Merge branch 'develop' into peerDAS

* `convertToAddrInfo`: Add peer details on error.

* `fetchOriginColumns`: Remove unused argument.

* `fetchOriginColumns`: Fix typo

* `isSidecarIndexRequested`: Log requested indices.

* `fetchOriginColumns`: Retry.

* Add changelog.

* Fix Preston comment.

* `custodyGroupCountFromPeerENR`: Add agent on error messages.

* Update beacon-chain/sync/initial-sync/service.go

Co-authored-by: Preston Van Loon <pvanloon@offchainlabs.com>

* Fix `TestCustodyGroupCountFromPeer`.

* `s.fetchOriginColumns`: Use `maxAttempts` and `delay` as parameters to ease unit testing.

* Implement `TestFetchOriginColumns`.

* `SendDataColumnSidecarsByRangeRequest` and `SendDataColumnSidecarsByRootRequest`: Add option to downscore the peer on RPC error.

* `fetchOriginColumns`: Remove max attempts, and downscore peers on RPC fault.

---------

Co-authored-by: Preston Van Loon <pvanloon@offchainlabs.com>

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -1,6 +1,6 @@
 name: 🐞 Bug report
 description: Report a bug or problem with running Prysm
-labels: ["Bug"]
+type: "Bug"
 body:
   - type: markdown
     attributes:

.github/workflows/check-specrefs.yml

@@ -0,0 +1,43 @@
+name: Check Spec References
+on: [push, pull_request]
+
+jobs:
+  check-specrefs:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v4
+
+    - name: Check version consistency
+      run: |
+        WORKSPACE_VERSION=$(grep 'consensus_spec_version = ' WORKSPACE | sed 's/.*"\(.*\)"/\1/')
+        ETHSPECIFY_VERSION=$(grep '^version:' specrefs/.ethspecify.yml | sed 's/version: //')
+        if [ "$WORKSPACE_VERSION" != "$ETHSPECIFY_VERSION" ]; then
+          echo "Version mismatch between WORKSPACE and ethspecify"
+          echo "  WORKSPACE: $WORKSPACE_VERSION"
+          echo "  specrefs/.ethspecify.yml: $ETHSPECIFY_VERSION"
+          exit 1
+        else
+          echo "Versions match: $WORKSPACE_VERSION"
+        fi
+
+    - name: Install ethspecify
+      run: python3 -mpip install ethspecify
+
+    - name: Update spec references
+      run: ethspecify process --path=specrefs
+
+    - name: Check for differences
+      run: |
+        if ! git diff --exit-code specrefs >/dev/null; then
+          echo "Spec references are out-of-date!"
+          echo ""
+          git --no-pager diff specrefs
+          exit 1
+        else
+          echo "Spec references are up-to-date!"
+        fi
+
+    - name: Check spec references
+      run: ethspecify check --path=specrefs

WORKSPACE

@@ -253,16 +253,16 @@ filegroup(
     url = "https://github.com/ethereum/EIPs/archive/5480440fe51742ed23342b68cf106cefd427e39d.tar.gz",
 )
 
-consensus_spec_version = "v1.6.0-alpha.1"
+consensus_spec_version = "v1.6.0-alpha.5"
 
 load("@prysm//tools:download_spectests.bzl", "consensus_spec_tests")
 
 consensus_spec_tests(
     name = "consensus_spec_tests",
     flavors = {
-        "general": "sha256-o4t9p3R+fQHF4KOykGmwlG3zDw5wUdVWprkzId8aIsk=",
-        "minimal": "sha256-sU7ToI8t3MR8x0vVjC8ERmAHZDWpEmnAC9FWIpHi5x4=",
-        "mainnet": "sha256-YKS4wngg0LgI9Upp4MYJ77aG+8+e/G4YeqEIlp06LZw=",
+        "general": "sha256-BXuEb1XbeSft0qzVFnoB8KC0YR1qM3ybT5lKUDbUWn8=",
+        "minimal": "sha256-EjwSHgBbWSoy5hm9V+A/bVMabyojaKsBNPrRtuPVq4k=",
+        "mainnet": "sha256-OGWMzarzaV1B9mVpy48/DCUbhjfX+b64pAxWwPLWhAs=",
     },
     version = consensus_spec_version,
 )
@@ -278,7 +278,7 @@ filegroup(
     visibility = ["//visibility:public"],
 )
     """,
-    integrity = "sha256-Nv4TEuEJPQIM4E6T9J0FOITsmappmXZjGtlhe1HEXnU=",
+    integrity = "sha256-FQWR5EZuVcQGR0ol9vpd7eunnfGexJ/7J3xycrFEJbU=",
     strip_prefix = "consensus-specs-" + consensus_spec_version[1:],
     url = "https://github.com/ethereum/consensus-specs/archive/refs/tags/%s.tar.gz" % consensus_spec_version,
 )

api/client/builder/client.go

@@ -102,6 +102,7 @@ type BuilderClient interface {
 	GetHeader(ctx context.Context, slot primitives.Slot, parentHash [32]byte, pubkey [48]byte) (SignedBid, error)
 	RegisterValidator(ctx context.Context, svr []*ethpb.SignedValidatorRegistrationV1) error
 	SubmitBlindedBlock(ctx context.Context, sb interfaces.ReadOnlySignedBeaconBlock) (interfaces.ExecutionData, v1.BlobsBundler, error)
+	SubmitBlindedBlockPostFulu(ctx context.Context, sb interfaces.ReadOnlySignedBeaconBlock) error
 	Status(ctx context.Context) error
 }
 
@@ -152,7 +153,8 @@ func (c *Client) NodeURL() string {
 type reqOption func(*http.Request)
 
 // do is a generic, opinionated request function to reduce boilerplate amongst the methods in this package api/client/builder.
-func (c *Client) do(ctx context.Context, method string, path string, body io.Reader, opts ...reqOption) (res []byte, header http.Header, err error) {
+// It validates that the HTTP response status matches the expectedStatus parameter.
+func (c *Client) do(ctx context.Context, method string, path string, body io.Reader, expectedStatus int, opts ...reqOption) (res []byte, header http.Header, err error) {
 	ctx, span := trace.StartSpan(ctx, "builder.client.do")
 	defer func() {
 		tracing.AnnotateError(span, err)
@@ -187,8 +189,8 @@ func (c *Client) do(ctx context.Context, method string, path string, body io.Rea
 			log.WithError(closeErr).Error("Failed to close response body")
 		}
 	}()
-	if r.StatusCode != http.StatusOK {
-		err = non200Err(r)
+	if r.StatusCode != expectedStatus {
+		err = unexpectedStatusErr(r, expectedStatus)
 		return
 	}
 	res, err = io.ReadAll(io.LimitReader(r.Body, client.MaxBodySize))
@@ -236,7 +238,7 @@ func (c *Client) GetHeader(ctx context.Context, slot primitives.Slot, parentHash
 			r.Header.Set("Accept", api.JsonMediaType)
 		}
 	}
-	data, header, err := c.do(ctx, http.MethodGet, path, nil, getOpts)
+	data, header, err := c.do(ctx, http.MethodGet, path, nil, http.StatusOK, getOpts)
 	if err != nil {
 		return nil, errors.Wrap(err, "error getting header from builder server")
 	}
@@ -409,7 +411,7 @@ func (c *Client) RegisterValidator(ctx context.Context, svr []*ethpb.SignedValid
 		}
 	}
 
-	if _, _, err = c.do(ctx, http.MethodPost, postRegisterValidatorPath, bytes.NewBuffer(body), postOpts); err != nil {
+	if _, _, err = c.do(ctx, http.MethodPost, postRegisterValidatorPath, bytes.NewBuffer(body), http.StatusOK, postOpts); err != nil {
 		return errors.Wrap(err, "do")
 	}
 	log.WithField("registrationCount", len(svr)).Debug("Successfully registered validator(s) on builder")
@@ -471,7 +473,7 @@ func (c *Client) SubmitBlindedBlock(ctx context.Context, sb interfaces.ReadOnlyS
 
 	// post the blinded block - the execution payload response should contain the unblinded payload, along with the
 	// blobs bundle if it is post deneb.
-	data, header, err := c.do(ctx, http.MethodPost, postBlindedBeaconBlockPath, bytes.NewBuffer(body), postOpts)
+	data, header, err := c.do(ctx, http.MethodPost, postBlindedBeaconBlockPath, bytes.NewBuffer(body), http.StatusOK, postOpts)
 	if err != nil {
 		return nil, nil, errors.Wrap(err, "error posting the blinded block to the builder api")
 	}
@@ -501,6 +503,24 @@ func (c *Client) SubmitBlindedBlock(ctx context.Context, sb interfaces.ReadOnlyS
 	return ed, blobs, nil
 }
 
+// SubmitBlindedBlockPostFulu calls the builder API endpoint post-Fulu where relays only return status codes.
+// This method is used after the Fulu fork when MEV-boost relays no longer return execution payloads.
+func (c *Client) SubmitBlindedBlockPostFulu(ctx context.Context, sb interfaces.ReadOnlySignedBeaconBlock) error {
+	body, postOpts, err := c.buildBlindedBlockRequest(sb)
+	if err != nil {
+		return err
+	}
+
+	// Post the blinded block - the response should only contain a status code (no payload)
+	_, _, err = c.do(ctx, http.MethodPost, postBlindedBeaconBlockPath, bytes.NewBuffer(body), http.StatusAccepted, postOpts)
+	if err != nil {
+		return errors.Wrap(err, "error posting the blinded block to the builder api post-Fulu")
+	}
+
+	// Success is indicated by no error (status 202)
+	return nil
+}
+
 func (c *Client) checkBlockVersion(respBytes []byte, header http.Header) (int, error) {
 	var versionHeader string
 	if c.sszEnabled {
@@ -657,11 +677,11 @@ func (c *Client) Status(ctx context.Context) error {
 	getOpts := func(r *http.Request) {
 		r.Header.Set("Accept", api.JsonMediaType)
 	}
-	_, _, err := c.do(ctx, http.MethodGet, getStatus, nil, getOpts)
+	_, _, err := c.do(ctx, http.MethodGet, getStatus, nil, http.StatusOK, getOpts)
 	return err
 }
 
-func non200Err(response *http.Response) error {
+func unexpectedStatusErr(response *http.Response, expected int) error {
 	bodyBytes, err := io.ReadAll(io.LimitReader(response.Body, client.MaxErrBodySize))
 	var errMessage ErrorMessage
 	var body string
@@ -670,7 +690,7 @@ func non200Err(response *http.Response) error {
 	} else {
 		body = "response body:\n" + string(bodyBytes)
 	}
-	msg := fmt.Sprintf("code=%d, url=%s, body=%s", response.StatusCode, response.Request.URL, body)
+	msg := fmt.Sprintf("expected=%d, got=%d, url=%s, body=%s", expected, response.StatusCode, response.Request.URL, body)
 	switch response.StatusCode {
 	case http.StatusUnsupportedMediaType:
 		log.WithError(ErrUnsupportedMediaType).Debug(msg)

api/client/builder/client_test.go

@@ -1555,6 +1555,89 @@ func testSignedBlindedBeaconBlockElectra(t *testing.T) *eth.SignedBlindedBeaconB
 	}
 }
 
+func TestSubmitBlindedBlockPostFulu(t *testing.T) {
+	ctx := t.Context()
+
+	t.Run("success", func(t *testing.T) {
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, postBlindedBeaconBlockPath, r.URL.Path)
+				require.Equal(t, "bellatrix", r.Header.Get("Eth-Consensus-Version"))
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Content-Type"))
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
+				// Post-Fulu: only return status code, no payload
+				return &http.Response{
+					StatusCode: http.StatusAccepted,
+					Body:       io.NopCloser(bytes.NewBufferString("")),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:      hc,
+			baseURL: &url.URL{Host: "localhost:3500", Scheme: "http"},
+		}
+		sbbb, err := blocks.NewSignedBeaconBlock(testSignedBlindedBeaconBlockBellatrix(t))
+		require.NoError(t, err)
+		err = c.SubmitBlindedBlockPostFulu(ctx, sbbb)
+		require.NoError(t, err)
+	})
+
+	t.Run("success_ssz", func(t *testing.T) {
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, postBlindedBeaconBlockPath, r.URL.Path)
+				require.Equal(t, "bellatrix", r.Header.Get(api.VersionHeader))
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Content-Type"))
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+				// Post-Fulu: only return status code, no payload
+				return &http.Response{
+					StatusCode: http.StatusAccepted,
+					Body:       io.NopCloser(bytes.NewBufferString("")),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:         hc,
+			baseURL:    &url.URL{Host: "localhost:3500", Scheme: "http"},
+			sszEnabled: true,
+		}
+		sbbb, err := blocks.NewSignedBeaconBlock(testSignedBlindedBeaconBlockBellatrix(t))
+		require.NoError(t, err)
+		err = c.SubmitBlindedBlockPostFulu(ctx, sbbb)
+		require.NoError(t, err)
+	})
+
+	t.Run("error_response", func(t *testing.T) {
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, postBlindedBeaconBlockPath, r.URL.Path)
+				require.Equal(t, "bellatrix", r.Header.Get("Eth-Consensus-Version"))
+				message := ErrorMessage{
+					Code:    400,
+					Message: "Bad Request",
+				}
+				resp, err := json.Marshal(message)
+				require.NoError(t, err)
+				return &http.Response{
+					StatusCode: http.StatusBadRequest,
+					Body:       io.NopCloser(bytes.NewBuffer(resp)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:      hc,
+			baseURL: &url.URL{Host: "localhost:3500", Scheme: "http"},
+		}
+		sbbb, err := blocks.NewSignedBeaconBlock(testSignedBlindedBeaconBlockBellatrix(t))
+		require.NoError(t, err)
+		err = c.SubmitBlindedBlockPostFulu(ctx, sbbb)
+		require.ErrorIs(t, err, ErrNotOK)
+	})
+}
+
 func TestRequestLogger(t *testing.T) {
 	wo := WithObserver(&requestLogger{})
 	c, err := NewClient("localhost:3500", wo)

api/client/builder/testing/mock.go

@@ -45,6 +45,11 @@ func (MockClient) SubmitBlindedBlock(_ context.Context, _ interfaces.ReadOnlySig
 	return nil, nil, nil
 }
 
+// SubmitBlindedBlockPostFulu --
+func (MockClient) SubmitBlindedBlockPostFulu(_ context.Context, _ interfaces.ReadOnlySignedBeaconBlock) error {
+	return nil
+}
+
 // Status --
 func (MockClient) Status(_ context.Context) error {
 	return nil

api/client/builder/types_test.go

@@ -1699,7 +1699,7 @@ func TestExecutionPayloadHeaderCapellaRoundtrip(t *testing.T) {
 	require.DeepEqual(t, string(expected[0:len(expected)-1]), string(m))
 }
 
-func TestErrorMessage_non200Err(t *testing.T) {
+func TestErrorMessage_unexpectedStatusErr(t *testing.T) {
 	mockRequest := &http.Request{
 		URL: &url.URL{Path: "example.com"},
 	}
@@ -1779,7 +1779,7 @@ func TestErrorMessage_non200Err(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			err := non200Err(tt.args)
+			err := unexpectedStatusErr(tt.args, http.StatusOK)
 			if err != nil && tt.wantMessage != "" {
 				require.ErrorContains(t, tt.wantMessage, err)
 			}

beacon-chain/blockchain/kzg/kzg.go

@@ -102,7 +102,6 @@ func VerifyCellKZGProofBatch(commitmentsBytes []Bytes48, cellIndices []uint64, c
 	for i := range cells {
 		ckzgCells[i] = ckzg4844.Cell(cells[i])
 	}
-
 	return ckzg4844.VerifyCellKZGProofBatch(commitmentsBytes, cellIndices, ckzgCells, proofsBytes)
 }
 

beacon-chain/blockchain/kzg/validation.go

@@ -1,32 +1,14 @@
 package kzg
 
 import (
+	"fmt"
+
 	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
 	GoKZG "github.com/crate-crypto/go-kzg-4844"
+	ckzg4844 "github.com/ethereum/c-kzg-4844/v2/bindings/go"
+	"github.com/pkg/errors"
 )
 
-// Verify performs single or batch verification of commitments depending on the number of given BlobSidecars.
-func Verify(sidecars ...blocks.ROBlob) error {
-	if len(sidecars) == 0 {
-		return nil
-	}
-	if len(sidecars) == 1 {
-		return kzgContext.VerifyBlobKZGProof(
-			bytesToBlob(sidecars[0].Blob),
-			bytesToCommitment(sidecars[0].KzgCommitment),
-			bytesToKZGProof(sidecars[0].KzgProof))
-	}
-	blobs := make([]GoKZG.Blob, len(sidecars))
-	cmts := make([]GoKZG.KZGCommitment, len(sidecars))
-	proofs := make([]GoKZG.KZGProof, len(sidecars))
-	for i, sidecar := range sidecars {
-		blobs[i] = *bytesToBlob(sidecar.Blob)
-		cmts[i] = bytesToCommitment(sidecar.KzgCommitment)
-		proofs[i] = bytesToKZGProof(sidecar.KzgProof)
-	}
-	return kzgContext.VerifyBlobKZGProofBatch(blobs, cmts, proofs)
-}
-
 func bytesToBlob(blob []byte) *GoKZG.Blob {
 	var ret GoKZG.Blob
 	copy(ret[:], blob)
@@ -42,3 +24,144 @@ func bytesToKZGProof(proof []byte) (ret GoKZG.KZGProof) {
 	copy(ret[:], proof)
 	return
 }
+
+// Verify performs single or batch verification of commitments depending on the number of given BlobSidecars.
+func Verify(blobSidecars ...blocks.ROBlob) error {
+	if len(blobSidecars) == 0 {
+		return nil
+	}
+	if len(blobSidecars) == 1 {
+		return kzgContext.VerifyBlobKZGProof(
+			bytesToBlob(blobSidecars[0].Blob),
+			bytesToCommitment(blobSidecars[0].KzgCommitment),
+			bytesToKZGProof(blobSidecars[0].KzgProof))
+	}
+	blobs := make([]GoKZG.Blob, len(blobSidecars))
+	cmts := make([]GoKZG.KZGCommitment, len(blobSidecars))
+	proofs := make([]GoKZG.KZGProof, len(blobSidecars))
+	for i, sidecar := range blobSidecars {
+		blobs[i] = *bytesToBlob(sidecar.Blob)
+		cmts[i] = bytesToCommitment(sidecar.KzgCommitment)
+		proofs[i] = bytesToKZGProof(sidecar.KzgProof)
+	}
+	return kzgContext.VerifyBlobKZGProofBatch(blobs, cmts, proofs)
+}
+
+// VerifyBlobKZGProofBatch verifies KZG proofs for multiple blobs using batch verification.
+// This is more efficient than verifying each blob individually when len(blobs) > 1.
+// For single blob verification, it uses the optimized single verification path.
+func VerifyBlobKZGProofBatch(blobs [][]byte, commitments [][]byte, proofs [][]byte) error {
+	if len(blobs) != len(commitments) || len(blobs) != len(proofs) {
+		return errors.Errorf("number of blobs (%d), commitments (%d), and proofs (%d) must match", len(blobs), len(commitments), len(proofs))
+	}
+
+	if len(blobs) == 0 {
+		return nil
+	}
+
+	// Optimize for single blob case - use single verification to avoid batch overhead
+	if len(blobs) == 1 {
+		return kzgContext.VerifyBlobKZGProof(
+			bytesToBlob(blobs[0]),
+			bytesToCommitment(commitments[0]),
+			bytesToKZGProof(proofs[0]))
+	}
+
+	// Use batch verification for multiple blobs
+	ckzgBlobs := make([]ckzg4844.Blob, len(blobs))
+	ckzgCommitments := make([]ckzg4844.Bytes48, len(commitments))
+	ckzgProofs := make([]ckzg4844.Bytes48, len(proofs))
+
+	for i := range blobs {
+		if len(blobs[i]) != len(ckzg4844.Blob{}) {
+			return fmt.Errorf("blobs len (%d) differs from expected (%d)", len(blobs[i]), len(ckzg4844.Blob{}))
+		}
+		if len(commitments[i]) != len(ckzg4844.Bytes48{}) {
+			return fmt.Errorf("commitments len (%d) differs from expected (%d)", len(commitments[i]), len(ckzg4844.Blob{}))
+		}
+		if len(proofs[i]) != len(ckzg4844.Bytes48{}) {
+			return fmt.Errorf("proofs len (%d) differs from expected (%d)", len(proofs[i]), len(ckzg4844.Blob{}))
+		}
+		ckzgBlobs[i] = ckzg4844.Blob(blobs[i])
+		ckzgCommitments[i] = ckzg4844.Bytes48(commitments[i])
+		ckzgProofs[i] = ckzg4844.Bytes48(proofs[i])
+	}
+
+	valid, err := ckzg4844.VerifyBlobKZGProofBatch(ckzgBlobs, ckzgCommitments, ckzgProofs)
+	if err != nil {
+		return errors.Wrap(err, "batch verification")
+	}
+	if !valid {
+		return errors.New("batch KZG proof verification failed")
+	}
+
+	return nil
+}
+
+// VerifyCellKZGProofBatchFromBlobData verifies cell KZG proofs in batch format directly from blob data.
+// This is more efficient than reconstructing data column sidecars when you have the raw blob data and cell proofs.
+// For PeerDAS/Fulu, the execution client provides cell proofs in flattened format via BlobsBundleV2.
+// For single blob verification, it optimizes by computing cells once and verifying efficiently.
+func VerifyCellKZGProofBatchFromBlobData(blobs [][]byte, commitments [][]byte, cellProofs [][]byte, numberOfColumns uint64) error {
+	blobCount := uint64(len(blobs))
+	expectedCellProofs := blobCount * numberOfColumns
+
+	if uint64(len(cellProofs)) != expectedCellProofs {
+		return errors.Errorf("expected %d cell proofs, got %d", expectedCellProofs, len(cellProofs))
+	}
+
+	if len(commitments) != len(blobs) {
+		return errors.Errorf("number of commitments (%d) must match number of blobs (%d)", len(commitments), len(blobs))
+	}
+
+	if blobCount == 0 {
+		return nil
+	}
+
+	// Handle multiple blobs - compute cells for all blobs
+	allCells := make([]Cell, 0, expectedCellProofs)
+	allCommitments := make([]Bytes48, 0, expectedCellProofs)
+	allIndices := make([]uint64, 0, expectedCellProofs)
+	allProofs := make([]Bytes48, 0, expectedCellProofs)
+
+	for blobIndex := range blobs {
+		if len(blobs[blobIndex]) != len(Blob{}) {
+			return fmt.Errorf("blobs len (%d) differs from expected (%d)", len(blobs[blobIndex]), len(Blob{}))
+		}
+		// Convert blob to kzg.Blob type
+		blob := Blob(blobs[blobIndex])
+
+		// Compute cells for this blob
+		cells, err := ComputeCells(&blob)
+		if err != nil {
+			return errors.Wrapf(err, "failed to compute cells for blob %d", blobIndex)
+		}
+
+		// Add cells and corresponding data for each column
+		for columnIndex := range numberOfColumns {
+			cellProofIndex := uint64(blobIndex)*numberOfColumns + columnIndex
+			if len(commitments[blobIndex]) != len(Bytes48{}) {
+				return fmt.Errorf("commitments len (%d) differs from expected (%d)", len(commitments[blobIndex]), len(Bytes48{}))
+			}
+			if len(cellProofs[cellProofIndex]) != len(Bytes48{}) {
+				return fmt.Errorf("proofs len (%d) differs from expected (%d)", len(cellProofs[cellProofIndex]), len(Bytes48{}))
+			}
+			allCells = append(allCells, cells[columnIndex])
+			allCommitments = append(allCommitments, Bytes48(commitments[blobIndex]))
+			allIndices = append(allIndices, columnIndex)
+
+			allProofs = append(allProofs, Bytes48(cellProofs[cellProofIndex]))
+		}
+	}
+
+	// Batch verify all cells
+	valid, err := VerifyCellKZGProofBatch(allCommitments, allIndices, allCells, allProofs)
+	if err != nil {
+		return errors.Wrap(err, "cell batch verification")
+	}
+	if !valid {
+		return errors.New("cell KZG proof batch verification failed")
+	}
+
+	return nil
+}

beacon-chain/blockchain/kzg/validation_test.go

@@ -22,8 +22,8 @@ func GenerateCommitmentAndProof(blob GoKZG.Blob) (GoKZG.KZGCommitment, GoKZG.KZG
 }
 
 func TestVerify(t *testing.T) {
-	sidecars := make([]blocks.ROBlob, 0)
-	require.NoError(t, Verify(sidecars...))
+	blobSidecars := make([]blocks.ROBlob, 0)
+	require.NoError(t, Verify(blobSidecars...))
 }
 
 func TestBytesToAny(t *testing.T) {
@@ -37,6 +37,7 @@ func TestBytesToAny(t *testing.T) {
 }
 
 func TestGenerateCommitmentAndProof(t *testing.T) {
+	require.NoError(t, Start())
 	blob := random.GetRandBlob(123)
 	commitment, proof, err := GenerateCommitmentAndProof(blob)
 	require.NoError(t, err)
@@ -45,3 +46,432 @@ func TestGenerateCommitmentAndProof(t *testing.T) {
 	require.Equal(t, expectedCommitment, commitment)
 	require.Equal(t, expectedProof, proof)
 }
+
+func TestVerifyBlobKZGProofBatch(t *testing.T) {
+	// Initialize KZG for testing
+	require.NoError(t, Start())
+
+	t.Run("valid single blob batch", func(t *testing.T) {
+		blob := random.GetRandBlob(123)
+		commitment, proof, err := GenerateCommitmentAndProof(blob)
+		require.NoError(t, err)
+
+		blobs := [][]byte{blob[:]}
+		commitments := [][]byte{commitment[:]}
+		proofs := [][]byte{proof[:]}
+
+		err = VerifyBlobKZGProofBatch(blobs, commitments, proofs)
+		require.NoError(t, err)
+	})
+
+	t.Run("valid multiple blob batch", func(t *testing.T) {
+		blobCount := 3
+		blobs := make([][]byte, blobCount)
+		commitments := make([][]byte, blobCount)
+		proofs := make([][]byte, blobCount)
+
+		for i := 0; i < blobCount; i++ {
+			blob := random.GetRandBlob(int64(i))
+			commitment, proof, err := GenerateCommitmentAndProof(blob)
+			require.NoError(t, err)
+
+			blobs[i] = blob[:]
+			commitments[i] = commitment[:]
+			proofs[i] = proof[:]
+		}
+
+		err := VerifyBlobKZGProofBatch(blobs, commitments, proofs)
+		require.NoError(t, err)
+	})
+
+	t.Run("empty inputs should pass", func(t *testing.T) {
+		err := VerifyBlobKZGProofBatch([][]byte{}, [][]byte{}, [][]byte{})
+		require.NoError(t, err)
+	})
+
+	t.Run("mismatched input lengths", func(t *testing.T) {
+		blob := random.GetRandBlob(123)
+		commitment, proof, err := GenerateCommitmentAndProof(blob)
+		require.NoError(t, err)
+
+		// Test different mismatch scenarios
+		err = VerifyBlobKZGProofBatch(
+			[][]byte{blob[:]},
+			[][]byte{},
+			[][]byte{proof[:]},
+		)
+		require.ErrorContains(t, "number of blobs (1), commitments (0), and proofs (1) must match", err)
+
+		err = VerifyBlobKZGProofBatch(
+			[][]byte{blob[:], blob[:]},
+			[][]byte{commitment[:]},
+			[][]byte{proof[:], proof[:]},
+		)
+		require.ErrorContains(t, "number of blobs (2), commitments (1), and proofs (2) must match", err)
+	})
+
+	t.Run("invalid commitment should fail", func(t *testing.T) {
+		blob := random.GetRandBlob(123)
+		_, proof, err := GenerateCommitmentAndProof(blob)
+		require.NoError(t, err)
+
+		// Use a different blob's commitment (mismatch)
+		differentBlob := random.GetRandBlob(456)
+		wrongCommitment, _, err := GenerateCommitmentAndProof(differentBlob)
+		require.NoError(t, err)
+
+		blobs := [][]byte{blob[:]}
+		commitments := [][]byte{wrongCommitment[:]}
+		proofs := [][]byte{proof[:]}
+
+		err = VerifyBlobKZGProofBatch(blobs, commitments, proofs)
+		// Single blob optimization uses different error message
+		require.ErrorContains(t, "can't verify opening proof", err)
+	})
+
+	t.Run("invalid proof should fail", func(t *testing.T) {
+		blob := random.GetRandBlob(123)
+		commitment, _, err := GenerateCommitmentAndProof(blob)
+		require.NoError(t, err)
+
+		// Use wrong proof
+		invalidProof := make([]byte, 48) // All zeros
+
+		blobs := [][]byte{blob[:]}
+		commitments := [][]byte{commitment[:]}
+		proofs := [][]byte{invalidProof}
+
+		err = VerifyBlobKZGProofBatch(blobs, commitments, proofs)
+		require.ErrorContains(t, "short buffer", err)
+	})
+
+	t.Run("mixed valid and invalid proofs should fail", func(t *testing.T) {
+		// First blob - valid
+		blob1 := random.GetRandBlob(123)
+		commitment1, proof1, err := GenerateCommitmentAndProof(blob1)
+		require.NoError(t, err)
+
+		// Second blob - invalid proof
+		blob2 := random.GetRandBlob(456)
+		commitment2, _, err := GenerateCommitmentAndProof(blob2)
+		require.NoError(t, err)
+		invalidProof := make([]byte, 48) // All zeros
+
+		blobs := [][]byte{blob1[:], blob2[:]}
+		commitments := [][]byte{commitment1[:], commitment2[:]}
+		proofs := [][]byte{proof1[:], invalidProof}
+
+		err = VerifyBlobKZGProofBatch(blobs, commitments, proofs)
+		require.ErrorContains(t, "batch verification", err)
+	})
+
+	t.Run("batch KZG proof verification failed", func(t *testing.T) {
+		// Create multiple blobs with mismatched commitments and proofs to trigger batch verification failure
+		blob1 := random.GetRandBlob(123)
+		blob2 := random.GetRandBlob(456)
+
+		// Generate valid proof for blob1
+		commitment1, proof1, err := GenerateCommitmentAndProof(blob1)
+		require.NoError(t, err)
+
+		// Generate valid proof for blob2 but use wrong commitment (from blob1)
+		_, proof2, err := GenerateCommitmentAndProof(blob2)
+		require.NoError(t, err)
+
+		// Use blob2 data with blob1's commitment and blob2's proof - this should cause batch verification to fail
+		blobs := [][]byte{blob1[:], blob2[:]}
+		commitments := [][]byte{commitment1[:], commitment1[:]} // Wrong commitment for blob2
+		proofs := [][]byte{proof1[:], proof2[:]}
+
+		err = VerifyBlobKZGProofBatch(blobs, commitments, proofs)
+		require.ErrorContains(t, "batch KZG proof verification failed", err)
+	})
+}
+
+func TestVerifyCellKZGProofBatchFromBlobData(t *testing.T) {
+	// Initialize KZG for testing
+	require.NoError(t, Start())
+
+	t.Run("valid single blob cell verification", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+
+		// Generate blob and commitment
+		randBlob := random.GetRandBlob(123)
+		var blob Blob
+		copy(blob[:], randBlob[:])
+		commitment, err := BlobToKZGCommitment(&blob)
+		require.NoError(t, err)
+
+		// Compute cells and proofs
+		cellsAndProofs, err := ComputeCellsAndKZGProofs(&blob)
+		require.NoError(t, err)
+
+		// Create flattened cell proofs (like execution client format)
+		cellProofs := make([][]byte, numberOfColumns)
+		for i := range numberOfColumns {
+			cellProofs[i] = cellsAndProofs.Proofs[i][:]
+		}
+
+		blobs := [][]byte{blob[:]}
+		commitments := [][]byte{commitment[:]}
+
+		err = VerifyCellKZGProofBatchFromBlobData(blobs, commitments, cellProofs, numberOfColumns)
+		require.NoError(t, err)
+	})
+
+	t.Run("valid multiple blob cell verification", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+		blobCount := 2
+
+		blobs := make([][]byte, blobCount)
+		commitments := make([][]byte, blobCount)
+		var allCellProofs [][]byte
+
+		for i := range blobCount {
+			// Generate blob and commitment
+			randBlob := random.GetRandBlob(int64(i))
+			var blob Blob
+			copy(blob[:], randBlob[:])
+			commitment, err := BlobToKZGCommitment(&blob)
+			require.NoError(t, err)
+
+			// Compute cells and proofs
+			cellsAndProofs, err := ComputeCellsAndKZGProofs(&blob)
+			require.NoError(t, err)
+
+			blobs[i] = blob[:]
+			commitments[i] = commitment[:]
+
+			// Add cell proofs for this blob
+			for j := range numberOfColumns {
+				allCellProofs = append(allCellProofs, cellsAndProofs.Proofs[j][:])
+			}
+		}
+
+		err := VerifyCellKZGProofBatchFromBlobData(blobs, commitments, allCellProofs, numberOfColumns)
+		require.NoError(t, err)
+	})
+
+	t.Run("empty inputs should pass", func(t *testing.T) {
+		err := VerifyCellKZGProofBatchFromBlobData([][]byte{}, [][]byte{}, [][]byte{}, 128)
+		require.NoError(t, err)
+	})
+
+	t.Run("mismatched blob and commitment count", func(t *testing.T) {
+		randBlob := random.GetRandBlob(123)
+		var blob Blob
+		copy(blob[:], randBlob[:])
+
+		err := VerifyCellKZGProofBatchFromBlobData(
+			[][]byte{blob[:]},
+			[][]byte{}, // Empty commitments
+			[][]byte{},
+			128,
+		)
+		require.ErrorContains(t, "expected 128 cell proofs", err)
+	})
+
+	t.Run("wrong cell proof count", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+
+		randBlob := random.GetRandBlob(123)
+		var blob Blob
+		copy(blob[:], randBlob[:])
+		commitment, err := BlobToKZGCommitment(&blob)
+		require.NoError(t, err)
+
+		blobs := [][]byte{blob[:]}
+		commitments := [][]byte{commitment[:]}
+
+		// Wrong number of cell proofs - should be 128 for 1 blob, but provide 10
+		wrongCellProofs := make([][]byte, 10)
+
+		err = VerifyCellKZGProofBatchFromBlobData(blobs, commitments, wrongCellProofs, numberOfColumns)
+		require.ErrorContains(t, "expected 128 cell proofs, got 10", err)
+	})
+
+	t.Run("invalid cell proofs should fail", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+
+		randBlob := random.GetRandBlob(123)
+		var blob Blob
+		copy(blob[:], randBlob[:])
+		commitment, err := BlobToKZGCommitment(&blob)
+		require.NoError(t, err)
+
+		blobs := [][]byte{blob[:]}
+		commitments := [][]byte{commitment[:]}
+
+		// Create invalid cell proofs (all zeros)
+		invalidCellProofs := make([][]byte, numberOfColumns)
+		for i := range numberOfColumns {
+			invalidCellProofs[i] = make([]byte, 48) // All zeros
+		}
+
+		err = VerifyCellKZGProofBatchFromBlobData(blobs, commitments, invalidCellProofs, numberOfColumns)
+		require.ErrorContains(t, "cell batch verification", err)
+	})
+
+	t.Run("mismatched commitment should fail", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+
+		// Generate blob and correct cell proofs
+		randBlob := random.GetRandBlob(123)
+		var blob Blob
+		copy(blob[:], randBlob[:])
+		cellsAndProofs, err := ComputeCellsAndKZGProofs(&blob)
+		require.NoError(t, err)
+
+		// Generate wrong commitment from different blob
+		randBlob2 := random.GetRandBlob(456)
+		var differentBlob Blob
+		copy(differentBlob[:], randBlob2[:])
+		wrongCommitment, err := BlobToKZGCommitment(&differentBlob)
+		require.NoError(t, err)
+
+		cellProofs := make([][]byte, numberOfColumns)
+		for i := range numberOfColumns {
+			cellProofs[i] = cellsAndProofs.Proofs[i][:]
+		}
+
+		blobs := [][]byte{blob[:]}
+		commitments := [][]byte{wrongCommitment[:]}
+
+		err = VerifyCellKZGProofBatchFromBlobData(blobs, commitments, cellProofs, numberOfColumns)
+		require.ErrorContains(t, "cell KZG proof batch verification failed", err)
+	})
+
+	t.Run("invalid blob data that should cause ComputeCells to fail", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+
+		// Create invalid blob (not properly formatted)
+		invalidBlobData := make([]byte, 10) // Too short
+		commitment := make([]byte, 48)      // Dummy commitment
+		cellProofs := make([][]byte, numberOfColumns)
+		for i := range numberOfColumns {
+			cellProofs[i] = make([]byte, 48)
+		}
+
+		blobs := [][]byte{invalidBlobData}
+		commitments := [][]byte{commitment}
+
+		err := VerifyCellKZGProofBatchFromBlobData(blobs, commitments, cellProofs, numberOfColumns)
+		require.NotNil(t, err)
+		require.ErrorContains(t, "blobs len (10) differs from expected (131072)", err)
+	})
+
+	t.Run("invalid commitment size should fail", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+
+		randBlob := random.GetRandBlob(123)
+		var blob Blob
+		copy(blob[:], randBlob[:])
+		
+		// Create invalid commitment (wrong size)
+		invalidCommitment := make([]byte, 32) // Should be 48 bytes
+		cellProofs := make([][]byte, numberOfColumns)
+		for i := range numberOfColumns {
+			cellProofs[i] = make([]byte, 48)
+		}
+
+		blobs := [][]byte{blob[:]}
+		commitments := [][]byte{invalidCommitment}
+
+		err := VerifyCellKZGProofBatchFromBlobData(blobs, commitments, cellProofs, numberOfColumns)
+		require.ErrorContains(t, "commitments len (32) differs from expected (48)", err)
+	})
+
+	t.Run("invalid cell proof size should fail", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+
+		randBlob := random.GetRandBlob(123)
+		var blob Blob
+		copy(blob[:], randBlob[:])
+		commitment, err := BlobToKZGCommitment(&blob)
+		require.NoError(t, err)
+
+		// Create invalid cell proofs (wrong size)
+		invalidCellProofs := make([][]byte, numberOfColumns)
+		for i := range numberOfColumns {
+			if i == 0 {
+				invalidCellProofs[i] = make([]byte, 32) // Wrong size - should be 48
+			} else {
+				invalidCellProofs[i] = make([]byte, 48)
+			}
+		}
+
+		blobs := [][]byte{blob[:]}
+		commitments := [][]byte{commitment[:]}
+
+		err = VerifyCellKZGProofBatchFromBlobData(blobs, commitments, invalidCellProofs, numberOfColumns)
+		require.ErrorContains(t, "proofs len (32) differs from expected (48)", err)
+	})
+
+	t.Run("multiple blobs with mixed invalid commitments", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+		blobCount := 2
+
+		blobs := make([][]byte, blobCount)
+		commitments := make([][]byte, blobCount)
+		var allCellProofs [][]byte
+
+		// First blob - valid
+		randBlob1 := random.GetRandBlob(123)
+		var blob1 Blob
+		copy(blob1[:], randBlob1[:])
+		commitment1, err := BlobToKZGCommitment(&blob1)
+		require.NoError(t, err)
+		blobs[0] = blob1[:]
+		commitments[0] = commitment1[:]
+
+		// Second blob - use invalid commitment size
+		randBlob2 := random.GetRandBlob(456)
+		var blob2 Blob
+		copy(blob2[:], randBlob2[:])
+		blobs[1] = blob2[:]
+		commitments[1] = make([]byte, 32) // Wrong size
+
+		// Add cell proofs for both blobs
+		for i := 0; i < blobCount; i++ {
+			for j := uint64(0); j < numberOfColumns; j++ {
+				allCellProofs = append(allCellProofs, make([]byte, 48))
+			}
+		}
+
+		err = VerifyCellKZGProofBatchFromBlobData(blobs, commitments, allCellProofs, numberOfColumns)
+		require.ErrorContains(t, "commitments len (32) differs from expected (48)", err)
+	})
+
+	t.Run("multiple blobs with mixed invalid cell proof sizes", func(t *testing.T) {
+		numberOfColumns := uint64(128)
+		blobCount := 2
+
+		blobs := make([][]byte, blobCount)
+		commitments := make([][]byte, blobCount)
+		var allCellProofs [][]byte
+
+		for i := 0; i < blobCount; i++ {
+			randBlob := random.GetRandBlob(int64(i))
+			var blob Blob
+			copy(blob[:], randBlob[:])
+			commitment, err := BlobToKZGCommitment(&blob)
+			require.NoError(t, err)
+			
+			blobs[i] = blob[:]
+			commitments[i] = commitment[:]
+			
+			// Add cell proofs - make some invalid in the second blob
+			for j := uint64(0); j < numberOfColumns; j++ {
+				if i == 1 && j == 64 {
+					// Invalid proof size in middle of second blob's proofs
+					allCellProofs = append(allCellProofs, make([]byte, 20))
+				} else {
+					allCellProofs = append(allCellProofs, make([]byte, 48))
+				}
+			}
+		}
+
+		err := VerifyCellKZGProofBatchFromBlobData(blobs, commitments, allCellProofs, numberOfColumns)
+		require.ErrorContains(t, "proofs len (20) differs from expected (48)", err)
+	})
+}

beacon-chain/blockchain/process_block.go

@@ -159,7 +159,7 @@ func (s *Service) onBlockBatch(ctx context.Context, blks []consensusblocks.ROBlo
 	}
 
 	// Fill in missing blocks
-	if err := s.fillInForkChoiceMissingBlocks(ctx, blks[0], preState.CurrentJustifiedCheckpoint(), preState.FinalizedCheckpoint()); err != nil {
+	if err := s.fillInForkChoiceMissingBlocks(ctx, blks[0], preState.FinalizedCheckpoint(), preState.CurrentJustifiedCheckpoint()); err != nil {
 		return errors.Wrap(err, "could not fill in missing blocks to forkchoice")
 	}
 
@@ -240,9 +240,10 @@ func (s *Service) onBlockBatch(ctx context.Context, blks []consensusblocks.ROBlo
 			}
 		}
 
-		if err := avs.IsDataAvailable(ctx, s.CurrentSlot(), b); err != nil {
-			return errors.Wrapf(err, "could not validate sidecar availability at slot %d", b.Block().Slot())
+		if err := s.areSidecarsAvailable(ctx, avs, b); err != nil {
+			return errors.Wrapf(err, "could not validate sidecar availability for block %#x at slot %d", b.Root(), b.Block().Slot())
 		}
+
 		args := &forkchoicetypes.BlockAndCheckpoints{Block: b,
 			JustifiedCheckpoint: jCheckpoints[i],
 			FinalizedCheckpoint: fCheckpoints[i]}
@@ -308,6 +309,30 @@ func (s *Service) onBlockBatch(ctx context.Context, blks []consensusblocks.ROBlo
 	return s.saveHeadNoDB(ctx, lastB, lastBR, preState, !isValidPayload)
 }
 
+func (s *Service) areSidecarsAvailable(ctx context.Context, avs das.AvailabilityStore, roBlock consensusblocks.ROBlock) error {
+	blockVersion := roBlock.Version()
+	block := roBlock.Block()
+	slot := block.Slot()
+
+	if blockVersion >= version.Fulu {
+		if err := s.areDataColumnsAvailable(ctx, roBlock.Root(), block); err != nil {
+			return errors.Wrapf(err, "are data columns available for block %#x with slot %d", roBlock.Root(), slot)
+		}
+
+		return nil
+	}
+
+	if blockVersion >= version.Deneb {
+		if err := avs.IsDataAvailable(ctx, s.CurrentSlot(), roBlock); err != nil {
+			return errors.Wrapf(err, "could not validate sidecar availability at slot %d", slot)
+		}
+
+		return nil
+	}
+
+	return nil
+}
+
 func (s *Service) updateEpochBoundaryCaches(ctx context.Context, st state.BeaconState) error {
 	e := coreTime.CurrentEpoch(st)
 	if err := helpers.UpdateCommitteeCache(ctx, st, e); err != nil {
@@ -584,7 +609,7 @@ func (s *Service) runLateBlockTasks() {
 // It returns a map where each key represents a missing BlobSidecar index.
 // An empty map means we have all indices; a non-empty map can be used to compare incoming
 // BlobSidecars against the set of known missing sidecars.
-func missingBlobIndices(bs *filesystem.BlobStorage, root [fieldparams.RootLength]byte, expected [][]byte, slot primitives.Slot) (map[uint64]bool, error) {
+func missingBlobIndices(store *filesystem.BlobStorage, root [fieldparams.RootLength]byte, expected [][]byte, slot primitives.Slot) (map[uint64]bool, error) {
 	maxBlobsPerBlock := params.BeaconConfig().MaxBlobsPerBlock(slot)
 	if len(expected) == 0 {
 		return nil, nil
@@ -592,7 +617,7 @@ func missingBlobIndices(bs *filesystem.BlobStorage, root [fieldparams.RootLength
 	if len(expected) > maxBlobsPerBlock {
 		return nil, errMaxBlobsExceeded
 	}
-	indices := bs.Summary(root)
+	indices := store.Summary(root)
 	missing := make(map[uint64]bool, len(expected))
 	for i := range expected {
 		if len(expected[i]) > 0 && !indices.HasIndex(uint64(i)) {
@@ -607,7 +632,7 @@ func missingBlobIndices(bs *filesystem.BlobStorage, root [fieldparams.RootLength
 // It returns a map where each key represents a missing DataColumnSidecar index.
 // An empty map means we have all indices; a non-empty map can be used to compare incoming
 // DataColumns against the set of known missing sidecars.
-func missingDataColumnIndices(bs *filesystem.DataColumnStorage, root [fieldparams.RootLength]byte, expected map[uint64]bool) (map[uint64]bool, error) {
+func missingDataColumnIndices(store *filesystem.DataColumnStorage, root [fieldparams.RootLength]byte, expected map[uint64]bool) (map[uint64]bool, error) {
 	if len(expected) == 0 {
 		return nil, nil
 	}
@@ -619,7 +644,7 @@ func missingDataColumnIndices(bs *filesystem.DataColumnStorage, root [fieldparam
 	}
 
 	// Get a summary of the data columns stored in the database.
-	summary := bs.Summary(root)
+	summary := store.Summary(root)
 
 	// Check all expected data columns against the summary.
 	missing := make(map[uint64]bool)
@@ -717,7 +742,7 @@ func (s *Service) areDataColumnsAvailable(
 	summary := s.dataColumnStorage.Summary(root)
 	storedDataColumnsCount := summary.Count()
 
-	minimumColumnCountToReconstruct := peerdas.MinimumColumnsCountToReconstruct()
+	minimumColumnCountToReconstruct := peerdas.MinimumColumnCountToReconstruct()
 
 	// As soon as we have enough data column sidecars, we can reconstruct the missing ones.
 	// We don't need to wait for the rest of the data columns to declare the block as available.
@@ -820,7 +845,7 @@ func (s *Service) areDataColumnsAvailable(
 				missingIndices = uint64MapToSortedSlice(missingMap)
 			}
 
-			return errors.Wrapf(ctx.Err(), "data column sidecars slot: %d, BlockRoot: %#x, missing %v", block.Slot(), root, missingIndices)
+			return errors.Wrapf(ctx.Err(), "data column sidecars slot: %d, BlockRoot: %#x, missing: %v", block.Slot(), root, missingIndices)
 		}
 	}
 }

beacon-chain/blockchain/process_block_helpers.go

@@ -30,6 +30,10 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+// ErrInvalidCheckpointArgs may be returned when the finalized checkpoint has an epoch greater than the justified checkpoint epoch.
+// If you are seeing this error, make sure you haven't mixed up the order of the arguments in the method you are calling.
+var ErrInvalidCheckpointArgs = errors.New("finalized checkpoint cannot be greater than justified checkpoint")
+
 // CurrentSlot returns the current slot based on time.
 func (s *Service) CurrentSlot() primitives.Slot {
 	return slots.CurrentSlot(s.genesisTime)
@@ -454,6 +458,9 @@ func (s *Service) ancestorByDB(ctx context.Context, r [32]byte, slot primitives.
 // This is useful for block tree visualizer and additional vote accounting.
 func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, signed interfaces.ReadOnlySignedBeaconBlock,
 	fCheckpoint, jCheckpoint *ethpb.Checkpoint) error {
+	if fCheckpoint.Epoch > jCheckpoint.Epoch {
+		return ErrInvalidCheckpointArgs
+	}
 	pendingNodes := make([]*forkchoicetypes.BlockAndCheckpoints, 0)
 
 	// Fork choice only matters from last finalized slot.

beacon-chain/blockchain/process_block_test.go

@@ -375,6 +375,81 @@ func TestFillForkChoiceMissingBlocks_FinalizedSibling(t *testing.T) {
 	require.Equal(t, ErrNotDescendantOfFinalized.Error(), err.Error())
 }
 
+func TestFillForkChoiceMissingBlocks_ErrorCases(t *testing.T) {
+	tests := []struct {
+		name           string
+		finalizedEpoch primitives.Epoch
+		justifiedEpoch primitives.Epoch
+		expectedError  error
+	}{
+		{
+			name:           "finalized epoch greater than justified epoch",
+			finalizedEpoch: 5,
+			justifiedEpoch: 3,
+			expectedError:  ErrInvalidCheckpointArgs,
+		},
+		{
+			name:           "valid case - finalized equal to justified",
+			finalizedEpoch: 3,
+			justifiedEpoch: 3,
+			expectedError:  nil,
+		},
+		{
+			name:           "valid case - finalized less than justified",
+			finalizedEpoch: 2,
+			justifiedEpoch: 3,
+			expectedError:  nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			service, tr := minimalTestService(t)
+			ctx, beaconDB := tr.ctx, tr.db
+
+			st, _ := util.DeterministicGenesisState(t, 64)
+			require.NoError(t, service.saveGenesisData(ctx, st))
+
+			// Create a simple block for testing
+			blk := util.NewBeaconBlock()
+			blk.Block.Slot = 10
+			blk.Block.ParentRoot = service.originBlockRoot[:]
+			wsb, err := consensusblocks.NewSignedBeaconBlock(blk)
+			require.NoError(t, err)
+			util.SaveBlock(t, ctx, beaconDB, blk)
+
+			// Create checkpoints with test case epochs
+			finalizedCheckpoint := &ethpb.Checkpoint{
+				Epoch: tt.finalizedEpoch,
+				Root:  service.originBlockRoot[:],
+			}
+			justifiedCheckpoint := &ethpb.Checkpoint{
+				Epoch: tt.justifiedEpoch,
+				Root:  service.originBlockRoot[:],
+			}
+
+			// Set up forkchoice store to avoid other errors
+			fcp := &ethpb.Checkpoint{Epoch: 0, Root: service.originBlockRoot[:]}
+			state, blkRoot, err := prepareForkchoiceState(ctx, 0, service.originBlockRoot, service.originBlockRoot, [32]byte{}, fcp, fcp)
+			require.NoError(t, err)
+			require.NoError(t, service.cfg.ForkChoiceStore.InsertNode(ctx, state, blkRoot))
+
+			err = service.fillInForkChoiceMissingBlocks(
+				t.Context(), wsb, finalizedCheckpoint, justifiedCheckpoint)
+
+			if tt.expectedError != nil {
+				require.ErrorIs(t, err, tt.expectedError)
+			} else {
+				// For valid cases, we might get other errors (like block not being descendant of finalized)
+				// but we shouldn't get the checkpoint validation error
+				if err != nil && errors.Is(err, tt.expectedError) {
+					t.Errorf("Unexpected checkpoint validation error: %v", err)
+				}
+			}
+		})
+	}
+}
+
 // blockTree1 constructs the following tree:
 //
 //	/- B1
@@ -2132,13 +2207,13 @@ func TestNoViableHead_Reboot(t *testing.T) {
 
 	// Forkchoice has the genesisRoot loaded at startup
 	require.Equal(t, genesisRoot, service.ensureRootNotZeros(service.cfg.ForkChoiceStore.CachedHeadRoot()))
-	// Service's store has the finalized state as headRoot
+	// Service's store has the justified checkpoint root as headRoot (verified below through justified checkpoint comparison)
 	headRoot, err := service.HeadRoot(ctx)
 	require.NoError(t, err)
-	require.Equal(t, genesisRoot, bytesutil.ToBytes32(headRoot))
+	require.NotEqual(t, bytesutil.ToBytes32(params.BeaconConfig().ZeroHash[:]), bytesutil.ToBytes32(headRoot)) // Ensure head is not zero
 	optimistic, err := service.IsOptimistic(ctx)
 	require.NoError(t, err)
-	require.Equal(t, false, optimistic)
+	require.Equal(t, true, optimistic) // Head is now optimistic when starting from justified checkpoint
 
 	// Check that the node's justified checkpoint does not agree with the
 	// last valid state's justified checkpoint
@@ -2889,7 +2964,7 @@ func TestIsDataAvailable(t *testing.T) {
 	})
 
 	t.Run("Fulu - more than half of the columns in custody", func(t *testing.T) {
-		minimumColumnsCountToReconstruct := peerdas.MinimumColumnsCountToReconstruct()
+		minimumColumnsCountToReconstruct := peerdas.MinimumColumnCountToReconstruct()
 		indices := make([]uint64, 0, minimumColumnsCountToReconstruct)
 		for i := range minimumColumnsCountToReconstruct {
 			indices = append(indices, i)
@@ -2974,7 +3049,7 @@ func TestIsDataAvailable(t *testing.T) {
 
 		startWaiting := make(chan bool)
 
-		minimumColumnsCountToReconstruct := peerdas.MinimumColumnsCountToReconstruct()
+		minimumColumnsCountToReconstruct := peerdas.MinimumColumnCountToReconstruct()
 		indices := make([]uint64, 0, minimumColumnsCountToReconstruct-missingColumns)
 
 		for i := range minimumColumnsCountToReconstruct - missingColumns {

beacon-chain/blockchain/receive_data_column.go

@@ -17,7 +17,7 @@ func (s *Service) ReceiveDataColumns(dataColumnSidecars []blocks.VerifiedRODataC
 // ReceiveDataColumn receives a single data column.
 func (s *Service) ReceiveDataColumn(dataColumnSidecar blocks.VerifiedRODataColumn) error {
 	if err := s.dataColumnStorage.Save([]blocks.VerifiedRODataColumn{dataColumnSidecar}); err != nil {
-		return errors.Wrap(err, "save data column sidecars")
+		return errors.Wrap(err, "save data column sidecar")
 	}
 
 	return nil

beacon-chain/blockchain/setup_forchoice.go

@@ -20,7 +20,7 @@ func (s *Service) setupForkchoice(st state.BeaconState) error {
 		return errors.Wrap(err, "could not set up forkchoice checkpoints")
 	}
 	if err := s.setupForkchoiceTree(st); err != nil {
-		return errors.Wrap(err, "could not set up forkchoice root")
+		return errors.Wrap(err, "could not set up forkchoice tree")
 	}
 	if err := s.initializeHead(s.ctx, st); err != nil {
 		return errors.Wrap(err, "could not initialize head from db")
@@ -30,24 +30,24 @@ func (s *Service) setupForkchoice(st state.BeaconState) error {
 
 func (s *Service) startupHeadRoot() [32]byte {
 	headStr := features.Get().ForceHead
-	cp := s.FinalizedCheckpt()
-	fRoot := s.ensureRootNotZeros([32]byte(cp.Root))
+	jp := s.CurrentJustifiedCheckpt()
+	jRoot := s.ensureRootNotZeros([32]byte(jp.Root))
 	if headStr == "" {
-		return fRoot
+		return jRoot
 	}
 	if headStr == "head" {
 		root, err := s.cfg.BeaconDB.HeadBlockRoot()
 		if err != nil {
-			log.WithError(err).Error("Could not get head block root, starting with finalized block as head")
-			return fRoot
+			log.WithError(err).Error("Could not get head block root, starting with justified block as head")
+			return jRoot
 		}
 		log.Infof("Using Head root of %#x", root)
 		return root
 	}
 	root, err := bytesutil.DecodeHexWithLength(headStr, 32)
 	if err != nil {
-		log.WithError(err).Error("Could not parse head root, starting with finalized block as head")
-		return fRoot
+		log.WithError(err).Error("Could not parse head root, starting with justified block as head")
+		return jRoot
 	}
 	return [32]byte(root)
 }

beacon-chain/blockchain/setup_forkchoice_test.go

@@ -32,7 +32,7 @@ func Test_startupHeadRoot(t *testing.T) {
 		})
 		defer resetCfg()
 		require.Equal(t, service.startupHeadRoot(), gr)
-		require.LogsContain(t, hook, "Could not get head block root, starting with finalized block as head")
+		require.LogsContain(t, hook, "Could not get head block root, starting with justified block as head")
 	})
 
 	st, _ := util.DeterministicGenesisState(t, 64)

beacon-chain/blockchain/setup_test.go

@@ -89,7 +89,7 @@ func (mb *mockBroadcaster) BroadcastLightClientFinalityUpdate(_ context.Context,
 	return nil
 }
 
-func (mb *mockBroadcaster) BroadcastDataColumn(_ [fieldparams.RootLength]byte, _ uint64, _ *ethpb.DataColumnSidecar) error {
+func (mb *mockBroadcaster) BroadcastDataColumnSidecar(_ [fieldparams.RootLength]byte, _ uint64, _ *ethpb.DataColumnSidecar) error {
 	mb.broadcastCalled = true
 	return nil
 }

beacon-chain/builder/service.go

@@ -25,6 +25,7 @@ var ErrNoBuilder = errors.New("builder endpoint not configured")
 // BlockBuilder defines the interface for interacting with the block builder
 type BlockBuilder interface {
 	SubmitBlindedBlock(ctx context.Context, block interfaces.ReadOnlySignedBeaconBlock) (interfaces.ExecutionData, v1.BlobsBundler, error)
+	SubmitBlindedBlockPostFulu(ctx context.Context, block interfaces.ReadOnlySignedBeaconBlock) error
 	GetHeader(ctx context.Context, slot primitives.Slot, parentHash [32]byte, pubKey [48]byte) (builder.SignedBid, error)
 	RegisterValidator(ctx context.Context, reg []*ethpb.SignedValidatorRegistrationV1) error
 	RegistrationByValidatorID(ctx context.Context, id primitives.ValidatorIndex) (*ethpb.ValidatorRegistrationV1, error)
@@ -101,6 +102,22 @@ func (s *Service) SubmitBlindedBlock(ctx context.Context, b interfaces.ReadOnlyS
 	return s.c.SubmitBlindedBlock(ctx, b)
 }
 
+// SubmitBlindedBlockPostFulu submits a blinded block to the builder relay network post-Fulu.
+// After Fulu, relays only return status codes (no payload).
+func (s *Service) SubmitBlindedBlockPostFulu(ctx context.Context, b interfaces.ReadOnlySignedBeaconBlock) error {
+	ctx, span := trace.StartSpan(ctx, "builder.SubmitBlindedBlockPostFulu")
+	defer span.End()
+	start := time.Now()
+	defer func() {
+		submitBlindedBlockLatency.Observe(float64(time.Since(start).Milliseconds()))
+	}()
+	if s.c == nil {
+		return ErrNoBuilder
+	}
+
+	return s.c.SubmitBlindedBlockPostFulu(ctx, b)
+}
+
 // GetHeader retrieves the header for a given slot and parent hash from the builder relay network.
 func (s *Service) GetHeader(ctx context.Context, slot primitives.Slot, parentHash [32]byte, pubKey [48]byte) (builder.SignedBid, error) {
 	ctx, span := trace.StartSpan(ctx, "builder.GetHeader")

beacon-chain/builder/testing/mock.go

@@ -24,21 +24,22 @@ type Config struct {
 
 // MockBuilderService to mock builder.
 type MockBuilderService struct {
-	HasConfigured         bool
-	Payload               *v1.ExecutionPayload
-	PayloadCapella        *v1.ExecutionPayloadCapella
-	PayloadDeneb          *v1.ExecutionPayloadDeneb
-	BlobBundle            *v1.BlobsBundle
-	BlobBundleV2          *v1.BlobsBundleV2
-	ErrSubmitBlindedBlock error
-	Bid                   *ethpb.SignedBuilderBid
-	BidCapella            *ethpb.SignedBuilderBidCapella
-	BidDeneb              *ethpb.SignedBuilderBidDeneb
-	BidElectra            *ethpb.SignedBuilderBidElectra
-	RegistrationCache     *cache.RegistrationCache
-	ErrGetHeader          error
-	ErrRegisterValidator  error
-	Cfg                   *Config
+	HasConfigured                 bool
+	Payload                       *v1.ExecutionPayload
+	PayloadCapella                *v1.ExecutionPayloadCapella
+	PayloadDeneb                  *v1.ExecutionPayloadDeneb
+	BlobBundle                    *v1.BlobsBundle
+	BlobBundleV2                  *v1.BlobsBundleV2
+	ErrSubmitBlindedBlock         error
+	ErrSubmitBlindedBlockPostFulu error
+	Bid                           *ethpb.SignedBuilderBid
+	BidCapella                    *ethpb.SignedBuilderBidCapella
+	BidDeneb                      *ethpb.SignedBuilderBidDeneb
+	BidElectra                    *ethpb.SignedBuilderBidElectra
+	RegistrationCache             *cache.RegistrationCache
+	ErrGetHeader                  error
+	ErrRegisterValidator          error
+	Cfg                           *Config
 }
 
 // Configured for mocking.
@@ -115,3 +116,8 @@ func (s *MockBuilderService) RegistrationByValidatorID(ctx context.Context, id p
 func (s *MockBuilderService) RegisterValidator(context.Context, []*ethpb.SignedValidatorRegistrationV1) error {
 	return s.ErrRegisterValidator
 }
+
+// SubmitBlindedBlockPostFulu for mocking.
+func (s *MockBuilderService) SubmitBlindedBlockPostFulu(_ context.Context, _ interfaces.ReadOnlySignedBeaconBlock) error {
+	return s.ErrSubmitBlindedBlockPostFulu
+}

beacon-chain/core/helpers/sync_committee_test.go

@@ -78,6 +78,7 @@ func TestIsCurrentEpochSyncCommittee_UsingCommittee(t *testing.T) {
 
 func TestIsCurrentEpochSyncCommittee_DoesNotExist(t *testing.T) {
 	helpers.ClearCache()
+	params.SetupTestConfigCleanup(t)
 
 	validators := make([]*ethpb.Validator, params.BeaconConfig().SyncCommitteeSize)
 	syncCommittee := &ethpb.SyncCommittee{
@@ -264,6 +265,7 @@ func TestCurrentEpochSyncSubcommitteeIndices_UsingCommittee(t *testing.T) {
 }
 
 func TestCurrentEpochSyncSubcommitteeIndices_DoesNotExist(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
 	helpers.ClearCache()
 
 	validators := make([]*ethpb.Validator, params.BeaconConfig().SyncCommitteeSize)

beacon-chain/core/peerdas/das_core.go

@@ -223,6 +223,14 @@ func dataColumnsSidecars(
 			cellsForRow := cellsAndProofs[rowIndex].Cells
 			proofsForRow := cellsAndProofs[rowIndex].Proofs
 
+			// Validate that we have enough cells and proofs for this column index
+			if columnIndex >= uint64(len(cellsForRow)) {
+				return nil, errors.Errorf("column index %d exceeds cells length %d for blob %d", columnIndex, len(cellsForRow), rowIndex)
+			}
+			if columnIndex >= uint64(len(proofsForRow)) {
+				return nil, errors.Errorf("column index %d exceeds proofs length %d for blob %d", columnIndex, len(proofsForRow), rowIndex)
+			}
+
 			cell := cellsForRow[columnIndex]
 			column = append(column, cell)
 

beacon-chain/core/peerdas/das_core_test.go

@@ -67,6 +67,55 @@ func TestDataColumnSidecars(t *testing.T) {
 		_, err = peerdas.DataColumnSidecars(signedBeaconBlock, cellsAndProofs)
 		require.ErrorIs(t, err, peerdas.ErrSizeMismatch)
 	})
+
+	t.Run("cells array too short for column index", func(t *testing.T) {
+		// Create a Fulu block with a blob commitment.
+		signedBeaconBlockPb := util.NewBeaconBlockFulu()
+		signedBeaconBlockPb.Block.Body.BlobKzgCommitments = [][]byte{make([]byte, 48)}
+
+		// Create a signed beacon block from the protobuf.
+		signedBeaconBlock, err := blocks.NewSignedBeaconBlock(signedBeaconBlockPb)
+		require.NoError(t, err)
+
+		// Create cells and proofs with insufficient cells for the number of columns.
+		// This simulates a scenario where cellsAndProofs has fewer cells than expected columns.
+		cellsAndProofs := []kzg.CellsAndProofs{
+			{
+				Cells:  make([]kzg.Cell, 10),  // Only 10 cells
+				Proofs: make([]kzg.Proof, 10), // Only 10 proofs
+			},
+		}
+
+		// This should fail because the function will try to access columns up to NumberOfColumns
+		// but we only have 10 cells/proofs.
+		_, err = peerdas.DataColumnSidecars(signedBeaconBlock, cellsAndProofs)
+		require.ErrorContains(t, "column index", err)
+		require.ErrorContains(t, "exceeds cells length", err)
+	})
+
+	t.Run("proofs array too short for column index", func(t *testing.T) {
+		// Create a Fulu block with a blob commitment.
+		signedBeaconBlockPb := util.NewBeaconBlockFulu()
+		signedBeaconBlockPb.Block.Body.BlobKzgCommitments = [][]byte{make([]byte, 48)}
+
+		// Create a signed beacon block from the protobuf.
+		signedBeaconBlock, err := blocks.NewSignedBeaconBlock(signedBeaconBlockPb)
+		require.NoError(t, err)
+
+		// Create cells and proofs with sufficient cells but insufficient proofs.
+		numberOfColumns := params.BeaconConfig().NumberOfColumns
+		cellsAndProofs := []kzg.CellsAndProofs{
+			{
+				Cells:  make([]kzg.Cell, numberOfColumns),
+				Proofs: make([]kzg.Proof, 5), // Only 5 proofs, less than columns
+			},
+		}
+
+		// This should fail when trying to access proof beyond index 4.
+		_, err = peerdas.DataColumnSidecars(signedBeaconBlock, cellsAndProofs)
+		require.ErrorContains(t, "column index", err)
+		require.ErrorContains(t, "exceeds proofs length", err)
+	})
 }
 
 func TestComputeCustodyGroupForColumn(t *testing.T) {

beacon-chain/core/peerdas/reconstruction.go

@@ -18,8 +18,8 @@ var (
 	ErrBlobsCellsProofsMismatch = errors.New("blobs and cells proofs mismatch")
 )
 
-// MinimumColumnsCountToReconstruct return the minimum number of columns needed to proceed to a reconstruction.
-func MinimumColumnsCountToReconstruct() uint64 {
+// MinimumColumnCountToReconstruct return the minimum number of columns needed to proceed to a reconstruction.
+func MinimumColumnCountToReconstruct() uint64 {
 	// If the number of columns is odd, then we need total / 2 + 1 columns to reconstruct.
 	// If the number of columns is even, then we need total / 2 columns to reconstruct.
 	return (params.BeaconConfig().NumberOfColumns + 1) / 2
@@ -58,7 +58,7 @@ func ReconstructDataColumnSidecars(inVerifiedRoSidecars []blocks.VerifiedRODataC
 
 	// Check if there is enough sidecars to reconstruct the missing columns.
 	sidecarCount := len(sidecarByIndex)
-	if uint64(sidecarCount) < MinimumColumnsCountToReconstruct() {
+	if uint64(sidecarCount) < MinimumColumnCountToReconstruct() {
 		return nil, ErrNotEnoughDataColumnSidecars
 	}
 

beacon-chain/core/peerdas/reconstruction_test.go

@@ -48,7 +48,7 @@ func TestMinimumColumnsCountToReconstruct(t *testing.T) {
 			params.OverrideBeaconConfig(cfg)
 
 			// Compute the minimum number of columns needed to reconstruct.
-			actual := peerdas.MinimumColumnsCountToReconstruct()
+			actual := peerdas.MinimumColumnCountToReconstruct()
 			require.Equal(t, tc.expected, actual)
 		})
 	}
@@ -100,7 +100,7 @@ func TestReconstructDataColumnSidecars(t *testing.T) {
 	t.Run("not enough columns to enable reconstruction", func(t *testing.T) {
 		_, _, verifiedRoSidecars := util.GenerateTestFuluBlockWithSidecars(t, 3)
 
-		minimum := peerdas.MinimumColumnsCountToReconstruct()
+		minimum := peerdas.MinimumColumnCountToReconstruct()
 		_, err := peerdas.ReconstructDataColumnSidecars(verifiedRoSidecars[:minimum-1])
 		require.ErrorIs(t, err, peerdas.ErrNotEnoughDataColumnSidecars)
 	})

beacon-chain/das/BUILD.bazel

@@ -4,7 +4,6 @@ go_library(
     name = "go_default_library",
     srcs = [
         "availability_blobs.go",
-        "availability_columns.go",
         "blob_cache.go",
         "data_column_cache.go",
         "iface.go",
@@ -13,7 +12,6 @@ go_library(
     importpath = "github.com/OffchainLabs/prysm/v6/beacon-chain/das",
     visibility = ["//visibility:public"],
     deps = [
-        "//beacon-chain/core/peerdas:go_default_library",
         "//beacon-chain/db/filesystem:go_default_library",
         "//beacon-chain/verification:go_default_library",
         "//config/fieldparams:go_default_library",
@@ -23,7 +21,6 @@ go_library(
         "//runtime/logging:go_default_library",
         "//runtime/version:go_default_library",
         "//time/slots:go_default_library",
-        "@com_github_ethereum_go_ethereum//p2p/enode:go_default_library",
         "@com_github_pkg_errors//:go_default_library",
         "@com_github_sirupsen_logrus//:go_default_library",
     ],
@@ -33,7 +30,6 @@ go_test(
     name = "go_default_test",
     srcs = [
         "availability_blobs_test.go",
-        "availability_columns_test.go",
         "blob_cache_test.go",
         "data_column_cache_test.go",
     ],
@@ -49,7 +45,6 @@ go_test(
         "//testing/require:go_default_library",
         "//testing/util:go_default_library",
         "//time/slots:go_default_library",
-        "@com_github_ethereum_go_ethereum//p2p/enode:go_default_library",
         "@com_github_pkg_errors//:go_default_library",
     ],
 )

beacon-chain/das/availability_blobs.go

@@ -53,30 +53,25 @@ func NewLazilyPersistentStore(store *filesystem.BlobStorage, verifier BlobBatchV
 // Persist adds blobs to the working blob cache. Blobs stored in this cache will be persisted
 // for at least as long as the node is running. Once IsDataAvailable succeeds, all blobs referenced
 // by the given block are guaranteed to be persisted for the remainder of the retention period.
-func (s *LazilyPersistentStoreBlob) Persist(current primitives.Slot, sidecars ...blocks.ROSidecar) error {
+func (s *LazilyPersistentStoreBlob) Persist(current primitives.Slot, sidecars ...blocks.ROBlob) error {
 	if len(sidecars) == 0 {
 		return nil
 	}
 
-	blobSidecars, err := blocks.BlobSidecarsFromSidecars(sidecars)
-	if err != nil {
-		return errors.Wrap(err, "blob sidecars from sidecars")
-	}
-
-	if len(blobSidecars) > 1 {
-		firstRoot := blobSidecars[0].BlockRoot()
-		for _, sidecar := range blobSidecars[1:] {
+	if len(sidecars) > 1 {
+		firstRoot := sidecars[0].BlockRoot()
+		for _, sidecar := range sidecars[1:] {
 			if sidecar.BlockRoot() != firstRoot {
 				return errMixedRoots
 			}
 		}
 	}
-	if !params.WithinDAPeriod(slots.ToEpoch(blobSidecars[0].Slot()), slots.ToEpoch(current)) {
+	if !params.WithinDAPeriod(slots.ToEpoch(sidecars[0].Slot()), slots.ToEpoch(current)) {
 		return nil
 	}
-	key := keyFromSidecar(blobSidecars[0])
+	key := keyFromSidecar(sidecars[0])
 	entry := s.cache.ensure(key)
-	for _, blobSidecar := range blobSidecars {
+	for _, blobSidecar := range sidecars {
 		if err := entry.stash(&blobSidecar); err != nil {
 			return err
 		}

beacon-chain/das/availability_blobs_test.go

@@ -118,23 +118,21 @@ func TestLazilyPersistent_Missing(t *testing.T) {
 
 	blk, blobSidecars := util.GenerateTestDenebBlockWithSidecar(t, [32]byte{}, 1, 3)
 
-	scs := blocks.NewSidecarsFromBlobSidecars(blobSidecars)
-
 	mbv := &mockBlobBatchVerifier{t: t, scs: blobSidecars}
 	as := NewLazilyPersistentStore(store, mbv)
 
 	// Only one commitment persisted, should return error with other indices
-	require.NoError(t, as.Persist(1, scs[2]))
+	require.NoError(t, as.Persist(1, blobSidecars[2]))
 	err := as.IsDataAvailable(ctx, 1, blk)
 	require.ErrorIs(t, err, errMissingSidecar)
 
 	// All but one persisted, return missing idx
-	require.NoError(t, as.Persist(1, scs[0]))
+	require.NoError(t, as.Persist(1, blobSidecars[0]))
 	err = as.IsDataAvailable(ctx, 1, blk)
 	require.ErrorIs(t, err, errMissingSidecar)
 
 	// All persisted, return nil
-	require.NoError(t, as.Persist(1, scs...))
+	require.NoError(t, as.Persist(1, blobSidecars...))
 
 	require.NoError(t, as.IsDataAvailable(ctx, 1, blk))
 }
@@ -149,10 +147,8 @@ func TestLazilyPersistent_Mismatch(t *testing.T) {
 	blobSidecars[0].KzgCommitment = bytesutil.PadTo([]byte("nope"), 48)
 	as := NewLazilyPersistentStore(store, mbv)
 
-	scs := blocks.NewSidecarsFromBlobSidecars(blobSidecars)
-
 	// Only one commitment persisted, should return error with other indices
-	require.NoError(t, as.Persist(1, scs[0]))
+	require.NoError(t, as.Persist(1, blobSidecars[0]))
 	err := as.IsDataAvailable(ctx, 1, blk)
 	require.NotNil(t, err)
 	require.ErrorIs(t, err, errCommitmentMismatch)
@@ -161,29 +157,25 @@ func TestLazilyPersistent_Mismatch(t *testing.T) {
 func TestLazyPersistOnceCommitted(t *testing.T) {
 	_, blobSidecars := util.GenerateTestDenebBlockWithSidecar(t, [32]byte{}, 1, 6)
 
-	scs := blocks.NewSidecarsFromBlobSidecars(blobSidecars)
-
 	as := NewLazilyPersistentStore(filesystem.NewEphemeralBlobStorage(t), &mockBlobBatchVerifier{})
 	// stashes as expected
-	require.NoError(t, as.Persist(1, scs...))
+	require.NoError(t, as.Persist(1, blobSidecars...))
 	// ignores duplicates
-	require.ErrorIs(t, as.Persist(1, scs...), ErrDuplicateSidecar)
+	require.ErrorIs(t, as.Persist(1, blobSidecars...), ErrDuplicateSidecar)
 
 	// ignores index out of bound
 	blobSidecars[0].Index = 6
-	require.ErrorIs(t, as.Persist(1, blocks.NewSidecarFromBlobSidecar(blobSidecars[0])), errIndexOutOfBounds)
+	require.ErrorIs(t, as.Persist(1, blobSidecars[0]), errIndexOutOfBounds)
 
 	_, moreBlobSidecars := util.GenerateTestDenebBlockWithSidecar(t, [32]byte{}, 1, 4)
 
-	more := blocks.NewSidecarsFromBlobSidecars(moreBlobSidecars)
-
 	// ignores sidecars before the retention period
 	slotOOB, err := slots.EpochStart(params.BeaconConfig().MinEpochsForBlobsSidecarsRequest)
 	require.NoError(t, err)
-	require.NoError(t, as.Persist(32+slotOOB, more[0]))
+	require.NoError(t, as.Persist(32+slotOOB, moreBlobSidecars[0]))
 
 	// doesn't ignore new sidecars with a different block root
-	require.NoError(t, as.Persist(1, more...))
+	require.NoError(t, as.Persist(1, moreBlobSidecars...))
 }
 
 type mockBlobBatchVerifier struct {

beacon-chain/das/availability_columns.go

@@ -1,213 +0,0 @@
-package das
-
-import (
-	"context"
-
-	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/peerdas"
-	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/filesystem"
-	"github.com/OffchainLabs/prysm/v6/beacon-chain/verification"
-	"github.com/OffchainLabs/prysm/v6/config/params"
-	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
-	"github.com/OffchainLabs/prysm/v6/consensus-types/primitives"
-	"github.com/OffchainLabs/prysm/v6/runtime/version"
-	"github.com/OffchainLabs/prysm/v6/time/slots"
-	"github.com/ethereum/go-ethereum/p2p/enode"
-	errors "github.com/pkg/errors"
-)
-
-// LazilyPersistentStoreColumn is an implementation of AvailabilityStore to be used when batch syncing data columns.
-// This implementation will hold any data columns passed to Persist until the IsDataAvailable is called for their
-// block, at which time they will undergo full verification and be saved to the disk.
-type LazilyPersistentStoreColumn struct {
-	store                  *filesystem.DataColumnStorage
-	nodeID                 enode.ID
-	cache                  *dataColumnCache
-	newDataColumnsVerifier verification.NewDataColumnsVerifier
-	custodyGroupCount      uint64
-}
-
-var _ AvailabilityStore = &LazilyPersistentStoreColumn{}
-
-// DataColumnsVerifier enables LazilyPersistentStoreColumn to manage the verification process
-// going from RODataColumn->VerifiedRODataColumn, while avoiding the decision of which individual verifications
-// to run and in what order. Since LazilyPersistentStoreColumn always tries to verify and save data columns only when
-// they are all available, the interface takes a slice of data column sidecars.
-type DataColumnsVerifier interface {
-	VerifiedRODataColumns(ctx context.Context, blk blocks.ROBlock, scs []blocks.RODataColumn) ([]blocks.VerifiedRODataColumn, error)
-}
-
-// NewLazilyPersistentStoreColumn creates a new LazilyPersistentStoreColumn.
-// WARNING: The resulting LazilyPersistentStoreColumn is NOT thread-safe.
-func NewLazilyPersistentStoreColumn(
-	store *filesystem.DataColumnStorage,
-	nodeID enode.ID,
-	newDataColumnsVerifier verification.NewDataColumnsVerifier,
-	custodyGroupCount uint64,
-) *LazilyPersistentStoreColumn {
-	return &LazilyPersistentStoreColumn{
-		store:                  store,
-		nodeID:                 nodeID,
-		cache:                  newDataColumnCache(),
-		newDataColumnsVerifier: newDataColumnsVerifier,
-		custodyGroupCount:      custodyGroupCount,
-	}
-}
-
-// PersistColumns adds columns to the working column cache. Columns stored in this cache will be persisted
-// for at least as long as the node is running. Once IsDataAvailable succeeds, all columns referenced
-// by the given block are guaranteed to be persisted for the remainder of the retention period.
-func (s *LazilyPersistentStoreColumn) Persist(current primitives.Slot, sidecars ...blocks.ROSidecar) error {
-	if len(sidecars) == 0 {
-		return nil
-	}
-
-	dataColumnSidecars, err := blocks.DataColumnSidecarsFromSidecars(sidecars)
-	if err != nil {
-		return errors.Wrap(err, "blob sidecars from sidecars")
-	}
-
-	// It is safe to retrieve the first sidecar.
-	firstSidecar := dataColumnSidecars[0]
-
-	if len(sidecars) > 1 {
-		firstRoot := firstSidecar.BlockRoot()
-		for _, sidecar := range dataColumnSidecars[1:] {
-			if sidecar.BlockRoot() != firstRoot {
-				return errMixedRoots
-			}
-		}
-	}
-
-	firstSidecarEpoch, currentEpoch := slots.ToEpoch(firstSidecar.Slot()), slots.ToEpoch(current)
-	if !params.WithinDAPeriod(firstSidecarEpoch, currentEpoch) {
-		return nil
-	}
-
-	key := cacheKey{slot: firstSidecar.Slot(), root: firstSidecar.BlockRoot()}
-	entry := s.cache.ensure(key)
-
-	for _, sidecar := range dataColumnSidecars {
-		if err := entry.stash(&sidecar); err != nil {
-			return errors.Wrap(err, "stash DataColumnSidecar")
-		}
-	}
-
-	return nil
-}
-
-// IsDataAvailable returns nil if all the commitments in the given block are persisted to the db and have been verified.
-// DataColumnsSidecars already in the db are assumed to have been previously verified against the block.
-func (s *LazilyPersistentStoreColumn) IsDataAvailable(ctx context.Context, currentSlot primitives.Slot, block blocks.ROBlock) error {
-	blockCommitments, err := s.fullCommitmentsToCheck(s.nodeID, block, currentSlot)
-	if err != nil {
-		return errors.Wrapf(err, "full commitments to check with block root `%#x` and current slot `%d`", block.Root(), currentSlot)
-	}
-
-	// Return early for blocks that do not have any commitments.
-	if blockCommitments.count() == 0 {
-		return nil
-	}
-
-	// Get the root of the block.
-	blockRoot := block.Root()
-
-	// Build the cache key for the block.
-	key := cacheKey{slot: block.Block().Slot(), root: blockRoot}
-
-	// Retrieve the cache entry for the block, or create an empty one if it doesn't exist.
-	entry := s.cache.ensure(key)
-
-	// Delete the cache entry for the block at the end.
-	defer s.cache.delete(key)
-
-	// Set the disk summary for the block in the cache entry.
-	entry.setDiskSummary(s.store.Summary(blockRoot))
-
-	// Verify we have all the expected sidecars, and fail fast if any are missing or inconsistent.
-	// We don't try to salvage problematic batches because this indicates a misbehaving peer and we'd rather
-	// ignore their response and decrease their peer score.
-	roDataColumns, err := entry.filter(blockRoot, blockCommitments)
-	if err != nil {
-		return errors.Wrap(err, "entry filter")
-	}
-
-	// https://github.com/ethereum/consensus-specs/blob/master/specs/fulu/p2p-interface.md#datacolumnsidecarsbyrange-v1
-	verifier := s.newDataColumnsVerifier(roDataColumns, verification.ByRangeRequestDataColumnSidecarRequirements)
-
-	if err := verifier.ValidFields(); err != nil {
-		return errors.Wrap(err, "valid fields")
-	}
-
-	if err := verifier.SidecarInclusionProven(); err != nil {
-		return errors.Wrap(err, "sidecar inclusion proven")
-	}
-
-	if err := verifier.SidecarKzgProofVerified(); err != nil {
-		return errors.Wrap(err, "sidecar KZG proof verified")
-	}
-
-	verifiedRoDataColumns, err := verifier.VerifiedRODataColumns()
-	if err != nil {
-		return errors.Wrap(err, "verified RO data columns - should never happen")
-	}
-
-	if err := s.store.Save(verifiedRoDataColumns); err != nil {
-		return errors.Wrap(err, "save data column sidecars")
-	}
-
-	return nil
-}
-
-// fullCommitmentsToCheck returns the commitments to check for a given block.
-func (s *LazilyPersistentStoreColumn) fullCommitmentsToCheck(nodeID enode.ID, block blocks.ROBlock, currentSlot primitives.Slot) (*safeCommitmentsArray, error) {
-	samplesPerSlot := params.BeaconConfig().SamplesPerSlot
-
-	// Return early for blocks that are pre-Fulu.
-	if block.Version() < version.Fulu {
-		return &safeCommitmentsArray{}, nil
-	}
-
-	// Compute the block epoch.
-	blockSlot := block.Block().Slot()
-	blockEpoch := slots.ToEpoch(blockSlot)
-
-	// Compute the current epoch.
-	currentEpoch := slots.ToEpoch(currentSlot)
-
-	// Return early if the request is out of the MIN_EPOCHS_FOR_DATA_COLUMN_SIDECARS_REQUESTS window.
-	if !params.WithinDAPeriod(blockEpoch, currentEpoch) {
-		return &safeCommitmentsArray{}, nil
-	}
-
-	// Retrieve the KZG commitments for the block.
-	kzgCommitments, err := block.Block().Body().BlobKzgCommitments()
-	if err != nil {
-		return nil, errors.Wrap(err, "blob KZG commitments")
-	}
-
-	// Return early if there are no commitments in the block.
-	if len(kzgCommitments) == 0 {
-		return &safeCommitmentsArray{}, nil
-	}
-
-	// Retrieve peer info.
-	samplingSize := max(s.custodyGroupCount, samplesPerSlot)
-	peerInfo, _, err := peerdas.Info(nodeID, samplingSize)
-	if err != nil {
-		return nil, errors.Wrap(err, "peer info")
-	}
-
-	// Create a safe commitments array for the custody columns.
-	commitmentsArray := &safeCommitmentsArray{}
-	commitmentsArraySize := uint64(len(commitmentsArray))
-
-	for column := range peerInfo.CustodyColumns {
-		if column >= commitmentsArraySize {
-			return nil, errors.Errorf("custody column index %d too high (max allowed %d) - should never happen", column, commitmentsArraySize)
-		}
-
-		commitmentsArray[column] = kzgCommitments
-	}
-
-	return commitmentsArray, nil
-}

beacon-chain/das/availability_columns_test.go

@@ -1,313 +0,0 @@
-package das
-
-import (
-	"context"
-	"testing"
-
-	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/filesystem"
-	"github.com/OffchainLabs/prysm/v6/beacon-chain/verification"
-	fieldparams "github.com/OffchainLabs/prysm/v6/config/fieldparams"
-	"github.com/OffchainLabs/prysm/v6/config/params"
-	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
-	"github.com/OffchainLabs/prysm/v6/consensus-types/primitives"
-	"github.com/OffchainLabs/prysm/v6/encoding/bytesutil"
-	"github.com/OffchainLabs/prysm/v6/testing/require"
-	"github.com/OffchainLabs/prysm/v6/testing/util"
-	"github.com/OffchainLabs/prysm/v6/time/slots"
-	"github.com/ethereum/go-ethereum/p2p/enode"
-)
-
-var commitments = [][]byte{
-	bytesutil.PadTo([]byte("a"), 48),
-	bytesutil.PadTo([]byte("b"), 48),
-	bytesutil.PadTo([]byte("c"), 48),
-	bytesutil.PadTo([]byte("d"), 48),
-}
-
-func TestPersist(t *testing.T) {
-	t.Run("no sidecars", func(t *testing.T) {
-		dataColumnStorage := filesystem.NewEphemeralDataColumnStorage(t)
-		lazilyPersistentStoreColumns := NewLazilyPersistentStoreColumn(dataColumnStorage, enode.ID{}, nil, 0)
-		err := lazilyPersistentStoreColumns.Persist(0)
-		require.NoError(t, err)
-		require.Equal(t, 0, len(lazilyPersistentStoreColumns.cache.entries))
-	})
-
-	t.Run("mixed roots", func(t *testing.T) {
-		dataColumnStorage := filesystem.NewEphemeralDataColumnStorage(t)
-
-		dataColumnParamsByBlockRoot := []util.DataColumnParam{
-			{Slot: 1, Index: 1},
-			{Slot: 2, Index: 2},
-		}
-
-		roSidecars, _ := roSidecarsFromDataColumnParamsByBlockRoot(t, dataColumnParamsByBlockRoot)
-		lazilyPersistentStoreColumns := NewLazilyPersistentStoreColumn(dataColumnStorage, enode.ID{}, nil, 0)
-
-		err := lazilyPersistentStoreColumns.Persist(0, roSidecars...)
-		require.ErrorIs(t, err, errMixedRoots)
-		require.Equal(t, 0, len(lazilyPersistentStoreColumns.cache.entries))
-	})
-
-	t.Run("outside DA period", func(t *testing.T) {
-		dataColumnStorage := filesystem.NewEphemeralDataColumnStorage(t)
-
-		dataColumnParamsByBlockRoot := []util.DataColumnParam{
-			{Slot: 1, Index: 1},
-		}
-
-		roSidecars, _ := roSidecarsFromDataColumnParamsByBlockRoot(t, dataColumnParamsByBlockRoot)
-		lazilyPersistentStoreColumns := NewLazilyPersistentStoreColumn(dataColumnStorage, enode.ID{}, nil, 0)
-
-		err := lazilyPersistentStoreColumns.Persist(1_000_000, roSidecars...)
-		require.NoError(t, err)
-		require.Equal(t, 0, len(lazilyPersistentStoreColumns.cache.entries))
-	})
-
-	t.Run("nominal", func(t *testing.T) {
-		const slot = 42
-		dataColumnStorage := filesystem.NewEphemeralDataColumnStorage(t)
-
-		dataColumnParamsByBlockRoot := []util.DataColumnParam{
-			{Slot: slot, Index: 1},
-			{Slot: slot, Index: 5},
-		}
-
-		roSidecars, roDataColumns := roSidecarsFromDataColumnParamsByBlockRoot(t, dataColumnParamsByBlockRoot)
-		lazilyPersistentStoreColumns := NewLazilyPersistentStoreColumn(dataColumnStorage, enode.ID{}, nil, 0)
-
-		err := lazilyPersistentStoreColumns.Persist(slot, roSidecars...)
-		require.NoError(t, err)
-		require.Equal(t, 1, len(lazilyPersistentStoreColumns.cache.entries))
-
-		key := cacheKey{slot: slot, root: roDataColumns[0].BlockRoot()}
-		entry, ok := lazilyPersistentStoreColumns.cache.entries[key]
-		require.Equal(t, true, ok)
-
-		// A call to Persist does NOT save the sidecars to disk.
-		require.Equal(t, uint64(0), entry.diskSummary.Count())
-
-		require.DeepSSZEqual(t, roDataColumns[0], *entry.scs[1])
-		require.DeepSSZEqual(t, roDataColumns[1], *entry.scs[5])
-
-		for i, roDataColumn := range entry.scs {
-			if map[int]bool{1: true, 5: true}[i] {
-				continue
-			}
-
-			require.IsNil(t, roDataColumn)
-		}
-	})
-}
-
-func TestIsDataAvailable(t *testing.T) {
-	newDataColumnsVerifier := func(dataColumnSidecars []blocks.RODataColumn, _ []verification.Requirement) verification.DataColumnsVerifier {
-		return &mockDataColumnsVerifier{t: t, dataColumnSidecars: dataColumnSidecars}
-	}
-
-	ctx := t.Context()
-
-	t.Run("without commitments", func(t *testing.T) {
-		signedBeaconBlockFulu := util.NewBeaconBlockFulu()
-		signedRoBlock := newSignedRoBlock(t, signedBeaconBlockFulu)
-
-		dataColumnStorage := filesystem.NewEphemeralDataColumnStorage(t)
-		lazilyPersistentStoreColumns := NewLazilyPersistentStoreColumn(dataColumnStorage, enode.ID{}, newDataColumnsVerifier, 0)
-
-		err := lazilyPersistentStoreColumns.IsDataAvailable(ctx, 0 /*current slot*/, signedRoBlock)
-		require.NoError(t, err)
-	})
-
-	t.Run("with commitments", func(t *testing.T) {
-		signedBeaconBlockFulu := util.NewBeaconBlockFulu()
-		signedBeaconBlockFulu.Block.Body.BlobKzgCommitments = commitments
-		signedRoBlock := newSignedRoBlock(t, signedBeaconBlockFulu)
-		block := signedRoBlock.Block()
-		slot := block.Slot()
-		proposerIndex := block.ProposerIndex()
-		parentRoot := block.ParentRoot()
-		stateRoot := block.StateRoot()
-		bodyRoot, err := block.Body().HashTreeRoot()
-		require.NoError(t, err)
-
-		root := signedRoBlock.Root()
-
-		dataColumnStorage := filesystem.NewEphemeralDataColumnStorage(t)
-		lazilyPersistentStoreColumns := NewLazilyPersistentStoreColumn(dataColumnStorage, enode.ID{}, newDataColumnsVerifier, 0)
-
-		indices := [...]uint64{1, 17, 19, 42, 75, 87, 102, 117}
-		dataColumnsParams := make([]util.DataColumnParam, 0, len(indices))
-		for _, index := range indices {
-			dataColumnParams := util.DataColumnParam{
-				Index:          index,
-				KzgCommitments: commitments,
-
-				Slot:          slot,
-				ProposerIndex: proposerIndex,
-				ParentRoot:    parentRoot[:],
-				StateRoot:     stateRoot[:],
-				BodyRoot:      bodyRoot[:],
-			}
-
-			dataColumnsParams = append(dataColumnsParams, dataColumnParams)
-		}
-
-		_, verifiedRoDataColumns := util.CreateTestVerifiedRoDataColumnSidecars(t, dataColumnsParams)
-
-		key := cacheKey{root: root}
-		entry := lazilyPersistentStoreColumns.cache.ensure(key)
-		defer lazilyPersistentStoreColumns.cache.delete(key)
-
-		for _, verifiedRoDataColumn := range verifiedRoDataColumns {
-			err := entry.stash(&verifiedRoDataColumn.RODataColumn)
-			require.NoError(t, err)
-		}
-
-		err = lazilyPersistentStoreColumns.IsDataAvailable(ctx, slot, signedRoBlock)
-		require.NoError(t, err)
-
-		actual, err := dataColumnStorage.Get(root, indices[:])
-		require.NoError(t, err)
-
-		summary := dataColumnStorage.Summary(root)
-		require.Equal(t, uint64(len(indices)), summary.Count())
-		require.DeepSSZEqual(t, verifiedRoDataColumns, actual)
-	})
-}
-
-func TestFullCommitmentsToCheck(t *testing.T) {
-	windowSlots, err := slots.EpochEnd(params.BeaconConfig().MinEpochsForDataColumnSidecarsRequest)
-	require.NoError(t, err)
-
-	testCases := []struct {
-		name        string
-		commitments [][]byte
-		block       func(*testing.T) blocks.ROBlock
-		slot        primitives.Slot
-	}{
-		{
-			name: "Pre-Fulu block",
-			block: func(t *testing.T) blocks.ROBlock {
-				return newSignedRoBlock(t, util.NewBeaconBlockElectra())
-			},
-		},
-		{
-			name: "Commitments outside data availability window",
-			block: func(t *testing.T) blocks.ROBlock {
-				beaconBlockElectra := util.NewBeaconBlockElectra()
-
-				// Block is from slot 0, "current slot" is window size +1 (so outside the window)
-				beaconBlockElectra.Block.Body.BlobKzgCommitments = commitments
-
-				return newSignedRoBlock(t, beaconBlockElectra)
-			},
-			slot: windowSlots + 1,
-		},
-		{
-			name: "Commitments within data availability window",
-			block: func(t *testing.T) blocks.ROBlock {
-				signedBeaconBlockFulu := util.NewBeaconBlockFulu()
-				signedBeaconBlockFulu.Block.Body.BlobKzgCommitments = commitments
-				signedBeaconBlockFulu.Block.Slot = 100
-
-				return newSignedRoBlock(t, signedBeaconBlockFulu)
-			},
-			commitments: commitments,
-			slot:        100,
-		},
-	}
-
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			numberOfColumns := params.BeaconConfig().NumberOfColumns
-
-			b := tc.block(t)
-			s := NewLazilyPersistentStoreColumn(nil, enode.ID{}, nil, numberOfColumns)
-
-			commitmentsArray, err := s.fullCommitmentsToCheck(enode.ID{}, b, tc.slot)
-			require.NoError(t, err)
-
-			for _, commitments := range commitmentsArray {
-				require.DeepEqual(t, tc.commitments, commitments)
-			}
-		})
-	}
-}
-
-func roSidecarsFromDataColumnParamsByBlockRoot(t *testing.T, parameters []util.DataColumnParam) ([]blocks.ROSidecar, []blocks.RODataColumn) {
-	roDataColumns, _ := util.CreateTestVerifiedRoDataColumnSidecars(t, parameters)
-
-	roSidecars := make([]blocks.ROSidecar, 0, len(roDataColumns))
-	for _, roDataColumn := range roDataColumns {
-		roSidecars = append(roSidecars, blocks.NewSidecarFromDataColumnSidecar(roDataColumn))
-	}
-
-	return roSidecars, roDataColumns
-}
-
-func newSignedRoBlock(t *testing.T, signedBeaconBlock interface{}) blocks.ROBlock {
-	sb, err := blocks.NewSignedBeaconBlock(signedBeaconBlock)
-	require.NoError(t, err)
-
-	rb, err := blocks.NewROBlock(sb)
-	require.NoError(t, err)
-
-	return rb
-}
-
-type mockDataColumnsVerifier struct {
-	t                                                                        *testing.T
-	dataColumnSidecars                                                       []blocks.RODataColumn
-	validCalled, SidecarInclusionProvenCalled, SidecarKzgProofVerifiedCalled bool
-}
-
-var _ verification.DataColumnsVerifier = &mockDataColumnsVerifier{}
-
-func (m *mockDataColumnsVerifier) VerifiedRODataColumns() ([]blocks.VerifiedRODataColumn, error) {
-	require.Equal(m.t, true, m.validCalled && m.SidecarInclusionProvenCalled && m.SidecarKzgProofVerifiedCalled)
-
-	verifiedDataColumnSidecars := make([]blocks.VerifiedRODataColumn, 0, len(m.dataColumnSidecars))
-	for _, dataColumnSidecar := range m.dataColumnSidecars {
-		verifiedDataColumnSidecar := blocks.NewVerifiedRODataColumn(dataColumnSidecar)
-		verifiedDataColumnSidecars = append(verifiedDataColumnSidecars, verifiedDataColumnSidecar)
-	}
-
-	return verifiedDataColumnSidecars, nil
-}
-
-func (m *mockDataColumnsVerifier) SatisfyRequirement(verification.Requirement) {}
-
-func (m *mockDataColumnsVerifier) ValidFields() error {
-	m.validCalled = true
-	return nil
-}
-
-func (m *mockDataColumnsVerifier) CorrectSubnet(dataColumnSidecarSubTopic string, expectedTopics []string) error {
-	return nil
-}
-func (m *mockDataColumnsVerifier) NotFromFutureSlot() error                         { return nil }
-func (m *mockDataColumnsVerifier) SlotAboveFinalized() error                        { return nil }
-func (m *mockDataColumnsVerifier) ValidProposerSignature(ctx context.Context) error { return nil }
-
-func (m *mockDataColumnsVerifier) SidecarParentSeen(parentSeen func([fieldparams.RootLength]byte) bool) error {
-	return nil
-}
-
-func (m *mockDataColumnsVerifier) SidecarParentValid(badParent func([fieldparams.RootLength]byte) bool) error {
-	return nil
-}
-
-func (m *mockDataColumnsVerifier) SidecarParentSlotLower() error       { return nil }
-func (m *mockDataColumnsVerifier) SidecarDescendsFromFinalized() error { return nil }
-
-func (m *mockDataColumnsVerifier) SidecarInclusionProven() error {
-	m.SidecarInclusionProvenCalled = true
-	return nil
-}
-
-func (m *mockDataColumnsVerifier) SidecarKzgProofVerified() error {
-	m.SidecarKzgProofVerifiedCalled = true
-	return nil
-}
-
-func (m *mockDataColumnsVerifier) SidecarProposerExpected(ctx context.Context) error { return nil }

beacon-chain/das/blob_cache.go

@@ -99,20 +99,26 @@ func (e *blobCacheEntry) filter(root [32]byte, kc [][]byte, slot primitives.Slot
 		if e.diskSummary.HasIndex(i) {
 			continue
 		}
+		// Check if e.scs has this index before accessing
+		var sidecar *blocks.ROBlob
+		if i < uint64(len(e.scs)) {
+			sidecar = e.scs[i]
+		}
+
 		if kc[i] == nil {
-			if e.scs[i] != nil {
-				return nil, errors.Wrapf(errCommitmentMismatch, "root=%#x, index=%#x, commitment=%#x, no block commitment", root, i, e.scs[i].KzgCommitment)
+			if sidecar != nil {
+				return nil, errors.Wrapf(errCommitmentMismatch, "root=%#x, index=%#x, commitment=%#x, no block commitment", root, i, sidecar.KzgCommitment)
 			}
 			continue
 		}
 
-		if e.scs[i] == nil {
+		if sidecar == nil {
 			return nil, errors.Wrapf(errMissingSidecar, "root=%#x, index=%#x", root, i)
 		}
-		if !bytes.Equal(kc[i], e.scs[i].KzgCommitment) {
-			return nil, errors.Wrapf(errCommitmentMismatch, "root=%#x, index=%#x, commitment=%#x, block commitment=%#x", root, i, e.scs[i].KzgCommitment, kc[i])
+		if !bytes.Equal(kc[i], sidecar.KzgCommitment) {
+			return nil, errors.Wrapf(errCommitmentMismatch, "root=%#x, index=%#x, commitment=%#x, block commitment=%#x", root, i, sidecar.KzgCommitment, kc[i])
 		}
-		scs = append(scs, *e.scs[i])
+		scs = append(scs, *sidecar)
 	}
 
 	return scs, nil

beacon-chain/das/blob_cache_test.go

@@ -155,6 +155,41 @@ func TestFilter(t *testing.T) {
 			},
 			err: errCommitmentMismatch,
 		},
+		{
+			name: "empty scs array with commitments",
+			setup: func(t *testing.T) (*blobCacheEntry, [][]byte, []blocks.ROBlob) {
+				// This reproduces the panic condition where entry.scs is empty or nil
+				// but we have commitments to check
+				entry := &blobCacheEntry{
+					scs: nil, // Empty/nil array that caused the panic
+				}
+				// Create a commitment that would trigger the check at index 0
+				commits := [][]byte{
+					bytesutil.PadTo([]byte("commitment1"), 48),
+				}
+				return entry, commits, nil
+			},
+			err: errMissingSidecar,
+		},
+		{
+			name: "scs array shorter than commitments",
+			setup: func(t *testing.T) (*blobCacheEntry, [][]byte, []blocks.ROBlob) {
+				// This reproduces the condition where entry.scs exists but is shorter
+				// than the number of commitments we're checking
+				entry := &blobCacheEntry{
+					scs: make([]*blocks.ROBlob, 2), // Only 2 slots
+				}
+				// Create 4 commitments, accessing index 2 and 3 would have panicked
+				commits := [][]byte{
+					nil,
+					nil,
+					bytesutil.PadTo([]byte("commitment3"), 48),
+					bytesutil.PadTo([]byte("commitment4"), 48),
+				}
+				return entry, commits, nil
+			},
+			err: errMissingSidecar,
+		},
 	}
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {

beacon-chain/das/iface.go

@@ -15,5 +15,5 @@ import (
 // durably persisted before returning a non-error value.
 type AvailabilityStore interface {
 	IsDataAvailable(ctx context.Context, current primitives.Slot, b blocks.ROBlock) error
-	Persist(current primitives.Slot, sc ...blocks.ROSidecar) error
+	Persist(current primitives.Slot, blobSidecar ...blocks.ROBlob) error
 }

beacon-chain/das/mock.go

@@ -5,13 +5,12 @@ import (
 
 	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/primitives"
-	errors "github.com/pkg/errors"
 )
 
 // MockAvailabilityStore is an implementation of AvailabilityStore that can be used by other packages in tests.
 type MockAvailabilityStore struct {
 	VerifyAvailabilityCallback func(ctx context.Context, current primitives.Slot, b blocks.ROBlock) error
-	PersistBlobsCallback       func(current primitives.Slot, sc ...blocks.ROBlob) error
+	PersistBlobsCallback       func(current primitives.Slot, blobSidecar ...blocks.ROBlob) error
 }
 
 var _ AvailabilityStore = &MockAvailabilityStore{}
@@ -25,13 +24,9 @@ func (m *MockAvailabilityStore) IsDataAvailable(ctx context.Context, current pri
 }
 
 // Persist satisfies the corresponding method of the AvailabilityStore interface in a way that is useful for tests.
-func (m *MockAvailabilityStore) Persist(current primitives.Slot, sc ...blocks.ROSidecar) error {
-	blobSidecars, err := blocks.BlobSidecarsFromSidecars(sc)
-	if err != nil {
-		return errors.Wrap(err, "blob sidecars from sidecars")
-	}
+func (m *MockAvailabilityStore) Persist(current primitives.Slot, blobSidecar ...blocks.ROBlob) error {
 	if m.PersistBlobsCallback != nil {
-		return m.PersistBlobsCallback(current, blobSidecars...)
+		return m.PersistBlobsCallback(current, blobSidecar...)
 	}
 	return nil
 }

beacon-chain/db/filesystem/data_column.go

@@ -100,6 +100,14 @@ type (
 	}
 )
 
+// DataColumnStorageReader is an interface to read data column sidecars from the filesystem.
+type DataColumnStorageReader interface {
+	Summary(root [fieldparams.RootLength]byte) DataColumnStorageSummary
+	Get(root [fieldparams.RootLength]byte, indices []uint64) ([]blocks.VerifiedRODataColumn, error)
+}
+
+var _ DataColumnStorageReader = &DataColumnStorage{}
+
 // WithDataColumnBasePath is a required option that sets the base path of data column storage.
 func WithDataColumnBasePath(base string) DataColumnStorageOption {
 	return func(b *DataColumnStorage) error {

beacon-chain/db/filesystem/data_column_cache.go

@@ -84,12 +84,6 @@ func (s DataColumnStorageSummary) Stored() map[uint64]bool {
 	return stored
 }
 
-// DataColumnStorageSummarizer can be used to receive a summary of metadata about data columns on disk for a given root.
-// The DataColumnStorageSummary can be used to check which indices (if any) are available for a given block by root.
-type DataColumnStorageSummarizer interface {
-	Summary(root [fieldparams.RootLength]byte) DataColumnStorageSummary
-}
-
 type dataColumnStorageSummaryCache struct {
 	mu                 sync.RWMutex
 	dataColumnCount    float64
@@ -98,8 +92,6 @@ type dataColumnStorageSummaryCache struct {
 	cache              map[[fieldparams.RootLength]byte]DataColumnStorageSummary
 }
 
-var _ DataColumnStorageSummarizer = &dataColumnStorageSummaryCache{}
-
 func newDataColumnStorageSummaryCache() *dataColumnStorageSummaryCache {
 	return &dataColumnStorageSummaryCache{
 		cache:             make(map[[fieldparams.RootLength]byte]DataColumnStorageSummary),

beacon-chain/db/filesystem/mock.go

@@ -144,14 +144,3 @@ func NewEphemeralDataColumnStorageWithMocker(t testing.TB) (*DataColumnMocker, *
 	fs, dcs := NewEphemeralDataColumnStorageAndFs(t)
 	return &DataColumnMocker{fs: fs, dcs: dcs}, dcs
 }
-
-func NewMockDataColumnStorageSummarizer(t *testing.T, set map[[fieldparams.RootLength]byte][]uint64) DataColumnStorageSummarizer {
-	c := newDataColumnStorageSummaryCache()
-	for root, indices := range set {
-		if err := c.set(DataColumnsIdent{Root: root, Epoch: 0, Indices: indices}); err != nil {
-			t.Fatal(err)
-		}
-	}
-
-	return c
-}

beacon-chain/db/iface/interface.go

@@ -115,6 +115,17 @@ type NoHeadAccessDatabase interface {
 	CleanUpDirtyStates(ctx context.Context, slotsPerArchivedPoint primitives.Slot) error
 	DeleteHistoricalDataBeforeSlot(ctx context.Context, slot primitives.Slot, batchSize int) (int, error)
 
+	// Genesis operations.
+	LoadGenesis(ctx context.Context, stateBytes []byte) error
+	SaveGenesisData(ctx context.Context, state state.BeaconState) error
+	EnsureEmbeddedGenesis(ctx context.Context) error
+
+	// Support for checkpoint sync and backfill.
+	SaveOriginCheckpointBlockRoot(ctx context.Context, blockRoot [32]byte) error
+	SaveOrigin(ctx context.Context, serState, serBlock []byte) error
+	SaveBackfillStatus(context.Context, *dbval.BackfillStatus) error
+	BackfillFinalizedIndex(ctx context.Context, blocks []blocks.ROBlock, finalizedChildRoot [32]byte) error
+
 	// Custody operations.
 	UpdateSubscribedToAllDataSubnets(ctx context.Context, subscribed bool) (bool, error)
 	UpdateCustodyInfo(ctx context.Context, earliestAvailableSlot primitives.Slot, custodyGroupCount uint64) (primitives.Slot, uint64, error)
@@ -131,16 +142,6 @@ type HeadAccessDatabase interface {
 	HeadBlock(ctx context.Context) (interfaces.ReadOnlySignedBeaconBlock, error)
 	HeadBlockRoot() ([32]byte, error)
 	SaveHeadBlockRoot(ctx context.Context, blockRoot [32]byte) error
-
-	// Genesis operations.
-	LoadGenesis(ctx context.Context, stateBytes []byte) error
-	SaveGenesisData(ctx context.Context, state state.BeaconState) error
-	EnsureEmbeddedGenesis(ctx context.Context) error
-
-	// Support for checkpoint sync and backfill.
-	SaveOrigin(ctx context.Context, serState, serBlock []byte) error
-	SaveBackfillStatus(context.Context, *dbval.BackfillStatus) error
-	BackfillFinalizedIndex(ctx context.Context, blocks []blocks.ROBlock, finalizedChildRoot [32]byte) error
 }
 
 // SlasherDatabase interface for persisting data related to detecting slashable offenses on Ethereum.

beacon-chain/node/node.go

@@ -318,6 +318,7 @@ func startBaseServices(cliCtx *cli.Context, beacon *BeaconNode, depositAddress s
 	}
 
 	beacon.BlobStorage.WarmCache()
+	beacon.DataColumnStorage.WarmCache()
 
 	log.Debugln("Starting Slashing DB")
 	if err := beacon.startSlasherDB(cliCtx, clearer); err != nil {
@@ -845,6 +846,7 @@ func (b *BeaconNode) registerInitialSyncService(complete chan struct{}) error {
 		ClockWaiter:         b.clockWaiter,
 		InitialSyncComplete: complete,
 		BlobStorage:         b.BlobStorage,
+		DataColumnStorage:   b.DataColumnStorage,
 	}, opts...)
 	return b.services.RegisterService(is)
 }
@@ -939,6 +941,7 @@ func (b *BeaconNode) registerRPCService(router *http.ServeMux) error {
 		FinalizationFetcher:       chainService,
 		BlockReceiver:             chainService,
 		BlobReceiver:              chainService,
+		DataColumnReceiver:        chainService,
 		AttestationReceiver:       chainService,
 		GenesisTimeFetcher:        chainService,
 		GenesisFetcher:            chainService,
@@ -966,6 +969,7 @@ func (b *BeaconNode) registerRPCService(router *http.ServeMux) error {
 		Router:                    router,
 		ClockWaiter:               b.clockWaiter,
 		BlobStorage:               b.BlobStorage,
+		DataColumnStorage:         b.DataColumnStorage,
 		TrackedValidatorsCache:    b.trackedValidatorsCache,
 		PayloadIDCache:            b.payloadIDCache,
 		LCStore:                   b.lcStore,

beacon-chain/p2p/BUILD.bazel

@@ -195,7 +195,6 @@ go_test(
         "@com_github_multiformats_go_multiaddr//:go_default_library",
         "@com_github_pkg_errors//:go_default_library",
         "@com_github_prysmaticlabs_go_bitfield//:go_default_library",
-        "@com_github_sirupsen_logrus//:go_default_library",
         "@com_github_sirupsen_logrus//hooks/test:go_default_library",
         "@org_golang_google_protobuf//proto:go_default_library",
     ],

beacon-chain/p2p/broadcaster.go

@@ -305,15 +305,15 @@ func (s *Service) BroadcastLightClientFinalityUpdate(ctx context.Context, update
 	return nil
 }
 
-// BroadcastDataColumn broadcasts a data column to the p2p network, the message is assumed to be
+// BroadcastDataColumnSidecar broadcasts a data column to the p2p network, the message is assumed to be
 // broadcasted to the current fork and to the input column subnet.
-func (s *Service) BroadcastDataColumn(
+func (s *Service) BroadcastDataColumnSidecar(
 	root [fieldparams.RootLength]byte,
 	dataColumnSubnet uint64,
 	dataColumnSidecar *ethpb.DataColumnSidecar,
 ) error {
 	// Add tracing to the function.
-	ctx, span := trace.StartSpan(s.ctx, "p2p.BroadcastDataColumn")
+	ctx, span := trace.StartSpan(s.ctx, "p2p.BroadcastDataColumnSidecar")
 	defer span.End()
 
 	// Ensure the data column sidecar is not nil.
@@ -330,12 +330,12 @@ func (s *Service) BroadcastDataColumn(
 	}
 
 	// Non-blocking broadcast, with attempts to discover a column subnet peer if none available.
-	go s.internalBroadcastDataColumn(ctx, root, dataColumnSubnet, dataColumnSidecar, forkDigest)
+	go s.internalBroadcastDataColumnSidecar(ctx, root, dataColumnSubnet, dataColumnSidecar, forkDigest)
 
 	return nil
 }
 
-func (s *Service) internalBroadcastDataColumn(
+func (s *Service) internalBroadcastDataColumnSidecar(
 	ctx context.Context,
 	root [fieldparams.RootLength]byte,
 	columnSubnet uint64,
@@ -343,7 +343,7 @@ func (s *Service) internalBroadcastDataColumn(
 	forkDigest [fieldparams.VersionLength]byte,
 ) {
 	// Add tracing to the function.
-	_, span := trace.StartSpan(ctx, "p2p.internalBroadcastDataColumn")
+	_, span := trace.StartSpan(ctx, "p2p.internalBroadcastDataColumnSidecar")
 	defer span.End()
 
 	// Increase the number of broadcast attempts.

beacon-chain/p2p/broadcaster_test.go

@@ -716,7 +716,7 @@ func TestService_BroadcastDataColumn(t *testing.T) {
 
 	// Attempt to broadcast nil object should fail.
 	var emptyRoot [fieldparams.RootLength]byte
-	err = service.BroadcastDataColumn(emptyRoot, subnet, nil)
+	err = service.BroadcastDataColumnSidecar(emptyRoot, subnet, nil)
 	require.ErrorContains(t, "attempted to broadcast nil", err)
 
 	// Subscribe to the topic.
@@ -727,7 +727,7 @@ func TestService_BroadcastDataColumn(t *testing.T) {
 	time.Sleep(50 * time.Millisecond)
 
 	// Broadcast to peers and wait.
-	err = service.BroadcastDataColumn(emptyRoot, subnet, sidecar)
+	err = service.BroadcastDataColumnSidecar(emptyRoot, subnet, sidecar)
 	require.NoError(t, err)
 
 	// Receive the message.

beacon-chain/p2p/custody.go

@@ -155,6 +155,7 @@ func (s *Service) custodyGroupCountFromPeerENR(pid peer.ID) uint64 {
 	log := log.WithFields(logrus.Fields{
 		"peerID":       pid,
 		"defaultValue": custodyRequirement,
+		"agent":        agentString(pid, s.Host()),
 	})
 
 	// Retrieve the ENR of the peer.

beacon-chain/p2p/custody_test.go

@@ -8,6 +8,7 @@ import (
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/peerdas"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/peers"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/peers/scorers"
+	testp2p "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/testing"
 	"github.com/OffchainLabs/prysm/v6/config/params"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/primitives"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/wrapper"
@@ -269,6 +270,7 @@ func TestCustodyGroupCountFromPeer(t *testing.T) {
 			service := &Service{
 				peers:    peers,
 				metaData: tc.metadata,
+				host:     testp2p.NewTestP2P(t).Host(),
 			}
 
 			// Retrieve the custody count from the remote peer.
@@ -329,6 +331,7 @@ func TestCustodyGroupCountFromPeerENR(t *testing.T) {
 
 			service := &Service{
 				peers: peers,
+				host:  testp2p.NewTestP2P(t).Host(),
 			}
 
 			actual := service.custodyGroupCountFromPeerENR(pid)

beacon-chain/p2p/discovery.go

@@ -443,20 +443,27 @@ func (s *Service) findPeers(ctx context.Context, missingPeerCount uint) ([]*enod
 			return peersToDial, ctx.Err()
 		}
 
-		// Skip peer not matching the filter.
 		node := iterator.Node()
-		if !s.filterPeer(node) {
-			continue
-		}
 
 		// Remove duplicates, keeping the node with higher seq.
 		existing, ok := nodeByNodeID[node.ID()]
-		if ok && existing.Seq() > node.Seq() {
+		if ok && existing.Seq() >= node.Seq() {
+			continue // keep existing and skip.
+		}
+
+		// Treat nodes that exist in nodeByNodeID with higher seq numbers as new peers
+		// Skip peer not matching the filter.
+		if !s.filterPeer(node) {
+			if ok {
+				// this means the existing peer with the lower sequence number is no longer valid
+				delete(nodeByNodeID, existing.ID())
+				missingPeerCount++
+			}
 			continue
 		}
-		nodeByNodeID[node.ID()] = node
 
 		// We found a new peer. Decrease the missing peer count.
+		nodeByNodeID[node.ID()] = node
 		missingPeerCount--
 	}
 
@@ -677,7 +684,7 @@ func (s *Service) filterPeer(node *enode.Node) bool {
 
 	peerData, multiAddrs, err := convertToAddrInfo(node)
 	if err != nil {
-		log.WithError(err).Debug("Could not convert to peer data")
+		log.WithError(err).WithField("node", node.String()).Debug("Could not convert to peer data")
 		return false
 	}
 
@@ -844,7 +851,7 @@ func convertToMultiAddr(nodes []*enode.Node) []ma.Multiaddr {
 func convertToAddrInfo(node *enode.Node) (*peer.AddrInfo, []ma.Multiaddr, error) {
 	multiAddrs, err := retrieveMultiAddrsFromNode(node)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, errors.Wrap(err, "retrieve multiaddrs from node")
 	}
 
 	if len(multiAddrs) == 0 {

beacon-chain/p2p/discovery_test.go

@@ -1,9 +1,11 @@
 package p2p
 
 import (
+	"bytes"
 	"context"
 	"crypto/ecdsa"
 	"crypto/rand"
+	"crypto/sha256"
 	"fmt"
 	mathRand "math/rand"
 	"net"
@@ -58,6 +60,81 @@ func createAddrAndPrivKey(t *testing.T) (net.IP, *ecdsa.PrivateKey) {
 	return ipAddr, pkey
 }
 
+// createTestNodeWithID creates a LocalNode for testing with deterministic private key
+// This is needed for deduplication tests where we need the same node ID across different sequence numbers
+func createTestNodeWithID(t *testing.T, id string) *enode.LocalNode {
+	// Create a deterministic reader based on the ID for consistent key generation
+	h := sha256.New()
+	h.Write([]byte(id))
+	seedBytes := h.Sum(nil)
+
+	// Create a deterministic reader using the seed
+	deterministicReader := bytes.NewReader(seedBytes)
+
+	// Generate the private key using the same approach as the production code
+	privKey, _, err := crypto.GenerateSecp256k1Key(deterministicReader)
+	require.NoError(t, err)
+
+	// Convert to ECDSA private key for enode usage
+	ecdsaPrivKey, err := ecdsaprysm.ConvertFromInterfacePrivKey(privKey)
+	require.NoError(t, err)
+
+	db, err := enode.OpenDB("")
+	require.NoError(t, err)
+	t.Cleanup(func() { db.Close() })
+
+	localNode := enode.NewLocalNode(db, ecdsaPrivKey)
+
+	// Set basic properties
+	localNode.SetStaticIP(net.ParseIP("127.0.0.1"))
+	localNode.Set(enr.TCP(3000))
+	localNode.Set(enr.UDP(3000))
+	localNode.Set(enr.WithEntry(eth2EnrKey, make([]byte, 16)))
+
+	return localNode
+}
+
+// createTestNodeRandom creates a LocalNode for testing using the existing createAddrAndPrivKey function
+func createTestNodeRandom(t *testing.T) *enode.LocalNode {
+	_, privKey := createAddrAndPrivKey(t)
+
+	db, err := enode.OpenDB("")
+	require.NoError(t, err)
+	t.Cleanup(func() { db.Close() })
+
+	localNode := enode.NewLocalNode(db, privKey)
+
+	// Set basic properties
+	localNode.SetStaticIP(net.ParseIP("127.0.0.1"))
+	localNode.Set(enr.TCP(3000))
+	localNode.Set(enr.UDP(3000))
+	localNode.Set(enr.WithEntry(eth2EnrKey, make([]byte, 16)))
+
+	return localNode
+}
+
+// setNodeSeq updates a LocalNode to have the specified sequence number
+func setNodeSeq(localNode *enode.LocalNode, seq uint64) {
+	// Force set the sequence number - we need to update the record seq-1 times
+	// because it starts at 1
+	currentSeq := localNode.Node().Seq()
+	for currentSeq < seq {
+		localNode.Set(enr.WithEntry("dummy", currentSeq))
+		currentSeq++
+	}
+}
+
+// setNodeSubnets sets the attestation subnets for a LocalNode
+func setNodeSubnets(localNode *enode.LocalNode, attSubnets []uint64) {
+	if len(attSubnets) > 0 {
+		bitV := bitfield.NewBitvector64()
+		for _, subnet := range attSubnets {
+			bitV.SetBitAt(subnet, true)
+		}
+		localNode.Set(enr.WithEntry(attSubnetEnrKey, &bitV))
+	}
+}
+
 func TestCreateListener(t *testing.T) {
 	port := 1024
 	ipAddr, pkey := createAddrAndPrivKey(t)
@@ -241,7 +318,7 @@ func TestCreateLocalNode(t *testing.T) {
 
 			// Check fork is set.
 			fork := new([]byte)
-			require.NoError(t, localNode.Node().Record().Load(enr.WithEntry(eth2ENRKey, fork)))
+			require.NoError(t, localNode.Node().Record().Load(enr.WithEntry(eth2EnrKey, fork)))
 			require.NotEmpty(t, *fork)
 
 			// Check att subnets.
@@ -492,7 +569,7 @@ func TestMultipleDiscoveryAddresses(t *testing.T) {
 	node := enode.NewLocalNode(db, key)
 	node.Set(enr.IPv4{127, 0, 0, 1})
 	node.Set(enr.IPv6{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68})
-	s := &Service{dv5Listener: mockListener{localNode: node}}
+	s := &Service{dv5Listener: testp2p.NewMockListener(node, nil)}
 
 	multiAddresses, err := s.DiscoveryAddresses()
 	require.NoError(t, err)
@@ -517,7 +594,7 @@ func TestDiscoveryV5_SeqNumber(t *testing.T) {
 	node := enode.NewLocalNode(db, key)
 	node.Set(enr.IPv4{127, 0, 0, 1})
 	currentSeq := node.Seq()
-	s := &Service{dv5Listener: mockListener{localNode: node}}
+	s := &Service{dv5Listener: testp2p.NewMockListener(node, nil)}
 	_, err = s.DiscoveryAddresses()
 	require.NoError(t, err)
 	newSeq := node.Seq()
@@ -529,7 +606,7 @@ func TestDiscoveryV5_SeqNumber(t *testing.T) {
 	nodeTwo.Set(enr.IPv6{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68})
 	seqTwo := nodeTwo.Seq()
 	assert.NotEqual(t, seqTwo, newSeq)
-	sTwo := &Service{dv5Listener: mockListener{localNode: nodeTwo}}
+	sTwo := &Service{dv5Listener: testp2p.NewMockListener(nodeTwo, nil)}
 	_, err = sTwo.DiscoveryAddresses()
 	require.NoError(t, err)
 	assert.Equal(t, seqTwo+1, nodeTwo.Seq())
@@ -886,3 +963,289 @@ func TestRefreshPersistentSubnets(t *testing.T) {
 	// Reset the config.
 	params.OverrideBeaconConfig(defaultCfg)
 }
+
+func TestFindPeers_NodeDeduplication(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	cache.SubnetIDs.EmptyAllCaches()
+	defer cache.SubnetIDs.EmptyAllCaches()
+
+	ctx := t.Context()
+
+	// Create LocalNodes and manipulate sequence numbers
+	localNode1 := createTestNodeWithID(t, "node1")
+	localNode2 := createTestNodeWithID(t, "node2")
+	localNode3 := createTestNodeWithID(t, "node3")
+
+	// Create different sequence versions of node1
+	setNodeSeq(localNode1, 1)
+	node1_seq1 := localNode1.Node()
+	setNodeSeq(localNode1, 2)
+	node1_seq2 := localNode1.Node() // Same ID, higher seq
+	setNodeSeq(localNode1, 3)
+	node1_seq3 := localNode1.Node() // Same ID, even higher seq
+
+	// Other nodes with seq 1
+	node2_seq1 := localNode2.Node()
+	node3_seq1 := localNode3.Node()
+
+	tests := []struct {
+		name          string
+		nodes         []*enode.Node
+		missingPeers  uint
+		expectedCount int
+		description   string
+		eval          func(t *testing.T, result []*enode.Node)
+	}{
+		{
+			name: "No duplicates - all unique nodes",
+			nodes: []*enode.Node{
+				node2_seq1,
+				node3_seq1,
+			},
+			missingPeers:  2,
+			expectedCount: 2,
+			description:   "Should return all unique nodes without deduplication",
+			eval:          nil, // No special validation needed
+		},
+		{
+			name: "Duplicate with lower seq comes first - should replace",
+			nodes: []*enode.Node{
+				node1_seq1,
+				node1_seq2, // Higher seq, should replace
+				node2_seq1, // Different node added after duplicates are processed
+			},
+			missingPeers:  2, // Need 2 peers so we process all nodes
+			expectedCount: 2, // Should get node1 (with higher seq) and node2
+			description:   "Should keep node with higher sequence number when duplicate found",
+			eval: func(t *testing.T, result []*enode.Node) {
+				// Should have node2 and node1 with higher seq (node1_seq2)
+				foundNode1WithHigherSeq := false
+				for _, node := range result {
+					if node.ID() == node1_seq2.ID() {
+						require.Equal(t, node1_seq2.Seq(), node.Seq(), "Node1 should have higher seq")
+						foundNode1WithHigherSeq = true
+					}
+				}
+				require.Equal(t, true, foundNode1WithHigherSeq, "Should have node1 with higher seq")
+			},
+		},
+		{
+			name: "Duplicate with higher seq comes first - should keep existing",
+			nodes: []*enode.Node{
+				node1_seq3, // Higher seq
+				node1_seq2, // Lower seq, should be skipped (continue branch)
+				node1_seq1, // Even lower seq, should also be skipped (continue branch)
+				node2_seq1, // Different node added after duplicates are processed
+			},
+			missingPeers:  2,
+			expectedCount: 2,
+			description:   "Should keep existing node when it has higher sequence number and skip all lower seq duplicates",
+			eval: func(t *testing.T, result []*enode.Node) {
+				// Should have kept the node with highest seq (node1_seq3)
+				foundNode1WithHigherSeq := false
+				for _, node := range result {
+					if node.ID() == node1_seq3.ID() {
+						require.Equal(t, node1_seq3.Seq(), node.Seq(), "Node1 should have highest seq")
+						foundNode1WithHigherSeq = true
+					}
+				}
+				require.Equal(t, true, foundNode1WithHigherSeq, "Should have node1 with highest seq")
+			},
+		},
+		{
+			name: "Multiple duplicates with increasing seq",
+			nodes: []*enode.Node{
+				node1_seq1,
+				node1_seq2, // Should replace seq1
+				node1_seq3, // Should replace seq2
+				node2_seq1, // Different node added after duplicates are processed
+			},
+			missingPeers:  2,
+			expectedCount: 2,
+			description:   "Should keep updating to highest sequence number",
+			eval: func(t *testing.T, result []*enode.Node) {
+				// Should have the node with highest seq (node1_seq3)
+				foundNode1WithHigherSeq := false
+				for _, node := range result {
+					if node.ID() == node1_seq3.ID() {
+						require.Equal(t, node1_seq3.Seq(), node.Seq(), "Node1 should have highest seq")
+						foundNode1WithHigherSeq = true
+					}
+				}
+				require.Equal(t, true, foundNode1WithHigherSeq, "Should have node1 with highest seq")
+			},
+		},
+		{
+			name: "Duplicate with equal seq comes after - should skip",
+			nodes: []*enode.Node{
+				node1_seq2, // First occurrence
+				node1_seq2, // Same exact node instance, should be skipped (continue branch for >= case)
+				node2_seq1, // Different node
+			},
+			missingPeers:  2,
+			expectedCount: 2,
+			description:   "Should skip duplicate with equal sequence number",
+			eval: func(t *testing.T, result []*enode.Node) {
+				// Should have exactly one instance of node1_seq2 and one instance of node2_seq1
+				foundNode1 := false
+				foundNode2 := false
+				for _, node := range result {
+					if node.ID() == node1_seq2.ID() {
+						require.Equal(t, node1_seq2.Seq(), node.Seq(), "Node1 should have the expected seq")
+						require.Equal(t, false, foundNode1, "Should have only one instance of node1") // Ensure no duplicates
+						foundNode1 = true
+					}
+					if node.ID() == node2_seq1.ID() {
+						foundNode2 = true
+					}
+				}
+				require.Equal(t, true, foundNode1, "Should have node1")
+				require.Equal(t, true, foundNode2, "Should have node2")
+			},
+		},
+		{
+			name: "Mix of unique and duplicate nodes",
+			nodes: []*enode.Node{
+				node1_seq1,
+				node2_seq1,
+				node1_seq2, // Should replace node1_seq1
+				node3_seq1,
+				node1_seq3, // Should replace node1_seq2
+			},
+			missingPeers:  3,
+			expectedCount: 3,
+			description:   "Should handle mix of unique nodes and duplicates correctly",
+			eval:          nil, // Basic count validation is sufficient
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fakePeer := testp2p.NewTestP2P(t)
+
+			s := &Service{
+				cfg: &Config{
+					MaxPeers: 30,
+				},
+				genesisValidatorsRoot: bytesutil.PadTo([]byte{'A'}, 32),
+				peers: peers.NewStatus(ctx, &peers.StatusConfig{
+					PeerLimit:    30,
+					ScorerParams: &scorers.Config{},
+				}),
+				host: fakePeer.BHost,
+			}
+
+			localNode := createTestNodeRandom(t)
+			mockIter := testp2p.NewMockIterator(tt.nodes)
+			s.dv5Listener = testp2p.NewMockListener(localNode, mockIter)
+
+			ctxWithTimeout, cancel := context.WithTimeout(ctx, 1*time.Second)
+			defer cancel()
+
+			result, err := s.findPeers(ctxWithTimeout, tt.missingPeers)
+
+			require.NoError(t, err, tt.description)
+			require.Equal(t, tt.expectedCount, len(result), tt.description)
+
+			if tt.eval != nil {
+				tt.eval(t, result)
+			}
+		})
+	}
+}
+
+// callbackIterator allows us to execute callbacks at specific points during iteration
+type callbackIterator struct {
+	nodes     []*enode.Node
+	index     int
+	callbacks map[int]func() // map from index to callback function
+}
+
+func (c *callbackIterator) Next() bool {
+	// Execute callback before checking if we can continue (if one exists)
+	if callback, exists := c.callbacks[c.index]; exists {
+		callback()
+	}
+
+	return c.index < len(c.nodes)
+}
+
+func (c *callbackIterator) Node() *enode.Node {
+	if c.index >= len(c.nodes) {
+		return nil
+	}
+
+	node := c.nodes[c.index]
+	c.index++
+	return node
+}
+
+func (c *callbackIterator) Close() {
+	// Nothing to clean up for this simple implementation
+}
+
+func TestFindPeers_received_bad_existing_node(t *testing.T) {
+	// This test successfully triggers delete(nodeByNodeID, node.ID()) in subnets.go by:
+	// 1. Processing node1_seq1 first (passes filterPeer, gets added to map
+	// 2. Callback marks peer as bad before processing node1_seq2"
+	// 3. Processing node1_seq2 (fails filterPeer, triggers delete since ok=true
+	params.SetupTestConfigCleanup(t)
+	cache.SubnetIDs.EmptyAllCaches()
+	defer cache.SubnetIDs.EmptyAllCaches()
+
+	// Create LocalNode with same ID but different sequences
+	localNode1 := createTestNodeWithID(t, "testnode")
+	node1_seq1 := localNode1.Node() // Get current node
+	currentSeq := node1_seq1.Seq()
+	setNodeSeq(localNode1, currentSeq+1) // Increment sequence by 1
+	node1_seq2 := localNode1.Node()      // This should have higher seq
+
+	// Additional node to ensure we have enough peers to process
+	localNode2 := createTestNodeWithID(t, "othernode")
+	node2 := localNode2.Node()
+
+	fakePeer := testp2p.NewTestP2P(t)
+
+	service := &Service{
+		cfg: &Config{
+			MaxPeers: 30,
+		},
+		genesisValidatorsRoot: bytesutil.PadTo([]byte{'A'}, 32),
+		peers: peers.NewStatus(t.Context(), &peers.StatusConfig{
+			PeerLimit:    30,
+			ScorerParams: &scorers.Config{},
+		}),
+		host: fakePeer.BHost,
+	}
+
+	// Create iterator with callback that marks peer as bad before processing node1_seq2
+	iter := &callbackIterator{
+		nodes: []*enode.Node{node1_seq1, node1_seq2, node2},
+		index: 0,
+		callbacks: map[int]func(){
+			1: func() { // Before processing node1_seq2 (index 1)
+				// Mark peer as bad before processing node1_seq2
+				peerData, _, _ := convertToAddrInfo(node1_seq2)
+				if peerData != nil {
+					service.peers.Add(node1_seq2.Record(), peerData.ID, nil, network.DirUnknown)
+					// Mark as bad peer - need enough increments to exceed threshold (6)
+					for i := 0; i < 10; i++ {
+						service.peers.Scorers().BadResponsesScorer().Increment(peerData.ID)
+					}
+				}
+			},
+		},
+	}
+
+	localNode := createTestNodeRandom(t)
+	service.dv5Listener = testp2p.NewMockListener(localNode, iter)
+
+	// Run findPeers - node1_seq1 gets processed first, then callback marks peer bad, then node1_seq2 fails
+	ctxWithTimeout, cancel := context.WithTimeout(t.Context(), 1*time.Second)
+	defer cancel()
+
+	result, err := service.findPeers(ctxWithTimeout, 3)
+
+	require.NoError(t, err)
+	require.Equal(t, 1, len(result))
+}

beacon-chain/p2p/fork.go

@@ -13,10 +13,17 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
-var errEth2ENRDigestMismatch = errors.New("fork digest of peer does not match local value")
+var (
+	errForkScheduleMismatch  = errors.New("peer fork schedule incompatible")
+	errCurrentDigestMismatch = errors.Wrap(errForkScheduleMismatch, "current_fork_digest mismatch")
+	errNextVersionMismatch   = errors.Wrap(errForkScheduleMismatch, "next_fork_version mismatch")
+	errNextDigestMismatch    = errors.Wrap(errForkScheduleMismatch, "nfd (next fork digest) mismatch")
+)
 
-// ENR key used for Ethereum consensus-related fork data.
-var eth2ENRKey = params.BeaconNetworkConfig().ETH2Key
+const (
+	eth2EnrKey = "eth2" // The `eth2` ENR entry advertizes the node's view of the fork schedule with an ssz-encoded ENRForkID value.
+	nfdEnrKey  = "nfd"  // The `nfd` ENR entry separately advertizes the "next fork digest" aspect of the fork schedule.
+)
 
 // ForkDigest returns the current fork digest of
 // the node according to the local clock.
@@ -33,44 +40,86 @@ func (s *Service) currentForkDigest() ([4]byte, error) {
 // Compares fork ENRs between an incoming peer's record and our node's
 // local record values for current and next fork version/epoch.
 func compareForkENR(self, peer *enr.Record) error {
-	peerForkENR, err := forkEntry(peer)
+	peerEntry, err := forkEntry(peer)
 	if err != nil {
 		return err
 	}
-	currentForkENR, err := forkEntry(self)
+	selfEntry, err := forkEntry(self)
 	if err != nil {
 		return err
 	}
-	enrString, err := SerializeENR(peer)
+	peerString, err := SerializeENR(peer)
 	if err != nil {
 		return err
 	}
 	// Clients SHOULD connect to peers with current_fork_digest, next_fork_version,
 	// and next_fork_epoch that match local values.
-	if !bytes.Equal(peerForkENR.CurrentForkDigest, currentForkENR.CurrentForkDigest) {
-		return errors.Wrapf(errEth2ENRDigestMismatch,
+	if !bytes.Equal(peerEntry.CurrentForkDigest, selfEntry.CurrentForkDigest) {
+		return errors.Wrapf(errCurrentDigestMismatch,
 			"fork digest of peer with ENR %s: %v, does not match local value: %v",
-			enrString,
-			peerForkENR.CurrentForkDigest,
-			currentForkENR.CurrentForkDigest,
+			peerString,
+			peerEntry.CurrentForkDigest,
+			selfEntry.CurrentForkDigest,
 		)
 	}
+
 	// Clients MAY connect to peers with the same current_fork_version but a
 	// different next_fork_version/next_fork_epoch. Unless ENRForkID is manually
 	// updated to matching prior to the earlier next_fork_epoch of the two clients,
 	// these type of connecting clients will be unable to successfully interact
 	// starting at the earlier next_fork_epoch.
-	if peerForkENR.NextForkEpoch != currentForkENR.NextForkEpoch {
+	if peerEntry.NextForkEpoch != selfEntry.NextForkEpoch {
 		log.WithFields(logrus.Fields{
-			"peerNextForkEpoch": peerForkENR.NextForkEpoch,
-			"peerENR":           enrString,
+			"peerNextForkEpoch":   peerEntry.NextForkEpoch,
+			"peerNextForkVersion": peerEntry.NextForkVersion,
+			"peerENR":             peerString,
 		}).Trace("Peer matches fork digest but has different next fork epoch")
+		// We allow the connection because we have a different view of the next fork epoch. This
+		// could be due to peers that have no upgraded ahead of a fork or BPO schedule change, so
+		// we allow the connection to continue until the fork boundary.
+		return nil
 	}
-	if !bytes.Equal(peerForkENR.NextForkVersion, currentForkENR.NextForkVersion) {
-		log.WithFields(logrus.Fields{
-			"peerNextForkVersion": peerForkENR.NextForkVersion,
-			"peerENR":             enrString,
-		}).Trace("Peer matches fork digest but has different next fork version")
+
+	// Since we agree on the next fork epoch, we require next fork version to also be in agreement.
+	if !bytes.Equal(peerEntry.NextForkVersion, selfEntry.NextForkVersion) {
+		return errors.Wrapf(errNextVersionMismatch,
+			"next fork version of peer with ENR %s: %#x, does not match local value: %#x",
+			peerString, peerEntry.NextForkVersion, selfEntry.NextForkVersion)
+	}
+
+	// Fulu adds the following to the spec:
+	// ---
+	// A new entry is added to the ENR under the key nfd, short for next fork digest. This entry
+	// communicates the digest of the next scheduled fork, regardless of whether it is a regular
+	// or a Blob-Parameters-Only fork. This new entry MUST be added once FULU_FORK_EPOCH is assigned
+	// any value other than FAR_FUTURE_EPOCH. Adding this entry prior to the Fulu fork will not
+	// impact peering as nodes will ignore unknown ENR entries and nfd mismatches do not cause
+	// disconnects.
+	// When discovering and interfacing with peers, nodes MUST evaluate nfd alongside their existing
+	// consideration of the ENRForkID::next_* fields under the eth2 key, to form a more accurate
+	// view of the peer's intended next fork for the purposes of sustained peering. If there is a
+	// mismatch, the node MUST NOT disconnect before the fork boundary, but it MAY disconnect
+	// at/after the fork boundary.
+
+	// Nodes unprepared to follow the Fulu fork will be unaware of nfd entries. However, their
+	// existing comparison of eth2 entries (concretely next_fork_epoch) is sufficient to detect
+	// upcoming divergence.
+	// ---
+
+	// Because this is a new in-bound connection, we lean into the pre-fulu point that clients
+	// MAY connect to peers with the same current_fork_version but a different
+	// next_fork_version/next_fork_epoch, which implies we can chose to not connect to them when these
+	// don't match.
+	//
+	// Given that the next_fork_epoch matches, we will require the next_fork_digest to match.
+	if !params.FuluEnabled() {
+		return nil
+	}
+	peerNFD, selfNFD := nfd(peer), nfd(self)
+	if peerNFD != selfNFD {
+		return errors.Wrapf(errNextDigestMismatch,
+			"next fork digest of peer with ENR %s: %v, does not match local value: %v",
+			peerString, peerNFD, selfNFD)
 	}
 	return nil
 }
@@ -81,16 +130,28 @@ func updateENR(node *enode.LocalNode, entry, next params.NetworkScheduleEntry) e
 		NextForkVersion:   next.ForkVersion[:],
 		NextForkEpoch:     next.Epoch,
 	}
-	log.
-		WithField("CurrentForkDigest", fmt.Sprintf("%#x", enrForkID.CurrentForkDigest)).
-		WithField("NextForkVersion", fmt.Sprintf("%#x", enrForkID.NextForkVersion)).
-		WithField("NextForkEpoch", fmt.Sprintf("%d", enrForkID.NextForkEpoch)).
-		Info("Updating ENR Fork ID")
+	if entry.Epoch == next.Epoch {
+		enrForkID.NextForkEpoch = params.BeaconConfig().FarFutureEpoch
+	}
+	logFields := logrus.Fields{
+		"CurrentForkDigest": fmt.Sprintf("%#x", enrForkID.CurrentForkDigest),
+		"NextForkVersion":   fmt.Sprintf("%#x", enrForkID.NextForkVersion),
+		"NextForkEpoch":     fmt.Sprintf("%d", enrForkID.NextForkEpoch),
+	}
+	if params.BeaconConfig().FuluForkEpoch != params.BeaconConfig().FarFutureEpoch {
+		if entry.ForkDigest == next.ForkDigest {
+			node.Set(enr.WithEntry(nfdEnrKey, make([]byte, len(next.ForkDigest))))
+		} else {
+			node.Set(enr.WithEntry(nfdEnrKey, next.ForkDigest[:]))
+		}
+		logFields["NextForkDigest"] = fmt.Sprintf("%#x", next.ForkDigest)
+	}
+	log.WithFields(logFields).Info("Updating ENR Fork ID")
 	enc, err := enrForkID.MarshalSSZ()
 	if err != nil {
 		return err
 	}
-	forkEntry := enr.WithEntry(eth2ENRKey, enc)
+	forkEntry := enr.WithEntry(eth2EnrKey, enc)
 	node.Set(forkEntry)
 	return nil
 }
@@ -99,7 +160,7 @@ func updateENR(node *enode.LocalNode, entry, next params.NetworkScheduleEntry) e
 // under the Ethereum consensus EnrKey
 func forkEntry(record *enr.Record) (*pb.ENRForkID, error) {
 	sszEncodedForkEntry := make([]byte, 16)
-	entry := enr.WithEntry(eth2ENRKey, &sszEncodedForkEntry)
+	entry := enr.WithEntry(eth2EnrKey, &sszEncodedForkEntry)
 	err := record.Load(entry)
 	if err != nil {
 		return nil, err
@@ -110,3 +171,15 @@ func forkEntry(record *enr.Record) (*pb.ENRForkID, error) {
 	}
 	return forkEntry, nil
 }
+
+// nfd retrieves the value of the `nfd` ("next fork digest") key from an ENR record.
+func nfd(record *enr.Record) [4]byte {
+	digest := [4]byte{}
+	entry := enr.WithEntry(nfdEnrKey, &digest)
+	if err := record.Load(entry); err != nil {
+		// Treat a missing nfd entry as an empty digest.
+		// We do this to avoid errors when checking peers that have not upgraded for fulu.
+		return [4]byte{}
+	}
+	return digest
+}

beacon-chain/p2p/fork_test.go

@@ -16,14 +16,12 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/p2p/enr"
-	"github.com/sirupsen/logrus"
-	logTest "github.com/sirupsen/logrus/hooks/test"
 )
 
 func TestCompareForkENR(t *testing.T) {
 	params.SetupTestConfigCleanup(t)
+	params.BeaconConfig().FuluForkEpoch = params.BeaconConfig().ElectraForkEpoch + 4096
 	params.BeaconConfig().InitializeForkSchedule()
-	logrus.SetLevel(logrus.TraceLevel)
 
 	db, err := enode.OpenDB("")
 	assert.NoError(t, err)
@@ -61,10 +59,10 @@ func TestCompareForkENR(t *testing.T) {
 				require.NoError(t, updateENR(peer, currentCopy, next))
 				return peer.Node()
 			},
-			expectErr: errEth2ENRDigestMismatch,
+			expectErr: errCurrentDigestMismatch,
 		},
 		{
-			name: "next fork version mismatch",
+			name: "next_fork_epoch match, next_fork_version mismatch",
 			node: func(t *testing.T) *enode.Node {
 				// Create a peer with the same current fork digest and next fork version/epoch.
 				peer := enode.NewLocalNode(db, k)
@@ -75,25 +73,44 @@ func TestCompareForkENR(t *testing.T) {
 				require.NoError(t, updateENR(peer, current, nextCopy))
 				return peer.Node()
 			},
-			expectLog: "Peer matches fork digest but has different next fork version",
+			expectErr: errNextVersionMismatch,
 		},
 		{
-			name: "next fork epoch mismatch",
+			name: "next fork epoch mismatch, next fork digest mismatch",
 			node: func(t *testing.T) *enode.Node {
 				// Create a peer with the same current fork digest and next fork version/epoch.
 				peer := enode.NewLocalNode(db, k)
 				nextCopy := next
+				// next epoch does not match, and neither does the next fork digest.
 				nextCopy.Epoch = nextCopy.Epoch + 1
+				nfd := [4]byte{0xFF, 0xFF, 0xFF, 0xFF}
+				require.NotEqual(t, next.ForkDigest, nfd)
+				//peer.Set(enr.WithEntry(nfdEnrKey, nfd[:]))
+				nextCopy.ForkDigest = nfd
 				require.NoError(t, updateENR(peer, current, nextCopy))
 				return peer.Node()
 			},
-			expectLog: "Peer matches fork digest but has different next fork epoch",
+			// no error because we allow a different next fork version / digest if the next fork epoch does not match
+		},
+		{
+			name: "next fork epoch -match-, next fork digest mismatch",
+			node: func(t *testing.T) *enode.Node {
+				peer := enode.NewLocalNode(db, k)
+				nextCopy := next
+				nfd := [4]byte{0xFF, 0xFF, 0xFF, 0xFF}
+				// next epoch *does match*, but the next fork digest doesn't - so we should get an error.
+				require.NotEqual(t, next.ForkDigest, nfd)
+				nextCopy.ForkDigest = nfd
+				//peer.Set(enr.WithEntry(nfdEnrKey, nfd[:]))
+				require.NoError(t, updateENR(peer, current, nextCopy))
+				return peer.Node()
+			},
+			expectErr: errNextDigestMismatch,
 		},
 	}
 
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {
-			hook := logTest.NewGlobal()
 			peer := c.node(t)
 			err := compareForkENR(self.Node().Record(), peer.Record())
 			if c.expectErr != nil {
@@ -101,13 +118,27 @@ func TestCompareForkENR(t *testing.T) {
 			} else {
 				require.NoError(t, err, "Expected no error comparing fork ENRs")
 			}
-			if c.expectLog != "" {
-				require.LogsContain(t, hook, c.expectLog, "Expected log message not found")
-			}
 		})
 	}
 }
 
+func TestNfdSetAndLoad(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	params.BeaconConfig().FuluForkEpoch = params.BeaconConfig().ElectraForkEpoch + 4096
+	params.BeaconConfig().InitializeForkSchedule()
+	db, err := enode.OpenDB("")
+	assert.NoError(t, err)
+	_, k := createAddrAndPrivKey(t)
+	clock := startup.NewClock(time.Now(), params.BeaconConfig().GenesisValidatorsRoot)
+	current := params.GetNetworkScheduleEntry(clock.CurrentEpoch())
+	next := params.NextNetworkScheduleEntry(clock.CurrentEpoch())
+	next.ForkDigest = [4]byte{0xFF, 0xFF, 0xFF, 0xFF} // Ensure a unique digest for testing.
+	self := enode.NewLocalNode(db, k)
+	require.NoError(t, updateENR(self, current, next))
+	n := nfd(self.Node().Record())
+	assert.Equal(t, next.ForkDigest, n, "Expected nfd to match next fork digest")
+}
+
 func TestDiscv5_AddRetrieveForkEntryENR(t *testing.T) {
 	params.SetupTestConfigCleanup(t)
 	params.BeaconConfig().InitializeForkSchedule()
@@ -122,7 +153,7 @@ func TestDiscv5_AddRetrieveForkEntryENR(t *testing.T) {
 	}
 	enc, err := enrForkID.MarshalSSZ()
 	require.NoError(t, err)
-	entry := enr.WithEntry(eth2ENRKey, enc)
+	entry := enr.WithEntry(eth2EnrKey, enc)
 	temp := t.TempDir()
 	randNum := rand.Int()
 	tempPath := path.Join(temp, strconv.Itoa(randNum))
@@ -177,3 +208,111 @@ func TestAddForkEntry_NextForkVersion(t *testing.T) {
 		"Wanted Next Fork Version to be equal to last entry in schedule")
 
 }
+
+func TestUpdateENR_FuluForkDigest(t *testing.T) {
+	setupTest := func(t *testing.T, fuluEnabled bool) (*enode.LocalNode, func()) {
+		params.SetupTestConfigCleanup(t)
+
+		cfg := params.BeaconConfig().Copy()
+		if fuluEnabled {
+			cfg.FuluForkEpoch = 100
+		} else {
+			cfg.FuluForkEpoch = cfg.FarFutureEpoch
+		}
+		cfg.FuluForkVersion = []byte{5, 0, 0, 0}
+		params.OverrideBeaconConfig(cfg)
+		cfg.InitializeForkSchedule()
+
+		pkey, err := privKey(&Config{DataDir: t.TempDir()})
+		require.NoError(t, err, "Could not get private key")
+		db, err := enode.OpenDB("")
+		require.NoError(t, err)
+
+		localNode := enode.NewLocalNode(db, pkey)
+		cleanup := func() {
+			db.Close()
+		}
+
+		return localNode, cleanup
+	}
+
+	tests := []struct {
+		name         string
+		fuluEnabled  bool
+		currentEntry params.NetworkScheduleEntry
+		nextEntry    params.NetworkScheduleEntry
+		validateNFD  func(t *testing.T, localNode *enode.LocalNode, nextEntry params.NetworkScheduleEntry)
+	}{
+		{
+			name:        "different digests sets nfd to next digest",
+			fuluEnabled: true,
+			currentEntry: params.NetworkScheduleEntry{
+				Epoch:       50,
+				ForkDigest:  [4]byte{1, 2, 3, 4},
+				ForkVersion: [4]byte{1, 0, 0, 0},
+			},
+			nextEntry: params.NetworkScheduleEntry{
+				Epoch:       100,
+				ForkDigest:  [4]byte{5, 6, 7, 8}, // Different from current
+				ForkVersion: [4]byte{2, 0, 0, 0},
+			},
+			validateNFD: func(t *testing.T, localNode *enode.LocalNode, nextEntry params.NetworkScheduleEntry) {
+				var nfdValue []byte
+				err := localNode.Node().Record().Load(enr.WithEntry(nfdEnrKey, &nfdValue))
+				require.NoError(t, err)
+				assert.DeepEqual(t, nextEntry.ForkDigest[:], nfdValue, "nfd entry should equal next fork digest")
+			},
+		},
+		{
+			name:        "same digests sets nfd to empty",
+			fuluEnabled: true,
+			currentEntry: params.NetworkScheduleEntry{
+				Epoch:       50,
+				ForkDigest:  [4]byte{1, 2, 3, 4},
+				ForkVersion: [4]byte{1, 0, 0, 0},
+			},
+			nextEntry: params.NetworkScheduleEntry{
+				Epoch:       100,
+				ForkDigest:  [4]byte{1, 2, 3, 4}, // Same as current
+				ForkVersion: [4]byte{2, 0, 0, 0},
+			},
+			validateNFD: func(t *testing.T, localNode *enode.LocalNode, nextEntry params.NetworkScheduleEntry) {
+				var nfdValue []byte
+				err := localNode.Node().Record().Load(enr.WithEntry(nfdEnrKey, &nfdValue))
+				require.NoError(t, err)
+				assert.DeepEqual(t, make([]byte, len(nextEntry.ForkDigest)), nfdValue, "nfd entry should be empty bytes when digests are same")
+			},
+		},
+		{
+			name:        "fulu disabled does not add nfd field",
+			fuluEnabled: false,
+			currentEntry: params.NetworkScheduleEntry{
+				Epoch:       50,
+				ForkDigest:  [4]byte{1, 2, 3, 4},
+				ForkVersion: [4]byte{1, 0, 0, 0},
+			},
+			nextEntry: params.NetworkScheduleEntry{
+				Epoch:       100,
+				ForkDigest:  [4]byte{5, 6, 7, 8}, // Different from current
+				ForkVersion: [4]byte{2, 0, 0, 0},
+			},
+			validateNFD: func(t *testing.T, localNode *enode.LocalNode, nextEntry params.NetworkScheduleEntry) {
+				var nfdValue []byte
+				err := localNode.Node().Record().Load(enr.WithEntry(nfdEnrKey, &nfdValue))
+				require.ErrorContains(t, "missing ENR key", err, "nfd field should not be present when Fulu fork is disabled")
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			localNode, cleanup := setupTest(t, tt.fuluEnabled)
+			defer cleanup()
+
+			currentEntry := tt.currentEntry
+			nextEntry := tt.nextEntry
+			require.NoError(t, updateENR(localNode, currentEntry, nextEntry))
+			tt.validateNFD(t, localNode, nextEntry)
+		})
+	}
+}

beacon-chain/p2p/interfaces.go

@@ -51,7 +51,7 @@ type (
 		BroadcastBlob(ctx context.Context, subnet uint64, blob *ethpb.BlobSidecar) error
 		BroadcastLightClientOptimisticUpdate(ctx context.Context, update interfaces.LightClientOptimisticUpdate) error
 		BroadcastLightClientFinalityUpdate(ctx context.Context, update interfaces.LightClientFinalityUpdate) error
-		BroadcastDataColumn(root [fieldparams.RootLength]byte, columnSubnet uint64, dataColumnSidecar *ethpb.DataColumnSidecar) error
+		BroadcastDataColumnSidecar(root [fieldparams.RootLength]byte, columnSubnet uint64, dataColumnSidecar *ethpb.DataColumnSidecar) error
 	}
 
 	// SetStreamHandler configures p2p to handle streams of a certain topic ID.

beacon-chain/p2p/peers/scorers/gossip_scorer_test.go

@@ -42,7 +42,7 @@ func TestScorers_Gossip_Score(t *testing.T) {
 			},
 			check: func(scorer *scorers.GossipScorer) {
 				assert.Equal(t, 10.0, scorer.Score("peer1"), "Unexpected score")
-				assert.Equal(t, nil, scorer.IsBadPeer("peer1"), "Unexpected bad peer")
+				assert.NoError(t, scorer.IsBadPeer("peer1"), "Unexpected bad peer")
 				_, _, topicMap, err := scorer.GossipData("peer1")
 				assert.NoError(t, err)
 				assert.Equal(t, uint64(100), topicMap["a"].TimeInMesh, "incorrect time in mesh")

beacon-chain/p2p/pubsub_filter.go

@@ -10,6 +10,7 @@ import (
 	pubsub "github.com/libp2p/go-libp2p-pubsub"
 	pubsubpb "github.com/libp2p/go-libp2p-pubsub/pb"
 	"github.com/libp2p/go-libp2p/core/peer"
+	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 )
 
@@ -40,49 +41,68 @@ func (s *Service) setAllForkDigests() {
 	}
 }
 
+var (
+	errNotReadyToSubscribe         = fmt.Errorf("not ready to subscribe, service is not initialized")
+	errMissingLeadingSlash         = fmt.Errorf("topic is missing leading slash")
+	errTopicMissingProtocolVersion = fmt.Errorf("topic is missing protocol version (eth2)")
+	errTopicPathWrongPartCount     = fmt.Errorf("topic path has wrong part count")
+	errDigestInvalid               = fmt.Errorf("digest is invalid")
+	errDigestUnexpected            = fmt.Errorf("digest is unexpected")
+	errSnappySuffixMissing         = fmt.Errorf("snappy suffix is missing")
+	errTopicNotFound               = fmt.Errorf("topic not found in gossip topic mappings")
+)
+
 // CanSubscribe returns true if the topic is of interest and we could subscribe to it.
 func (s *Service) CanSubscribe(topic string) bool {
-	if !s.isInitialized() {
+	if err := s.checkSubscribable(topic); err != nil {
+		if !errors.Is(err, errNotReadyToSubscribe) {
+			logrus.WithError(err).WithField("topic", topic).Debug("CanSubscribe failed")
+		}
 		return false
 	}
+	return true
+}
+
+func (s *Service) checkSubscribable(topic string) error {
+	if !s.isInitialized() {
+		return errNotReadyToSubscribe
+	}
 	parts := strings.Split(topic, "/")
 	if len(parts) != 5 {
-		return false
+		return errTopicPathWrongPartCount
 	}
 	// The topic must start with a slash, which means the first part will be empty.
 	if parts[0] != "" {
-		return false
+		return errMissingLeadingSlash
 	}
-	if parts[1] != "eth2" {
-		return false
+	protocol, rawDigest, suffix := parts[1], parts[2], parts[4]
+	if protocol != "eth2" {
+		return errTopicMissingProtocolVersion
+	}
+	if suffix != encoder.ProtocolSuffixSSZSnappy {
+		return errSnappySuffixMissing
 	}
 
 	var digest [4]byte
-	dl, err := hex.Decode(digest[:], []byte(parts[2]))
-	if err == nil && dl != 4 {
-		err = fmt.Errorf("expected 4 bytes, got %d", dl)
-	}
+	dl, err := hex.Decode(digest[:], []byte(rawDigest))
 	if err != nil {
-		log.WithError(err).WithField("topic", topic).WithField("digest", parts[2]).Error("CanSubscribe failed to parse message")
-		return false
+		return errors.Wrapf(errDigestInvalid, "%v", err)
+	}
+	if dl != 4 {
+		return errors.Wrapf(errDigestInvalid, "wrong byte length")
 	}
 	if _, ok := s.allForkDigests[digest]; !ok {
-		log.WithField("topic", topic).WithField("digest", fmt.Sprintf("%#x", digest)).Error("CanSubscribe failed to find digest in allForkDigests")
-		return false
-	}
-
-	if parts[4] != encoder.ProtocolSuffixSSZSnappy {
-		return false
+		return errDigestUnexpected
 	}
 
 	// Check the incoming topic matches any topic mapping. This includes a check for part[3].
 	for gt := range gossipTopicMappings {
 		if _, err := scanfcheck(strings.Join(parts[0:4], "/"), gt); err == nil {
-			return true
+			return nil
 		}
 	}
 
-	return false
+	return errTopicNotFound
 }
 
 // FilterIncomingSubscriptions is invoked for all RPCs containing subscription notifications.
@@ -100,7 +120,22 @@ func (s *Service) FilterIncomingSubscriptions(peerID peer.ID, subs []*pubsubpb.R
 		return nil, pubsub.ErrTooManySubscriptions
 	}
 
-	return pubsub.FilterSubscriptions(subs, s.CanSubscribe), nil
+	return pubsub.FilterSubscriptions(subs, s.logCheckSubscribableError(peerID)), nil
+}
+
+func (s *Service) logCheckSubscribableError(pid peer.ID) func(string) bool {
+	return func(topic string) bool {
+		if err := s.checkSubscribable(topic); err != nil {
+			if !errors.Is(err, errNotReadyToSubscribe) {
+				log.WithError(err).WithFields(logrus.Fields{
+					"peerID": pid,
+					"topic":  topic,
+				}).Debug("Peer subscription rejected")
+			}
+			return false
+		}
+		return true
+	}
 }
 
 // scanfcheck uses fmt.Sscanf to check that a given string matches expected format. This method

beacon-chain/p2p/rpc_topic_mappings.go

@@ -169,7 +169,7 @@ var (
 		RPCDataColumnSidecarsByRangeTopicV1: new(pb.DataColumnSidecarsByRangeRequest),
 
 		// DataColumnSidecarsByRoot v1 Message
-		RPCDataColumnSidecarsByRootTopicV1: new(p2ptypes.DataColumnsByRootIdentifiers),
+		RPCDataColumnSidecarsByRootTopicV1: p2ptypes.DataColumnsByRootIdentifiers{},
 	}
 
 	// Maps all registered protocol prefixes.

beacon-chain/p2p/service_test.go

@@ -13,13 +13,13 @@ import (
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/encoder"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/peers"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/peers/scorers"
+	testp2p "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/testing"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/startup"
 	fieldparams "github.com/OffchainLabs/prysm/v6/config/fieldparams"
 	"github.com/OffchainLabs/prysm/v6/config/params"
 	"github.com/OffchainLabs/prysm/v6/testing/assert"
 	"github.com/OffchainLabs/prysm/v6/testing/require"
 	prysmTime "github.com/OffchainLabs/prysm/v6/time"
-	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/libp2p/go-libp2p"
 	"github.com/libp2p/go-libp2p/core/host"
 	"github.com/libp2p/go-libp2p/core/peer"
@@ -30,48 +30,6 @@ import (
 
 const testPingInterval = 100 * time.Millisecond
 
-type mockListener struct {
-	localNode *enode.LocalNode
-}
-
-func (m mockListener) Self() *enode.Node {
-	return m.localNode.Node()
-}
-
-func (mockListener) Close() {
-	// no-op
-}
-
-func (mockListener) Lookup(enode.ID) []*enode.Node {
-	panic("implement me")
-}
-
-func (mockListener) ReadRandomNodes(_ []*enode.Node) int {
-	panic("implement me")
-}
-
-func (mockListener) Resolve(*enode.Node) *enode.Node {
-	panic("implement me")
-}
-
-func (mockListener) Ping(*enode.Node) error {
-	panic("implement me")
-}
-
-func (mockListener) RequestENR(*enode.Node) (*enode.Node, error) {
-	panic("implement me")
-}
-
-func (mockListener) LocalNode() *enode.LocalNode {
-	panic("implement me")
-}
-
-func (mockListener) RandomNodes() enode.Iterator {
-	panic("implement me")
-}
-
-func (mockListener) RebootListener() error { panic("implement me") }
-
 func createHost(t *testing.T, port uint) (host.Host, *ecdsa.PrivateKey, net.IP) {
 	_, pkey := createAddrAndPrivKey(t)
 	ipAddr := net.ParseIP("127.0.0.1")
@@ -87,7 +45,7 @@ func TestService_Stop_SetsStartedToFalse(t *testing.T) {
 	s, err := NewService(t.Context(), &Config{StateNotifier: &mock.MockStateNotifier{}, DB: testDB.SetupDB(t)})
 	require.NoError(t, err)
 	s.started = true
-	s.dv5Listener = &mockListener{}
+	s.dv5Listener = testp2p.NewMockListener(nil, nil)
 	assert.NoError(t, s.Stop())
 	assert.Equal(t, false, s.started)
 }
@@ -113,7 +71,7 @@ func TestService_Start_OnlyStartsOnce(t *testing.T) {
 	}
 	s, err := NewService(t.Context(), cfg)
 	require.NoError(t, err)
-	s.dv5Listener = &mockListener{}
+	s.dv5Listener = testp2p.NewMockListener(nil, nil)
 	s.custodyInfo = &custodyInfo{}
 	exitRoutine := make(chan bool)
 	go func() {
@@ -133,14 +91,14 @@ func TestService_Start_OnlyStartsOnce(t *testing.T) {
 func TestService_Status_NotRunning(t *testing.T) {
 	params.SetupTestConfigCleanup(t)
 	s := &Service{started: false}
-	s.dv5Listener = &mockListener{}
+	s.dv5Listener = testp2p.NewMockListener(nil, nil)
 	assert.ErrorContains(t, "not running", s.Status(), "Status returned wrong error")
 }
 
 func TestService_Status_NoGenesisTimeSet(t *testing.T) {
 	params.SetupTestConfigCleanup(t)
 	s := &Service{started: true}
-	s.dv5Listener = &mockListener{}
+	s.dv5Listener = testp2p.NewMockListener(nil, nil)
 	assert.ErrorContains(t, "no genesis time set", s.Status(), "Status returned wrong error")
 
 	s.genesisTime = time.Now()

beacon-chain/p2p/subnets.go

@@ -134,6 +134,24 @@ func (s *Service) FindAndDialPeersWithSubnets(
 	return nil
 }
 
+// updateDefectiveSubnets updates the defective subnets map when a node with matching subnets is found.
+// It decrements the defective count for each subnet the node satisfies and removes subnets
+// that are fully satisfied (count reaches 0).
+func updateDefectiveSubnets(
+	nodeSubnets map[uint64]bool,
+	defectiveSubnets map[uint64]int,
+) {
+	for subnet := range defectiveSubnets {
+		if !nodeSubnets[subnet] {
+			continue
+		}
+		defectiveSubnets[subnet]--
+		if defectiveSubnets[subnet] == 0 {
+			delete(defectiveSubnets, subnet)
+		}
+	}
+}
+
 // findPeersWithSubnets finds peers subscribed to defective subnets in batches
 // until enough peers are found or the context is canceled.
 // It returns new peers found during the search.
@@ -169,6 +187,7 @@ func (s *Service) findPeersWithSubnets(
 
 	// Crawl the network for peers subscribed to the defective subnets.
 	nodeByNodeID := make(map[enode.ID]*enode.Node)
+
 	for len(defectiveSubnets) > 0 && iterator.Next() {
 		if err := ctx.Err(); err != nil {
 			// Convert the map to a slice.
@@ -180,14 +199,28 @@ func (s *Service) findPeersWithSubnets(
 			return peersToDial, err
 		}
 
-		// Get all needed subnets that the node is subscribed to.
-		// Skip nodes that are not subscribed to any of the defective subnets.
 		node := iterator.Node()
 
+		// Remove duplicates, keeping the node with higher seq.
+		existing, ok := nodeByNodeID[node.ID()]
+		if ok && existing.Seq() >= node.Seq() {
+			continue // keep existing and skip.
+		}
+
+		// Treat nodes that exist in nodeByNodeID with higher seq numbers as new peers
+		// Skip peer not matching the filter.
 		if !s.filterPeer(node) {
+			if ok {
+				// this means the existing peer with the lower sequence number is no longer valid
+				delete(nodeByNodeID, existing.ID())
+				// Note: We are choosing to not rollback changes to the defective subnets map in favor of calling s.defectiveSubnets once again after dialing peers.
+				// This is a case that should rarely happen and should be handled through a second iteration in FindAndDialPeersWithSubnets
+			}
 			continue
 		}
 
+		// Get all needed subnets that the node is subscribed to.
+		// Skip nodes that are not subscribed to any of the defective subnets.
 		nodeSubnets, err := filter(node)
 		if err != nil {
 			return nil, errors.Wrap(err, "filter node")
@@ -196,30 +229,14 @@ func (s *Service) findPeersWithSubnets(
 			continue
 		}
 
-		// Remove duplicates, keeping the node with higher seq.
-		existing, ok := nodeByNodeID[node.ID()]
-		if ok && existing.Seq() > node.Seq() {
-			continue
-		}
-		nodeByNodeID[node.ID()] = node
-
 		// We found a new peer. Modify the defective subnets map
 		// and the filter accordingly.
-		for subnet := range defectiveSubnets {
-			if !nodeSubnets[subnet] {
-				continue
-			}
+		nodeByNodeID[node.ID()] = node
 
-			defectiveSubnets[subnet]--
-
-			if defectiveSubnets[subnet] == 0 {
-				delete(defectiveSubnets, subnet)
-			}
-
-			filter, err = s.nodeFilter(topicFormat, defectiveSubnets)
-			if err != nil {
-				return nil, errors.Wrap(err, "node filter")
-			}
+		updateDefectiveSubnets(nodeSubnets, defectiveSubnets)
+		filter, err = s.nodeFilter(topicFormat, defectiveSubnets)
+		if err != nil {
+			return nil, errors.Wrap(err, "node filter")
 		}
 	}
 

beacon-chain/p2p/subnets_test.go

@@ -10,14 +10,19 @@ import (
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/cache"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/peerdas"
 	testDB "github.com/OffchainLabs/prysm/v6/beacon-chain/db/testing"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/peers"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/peers/scorers"
+	testp2p "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/testing"
 	"github.com/OffchainLabs/prysm/v6/cmd/beacon-chain/flags"
 	"github.com/OffchainLabs/prysm/v6/config/params"
 	ecdsaprysm "github.com/OffchainLabs/prysm/v6/crypto/ecdsa"
+	"github.com/OffchainLabs/prysm/v6/encoding/bytesutil"
 	"github.com/OffchainLabs/prysm/v6/testing/assert"
 	"github.com/OffchainLabs/prysm/v6/testing/require"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/p2p/enr"
 	"github.com/libp2p/go-libp2p/core/crypto"
+	"github.com/libp2p/go-libp2p/core/network"
 	"github.com/prysmaticlabs/go-bitfield"
 )
 
@@ -541,3 +546,552 @@ func TestInitializePersistentSubnets(t *testing.T) {
 	assert.Equal(t, 2, len(subs))
 	assert.Equal(t, true, expTime.After(time.Now()))
 }
+
+func TestFindPeersWithSubnets_NodeDeduplication(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	cache.SubnetIDs.EmptyAllCaches()
+	defer cache.SubnetIDs.EmptyAllCaches()
+
+	ctx := context.Background()
+	db := testDB.SetupDB(t)
+
+	localNode1 := createTestNodeWithID(t, "node1")
+	localNode2 := createTestNodeWithID(t, "node2")
+	localNode3 := createTestNodeWithID(t, "node3")
+
+	// Create different sequence versions of node1 with subnet 1
+	setNodeSubnets(localNode1, []uint64{1})
+	setNodeSeq(localNode1, 1)
+	node1_seq1_subnet1 := localNode1.Node()
+	setNodeSeq(localNode1, 2)
+	node1_seq2_subnet1 := localNode1.Node() // Same ID, higher seq
+	setNodeSeq(localNode1, 3)
+	node1_seq3_subnet1 := localNode1.Node() // Same ID, even higher seq
+
+	// Node2 with different sequences and subnets
+	setNodeSubnets(localNode2, []uint64{1})
+	node2_seq1_subnet1 := localNode2.Node()
+	setNodeSubnets(localNode2, []uint64{2}) // Different subnet
+	setNodeSeq(localNode2, 2)
+	node2_seq2_subnet2 := localNode2.Node()
+
+	// Node3 with multiple subnets
+	setNodeSubnets(localNode3, []uint64{1, 2})
+	node3_seq1_subnet1_2 := localNode3.Node()
+
+	tests := []struct {
+		name             string
+		nodes            []*enode.Node
+		defectiveSubnets map[uint64]int
+		expectedCount    int
+		description      string
+		eval             func(t *testing.T, result []*enode.Node) // Custom validation function
+	}{
+		{
+			name: "No duplicates - unique nodes with same subnet",
+			nodes: []*enode.Node{
+				node2_seq1_subnet1,
+				node3_seq1_subnet1_2,
+			},
+			defectiveSubnets: map[uint64]int{1: 2},
+			expectedCount:    2,
+			description:      "Should return all unique nodes subscribed to subnet",
+			eval:             nil, // No special validation needed
+		},
+		{
+			name: "Duplicate with lower seq first - should replace",
+			nodes: []*enode.Node{
+				node1_seq1_subnet1,
+				node1_seq2_subnet1, // Higher seq, should replace
+				node2_seq1_subnet1, // Different node to ensure we process enough nodes
+			},
+			defectiveSubnets: map[uint64]int{1: 2}, // Need 2 peers for subnet 1
+			expectedCount:    2,
+			description:      "Should replace with higher seq node for same subnet",
+			eval: func(t *testing.T, result []*enode.Node) {
+				found := false
+				for _, node := range result {
+					if node.ID() == node1_seq2_subnet1.ID() && node.Seq() == node1_seq2_subnet1.Seq() {
+						found = true
+						break
+					}
+				}
+				require.Equal(t, true, found, "Should have node with higher seq")
+			},
+		},
+		{
+			name: "Duplicate with higher seq first - should keep existing",
+			nodes: []*enode.Node{
+				node1_seq3_subnet1, // Higher seq
+				node1_seq2_subnet1, // Lower seq, should be skipped (continue branch)
+				node1_seq1_subnet1, // Even lower seq, should also be skipped (continue branch)
+				node2_seq1_subnet1, // Different node
+			},
+			defectiveSubnets: map[uint64]int{1: 2},
+			expectedCount:    2,
+			description:      "Should keep existing node with higher seq and skip lower seq duplicates",
+			eval: func(t *testing.T, result []*enode.Node) {
+				found := false
+				for _, node := range result {
+					if node.ID() == node1_seq3_subnet1.ID() && node.Seq() == node1_seq3_subnet1.Seq() {
+						found = true
+						break
+					}
+				}
+				require.Equal(t, true, found, "Should have node with highest seq")
+			},
+		},
+		{
+			name: "Multiple updates for same node",
+			nodes: []*enode.Node{
+				node1_seq1_subnet1,
+				node1_seq2_subnet1, // Should replace seq1
+				node1_seq3_subnet1, // Should replace seq2
+				node2_seq1_subnet1, // Different node
+			},
+			defectiveSubnets: map[uint64]int{1: 2},
+			expectedCount:    2,
+			description:      "Should keep updating to highest seq",
+			eval: func(t *testing.T, result []*enode.Node) {
+				found := false
+				for _, node := range result {
+					if node.ID() == node1_seq3_subnet1.ID() && node.Seq() == node1_seq3_subnet1.Seq() {
+						found = true
+						break
+					}
+				}
+				require.Equal(t, true, found, "Should have node with highest seq")
+			},
+		},
+		{
+			name: "Duplicate with equal seq in subnets - should skip",
+			nodes: []*enode.Node{
+				node1_seq2_subnet1, // First occurrence
+				node1_seq2_subnet1, // Same exact node instance, should be skipped (continue branch)
+				node2_seq1_subnet1, // Different node
+			},
+			defectiveSubnets: map[uint64]int{1: 2},
+			expectedCount:    2,
+			description:      "Should skip duplicate with equal sequence number in subnet search",
+			eval: func(t *testing.T, result []*enode.Node) {
+				foundNode1 := false
+				foundNode2 := false
+				node1Count := 0
+				for _, node := range result {
+					if node.ID() == node1_seq2_subnet1.ID() {
+						require.Equal(t, node1_seq2_subnet1.Seq(), node.Seq(), "Node1 should have expected seq")
+						foundNode1 = true
+						node1Count++
+					}
+					if node.ID() == node2_seq1_subnet1.ID() {
+						foundNode2 = true
+					}
+				}
+				require.Equal(t, true, foundNode1, "Should have node1")
+				require.Equal(t, true, foundNode2, "Should have node2")
+				require.Equal(t, 1, node1Count, "Should have exactly one instance of node1")
+			},
+		},
+		{
+			name: "Mix with different subnets",
+			nodes: []*enode.Node{
+				node2_seq1_subnet1,
+				node2_seq2_subnet2, // Higher seq but different subnet
+				node3_seq1_subnet1_2,
+			},
+			defectiveSubnets: map[uint64]int{1: 2, 2: 1},
+			expectedCount:    2, // node2 (latest) and node3
+			description:      "Should handle nodes with different subnet subscriptions",
+			eval:             nil, // Basic count validation is sufficient
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gFlags := new(flags.GlobalFlags)
+			gFlags.MinimumPeersPerSubnet = 1
+			flags.Init(gFlags)
+			defer flags.Init(new(flags.GlobalFlags))
+
+			fakePeer := testp2p.NewTestP2P(t)
+
+			s := &Service{
+				cfg: &Config{
+					MaxPeers: 30,
+					DB:       db,
+				},
+				genesisTime:           time.Now(),
+				genesisValidatorsRoot: bytesutil.PadTo([]byte{'A'}, 32),
+				peers: peers.NewStatus(ctx, &peers.StatusConfig{
+					PeerLimit:    30,
+					ScorerParams: &scorers.Config{},
+				}),
+				host: fakePeer.BHost,
+			}
+
+			localNode := createTestNodeRandom(t)
+
+			mockIter := testp2p.NewMockIterator(tt.nodes)
+			s.dv5Listener = testp2p.NewMockListener(localNode, mockIter)
+
+			digest, err := s.currentForkDigest()
+			require.NoError(t, err)
+
+			ctxWithTimeout, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
+			defer cancel()
+
+			result, err := s.findPeersWithSubnets(
+				ctxWithTimeout,
+				AttestationSubnetTopicFormat,
+				digest,
+				1,
+				tt.defectiveSubnets,
+			)
+
+			require.NoError(t, err, tt.description)
+			require.Equal(t, tt.expectedCount, len(result), tt.description)
+
+			if tt.eval != nil {
+				tt.eval(t, result)
+			}
+		})
+	}
+}
+
+func TestFindPeersWithSubnets_FilterPeerRemoval(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	cache.SubnetIDs.EmptyAllCaches()
+	defer cache.SubnetIDs.EmptyAllCaches()
+
+	ctx := context.Background()
+	db := testDB.SetupDB(t)
+
+	localNode1 := createTestNodeWithID(t, "node1")
+	localNode2 := createTestNodeWithID(t, "node2")
+	localNode3 := createTestNodeWithID(t, "node3")
+
+	// Create versions of node1 with subnet 1
+	setNodeSubnets(localNode1, []uint64{1})
+	setNodeSeq(localNode1, 1)
+	node1_seq1_valid_subnet1 := localNode1.Node()
+
+	// Create bad version (higher seq)
+	setNodeSeq(localNode1, 2)
+	node1_seq2_bad_subnet1 := localNode1.Node()
+
+	// Create another valid version
+	setNodeSeq(localNode1, 3)
+	node1_seq3_valid_subnet1 := localNode1.Node()
+
+	// Node2 with subnet 1
+	setNodeSubnets(localNode2, []uint64{1})
+	node2_seq1_valid_subnet1 := localNode2.Node()
+
+	// Node3 with subnet 1 and 2
+	setNodeSubnets(localNode3, []uint64{1, 2})
+	node3_seq1_valid_subnet1_2 := localNode3.Node()
+
+	tests := []struct {
+		name             string
+		nodes            []*enode.Node
+		defectiveSubnets map[uint64]int
+		expectedCount    int
+		description      string
+		eval             func(t *testing.T, result []*enode.Node)
+	}{
+		{
+			name: "Valid node in subnet followed by bad version - should remove",
+			nodes: []*enode.Node{
+				node1_seq1_valid_subnet1, // First add valid node with subnet 1
+				node1_seq2_bad_subnet1,   // Invalid version with higher seq - should delete
+				node2_seq1_valid_subnet1, // Different valid node with subnet 1
+			},
+			defectiveSubnets: map[uint64]int{1: 2}, // Need 2 peers for subnet 1
+			expectedCount:    1,                    // Only node2 should remain
+			description:      "Should remove node from map when bad version arrives, even if it has required subnet",
+			eval: func(t *testing.T, result []*enode.Node) {
+				foundNode1 := false
+				foundNode2 := false
+				for _, node := range result {
+					if node.ID() == node1_seq1_valid_subnet1.ID() {
+						foundNode1 = true
+					}
+					if node.ID() == node2_seq1_valid_subnet1.ID() {
+						foundNode2 = true
+					}
+				}
+				require.Equal(t, false, foundNode1, "Node1 should have been removed despite having subnet")
+				require.Equal(t, true, foundNode2, "Node2 should be present")
+			},
+		},
+		{
+			name: "Bad node with subnet stays bad even with higher seq",
+			nodes: []*enode.Node{
+				node1_seq2_bad_subnet1,   // First bad node - not added
+				node1_seq3_valid_subnet1, // Higher seq but same bad peer ID
+				node2_seq1_valid_subnet1, // Different valid node
+			},
+			defectiveSubnets: map[uint64]int{1: 2},
+			expectedCount:    1, // Only node2 (node1 remains bad)
+			description:      "Bad peer with subnet remains bad even with higher seq",
+			eval: func(t *testing.T, result []*enode.Node) {
+				foundNode1 := false
+				foundNode2 := false
+				for _, node := range result {
+					if node.ID() == node1_seq3_valid_subnet1.ID() {
+						foundNode1 = true
+					}
+					if node.ID() == node2_seq1_valid_subnet1.ID() {
+						foundNode2 = true
+					}
+				}
+				require.Equal(t, false, foundNode1, "Node1 should remain bad despite having subnet")
+				require.Equal(t, true, foundNode2, "Node2 should be present")
+			},
+		},
+		{
+			name: "Mixed valid and bad nodes with subnets",
+			nodes: []*enode.Node{
+				node1_seq1_valid_subnet1,   // Add valid node1 with subnet
+				node2_seq1_valid_subnet1,   // Add valid node2 with subnet
+				node1_seq2_bad_subnet1,     // Invalid update for node1 - should remove
+				node3_seq1_valid_subnet1_2, // Add valid node3 with multiple subnets
+			},
+			defectiveSubnets: map[uint64]int{1: 3}, // Need 3 peers for subnet 1
+			expectedCount:    2,                    // Only node2 and node3 should remain
+			description:      "Should handle removal of nodes with subnets when they become bad",
+			eval: func(t *testing.T, result []*enode.Node) {
+				foundNode1 := false
+				foundNode2 := false
+				foundNode3 := false
+				for _, node := range result {
+					if node.ID() == node1_seq1_valid_subnet1.ID() {
+						foundNode1 = true
+					}
+					if node.ID() == node2_seq1_valid_subnet1.ID() {
+						foundNode2 = true
+					}
+					if node.ID() == node3_seq1_valid_subnet1_2.ID() {
+						foundNode3 = true
+					}
+				}
+				require.Equal(t, false, foundNode1, "Node1 should have been removed")
+				require.Equal(t, true, foundNode2, "Node2 should be present")
+				require.Equal(t, true, foundNode3, "Node3 should be present")
+			},
+		},
+		{
+			name: "Node with subnet marked bad stays bad for all sequences",
+			nodes: []*enode.Node{
+				node1_seq1_valid_subnet1, // Add valid node1 with subnet
+				node1_seq2_bad_subnet1,   // Bad update - should remove and mark bad
+				node1_seq3_valid_subnet1, // Higher seq but still same bad peer ID
+				node2_seq1_valid_subnet1, // Different valid node
+			},
+			defectiveSubnets: map[uint64]int{1: 2},
+			expectedCount:    1, // Only node2 (node1 stays bad)
+			description:      "Once marked bad, subnet peer stays bad for all sequences",
+			eval: func(t *testing.T, result []*enode.Node) {
+				foundNode1 := false
+				foundNode2 := false
+				for _, node := range result {
+					if node.ID() == node1_seq3_valid_subnet1.ID() {
+						foundNode1 = true
+					}
+					if node.ID() == node2_seq1_valid_subnet1.ID() {
+						foundNode2 = true
+					}
+				}
+				require.Equal(t, false, foundNode1, "Node1 should stay bad")
+				require.Equal(t, true, foundNode2, "Node2 should be present")
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Initialize flags for subnet operations
+			gFlags := new(flags.GlobalFlags)
+			gFlags.MinimumPeersPerSubnet = 1
+			flags.Init(gFlags)
+			defer flags.Init(new(flags.GlobalFlags))
+
+			// Create test P2P instance
+			fakePeer := testp2p.NewTestP2P(t)
+
+			// Create mock service
+			s := &Service{
+				cfg: &Config{
+					MaxPeers: 30,
+					DB:       db,
+				},
+				genesisTime:           time.Now(),
+				genesisValidatorsRoot: bytesutil.PadTo([]byte{'A'}, 32),
+				peers: peers.NewStatus(ctx, &peers.StatusConfig{
+					PeerLimit:    30,
+					ScorerParams: &scorers.Config{},
+				}),
+				host: fakePeer.BHost,
+			}
+
+			// Mark specific node versions as "bad" to simulate filterPeer failures
+			for _, node := range tt.nodes {
+				if node == node1_seq2_bad_subnet1 {
+					// Get peer ID from the node to mark it as bad
+					peerData, _, _ := convertToAddrInfo(node)
+					if peerData != nil {
+						s.peers.Add(node.Record(), peerData.ID, nil, network.DirUnknown)
+						// Mark as bad peer - this will make filterPeer return false
+						s.peers.Scorers().BadResponsesScorer().Increment(peerData.ID)
+						s.peers.Scorers().BadResponsesScorer().Increment(peerData.ID)
+						s.peers.Scorers().BadResponsesScorer().Increment(peerData.ID)
+					}
+				}
+			}
+
+			localNode := createTestNodeRandom(t)
+
+			mockIter := testp2p.NewMockIterator(tt.nodes)
+			s.dv5Listener = testp2p.NewMockListener(localNode, mockIter)
+
+			digest, err := s.currentForkDigest()
+			require.NoError(t, err)
+
+			ctxWithTimeout, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
+			defer cancel()
+
+			result, err := s.findPeersWithSubnets(
+				ctxWithTimeout,
+				AttestationSubnetTopicFormat,
+				digest,
+				1,
+				tt.defectiveSubnets,
+			)
+
+			require.NoError(t, err, tt.description)
+			require.Equal(t, tt.expectedCount, len(result), tt.description)
+
+			if tt.eval != nil {
+				tt.eval(t, result)
+			}
+		})
+	}
+}
+
+// callbackIterator allows us to execute callbacks at specific points during iteration
+type callbackIteratorForSubnets struct {
+	nodes     []*enode.Node
+	index     int
+	callbacks map[int]func() // map from index to callback function
+}
+
+func (c *callbackIteratorForSubnets) Next() bool {
+	// Execute callback before checking if we can continue (if one exists)
+	if callback, exists := c.callbacks[c.index]; exists {
+		callback()
+	}
+
+	return c.index < len(c.nodes)
+}
+
+func (c *callbackIteratorForSubnets) Node() *enode.Node {
+	if c.index >= len(c.nodes) {
+		return nil
+	}
+
+	node := c.nodes[c.index]
+	c.index++
+	return node
+}
+
+func (c *callbackIteratorForSubnets) Close() {
+	// Nothing to clean up for this simple implementation
+}
+
+func TestFindPeersWithSubnets_received_bad_existing_node(t *testing.T) {
+	// This test successfully triggers delete(nodeByNodeID, node.ID()) in subnets.go by:
+	// 1. Processing node1_seq1 first (passes filterPeer, gets added to map
+	// 2. Callback marks peer as bad before processing node1_seq2"
+	// 3. Processing node1_seq2 (fails filterPeer, triggers delete since ok=true
+	params.SetupTestConfigCleanup(t)
+	cache.SubnetIDs.EmptyAllCaches()
+	defer cache.SubnetIDs.EmptyAllCaches()
+
+	ctx := context.Background()
+	db := testDB.SetupDB(t)
+
+	// Create LocalNode with same ID but different sequences
+	localNode1 := createTestNodeWithID(t, "testnode")
+	setNodeSubnets(localNode1, []uint64{1})
+	node1_seq1 := localNode1.Node() // Get current node
+	currentSeq := node1_seq1.Seq()
+	setNodeSeq(localNode1, currentSeq+1) // Increment sequence by 1
+	node1_seq2 := localNode1.Node()      // This should have higher seq
+
+	// Additional node to ensure we have enough peers to process
+	localNode2 := createTestNodeWithID(t, "othernode")
+	setNodeSubnets(localNode2, []uint64{1})
+	node2 := localNode2.Node()
+
+	gFlags := new(flags.GlobalFlags)
+	gFlags.MinimumPeersPerSubnet = 1
+	flags.Init(gFlags)
+	defer flags.Init(new(flags.GlobalFlags))
+
+	fakePeer := testp2p.NewTestP2P(t)
+
+	service := &Service{
+		cfg: &Config{
+			MaxPeers: 30,
+			DB:       db,
+		},
+		genesisTime:           time.Now(),
+		genesisValidatorsRoot: bytesutil.PadTo([]byte{'A'}, 32),
+		peers: peers.NewStatus(ctx, &peers.StatusConfig{
+			PeerLimit:    30,
+			ScorerParams: &scorers.Config{},
+		}),
+		host: fakePeer.BHost,
+	}
+
+	// Create iterator with callback that marks peer as bad before processing node1_seq2
+	iter := &callbackIteratorForSubnets{
+		nodes: []*enode.Node{node1_seq1, node1_seq2, node2},
+		index: 0,
+		callbacks: map[int]func(){
+			1: func() { // Before processing node1_seq2 (index 1)
+				// Mark peer as bad before processing node1_seq2
+				peerData, _, _ := convertToAddrInfo(node1_seq2)
+				if peerData != nil {
+					service.peers.Add(node1_seq2.Record(), peerData.ID, nil, network.DirUnknown)
+					// Mark as bad peer - need enough increments to exceed threshold (6)
+					for i := 0; i < 10; i++ {
+						service.peers.Scorers().BadResponsesScorer().Increment(peerData.ID)
+					}
+				}
+			},
+		},
+	}
+
+	localNode := createTestNodeRandom(t)
+	service.dv5Listener = testp2p.NewMockListener(localNode, iter)
+
+	digest, err := service.currentForkDigest()
+	require.NoError(t, err)
+
+	// Run findPeersWithSubnets - node1_seq1 gets processed first, then callback marks peer bad, then node1_seq2 fails
+	ctxWithTimeout, cancel := context.WithTimeout(ctx, 1*time.Second)
+	defer cancel()
+
+	result, err := service.findPeersWithSubnets(
+		ctxWithTimeout,
+		AttestationSubnetTopicFormat,
+		digest,
+		1,
+		map[uint64]int{1: 2}, // Need 2 peers for subnet 1
+	)
+
+	require.NoError(t, err)
+	require.Equal(t, 1, len(result))
+	require.Equal(t, localNode2.Node().ID(), result[0].ID()) // only node2 should remain
+}

beacon-chain/p2p/testing/BUILD.bazel

@@ -7,6 +7,7 @@ go_library(
         "fuzz_p2p.go",
         "mock_broadcaster.go",
         "mock_host.go",
+        "mock_listener.go",
         "mock_metadataprovider.go",
         "mock_peermanager.go",
         "mock_peersprovider.go",

beacon-chain/p2p/testing/fuzz_p2p.go

@@ -167,8 +167,8 @@ func (*FakeP2P) BroadcastLightClientFinalityUpdate(_ context.Context, _ interfac
 	return nil
 }
 
-// BroadcastDataColumn -- fake.
-func (*FakeP2P) BroadcastDataColumn(_ [fieldparams.RootLength]byte, _ uint64, _ *ethpb.DataColumnSidecar) error {
+// BroadcastDataColumnSidecar -- fake.
+func (*FakeP2P) BroadcastDataColumnSidecar(_ [fieldparams.RootLength]byte, _ uint64, _ *ethpb.DataColumnSidecar) error {
 	return nil
 }
 

beacon-chain/p2p/testing/mock_broadcaster.go

@@ -62,8 +62,8 @@ func (m *MockBroadcaster) BroadcastLightClientFinalityUpdate(_ context.Context,
 	return nil
 }
 
-// BroadcastDataColumn broadcasts a data column for mock.
-func (m *MockBroadcaster) BroadcastDataColumn([fieldparams.RootLength]byte, uint64, *ethpb.DataColumnSidecar) error {
+// BroadcastDataColumnSidecar broadcasts a data column for mock.
+func (m *MockBroadcaster) BroadcastDataColumnSidecar([fieldparams.RootLength]byte, uint64, *ethpb.DataColumnSidecar) error {
 	m.BroadcastCalled.Store(true)
 	return nil
 }

beacon-chain/p2p/testing/mock_listener.go

@@ -0,0 +1,128 @@
+package testing
+
+import (
+	"github.com/ethereum/go-ethereum/p2p/enode"
+)
+
+// MockListener is a mock implementation of the Listener and ListenerRebooter interfaces
+// that can be used in tests. It provides configurable behavior for all methods.
+type MockListener struct {
+	LocalNodeFunc   func() *enode.LocalNode
+	SelfFunc        func() *enode.Node
+	RandomNodesFunc func() enode.Iterator
+	LookupFunc      func(enode.ID) []*enode.Node
+	ResolveFunc     func(*enode.Node) *enode.Node
+	PingFunc        func(*enode.Node) error
+	RequestENRFunc  func(*enode.Node) (*enode.Node, error)
+	RebootFunc      func() error
+	CloseFunc       func()
+
+	// Default implementations
+	localNode *enode.LocalNode
+	iterator  enode.Iterator
+}
+
+// NewMockListener creates a new MockListener with default implementations
+func NewMockListener(localNode *enode.LocalNode, iterator enode.Iterator) *MockListener {
+	return &MockListener{
+		localNode: localNode,
+		iterator:  iterator,
+	}
+}
+
+func (m *MockListener) LocalNode() *enode.LocalNode {
+	if m.LocalNodeFunc != nil {
+		return m.LocalNodeFunc()
+	}
+	return m.localNode
+}
+
+func (m *MockListener) Self() *enode.Node {
+	if m.SelfFunc != nil {
+		return m.SelfFunc()
+	}
+	if m.localNode != nil {
+		return m.localNode.Node()
+	}
+	return nil
+}
+
+func (m *MockListener) RandomNodes() enode.Iterator {
+	if m.RandomNodesFunc != nil {
+		return m.RandomNodesFunc()
+	}
+	return m.iterator
+}
+
+func (m *MockListener) Lookup(id enode.ID) []*enode.Node {
+	if m.LookupFunc != nil {
+		return m.LookupFunc(id)
+	}
+	return nil
+}
+
+func (m *MockListener) Resolve(node *enode.Node) *enode.Node {
+	if m.ResolveFunc != nil {
+		return m.ResolveFunc(node)
+	}
+	return nil
+}
+
+func (m *MockListener) Ping(node *enode.Node) error {
+	if m.PingFunc != nil {
+		return m.PingFunc(node)
+	}
+	return nil
+}
+
+func (m *MockListener) RequestENR(node *enode.Node) (*enode.Node, error) {
+	if m.RequestENRFunc != nil {
+		return m.RequestENRFunc(node)
+	}
+	return nil, nil
+}
+
+func (m *MockListener) RebootListener() error {
+	if m.RebootFunc != nil {
+		return m.RebootFunc()
+	}
+	return nil
+}
+
+func (m *MockListener) Close() {
+	if m.CloseFunc != nil {
+		m.CloseFunc()
+	}
+}
+
+// MockIterator is a mock implementation of enode.Iterator for testing
+type MockIterator struct {
+	Nodes    []*enode.Node
+	Position int
+	Closed   bool
+}
+
+func NewMockIterator(nodes []*enode.Node) *MockIterator {
+	return &MockIterator{
+		Nodes: nodes,
+	}
+}
+
+func (m *MockIterator) Next() bool {
+	if m.Closed || m.Position >= len(m.Nodes) {
+		return false
+	}
+	m.Position++
+	return true
+}
+
+func (m *MockIterator) Node() *enode.Node {
+	if m.Position == 0 || m.Position > len(m.Nodes) {
+		return nil
+	}
+	return m.Nodes[m.Position-1]
+}
+
+func (m *MockIterator) Close() {
+	m.Closed = true
+}

beacon-chain/p2p/testing/p2p.go

@@ -63,6 +63,7 @@ type TestP2P struct {
 	custodyInfoMut        sync.RWMutex // protects custodyGroupCount and earliestAvailableSlot
 	earliestAvailableSlot primitives.Slot
 	custodyGroupCount     uint64
+	enr                   *enr.Record
 }
 
 // NewTestP2P initializes a new p2p test service.
@@ -103,6 +104,7 @@ func NewTestP2P(t *testing.T, userOptions ...config.Option) *TestP2P {
 		pubsub:       ps,
 		joinedTopics: map[string]*pubsub.Topic{},
 		peers:        peerStatuses,
+		enr:          new(enr.Record),
 	}
 }
 
@@ -228,8 +230,8 @@ func (p *TestP2P) BroadcastLightClientFinalityUpdate(_ context.Context, _ interf
 	return nil
 }
 
-// BroadcastDataColumn broadcasts a data column for mock.
-func (p *TestP2P) BroadcastDataColumn([fieldparams.RootLength]byte, uint64, *ethpb.DataColumnSidecar) error {
+// BroadcastDataColumnSidecar broadcasts a data column for mock.
+func (p *TestP2P) BroadcastDataColumnSidecar([fieldparams.RootLength]byte, uint64, *ethpb.DataColumnSidecar) error {
 	p.BroadcastCalled.Store(true)
 	return nil
 }
@@ -310,8 +312,8 @@ func (p *TestP2P) Host() host.Host {
 }
 
 // ENR returns the enr of the local peer.
-func (*TestP2P) ENR() *enr.Record {
-	return new(enr.Record)
+func (p *TestP2P) ENR() *enr.Record {
+	return p.enr
 }
 
 // NodeID returns the node id of the local peer.

beacon-chain/rpc/eth/beacon/BUILD.bazel

@@ -18,6 +18,7 @@ go_library(
         "//api/server:go_default_library",
         "//api/server/structs:go_default_library",
         "//beacon-chain/blockchain:go_default_library",
+        "//beacon-chain/blockchain/kzg:go_default_library",
         "//beacon-chain/cache:go_default_library",
         "//beacon-chain/cache/depositsnapshot:go_default_library",
         "//beacon-chain/core/altair:go_default_library",
@@ -60,7 +61,6 @@ go_library(
         "//runtime/version:go_default_library",
         "//time/slots:go_default_library",
         "@com_github_ethereum_go_ethereum//common/hexutil:go_default_library",
-        "@com_github_ethereum_go_ethereum//crypto/kzg4844:go_default_library",
         "@com_github_pkg_errors//:go_default_library",
         "@com_github_prometheus_client_golang//prometheus:go_default_library",
         "@com_github_prometheus_client_golang//prometheus/promauto:go_default_library",
@@ -72,6 +72,7 @@ go_library(
 go_test(
     name = "go_default_test",
     srcs = [
+        "handlers_equivocation_test.go",
         "handlers_pool_test.go",
         "handlers_state_test.go",
         "handlers_test.go",
@@ -83,6 +84,7 @@ go_test(
         "//api:go_default_library",
         "//api/server:go_default_library",
         "//api/server/structs:go_default_library",
+        "//beacon-chain/blockchain/kzg:go_default_library",
         "//beacon-chain/blockchain/testing:go_default_library",
         "//beacon-chain/cache/depositsnapshot:go_default_library",
         "//beacon-chain/core/signing:go_default_library",
@@ -123,7 +125,6 @@ go_test(
         "//testing/require:go_default_library",
         "//testing/util:go_default_library",
         "//time/slots:go_default_library",
-        "@com_github_crate_crypto_go_kzg_4844//:go_default_library",
         "@com_github_ethereum_go_ethereum//common/hexutil:go_default_library",
         "@com_github_pkg_errors//:go_default_library",
         "@com_github_prysmaticlabs_fastssz//:go_default_library",

beacon-chain/rpc/eth/beacon/handlers.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/OffchainLabs/prysm/v6/api"
 	"github.com/OffchainLabs/prysm/v6/api/server/structs"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain/kzg"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/cache/depositsnapshot"
 	corehelpers "github.com/OffchainLabs/prysm/v6/beacon-chain/core/helpers"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/transition"
@@ -32,7 +33,6 @@ import (
 	"github.com/OffchainLabs/prysm/v6/runtime/version"
 	"github.com/OffchainLabs/prysm/v6/time/slots"
 	"github.com/ethereum/go-ethereum/common/hexutil"
-	"github.com/ethereum/go-ethereum/crypto/kzg4844"
 	"github.com/pkg/errors"
 	ssz "github.com/prysmaticlabs/fastssz"
 	"github.com/sirupsen/logrus"
@@ -701,7 +701,7 @@ func (s *Server) publishBlockSSZ(ctx context.Context, w http.ResponseWriter, r *
 	// Validate and optionally broadcast sidecars on equivocation.
 	if err := s.validateBroadcast(ctx, r, genericBlock); err != nil {
 		if errors.Is(err, errEquivocatedBlock) {
-			b, err := blocks.NewSignedBeaconBlock(genericBlock)
+			b, err := blocks.NewSignedBeaconBlock(genericBlock.Block)
 			if err != nil {
 				httputil.HandleError(w, err.Error(), http.StatusBadRequest)
 				return
@@ -855,7 +855,7 @@ func (s *Server) publishBlock(ctx context.Context, w http.ResponseWriter, r *htt
 	// Validate and optionally broadcast sidecars on equivocation.
 	if err := s.validateBroadcast(ctx, r, genericBlock); err != nil {
 		if errors.Is(err, errEquivocatedBlock) {
-			b, err := blocks.NewSignedBeaconBlock(genericBlock)
+			b, err := blocks.NewSignedBeaconBlock(genericBlock.Block)
 			if err != nil {
 				httputil.HandleError(w, err.Error(), http.StatusBadRequest)
 				return
@@ -942,14 +942,13 @@ func decodePhase0JSON(body []byte) (*eth.GenericSignedBeaconBlock, error) {
 // broadcastSidecarsIfSupported broadcasts blob sidecars when an equivocated block occurs.
 func broadcastSidecarsIfSupported(ctx context.Context, s *Server, b interfaces.SignedBeaconBlock, gb *eth.GenericSignedBeaconBlock, versionHeader string) error {
 	switch versionHeader {
-	case version.String(version.Fulu):
-		return s.broadcastSeenBlockSidecars(ctx, b, gb.GetFulu().Blobs, gb.GetFulu().KzgProofs)
 	case version.String(version.Electra):
 		return s.broadcastSeenBlockSidecars(ctx, b, gb.GetElectra().Blobs, gb.GetElectra().KzgProofs)
 	case version.String(version.Deneb):
 		return s.broadcastSeenBlockSidecars(ctx, b, gb.GetDeneb().Blobs, gb.GetDeneb().KzgProofs)
 	default:
 		// other forks before Deneb do not support blob sidecars
+		// forks after fulu do not support blob sidecars, instead support data columns, no need to rebroadcast
 		return nil
 	}
 }
@@ -1053,7 +1052,7 @@ func (s *Server) validateConsensus(ctx context.Context, b *eth.GenericSignedBeac
 		return nil
 	}
 
-	if err := s.validateBlobSidecars(blk, blobs, proofs); err != nil {
+	if err := s.validateBlobs(blk, blobs, proofs); err != nil {
 		return err
 	}
 
@@ -1067,23 +1066,41 @@ func (s *Server) validateEquivocation(blk interfaces.ReadOnlyBeaconBlock) error
 	return nil
 }
 
-func (s *Server) validateBlobSidecars(blk interfaces.SignedBeaconBlock, blobs [][]byte, proofs [][]byte) error {
+func (s *Server) validateBlobs(blk interfaces.SignedBeaconBlock, blobs [][]byte, proofs [][]byte) error {
 	if blk.Version() < version.Deneb {
 		return nil
 	}
-	kzgs, err := blk.Block().Body().BlobKzgCommitments()
+	numberOfColumns := params.BeaconConfig().NumberOfColumns
+	commitments, err := blk.Block().Body().BlobKzgCommitments()
 	if err != nil {
 		return errors.Wrap(err, "could not get blob kzg commitments")
 	}
-	if len(blobs) != len(proofs) || len(blobs) != len(kzgs) {
-		return errors.New("number of blobs, proofs, and commitments do not match")
+	maxBlobsPerBlock := params.BeaconConfig().MaxBlobsPerBlock(blk.Block().Slot())
+	if len(blobs) > maxBlobsPerBlock {
+		return fmt.Errorf("number of blobs over max, %d > %d", len(blobs), maxBlobsPerBlock)
 	}
-	for i, blob := range blobs {
-		b := kzg4844.Blob(blob)
-		if err := kzg4844.VerifyBlobProof(&b, kzg4844.Commitment(kzgs[i]), kzg4844.Proof(proofs[i])); err != nil {
-			return errors.Wrap(err, "could not verify blob proof")
+	if blk.Version() >= version.Fulu {
+		// For Fulu blocks, proofs are cell proofs (blobs * numberOfColumns)
+		expectedProofsCount := uint64(len(blobs)) * numberOfColumns
+		if uint64(len(proofs)) != expectedProofsCount || len(blobs) != len(commitments) {
+			return fmt.Errorf("number of blobs (%d), cell proofs (%d), and commitments (%d) do not match (expected %d cell proofs)", len(blobs), len(proofs), len(commitments), expectedProofsCount)
+		}
+		// For Fulu blocks, proofs are cell proofs from execution client's BlobsBundleV2
+		// Verify cell proofs directly without reconstructing data column sidecars
+		if err := kzg.VerifyCellKZGProofBatchFromBlobData(blobs, commitments, proofs, numberOfColumns); err != nil {
+			return errors.Wrap(err, "could not verify cell proofs")
+		}
+	} else {
+		// For pre-Fulu blocks, proofs are blob proofs (1:1 with blobs)
+		if len(blobs) != len(proofs) || len(blobs) != len(commitments) {
+			return errors.Errorf("number of blobs (%d), proofs (%d), and commitments (%d) do not match", len(blobs), len(proofs), len(commitments))
+		}
+		// Use batch verification for better performance
+		if err := kzg.VerifyBlobKZGProofBatch(blobs, commitments, proofs); err != nil {
+			return errors.Wrap(err, "could not verify blob proofs")
 		}
 	}
+
 	return nil
 }
 
@@ -1220,7 +1237,7 @@ func (s *Server) GetStateFork(w http.ResponseWriter, r *http.Request) {
 	fork := st.Fork()
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status"+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 	blockRoot, err := st.LatestBlockHeader().HashTreeRoot()
@@ -1331,7 +1348,7 @@ func (s *Server) GetCommittees(w http.ResponseWriter, r *http.Request) {
 
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 
@@ -1512,7 +1529,7 @@ func (s *Server) GetFinalityCheckpoints(w http.ResponseWriter, r *http.Request)
 	}
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 	blockRoot, err := st.LatestBlockHeader().HashTreeRoot()
@@ -1627,6 +1644,8 @@ func (s *Server) broadcastSeenBlockSidecars(
 	if err != nil {
 		return err
 	}
+
+	// Broadcast blob sidecars with forkchoice checking
 	for _, sc := range scs {
 		r, err := sc.SignedBlockHeader.Header.HashTreeRoot()
 		if err != nil {
@@ -1686,7 +1705,7 @@ func (s *Server) GetPendingConsolidations(w http.ResponseWriter, r *http.Request
 	} else {
 		isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 		if err != nil {
-			httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+			helpers.HandleIsOptimisticError(w, err)
 			return
 		}
 		blockRoot, err := st.LatestBlockHeader().HashTreeRoot()
@@ -1742,7 +1761,7 @@ func (s *Server) GetPendingDeposits(w http.ResponseWriter, r *http.Request) {
 	} else {
 		isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 		if err != nil {
-			httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+			helpers.HandleIsOptimisticError(w, err)
 			return
 		}
 		blockRoot, err := st.LatestBlockHeader().HashTreeRoot()
@@ -1798,7 +1817,7 @@ func (s *Server) GetPendingPartialWithdrawals(w http.ResponseWriter, r *http.Req
 	} else {
 		isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 		if err != nil {
-			httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+			helpers.HandleIsOptimisticError(w, err)
 			return
 		}
 		blockRoot, err := st.LatestBlockHeader().HashTreeRoot()
@@ -1851,7 +1870,7 @@ func (s *Server) GetProposerLookahead(w http.ResponseWriter, r *http.Request) {
 	} else {
 		isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 		if err != nil {
-			httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+			helpers.HandleIsOptimisticError(w, err)
 			return
 		}
 		blockRoot, err := st.LatestBlockHeader().HashTreeRoot()

beacon-chain/rpc/eth/beacon/handlers_equivocation_test.go

@@ -0,0 +1,35 @@
+package beacon
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/OffchainLabs/prysm/v6/api/server/structs"
+	rpctesting "github.com/OffchainLabs/prysm/v6/beacon-chain/rpc/eth/shared/testing"
+	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
+	"github.com/OffchainLabs/prysm/v6/testing/require"
+)
+
+// TestBlocks_NewSignedBeaconBlock_EquivocationFix tests that blocks.NewSignedBeaconBlock
+// correctly handles the fixed case where genericBlock.Block is passed instead of genericBlock
+func TestBlocks_NewSignedBeaconBlock_EquivocationFix(t *testing.T) {
+	// Parse the Phase0 JSON block
+	var block structs.SignedBeaconBlock
+	err := json.Unmarshal([]byte(rpctesting.Phase0Block), &block)
+	require.NoError(t, err)
+	
+	// Convert to generic format
+	genericBlock, err := block.ToGeneric()
+	require.NoError(t, err)
+	
+	// Test the FIX: pass genericBlock.Block instead of genericBlock
+	// This is what our fix changed in handlers.go line 704 and 858
+	_, err = blocks.NewSignedBeaconBlock(genericBlock.Block)
+	require.NoError(t, err, "NewSignedBeaconBlock should work with genericBlock.Block")
+	
+	// Test the BROKEN version: pass genericBlock directly (this should fail)
+	_, err = blocks.NewSignedBeaconBlock(genericBlock)
+	if err == nil {
+		t.Errorf("NewSignedBeaconBlock should fail with whole genericBlock but succeeded")
+	}
+}

beacon-chain/rpc/eth/beacon/handlers_state.go

@@ -56,7 +56,7 @@ func (s *Server) GetStateRoot(w http.ResponseWriter, r *http.Request) {
 	}
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 	blockRoot, err := st.LatestBlockHeader().HashTreeRoot()
@@ -125,7 +125,7 @@ func (s *Server) GetRandao(w http.ResponseWriter, r *http.Request) {
 
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 
@@ -227,7 +227,7 @@ func (s *Server) GetSyncCommittees(w http.ResponseWriter, r *http.Request) {
 
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 

beacon-chain/rpc/eth/beacon/handlers_test.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/OffchainLabs/prysm/v6/api"
 	"github.com/OffchainLabs/prysm/v6/api/server/structs"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain/kzg"
 	chainMock "github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain/testing"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/cache/depositsnapshot"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/transition"
@@ -40,7 +41,6 @@ import (
 	"github.com/OffchainLabs/prysm/v6/testing/require"
 	"github.com/OffchainLabs/prysm/v6/testing/util"
 	"github.com/OffchainLabs/prysm/v6/time/slots"
-	GoKZG "github.com/crate-crypto/go-kzg-4844"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/pkg/errors"
 	ssz "github.com/prysmaticlabs/fastssz"
@@ -4781,25 +4781,329 @@ func TestServer_broadcastBlobSidecars(t *testing.T) {
 	require.LogsContain(t, hook, "Broadcasted blob sidecar for already seen block")
 }
 
-func Test_validateBlobSidecars(t *testing.T) {
+func Test_validateBlobs(t *testing.T) {
+	require.NoError(t, kzg.Start())
+
 	blob := util.GetRandBlob(123)
-	commitment := GoKZG.KZGCommitment{180, 218, 156, 194, 59, 20, 10, 189, 186, 254, 132, 93, 7, 127, 104, 172, 238, 240, 237, 70, 83, 89, 1, 152, 99, 0, 165, 65, 143, 62, 20, 215, 230, 14, 205, 95, 28, 245, 54, 25, 160, 16, 178, 31, 232, 207, 38, 85}
-	proof := GoKZG.KZGProof{128, 110, 116, 170, 56, 111, 126, 87, 229, 234, 211, 42, 110, 150, 129, 206, 73, 142, 167, 243, 90, 149, 240, 240, 236, 204, 143, 182, 229, 249, 81, 27, 153, 171, 83, 70, 144, 250, 42, 1, 188, 215, 71, 235, 30, 7, 175, 86}
+	// Generate proper commitment and proof for the blob
+	var kzgBlob kzg.Blob
+	copy(kzgBlob[:], blob[:])
+	commitment, err := kzg.BlobToKZGCommitment(&kzgBlob)
+	require.NoError(t, err)
+	proof, err := kzg.ComputeBlobKZGProof(&kzgBlob, commitment)
+	require.NoError(t, err)
 	blk := util.NewBeaconBlockDeneb()
 	blk.Block.Body.BlobKzgCommitments = [][]byte{commitment[:]}
 	b, err := blocks.NewSignedBeaconBlock(blk)
 	require.NoError(t, err)
 	s := &Server{}
-	require.NoError(t, s.validateBlobSidecars(b, [][]byte{blob[:]}, [][]byte{proof[:]}))
+	require.NoError(t, s.validateBlobs(b, [][]byte{blob[:]}, [][]byte{proof[:]}))
 
-	require.ErrorContains(t, "number of blobs, proofs, and commitments do not match", s.validateBlobSidecars(b, [][]byte{blob[:]}, [][]byte{}))
+	require.ErrorContains(t, "number of blobs (1), proofs (0), and commitments (1) do not match", s.validateBlobs(b, [][]byte{blob[:]}, [][]byte{}))
 
 	sk, err := bls.RandKey()
 	require.NoError(t, err)
 	blk.Block.Body.BlobKzgCommitments = [][]byte{sk.PublicKey().Marshal()}
 	b, err = blocks.NewSignedBeaconBlock(blk)
 	require.NoError(t, err)
-	require.ErrorContains(t, "could not verify blob proof: can't verify opening proof", s.validateBlobSidecars(b, [][]byte{blob[:]}, [][]byte{proof[:]}))
+	require.ErrorContains(t, "could not verify blob proofs", s.validateBlobs(b, [][]byte{blob[:]}, [][]byte{proof[:]}))
+
+	blobs := [][]byte{}
+	commitments := [][]byte{}
+	proofs := [][]byte{}
+	for i := 0; i < 10; i++ {
+		blobs = append(blobs, blob[:])
+		commitments = append(commitments, commitment[:])
+		proofs = append(proofs, proof[:])
+	}
+	t.Run("pre-Deneb block should return early", func(t *testing.T) {
+		// Create a pre-Deneb block (e.g., Capella)
+		blk := util.NewBeaconBlockCapella()
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+		s := &Server{}
+		// Should return nil for pre-Deneb blocks regardless of blobs
+		require.NoError(t, s.validateBlobs(b, [][]byte{}, [][]byte{}))
+		require.NoError(t, s.validateBlobs(b, blobs[:1], proofs[:1]))
+	})
+
+	t.Run("Deneb block with valid single blob", func(t *testing.T) {
+		blk := util.NewBeaconBlockDeneb()
+		blk.Block.Body.BlobKzgCommitments = [][]byte{commitment[:]}
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+		s := &Server{}
+		require.NoError(t, s.validateBlobs(b, [][]byte{blob[:]}, [][]byte{proof[:]}))
+	})
+
+	t.Run("Deneb block with max blobs (6)", func(t *testing.T) {
+		cfg := params.BeaconConfig().Copy()
+		defer params.OverrideBeaconConfig(cfg)
+
+		testCfg := params.BeaconConfig().Copy()
+		testCfg.DenebForkEpoch = 0
+		testCfg.ElectraForkEpoch = 100
+		testCfg.DeprecatedMaxBlobsPerBlock = 6
+		params.OverrideBeaconConfig(testCfg)
+
+		blk := util.NewBeaconBlockDeneb()
+		blk.Block.Slot = 10 // Deneb slot
+		blk.Block.Body.BlobKzgCommitments = commitments[:6]
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+		s := &Server{}
+		// Should pass with exactly 6 blobs
+		require.NoError(t, s.validateBlobs(b, blobs[:6], proofs[:6]))
+	})
+
+	t.Run("Deneb block exceeding max blobs", func(t *testing.T) {
+		cfg := params.BeaconConfig().Copy()
+		defer params.OverrideBeaconConfig(cfg)
+
+		testCfg := params.BeaconConfig().Copy()
+		testCfg.DenebForkEpoch = 0
+		testCfg.ElectraForkEpoch = 100
+		testCfg.DeprecatedMaxBlobsPerBlock = 6
+		params.OverrideBeaconConfig(testCfg)
+
+		blk := util.NewBeaconBlockDeneb()
+		blk.Block.Slot = 10 // Deneb slot
+		blk.Block.Body.BlobKzgCommitments = commitments[:7]
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+		s := &Server{}
+		// Should fail with 7 blobs when max is 6
+		err = s.validateBlobs(b, blobs[:7], proofs[:7])
+		require.ErrorContains(t, "number of blobs over max, 7 > 6", err)
+	})
+
+	t.Run("Electra block with valid blobs", func(t *testing.T) {
+		cfg := params.BeaconConfig().Copy()
+		defer params.OverrideBeaconConfig(cfg)
+
+		// Set up Electra config with max 9 blobs
+		testCfg := params.BeaconConfig().Copy()
+		testCfg.DenebForkEpoch = 0
+		testCfg.ElectraForkEpoch = 5
+		testCfg.DeprecatedMaxBlobsPerBlock = 6
+		testCfg.DeprecatedMaxBlobsPerBlockElectra = 9
+		params.OverrideBeaconConfig(testCfg)
+
+		blk := util.NewBeaconBlockElectra()
+		blk.Block.Slot = 160 // Electra slot (epoch 5+)
+		blk.Block.Body.BlobKzgCommitments = commitments[:9]
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+		s := &Server{}
+		// Should pass with 9 blobs in Electra
+		require.NoError(t, s.validateBlobs(b, blobs[:9], proofs[:9]))
+	})
+
+	t.Run("Electra block exceeding max blobs", func(t *testing.T) {
+		cfg := params.BeaconConfig().Copy()
+		defer params.OverrideBeaconConfig(cfg)
+
+		// Set up Electra config with max 9 blobs
+		testCfg := params.BeaconConfig().Copy()
+		testCfg.DenebForkEpoch = 0
+		testCfg.ElectraForkEpoch = 5
+		testCfg.DeprecatedMaxBlobsPerBlock = 6
+		testCfg.DeprecatedMaxBlobsPerBlockElectra = 9
+		params.OverrideBeaconConfig(testCfg)
+
+		blk := util.NewBeaconBlockElectra()
+		blk.Block.Slot = 160 // Electra slot
+		blk.Block.Body.BlobKzgCommitments = commitments[:10]
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+		s := &Server{}
+		// Should fail with 10 blobs when max is 9
+		err = s.validateBlobs(b, blobs[:10], proofs[:10])
+		require.ErrorContains(t, "number of blobs over max, 10 > 9", err)
+	})
+
+	t.Run("Fulu block with valid cell proofs", func(t *testing.T) {
+		cfg := params.BeaconConfig().Copy()
+		defer params.OverrideBeaconConfig(cfg)
+
+		testCfg := params.BeaconConfig().Copy()
+		testCfg.DenebForkEpoch = 0
+		testCfg.ElectraForkEpoch = 5
+		testCfg.FuluForkEpoch = 10
+		testCfg.DeprecatedMaxBlobsPerBlock = 6
+		testCfg.DeprecatedMaxBlobsPerBlockElectra = 9
+		testCfg.NumberOfColumns = 128 // Standard PeerDAS configuration
+		params.OverrideBeaconConfig(testCfg)
+
+		// Create Fulu block with proper cell proofs
+		blk := util.NewBeaconBlockFulu()
+		blk.Block.Slot = 320 // Epoch 10 (Fulu fork)
+
+		// Generate valid commitments and cell proofs for testing
+		blobCount := 2
+		commitments := make([][]byte, blobCount)
+		fuluBlobs := make([][]byte, blobCount)
+		var kzgBlobs []kzg.Blob
+
+		for i := 0; i < blobCount; i++ {
+			blob := util.GetRandBlob(int64(i))
+			fuluBlobs[i] = blob[:]
+			var kzgBlob kzg.Blob
+			copy(kzgBlob[:], blob[:])
+			kzgBlobs = append(kzgBlobs, kzgBlob)
+
+			// Generate commitment
+			commitment, err := kzg.BlobToKZGCommitment(&kzgBlob)
+			require.NoError(t, err)
+			commitments[i] = commitment[:]
+		}
+
+		blk.Block.Body.BlobKzgCommitments = commitments
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+
+		// Generate cell proofs for the blobs (flattened format like execution client)
+		numberOfColumns := params.BeaconConfig().NumberOfColumns
+		cellProofs := make([][]byte, uint64(blobCount)*numberOfColumns)
+		for blobIdx := 0; blobIdx < blobCount; blobIdx++ {
+			cellsAndProofs, err := kzg.ComputeCellsAndKZGProofs(&kzgBlobs[blobIdx])
+			require.NoError(t, err)
+
+			for colIdx := uint64(0); colIdx < numberOfColumns; colIdx++ {
+				cellProofIdx := uint64(blobIdx)*numberOfColumns + colIdx
+				cellProofs[cellProofIdx] = cellsAndProofs.Proofs[colIdx][:]
+			}
+		}
+
+		s := &Server{}
+		// Should use cell batch verification for Fulu blocks
+		require.NoError(t, s.validateBlobs(b, fuluBlobs, cellProofs))
+	})
+
+	t.Run("Fulu block with invalid cell proof count", func(t *testing.T) {
+		cfg := params.BeaconConfig().Copy()
+		defer params.OverrideBeaconConfig(cfg)
+
+		testCfg := params.BeaconConfig().Copy()
+		testCfg.DenebForkEpoch = 0
+		testCfg.ElectraForkEpoch = 5
+		testCfg.FuluForkEpoch = 10
+		testCfg.NumberOfColumns = 128
+		params.OverrideBeaconConfig(testCfg)
+
+		blk := util.NewBeaconBlockFulu()
+		blk.Block.Slot = 320 // Epoch 10 (Fulu fork)
+
+		// Create valid commitments but wrong number of cell proofs
+		blobCount := 2
+		commitments := make([][]byte, blobCount)
+		fuluBlobs := make([][]byte, blobCount)
+		for i := 0; i < blobCount; i++ {
+			blob := util.GetRandBlob(int64(i))
+			fuluBlobs[i] = blob[:]
+
+			var kzgBlob kzg.Blob
+			copy(kzgBlob[:], blob[:])
+			commitment, err := kzg.BlobToKZGCommitment(&kzgBlob)
+			require.NoError(t, err)
+			commitments[i] = commitment[:]
+		}
+
+		blk.Block.Body.BlobKzgCommitments = commitments
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+
+		// Wrong number of cell proofs (should be blobCount * numberOfColumns)
+		wrongCellProofs := make([][]byte, 10) // Too few proofs
+
+		s := &Server{}
+		err = s.validateBlobs(b, fuluBlobs, wrongCellProofs)
+		require.ErrorContains(t, "do not match", err)
+	})
+
+	t.Run("Deneb block with invalid blob proof", func(t *testing.T) {
+		blob := util.GetRandBlob(123)
+		invalidProof := make([]byte, 48) // All zeros - invalid proof
+
+		sk, err := bls.RandKey()
+		require.NoError(t, err)
+
+		blk := util.NewBeaconBlockDeneb()
+		blk.Block.Body.BlobKzgCommitments = [][]byte{sk.PublicKey().Marshal()}
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+
+		s := &Server{}
+		err = s.validateBlobs(b, [][]byte{blob[:]}, [][]byte{invalidProof})
+		require.ErrorContains(t, "could not verify blob proofs", err)
+	})
+
+	t.Run("empty blobs and proofs should pass", func(t *testing.T) {
+		blk := util.NewBeaconBlockDeneb()
+		blk.Block.Body.BlobKzgCommitments = [][]byte{}
+		b, err := blocks.NewSignedBeaconBlock(blk)
+		require.NoError(t, err)
+
+		s := &Server{}
+		require.NoError(t, s.validateBlobs(b, [][]byte{}, [][]byte{}))
+	})
+
+	t.Run("BlobSchedule with progressive increases (BPO)", func(t *testing.T) {
+		cfg := params.BeaconConfig().Copy()
+		defer params.OverrideBeaconConfig(cfg)
+
+		// Set up config with BlobSchedule (BPO - Blob Production Optimization)
+		testCfg := params.BeaconConfig().Copy()
+		testCfg.DenebForkEpoch = 0
+		testCfg.ElectraForkEpoch = 100
+		testCfg.FuluForkEpoch = 200
+		testCfg.DeprecatedMaxBlobsPerBlock = 6
+		testCfg.DeprecatedMaxBlobsPerBlockElectra = 9
+		// Define blob schedule with progressive increases
+		testCfg.BlobSchedule = []params.BlobScheduleEntry{
+			{Epoch: 0, MaxBlobsPerBlock: 3},  // Start with 3 blobs
+			{Epoch: 10, MaxBlobsPerBlock: 5}, // Increase to 5 at epoch 10
+			{Epoch: 20, MaxBlobsPerBlock: 7}, // Increase to 7 at epoch 20
+			{Epoch: 30, MaxBlobsPerBlock: 9}, // Increase to 9 at epoch 30
+		}
+		params.OverrideBeaconConfig(testCfg)
+
+		s := &Server{}
+
+		// Test epoch 0-9: max 3 blobs
+		t.Run("epoch 0-9: max 3 blobs", func(t *testing.T) {
+			blk := util.NewBeaconBlockDeneb()
+			blk.Block.Slot = 5 // Epoch 0
+			blk.Block.Body.BlobKzgCommitments = commitments[:3]
+			b, err := blocks.NewSignedBeaconBlock(blk)
+			require.NoError(t, err)
+			require.NoError(t, s.validateBlobs(b, blobs[:3], proofs[:3]))
+
+			// Should fail with 4 blobs
+			blk.Block.Body.BlobKzgCommitments = commitments[:4]
+			b, err = blocks.NewSignedBeaconBlock(blk)
+			require.NoError(t, err)
+			err = s.validateBlobs(b, blobs[:4], proofs[:4])
+			require.ErrorContains(t, "number of blobs over max, 4 > 3", err)
+		})
+
+		// Test epoch 30+: max 9 blobs
+		t.Run("epoch 30+: max 9 blobs", func(t *testing.T) {
+			blk := util.NewBeaconBlockDeneb()
+			blk.Block.Slot = 960 // Epoch 30
+			blk.Block.Body.BlobKzgCommitments = commitments[:9]
+			b, err := blocks.NewSignedBeaconBlock(blk)
+			require.NoError(t, err)
+			require.NoError(t, s.validateBlobs(b, blobs[:9], proofs[:9]))
+
+			// Should fail with 10 blobs
+			blk.Block.Body.BlobKzgCommitments = commitments[:10]
+			b, err = blocks.NewSignedBeaconBlock(blk)
+			require.NoError(t, err)
+			err = s.validateBlobs(b, blobs[:10], proofs[:10])
+			require.ErrorContains(t, "number of blobs over max, 10 > 9", err)
+		})
+	})
 }
 
 func TestGetPendingConsolidations(t *testing.T) {

beacon-chain/rpc/eth/beacon/handlers_validator.go

@@ -44,7 +44,7 @@ func (s *Server) GetValidators(w http.ResponseWriter, r *http.Request) {
 
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 	blockRoot, err := st.LatestBlockHeader().HashTreeRoot()
@@ -222,7 +222,7 @@ func (s *Server) GetValidator(w http.ResponseWriter, r *http.Request) {
 
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 	blockRoot, err := st.LatestBlockHeader().HashTreeRoot()
@@ -258,7 +258,7 @@ func (s *Server) GetValidatorBalances(w http.ResponseWriter, r *http.Request) {
 
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 	blockRoot, err := st.LatestBlockHeader().HashTreeRoot()
@@ -419,7 +419,7 @@ func (s *Server) getValidatorIdentitiesJSON(
 ) {
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateId), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 	blockRoot, err := st.LatestBlockHeader().HashTreeRoot()

beacon-chain/rpc/eth/debug/handlers.go

@@ -46,7 +46,7 @@ func (s *Server) getBeaconStateV2(ctx context.Context, w http.ResponseWriter, id
 
 	isOptimistic, err := helpers.IsOptimistic(ctx, id, s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		httputil.HandleError(w, "Could not check if state is optimistic: "+err.Error(), http.StatusInternalServerError)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 	blockRoot, err := st.LatestBlockHeader().HashTreeRoot()

beacon-chain/rpc/eth/helpers/BUILD.bazel

@@ -12,6 +12,7 @@ go_library(
     deps = [
         "//beacon-chain/blockchain:go_default_library",
         "//beacon-chain/db:go_default_library",
+        "//beacon-chain/rpc/eth/shared:go_default_library",
         "//beacon-chain/rpc/lookup:go_default_library",
         "//beacon-chain/state:go_default_library",
         "//beacon-chain/state/stategen:go_default_library",
@@ -21,6 +22,7 @@ go_library(
         "//consensus-types/primitives:go_default_library",
         "//consensus-types/validator:go_default_library",
         "//encoding/bytesutil:go_default_library",
+        "//network/httputil:go_default_library",
         "//time/slots:go_default_library",
         "@com_github_ethereum_go_ethereum//common/hexutil:go_default_library",
         "@com_github_pkg_errors//:go_default_library",
@@ -40,6 +42,7 @@ go_test(
         "//beacon-chain/blockchain/testing:go_default_library",
         "//beacon-chain/db/testing:go_default_library",
         "//beacon-chain/forkchoice/doubly-linked-tree:go_default_library",
+        "//beacon-chain/rpc/lookup:go_default_library",
         "//beacon-chain/rpc/testutil:go_default_library",
         "//beacon-chain/state:go_default_library",
         "//beacon-chain/state/state-native:go_default_library",
@@ -57,5 +60,6 @@ go_test(
         "//testing/require:go_default_library",
         "//testing/util:go_default_library",
         "@com_github_ethereum_go_ethereum//common/hexutil:go_default_library",
+        "@com_github_pkg_errors//:go_default_library",
     ],
 )

beacon-chain/rpc/eth/helpers/error_handling.go

@@ -2,11 +2,14 @@ package helpers
 
 import (
 	"errors"
+	"net/http"
 
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/rpc/eth/shared"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/rpc/lookup"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/state/stategen"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/interfaces"
+	"github.com/OffchainLabs/prysm/v6/network/httputil"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )
@@ -28,6 +31,22 @@ func PrepareStateFetchGRPCError(err error) error {
 	return status.Errorf(codes.Internal, "Invalid state ID: %v", err)
 }
 
+// HandleIsOptimisticError handles errors from IsOptimistic function calls and writes appropriate HTTP responses.
+func HandleIsOptimisticError(w http.ResponseWriter, err error) {
+	var fetchErr *lookup.FetchStateError
+	if errors.As(err, &fetchErr) {
+		shared.WriteStateFetchError(w, err)
+		return
+	}
+
+	var blockRootsNotFoundErr *lookup.BlockRootsNotFoundError
+	if errors.As(err, &blockRootsNotFoundErr) {
+		httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusNotFound)
+		return
+	}
+	httputil.HandleError(w, "Could not check optimistic status: "+err.Error(), http.StatusInternalServerError)
+}
+
 // IndexedVerificationFailure represents a collection of verification failures.
 type IndexedVerificationFailure struct {
 	Failures []*SingleIndexedVerificationFailure `json:"failures"`

beacon-chain/rpc/eth/helpers/sync.go

@@ -56,7 +56,8 @@ func IsOptimistic(
 		if bytesutil.IsHex(stateId) {
 			id, err := hexutil.Decode(stateIdString)
 			if err != nil {
-				return false, err
+				e := lookup.NewStateIdParseError(err)
+				return false, &e
 			}
 			return isStateRootOptimistic(ctx, id, optimisticModeFetcher, stateFetcher, chainInfo, database)
 		} else if len(stateId) == 32 {
@@ -127,7 +128,7 @@ func isStateRootOptimistic(
 ) (bool, error) {
 	st, err := stateFetcher.State(ctx, stateId)
 	if err != nil {
-		return true, errors.Wrap(err, "could not fetch state")
+		return true, lookup.NewFetchStateError(err)
 	}
 	if st.Slot() == chainInfo.HeadSlot() {
 		return optimisticModeFetcher.IsOptimistic(ctx)
@@ -137,7 +138,7 @@ func isStateRootOptimistic(
 		return true, errors.Wrapf(err, "could not get block roots for slot %d", st.Slot())
 	}
 	if !has {
-		return true, errors.New("no block roots returned from the database")
+		return true, lookup.NewBlockRootsNotFoundError()
 	}
 	for _, r := range roots {
 		b, err := database.Block(ctx, r)

beacon-chain/rpc/eth/helpers/sync_test.go

@@ -1,12 +1,15 @@
 package helpers
 
 import (
+	"net/http"
+	"net/http/httptest"
 	"strconv"
 	"testing"
 
 	chainmock "github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain/testing"
 	dbtest "github.com/OffchainLabs/prysm/v6/beacon-chain/db/testing"
 	doublylinkedtree "github.com/OffchainLabs/prysm/v6/beacon-chain/forkchoice/doubly-linked-tree"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/rpc/lookup"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/rpc/testutil"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/state"
 	state_native "github.com/OffchainLabs/prysm/v6/beacon-chain/state/state-native"
@@ -21,6 +24,7 @@ import (
 	"github.com/OffchainLabs/prysm/v6/testing/require"
 	"github.com/OffchainLabs/prysm/v6/testing/util"
 	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/pkg/errors"
 )
 
 func TestIsOptimistic(t *testing.T) {
@@ -226,7 +230,67 @@ func TestIsOptimistic(t *testing.T) {
 			require.NoError(t, err)
 			assert.Equal(t, true, o)
 		})
+		t.Run("State not found", func(t *testing.T) {
+			b, err := blocks.NewSignedBeaconBlock(util.NewBeaconBlock())
+			require.NoError(t, err)
+			b.SetStateRoot(bytesutil.PadTo([]byte("root"), 32))
+			db := dbtest.SetupDB(t)
+			require.NoError(t, db.SaveBlock(ctx, b))
+			chainSt, err := util.NewBeaconState()
+			require.NoError(t, err)
+			require.NoError(t, chainSt.SetSlot(fieldparams.SlotsPerEpoch))
+			bRoot, err := b.Block().HashTreeRoot()
+			require.NoError(t, err)
+			cs := &chainmock.ChainService{State: chainSt, OptimisticRoots: map[[32]byte]bool{bRoot: true}}
+			mf := &testutil.MockStater{
+				CustomError: lookup.NewFetchStateError(nil),
+			}
+			_, err = IsOptimistic(ctx, []byte(hexutil.Encode(bytesutil.PadTo([]byte("root"), 32))), cs, mf, cs, db)
+			var fetchErr *lookup.FetchStateError
+			require.Equal(t, true, errors.As(err, &fetchErr))
+		})
+
+		t.Run("stateId invalid", func(t *testing.T) {
+			b, err := blocks.NewSignedBeaconBlock(util.NewBeaconBlock())
+			require.NoError(t, err)
+			b.SetStateRoot(bytesutil.PadTo([]byte("root"), 32))
+			db := dbtest.SetupDB(t)
+			require.NoError(t, db.SaveBlock(ctx, b))
+			chainSt, err := util.NewBeaconState()
+			require.NoError(t, err)
+			require.NoError(t, chainSt.SetSlot(fieldparams.SlotsPerEpoch))
+			bRoot, err := b.Block().HashTreeRoot()
+			require.NoError(t, err)
+			cs := &chainmock.ChainService{State: chainSt, OptimisticRoots: map[[32]byte]bool{bRoot: true}}
+			mf := &testutil.MockStater{
+				CustomError: lookup.NewFetchStateError(nil),
+			}
+			_, err = IsOptimistic(ctx, []byte("0xabc"), cs, mf, cs, db)
+			var fetchErr *lookup.FetchStateError
+			require.Equal(t, false, errors.As(err, &fetchErr))
+		})
+		t.Run("block roots not found", func(t *testing.T) {
+			b, err := blocks.NewSignedBeaconBlock(util.NewBeaconBlock())
+			require.NoError(t, err)
+			b.SetStateRoot(bytesutil.PadTo([]byte("root"), 32))
+			db := dbtest.SetupDB(t)
+			require.NoError(t, db.SaveBlock(ctx, b))
+			chainSt, err := util.NewBeaconState()
+			require.NoError(t, err)
+			require.NoError(t, chainSt.SetSlot(fieldparams.SlotsPerEpoch))
+			bRoot, err := b.Block().HashTreeRoot()
+			require.NoError(t, err)
+			cs := &chainmock.ChainService{State: chainSt, OptimisticRoots: map[[32]byte]bool{bRoot: true}}
+			st, err := util.NewBeaconState()
+			require.NoError(t, st.SetSlot(primitives.Slot(fieldparams.SlotsPerEpoch+1)))
+			require.NoError(t, err)
+			mf := &testutil.MockStater{BeaconState: st}
+			_, err = IsOptimistic(ctx, []byte(hexutil.Encode(bytesutil.PadTo([]byte("root"), 32))), cs, mf, cs, db)
+			var blockRootsNotFoundErr *lookup.BlockRootsNotFoundError
+			require.Equal(t, true, errors.As(err, &blockRootsNotFoundErr))
+		})
 	})
+
 	t.Run("slot", func(t *testing.T) {
 		t.Run("head is not optimistic", func(t *testing.T) {
 			cs := &chainmock.ChainService{Optimistic: false}
@@ -319,6 +383,36 @@ func TestIsOptimistic(t *testing.T) {
 	})
 }
 
+func TestHandleIsOptimisticError(t *testing.T) {
+	t.Run("fetch-state error handled as 404", func(t *testing.T) {
+		rr := httptest.NewRecorder()
+		notFoundErr := lookup.StateNotFoundError{}
+		fetchErr := lookup.NewFetchStateError(&notFoundErr)
+		HandleIsOptimisticError(rr, fetchErr)
+
+		require.Equal(t, http.StatusNotFound, rr.Code)
+		require.StringContains(t, notFoundErr.Error(), rr.Body.String())
+	})
+	t.Run("no block roots error handled as 404", func(t *testing.T) {
+		rr := httptest.NewRecorder()
+		blockRootsErr := lookup.NewBlockRootsNotFoundError()
+		HandleIsOptimisticError(rr, blockRootsErr)
+
+		require.Equal(t, http.StatusNotFound, rr.Code)
+		require.StringContains(t, blockRootsErr.Error(), rr.Body.String())
+	})
+
+	t.Run("generic error handled as 500", func(t *testing.T) {
+		rr := httptest.NewRecorder()
+		genericErr := errors.New("boom")
+
+		HandleIsOptimisticError(rr, genericErr)
+
+		require.Equal(t, http.StatusInternalServerError, rr.Code)
+		require.StringContains(t, "Could not check optimistic status: boom", rr.Body.String())
+	})
+}
+
 // prepareForkchoiceState prepares a beacon state with the given data to mock
 // insert into forkchoice
 func prepareForkchoiceState(

beacon-chain/rpc/lookup/blocker.go

@@ -23,6 +23,20 @@ import (
 	"github.com/pkg/errors"
 )
 
+type BlockRootsNotFoundError struct {
+	message string
+}
+
+func NewBlockRootsNotFoundError() *BlockRootsNotFoundError {
+	return &BlockRootsNotFoundError{
+		message: "no block roots returned from the database",
+	}
+}
+
+func (e BlockRootsNotFoundError) Error() string {
+	return e.message
+}
+
 // BlockIdParseError represents an error scenario where a block ID could not be parsed.
 type BlockIdParseError struct {
 	message string
@@ -341,7 +355,7 @@ func (p *BeaconDbBlocker) blobsFromStoredDataColumns(block blocks.ROBlock, indic
 	stored := summary.Stored()
 	count := uint64(len(stored))
 
-	if count < peerdas.MinimumColumnsCountToReconstruct() {
+	if count < peerdas.MinimumColumnCountToReconstruct() {
 		// There is no way to reconstruct the data columns.
 		return nil, &core.RpcError{
 			Err:    errors.Errorf("the node does not custody enough data columns to reconstruct blobs - please start the beacon node with the `--%s` flag to ensure this call to succeed, or retry later if it is already the case", flags.SubscribeAllDataSubnets.Name),

beacon-chain/rpc/lookup/blocker_test.go

@@ -443,7 +443,7 @@ func TestGetBlob(t *testing.T) {
 		setupFulu(t)
 
 		_, dataColumnStorage := filesystem.NewEphemeralDataColumnStorageAndFs(t)
-		err = dataColumnStorage.Save(verifiedRoDataColumnSidecars[1 : peerdas.MinimumColumnsCountToReconstruct()+1])
+		err = dataColumnStorage.Save(verifiedRoDataColumnSidecars[1 : peerdas.MinimumColumnCountToReconstruct()+1])
 		require.NoError(t, err)
 
 		blocker := &BeaconDbBlocker{

beacon-chain/rpc/lookup/stater.go

@@ -21,6 +21,27 @@ import (
 	"github.com/pkg/errors"
 )
 
+type FetchStateError struct {
+	message string
+	cause   error
+}
+
+func NewFetchStateError(cause error) *FetchStateError {
+	return &FetchStateError{
+		message: "could not fetch state",
+		cause:   cause,
+	}
+}
+
+func (e *FetchStateError) Error() string {
+	if e.cause != nil {
+		return e.message + ": " + e.cause.Error()
+	}
+	return e.message
+}
+
+func (e *FetchStateError) Unwrap() error { return e.cause }
+
 // StateIdParseError represents an error scenario where a state ID could not be parsed.
 type StateIdParseError struct {
 	message string

beacon-chain/rpc/prysm/beacon/validator_count.go

@@ -56,11 +56,7 @@ func (s *Server) GetValidatorCount(w http.ResponseWriter, r *http.Request) {
 
 	isOptimistic, err := helpers.IsOptimistic(ctx, []byte(stateID), s.OptimisticModeFetcher, s.Stater, s.ChainInfoFetcher, s.BeaconDB)
 	if err != nil {
-		errJson := &httputil.DefaultJsonError{
-			Message: fmt.Sprintf("could not check if slot's block is optimistic: %v", err),
-			Code:    http.StatusInternalServerError,
-		}
-		httputil.WriteError(w, errJson)
+		helpers.HandleIsOptimisticError(w, err)
 		return
 	}
 

beacon-chain/rpc/prysm/v1alpha1/validator/BUILD.bazel

@@ -1,3 +1,5 @@
+# gazelle:ignore
+
 load("@prysm//tools/go:def.bzl", "go_library", "go_test")
 
 go_library(
@@ -37,6 +39,7 @@ go_library(
         "//api/client/builder:go_default_library",
         "//async/event:go_default_library",
         "//beacon-chain/blockchain:go_default_library",
+        "//beacon-chain/blockchain/kzg:go_default_library",
         "//beacon-chain/builder:go_default_library",
         "//beacon-chain/cache:go_default_library",
         "//beacon-chain/cache/depositsnapshot:go_default_library",
@@ -47,6 +50,7 @@ go_library(
         "//beacon-chain/core/feed/operation:go_default_library",
         "//beacon-chain/core/feed/state:go_default_library",
         "//beacon-chain/core/helpers:go_default_library",
+        "//beacon-chain/core/peerdas:go_default_library",
         "//beacon-chain/core/signing:go_default_library",
         "//beacon-chain/core/time:go_default_library",
         "//beacon-chain/core/transition:go_default_library",
@@ -63,8 +67,8 @@ go_library(
         "//beacon-chain/rpc/core:go_default_library",
         "//beacon-chain/startup:go_default_library",
         "//beacon-chain/state:go_default_library",
-        "//beacon-chain/state/stategen:go_default_library",
         "//beacon-chain/state/state-native:go_default_library",
+        "//beacon-chain/state/stategen:go_default_library",
         "//beacon-chain/sync:go_default_library",
         "//config/features:go_default_library",
         "//config/fieldparams:go_default_library",
@@ -81,7 +85,7 @@ go_library(
         "//crypto/rand:go_default_library",
         "//encoding/bytesutil:go_default_library",
         "//encoding/ssz:go_default_library",
-	"//genesis:go_default_library",
+        "//genesis:go_default_library",
         "//math:go_default_library",
         "//monitoring/tracing:go_default_library",
         "//monitoring/tracing/trace:go_default_library",
@@ -181,7 +185,6 @@ common_deps = [
     "@org_golang_google_protobuf//types/known/emptypb:go_default_library",
 ]
 
-# gazelle:ignore
 go_test(
     name = "go_default_test",
     timeout = "moderate",

beacon-chain/rpc/prysm/v1alpha1/validator/blocks.go

@@ -248,6 +248,8 @@ func (vs *Server) sendBlocks(stream ethpb.BeaconNodeValidator_StreamBlocksAltair
 		b.Block = &ethpb.StreamBlocksResponse_DenebBlock{DenebBlock: p}
 	case *ethpb.SignedBeaconBlockElectra:
 		b.Block = &ethpb.StreamBlocksResponse_ElectraBlock{ElectraBlock: p}
+	case *ethpb.SignedBeaconBlockFulu:
+		b.Block = &ethpb.StreamBlocksResponse_FuluBlock{FuluBlock: p}
 	default:
 		log.Errorf("Unknown block type %T", p)
 	}

beacon-chain/rpc/prysm/v1alpha1/validator/blocks_test.go

@@ -381,3 +381,92 @@ func TestServer_StreamSlotsVerified_OnHeadUpdated(t *testing.T) {
 	}
 	<-exitRoutine
 }
+
+func TestServer_StreamBlocksVerified_FuluBlock(t *testing.T) {
+	db := dbTest.SetupDB(t)
+	ctx := t.Context()
+	beaconState, privs := util.DeterministicGenesisStateFulu(t, 32)
+	c, err := altair.NextSyncCommittee(ctx, beaconState)
+	require.NoError(t, err)
+	require.NoError(t, beaconState.SetCurrentSyncCommittee(c))
+
+	b, err := util.GenerateFullBlockFulu(beaconState, privs, util.DefaultBlockGenConfig(), 1)
+	require.NoError(t, err)
+	r, err := b.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wrappedBlk := util.SaveBlock(t, ctx, db, b)
+	chainService := &chainMock.ChainService{State: beaconState}
+	server := &Server{
+		Ctx:           ctx,
+		StateNotifier: chainService.StateNotifier(),
+		HeadFetcher:   chainService,
+	}
+	exitRoutine := make(chan bool)
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+	mockStream := mock.NewMockBeaconNodeValidatorAltair_StreamBlocksServer(ctrl)
+	mockStream.EXPECT().Send(&ethpb.StreamBlocksResponse{Block: &ethpb.StreamBlocksResponse_FuluBlock{FuluBlock: b}}).Do(func(arg0 interface{}) {
+		exitRoutine <- true
+	})
+	mockStream.EXPECT().Context().Return(ctx).AnyTimes()
+
+	go func(tt *testing.T) {
+		err := server.StreamBlocksAltair(&ethpb.StreamBlocksRequest{VerifiedOnly: true}, mockStream)
+		if s, _ := status.FromError(err); s.Code() != codes.Canceled {
+			assert.NoError(tt, err)
+		}
+	}(t)
+	// Send in a loop to ensure it is delivered (busy wait for the service to subscribe to the state feed).
+	for sent := 0; sent == 0; {
+		sent = server.StateNotifier.StateFeed().Send(&feed.Event{
+			Type: statefeed.BlockProcessed,
+			Data: &statefeed.BlockProcessedData{Slot: b.Block.Slot, BlockRoot: r, SignedBlock: wrappedBlk},
+		})
+	}
+	<-exitRoutine
+}
+
+func TestServer_StreamBlocks_FuluBlock(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	params.OverrideBeaconConfig(params.BeaconConfig())
+	ctx := t.Context()
+	beaconState, privs := util.DeterministicGenesisStateFulu(t, 64)
+	c, err := altair.NextSyncCommittee(ctx, beaconState)
+	require.NoError(t, err)
+	require.NoError(t, beaconState.SetCurrentSyncCommittee(c))
+
+	b, err := util.GenerateFullBlockFulu(beaconState, privs, util.DefaultBlockGenConfig(), 1)
+	require.NoError(t, err)
+	chainService := &chainMock.ChainService{State: beaconState}
+	server := &Server{
+		Ctx:           ctx,
+		BlockNotifier: chainService.BlockNotifier(),
+		HeadFetcher:   chainService,
+	}
+	exitRoutine := make(chan bool)
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+	mockStream := mock.NewMockBeaconNodeValidatorAltair_StreamBlocksServer(ctrl)
+
+	mockStream.EXPECT().Send(&ethpb.StreamBlocksResponse{Block: &ethpb.StreamBlocksResponse_FuluBlock{FuluBlock: b}}).Do(func(arg0 interface{}) {
+		exitRoutine <- true
+	})
+	mockStream.EXPECT().Context().Return(ctx).AnyTimes()
+
+	go func(tt *testing.T) {
+		err := server.StreamBlocksAltair(&ethpb.StreamBlocksRequest{}, mockStream)
+		if s, _ := status.FromError(err); s.Code() != codes.Canceled {
+			assert.NoError(tt, err)
+		}
+	}(t)
+	wrappedBlk, err := blocks.NewSignedBeaconBlock(b)
+	require.NoError(t, err)
+	// Send in a loop to ensure it is delivered (busy wait for the service to subscribe to the state feed).
+	for sent := 0; sent == 0; {
+		sent = server.BlockNotifier.BlockFeed().Send(&feed.Event{
+			Type: blockfeed.ReceivedBlock,
+			Data: &blockfeed.ReceivedBlockData{SignedBlock: wrappedBlk},
+		})
+	}
+	<-exitRoutine
+}

beacon-chain/rpc/prysm/v1alpha1/validator/construct_generic_block_test.go

@@ -29,12 +29,19 @@ func TestConstructGenericBeaconBlock(t *testing.T) {
 		require.NoError(t, err)
 		r1, err := eb.Block.HashTreeRoot()
 		require.NoError(t, err)
-		result, err := vs.constructGenericBeaconBlock(b, nil, primitives.ZeroWei())
+		bundle := &enginev1.BlobsBundleV2{
+			KzgCommitments: [][]byte{{1, 2, 3}},
+			Proofs:         [][]byte{{4, 5, 6}},
+			Blobs:          [][]byte{{7, 8, 9}},
+		}
+		result, err := vs.constructGenericBeaconBlock(b, bundle, primitives.ZeroWei())
 		require.NoError(t, err)
 		r2, err := result.GetFulu().Block.HashTreeRoot()
 		require.NoError(t, err)
 		require.Equal(t, r1, r2)
 		require.Equal(t, result.IsBlinded, false)
+		require.DeepEqual(t, bundle.Blobs, result.GetFulu().GetBlobs())
+		require.DeepEqual(t, bundle.Proofs, result.GetFulu().GetKzgProofs())
 	})
 
 	// Test for Electra version

beacon-chain/rpc/prysm/v1alpha1/validator/proposer.go

@@ -15,9 +15,12 @@ import (
 	blockfeed "github.com/OffchainLabs/prysm/v6/beacon-chain/core/feed/block"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/feed/operation"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/helpers"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/peerdas"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/transition"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/kv"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/state"
+	"github.com/OffchainLabs/prysm/v6/config/features"
+	fieldparams "github.com/OffchainLabs/prysm/v6/config/fieldparams"
 	"github.com/OffchainLabs/prysm/v6/config/params"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/interfaces"
@@ -58,28 +61,31 @@ func (vs *Server) GetBeaconBlock(ctx context.Context, req *ethpb.BlockRequest) (
 	if err != nil {
 		log.WithError(err).Error("Could not convert slot to time")
 	}
-	log.WithFields(logrus.Fields{
-		"slot":               req.Slot,
-		"sinceSlotStartTime": time.Since(t),
-	}).Info("Begin building block")
+
+	log := log.WithField("slot", req.Slot)
+	log.WithField("sinceSlotStartTime", time.Since(t)).Info("Begin building block")
 
 	// A syncing validator should not produce a block.
 	if vs.SyncChecker.Syncing() {
+		log.Error("Fail to build block: node is syncing")
 		return nil, status.Error(codes.Unavailable, "Syncing to latest head, not ready to respond")
 	}
 	// An optimistic validator MUST NOT produce a block (i.e., sign across the DOMAIN_BEACON_PROPOSER domain).
 	if slots.ToEpoch(req.Slot) >= params.BeaconConfig().BellatrixForkEpoch {
 		if err := vs.optimisticStatus(ctx); err != nil {
+			log.WithError(err).Error("Fail to build block: node is optimistic")
 			return nil, status.Errorf(codes.Unavailable, "Validator is not ready to propose: %v", err)
 		}
 	}
 
 	head, parentRoot, err := vs.getParentState(ctx, req.Slot)
 	if err != nil {
+		log.WithError(err).Error("Fail to build block: could not get parent state")
 		return nil, err
 	}
 	sBlk, err := getEmptyBlock(req.Slot)
 	if err != nil {
+		log.WithError(err).Error("Fail to build block: could not get empty block")
 		return nil, status.Errorf(codes.Internal, "Could not prepare block: %v", err)
 	}
 	// Set slot, graffiti, randao reveal, and parent root.
@@ -101,8 +107,7 @@ func (vs *Server) GetBeaconBlock(ctx context.Context, req *ethpb.BlockRequest) (
 	}
 
 	resp, err := vs.BuildBlockParallel(ctx, sBlk, head, req.SkipMevBoost, builderBoostFactor)
-	log := log.WithFields(logrus.Fields{
-		"slot":               req.Slot,
+	log = log.WithFields(logrus.Fields{
 		"sinceSlotStartTime": time.Since(t),
 		"validator":          sBlk.Block().ProposerIndex(),
 	})
@@ -275,6 +280,11 @@ func (vs *Server) BuildBlockParallel(ctx context.Context, sBlk interfaces.Signed
 //
 // ProposeBeaconBlock handles the proposal of beacon blocks.
 func (vs *Server) ProposeBeaconBlock(ctx context.Context, req *ethpb.GenericSignedBeaconBlock) (*ethpb.ProposeResponse, error) {
+	var (
+		blobSidecars       []*ethpb.BlobSidecar
+		dataColumnSidecars []*ethpb.DataColumnSidecar
+	)
+
 	ctx, span := trace.StartSpan(ctx, "ProposerServer.ProposeBeaconBlock")
 	defer span.End()
 
@@ -287,24 +297,31 @@ func (vs *Server) ProposeBeaconBlock(ctx context.Context, req *ethpb.GenericSign
 		return nil, status.Errorf(codes.InvalidArgument, "%s: %v", "decode block failed", err)
 	}
 
-	var sidecars []*ethpb.BlobSidecar
-	if block.IsBlinded() {
-		block, sidecars, err = vs.handleBlindedBlock(ctx, block)
-	} else if block.Version() >= version.Deneb {
-		sidecars, err = vs.blobSidecarsFromUnblindedBlock(block, req)
-	}
-	if err != nil {
-		return nil, status.Errorf(codes.Internal, "%s: %v", "handle block failed", err)
-	}
-
 	root, err := block.Block().HashTreeRoot()
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "Could not hash tree root: %v", err)
 	}
 
+	// For post-Fulu blinded blocks, submit to relay and return early
+	if block.IsBlinded() && slots.ToEpoch(block.Block().Slot()) >= params.BeaconConfig().FuluForkEpoch {
+		err := vs.BlockBuilder.SubmitBlindedBlockPostFulu(ctx, block)
+		if err != nil {
+			return nil, status.Errorf(codes.Internal, "Could not submit blinded block post-Fulu: %v", err)
+		}
+		return &ethpb.ProposeResponse{BlockRoot: root[:]}, nil
+	}
+
+	if block.IsBlinded() {
+		block, blobSidecars, err = vs.handleBlindedBlock(ctx, block)
+	} else if block.Version() >= version.Deneb {
+		blobSidecars, dataColumnSidecars, err = vs.handleUnblindedBlock(block, req)
+	}
+	if err != nil {
+		return nil, status.Errorf(codes.Internal, "%s: %v", "handle block failed", err)
+	}
+
 	var wg sync.WaitGroup
 	errChan := make(chan error, 1)
-
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
@@ -315,10 +332,9 @@ func (vs *Server) ProposeBeaconBlock(ctx context.Context, req *ethpb.GenericSign
 		errChan <- nil
 	}()
 
-	if err := vs.broadcastAndReceiveBlobs(ctx, sidecars, root); err != nil {
-		return nil, status.Errorf(codes.Internal, "Could not broadcast/receive blobs: %v", err)
+	if err := vs.broadcastAndReceiveSidecars(ctx, block, root, blobSidecars, dataColumnSidecars); err != nil {
+		return nil, status.Errorf(codes.Internal, "Could not broadcast/receive sidecars: %v", err)
 	}
-
 	wg.Wait()
 	if err := <-errChan; err != nil {
 		return nil, status.Errorf(codes.Internal, "Could not broadcast/receive block: %v", err)
@@ -327,11 +343,35 @@ func (vs *Server) ProposeBeaconBlock(ctx context.Context, req *ethpb.GenericSign
 	return &ethpb.ProposeResponse{BlockRoot: root[:]}, nil
 }
 
-// handleBlindedBlock processes blinded beacon blocks.
+// broadcastAndReceiveSidecars broadcasts and receives sidecars.
+func (vs *Server) broadcastAndReceiveSidecars(
+	ctx context.Context,
+	block interfaces.SignedBeaconBlock,
+	root [fieldparams.RootLength]byte,
+	blobSidecars []*ethpb.BlobSidecar,
+	dataColumnSideCars []*ethpb.DataColumnSidecar,
+) error {
+	if block.Version() >= version.Fulu {
+		if err := vs.broadcastAndReceiveDataColumns(ctx, dataColumnSideCars, root, block.Block().Slot()); err != nil {
+			return errors.Wrap(err, "broadcast and receive data columns")
+		}
+		return nil
+	}
+
+	if err := vs.broadcastAndReceiveBlobs(ctx, blobSidecars, root); err != nil {
+		return errors.Wrap(err, "broadcast and receive blobs")
+	}
+
+	return nil
+}
+
+// handleBlindedBlock processes blinded beacon blocks (pre-Fulu only).
+// Post-Fulu blinded blocks are handled directly in ProposeBeaconBlock.
 func (vs *Server) handleBlindedBlock(ctx context.Context, block interfaces.SignedBeaconBlock) (interfaces.SignedBeaconBlock, []*ethpb.BlobSidecar, error) {
 	if block.Version() < version.Bellatrix {
 		return nil, nil, errors.New("pre-Bellatrix blinded block")
 	}
+
 	if vs.BlockBuilder == nil || !vs.BlockBuilder.Configured() {
 		return nil, nil, errors.New("unconfigured block builder")
 	}
@@ -358,16 +398,34 @@ func (vs *Server) handleBlindedBlock(ctx context.Context, block interfaces.Signe
 	return copiedBlock, sidecars, nil
 }
 
-func (vs *Server) blobSidecarsFromUnblindedBlock(block interfaces.SignedBeaconBlock, req *ethpb.GenericSignedBeaconBlock) ([]*ethpb.BlobSidecar, error) {
+func (vs *Server) handleUnblindedBlock(
+	block interfaces.SignedBeaconBlock,
+	req *ethpb.GenericSignedBeaconBlock,
+) ([]*ethpb.BlobSidecar, []*ethpb.DataColumnSidecar, error) {
 	rawBlobs, proofs, err := blobsAndProofs(req)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
-	return BuildBlobSidecars(block, rawBlobs, proofs)
+
+	if block.Version() >= version.Fulu {
+		dataColumnSideCars, err := peerdas.ConstructDataColumnSidecars(block, rawBlobs, proofs)
+		if err != nil {
+			return nil, nil, errors.Wrap(err, "construct data column sidecars")
+		}
+
+		return nil, dataColumnSideCars, nil
+	}
+
+	blobSidecars, err := BuildBlobSidecars(block, rawBlobs, proofs)
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "build blob sidecars")
+	}
+
+	return blobSidecars, nil, nil
 }
 
 // broadcastReceiveBlock broadcasts a block and handles its reception.
-func (vs *Server) broadcastReceiveBlock(ctx context.Context, block interfaces.SignedBeaconBlock, root [32]byte) error {
+func (vs *Server) broadcastReceiveBlock(ctx context.Context, block interfaces.SignedBeaconBlock, root [fieldparams.RootLength]byte) error {
 	protoBlock, err := block.Proto()
 	if err != nil {
 		return errors.Wrap(err, "protobuf conversion failed")
@@ -383,18 +441,14 @@ func (vs *Server) broadcastReceiveBlock(ctx context.Context, block interfaces.Si
 }
 
 // broadcastAndReceiveBlobs handles the broadcasting and reception of blob sidecars.
-func (vs *Server) broadcastAndReceiveBlobs(ctx context.Context, sidecars []*ethpb.BlobSidecar, root [32]byte) error {
+func (vs *Server) broadcastAndReceiveBlobs(ctx context.Context, sidecars []*ethpb.BlobSidecar, root [fieldparams.RootLength]byte) error {
 	eg, eCtx := errgroup.WithContext(ctx)
-	for i, sc := range sidecars {
-		// Copy the iteration instance to a local variable to give each go-routine its own copy to play with.
-		// See https://golang.org/doc/faq#closures_and_goroutines for more details.
-		subIdx := i
-		sCar := sc
+	for subIdx, sc := range sidecars {
 		eg.Go(func() error {
-			if err := vs.P2P.BroadcastBlob(eCtx, uint64(subIdx), sCar); err != nil {
+			if err := vs.P2P.BroadcastBlob(eCtx, uint64(subIdx), sc); err != nil {
 				return errors.Wrap(err, "broadcast blob failed")
 			}
-			readOnlySc, err := blocks.NewROBlobWithRoot(sCar, root)
+			readOnlySc, err := blocks.NewROBlobWithRoot(sc, root)
 			if err != nil {
 				return errors.Wrap(err, "ROBlob creation failed")
 			}
@@ -412,6 +466,69 @@ func (vs *Server) broadcastAndReceiveBlobs(ctx context.Context, sidecars []*ethp
 	return eg.Wait()
 }
 
+// broadcastAndReceiveDataColumns handles the broadcasting and reception of data columns sidecars.
+func (vs *Server) broadcastAndReceiveDataColumns(
+	ctx context.Context,
+	sidecars []*ethpb.DataColumnSidecar,
+	root [fieldparams.RootLength]byte,
+	slot primitives.Slot,
+) error {
+	dataColumnsWithholdCount := features.Get().DataColumnsWithholdCount
+	verifiedRODataColumns := make([]blocks.VerifiedRODataColumn, 0, len(sidecars))
+
+	eg, _ := errgroup.WithContext(ctx)
+	for _, sd := range sidecars {
+		roDataColumn, err := blocks.NewRODataColumnWithRoot(sd, root)
+		if err != nil {
+			return errors.Wrap(err, "new read-only data column with root")
+		}
+
+		// We build this block ourselves, so we can upgrade the read only data column sidecar into a verified one.
+		verifiedRODataColumn := blocks.NewVerifiedRODataColumn(roDataColumn)
+		verifiedRODataColumns = append(verifiedRODataColumns, verifiedRODataColumn)
+
+		// Copy the iteration instance to a local variable to give each go-routine its own copy to play with.
+		// See https://golang.org/doc/faq#closures_and_goroutines for more details.
+		sidecar := sd
+		eg.Go(func() error {
+			if sidecar.Index < dataColumnsWithholdCount {
+				log.WithFields(logrus.Fields{
+					"root":  fmt.Sprintf("%#x", root),
+					"slot":  slot,
+					"index": sidecar.Index,
+				}).Warning("Withholding data column")
+
+				return nil
+			}
+
+			// Compute the subnet index based on the column index.
+			subnet := peerdas.ComputeSubnetForDataColumnSidecar(sidecar.Index)
+
+			if err := vs.P2P.BroadcastDataColumnSidecar(root, subnet, sidecar); err != nil {
+				return errors.Wrap(err, "broadcast data column")
+			}
+
+			return nil
+		})
+	}
+
+	if err := eg.Wait(); err != nil {
+		return errors.Wrap(err, "wait for data columns to be broadcasted")
+	}
+
+	if err := vs.DataColumnReceiver.ReceiveDataColumns(verifiedRODataColumns); err != nil {
+		return errors.Wrap(err, "receive data column")
+	}
+
+	for _, verifiedRODataColumn := range verifiedRODataColumns {
+		vs.OperationNotifier.OperationFeed().Send(&feed.Event{
+			Type: operation.DataColumnSidecarReceived,
+			Data: &operation.DataColumnSidecarReceivedData{DataColumn: &verifiedRODataColumn}, // #nosec G601
+		})
+	}
+	return nil
+}
+
 // Deprecated: The gRPC API will remain the default and fully supported through v8 (expected in 2026) but will be eventually removed in favor of REST API.
 //
 // PrepareBeaconProposer caches and updates the fee recipient for the given proposer.

beacon-chain/rpc/prysm/v1alpha1/validator/proposer_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain/kzg"
 	mock "github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain/testing"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/builder"
 	builderTest "github.com/OffchainLabs/prysm/v6/beacon-chain/builder/testing"
@@ -894,6 +895,9 @@ func injectSlashings(t *testing.T, st state.BeaconState, keys []bls.SecretKey, s
 }
 
 func TestProposer_ProposeBlock_OK(t *testing.T) {
+	// Initialize KZG for Fulu blocks
+	require.NoError(t, kzg.Start())
+
 	tests := []struct {
 		name       string
 		block      func([32]byte) *ethpb.GenericSignedBeaconBlock
@@ -1098,6 +1102,131 @@ func TestProposer_ProposeBlock_OK(t *testing.T) {
 			},
 			err: "blob KZG commitments don't match number of blobs or KZG proofs",
 		},
+		{
+			name: "fulu block no blob",
+			block: func(parent [32]byte) *ethpb.GenericSignedBeaconBlock {
+				sb := &ethpb.SignedBeaconBlockContentsFulu{
+					Block: &ethpb.SignedBeaconBlockFulu{
+						Block: &ethpb.BeaconBlockElectra{Slot: 5, ParentRoot: parent[:], Body: util.HydrateBeaconBlockBodyElectra(&ethpb.BeaconBlockBodyElectra{})},
+					},
+				}
+				blk := &ethpb.GenericSignedBeaconBlock_Fulu{Fulu: sb}
+				return &ethpb.GenericSignedBeaconBlock{Block: blk, IsBlinded: false}
+			},
+		},
+		{
+			name: "fulu block with single blob and cell proofs",
+			block: func(parent [32]byte) *ethpb.GenericSignedBeaconBlock {
+				numberOfColumns := uint64(128)
+				// For Fulu, we have cell proofs (blobs * numberOfColumns)
+				cellProofs := make([][]byte, numberOfColumns)
+				for i := uint64(0); i < numberOfColumns; i++ {
+					cellProofs[i] = bytesutil.PadTo([]byte{byte(i)}, 48)
+				}
+				// Blob must be exactly 131072 bytes
+				blob := make([]byte, 131072)
+				blob[0] = 0x01
+				sb := &ethpb.SignedBeaconBlockContentsFulu{
+					Block: &ethpb.SignedBeaconBlockFulu{
+						Block: &ethpb.BeaconBlockElectra{
+							Slot: 5, ParentRoot: parent[:],
+							Body: util.HydrateBeaconBlockBodyElectra(&ethpb.BeaconBlockBodyElectra{
+								BlobKzgCommitments: [][]byte{bytesutil.PadTo([]byte("kc"), 48)},
+							}),
+						},
+					},
+					KzgProofs: cellProofs,
+					Blobs:     [][]byte{blob},
+				}
+				blk := &ethpb.GenericSignedBeaconBlock_Fulu{Fulu: sb}
+				return &ethpb.GenericSignedBeaconBlock{Block: blk, IsBlinded: false}
+			},
+		},
+		{
+			name: "fulu block with multiple blobs and cell proofs",
+			block: func(parent [32]byte) *ethpb.GenericSignedBeaconBlock {
+				numberOfColumns := uint64(128)
+				blobCount := 3
+				// For Fulu, we have cell proofs (blobs * numberOfColumns)
+				cellProofs := make([][]byte, uint64(blobCount)*numberOfColumns)
+				for i := range cellProofs {
+					cellProofs[i] = bytesutil.PadTo([]byte{byte(i % 256)}, 48)
+				}
+				// Create properly sized blobs (131072 bytes each)
+				blobs := make([][]byte, blobCount)
+				for i := 0; i < blobCount; i++ {
+					blob := make([]byte, 131072)
+					blob[0] = byte(i + 1)
+					blobs[i] = blob
+				}
+				sb := &ethpb.SignedBeaconBlockContentsFulu{
+					Block: &ethpb.SignedBeaconBlockFulu{
+						Block: &ethpb.BeaconBlockElectra{
+							Slot: 5, ParentRoot: parent[:],
+							Body: util.HydrateBeaconBlockBodyElectra(&ethpb.BeaconBlockBodyElectra{
+								BlobKzgCommitments: [][]byte{
+									bytesutil.PadTo([]byte("kc"), 48),
+									bytesutil.PadTo([]byte("kc1"), 48),
+									bytesutil.PadTo([]byte("kc2"), 48),
+								},
+							}),
+						},
+					},
+					KzgProofs: cellProofs,
+					Blobs:     blobs,
+				}
+				blk := &ethpb.GenericSignedBeaconBlock_Fulu{Fulu: sb}
+				return &ethpb.GenericSignedBeaconBlock{Block: blk, IsBlinded: false}
+			},
+		},
+		{
+			name: "fulu block wrong cell proof count (should be blobs * 128)",
+			block: func(parent [32]byte) *ethpb.GenericSignedBeaconBlock {
+				// Wrong number of cell proofs - should be 2 * 128 = 256, but providing only 2
+				// Create properly sized blobs
+				blob1 := make([]byte, 131072)
+				blob1[0] = 0x01
+				blob2 := make([]byte, 131072)
+				blob2[0] = 0x02
+				sb := &ethpb.SignedBeaconBlockContentsFulu{
+					Block: &ethpb.SignedBeaconBlockFulu{
+						Block: &ethpb.BeaconBlockElectra{
+							Slot: 5, ParentRoot: parent[:],
+							Body: util.HydrateBeaconBlockBodyElectra(&ethpb.BeaconBlockBodyElectra{
+								BlobKzgCommitments: [][]byte{
+									bytesutil.PadTo([]byte("kc"), 48),
+									bytesutil.PadTo([]byte("kc1"), 48),
+								},
+							}),
+						},
+					},
+					KzgProofs: [][]byte{{0x01}, {0x02}}, // Wrong: should be 256 cell proofs
+					Blobs:     [][]byte{blob1, blob2},
+				}
+				blk := &ethpb.GenericSignedBeaconBlock_Fulu{Fulu: sb}
+				return &ethpb.GenericSignedBeaconBlock{Block: blk, IsBlinded: false}
+			},
+			err: "blobs and cells proofs mismatch",
+		},
+		{
+			name: "blind fulu block with blob commitments",
+			block: func(parent [32]byte) *ethpb.GenericSignedBeaconBlock {
+				blockToPropose := util.NewBlindedBeaconBlockFulu()
+				blockToPropose.Message.Slot = 5
+				blockToPropose.Message.ParentRoot = parent[:]
+				txRoot, err := ssz.TransactionsRoot([][]byte{})
+				require.NoError(t, err)
+				withdrawalsRoot, err := ssz.WithdrawalSliceRoot([]*enginev1.Withdrawal{}, fieldparams.MaxWithdrawalsPerPayload)
+				require.NoError(t, err)
+				blockToPropose.Message.Body.ExecutionPayloadHeader.TransactionsRoot = txRoot[:]
+				blockToPropose.Message.Body.ExecutionPayloadHeader.WithdrawalsRoot = withdrawalsRoot[:]
+				blockToPropose.Message.Body.BlobKzgCommitments = [][]byte{bytesutil.PadTo([]byte{0x01}, 48)}
+				blk := &ethpb.GenericSignedBeaconBlock_BlindedFulu{BlindedFulu: blockToPropose}
+				return &ethpb.GenericSignedBeaconBlock{Block: blk}
+			},
+			useBuilder: true,
+			err:        "commitment value doesn't match block", // Known issue with mock builder cell proof mismatch
+		},
 	}
 
 	for _, tt := range tests {
@@ -1111,15 +1240,29 @@ func TestProposer_ProposeBlock_OK(t *testing.T) {
 
 			c := &mock.ChainService{Root: bsRoot[:], State: beaconState}
 			db := dbutil.SetupDB(t)
+			// Create cell proofs for Fulu blocks (128 proofs per blob)
+			numberOfColumns := uint64(128)
+			cellProofs := make([][]byte, numberOfColumns)
+			for i := uint64(0); i < numberOfColumns; i++ {
+				cellProofs[i] = bytesutil.PadTo([]byte{byte(i)}, 48)
+			}
+			// Create properly sized blob for mock builder
+			mockBlob := make([]byte, 131072)
+			mockBlob[0] = 0x03
+			// Use the same commitment as in the blind block test
+			mockCommitment := bytesutil.PadTo([]byte{0x01}, 48)
+
 			proposerServer := &Server{
 				BlockReceiver: c,
 				BlockNotifier: c.BlockNotifier(),
 				P2P:           mockp2p.NewTestP2P(t),
 				BlockBuilder: &builderTest.MockBuilderService{HasConfigured: tt.useBuilder, PayloadCapella: emptyPayloadCapella(), PayloadDeneb: emptyPayloadDeneb(),
-					BlobBundle: &enginev1.BlobsBundle{KzgCommitments: [][]byte{bytesutil.PadTo([]byte{0x01}, 48)}, Proofs: [][]byte{{0x02}}, Blobs: [][]byte{{0x03}}}},
-				BeaconDB:          db,
-				BlobReceiver:      c,
-				OperationNotifier: c.OperationNotifier(),
+					BlobBundle:   &enginev1.BlobsBundle{KzgCommitments: [][]byte{mockCommitment}, Proofs: [][]byte{{0x02}}, Blobs: [][]byte{{0x03}}},
+					BlobBundleV2: &enginev1.BlobsBundleV2{KzgCommitments: [][]byte{mockCommitment}, Proofs: cellProofs, Blobs: [][]byte{mockBlob}}},
+				BeaconDB:           db,
+				BlobReceiver:       c,
+				DataColumnReceiver: c, // Add DataColumnReceiver for Fulu blocks
+				OperationNotifier:  c.OperationNotifier(),
 			}
 			blockToPropose := tt.block(bsRoot)
 			res, err := proposerServer.ProposeBeaconBlock(t.Context(), blockToPropose)
@@ -3286,3 +3429,252 @@ func TestProposer_ElectraBlobsAndProofs(t *testing.T) {
 	require.Equal(t, 10, len(blobs))
 	require.Equal(t, 10, len(proofs))
 }
+
+func TestServer_ProposeBeaconBlock_PostFuluBlindedBlock(t *testing.T) {
+	db := dbutil.SetupDB(t)
+	ctx := t.Context()
+
+	beaconState, parentRoot, _ := util.DeterministicGenesisStateWithGenesisBlock(t, ctx, db, 100)
+	require.NoError(t, beaconState.SetSlot(1))
+
+	t.Run("post-Fulu blinded block - early return success", func(t *testing.T) {
+		// Set up config with Fulu fork at epoch 5
+		params.SetupTestConfigCleanup(t)
+		cfg := params.BeaconConfig().Copy()
+		cfg.FuluForkEpoch = 5
+		params.OverrideBeaconConfig(cfg)
+
+		mockBuilder := &builderTest.MockBuilderService{
+			HasConfigured:                 true,
+			Cfg:                           &builderTest.Config{BeaconDB: db},
+			ErrSubmitBlindedBlockPostFulu: nil, // Success case
+		}
+
+		c := &mock.ChainService{State: beaconState, Root: parentRoot[:]}
+		proposerServer := &Server{
+			ChainStartFetcher: &mockExecution.Chain{},
+			Eth1InfoFetcher:   &mockExecution.Chain{},
+			Eth1BlockFetcher:  &mockExecution.Chain{},
+			BlockReceiver:     c,
+			BlobReceiver:      c,
+			HeadFetcher:       c,
+			BlockNotifier:     c.BlockNotifier(),
+			OperationNotifier: c.OperationNotifier(),
+			StateGen:          stategen.New(db, doublylinkedtree.New()),
+			TimeFetcher:       c,
+			SyncChecker:       &mockSync.Sync{IsSyncing: false},
+			BeaconDB:          db,
+			BlockBuilder:      mockBuilder,
+			P2P:               &mockp2p.MockBroadcaster{},
+		}
+
+		// Create a blinded block at slot 160 (epoch 5, which is >= FuluForkEpoch)
+		blindedBlock := util.NewBlindedBeaconBlockDeneb()
+		blindedBlock.Message.Slot = 160 // This puts us at epoch 5 (160/32 = 5)
+		blindedBlock.Message.ProposerIndex = 0
+		blindedBlock.Message.ParentRoot = parentRoot[:]
+		blindedBlock.Message.StateRoot = make([]byte, 32)
+
+		req := &ethpb.GenericSignedBeaconBlock{
+			Block: &ethpb.GenericSignedBeaconBlock_BlindedDeneb{BlindedDeneb: blindedBlock},
+		}
+
+		// This should trigger the post-Fulu early return path
+		res, err := proposerServer.ProposeBeaconBlock(ctx, req)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+		require.NotEmpty(t, res.BlockRoot)
+	})
+
+	t.Run("post-Fulu blinded block - builder submission error", func(t *testing.T) {
+		// Set up config with Fulu fork at epoch 5
+		params.SetupTestConfigCleanup(t)
+		cfg := params.BeaconConfig().Copy()
+		cfg.FuluForkEpoch = 5
+		params.OverrideBeaconConfig(cfg)
+
+		mockBuilder := &builderTest.MockBuilderService{
+			HasConfigured:                 true,
+			Cfg:                           &builderTest.Config{BeaconDB: db},
+			ErrSubmitBlindedBlockPostFulu: errors.New("post-Fulu builder submission failed"),
+		}
+
+		c := &mock.ChainService{State: beaconState, Root: parentRoot[:]}
+		proposerServer := &Server{
+			ChainStartFetcher: &mockExecution.Chain{},
+			Eth1InfoFetcher:   &mockExecution.Chain{},
+			Eth1BlockFetcher:  &mockExecution.Chain{},
+			BlockReceiver:     c,
+			BlobReceiver:      c,
+			HeadFetcher:       c,
+			BlockNotifier:     c.BlockNotifier(),
+			OperationNotifier: c.OperationNotifier(),
+			StateGen:          stategen.New(db, doublylinkedtree.New()),
+			TimeFetcher:       c,
+			SyncChecker:       &mockSync.Sync{IsSyncing: false},
+			BeaconDB:          db,
+			BlockBuilder:      mockBuilder,
+			P2P:               &mockp2p.MockBroadcaster{},
+		}
+
+		// Create a blinded block at slot 160 (epoch 5)
+		blindedBlock := util.NewBlindedBeaconBlockDeneb()
+		blindedBlock.Message.Slot = 160
+		blindedBlock.Message.ProposerIndex = 0
+		blindedBlock.Message.ParentRoot = parentRoot[:]
+		blindedBlock.Message.StateRoot = make([]byte, 32)
+
+		req := &ethpb.GenericSignedBeaconBlock{
+			Block: &ethpb.GenericSignedBeaconBlock_BlindedDeneb{BlindedDeneb: blindedBlock},
+		}
+
+		_, err := proposerServer.ProposeBeaconBlock(ctx, req)
+		require.ErrorContains(t, "Could not submit blinded block post-Fulu", err)
+		require.ErrorContains(t, "post-Fulu builder submission failed", err)
+	})
+
+	t.Run("pre-Fulu blinded block - uses regular handleBlindedBlock path", func(t *testing.T) {
+		// Set up config with Fulu fork at epoch 10 (future)
+		params.SetupTestConfigCleanup(t)
+		cfg := params.BeaconConfig().Copy()
+		cfg.FuluForkEpoch = 10
+		params.OverrideBeaconConfig(cfg)
+
+		mockBuilder := &builderTest.MockBuilderService{
+			HasConfigured: true,
+			Cfg:           &builderTest.Config{BeaconDB: db},
+			PayloadDeneb:  &enginev1.ExecutionPayloadDeneb{},
+			BlobBundle:    &enginev1.BlobsBundle{},
+		}
+
+		c := &mock.ChainService{State: beaconState, Root: parentRoot[:]}
+		proposerServer := &Server{
+			ChainStartFetcher: &mockExecution.Chain{},
+			Eth1InfoFetcher:   &mockExecution.Chain{},
+			Eth1BlockFetcher:  &mockExecution.Chain{},
+			BlockReceiver:     c,
+			BlobReceiver:      c,
+			HeadFetcher:       c,
+			BlockNotifier:     c.BlockNotifier(),
+			OperationNotifier: c.OperationNotifier(),
+			StateGen:          stategen.New(db, doublylinkedtree.New()),
+			TimeFetcher:       c,
+			SyncChecker:       &mockSync.Sync{IsSyncing: false},
+			BeaconDB:          db,
+			BlockBuilder:      mockBuilder,
+			P2P:               &mockp2p.MockBroadcaster{},
+		}
+
+		// Create a blinded block at slot 160 (epoch 5, which is < FuluForkEpoch=10)
+		blindedBlock := util.NewBlindedBeaconBlockDeneb()
+		blindedBlock.Message.Slot = 160
+		blindedBlock.Message.ProposerIndex = 0
+		blindedBlock.Message.ParentRoot = parentRoot[:]
+		blindedBlock.Message.StateRoot = make([]byte, 32)
+
+		req := &ethpb.GenericSignedBeaconBlock{
+			Block: &ethpb.GenericSignedBeaconBlock_BlindedDeneb{BlindedDeneb: blindedBlock},
+		}
+
+		// This should NOT trigger the post-Fulu early return path, but use handleBlindedBlock instead
+		res, err := proposerServer.ProposeBeaconBlock(ctx, req)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+		require.NotEmpty(t, res.BlockRoot)
+	})
+
+	t.Run("boundary test - exactly at Fulu fork epoch", func(t *testing.T) {
+		// Set up config with Fulu fork at epoch 5
+		params.SetupTestConfigCleanup(t)
+		cfg := params.BeaconConfig().Copy()
+		cfg.FuluForkEpoch = 5
+		params.OverrideBeaconConfig(cfg)
+
+		mockBuilder := &builderTest.MockBuilderService{
+			HasConfigured:                 true,
+			Cfg:                           &builderTest.Config{BeaconDB: db},
+			ErrSubmitBlindedBlockPostFulu: nil,
+		}
+
+		c := &mock.ChainService{State: beaconState, Root: parentRoot[:]}
+		proposerServer := &Server{
+			ChainStartFetcher: &mockExecution.Chain{},
+			Eth1InfoFetcher:   &mockExecution.Chain{},
+			Eth1BlockFetcher:  &mockExecution.Chain{},
+			BlockReceiver:     c,
+			BlobReceiver:      c,
+			HeadFetcher:       c,
+			BlockNotifier:     c.BlockNotifier(),
+			OperationNotifier: c.OperationNotifier(),
+			StateGen:          stategen.New(db, doublylinkedtree.New()),
+			TimeFetcher:       c,
+			SyncChecker:       &mockSync.Sync{IsSyncing: false},
+			BeaconDB:          db,
+			BlockBuilder:      mockBuilder,
+			P2P:               &mockp2p.MockBroadcaster{},
+		}
+
+		// Create a blinded block at slot 160 (exactly epoch 5)
+		blindedBlock := util.NewBlindedBeaconBlockDeneb()
+		blindedBlock.Message.Slot = 160 // 160/32 = 5 (exactly at FuluForkEpoch)
+		blindedBlock.Message.ProposerIndex = 0
+		blindedBlock.Message.ParentRoot = parentRoot[:]
+		blindedBlock.Message.StateRoot = make([]byte, 32)
+
+		req := &ethpb.GenericSignedBeaconBlock{
+			Block: &ethpb.GenericSignedBeaconBlock_BlindedDeneb{BlindedDeneb: blindedBlock},
+		}
+
+		// Should trigger post-Fulu path since epoch 5 >= FuluForkEpoch (5)
+		res, err := proposerServer.ProposeBeaconBlock(ctx, req)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+		require.NotEmpty(t, res.BlockRoot)
+	})
+
+	t.Run("unblinded block - not affected by post-Fulu condition", func(t *testing.T) {
+		// Set up config with Fulu fork at epoch 5
+		params.SetupTestConfigCleanup(t)
+		cfg := params.BeaconConfig().Copy()
+		cfg.FuluForkEpoch = 5
+		params.OverrideBeaconConfig(cfg)
+
+		c := &mock.ChainService{State: beaconState, Root: parentRoot[:]}
+		proposerServer := &Server{
+			ChainStartFetcher: &mockExecution.Chain{},
+			Eth1InfoFetcher:   &mockExecution.Chain{},
+			Eth1BlockFetcher:  &mockExecution.Chain{},
+			BlockReceiver:     c,
+			BlobReceiver:      c,
+			HeadFetcher:       c,
+			BlockNotifier:     c.BlockNotifier(),
+			OperationNotifier: c.OperationNotifier(),
+			StateGen:          stategen.New(db, doublylinkedtree.New()),
+			TimeFetcher:       c,
+			SyncChecker:       &mockSync.Sync{IsSyncing: false},
+			BeaconDB:          db,
+			P2P:               &mockp2p.MockBroadcaster{},
+		}
+
+		// Create an unblinded block at slot 160 (epoch 5)
+		unblindeBlock := util.NewBeaconBlockDeneb()
+		unblindeBlock.Block.Slot = 160
+		unblindeBlock.Block.ProposerIndex = 0
+		unblindeBlock.Block.ParentRoot = parentRoot[:]
+		unblindeBlock.Block.StateRoot = make([]byte, 32)
+
+		req := &ethpb.GenericSignedBeaconBlock{
+			Block: &ethpb.GenericSignedBeaconBlock_Deneb{
+				Deneb: &ethpb.SignedBeaconBlockContentsDeneb{
+					Block: unblindeBlock,
+				},
+			},
+		}
+
+		// Unblinded blocks should not trigger post-Fulu condition, even at epoch >= FuluForkEpoch
+		res, err := proposerServer.ProposeBeaconBlock(ctx, req)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+		require.NotEmpty(t, res.BlockRoot)
+	})
+}

beacon-chain/rpc/prysm/v1alpha1/validator/server.go

@@ -69,6 +69,7 @@ type Server struct {
 	SyncCommitteePool       synccommittee.Pool
 	BlockReceiver           blockchain.BlockReceiver
 	BlobReceiver            blockchain.BlobReceiver
+	DataColumnReceiver      blockchain.DataColumnReceiver
 	MockEth1Votes           bool
 	Eth1BlockFetcher        execution.POWBlockFetcher
 	PendingDepositsFetcher  depositsnapshot.PendingDepositsFetcher

beacon-chain/rpc/service.go

@@ -89,6 +89,7 @@ type Config struct {
 	AttestationReceiver       blockchain.AttestationReceiver
 	BlockReceiver             blockchain.BlockReceiver
 	BlobReceiver              blockchain.BlobReceiver
+	DataColumnReceiver        blockchain.DataColumnReceiver
 	ExecutionChainService     execution.Chain
 	ChainStartFetcher         execution.ChainStartFetcher
 	ExecutionChainInfoFetcher execution.ChainInfoFetcher
@@ -120,6 +121,7 @@ type Config struct {
 	Router                    *http.ServeMux
 	ClockWaiter               startup.ClockWaiter
 	BlobStorage               *filesystem.BlobStorage
+	DataColumnStorage         *filesystem.DataColumnStorage
 	TrackedValidatorsCache    *cache.TrackedValidatorsCache
 	PayloadIDCache            *cache.PayloadIDCache
 	LCStore                   *lightClient.Store
@@ -196,6 +198,7 @@ func NewService(ctx context.Context, cfg *Config) *Service {
 		ChainInfoFetcher:   s.cfg.ChainInfoFetcher,
 		GenesisTimeFetcher: s.cfg.GenesisTimeFetcher,
 		BlobStorage:        s.cfg.BlobStorage,
+		DataColumnStorage:  s.cfg.DataColumnStorage,
 	}
 	rewardFetcher := &rewards.BlockRewardService{Replayer: ch, DB: s.cfg.BeaconDB}
 	coreService := &core.Service{
@@ -236,6 +239,7 @@ func NewService(ctx context.Context, cfg *Config) *Service {
 		P2P:                     s.cfg.Broadcaster,
 		BlockReceiver:           s.cfg.BlockReceiver,
 		BlobReceiver:            s.cfg.BlobReceiver,
+		DataColumnReceiver:      s.cfg.DataColumnReceiver,
 		MockEth1Votes:           s.cfg.MockEth1Votes,
 		Eth1BlockFetcher:        s.cfg.ExecutionChainService,
 		PendingDepositsFetcher:  s.cfg.PendingDepositFetcher,

beacon-chain/rpc/testutil/BUILD.bazel

@@ -8,6 +8,7 @@ go_library(
         "mock_blocker.go",
         "mock_exec_chain_info_fetcher.go",
         "mock_genesis_timefetcher.go",
+        "mock_sidecars.go",
         "mock_stater.go",
     ],
     importpath = "github.com/OffchainLabs/prysm/v6/beacon-chain/rpc/testutil",

beacon-chain/rpc/testutil/mock_sidecars.go

@@ -0,0 +1,44 @@
+package testutil
+
+import ethpb "github.com/OffchainLabs/prysm/v6/proto/prysm/v1alpha1"
+
+// CreateDataColumnSidecar generates a filled dummy data column sidecar
+func CreateDataColumnSidecar(index uint64, data []byte) *ethpb.DataColumnSidecar {
+	return &ethpb.DataColumnSidecar{
+		Index:  index,
+		Column: [][]byte{data},
+		SignedBlockHeader: &ethpb.SignedBeaconBlockHeader{
+			Header: &ethpb.BeaconBlockHeader{
+				Slot:          1,
+				ProposerIndex: 1,
+				ParentRoot:    make([]byte, 32),
+				StateRoot:     make([]byte, 32),
+				BodyRoot:      make([]byte, 32),
+			},
+			Signature: make([]byte, 96),
+		},
+		KzgCommitments:               [][]byte{make([]byte, 48)},
+		KzgProofs:                    [][]byte{make([]byte, 48)},
+		KzgCommitmentsInclusionProof: [][]byte{make([]byte, 32)},
+	}
+}
+
+// CreateBlobSidecar generates a filled dummy data blob sidecar
+func CreateBlobSidecar(index uint64, blob []byte) *ethpb.BlobSidecar {
+	return &ethpb.BlobSidecar{
+		Index: index,
+		Blob:  blob,
+		SignedBlockHeader: &ethpb.SignedBeaconBlockHeader{
+			Header: &ethpb.BeaconBlockHeader{
+				Slot:          1,
+				ProposerIndex: 1,
+				ParentRoot:    make([]byte, 32),
+				StateRoot:     make([]byte, 32),
+				BodyRoot:      make([]byte, 32),
+			},
+			Signature: make([]byte, 96),
+		},
+		KzgCommitment: make([]byte, 48),
+		KzgProof:      make([]byte, 48),
+	}
+}

beacon-chain/rpc/testutil/mock_stater.go

@@ -15,10 +15,14 @@ type MockStater struct {
 	BeaconStateRoot   []byte
 	StatesBySlot      map[primitives.Slot]state.BeaconState
 	StatesByRoot      map[[32]byte]state.BeaconState
+	CustomError       error
 }
 
 // State --
 func (m *MockStater) State(ctx context.Context, id []byte) (state.BeaconState, error) {
+	if m.CustomError != nil {
+		return nil, m.CustomError
+	}
 	if m.StateProviderFunc != nil {
 		return m.StateProviderFunc(ctx, id)
 	}

beacon-chain/sync/BUILD.bazel

@@ -8,6 +8,7 @@ go_library(
         "broadcast_bls_changes.go",
         "context.go",
         "custody.go",
+        "data_column_sidecars.go",
         "data_columns_reconstruct.go",
         "deadlines.go",
         "decode_pubsub.go",
@@ -167,6 +168,7 @@ go_test(
         "broadcast_bls_changes_test.go",
         "context_test.go",
         "custody_test.go",
+        "data_column_sidecars_test.go",
         "data_columns_reconstruct_test.go",
         "decode_pubsub_test.go",
         "error_test.go",
@@ -281,6 +283,7 @@ go_test(
         "@com_github_golang_snappy//:go_default_library",
         "@com_github_libp2p_go_libp2p//:go_default_library",
         "@com_github_libp2p_go_libp2p//core:go_default_library",
+        "@com_github_libp2p_go_libp2p//core/crypto:go_default_library",
         "@com_github_libp2p_go_libp2p//core/network:go_default_library",
         "@com_github_libp2p_go_libp2p//core/peer:go_default_library",
         "@com_github_libp2p_go_libp2p//core/protocol:go_default_library",

beacon-chain/sync/backfill/blobs.go

@@ -91,9 +91,7 @@ func (bs *blobSync) validateNext(rb blocks.ROBlob) error {
 		return err
 	}
 
-	sc := blocks.NewSidecarFromBlobSidecar(rb)
-
-	if err := bs.store.Persist(bs.current, sc); err != nil {
+	if err := bs.store.Persist(bs.current, rb); err != nil {
 		return err
 	}
 

beacon-chain/sync/data_column_sidecars.go

@@ -0,0 +1,950 @@
+package sync
+
+import (
+	"bytes"
+	"context"
+	"slices"
+	"sync"
+	"time"
+
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/peerdas"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/filesystem"
+	prysmP2P "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p"
+	p2ptypes "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/types"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/verification"
+	fieldparams "github.com/OffchainLabs/prysm/v6/config/fieldparams"
+	"github.com/OffchainLabs/prysm/v6/config/params"
+	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
+	"github.com/OffchainLabs/prysm/v6/consensus-types/primitives"
+	leakybucket "github.com/OffchainLabs/prysm/v6/container/leaky-bucket"
+	"github.com/OffchainLabs/prysm/v6/crypto/rand"
+	eth "github.com/OffchainLabs/prysm/v6/proto/prysm/v1alpha1"
+	ethpb "github.com/OffchainLabs/prysm/v6/proto/prysm/v1alpha1"
+	goPeer "github.com/libp2p/go-libp2p/core/peer"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+)
+
+// DataColumnSidecarsParams stores the common parameters needed to
+// fetch data column sidecars from peers.
+type DataColumnSidecarsParams struct {
+	Ctx                     context.Context                     // Context
+	Tor                     blockchain.TemporalOracle           // Temporal oracle, useful to get the current slot
+	P2P                     prysmP2P.P2P                        // P2P network interface
+	RateLimiter             *leakybucket.Collector              // Rate limiter for outgoing requests
+	CtxMap                  ContextByteVersions                 // Context map, useful to know if a message is mapped to the correct fork
+	Storage                 filesystem.DataColumnStorageReader  // Data columns storage
+	NewVerifier             verification.NewDataColumnsVerifier // Data columns verifier to check to conformity of incoming data column sidecars
+	DownscorePeerOnRPCFault bool                                // Downscore a peer if it commits an RPC fault. Not responding sidecars at all is considered as a fault.
+}
+
+// FetchDataColumnSidecars retrieves data column sidecars from storage and peers for the given
+// blocks and requested data column indices. It employs a multi-step strategy:
+//
+//  1. Direct retrieval: If all requested columns are available in storage, they are
+//     retrieved directly without reconstruction.
+//  2. Reconstruction-based retrieval: If some requested columns are missing but sufficient
+//     stored columns exist (at least the minimum required for reconstruction), the function
+//     reconstructs all columns and extracts the requested indices.
+//  3. Peer retrieval: If storage and reconstruction fail, missing columns are requested
+//     from connected peers that are expected to custody the required data.
+//
+// The function returns a map of block roots to their corresponding verified read-only data
+// columns. It returns an error if data column storage is unavailable, if storage/reconstruction
+// operations fail unexpectedly, or if not all requested columns could be retrieved from peers.
+func FetchDataColumnSidecars(
+	params DataColumnSidecarsParams,
+	roBlocks []blocks.ROBlock,
+	indicesMap map[uint64]bool,
+) (map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn, error) {
+	if len(roBlocks) == 0 || len(indicesMap) == 0 {
+		return nil, nil
+	}
+
+	indices := sortedSliceFromMap(indicesMap)
+	slotsWithCommitments := make(map[primitives.Slot]bool)
+	missingIndicesByRoot := make(map[[fieldparams.RootLength]byte]map[uint64]bool)
+	indicesByRootStored := make(map[[fieldparams.RootLength]byte]map[uint64]bool)
+	result := make(map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn)
+
+	for _, roBlock := range roBlocks {
+		// Filter out blocks without commitments.
+		block := roBlock.Block()
+		commitments, err := block.Body().BlobKzgCommitments()
+		if err != nil {
+			return nil, errors.Wrapf(err, "get blob kzg commitments for block root %#x", roBlock.Root())
+		}
+		if len(commitments) == 0 {
+			continue
+		}
+
+		slotsWithCommitments[block.Slot()] = true
+		root := roBlock.Root()
+
+		// Step 1: Get the requested sidecars for this root if available in storage
+		requestedColumns, err := tryGetStoredColumns(params.Storage, root, indices)
+		if err != nil {
+			return nil, errors.Wrapf(err, "try get direct columns for root %#x", root)
+		}
+		if requestedColumns != nil {
+			result[root] = requestedColumns
+			continue
+		}
+
+		// Step 2: If step 1 failed, reconstruct the requested sidecars from what is available in storage
+		requestedColumns, err = tryGetReconstructedColumns(params.Storage, root, indices)
+		if err != nil {
+			return nil, errors.Wrapf(err, "try get reconstructed columns for root %#x", root)
+		}
+		if requestedColumns != nil {
+			result[root] = requestedColumns
+			continue
+		}
+
+		// Step 3a: If steps 1 and 2 failed, keep track of the sidecars that need to be queried from peers
+		//          and those that are already stored.
+		indicesToQueryMap, indicesStoredMap := categorizeIndices(params.Storage, root, indices)
+
+		if len(indicesToQueryMap) > 0 {
+			missingIndicesByRoot[root] = indicesToQueryMap
+		}
+		if len(indicesStoredMap) > 0 {
+			indicesByRootStored[root] = indicesStoredMap
+		}
+	}
+
+	// Early return if no sidecars need to be queried from peers.
+	if len(missingIndicesByRoot) == 0 {
+		return result, nil
+	}
+
+	// Step 3b: Request missing sidecars from peers.
+	start, count := time.Now(), computeTotalCount(missingIndicesByRoot)
+	fromPeersResult, err := tryRequestingColumnsFromPeers(params, roBlocks, slotsWithCommitments, missingIndicesByRoot)
+	if err != nil {
+		return nil, errors.Wrap(err, "request from peers")
+	}
+
+	log.WithFields(logrus.Fields{"duration": time.Since(start), "count": count}).Debug("Requested data column sidecars from peers")
+
+	// Step 3c: If needed, try to reconstruct missing sidecars from storage and fetched data.
+	fromReconstructionResult, err := tryReconstructFromStorageAndPeers(params.Storage, fromPeersResult, indicesMap, missingIndicesByRoot)
+	if err != nil {
+		return nil, errors.Wrap(err, "reconstruct from storage and peers")
+	}
+
+	for root, verifiedSidecars := range fromReconstructionResult {
+		result[root] = verifiedSidecars
+	}
+
+	for root := range fromPeersResult {
+		if _, ok := fromReconstructionResult[root]; ok {
+			// We already have what we need from peers + reconstruction
+			continue
+		}
+
+		result[root] = append(result[root], fromPeersResult[root]...)
+
+		storedIndices := indicesByRootStored[root]
+		if len(storedIndices) == 0 {
+			continue
+		}
+
+		storedColumns, err := tryGetStoredColumns(params.Storage, root, sortedSliceFromMap(storedIndices))
+		if err != nil {
+			return nil, errors.Wrapf(err, "try get direct columns for root %#x", root)
+		}
+
+		result[root] = append(result[root], storedColumns...)
+	}
+
+	return result, nil
+}
+
+// tryGetStoredColumns attempts to retrieve all requested data column sidecars directly from storage
+// if they are all available. Returns the sidecars if successful, and nil if at least one
+// requested sidecar is not available in the storage.
+func tryGetStoredColumns(storage filesystem.DataColumnStorageReader, blockRoot [fieldparams.RootLength]byte, indices []uint64) ([]blocks.VerifiedRODataColumn, error) {
+	// Check if all requested indices are present in cache
+	storedIndices := storage.Summary(blockRoot).Stored()
+	allRequestedPresent := true
+	for _, requestedIndex := range indices {
+		if !storedIndices[requestedIndex] {
+			allRequestedPresent = false
+			break
+		}
+	}
+
+	if !allRequestedPresent {
+		return nil, nil
+	}
+
+	// All requested data is present, retrieve directly from DB
+	requestedColumns, err := storage.Get(blockRoot, indices)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to get data columns for block root %#x", blockRoot)
+	}
+
+	return requestedColumns, nil
+}
+
+// tryGetReconstructedColumns attempts to retrieve columns using reconstruction
+// if sufficient columns are available. Returns the columns if successful, nil and nil if insufficient columns,
+// or nil and error if an error occurs.
+func tryGetReconstructedColumns(storage filesystem.DataColumnStorageReader, blockRoot [fieldparams.RootLength]byte, indices []uint64) ([]blocks.VerifiedRODataColumn, error) {
+	// Check if we have enough columns for reconstruction
+	summary := storage.Summary(blockRoot)
+	if summary.Count() < peerdas.MinimumColumnCountToReconstruct() {
+		return nil, nil
+	}
+
+	// Retrieve all stored columns for reconstruction
+	allStoredColumns, err := storage.Get(blockRoot, nil)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to get all stored columns for reconstruction for block root %#x", blockRoot)
+	}
+
+	// Attempt reconstruction
+	reconstructedColumns, err := peerdas.ReconstructDataColumnSidecars(allStoredColumns)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to reconstruct data columns for block root %#x", blockRoot)
+	}
+
+	// Health check: ensure we have the expected number of columns
+	numberOfColumns := params.BeaconConfig().NumberOfColumns
+	if uint64(len(reconstructedColumns)) != numberOfColumns {
+		return nil, errors.Errorf("reconstructed %d columns but expected %d for block root %#x", len(reconstructedColumns), numberOfColumns, blockRoot)
+	}
+
+	// Extract only the requested indices from reconstructed data using direct indexing
+	requestedColumns := make([]blocks.VerifiedRODataColumn, 0, len(indices))
+	for _, requestedIndex := range indices {
+		if requestedIndex >= numberOfColumns {
+			return nil, errors.Errorf("requested column index %d exceeds maximum %d for block root %#x", requestedIndex, numberOfColumns-1, blockRoot)
+		}
+		requestedColumns = append(requestedColumns, reconstructedColumns[requestedIndex])
+	}
+
+	return requestedColumns, nil
+}
+
+// categorizeIndices separates indices into those that need to be queried from peers
+// and those that are already stored.
+func categorizeIndices(storage filesystem.DataColumnStorageReader, blockRoot [fieldparams.RootLength]byte, indices []uint64) (map[uint64]bool, map[uint64]bool) {
+	indicesToQuery := make(map[uint64]bool, len(indices))
+	indicesStored := make(map[uint64]bool, len(indices))
+
+	allStoredIndices := storage.Summary(blockRoot).Stored()
+	for _, index := range indices {
+		if allStoredIndices[index] {
+			indicesStored[index] = true
+			continue
+		}
+		indicesToQuery[index] = true
+	}
+
+	return indicesToQuery, indicesStored
+}
+
+// tryRequestingColumnsFromPeers attempts to request missing data column sidecars from connected peers.
+// It explores the connected peers to find those that are expected to custody the requested columns
+// and returns only when all requested columns are either retrieved or have been tried to be retrieved
+// by all possible peers.
+// WARNING: This function alters `missingIndicesByRoot` by removing successfully retrieved columns.
+// After running this function, the user can check the content of the (modified) `missingIndicesByRoot` map
+// to check if some sidecars are still missing.
+func tryRequestingColumnsFromPeers(
+	p DataColumnSidecarsParams,
+	roBlocks []blocks.ROBlock,
+	slotsWithCommitments map[primitives.Slot]bool,
+	missingIndicesByRoot map[[fieldparams.RootLength]byte]map[uint64]bool,
+) (map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn, error) {
+	// Create a new random source for peer selection.
+	randomSource := rand.NewGenerator()
+
+	// Compute slots by block root.
+	slotByRoot := computeSlotByBlockRoot(roBlocks)
+
+	// Determine all sidecars each peers are expected to custody.
+	connectedPeersSlice := p.P2P.Peers().Connected()
+	connectedPeers := make(map[goPeer.ID]bool, len(connectedPeersSlice))
+	for _, peer := range connectedPeersSlice {
+		connectedPeers[peer] = true
+	}
+
+	indicesByRootByPeer, err := computeIndicesByRootByPeer(p.P2P, slotByRoot, missingIndicesByRoot, connectedPeers)
+	if err != nil {
+		return nil, errors.Wrap(err, "explore peers")
+	}
+
+	verifiedColumnsByRoot := make(map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn)
+	for len(missingIndicesByRoot) > 0 && len(indicesByRootByPeer) > 0 {
+		// Select peers to query the missing sidecars from.
+		indicesByRootByPeerToQuery, err := selectPeers(p, randomSource, len(missingIndicesByRoot), indicesByRootByPeer)
+		if err != nil {
+			return nil, errors.Wrap(err, "select peers")
+		}
+
+		// Remove selected peers from the maps.
+		for peer := range indicesByRootByPeerToQuery {
+			delete(connectedPeers, peer)
+		}
+
+		// Fetch the sidecars from the chosen peers.
+		roDataColumnsByPeer := fetchDataColumnSidecarsFromPeers(p, slotByRoot, slotsWithCommitments, indicesByRootByPeerToQuery)
+
+		// Verify the received data column sidecars.
+		verifiedRoDataColumnSidecars, err := verifyDataColumnSidecarsByPeer(p.P2P, p.NewVerifier, roDataColumnsByPeer)
+		if err != nil {
+			return nil, errors.Wrap(err, "verify data columns sidecars by peer")
+		}
+
+		// Remove the verified sidecars from the missing indices map and compute the new verified columns by root.
+		localVerifiedColumnsByRoot := updateResults(verifiedRoDataColumnSidecars, missingIndicesByRoot)
+		for root, verifiedRoDataColumns := range localVerifiedColumnsByRoot {
+			verifiedColumnsByRoot[root] = append(verifiedColumnsByRoot[root], verifiedRoDataColumns...)
+		}
+
+		// Compute indices by root by peers with the updated missing indices and connected peers.
+		indicesByRootByPeer, err = computeIndicesByRootByPeer(p.P2P, slotByRoot, missingIndicesByRoot, connectedPeers)
+		if err != nil {
+			return nil, errors.Wrap(err, "explore peers")
+		}
+	}
+
+	return verifiedColumnsByRoot, nil
+}
+
+// tryReconstructFromStorageAndPeers attempts to reconstruct missing data column sidecars
+// using the data available in the storage and the data fetched from peers.
+// If, for at least one root, the reconstruction is not possible, an error is returned.
+func tryReconstructFromStorageAndPeers(
+	storage filesystem.DataColumnStorageReader,
+	fromPeersByRoot map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn,
+	indices map[uint64]bool,
+	missingIndicesByRoot map[[fieldparams.RootLength]byte]map[uint64]bool,
+) (map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn, error) {
+	if len(missingIndicesByRoot) == 0 {
+		// Nothing to do, return early.
+		return nil, nil
+	}
+
+	minimumColumnsCountToReconstruct := peerdas.MinimumColumnCountToReconstruct()
+
+	start := time.Now()
+	result := make(map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn, len(missingIndicesByRoot))
+	for root := range missingIndicesByRoot {
+		// Check if a reconstruction is possible based on what we have from the store and fetched from peers.
+		summary := storage.Summary(root)
+		storedCount := summary.Count()
+		fetchedCount := uint64(len(fromPeersByRoot[root]))
+
+		if storedCount+fetchedCount < minimumColumnsCountToReconstruct {
+			return nil, errors.Errorf("cannot reconstruct all needed columns for root %#x. stored: %d, fetched: %d, minimum: %d", root, storedCount, fetchedCount, minimumColumnsCountToReconstruct)
+		}
+
+		// Load all we have in the store.
+		storedSidecars, err := storage.Get(root, nil)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to get stored sidecars for root %#x", root)
+		}
+
+		sidecars := make([]blocks.VerifiedRODataColumn, 0, storedCount+fetchedCount)
+		sidecars = append(sidecars, storedSidecars...)
+		sidecars = append(sidecars, fromPeersByRoot[root]...)
+
+		// Attempt reconstruction.
+		reconstructedSidecars, err := peerdas.ReconstructDataColumnSidecars(sidecars)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to reconstruct data columns for root %#x", root)
+		}
+
+		// Select only sidecars we need.
+		for _, sidecar := range reconstructedSidecars {
+			if indices[sidecar.Index] {
+				result[root] = append(result[root], sidecar)
+			}
+		}
+	}
+
+	log.WithFields(logrus.Fields{
+		"rootCount": len(missingIndicesByRoot),
+		"elapsed":   time.Since(start),
+	}).Debug("Reconstructed from storage and peers")
+
+	return result, nil
+}
+
+// selectPeers selects peers to query the sidecars.
+// It begins by randomly selecting a peer in `origIndicesByRootByPeer` that has enough bandwidth,
+// and assigns to it all its available sidecars. Then, it randomly select an other peer, until
+// all sidecars in `missingIndicesByRoot` are covered.
+func selectPeers(
+	p DataColumnSidecarsParams,
+	randomSource *rand.Rand,
+	count int,
+	origIndicesByRootByPeer map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool,
+) (map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool, error) {
+	const randomPeerTimeout = 2 * time.Minute
+
+	// Select peers to query the missing sidecars from.
+	indicesByRootByPeer := copyIndicesByRootByPeer(origIndicesByRootByPeer)
+	internalIndicesByRootByPeer := copyIndicesByRootByPeer(indicesByRootByPeer)
+	indicesByRootByPeerToQuery := make(map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool)
+	for len(internalIndicesByRootByPeer) > 0 {
+		// Randomly select a peer with enough bandwidth.
+		peer, err := func() (goPeer.ID, error) {
+			ctx, cancel := context.WithTimeout(p.Ctx, randomPeerTimeout)
+			defer cancel()
+
+			peer, err := randomPeer(ctx, randomSource, p.RateLimiter, count, internalIndicesByRootByPeer)
+			if err != nil {
+				return "", errors.Wrap(err, "select random peer")
+			}
+
+			return peer, err
+		}()
+		if err != nil {
+			return nil, err
+		}
+
+		// Query all the sidecars that peer can offer us.
+		newIndicesByRoot, ok := internalIndicesByRootByPeer[peer]
+		if !ok {
+			return nil, errors.Errorf("peer %s not found in internal indices by root by peer map", peer)
+		}
+
+		indicesByRootByPeerToQuery[peer] = newIndicesByRoot
+
+		// Remove this peer from the maps to avoid re-selection.
+		delete(indicesByRootByPeer, peer)
+		delete(internalIndicesByRootByPeer, peer)
+
+		// Delete the corresponding sidecars from other peers in the internal map
+		// to avoid re-selection during this iteration.
+		for peer, indicesByRoot := range internalIndicesByRootByPeer {
+			for root, indices := range indicesByRoot {
+				newIndices := newIndicesByRoot[root]
+				for index := range newIndices {
+					delete(indices, index)
+				}
+				if len(indices) == 0 {
+					delete(indicesByRoot, root)
+				}
+			}
+			if len(indicesByRoot) == 0 {
+				delete(internalIndicesByRootByPeer, peer)
+			}
+		}
+	}
+
+	return indicesByRootByPeerToQuery, nil
+}
+
+// updateResults updates the missing indices and verified sidecars maps based on the newly verified sidecars.
+// WARNING: This function alters `missingIndicesByRoot` by removing verified sidecars.
+// After running this function, the user can check the content of the (modified) `missingIndicesByRoot` map
+// to check if some sidecars are still missing.
+func updateResults(
+	verifiedSidecars []blocks.VerifiedRODataColumn,
+	missingIndicesByRoot map[[fieldparams.RootLength]byte]map[uint64]bool,
+) map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn {
+	// Copy the original map to avoid modifying it directly.
+	verifiedSidecarsByRoot := make(map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn)
+	for _, verifiedSidecar := range verifiedSidecars {
+		blockRoot := verifiedSidecar.BlockRoot()
+		index := verifiedSidecar.Index
+
+		// Add to the result map grouped by block root
+		verifiedSidecarsByRoot[blockRoot] = append(verifiedSidecarsByRoot[blockRoot], verifiedSidecar)
+
+		if indices, ok := missingIndicesByRoot[blockRoot]; ok {
+			delete(indices, index)
+			if len(indices) == 0 {
+				delete(missingIndicesByRoot, blockRoot)
+			}
+		}
+	}
+
+	return verifiedSidecarsByRoot
+}
+
+// fetchDataColumnSidecarsFromPeers retrieves data column sidecars from peers.
+func fetchDataColumnSidecarsFromPeers(
+	params DataColumnSidecarsParams,
+	slotByRoot map[[fieldparams.RootLength]byte]primitives.Slot,
+	slotsWithCommitments map[primitives.Slot]bool,
+	indicesByRootByPeer map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool,
+) map[goPeer.ID][]blocks.RODataColumn {
+	var (
+		wg  sync.WaitGroup
+		mut sync.Mutex
+	)
+
+	roDataColumnsByPeer := make(map[goPeer.ID][]blocks.RODataColumn)
+	wg.Add(len(indicesByRootByPeer))
+	for peerID, indicesByRoot := range indicesByRootByPeer {
+		go func(peerID goPeer.ID, indicesByRoot map[[fieldparams.RootLength]byte]map[uint64]bool) {
+			defer wg.Done()
+
+			requestedCount := 0
+			for _, indices := range indicesByRoot {
+				requestedCount += len(indices)
+			}
+
+			log := log.WithFields(logrus.Fields{
+				"peerID":              peerID,
+				"agent":               agentString(peerID, params.P2P.Host()),
+				"blockCount":          len(indicesByRoot),
+				"totalRequestedCount": requestedCount,
+			})
+
+			roDataColumns, err := sendDataColumnSidecarsRequest(params, slotByRoot, slotsWithCommitments, peerID, indicesByRoot)
+			if err != nil {
+				log.WithError(err).Warning("Failed to send data column sidecars request")
+				return
+			}
+
+			mut.Lock()
+			defer mut.Unlock()
+			roDataColumnsByPeer[peerID] = roDataColumns
+		}(peerID, indicesByRoot)
+	}
+
+	wg.Wait()
+
+	return roDataColumnsByPeer
+}
+
+func sendDataColumnSidecarsRequest(
+	params DataColumnSidecarsParams,
+	slotByRoot map[[fieldparams.RootLength]byte]primitives.Slot,
+	slotsWithCommitments map[primitives.Slot]bool,
+	peerID goPeer.ID,
+	indicesByRoot map[[fieldparams.RootLength]byte]map[uint64]bool,
+) ([]blocks.RODataColumn, error) {
+	const batchSize = 32
+
+	rootCount := int64(len(indicesByRoot))
+	requestedSidecarsCount := 0
+	for _, indices := range indicesByRoot {
+		requestedSidecarsCount += len(indices)
+	}
+
+	log := log.WithFields(logrus.Fields{
+		"peerID":            peerID,
+		"agent":             agentString(peerID, params.P2P.Host()),
+		"requestedSidecars": requestedSidecarsCount,
+	})
+
+	// Try to build a by range byRangeRequest first.
+	byRangeRequests, err := buildByRangeRequests(slotByRoot, slotsWithCommitments, indicesByRoot, batchSize)
+	if err != nil {
+		return nil, errors.Wrap(err, "craft by range request")
+	}
+
+	// If we have a valid by range request, send it.
+	if len(byRangeRequests) > 0 {
+		count := 0
+		for _, indices := range indicesByRoot {
+			count += len(indices)
+		}
+
+		start := time.Now()
+		roDataColumns := make([]blocks.RODataColumn, 0, count)
+		for _, request := range byRangeRequests {
+			if params.RateLimiter != nil {
+				params.RateLimiter.Add(peerID.String(), rootCount)
+			}
+
+			localRoDataColumns, err := SendDataColumnSidecarsByRangeRequest(params, peerID, request)
+			if err != nil {
+				return nil, errors.Wrapf(err, "send data column sidecars by range request to peer %s", peerID)
+			}
+
+			roDataColumns = append(roDataColumns, localRoDataColumns...)
+		}
+
+		log.WithFields(logrus.Fields{
+			"respondedSidecars": len(roDataColumns),
+			"requests":          len(byRangeRequests),
+			"type":              "byRange",
+			"duration":          time.Since(start),
+		}).Debug("Received data column sidecars")
+
+		return roDataColumns, nil
+	}
+
+	// Build identifiers for the by root request.
+	byRootRequest := buildByRootRequest(indicesByRoot)
+
+	// Send the by root request.
+	start := time.Now()
+	if params.RateLimiter != nil {
+		params.RateLimiter.Add(peerID.String(), rootCount)
+	}
+	roDataColumns, err := SendDataColumnSidecarsByRootRequest(params, peerID, byRootRequest)
+	if err != nil {
+		return nil, errors.Wrapf(err, "send data column sidecars by root request to peer %s", peerID)
+	}
+
+	log.WithFields(logrus.Fields{
+		"respondedSidecars": len(roDataColumns),
+		"requests":          1,
+		"type":              "byRoot",
+		"duration":          time.Since(start),
+	}).Debug("Received data column sidecars")
+
+	return roDataColumns, nil
+}
+
+// buildByRangeRequests constructs a by range request from the given indices,
+// only if the indices are the same all blocks and if the blocks are contiguous.
+// (Missing blocks or blocks without commitments do count as contiguous)
+// If one of this condition is not met, returns nil.
+func buildByRangeRequests(
+	slotByRoot map[[fieldparams.RootLength]byte]primitives.Slot,
+	slotsWithCommitments map[primitives.Slot]bool,
+	indicesByRoot map[[fieldparams.RootLength]byte]map[uint64]bool,
+	batchSize uint64,
+) ([]*ethpb.DataColumnSidecarsByRangeRequest, error) {
+	if len(indicesByRoot) == 0 {
+		return nil, nil
+	}
+
+	var reference map[uint64]bool
+	slots := make([]primitives.Slot, 0, len(slotByRoot))
+	for root, indices := range indicesByRoot {
+		if reference == nil {
+			reference = indices
+		}
+
+		if !compareIndices(reference, indices) {
+			return nil, nil
+		}
+
+		slot, ok := slotByRoot[root]
+		if !ok {
+			return nil, errors.Errorf("slot not found for block root %#x", root)
+		}
+
+		slots = append(slots, slot)
+	}
+
+	slices.Sort(slots)
+
+	for i := 1; i < len(slots); i++ {
+		previous, current := slots[i-1], slots[i]
+		if current == previous+1 {
+			continue
+		}
+
+		for j := previous + 1; j < current; j++ {
+			if slotsWithCommitments[j] {
+				return nil, nil
+			}
+		}
+	}
+
+	columns := sortedSliceFromMap(reference)
+	startSlot, endSlot := slots[0], slots[len(slots)-1]
+	totalCount := uint64(endSlot - startSlot + 1)
+
+	requests := make([]*ethpb.DataColumnSidecarsByRangeRequest, 0, totalCount/batchSize)
+	for start := startSlot; start <= endSlot; start += primitives.Slot(batchSize) {
+		end := min(start+primitives.Slot(batchSize)-1, endSlot)
+		request := &ethpb.DataColumnSidecarsByRangeRequest{
+			StartSlot: start,
+			Count:     uint64(end - start + 1),
+			Columns:   columns,
+		}
+
+		requests = append(requests, request)
+	}
+
+	return requests, nil
+}
+
+// buildByRootRequest constructs a by root request from the given indices.
+func buildByRootRequest(indicesByRoot map[[fieldparams.RootLength]byte]map[uint64]bool) p2ptypes.DataColumnsByRootIdentifiers {
+	identifiers := make(p2ptypes.DataColumnsByRootIdentifiers, 0, len(indicesByRoot))
+	for root, indices := range indicesByRoot {
+		identifier := &eth.DataColumnsByRootIdentifier{
+			BlockRoot: root[:],
+			Columns:   sortedSliceFromMap(indices),
+		}
+		identifiers = append(identifiers, identifier)
+	}
+
+	// Sort identifiers to have a deterministic output.
+	slices.SortFunc(identifiers, func(left, right *eth.DataColumnsByRootIdentifier) int {
+		if cmp := bytes.Compare(left.BlockRoot, right.BlockRoot); cmp != 0 {
+			return cmp
+		}
+		return slices.Compare(left.Columns, right.Columns)
+	})
+
+	return identifiers
+}
+
+// verifyDataColumnSidecarsByPeer verifies the received data column sidecars.
+// If at least one sidecar from a peer is invalid, the peer is downscored and
+// all its sidecars are rejected. (Sidecars from other peers are still accepted.)
+func verifyDataColumnSidecarsByPeer(
+	p2p prysmP2P.P2P,
+	newVerifier verification.NewDataColumnsVerifier,
+	roDataColumnsByPeer map[goPeer.ID][]blocks.RODataColumn,
+) ([]blocks.VerifiedRODataColumn, error) {
+	// First optimistically verify all received data columns in a single batch.
+	count := 0
+	for _, columns := range roDataColumnsByPeer {
+		count += len(columns)
+	}
+
+	roDataColumnSidecars := make([]blocks.RODataColumn, 0, count)
+	for _, columns := range roDataColumnsByPeer {
+		roDataColumnSidecars = append(roDataColumnSidecars, columns...)
+	}
+
+	verifiedRoDataColumnSidecars, err := verifyByRootDataColumnSidecars(newVerifier, roDataColumnSidecars)
+	if err == nil {
+		// This is the happy path where all sidecars are verified.
+		return verifiedRoDataColumnSidecars, nil
+	}
+
+	// An error occurred during verification, which means that at least one sidecar is invalid.
+	// Reverify peer by peer to identify faulty peer(s), reject all its sidecars, and downscore it.
+	verifiedRoDataColumnSidecars = make([]blocks.VerifiedRODataColumn, 0, count)
+	for peer, columns := range roDataColumnsByPeer {
+		peerVerifiedRoDataColumnSidecars, err := verifyByRootDataColumnSidecars(newVerifier, columns)
+		if err != nil {
+			// This peer has invalid sidecars.
+			log := log.WithError(err).WithField("peerID", peer)
+			newScore := p2p.Peers().Scorers().BadResponsesScorer().Increment(peer)
+			log.Warning("Peer returned invalid data column sidecars")
+			log.WithFields(logrus.Fields{"reason": "invalidDataColumnSidecars", "newScore": newScore}).Debug("Downscore peer")
+		}
+
+		verifiedRoDataColumnSidecars = append(verifiedRoDataColumnSidecars, peerVerifiedRoDataColumnSidecars...)
+	}
+
+	return verifiedRoDataColumnSidecars, nil
+}
+
+// verifyByRootDataColumnSidecars verifies the provided read-only data columns against the
+// requirements for data column sidecars received via the by root request.
+func verifyByRootDataColumnSidecars(newVerifier verification.NewDataColumnsVerifier, roDataColumns []blocks.RODataColumn) ([]blocks.VerifiedRODataColumn, error) {
+	verifier := newVerifier(roDataColumns, verification.ByRootRequestDataColumnSidecarRequirements)
+
+	if err := verifier.ValidFields(); err != nil {
+		return nil, errors.Wrap(err, "valid fields")
+	}
+
+	if err := verifier.SidecarInclusionProven(); err != nil {
+		return nil, errors.Wrap(err, "sidecar inclusion proven")
+	}
+
+	if err := verifier.SidecarKzgProofVerified(); err != nil {
+		return nil, errors.Wrap(err, "sidecar KZG proof verified")
+	}
+
+	verifiedRoDataColumns, err := verifier.VerifiedRODataColumns()
+	if err != nil {
+		return nil, errors.Wrap(err, "verified RO data columns - should never happen")
+	}
+
+	return verifiedRoDataColumns, nil
+}
+
+// computeIndicesByRootByPeer returns a peers->root->indices map only for
+// root and indices given in `indicesByBlockRoot`. It also only selects peers
+// for a given root only if its head state is higher than the block slot.
+func computeIndicesByRootByPeer(
+	p2p prysmP2P.P2P,
+	slotByBlockRoot map[[fieldparams.RootLength]byte]primitives.Slot,
+	indicesByBlockRoot map[[fieldparams.RootLength]byte]map[uint64]bool,
+	peers map[goPeer.ID]bool,
+) (map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool, error) {
+	// First, compute custody columns for all peers
+	peersByIndex := make(map[uint64]map[goPeer.ID]bool)
+	headSlotByPeer := make(map[goPeer.ID]primitives.Slot)
+	for peer := range peers {
+		// Computes the custody columns for each peer
+		nodeID, err := prysmP2P.ConvertPeerIDToNodeID(peer)
+		if err != nil {
+			return nil, errors.Wrapf(err, "convert peer ID to node ID for peer %s", peer)
+		}
+
+		custodyGroupCount := p2p.CustodyGroupCountFromPeer(peer)
+
+		dasInfo, _, err := peerdas.Info(nodeID, custodyGroupCount)
+		if err != nil {
+			return nil, errors.Wrapf(err, "peerdas info for peer %s", peer)
+		}
+
+		for column := range dasInfo.CustodyColumns {
+			if _, exists := peersByIndex[column]; !exists {
+				peersByIndex[column] = make(map[goPeer.ID]bool)
+			}
+			peersByIndex[column][peer] = true
+		}
+
+		// Compute the head slot for each peer
+		peerChainState, err := p2p.Peers().ChainState(peer)
+		if err != nil {
+			return nil, errors.Wrapf(err, "get chain state for peer %s", peer)
+		}
+
+		if peerChainState == nil {
+			return nil, errors.Errorf("chain state is nil for peer %s", peer)
+		}
+
+		headSlotByPeer[peer] = peerChainState.HeadSlot
+	}
+
+	// For each block root and its indices, find suitable peers
+	indicesByRootByPeer := make(map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool)
+	for blockRoot, indices := range indicesByBlockRoot {
+		blockSlot, ok := slotByBlockRoot[blockRoot]
+		if !ok {
+			return nil, errors.Errorf("slot not found for block root %#x", blockRoot)
+		}
+
+		for index := range indices {
+			peers := peersByIndex[index]
+			for peer := range peers {
+				peerHeadSlot, ok := headSlotByPeer[peer]
+				if !ok {
+					return nil, errors.Errorf("head slot not found for peer %s", peer)
+				}
+
+				if peerHeadSlot < blockSlot {
+					continue
+				}
+
+				// Build peers->root->indices map
+				if _, exists := indicesByRootByPeer[peer]; !exists {
+					indicesByRootByPeer[peer] = make(map[[fieldparams.RootLength]byte]map[uint64]bool)
+				}
+				if _, exists := indicesByRootByPeer[peer][blockRoot]; !exists {
+					indicesByRootByPeer[peer][blockRoot] = make(map[uint64]bool)
+				}
+				indicesByRootByPeer[peer][blockRoot][index] = true
+			}
+		}
+	}
+
+	return indicesByRootByPeer, nil
+}
+
+// randomPeer selects a random peer. If no peers has enough bandwidth, it will wait and retry.
+// Returns the selected peer ID and any error.
+func randomPeer(
+	ctx context.Context,
+	randomSource *rand.Rand,
+	rateLimiter *leakybucket.Collector,
+	count int,
+	indicesByRootByPeer map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool,
+) (goPeer.ID, error) {
+	const waitPeriod = 5 * time.Second
+
+	peerCount := len(indicesByRootByPeer)
+	if peerCount == 0 {
+		return "", errors.New("no peers available")
+	}
+
+	for ctx.Err() == nil {
+		nonRateLimitedPeers := make([]goPeer.ID, 0, len(indicesByRootByPeer))
+		for peer := range indicesByRootByPeer {
+			if rateLimiter == nil || rateLimiter.Remaining(peer.String()) >= int64(count) {
+				nonRateLimitedPeers = append(nonRateLimitedPeers, peer)
+			}
+		}
+
+		slices.Sort(nonRateLimitedPeers)
+
+		if len(nonRateLimitedPeers) == 0 {
+			log.WithFields(logrus.Fields{
+				"peerCount": peerCount,
+				"delay":     waitPeriod,
+			}).Debug("Waiting for a peer with enough bandwidth for data column sidecars")
+			time.Sleep(waitPeriod)
+			continue
+		}
+
+		randomIndex := randomSource.Intn(len(nonRateLimitedPeers))
+		return nonRateLimitedPeers[randomIndex], nil
+	}
+
+	return "", ctx.Err()
+}
+
+// copyIndicesByRootByPeer creates a deep copy of the given nested map.
+// Returns a new map with the same structure and contents.
+func copyIndicesByRootByPeer(original map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool) map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool {
+	copied := make(map[goPeer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool, len(original))
+	for peer, indicesByRoot := range original {
+		copied[peer] = copyIndicesByRoot(indicesByRoot)
+	}
+
+	return copied
+}
+
+// copyIndicesByRoot creates a deep copy of the given nested map.
+// Returns a new map with the same structure and contents.
+func copyIndicesByRoot(original map[[fieldparams.RootLength]byte]map[uint64]bool) map[[fieldparams.RootLength]byte]map[uint64]bool {
+	copied := make(map[[fieldparams.RootLength]byte]map[uint64]bool, len(original))
+	for root, indexMap := range original {
+		copied[root] = make(map[uint64]bool, len(indexMap))
+		for index, value := range indexMap {
+			copied[root][index] = value
+		}
+	}
+	return copied
+}
+
+// compareIndices compares two map[uint64]bool and returns true if they are equal.
+func compareIndices(left, right map[uint64]bool) bool {
+	if len(left) != len(right) {
+		return false
+	}
+
+	for key, leftValue := range left {
+		rightValue, exists := right[key]
+		if !exists || leftValue != rightValue {
+			return false
+		}
+	}
+
+	return true
+}
+
+// sortedSliceFromMap converts a map[uint64]bool to a sorted slice of keys.
+func sortedSliceFromMap(m map[uint64]bool) []uint64 {
+	result := make([]uint64, 0, len(m))
+	for k := range m {
+		result = append(result, k)
+	}
+
+	slices.Sort(result)
+	return result
+}
+
+// computeSlotByBlockRoot maps each block root to its corresponding slot.
+func computeSlotByBlockRoot(roBlocks []blocks.ROBlock) map[[fieldparams.RootLength]byte]primitives.Slot {
+	slotByBlockRoot := make(map[[fieldparams.RootLength]byte]primitives.Slot, len(roBlocks))
+	for _, roBlock := range roBlocks {
+		slotByBlockRoot[roBlock.Root()] = roBlock.Block().Slot()
+	}
+	return slotByBlockRoot
+}
+
+// computeTotalCount calculates the total count of indices across all roots.
+func computeTotalCount(input map[[fieldparams.RootLength]byte]map[uint64]bool) int {
+	totalCount := 0
+	for _, indices := range input {
+		totalCount += len(indices)
+	}
+	return totalCount
+}

beacon-chain/sync/data_column_sidecars_test.go

@@ -0,0 +1,998 @@
+package sync
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain/kzg"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/peerdas"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/filesystem"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/peers"
+	testp2p "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/testing"
+	p2ptypes "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/types"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/startup"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/verification"
+	fieldparams "github.com/OffchainLabs/prysm/v6/config/fieldparams"
+	"github.com/OffchainLabs/prysm/v6/config/params"
+	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
+	"github.com/OffchainLabs/prysm/v6/consensus-types/primitives"
+	leakybucket "github.com/OffchainLabs/prysm/v6/container/leaky-bucket"
+	ethpb "github.com/OffchainLabs/prysm/v6/proto/prysm/v1alpha1"
+	"github.com/OffchainLabs/prysm/v6/testing/assert"
+	"github.com/OffchainLabs/prysm/v6/testing/require"
+	"github.com/OffchainLabs/prysm/v6/testing/util"
+	"github.com/libp2p/go-libp2p"
+	"github.com/libp2p/go-libp2p/core/crypto"
+	"github.com/libp2p/go-libp2p/core/network"
+	"github.com/libp2p/go-libp2p/core/peer"
+)
+
+func TestFetchDataColumnSidecars(t *testing.T) {
+	numberOfColumns := params.BeaconConfig().NumberOfColumns
+	// Slot 1: All needed sidecars are available in storage
+	// Slot 2: No commitment
+	// Slot 3: All sidecars are saved excepted the needed ones
+	// Slot 4: Some sidecars are in the storage, other have to be retrieved from peers.
+	// Slot 5: Some sidecars are in the storage, other have to be retrieved from peers but peers do not deliver all requested sidecars.
+
+	params.SetupTestConfigCleanup(t)
+	cfg := params.BeaconConfig().Copy()
+	cfg.FuluForkEpoch = 0
+	params.OverrideBeaconConfig(cfg)
+
+	// Start the trusted setup.
+	err := kzg.Start()
+	require.NoError(t, err)
+
+	storage := filesystem.NewEphemeralDataColumnStorage(t)
+
+	ctxMap, err := ContextByteVersionsForValRoot(params.BeaconConfig().GenesisValidatorsRoot)
+	require.NoError(t, err)
+
+	const blobCount = 3
+	indices := map[uint64]bool{31: true, 81: true, 106: true}
+
+	// Block 1
+	block1, _, verifiedSidecars1 := util.GenerateTestFuluBlockWithSidecars(t, blobCount, util.WithSlot(1))
+	root1 := block1.Root()
+
+	toStore1 := make([]blocks.VerifiedRODataColumn, 0, len(indices))
+	for index := range indices {
+		sidecar := verifiedSidecars1[index]
+		toStore1 = append(toStore1, sidecar)
+	}
+
+	err = storage.Save(toStore1)
+	require.NoError(t, err)
+
+	// Block 2
+	block2, _, _ := util.GenerateTestFuluBlockWithSidecars(t, 0, util.WithSlot(2))
+
+	// Block 3
+	block3, _, verifiedSidecars3 := util.GenerateTestFuluBlockWithSidecars(t, blobCount, util.WithSlot(3))
+	root3 := block3.Root()
+
+	toStore3 := make([]blocks.VerifiedRODataColumn, 0, numberOfColumns-uint64(len(indices)))
+	for i := range numberOfColumns {
+		if !indices[i] {
+			sidecar := verifiedSidecars3[i]
+			toStore3 = append(toStore3, sidecar)
+		}
+	}
+
+	err = storage.Save(toStore3)
+	require.NoError(t, err)
+
+	// Block 4
+	block4, _, verifiedSidecars4 := util.GenerateTestFuluBlockWithSidecars(t, blobCount, util.WithSlot(4))
+	root4 := block4.Root()
+	toStore4 := []blocks.VerifiedRODataColumn{verifiedSidecars4[106]}
+
+	err = storage.Save(toStore4)
+	require.NoError(t, err)
+
+	// Block 5
+	minimumColumnsCountToReconstruct := peerdas.MinimumColumnCountToReconstruct()
+	block5, _, verifiedSidecars5 := util.GenerateTestFuluBlockWithSidecars(t, blobCount, util.WithSlot(5))
+	root5 := block5.Root()
+
+	toStoreCount := minimumColumnsCountToReconstruct - 1
+	toStore5 := make([]blocks.VerifiedRODataColumn, 0, toStoreCount)
+
+	for i := uint64(0); uint64(len(toStore5)) < toStoreCount; i++ {
+		sidecar := verifiedSidecars5[minimumColumnsCountToReconstruct+i]
+		if sidecar.Index == 81 {
+			continue
+		}
+
+		toStore5 = append(toStore5, sidecar)
+	}
+
+	err = storage.Save(toStore5)
+	require.NoError(t, err)
+
+	// Custody columns with this private key and 4-cgc: 31, 81, 97, 105
+	privateKeyBytes := [32]byte{1}
+	privateKey, err := crypto.UnmarshalSecp256k1PrivateKey(privateKeyBytes[:])
+	require.NoError(t, err)
+
+	// Peers
+	protocol := fmt.Sprintf("%s/ssz_snappy", p2p.RPCDataColumnSidecarsByRangeTopicV1)
+
+	p2p, other := testp2p.NewTestP2P(t), testp2p.NewTestP2P(t, libp2p.Identity(privateKey))
+	p2p.Peers().SetConnectionState(other.PeerID(), peers.Connected)
+	p2p.Connect(other)
+
+	p2p.Peers().SetChainState(other.PeerID(), &ethpb.StatusV2{
+		HeadSlot: 5,
+	})
+
+	expectedRequest := &ethpb.DataColumnSidecarsByRangeRequest{
+		StartSlot: 4,
+		Count:     2,
+		Columns:   []uint64{31, 81},
+	}
+
+	clock := startup.NewClock(time.Now(), [fieldparams.RootLength]byte{})
+
+	gs := startup.NewClockSynchronizer()
+	err = gs.SetClock(startup.NewClock(time.Unix(4113849600, 0), [fieldparams.RootLength]byte{}))
+	require.NoError(t, err)
+
+	waiter := verification.NewInitializerWaiter(gs, nil, nil)
+	initializer, err := waiter.WaitForInitializer(t.Context())
+	require.NoError(t, err)
+
+	newDataColumnsVerifier := newDataColumnsVerifierFromInitializer(initializer)
+
+	other.SetStreamHandler(protocol, func(stream network.Stream) {
+		actualRequest := new(ethpb.DataColumnSidecarsByRangeRequest)
+		err := other.Encoding().DecodeWithMaxLength(stream, actualRequest)
+		assert.NoError(t, err)
+		assert.DeepEqual(t, expectedRequest, actualRequest)
+
+		err = WriteDataColumnSidecarChunk(stream, clock, other.Encoding(), verifiedSidecars4[31].DataColumnSidecar)
+		assert.NoError(t, err)
+
+		err = WriteDataColumnSidecarChunk(stream, clock, other.Encoding(), verifiedSidecars4[81].DataColumnSidecar)
+		assert.NoError(t, err)
+
+		err = WriteDataColumnSidecarChunk(stream, clock, other.Encoding(), verifiedSidecars5[81].DataColumnSidecar)
+		assert.NoError(t, err)
+
+		err = stream.CloseWrite()
+		assert.NoError(t, err)
+	})
+
+	params := DataColumnSidecarsParams{
+		Ctx:         t.Context(),
+		Tor:         clock,
+		P2P:         p2p,
+		RateLimiter: leakybucket.NewCollector(1., 10, time.Second, false /* deleteEmptyBuckets */),
+		CtxMap:      ctxMap,
+		Storage:     storage,
+		NewVerifier: newDataColumnsVerifier,
+	}
+
+	expected := map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn{
+		root1: {verifiedSidecars1[31], verifiedSidecars1[81], verifiedSidecars1[106]},
+		// no root2 (no commitments in this block)
+		root3: {verifiedSidecars3[31], verifiedSidecars3[81], verifiedSidecars3[106]},
+		root4: {verifiedSidecars4[31], verifiedSidecars4[81], verifiedSidecars4[106]},
+		root5: {verifiedSidecars5[31], verifiedSidecars5[81], verifiedSidecars5[106]},
+	}
+
+	blocks := []blocks.ROBlock{block1, block2, block3, block4, block5}
+	actual, err := FetchDataColumnSidecars(params, blocks, indices)
+	require.NoError(t, err)
+
+	require.Equal(t, len(expected), len(actual))
+	for root := range expected {
+		require.Equal(t, len(expected[root]), len(actual[root]))
+		for i := range expected[root] {
+			require.DeepSSZEqual(t, expected[root][i], actual[root][i])
+		}
+	}
+}
+
+func TestCategorizeIndices(t *testing.T) {
+	storage := filesystem.NewEphemeralDataColumnStorage(t)
+
+	_, verifiedRoSidecars := util.CreateTestVerifiedRoDataColumnSidecars(t, []util.DataColumnParam{
+		{Slot: 1, Index: 12, Column: [][]byte{{1}, {2}, {3}}},
+		{Slot: 1, Index: 14, Column: [][]byte{{1}, {2}, {3}}},
+	})
+
+	err := storage.Save(verifiedRoSidecars)
+	require.NoError(t, err)
+
+	expectedToQuery := map[uint64]bool{13: true}
+	expectedStored := map[uint64]bool{12: true, 14: true}
+
+	actualToQuery, actualStored := categorizeIndices(storage, verifiedRoSidecars[0].BlockRoot(), []uint64{12, 13, 14})
+
+	require.Equal(t, len(expectedToQuery), len(actualToQuery))
+	require.Equal(t, len(expectedStored), len(actualStored))
+
+	for index := range expectedToQuery {
+		require.Equal(t, true, actualToQuery[index])
+	}
+	for index := range expectedStored {
+		require.Equal(t, true, actualStored[index])
+	}
+}
+
+func TestSelectPeers(t *testing.T) {
+	const (
+		count = 3
+		seed  = 42
+	)
+
+	params := DataColumnSidecarsParams{
+		Ctx:         t.Context(),
+		RateLimiter: leakybucket.NewCollector(1., 10, time.Second, false /* deleteEmptyBuckets */),
+	}
+
+	randomSource := rand.New(rand.NewSource(seed))
+
+	indicesByRootByPeer := map[peer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool{
+		"peer1": {
+			{1}: {12: true, 13: true},
+			{2}: {13: true, 14: true, 15: true},
+			{3}: {14: true, 15: true},
+		},
+		"peer2": {
+			{1}: {13: true, 14: true},
+			{2}: {13: true, 14: true, 15: true},
+			{3}: {14: true, 16: true},
+		},
+	}
+
+	expected := map[peer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool{
+		"peer1": {
+			{1}: {12: true},
+			{3}: {15: true},
+		},
+		"peer2": {
+			{1}: {13: true, 14: true},
+			{2}: {13: true, 14: true, 15: true},
+			{3}: {14: true, 16: true},
+		},
+	}
+
+	actual, err := selectPeers(params, randomSource, count, indicesByRootByPeer)
+
+	require.NoError(t, err)
+	require.Equal(t, len(expected), len(actual))
+	for peerID := range expected {
+		require.Equal(t, len(expected[peerID]), len(actual[peerID]))
+		for root := range expected[peerID] {
+			require.Equal(t, len(expected[peerID][root]), len(actual[peerID][root]))
+			for indices := range expected[peerID][root] {
+				require.Equal(t, expected[peerID][root][indices], actual[peerID][root][indices])
+			}
+		}
+	}
+}
+
+func TestUpdateResults(t *testing.T) {
+	_, verifiedSidecars := util.CreateTestVerifiedRoDataColumnSidecars(t, []util.DataColumnParam{
+		{Slot: 1, Index: 12, Column: [][]byte{{1}, {2}, {3}}},
+		{Slot: 1, Index: 13, Column: [][]byte{{1}, {2}, {3}}},
+		{Slot: 2, Index: 13, Column: [][]byte{{1}, {2}, {3}}},
+		{Slot: 2, Index: 14, Column: [][]byte{{1}, {2}, {3}}},
+	})
+
+	missingIndicesByRoot := map[[fieldparams.RootLength]byte]map[uint64]bool{
+		verifiedSidecars[0].BlockRoot(): {12: true, 13: true},
+		verifiedSidecars[2].BlockRoot(): {13: true, 14: true, 15: true},
+	}
+
+	expectedMissingIndicesByRoot := map[[fieldparams.RootLength]byte]map[uint64]bool{
+		verifiedSidecars[2].BlockRoot(): {15: true},
+	}
+
+	expectedVerifiedSidecarsByRoot := map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn{
+		verifiedSidecars[0].BlockRoot(): {verifiedSidecars[0], verifiedSidecars[1]},
+		verifiedSidecars[2].BlockRoot(): {verifiedSidecars[2], verifiedSidecars[3]},
+	}
+
+	actualVerifiedSidecarsByRoot := updateResults(verifiedSidecars, missingIndicesByRoot)
+	require.DeepEqual(t, expectedMissingIndicesByRoot, missingIndicesByRoot)
+	require.DeepEqual(t, expectedVerifiedSidecarsByRoot, actualVerifiedSidecarsByRoot)
+}
+
+func TestFetchDataColumnSidecarsFromPeers(t *testing.T) {
+	const count = 4
+
+	params.SetupTestConfigCleanup(t)
+	cfg := params.BeaconConfig().Copy()
+	cfg.FuluForkEpoch = 0
+	params.OverrideBeaconConfig(cfg)
+
+	clock := startup.NewClock(time.Now(), [fieldparams.RootLength]byte{})
+	ctxMap, err := ContextByteVersionsForValRoot(params.BeaconConfig().GenesisValidatorsRoot)
+	require.NoError(t, err)
+
+	kzgCommitmentsInclusionProof := make([][]byte, 0, count)
+	for range count {
+		kzgCommitmentsInclusionProof = append(kzgCommitmentsInclusionProof, make([]byte, 32))
+	}
+
+	expectedResponseSidecarPb := &ethpb.DataColumnSidecar{
+		Index: 2,
+		SignedBlockHeader: &ethpb.SignedBeaconBlockHeader{
+			Header: &ethpb.BeaconBlockHeader{
+				Slot:       1,
+				ParentRoot: make([]byte, fieldparams.RootLength),
+				StateRoot:  make([]byte, fieldparams.RootLength),
+				BodyRoot:   make([]byte, fieldparams.RootLength),
+			},
+			Signature: make([]byte, fieldparams.BLSSignatureLength),
+		},
+		KzgCommitmentsInclusionProof: kzgCommitmentsInclusionProof,
+	}
+
+	expectedResponseSidecar, err := blocks.NewRODataColumn(expectedResponseSidecarPb)
+	require.NoError(t, err)
+
+	slotByRoot := map[[fieldparams.RootLength]byte]primitives.Slot{
+		{1}: 1,
+		{3}: 3,
+		{4}: 4,
+		{7}: 7,
+	}
+
+	slotsWithCommitments := map[primitives.Slot]bool{
+		1: true,
+		3: true,
+		4: true,
+		7: true,
+	}
+
+	expectedRequest := &ethpb.DataColumnSidecarsByRangeRequest{
+		StartSlot: 1,
+		Count:     7,
+		Columns:   []uint64{1, 2},
+	}
+
+	protocol := fmt.Sprintf("%s/ssz_snappy", p2p.RPCDataColumnSidecarsByRangeTopicV1)
+	p2p, other := testp2p.NewTestP2P(t), testp2p.NewTestP2P(t)
+	p2p.Connect(other)
+
+	other.SetStreamHandler(protocol, func(stream network.Stream) {
+		receivedRequest := new(ethpb.DataColumnSidecarsByRangeRequest)
+		err := other.Encoding().DecodeWithMaxLength(stream, receivedRequest)
+		assert.NoError(t, err)
+		assert.DeepEqual(t, expectedRequest, receivedRequest)
+
+		err = WriteDataColumnSidecarChunk(stream, clock, other.Encoding(), expectedResponseSidecarPb)
+		assert.NoError(t, err)
+
+		err = stream.CloseWrite()
+		assert.NoError(t, err)
+	})
+
+	indicesByRootByPeer := map[peer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool{
+		other.PeerID(): {
+			{1}: {1: true, 2: true},
+			{3}: {1: true, 2: true},
+			{4}: {1: true, 2: true},
+			{7}: {1: true, 2: true},
+		},
+	}
+
+	params := DataColumnSidecarsParams{
+		Ctx:         t.Context(),
+		Tor:         clock,
+		P2P:         p2p,
+		CtxMap:      ctxMap,
+		RateLimiter: leakybucket.NewCollector(1., 1, time.Second, false /* deleteEmptyBuckets */),
+	}
+
+	expectedResponse := map[peer.ID][]blocks.RODataColumn{
+		other.PeerID(): {expectedResponseSidecar},
+	}
+
+	actualResponse := fetchDataColumnSidecarsFromPeers(params, slotByRoot, slotsWithCommitments, indicesByRootByPeer)
+	require.Equal(t, len(expectedResponse), len(actualResponse))
+
+	for peerID := range expectedResponse {
+		require.DeepSSZEqual(t, expectedResponse[peerID], actualResponse[peerID])
+	}
+}
+
+func TestSendDataColumnSidecarsRequest(t *testing.T) {
+	const count = 4
+
+	params.SetupTestConfigCleanup(t)
+	cfg := params.BeaconConfig().Copy()
+	cfg.FuluForkEpoch = 0
+	params.OverrideBeaconConfig(cfg)
+
+	kzgCommitmentsInclusionProof := make([][]byte, 0, count)
+	for range count {
+		kzgCommitmentsInclusionProof = append(kzgCommitmentsInclusionProof, make([]byte, 32))
+	}
+
+	expectedResponsePb := &ethpb.DataColumnSidecar{
+		Index: 2,
+		SignedBlockHeader: &ethpb.SignedBeaconBlockHeader{
+			Header: &ethpb.BeaconBlockHeader{
+				Slot:       1,
+				ParentRoot: make([]byte, fieldparams.RootLength),
+				StateRoot:  make([]byte, fieldparams.RootLength),
+				BodyRoot:   make([]byte, fieldparams.RootLength),
+			},
+			Signature: make([]byte, fieldparams.BLSSignatureLength),
+		},
+		KzgCommitmentsInclusionProof: kzgCommitmentsInclusionProof,
+	}
+
+	expectedResponse, err := blocks.NewRODataColumn(expectedResponsePb)
+	require.NoError(t, err)
+
+	clock := startup.NewClock(time.Now(), params.BeaconConfig().GenesisValidatorsRoot)
+	ctxMap, err := ContextByteVersionsForValRoot(params.BeaconConfig().GenesisValidatorsRoot)
+	require.NoError(t, err)
+
+	t.Run("contiguous", func(t *testing.T) {
+		indicesByRoot := map[[fieldparams.RootLength]byte]map[uint64]bool{
+			{1}: {1: true, 2: true},
+			{3}: {1: true, 2: true},
+			{4}: {1: true, 2: true},
+			{7}: {1: true, 2: true},
+		}
+
+		slotByRoot := map[[fieldparams.RootLength]byte]primitives.Slot{
+			{1}: 1,
+			{3}: 3,
+			{4}: 4,
+			{7}: 7,
+		}
+
+		slotsWithCommitments := map[primitives.Slot]bool{
+			1: true,
+			3: true,
+			4: true,
+			7: true,
+		}
+
+		expectedRequest := &ethpb.DataColumnSidecarsByRangeRequest{
+			StartSlot: 1,
+			Count:     7,
+			Columns:   []uint64{1, 2},
+		}
+
+		protocol := fmt.Sprintf("%s/ssz_snappy", p2p.RPCDataColumnSidecarsByRangeTopicV1)
+		p2p, other := testp2p.NewTestP2P(t), testp2p.NewTestP2P(t)
+		p2p.Connect(other)
+
+		other.SetStreamHandler(protocol, func(stream network.Stream) {
+			receivedRequest := new(ethpb.DataColumnSidecarsByRangeRequest)
+			err := other.Encoding().DecodeWithMaxLength(stream, receivedRequest)
+			assert.NoError(t, err)
+			assert.DeepEqual(t, expectedRequest, receivedRequest)
+
+			err = WriteDataColumnSidecarChunk(stream, clock, other.Encoding(), expectedResponsePb)
+			assert.NoError(t, err)
+
+			err = stream.CloseWrite()
+			assert.NoError(t, err)
+		})
+
+		params := DataColumnSidecarsParams{
+			Ctx:         t.Context(),
+			Tor:         clock,
+			P2P:         p2p,
+			CtxMap:      ctxMap,
+			RateLimiter: leakybucket.NewCollector(1., 1, time.Second, false /* deleteEmptyBuckets */),
+		}
+
+		actualResponse, err := sendDataColumnSidecarsRequest(params, slotByRoot, slotsWithCommitments, other.PeerID(), indicesByRoot)
+		require.NoError(t, err)
+		require.DeepEqual(t, expectedResponse, actualResponse[0])
+	})
+
+	t.Run("non contiguous", func(t *testing.T) {
+		indicesByRoot := map[[fieldparams.RootLength]byte]map[uint64]bool{
+			expectedResponse.BlockRoot(): {1: true, 2: true},
+			{4}:                          {1: true, 2: true},
+			{7}:                          {1: true, 2: true},
+		}
+
+		slotByRoot := map[[fieldparams.RootLength]byte]primitives.Slot{
+			expectedResponse.BlockRoot(): 1,
+			{4}:                          4,
+			{7}:                          7,
+		}
+
+		slotsWithCommitments := map[primitives.Slot]bool{
+			1: true,
+			3: true,
+			4: true,
+			7: true,
+		}
+
+		roots := [...][fieldparams.RootLength]byte{expectedResponse.BlockRoot(), {4}, {7}}
+
+		expectedRequest := &p2ptypes.DataColumnsByRootIdentifiers{
+			{
+				BlockRoot: roots[1][:],
+				Columns:   []uint64{1, 2},
+			},
+			{
+				BlockRoot: roots[2][:],
+				Columns:   []uint64{1, 2},
+			},
+			{
+				BlockRoot: roots[0][:],
+				Columns:   []uint64{1, 2},
+			},
+		}
+
+		protocol := fmt.Sprintf("%s/ssz_snappy", p2p.RPCDataColumnSidecarsByRootTopicV1)
+		p2p, other := testp2p.NewTestP2P(t), testp2p.NewTestP2P(t)
+		p2p.Connect(other)
+
+		other.SetStreamHandler(protocol, func(stream network.Stream) {
+			receivedRequest := new(p2ptypes.DataColumnsByRootIdentifiers)
+			err := other.Encoding().DecodeWithMaxLength(stream, receivedRequest)
+			assert.NoError(t, err)
+			assert.DeepSSZEqual(t, *expectedRequest, *receivedRequest)
+
+			err = WriteDataColumnSidecarChunk(stream, clock, other.Encoding(), expectedResponsePb)
+			assert.NoError(t, err)
+
+			err = stream.CloseWrite()
+			assert.NoError(t, err)
+		})
+
+		params := DataColumnSidecarsParams{
+			Ctx:         t.Context(),
+			Tor:         clock,
+			P2P:         p2p,
+			CtxMap:      ctxMap,
+			RateLimiter: leakybucket.NewCollector(1., 1, time.Second, false /* deleteEmptyBuckets */),
+		}
+
+		actualResponse, err := sendDataColumnSidecarsRequest(params, slotByRoot, slotsWithCommitments, other.PeerID(), indicesByRoot)
+		require.NoError(t, err)
+		require.DeepEqual(t, expectedResponse, actualResponse[0])
+	})
+}
+
+func TestBuildByRangeRequests(t *testing.T) {
+	const nullBatchSize = 0
+
+	t.Run("empty", func(t *testing.T) {
+		actual, err := buildByRangeRequests(nil, nil, nil, nullBatchSize)
+		require.NoError(t, err)
+
+		require.Equal(t, 0, len(actual))
+	})
+
+	t.Run("missing Root", func(t *testing.T) {
+		indicesByRoot := map[[fieldparams.RootLength]byte]map[uint64]bool{
+			{1}: {1: true, 2: true},
+		}
+
+		_, err := buildByRangeRequests(nil, nil, indicesByRoot, nullBatchSize)
+		require.NotNil(t, err)
+	})
+
+	t.Run("indices differ", func(t *testing.T) {
+		indicesByRoot := map[[fieldparams.RootLength]byte]map[uint64]bool{
+			{1}: {1: true, 2: true},
+			{2}: {1: true, 2: true},
+			{3}: {2: true, 3: true},
+		}
+
+		slotByRoot := map[[fieldparams.RootLength]byte]primitives.Slot{
+			{1}: 1,
+			{2}: 2,
+			{3}: 3,
+		}
+
+		actual, err := buildByRangeRequests(slotByRoot, nil, indicesByRoot, nullBatchSize)
+		require.NoError(t, err)
+		require.Equal(t, 0, len(actual))
+	})
+
+	t.Run("slots non contiguous", func(t *testing.T) {
+		indicesByRoot := map[[fieldparams.RootLength]byte]map[uint64]bool{
+			{1}: {1: true, 2: true},
+			{2}: {1: true, 2: true},
+		}
+
+		slotByRoot := map[[fieldparams.RootLength]byte]primitives.Slot{
+			{1}: 1,
+			{2}: 3,
+		}
+
+		slotsWithCommitments := map[primitives.Slot]bool{
+			1: true,
+			2: true,
+			3: true,
+		}
+
+		actual, err := buildByRangeRequests(slotByRoot, slotsWithCommitments, indicesByRoot, nullBatchSize)
+		require.NoError(t, err)
+		require.Equal(t, 0, len(actual))
+	})
+
+	t.Run("nominal", func(t *testing.T) {
+		const batchSize = 3
+
+		indicesByRoot := map[[fieldparams.RootLength]byte]map[uint64]bool{
+			{1}: {1: true, 2: true},
+			{3}: {1: true, 2: true},
+			{4}: {1: true, 2: true},
+			{7}: {1: true, 2: true},
+		}
+
+		slotByRoot := map[[fieldparams.RootLength]byte]primitives.Slot{
+			{1}: 1,
+			{3}: 3,
+			{4}: 4,
+			{7}: 7,
+		}
+
+		slotsWithCommitments := map[primitives.Slot]bool{
+			1: true,
+			3: true,
+			4: true,
+			7: true,
+		}
+
+		expected := []*ethpb.DataColumnSidecarsByRangeRequest{
+			{
+				StartSlot: 1,
+				Count:     3,
+				Columns:   []uint64{1, 2},
+			},
+			{
+				StartSlot: 4,
+				Count:     3,
+				Columns:   []uint64{1, 2},
+			},
+			{
+				StartSlot: 7,
+				Count:     1,
+				Columns:   []uint64{1, 2},
+			},
+		}
+
+		actual, err := buildByRangeRequests(slotByRoot, slotsWithCommitments, indicesByRoot, batchSize)
+		require.NoError(t, err)
+		require.DeepEqual(t, expected, actual)
+	})
+}
+
+func TestBuildByRootRequest(t *testing.T) {
+	root1 := [fieldparams.RootLength]byte{1}
+	root2 := [fieldparams.RootLength]byte{2}
+
+	input := map[[fieldparams.RootLength]byte]map[uint64]bool{
+		root1: {1: true, 2: true},
+		root2: {3: true},
+	}
+
+	expected := p2ptypes.DataColumnsByRootIdentifiers{
+		{
+			BlockRoot: root1[:],
+			Columns:   []uint64{1, 2},
+		},
+		{
+			BlockRoot: root2[:],
+			Columns:   []uint64{3},
+		},
+	}
+
+	actual := buildByRootRequest(input)
+	require.DeepSSZEqual(t, expected, actual)
+}
+
+func TestVerifyDataColumnSidecarsByPeer(t *testing.T) {
+	err := kzg.Start()
+	require.NoError(t, err)
+
+	t.Run("nominal", func(t *testing.T) {
+		const (
+			start, stop = 0, 15
+			blobCount   = 1
+		)
+
+		p2p := testp2p.NewTestP2P(t)
+
+		// Setup test data and expectations
+		_, roDataColumnSidecars, expected := util.GenerateTestFuluBlockWithSidecars(t, blobCount)
+
+		roDataColumnsByPeer := map[peer.ID][]blocks.RODataColumn{
+			"peer1": roDataColumnSidecars[start:5],
+			"peer2": roDataColumnSidecars[5:9],
+			"peer3": roDataColumnSidecars[9:stop],
+		}
+		gs := startup.NewClockSynchronizer()
+		err := gs.SetClock(startup.NewClock(time.Unix(4113849600, 0), [fieldparams.RootLength]byte{}))
+		require.NoError(t, err)
+
+		waiter := verification.NewInitializerWaiter(gs, nil, nil)
+		initializer, err := waiter.WaitForInitializer(t.Context())
+		require.NoError(t, err)
+
+		newDataColumnsVerifier := newDataColumnsVerifierFromInitializer(initializer)
+		actual, err := verifyDataColumnSidecarsByPeer(p2p, newDataColumnsVerifier, roDataColumnsByPeer)
+		require.NoError(t, err)
+
+		require.Equal(t, stop-start, len(actual))
+
+		for i := range actual {
+			actualSidecar := actual[i]
+			index := actualSidecar.Index
+			expectedSidecar := expected[index]
+			require.DeepEqual(t, expectedSidecar, actualSidecar)
+		}
+	})
+
+	t.Run("one rogue peer", func(t *testing.T) {
+		const (
+			start, middle, stop = 0, 5, 15
+			blobCount           = 1
+		)
+
+		p2p := testp2p.NewTestP2P(t)
+
+		// Setup test data and expectations
+		_, roDataColumnSidecars, expected := util.GenerateTestFuluBlockWithSidecars(t, blobCount)
+
+		// Modify one sidecar to ensure proof verification fails.
+		if roDataColumnSidecars[middle].KzgProofs[0][0] == 0 {
+			roDataColumnSidecars[middle].KzgProofs[0][0]++
+		} else {
+			roDataColumnSidecars[middle].KzgProofs[0][0]--
+		}
+
+		roDataColumnsByPeer := map[peer.ID][]blocks.RODataColumn{
+			"peer1": roDataColumnSidecars[start:middle],
+			"peer2": roDataColumnSidecars[5:middle],
+			"peer3": roDataColumnSidecars[middle:stop],
+		}
+		gs := startup.NewClockSynchronizer()
+		err := gs.SetClock(startup.NewClock(time.Unix(4113849600, 0), [fieldparams.RootLength]byte{}))
+		require.NoError(t, err)
+
+		waiter := verification.NewInitializerWaiter(gs, nil, nil)
+		initializer, err := waiter.WaitForInitializer(t.Context())
+		require.NoError(t, err)
+
+		newDataColumnsVerifier := newDataColumnsVerifierFromInitializer(initializer)
+		actual, err := verifyDataColumnSidecarsByPeer(p2p, newDataColumnsVerifier, roDataColumnsByPeer)
+		require.NoError(t, err)
+
+		require.Equal(t, middle-start, len(actual))
+
+		for i := range actual {
+			actualSidecar := actual[i]
+			index := actualSidecar.Index
+			expectedSidecar := expected[index]
+			require.DeepEqual(t, expectedSidecar, actualSidecar)
+		}
+	})
+}
+
+func TestComputeIndicesByRootByPeer(t *testing.T) {
+	peerIdStrs := []string{
+		"16Uiu2HAm3k5Npu6EaYWxiEvzsdLseEkjVyoVhvbxWEuyqdBgBBbq", // Custodies 89, 94, 97 & 122
+		"16Uiu2HAmTwQPAwzTr6hTgBmKNecCfH6kP3Kbzxj36ZRyyQ46L6gf", // Custodies 1, 11, 37 & 86
+		"16Uiu2HAmMDB5uUePTpN7737m78ehePfWPtBL9qMGdH8kCygjzNA8", // Custodies 2, 37, 38 & 68
+		"16Uiu2HAmTAE5Vxf7Pgfk7eWpmCvVJdSba4C9xg4xkYuuvnVbgfFx", // Custodies 10, 29, 36 & 108
+	}
+
+	headSlotByPeer := map[string]primitives.Slot{
+		"16Uiu2HAm3k5Npu6EaYWxiEvzsdLseEkjVyoVhvbxWEuyqdBgBBbq": 89,
+		"16Uiu2HAmTwQPAwzTr6hTgBmKNecCfH6kP3Kbzxj36ZRyyQ46L6gf": 10,
+		"16Uiu2HAmMDB5uUePTpN7737m78ehePfWPtBL9qMGdH8kCygjzNA8": 12,
+		"16Uiu2HAmTAE5Vxf7Pgfk7eWpmCvVJdSba4C9xg4xkYuuvnVbgfFx": 9,
+	}
+
+	p2p := testp2p.NewTestP2P(t)
+	peers := p2p.Peers()
+
+	peerIDs := make([]peer.ID, 0, len(peerIdStrs))
+	for _, peerIdStr := range peerIdStrs {
+		peerID, err := peer.Decode(peerIdStr)
+		require.NoError(t, err)
+
+		peers.SetChainState(peerID, &ethpb.StatusV2{
+			HeadSlot: headSlotByPeer[peerIdStr],
+		})
+
+		peerIDs = append(peerIDs, peerID)
+	}
+
+	slotByBlockRoot := map[[fieldparams.RootLength]byte]primitives.Slot{
+		[fieldparams.RootLength]byte{1}: 8,
+		[fieldparams.RootLength]byte{2}: 10,
+		[fieldparams.RootLength]byte{3}: 9,
+		[fieldparams.RootLength]byte{4}: 50,
+	}
+
+	indicesByBlockRoot := map[[fieldparams.RootLength]byte]map[uint64]bool{
+		[fieldparams.RootLength]byte{1}: {3: true, 4: true, 5: true},
+		[fieldparams.RootLength]byte{2}: {1: true, 10: true, 37: true, 80: true},
+		[fieldparams.RootLength]byte{3}: {10: true, 38: true, 39: true, 40: true},
+		[fieldparams.RootLength]byte{4}: {89: true, 108: true, 122: true},
+	}
+
+	expected := map[peer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool{
+		peerIDs[0]: {
+			[fieldparams.RootLength]byte{4}: {89: true, 122: true},
+		},
+		peerIDs[1]: {
+			[fieldparams.RootLength]byte{2}: {1: true, 37: true},
+		},
+		peerIDs[2]: {
+			[fieldparams.RootLength]byte{2}: {37: true},
+			[fieldparams.RootLength]byte{3}: {38: true},
+		},
+		peerIDs[3]: {
+			[fieldparams.RootLength]byte{3}: {10: true},
+		},
+	}
+
+	peerIDsMap := make(map[peer.ID]bool, len(peerIDs))
+	for _, id := range peerIDs {
+		peerIDsMap[id] = true
+	}
+
+	actual, err := computeIndicesByRootByPeer(p2p, slotByBlockRoot, indicesByBlockRoot, peerIDsMap)
+	require.NoError(t, err)
+	require.Equal(t, len(expected), len(actual))
+
+	for peer, indicesByRoot := range expected {
+		require.Equal(t, len(indicesByRoot), len(actual[peer]))
+		for root, indices := range indicesByRoot {
+			require.Equal(t, len(indices), len(actual[peer][root]))
+			for index := range indices {
+				require.Equal(t, actual[peer][root][index], true)
+			}
+		}
+	}
+}
+
+func TestRandomPeer(t *testing.T) {
+	// Fixed seed.
+	const seed = 43
+	randomSource := rand.New(rand.NewSource(seed))
+
+	t.Run("no peers", func(t *testing.T) {
+		pid, err := randomPeer(t.Context(), randomSource, leakybucket.NewCollector(4, 8, time.Second, false /* deleteEmptyBuckets */), 1, nil)
+		require.NotNil(t, err)
+		require.Equal(t, peer.ID(""), pid)
+	})
+
+	t.Run("context cancelled", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(t.Context())
+		cancel()
+
+		indicesByRootByPeer := map[peer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool{peer.ID("peer1"): {}}
+		pid, err := randomPeer(ctx, randomSource, leakybucket.NewCollector(4, 8, time.Second, false /* deleteEmptyBuckets */), 1, indicesByRootByPeer)
+		require.NotNil(t, err)
+		require.Equal(t, peer.ID(""), pid)
+	})
+
+	t.Run("nominal", func(t *testing.T) {
+		const count = 1
+		collector := leakybucket.NewCollector(4, 8, time.Second, false /* deleteEmptyBuckets */)
+		peer1, peer2, peer3 := peer.ID("peer1"), peer.ID("peer2"), peer.ID("peer3")
+
+		indicesByRootByPeer := map[peer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool{
+			peer1: {},
+			peer2: {},
+			peer3: {},
+		}
+
+		pid, err := randomPeer(t.Context(), randomSource, collector, count, indicesByRootByPeer)
+		require.NoError(t, err)
+		require.Equal(t, peer1, pid)
+
+		pid, err = randomPeer(t.Context(), randomSource, collector, count, indicesByRootByPeer)
+		require.NoError(t, err)
+		require.Equal(t, peer2, pid)
+	})
+}
+
+func TestCopyIndicesByRootByPeer(t *testing.T) {
+	original := map[peer.ID]map[[fieldparams.RootLength]byte]map[uint64]bool{
+		peer.ID("peer1"): {
+			[fieldparams.RootLength]byte{1}: {1: true, 3: true},
+			[fieldparams.RootLength]byte{2}: {2: true},
+		},
+		peer.ID("peer2"): {
+			[fieldparams.RootLength]byte{1}: {1: true},
+		},
+	}
+
+	copied := copyIndicesByRootByPeer(original)
+
+	require.Equal(t, len(original), len(copied))
+	for peer, indicesByRoot := range original {
+		require.Equal(t, len(indicesByRoot), len(copied[peer]))
+		for root, indices := range indicesByRoot {
+			require.Equal(t, len(indices), len(copied[peer][root]))
+			for index := range indices {
+				require.Equal(t, copied[peer][root][index], true)
+			}
+		}
+	}
+}
+
+func TestCompareIndices(t *testing.T) {
+	left := map[uint64]bool{3: true, 5: true, 7: true}
+	right := map[uint64]bool{5: true}
+	require.Equal(t, false, compareIndices(left, right))
+
+	left = map[uint64]bool{3: true, 5: true, 7: true}
+	right = map[uint64]bool{3: true, 6: true, 7: true}
+	require.Equal(t, false, compareIndices(left, right))
+
+	left = map[uint64]bool{3: true, 5: true, 7: true}
+	right = map[uint64]bool{5: true, 7: true, 3: true}
+	require.Equal(t, true, compareIndices(left, right))
+}
+
+func TestSlortedSliceFromMap(t *testing.T) {
+	input := map[uint64]bool{54: true, 23: true, 35: true}
+	expected := []uint64{23, 35, 54}
+	actual := sortedSliceFromMap(input)
+	require.DeepEqual(t, expected, actual)
+}
+
+func TestComputeSlotByBlockRoot(t *testing.T) {
+	const (
+		count      = 3
+		multiplier = 10
+	)
+
+	roBlocks := make([]blocks.ROBlock, 0, count)
+	for i := range count {
+		signedBlock := util.NewBeaconBlock()
+		signedBlock.Block.Slot = primitives.Slot(i).Mul(multiplier)
+		roSignedBlock, err := blocks.NewSignedBeaconBlock(signedBlock)
+		require.NoError(t, err)
+
+		roBlock, err := blocks.NewROBlockWithRoot(roSignedBlock, [fieldparams.RootLength]byte{byte(i)})
+		require.NoError(t, err)
+
+		roBlocks = append(roBlocks, roBlock)
+	}
+
+	expected := map[[fieldparams.RootLength]byte]primitives.Slot{
+		[fieldparams.RootLength]byte{0}: primitives.Slot(0),
+		[fieldparams.RootLength]byte{1}: primitives.Slot(10),
+		[fieldparams.RootLength]byte{2}: primitives.Slot(20),
+	}
+
+	actual := computeSlotByBlockRoot(roBlocks)
+
+	require.Equal(t, len(expected), len(actual))
+	for k, v := range expected {
+		require.Equal(t, v, actual[k])
+	}
+}
+
+func TestComputeTotalCount(t *testing.T) {
+	input := map[[fieldparams.RootLength]byte]map[uint64]bool{
+		[fieldparams.RootLength]byte{1}: {1: true, 3: true},
+		[fieldparams.RootLength]byte{2}: {2: true},
+	}
+
+	const expected = 3
+	actual := computeTotalCount(input)
+	require.Equal(t, expected, actual)
+}

beacon-chain/sync/data_columns_reconstruct.go

@@ -44,7 +44,7 @@ func (s *Service) reconstructSaveBroadcastDataColumnSidecars(
 	numberOfColumns := params.BeaconConfig().NumberOfColumns
 
 	// If reconstruction is not possible or if all columns are already stored, exit early.
-	if storedColumnsCount < peerdas.MinimumColumnsCountToReconstruct() || storedColumnsCount == numberOfColumns {
+	if storedColumnsCount < peerdas.MinimumColumnCountToReconstruct() || storedColumnsCount == numberOfColumns {
 		return nil
 	}
 
@@ -198,7 +198,7 @@ func (s *Service) broadcastMissingDataColumnSidecars(
 		subnet := peerdas.ComputeSubnetForDataColumnSidecar(verifiedRODataColumn.Index)
 
 		// Broadcast the missing data column.
-		if err := s.cfg.p2p.BroadcastDataColumn(root, subnet, verifiedRODataColumn.DataColumnSidecar); err != nil {
+		if err := s.cfg.p2p.BroadcastDataColumnSidecar(root, subnet, verifiedRODataColumn.DataColumnSidecar); err != nil {
 			log.WithError(err).Error("Broadcast data column")
 		}
 

beacon-chain/sync/data_columns_reconstruct_test.go

@@ -30,7 +30,7 @@ func TestReconstructDataColumns(t *testing.T) {
 	root, block := roBlock.Root(), roBlock.Block()
 	slot, proposerIndex := block.Slot(), block.ProposerIndex()
 
-	minimumCount := peerdas.MinimumColumnsCountToReconstruct()
+	minimumCount := peerdas.MinimumColumnCountToReconstruct()
 
 	t.Run("not enough stored sidecars", func(t *testing.T) {
 		storage := filesystem.NewEphemeralDataColumnStorage(t)
@@ -61,7 +61,7 @@ func TestReconstructDataColumns(t *testing.T) {
 		const cgc = 8
 
 		storage := filesystem.NewEphemeralDataColumnStorage(t)
-		minimumCount := peerdas.MinimumColumnsCountToReconstruct()
+		minimumCount := peerdas.MinimumColumnCountToReconstruct()
 		err := storage.Save(verifiedRoDataColumns[:minimumCount])
 		require.NoError(t, err)
 

beacon-chain/sync/initial-sync/BUILD.bazel

@@ -20,6 +20,7 @@ go_library(
         "//beacon-chain/blockchain:go_default_library",
         "//beacon-chain/core/feed/block:go_default_library",
         "//beacon-chain/core/feed/state:go_default_library",
+        "//beacon-chain/core/peerdas:go_default_library",
         "//beacon-chain/core/transition:go_default_library",
         "//beacon-chain/das:go_default_library",
         "//beacon-chain/db:go_default_library",
@@ -33,6 +34,7 @@ go_library(
         "//beacon-chain/verification:go_default_library",
         "//cmd/beacon-chain/flags:go_default_library",
         "//config/features:go_default_library",
+        "//config/fieldparams:go_default_library",
         "//config/params:go_default_library",
         "//consensus-types/blocks:go_default_library",
         "//consensus-types/interfaces:go_default_library",
@@ -72,7 +74,9 @@ go_test(
     deps = [
         "//async/abool:go_default_library",
         "//beacon-chain/blockchain:go_default_library",
+        "//beacon-chain/blockchain/kzg:go_default_library",
         "//beacon-chain/blockchain/testing:go_default_library",
+        "//beacon-chain/core/peerdas:go_default_library",
         "//beacon-chain/das:go_default_library",
         "//beacon-chain/db:go_default_library",
         "//beacon-chain/db/filesystem:go_default_library",
@@ -89,6 +93,7 @@ go_test(
         "//beacon-chain/verification:go_default_library",
         "//cmd/beacon-chain/flags:go_default_library",
         "//config/features:go_default_library",
+        "//config/fieldparams:go_default_library",
         "//config/params:go_default_library",
         "//consensus-types/blocks:go_default_library",
         "//consensus-types/interfaces:go_default_library",
@@ -104,7 +109,9 @@ go_test(
         "//time:go_default_library",
         "//time/slots:go_default_library",
         "@com_github_ethereum_go_ethereum//p2p/enr:go_default_library",
+        "@com_github_libp2p_go_libp2p//:go_default_library",
         "@com_github_libp2p_go_libp2p//core:go_default_library",
+        "@com_github_libp2p_go_libp2p//core/crypto:go_default_library",
         "@com_github_libp2p_go_libp2p//core/network:go_default_library",
         "@com_github_libp2p_go_libp2p//core/peer:go_default_library",
         "@com_github_paulbellamy_ratecounter//:go_default_library",

beacon-chain/sync/initial-sync/blocks_fetcher.go

@@ -3,11 +3,13 @@ package initialsync
 import (
 	"context"
 	"fmt"
+	"slices"
 	"sort"
 	"strings"
 	"sync"
 	"time"
 
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/peerdas"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/db"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/filesystem"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p"
@@ -15,6 +17,7 @@ import (
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/startup"
 	prysmsync "github.com/OffchainLabs/prysm/v6/beacon-chain/sync"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/sync/verify"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/verification"
 	"github.com/OffchainLabs/prysm/v6/cmd/beacon-chain/flags"
 	"github.com/OffchainLabs/prysm/v6/config/features"
 	"github.com/OffchainLabs/prysm/v6/config/params"
@@ -34,7 +37,6 @@ import (
 )
 
 const (
-
 	// maxPendingRequests limits how many concurrent fetch request one can initiate.
 	maxPendingRequests = 64
 	// peersPercentagePerRequest caps percentage of peers to be used in a request.
@@ -78,6 +80,8 @@ type blocksFetcherConfig struct {
 	peerFilterCapacityWeight float64
 	mode                     syncMode
 	bs                       filesystem.BlobStorageSummarizer
+	dcs                      filesystem.DataColumnStorageReader
+	cv                       verification.NewDataColumnsVerifier
 }
 
 // blocksFetcher is a service to fetch chain data from peers.
@@ -94,6 +98,8 @@ type blocksFetcher struct {
 	p2p             p2p.P2P
 	db              db.ReadOnlyDatabase
 	bs              filesystem.BlobStorageSummarizer
+	dcs             filesystem.DataColumnStorageReader
+	cv              verification.NewDataColumnsVerifier
 	blocksPerPeriod uint64
 	rateLimiter     *leakybucket.Collector
 	peerLocks       map[peer.ID]*peerLock
@@ -124,7 +130,7 @@ type fetchRequestResponse struct {
 	blobsFrom  peer.ID
 	start      primitives.Slot
 	count      uint64
-	bwb        []blocks.BlockWithROBlobs
+	bwb        []blocks.BlockWithROSidecars
 	err        error
 }
 
@@ -162,6 +168,8 @@ func newBlocksFetcher(ctx context.Context, cfg *blocksFetcherConfig) *blocksFetc
 		p2p:             cfg.p2p,
 		db:              cfg.db,
 		bs:              cfg.bs,
+		dcs:             cfg.dcs,
+		cv:              cfg.cv,
 		blocksPerPeriod: uint64(blocksPerPeriod),
 		rateLimiter:     rateLimiter,
 		peerLocks:       make(map[peer.ID]*peerLock),
@@ -298,7 +306,7 @@ func (f *blocksFetcher) handleRequest(ctx context.Context, start primitives.Slot
 	response := &fetchRequestResponse{
 		start: start,
 		count: count,
-		bwb:   []blocks.BlockWithROBlobs{},
+		bwb:   []blocks.BlockWithROSidecars{},
 		err:   nil,
 	}
 
@@ -317,30 +325,114 @@ func (f *blocksFetcher) handleRequest(ctx context.Context, start primitives.Slot
 	if f.mode == modeStopOnFinalizedEpoch {
 		highestFinalizedSlot := params.BeaconConfig().SlotsPerEpoch.Mul(uint64(targetEpoch + 1))
 		if start > highestFinalizedSlot {
-			response.err = fmt.Errorf("%w, slot: %d, highest finalized slot: %d",
-				errSlotIsTooHigh, start, highestFinalizedSlot)
+			response.err = fmt.Errorf(
+				"%w, slot: %d, highest finalized slot: %d",
+				errSlotIsTooHigh, start, highestFinalizedSlot,
+			)
+
 			return response
 		}
 	}
 
 	response.bwb, response.blocksFrom, response.err = f.fetchBlocksFromPeer(ctx, start, count, peers)
 	if response.err == nil {
-		pid, bwb, err := f.fetchBlobsFromPeer(ctx, response.bwb, response.blocksFrom, peers)
+		pid, err := f.fetchSidecars(ctx, response.blocksFrom, peers, response.bwb)
 		if err != nil {
+			log.WithError(err).Error("Failed to fetch sidecars")
 			response.err = err
 		}
-		response.bwb = bwb
+
 		response.blobsFrom = pid
 	}
+
 	return response
 }
 
-// fetchBlocksFromPeer fetches blocks from a single randomly selected peer.
+// fetchSidecars fetches sidecars corresponding to blocks in `response.bwb`.
+// It mutates `Blobs` and `Columns` fields of `response.bwb` with fetched sidecars.
+// `pid` is the initial peer to request blob from (usually the peer from which the block originated),
+// `peers` is a list of peers to use for the request blobs if `pid` fails.
+// `bwScs` must me sorted by slot.
+// It returns the peer ID from which blobs were fetched (if any).
+func (f *blocksFetcher) fetchSidecars(ctx context.Context, pid peer.ID, peers []peer.ID, bwScs []blocks.BlockWithROSidecars) (peer.ID, error) {
+	samplesPerSlot := params.BeaconConfig().SamplesPerSlot
+
+	if len(bwScs) == 0 {
+		return "", nil
+	}
+
+	firstFuluIndex, err := findFirstFuluIndex(bwScs)
+	if err != nil {
+		return "", errors.Wrap(err, "find first Fulu index")
+	}
+
+	preFulu := bwScs[:firstFuluIndex]
+	postFulu := bwScs[firstFuluIndex:]
+
+	var blobsPid peer.ID
+
+	if len(preFulu) > 0 {
+		// Fetch blob sidecars.
+		blobsPid, err = f.fetchBlobsFromPeer(ctx, preFulu, pid, peers)
+		if err != nil {
+			return "", errors.Wrap(err, "fetch blobs from peer")
+		}
+	}
+
+	if len(postFulu) == 0 {
+		return blobsPid, nil
+	}
+
+	// Compute the columns to request.
+	custodyGroupCount, err := f.p2p.CustodyGroupCount()
+	if err != nil {
+		return blobsPid, errors.Wrap(err, "custody group count")
+	}
+
+	samplingSize := max(custodyGroupCount, samplesPerSlot)
+	info, _, err := peerdas.Info(f.p2p.NodeID(), samplingSize)
+	if err != nil {
+		return blobsPid, errors.Wrap(err, "custody info")
+	}
+
+	params := prysmsync.DataColumnSidecarsParams{
+		Ctx:         ctx,
+		Tor:         f.clock,
+		P2P:         f.p2p,
+		RateLimiter: f.rateLimiter,
+		CtxMap:      f.ctxMap,
+		Storage:     f.dcs,
+		NewVerifier: f.cv,
+	}
+
+	roBlocks := make([]blocks.ROBlock, 0, len(postFulu))
+	for _, block := range postFulu {
+		roBlocks = append(roBlocks, block.Block)
+	}
+
+	verifiedRoDataColumnsByRoot, err := prysmsync.FetchDataColumnSidecars(params, roBlocks, info.CustodyColumns)
+	if err != nil {
+		return "", errors.Wrap(err, "fetch data column sidecars")
+	}
+
+	// Populate the response.
+	for i := range bwScs {
+		bwSc := &bwScs[i]
+		root := bwSc.Block.Root()
+		if columns, ok := verifiedRoDataColumnsByRoot[root]; ok {
+			bwSc.Columns = columns
+		}
+	}
+
+	return blobsPid, nil
+}
+
+// fetchBlocksFromPeer fetches blocks from a single randomly selected peer, sorted by slot.
 func (f *blocksFetcher) fetchBlocksFromPeer(
 	ctx context.Context,
 	start primitives.Slot, count uint64,
 	peers []peer.ID,
-) ([]blocks.BlockWithROBlobs, peer.ID, error) {
+) ([]blocks.BlockWithROSidecars, peer.ID, error) {
 	ctx, span := trace.StartSpan(ctx, "initialsync.fetchBlocksFromPeer")
 	defer span.End()
 
@@ -355,8 +447,7 @@ func (f *blocksFetcher) fetchBlocksFromPeer(
 	// peers are dialed first.
 	peers = append(bestPeers, peers...)
 	peers = dedupPeers(peers)
-	for i := 0; i < len(peers); i++ {
-		p := peers[i]
+	for _, p := range peers {
 		blocks, err := f.requestBlocks(ctx, req, p)
 		if err != nil {
 			log.WithField("peer", p).WithError(err).Debug("Could not request blocks by range from peer")
@@ -380,14 +471,14 @@ func (f *blocksFetcher) fetchBlocksFromPeer(
 	return nil, "", errNoPeersAvailable
 }
 
-func sortedBlockWithVerifiedBlobSlice(bs []interfaces.ReadOnlySignedBeaconBlock) ([]blocks.BlockWithROBlobs, error) {
-	rb := make([]blocks.BlockWithROBlobs, len(bs))
-	for i, b := range bs {
+func sortedBlockWithVerifiedBlobSlice(blks []interfaces.ReadOnlySignedBeaconBlock) ([]blocks.BlockWithROSidecars, error) {
+	rb := make([]blocks.BlockWithROSidecars, len(blks))
+	for i, b := range blks {
 		ro, err := blocks.NewROBlock(b)
 		if err != nil {
 			return nil, err
 		}
-		rb[i] = blocks.BlockWithROBlobs{Block: ro}
+		rb[i] = blocks.BlockWithROSidecars{Block: ro}
 	}
 	sort.Sort(blocks.BlockWithROBlobsSlice(rb))
 	return rb, nil
@@ -403,7 +494,8 @@ type commitmentCountList []commitmentCount
 
 // countCommitments makes a list of all blocks that have commitments that need to be satisfied.
 // This gives us a representation to finish building the request that is lightweight and readable for testing.
-func countCommitments(bwb []blocks.BlockWithROBlobs, retentionStart primitives.Slot) commitmentCountList {
+// `bwb` must be sorted by slot.
+func countCommitments(bwb []blocks.BlockWithROSidecars, retentionStart primitives.Slot) commitmentCountList {
 	if len(bwb) == 0 {
 		return nil
 	}
@@ -485,7 +577,9 @@ func (r *blobRange) Request() *p2ppb.BlobSidecarsByRangeRequest {
 var errBlobVerification = errors.New("peer unable to serve aligned BlobSidecarsByRange and BeaconBlockSidecarsByRange responses")
 var errMissingBlobsForBlockCommitments = errors.Wrap(errBlobVerification, "blobs unavailable for processing block with kzg commitments")
 
-func verifyAndPopulateBlobs(bwb []blocks.BlockWithROBlobs, blobs []blocks.ROBlob, req *p2ppb.BlobSidecarsByRangeRequest, bss filesystem.BlobStorageSummarizer) ([]blocks.BlockWithROBlobs, error) {
+// verifyAndPopulateBlobs mutate the input `bwb` argument by adding verified blobs.
+// This function mutates the input `bwb` argument.
+func verifyAndPopulateBlobs(bwb []blocks.BlockWithROSidecars, blobs []blocks.ROBlob, req *p2ppb.BlobSidecarsByRangeRequest, bss filesystem.BlobStorageSummarizer) error {
 	blobsByRoot := make(map[[32]byte][]blocks.ROBlob)
 	for i := range blobs {
 		if blobs[i].Slot() < req.StartSlot {
@@ -495,46 +589,53 @@ func verifyAndPopulateBlobs(bwb []blocks.BlockWithROBlobs, blobs []blocks.ROBlob
 		blobsByRoot[br] = append(blobsByRoot[br], blobs[i])
 	}
 	for i := range bwb {
-		bwi, err := populateBlock(bwb[i], blobsByRoot[bwb[i].Block.Root()], req, bss)
+		err := populateBlock(&bwb[i], blobsByRoot[bwb[i].Block.Root()], req, bss)
 		if err != nil {
 			if errors.Is(err, errDidntPopulate) {
 				continue
 			}
-			return bwb, err
+			return err
 		}
-		bwb[i] = bwi
 	}
-	return bwb, nil
+	return nil
 }
 
 var errDidntPopulate = errors.New("skipping population of block")
 
-func populateBlock(bw blocks.BlockWithROBlobs, blobs []blocks.ROBlob, req *p2ppb.BlobSidecarsByRangeRequest, bss filesystem.BlobStorageSummarizer) (blocks.BlockWithROBlobs, error) {
+// populateBlock verifies and populates blobs for a block.
+// This function mutates the input `bw` argument.
+func populateBlock(bw *blocks.BlockWithROSidecars, blobs []blocks.ROBlob, req *p2ppb.BlobSidecarsByRangeRequest, bss filesystem.BlobStorageSummarizer) error {
 	blk := bw.Block
 	if blk.Version() < version.Deneb || blk.Block().Slot() < req.StartSlot {
-		return bw, errDidntPopulate
+		return errDidntPopulate
 	}
+
 	commits, err := blk.Block().Body().BlobKzgCommitments()
 	if err != nil {
-		return bw, errDidntPopulate
+		return errDidntPopulate
 	}
+
 	if len(commits) == 0 {
-		return bw, errDidntPopulate
+		return errDidntPopulate
 	}
+
 	// Drop blobs on the floor if we already have them.
 	if bss != nil && bss.Summary(blk.Root()).AllAvailable(len(commits)) {
-		return bw, errDidntPopulate
+		return errDidntPopulate
 	}
+
 	if len(commits) != len(blobs) {
-		return bw, missingCommitError(blk.Root(), blk.Block().Slot(), commits)
+		return missingCommitError(blk.Root(), blk.Block().Slot(), commits)
 	}
+
 	for ci := range commits {
 		if err := verify.BlobAlignsWithBlock(blobs[ci], blk); err != nil {
-			return bw, err
+			return err
 		}
 	}
+
 	bw.Blobs = blobs
-	return bw, nil
+	return nil
 }
 
 func missingCommitError(root [32]byte, slot primitives.Slot, missing [][]byte) error {
@@ -547,29 +648,38 @@ func missingCommitError(root [32]byte, slot primitives.Slot, missing [][]byte) e
 }
 
 // fetchBlobsFromPeer fetches blocks from a single randomly selected peer.
-func (f *blocksFetcher) fetchBlobsFromPeer(ctx context.Context, bwb []blocks.BlockWithROBlobs, pid peer.ID, peers []peer.ID) (peer.ID, []blocks.BlockWithROBlobs, error) {
+// This function mutates the input `bwb` argument.
+// `pid` is the initial peer to request blobs from (usually the peer from which the block originated),
+// `peers` is a list of peers to use for the request if `pid` fails.
+// `bwb` must be sorted by slot.
+// It returns the peer ID from which blobs were fetched.
+func (f *blocksFetcher) fetchBlobsFromPeer(ctx context.Context, bwb []blocks.BlockWithROSidecars, pid peer.ID, peers []peer.ID) (peer.ID, error) {
+	if len(bwb) == 0 {
+		return "", nil
+	}
+
 	ctx, span := trace.StartSpan(ctx, "initialsync.fetchBlobsFromPeer")
 	defer span.End()
 	if slots.ToEpoch(f.clock.CurrentSlot()) < params.BeaconConfig().DenebForkEpoch {
-		return "", bwb, nil
+		return "", nil
 	}
 	blobWindowStart, err := prysmsync.BlobRPCMinValidSlot(f.clock.CurrentSlot())
 	if err != nil {
-		return "", nil, err
+		return "", err
 	}
 	// Construct request message based on observed interval of blocks in need of blobs.
 	req := countCommitments(bwb, blobWindowStart).blobRange(f.bs).Request()
 	if req == nil {
-		return "", bwb, nil
+		return "", nil
 	}
 	peers = f.filterPeers(ctx, peers, peersPercentagePerRequest)
 	// We dial the initial peer first to ensure that we get the desired set of blobs.
-	wantedPeers := append([]peer.ID{pid}, peers...)
-	bestPeers := f.hasSufficientBandwidth(wantedPeers, req.Count)
+	peers = append([]peer.ID{pid}, peers...)
+	peers = f.hasSufficientBandwidth(peers, req.Count)
 	// We append the best peers to the front so that higher capacity
 	// peers are dialed first. If all of them fail, we fallback to the
 	// initial peer we wanted to request blobs from.
-	peers = append(bestPeers, pid)
+	peers = append(peers, pid)
 	for i := 0; i < len(peers); i++ {
 		p := peers[i]
 		blobs, err := f.requestBlobs(ctx, req, p)
@@ -578,14 +688,24 @@ func (f *blocksFetcher) fetchBlobsFromPeer(ctx context.Context, bwb []blocks.Blo
 			continue
 		}
 		f.p2p.Peers().Scorers().BlockProviderScorer().Touch(p)
-		robs, err := verifyAndPopulateBlobs(bwb, blobs, req, f.bs)
-		if err != nil {
+		if err := verifyAndPopulateBlobs(bwb, blobs, req, f.bs); err != nil {
 			log.WithField("peer", p).WithError(err).Debug("Invalid BeaconBlobsByRange response")
 			continue
 		}
-		return p, robs, err
+		return p, err
 	}
-	return "", nil, errNoPeersAvailable
+	return "", errNoPeersAvailable
+}
+
+// sortedSliceFromMap returns a sorted slice of keys from a map.
+func sortedSliceFromMap(m map[uint64]bool) []uint64 {
+	result := make([]uint64, 0, len(m))
+	for k := range m {
+		result = append(result, k)
+	}
+
+	slices.Sort(result)
+	return result
 }
 
 // requestBlocks is a wrapper for handling BeaconBlocksByRangeRequest requests/streams.
@@ -642,6 +762,7 @@ func (f *blocksFetcher) requestBlobs(ctx context.Context, req *p2ppb.BlobSidecar
 	}
 	f.rateLimiter.Add(pid.String(), int64(req.Count))
 	l.Unlock()
+
 	return prysmsync.SendBlobsByRangeRequest(ctx, f.clock, f.p2p, pid, f.ctxMap, req)
 }
 
@@ -699,13 +820,17 @@ func (f *blocksFetcher) waitForBandwidth(pid peer.ID, count uint64) error {
 }
 
 func (f *blocksFetcher) hasSufficientBandwidth(peers []peer.ID, count uint64) []peer.ID {
-	filteredPeers := []peer.ID{}
-	for _, p := range peers {
-		if uint64(f.rateLimiter.Remaining(p.String())) < count {
+	filteredPeers := make([]peer.ID, 0, len(peers))
+
+	for _, peer := range peers {
+		remaining := uint64(0)
+		if remainingInt := f.rateLimiter.Remaining(peer.String()); remainingInt > 0 {
+			remaining = uint64(remainingInt)
+		}
+		if remaining < count {
 			continue
 		}
-		copiedP := p
-		filteredPeers = append(filteredPeers, copiedP)
+		filteredPeers = append(filteredPeers, peer)
 	}
 	return filteredPeers
 }
@@ -745,3 +870,23 @@ func dedupPeers(peers []peer.ID) []peer.ID {
 	}
 	return newPeerList
 }
+
+// findFirstFuluIndex returns the index of the first block with a version >= Fulu.
+// It returns an error if blocks are not correctly sorted by version regarding Fulu.
+func findFirstFuluIndex(bwScs []blocks.BlockWithROSidecars) (int, error) {
+	firstFuluIndex := len(bwScs)
+
+	for i, bwSc := range bwScs {
+		blockVersion := bwSc.Block.Version()
+		if blockVersion >= version.Fulu && firstFuluIndex > i {
+			firstFuluIndex = i
+			continue
+		}
+
+		if blockVersion < version.Fulu && firstFuluIndex <= i {
+			return 0, errors.New("blocks are not sorted by version")
+		}
+	}
+
+	return firstFuluIndex, nil
+}

beacon-chain/sync/initial-sync/blocks_fetcher_test.go

@@ -12,11 +12,12 @@ import (
 	mock "github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain/testing"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/filesystem"
 	dbtest "github.com/OffchainLabs/prysm/v6/beacon-chain/db/testing"
-	p2pm "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p"
-	p2pt "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/testing"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/p2p"
+	p2ptest "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/testing"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/startup"
 	beaconsync "github.com/OffchainLabs/prysm/v6/beacon-chain/sync"
 	"github.com/OffchainLabs/prysm/v6/cmd/beacon-chain/flags"
+	fieldparams "github.com/OffchainLabs/prysm/v6/config/fieldparams"
 	"github.com/OffchainLabs/prysm/v6/config/params"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/interfaces"
@@ -266,7 +267,7 @@ func TestBlocksFetcher_RoundRobin(t *testing.T) {
 
 			beaconDB := dbtest.SetupDB(t)
 
-			p := p2pt.NewTestP2P(t)
+			p := p2ptest.NewTestP2P(t)
 			connectPeers(t, p, tt.peers, p.Peers())
 			cache.RLock()
 			genesisRoot := cache.rootCache[0]
@@ -307,9 +308,9 @@ func TestBlocksFetcher_RoundRobin(t *testing.T) {
 				fetcher.stop()
 			}()
 
-			processFetchedBlocks := func() ([]blocks.BlockWithROBlobs, error) {
+			processFetchedBlocks := func() ([]blocks.BlockWithROSidecars, error) {
 				defer cancel()
-				var unionRespBlocks []blocks.BlockWithROBlobs
+				var unionRespBlocks []blocks.BlockWithROSidecars
 
 				for {
 					select {
@@ -398,6 +399,7 @@ func TestBlocksFetcher_scheduleRequest(t *testing.T) {
 			fetcher.scheduleRequest(t.Context(), 1, blockBatchLimit))
 	})
 }
+
 func TestBlocksFetcher_handleRequest(t *testing.T) {
 	blockBatchLimit := flags.Get().BlockBatchLimit
 	chainConfig := struct {
@@ -455,7 +457,7 @@ func TestBlocksFetcher_handleRequest(t *testing.T) {
 			}
 		}()
 
-		var bwb []blocks.BlockWithROBlobs
+		var bwb []blocks.BlockWithROSidecars
 		select {
 		case <-ctx.Done():
 			t.Error(ctx.Err())
@@ -531,9 +533,9 @@ func TestBlocksFetcher_requestBeaconBlocksByRange(t *testing.T) {
 }
 
 func TestBlocksFetcher_RequestBlocksRateLimitingLocks(t *testing.T) {
-	p1 := p2pt.NewTestP2P(t)
-	p2 := p2pt.NewTestP2P(t)
-	p3 := p2pt.NewTestP2P(t)
+	p1 := p2ptest.NewTestP2P(t)
+	p2 := p2ptest.NewTestP2P(t)
+	p3 := p2ptest.NewTestP2P(t)
 	p1.Connect(p2)
 	p1.Connect(p3)
 	require.Equal(t, 2, len(p1.BHost.Network().Peers()), "Expected peers to be connected")
@@ -543,7 +545,7 @@ func TestBlocksFetcher_RequestBlocksRateLimitingLocks(t *testing.T) {
 		Count:     64,
 	}
 
-	topic := p2pm.RPCBlocksByRangeTopicV1
+	topic := p2p.RPCBlocksByRangeTopicV1
 	protocol := libp2pcore.ProtocolID(topic + p2.Encoding().ProtocolSuffix())
 	streamHandlerFn := func(stream network.Stream) {
 		assert.NoError(t, stream.Close())
@@ -602,15 +604,15 @@ func TestBlocksFetcher_RequestBlocksRateLimitingLocks(t *testing.T) {
 }
 
 func TestBlocksFetcher_WaitForBandwidth(t *testing.T) {
-	p1 := p2pt.NewTestP2P(t)
-	p2 := p2pt.NewTestP2P(t)
+	p1 := p2ptest.NewTestP2P(t)
+	p2 := p2ptest.NewTestP2P(t)
 	p1.Connect(p2)
 	require.Equal(t, 1, len(p1.BHost.Network().Peers()), "Expected peers to be connected")
 	req := &ethpb.BeaconBlocksByRangeRequest{
 		Count: 64,
 	}
 
-	topic := p2pm.RPCBlocksByRangeTopicV1
+	topic := p2p.RPCBlocksByRangeTopicV1
 	protocol := libp2pcore.ProtocolID(topic + p2.Encoding().ProtocolSuffix())
 	streamHandlerFn := func(stream network.Stream) {
 		assert.NoError(t, stream.Close())
@@ -638,7 +640,7 @@ func TestBlocksFetcher_WaitForBandwidth(t *testing.T) {
 }
 
 func TestBlocksFetcher_requestBlocksFromPeerReturningInvalidBlocks(t *testing.T) {
-	p1 := p2pt.NewTestP2P(t)
+	p1 := p2ptest.NewTestP2P(t)
 	tests := []struct {
 		name         string
 		req          *ethpb.BeaconBlocksByRangeRequest
@@ -883,7 +885,7 @@ func TestBlocksFetcher_requestBlocksFromPeerReturningInvalidBlocks(t *testing.T)
 		},
 	}
 
-	topic := p2pm.RPCBlocksByRangeTopicV1
+	topic := p2p.RPCBlocksByRangeTopicV1
 	protocol := libp2pcore.ProtocolID(topic + p1.Encoding().ProtocolSuffix())
 
 	ctx, cancel := context.WithCancel(t.Context())
@@ -893,7 +895,7 @@ func TestBlocksFetcher_requestBlocksFromPeerReturningInvalidBlocks(t *testing.T)
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			p2 := p2pt.NewTestP2P(t)
+			p2 := p2ptest.NewTestP2P(t)
 			p1.Connect(p2)
 
 			p2.BHost.SetStreamHandler(protocol, tt.handlerGenFn(tt.req))
@@ -993,7 +995,7 @@ func TestBlobRangeForBlocks(t *testing.T) {
 func TestBlobRequest(t *testing.T) {
 	var nilReq *ethpb.BlobSidecarsByRangeRequest
 	// no blocks
-	req := countCommitments([]blocks.BlockWithROBlobs{}, 0).blobRange(nil).Request()
+	req := countCommitments([]blocks.BlockWithROSidecars{}, 0).blobRange(nil).Request()
 	require.Equal(t, nilReq, req)
 	blks, _ := util.ExtendBlocksPlusBlobs(t, []blocks.ROBlock{}, 10)
 	sbbs := make([]interfaces.ReadOnlySignedBeaconBlock, len(blks))
@@ -1026,22 +1028,16 @@ func TestBlobRequest(t *testing.T) {
 }
 
 func TestCountCommitments(t *testing.T) {
-	// no blocks
-	// blocks before retention start filtered
-	// blocks without commitments filtered
-	// pre-deneb filtered
-	// variety of commitment counts are accurate, from 1 to max
 	type testcase struct {
-		name      string
-		bwb       func(t *testing.T, c testcase) []blocks.BlockWithROBlobs
-		numBlocks int
-		retStart  primitives.Slot
-		resCount  int
+		name     string
+		bwb      func(t *testing.T, c testcase) []blocks.BlockWithROSidecars
+		retStart primitives.Slot
+		resCount int
 	}
 	cases := []testcase{
 		{
 			name: "nil blocks is safe",
-			bwb: func(t *testing.T, c testcase) []blocks.BlockWithROBlobs {
+			bwb: func(t *testing.T, c testcase) []blocks.BlockWithROSidecars {
 				return nil
 			},
 			retStart: 0,
@@ -1179,7 +1175,7 @@ func TestCommitmentCountList(t *testing.T) {
 	}
 }
 
-func testSequenceBlockWithBlob(t *testing.T, nblocks int) ([]blocks.BlockWithROBlobs, []blocks.ROBlob) {
+func testSequenceBlockWithBlob(t *testing.T, nblocks int) ([]blocks.BlockWithROSidecars, []blocks.ROBlob) {
 	blks, blobs := util.ExtendBlocksPlusBlobs(t, []blocks.ROBlock{}, nblocks)
 	sbbs := make([]interfaces.ReadOnlySignedBeaconBlock, len(blks))
 	for i := range blks {
@@ -1190,7 +1186,7 @@ func testSequenceBlockWithBlob(t *testing.T, nblocks int) ([]blocks.BlockWithROB
 	return bwb, blobs
 }
 
-func testReqFromResp(bwb []blocks.BlockWithROBlobs) *ethpb.BlobSidecarsByRangeRequest {
+func testReqFromResp(bwb []blocks.BlockWithROSidecars) *ethpb.BlobSidecarsByRangeRequest {
 	return &ethpb.BlobSidecarsByRangeRequest{
 		StartSlot: bwb[0].Block.Block().Slot(),
 		Count:     uint64(bwb[len(bwb)-1].Block.Block().Slot()-bwb[0].Block.Block().Slot()) + 1,
@@ -1207,7 +1203,7 @@ func TestVerifyAndPopulateBlobs(t *testing.T) {
 		}
 		require.Equal(t, len(blobs), len(expectedCommits))
 
-		bwb, err := verifyAndPopulateBlobs(bwb, blobs, testReqFromResp(bwb), nil)
+		err := verifyAndPopulateBlobs(bwb, blobs, testReqFromResp(bwb), nil)
 		require.NoError(t, err)
 		for _, bw := range bwb {
 			commits, err := bw.Block.Block().Body().BlobKzgCommitments()
@@ -1228,7 +1224,7 @@ func TestVerifyAndPopulateBlobs(t *testing.T) {
 	})
 	t.Run("missing blobs", func(t *testing.T) {
 		bwb, blobs := testSequenceBlockWithBlob(t, 10)
-		_, err := verifyAndPopulateBlobs(bwb, blobs[1:], testReqFromResp(bwb), nil)
+		err := verifyAndPopulateBlobs(bwb, blobs[1:], testReqFromResp(bwb), nil)
 		require.ErrorIs(t, err, errMissingBlobsForBlockCommitments)
 	})
 	t.Run("no blobs for last block", func(t *testing.T) {
@@ -1240,7 +1236,7 @@ func TestVerifyAndPopulateBlobs(t *testing.T) {
 		blobs = blobs[0 : len(blobs)-len(cmts)]
 		lastBlk, _ = util.GenerateTestDenebBlockWithSidecar(t, lastBlk.Block().ParentRoot(), lastBlk.Block().Slot(), 0)
 		bwb[lastIdx].Block = lastBlk
-		_, err = verifyAndPopulateBlobs(bwb, blobs, testReqFromResp(bwb), nil)
+		err = verifyAndPopulateBlobs(bwb, blobs, testReqFromResp(bwb), nil)
 		require.NoError(t, err)
 	})
 	t.Run("blobs not copied if all locally available", func(t *testing.T) {
@@ -1254,7 +1250,7 @@ func TestVerifyAndPopulateBlobs(t *testing.T) {
 			r7: {0, 1, 2, 3, 4, 5},
 		}
 		bss := filesystem.NewMockBlobStorageSummarizer(t, onDisk)
-		bwb, err := verifyAndPopulateBlobs(bwb, blobs, testReqFromResp(bwb), bss)
+		err := verifyAndPopulateBlobs(bwb, blobs, testReqFromResp(bwb), bss)
 		require.NoError(t, err)
 		require.Equal(t, 6, len(bwb[i1].Blobs))
 		require.Equal(t, 0, len(bwb[i7].Blobs))
@@ -1302,3 +1298,203 @@ func TestBlockFetcher_HasSufficientBandwidth(t *testing.T) {
 	}
 	assert.Equal(t, 2, len(receivedPeers))
 }
+
+func TestSortedSliceFromMap(t *testing.T) {
+	m := map[uint64]bool{1: true, 3: true, 2: true, 4: true}
+	expected := []uint64{1, 2, 3, 4}
+
+	actual := sortedSliceFromMap(m)
+	require.DeepSSZEqual(t, expected, actual)
+}
+
+func TestFetchSidecars(t *testing.T) {
+	ctx := t.Context()
+	t.Run("No blocks", func(t *testing.T) {
+		fetcher := new(blocksFetcher)
+
+		pid, err := fetcher.fetchSidecars(ctx, "", nil, []blocks.BlockWithROSidecars{})
+		assert.NoError(t, err)
+		assert.Equal(t, peer.ID(""), pid)
+	})
+
+	t.Run("Nominal", func(t *testing.T) {
+		beaconConfig := params.BeaconConfig()
+		numberOfColumns := beaconConfig.NumberOfColumns
+		samplesPerSlot := beaconConfig.SamplesPerSlot
+
+		// Define "now" to be one epoch after genesis time + retention period.
+		genesisTime := time.Date(2025, time.August, 10, 0, 0, 0, 0, time.UTC)
+		secondsPerSlot := beaconConfig.SecondsPerSlot
+		slotsPerEpoch := beaconConfig.SlotsPerEpoch
+		secondsPerEpoch := uint64(slotsPerEpoch.Mul(secondsPerSlot))
+		retentionEpochs := beaconConfig.MinEpochsForDataColumnSidecarsRequest
+		nowWrtGenesisSecs := retentionEpochs.Add(1).Mul(secondsPerEpoch)
+		now := genesisTime.Add(time.Duration(nowWrtGenesisSecs) * time.Second)
+
+		genesisValidatorRoot := [fieldparams.RootLength]byte{}
+		nower := func() time.Time { return now }
+		clock := startup.NewClock(genesisTime, genesisValidatorRoot, startup.WithNower(nower))
+
+		// Define a Deneb block with blobs out of retention period.
+		denebBlock := util.NewBeaconBlockDeneb()
+		denebBlock.Block.Slot = 0 // Genesis slot, out of retention period.
+		signedDenebBlock, err := blocks.NewSignedBeaconBlock(denebBlock)
+		require.NoError(t, err)
+		roDebebBlock, err := blocks.NewROBlock(signedDenebBlock)
+		require.NoError(t, err)
+
+		// Define a Fulu block with blobs in the retention period.
+		fuluBlock := util.NewBeaconBlockFulu()
+		fuluBlock.Block.Slot = slotsPerEpoch                                                            // Within retention period.
+		fuluBlock.Block.Body.BlobKzgCommitments = [][]byte{make([]byte, fieldparams.KzgCommitmentSize)} // Dummy commitment.
+		signedFuluBlock, err := blocks.NewSignedBeaconBlock(fuluBlock)
+		require.NoError(t, err)
+		roFuluBlock, err := blocks.NewROBlock(signedFuluBlock)
+		require.NoError(t, err)
+
+		bodyRoot, err := fuluBlock.Block.Body.HashTreeRoot()
+		require.NoError(t, err)
+
+		// Create and save data column sidecars for this fulu block in the database.
+		params := make([]util.DataColumnParam, 0, numberOfColumns)
+		for i := range numberOfColumns {
+			param := util.DataColumnParam{Index: i, Slot: slotsPerEpoch, BodyRoot: bodyRoot[:]}
+			params = append(params, param)
+		}
+		_, verifiedRoDataColumnSidecars := util.CreateTestVerifiedRoDataColumnSidecars(t, params)
+
+		// Create a data columns storage.
+		dir := t.TempDir()
+		dataColumnStorage, err := filesystem.NewDataColumnStorage(ctx, filesystem.WithDataColumnBasePath(dir))
+		require.NoError(t, err)
+
+		// Save the data column sidecars to the storage.
+		err = dataColumnStorage.Save(verifiedRoDataColumnSidecars)
+		require.NoError(t, err)
+
+		// Create a blocks fetcher.
+		fetcher := &blocksFetcher{
+			clock: clock,
+			p2p:   p2ptest.NewTestP2P(t),
+			dcs:   dataColumnStorage,
+		}
+
+		// Fetch sidecars.
+		blocksWithSidecars := []blocks.BlockWithROSidecars{
+			{Block: roDebebBlock},
+			{Block: roFuluBlock},
+		}
+		pid, err := fetcher.fetchSidecars(ctx, "", nil, blocksWithSidecars)
+		require.NoError(t, err)
+		require.Equal(t, peer.ID(""), pid)
+
+		// Verify that block with sidecars were modified correctly.
+		require.Equal(t, 0, len(blocksWithSidecars[0].Blobs))
+		require.Equal(t, 0, len(blocksWithSidecars[0].Columns))
+		require.Equal(t, 0, len(blocksWithSidecars[1].Blobs))
+
+		// We don't check the content of the columns here. The extensive test is done
+		// in TestFetchDataColumnsSidecars.
+		require.Equal(t, samplesPerSlot, uint64(len(blocksWithSidecars[1].Columns)))
+	})
+}
+func TestFirstFuluIndex(t *testing.T) {
+	bellatrix := util.NewBeaconBlockBellatrix()
+	signedBellatrix, err := blocks.NewSignedBeaconBlock(bellatrix)
+	require.NoError(t, err)
+	roBellatrix, err := blocks.NewROBlock(signedBellatrix)
+	require.NoError(t, err)
+
+	capella := util.NewBeaconBlockCapella()
+	signedCapella, err := blocks.NewSignedBeaconBlock(capella)
+	require.NoError(t, err)
+	roCapella, err := blocks.NewROBlock(signedCapella)
+	require.NoError(t, err)
+
+	deneb := util.NewBeaconBlockDeneb()
+	signedDeneb, err := blocks.NewSignedBeaconBlock(deneb)
+	require.NoError(t, err)
+	roDeneb, err := blocks.NewROBlock(signedDeneb)
+	require.NoError(t, err)
+
+	fulu := util.NewBeaconBlockFulu()
+	signedFulu, err := blocks.NewSignedBeaconBlock(fulu)
+	require.NoError(t, err)
+	roFulu, err := blocks.NewROBlock(signedFulu)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name          string
+		setupBlocks   func(t *testing.T) []blocks.BlockWithROSidecars
+		expectedIndex int
+		expectError   bool
+	}{
+		{
+			name: "all blocks are pre-Fulu",
+			setupBlocks: func(t *testing.T) []blocks.BlockWithROSidecars {
+				return []blocks.BlockWithROSidecars{
+					{Block: roBellatrix},
+					{Block: roCapella},
+					{Block: roDeneb},
+				}
+			},
+			expectedIndex: 3, // Should be the length of the slice
+			expectError:   false,
+		},
+		{
+			name: "all blocks are Fulu or later",
+			setupBlocks: func(t *testing.T) []blocks.BlockWithROSidecars {
+				return []blocks.BlockWithROSidecars{
+					{Block: roFulu},
+					{Block: roFulu},
+				}
+			},
+			expectedIndex: 0,
+			expectError:   false,
+		},
+		{
+			name: "mixed blocks correctly sorted",
+			setupBlocks: func(t *testing.T) []blocks.BlockWithROSidecars {
+
+				return []blocks.BlockWithROSidecars{
+					{Block: roBellatrix},
+					{Block: roCapella},
+					{Block: roDeneb},
+					{Block: roFulu},
+					{Block: roFulu},
+				}
+			},
+			expectedIndex: 3, // Index where Fulu blocks start
+			expectError:   false,
+		},
+		{
+			name: "mixed blocks incorrectly sorted",
+			setupBlocks: func(t *testing.T) []blocks.BlockWithROSidecars {
+				return []blocks.BlockWithROSidecars{
+					{Block: roBellatrix},
+					{Block: roCapella},
+					{Block: roFulu},
+					{Block: roDeneb},
+					{Block: roFulu},
+				}
+			},
+			expectedIndex: 0,
+			expectError:   true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			blocks := tt.setupBlocks(t)
+			index, err := findFirstFuluIndex(blocks)
+
+			if tt.expectError {
+				require.NotNil(t, err)
+				return
+			}
+
+			require.NoError(t, err)
+			require.Equal(t, tt.expectedIndex, index)
+		})
+	}
+}

beacon-chain/sync/initial-sync/blocks_fetcher_utils.go

@@ -24,7 +24,7 @@ import (
 type forkData struct {
 	blocksFrom peer.ID
 	blobsFrom  peer.ID
-	bwb        []blocks.BlockWithROBlobs
+	bwb        []blocks.BlockWithROSidecars
 }
 
 // nonSkippedSlotAfter checks slots after the given one in an attempt to find a non-empty future slot.
@@ -275,16 +275,18 @@ func (f *blocksFetcher) findForkWithPeer(ctx context.Context, pid peer.ID, slot
 			"slot": block.Block().Slot(),
 			"root": fmt.Sprintf("%#x", parentRoot),
 		}).Debug("Block with unknown parent root has been found")
-		altBlocks, err := sortedBlockWithVerifiedBlobSlice(blocks[i-1:])
+		bwb, err := sortedBlockWithVerifiedBlobSlice(blocks[i-1:])
 		if err != nil {
 			return nil, errors.Wrap(err, "invalid blocks received in findForkWithPeer")
 		}
+
 		// We need to fetch the blobs for the given alt-chain if any exist, so that we can try to verify and import
 		// the blocks.
-		bpid, bwb, err := f.fetchBlobsFromPeer(ctx, altBlocks, pid, []peer.ID{pid})
+		bpid, err := f.fetchSidecars(ctx, pid, []peer.ID{pid}, bwb)
 		if err != nil {
-			return nil, errors.Wrap(err, "unable to retrieve blobs for blocks found in findForkWithPeer")
+			return nil, errors.Wrap(err, "fetch sidecars")
 		}
+
 		// The caller will use the BlocksWith VerifiedBlobs in bwb as the starting point for
 		// round-robin syncing the alternate chain.
 		return &forkData{blocksFrom: pid, blobsFrom: bpid, bwb: bwb}, nil
@@ -303,10 +305,9 @@ func (f *blocksFetcher) findAncestor(ctx context.Context, pid peer.ID, b interfa
 			if err != nil {
 				return nil, errors.Wrap(err, "received invalid blocks in findAncestor")
 			}
-			var bpid peer.ID
-			bpid, bwb, err = f.fetchBlobsFromPeer(ctx, bwb, pid, []peer.ID{pid})
+			bpid, err := f.fetchSidecars(ctx, pid, []peer.ID{pid}, bwb)
 			if err != nil {
-				return nil, errors.Wrap(err, "unable to retrieve blobs for blocks found in findAncestor")
+				return nil, errors.Wrap(err, "fetch sidecars")
 			}
 			return &forkData{
 				blocksFrom: pid,
@@ -350,9 +351,12 @@ func (f *blocksFetcher) calculateHeadAndTargetEpochs() (headEpoch, targetEpoch p
 		cp := f.chain.FinalizedCheckpt()
 		headEpoch = cp.Epoch
 		targetEpoch, peers = f.p2p.Peers().BestFinalized(params.BeaconConfig().MaxPeersToSync, headEpoch)
-	} else {
-		headEpoch = slots.ToEpoch(f.chain.HeadSlot())
-		targetEpoch, peers = f.p2p.Peers().BestNonFinalized(flags.Get().MinimumSyncPeers, headEpoch)
+
+		return headEpoch, targetEpoch, peers
 	}
+
+	headEpoch = slots.ToEpoch(f.chain.HeadSlot())
+	targetEpoch, peers = f.p2p.Peers().BestNonFinalized(flags.Get().MinimumSyncPeers, headEpoch)
+
 	return headEpoch, targetEpoch, peers
 }

beacon-chain/sync/initial-sync/blocks_queue.go

@@ -72,6 +72,8 @@ type blocksQueueConfig struct {
 	db                  db.ReadOnlyDatabase
 	mode                syncMode
 	bs                  filesystem.BlobStorageSummarizer
+	dcs                 filesystem.DataColumnStorageReader
+	cv                  verification.NewDataColumnsVerifier
 }
 
 // blocksQueue is a priority queue that serves as a intermediary between block fetchers (producers)
@@ -96,7 +98,7 @@ type blocksQueue struct {
 type blocksQueueFetchedData struct {
 	blocksFrom peer.ID
 	blobsFrom  peer.ID
-	bwb        []blocks.BlockWithROBlobs
+	bwb        []blocks.BlockWithROSidecars
 }
 
 // newBlocksQueue creates initialized priority queue.
@@ -115,6 +117,8 @@ func newBlocksQueue(ctx context.Context, cfg *blocksQueueConfig) *blocksQueue {
 			db:     cfg.db,
 			clock:  cfg.clock,
 			bs:     cfg.bs,
+			dcs:    cfg.dcs,
+			cv:     cfg.cv,
 		})
 	}
 	highestExpectedSlot := cfg.highestExpectedSlot

beacon-chain/sync/initial-sync/blocks_queue_test.go

@@ -263,7 +263,7 @@ func TestBlocksQueue_Loop(t *testing.T) {
 				highestExpectedSlot: tt.highestExpectedSlot,
 			})
 			assert.NoError(t, queue.start())
-			processBlock := func(b blocks.BlockWithROBlobs) error {
+			processBlock := func(b blocks.BlockWithROSidecars) error {
 				block := b.Block
 				if !beaconDB.HasBlock(ctx, block.Block().ParentRoot()) {
 					return fmt.Errorf("%w: %#x", errParentDoesNotExist, block.Block().ParentRoot())
@@ -275,7 +275,7 @@ func TestBlocksQueue_Loop(t *testing.T) {
 				return mc.ReceiveBlock(ctx, block, root, nil)
 			}
 
-			var blocks []blocks.BlockWithROBlobs
+			var blocks []blocks.BlockWithROSidecars
 			for data := range queue.fetchedData {
 				for _, b := range data.bwb {
 					if err := processBlock(b); err != nil {
@@ -538,7 +538,7 @@ func TestBlocksQueue_onDataReceivedEvent(t *testing.T) {
 		require.NoError(t, err)
 		response := &fetchRequestResponse{
 			blocksFrom: "abc",
-			bwb: []blocks.BlockWithROBlobs{
+			bwb: []blocks.BlockWithROSidecars{
 				{Block: blocks.ROBlock{ReadOnlySignedBeaconBlock: wsb}},
 				{Block: blocks.ROBlock{ReadOnlySignedBeaconBlock: wsbCopy}},
 			},
@@ -640,7 +640,7 @@ func TestBlocksQueue_onReadyToSendEvent(t *testing.T) {
 		queue.smm.machines[256].fetched.blocksFrom = pidDataParsed
 		rwsb, err := blocks.NewROBlock(wsb)
 		require.NoError(t, err)
-		queue.smm.machines[256].fetched.bwb = []blocks.BlockWithROBlobs{
+		queue.smm.machines[256].fetched.bwb = []blocks.BlockWithROSidecars{
 			{Block: rwsb},
 		}
 
@@ -674,7 +674,7 @@ func TestBlocksQueue_onReadyToSendEvent(t *testing.T) {
 		queue.smm.machines[320].fetched.blocksFrom = pidDataParsed
 		rwsb, err := blocks.NewROBlock(wsb)
 		require.NoError(t, err)
-		queue.smm.machines[320].fetched.bwb = []blocks.BlockWithROBlobs{
+		queue.smm.machines[320].fetched.bwb = []blocks.BlockWithROSidecars{
 			{Block: rwsb},
 		}
 
@@ -705,7 +705,7 @@ func TestBlocksQueue_onReadyToSendEvent(t *testing.T) {
 		queue.smm.machines[320].fetched.blocksFrom = pidDataParsed
 		rwsb, err := blocks.NewROBlock(wsb)
 		require.NoError(t, err)
-		queue.smm.machines[320].fetched.bwb = []blocks.BlockWithROBlobs{
+		queue.smm.machines[320].fetched.bwb = []blocks.BlockWithROSidecars{
 			{Block: rwsb},
 		}
 

beacon-chain/sync/initial-sync/round_robin.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/hex"
 	"fmt"
+	"sort"
 	"time"
 
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/transition"
@@ -13,6 +14,7 @@ import (
 	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/interfaces"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/primitives"
+	"github.com/OffchainLabs/prysm/v6/runtime/version"
 	"github.com/OffchainLabs/prysm/v6/time/slots"
 	"github.com/libp2p/go-libp2p/core/peer"
 	"github.com/paulbellamy/ratecounter"
@@ -78,6 +80,8 @@ func (s *Service) startBlocksQueue(ctx context.Context, highestSlot primitives.S
 		highestExpectedSlot: highestSlot,
 		mode:                mode,
 		bs:                  s.cfg.BlobStorage,
+		dcs:                 s.cfg.DataColumnStorage,
+		cv:                  s.newDataColumnsVerifier,
 	}
 	queue := newBlocksQueue(ctx, cfg)
 	if err := queue.start(); err != nil {
@@ -157,31 +161,82 @@ func (s *Service) processFetchedDataRegSync(ctx context.Context, data *blocksQue
 		log.WithError(err).Debug("Batch did not contain a valid sequence of unprocessed blocks")
 		return 0, err
 	}
+
 	if len(bwb) == 0 {
 		return 0, nil
 	}
-	bv := verification.NewBlobBatchVerifier(s.newBlobVerifier, verification.InitsyncBlobSidecarRequirements)
-	avs := das.NewLazilyPersistentStore(s.cfg.BlobStorage, bv)
-	batchFields := logrus.Fields{
-		"firstSlot":        data.bwb[0].Block.Block().Slot(),
-		"firstUnprocessed": bwb[0].Block.Block().Slot(),
+
+	// Separate blocks with blobs from blocks with data columns.
+	fistDataColumnIndex := sort.Search(len(bwb), func(i int) bool {
+		return bwb[i].Block.Version() >= version.Fulu
+	})
+
+	blocksWithBlobs := bwb[:fistDataColumnIndex]
+	blocksWithDataColumns := bwb[fistDataColumnIndex:]
+
+	blobBatchVerifier := verification.NewBlobBatchVerifier(s.newBlobVerifier, verification.InitsyncBlobSidecarRequirements)
+	lazilyPersistentStoreBlobs := das.NewLazilyPersistentStore(s.cfg.BlobStorage, blobBatchVerifier)
+
+	log := log.WithField("firstSlot", data.bwb[0].Block.Block().Slot())
+	logBlobs, logDataColumns := log, log
+
+	if len(blocksWithBlobs) > 0 {
+		logBlobs = logBlobs.WithField("firstUnprocessed", blocksWithBlobs[0].Block.Block().Slot())
 	}
-	for i, b := range bwb {
-		sidecars := blocks.NewSidecarsFromBlobSidecars(b.Blobs)
-		if err := avs.Persist(s.clock.CurrentSlot(), sidecars...); err != nil {
-			log.WithError(err).WithFields(batchFields).WithFields(syncFields(b.Block)).Warn("Batch failure due to BlobSidecar issues")
+
+	for i, b := range blocksWithBlobs {
+		if err := lazilyPersistentStoreBlobs.Persist(s.clock.CurrentSlot(), b.Blobs...); err != nil {
+			logBlobs.WithError(err).WithFields(syncFields(b.Block)).Warning("Batch failure due to BlobSidecar issues")
 			return uint64(i), err
 		}
-		if err := s.processBlock(ctx, s.genesisTime, b, s.cfg.Chain.ReceiveBlock, avs); err != nil {
+
+		if err := s.processBlock(ctx, s.genesisTime, b, s.cfg.Chain.ReceiveBlock, lazilyPersistentStoreBlobs); err != nil {
 			if errors.Is(err, errParentDoesNotExist) {
-				log.WithFields(batchFields).WithField("missingParent", fmt.Sprintf("%#x", b.Block.Block().ParentRoot())).
+				logBlobs.WithField("missingParent", fmt.Sprintf("%#x", b.Block.Block().ParentRoot())).
 					WithFields(syncFields(b.Block)).Debug("Could not process batch blocks due to missing parent")
 			} else {
-				log.WithError(err).WithFields(batchFields).WithFields(syncFields(b.Block)).Warn("Block processing failure")
+				logBlobs.WithError(err).WithFields(syncFields(b.Block)).Warn("Block processing failure")
 			}
+
 			return uint64(i), err
 		}
 	}
+
+	if len(blocksWithDataColumns) == 0 {
+		return uint64(len(bwb)), nil
+	}
+
+	// Save data column sidecars.
+	count := 0
+	for _, b := range blocksWithDataColumns {
+		count += len(b.Columns)
+	}
+
+	sidecarsToSave := make([]blocks.VerifiedRODataColumn, 0, count)
+	for _, blockWithDataColumns := range blocksWithDataColumns {
+		sidecarsToSave = append(sidecarsToSave, blockWithDataColumns.Columns...)
+	}
+
+	if err := s.cfg.DataColumnStorage.Save(sidecarsToSave); err != nil {
+		return 0, errors.Wrap(err, "save data column sidecars")
+	}
+
+	for i, b := range blocksWithDataColumns {
+		logDataColumns := logDataColumns.WithFields(syncFields(b.Block))
+
+		if err := s.processBlock(ctx, s.genesisTime, b, s.cfg.Chain.ReceiveBlock, nil); err != nil {
+			switch {
+			case errors.Is(err, errParentDoesNotExist):
+				logDataColumns.
+					WithField("missingParent", fmt.Sprintf("%#x", b.Block.Block().ParentRoot())).
+					Debug("Could not process batch blocks due to missing parent")
+				return uint64(i), err
+			default:
+				logDataColumns.WithError(err).Warning("Block processing failure")
+				return uint64(i), err
+			}
+		}
+	}
 	return uint64(len(bwb)), nil
 }
 
@@ -193,12 +248,18 @@ func syncFields(b blocks.ROBlock) logrus.Fields {
 }
 
 // highestFinalizedEpoch returns the absolute highest finalized epoch of all connected peers.
-// Note this can be lower than our finalized epoch if we have no peers or peers that are all behind us.
+// It returns `0` if no peers are connected.
+// Note this can be lower than our finalized epoch if our connected peers are all behind us.
 func (s *Service) highestFinalizedEpoch() primitives.Epoch {
 	highest := primitives.Epoch(0)
 	for _, pid := range s.cfg.P2P.Peers().Connected() {
 		peerChainState, err := s.cfg.P2P.Peers().ChainState(pid)
-		if err == nil && peerChainState != nil && peerChainState.FinalizedEpoch > highest {
+
+		if err != nil || peerChainState == nil {
+			continue
+		}
+
+		if peerChainState.FinalizedEpoch > highest {
 			highest = peerChainState.FinalizedEpoch
 		}
 	}
@@ -250,7 +311,7 @@ func (s *Service) logBatchSyncStatus(firstBlk blocks.ROBlock, nBlocks int) {
 func (s *Service) processBlock(
 	ctx context.Context,
 	genesis time.Time,
-	bwb blocks.BlockWithROBlobs,
+	bwb blocks.BlockWithROSidecars,
 	blockReceiver blockReceiverFn,
 	avs das.AvailabilityStore,
 ) error {
@@ -269,7 +330,7 @@ func (s *Service) processBlock(
 
 type processedChecker func(context.Context, blocks.ROBlock) bool
 
-func validUnprocessed(ctx context.Context, bwb []blocks.BlockWithROBlobs, headSlot primitives.Slot, isProc processedChecker) ([]blocks.BlockWithROBlobs, error) {
+func validUnprocessed(ctx context.Context, bwb []blocks.BlockWithROSidecars, headSlot primitives.Slot, isProc processedChecker) ([]blocks.BlockWithROSidecars, error) {
 	// use a pointer to avoid confusing the zero-value with the case where the first element is processed.
 	var processed *int
 	for i := range bwb {
@@ -299,43 +360,100 @@ func validUnprocessed(ctx context.Context, bwb []blocks.BlockWithROBlobs, headSl
 	return bwb[nonProcessedIdx:], nil
 }
 
-func (s *Service) processBatchedBlocks(ctx context.Context, bwb []blocks.BlockWithROBlobs, bFunc batchBlockReceiverFn) (uint64, error) {
-	if len(bwb) == 0 {
+func (s *Service) processBatchedBlocks(ctx context.Context, bwb []blocks.BlockWithROSidecars, bFunc batchBlockReceiverFn) (uint64, error) {
+	bwbCount := uint64(len(bwb))
+	if bwbCount == 0 {
 		return 0, errors.New("0 blocks provided into method")
 	}
+
 	headSlot := s.cfg.Chain.HeadSlot()
-	var err error
-	bwb, err = validUnprocessed(ctx, bwb, headSlot, s.isProcessedBlock)
+	bwb, err := validUnprocessed(ctx, bwb, headSlot, s.isProcessedBlock)
 	if err != nil {
 		return 0, err
 	}
-	if len(bwb) == 0 {
-		return 0, nil
-	}
 
-	first := bwb[0].Block
-	if !s.cfg.Chain.HasBlock(ctx, first.Block().ParentRoot()) {
+	firstBlock := bwb[0].Block
+	if !s.cfg.Chain.HasBlock(ctx, firstBlock.Block().ParentRoot()) {
 		return 0, fmt.Errorf("%w: %#x (in processBatchedBlocks, slot=%d)",
-			errParentDoesNotExist, first.Block().ParentRoot(), first.Block().Slot())
+			errParentDoesNotExist, firstBlock.Block().ParentRoot(), firstBlock.Block().Slot())
 	}
 
-	bv := verification.NewBlobBatchVerifier(s.newBlobVerifier, verification.InitsyncBlobSidecarRequirements)
-	avs := das.NewLazilyPersistentStore(s.cfg.BlobStorage, bv)
-	s.logBatchSyncStatus(first, len(bwb))
-	for _, bb := range bwb {
-		if len(bb.Blobs) == 0 {
+	firstFuluIndex, err := findFirstFuluIndex(bwb)
+	if err != nil {
+		return 0, errors.Wrap(err, "finding first Fulu index")
+	}
+
+	blocksWithBlobs := bwb[:firstFuluIndex]
+	blocksWithDataColumns := bwb[firstFuluIndex:]
+
+	if err := s.processBlocksWithBlobs(ctx, blocksWithBlobs, bFunc, firstBlock); err != nil {
+		return 0, errors.Wrap(err, "processing blocks with blobs")
+	}
+
+	if err := s.processBlocksWithDataColumns(ctx, blocksWithDataColumns, bFunc, firstBlock); err != nil {
+		return 0, errors.Wrap(err, "processing blocks with data columns")
+	}
+
+	return bwbCount, nil
+}
+
+func (s *Service) processBlocksWithBlobs(ctx context.Context, bwbs []blocks.BlockWithROSidecars, bFunc batchBlockReceiverFn, firstBlock blocks.ROBlock) error {
+	bwbCount := len(bwbs)
+	if bwbCount == 0 {
+		return nil
+	}
+
+	batchVerifier := verification.NewBlobBatchVerifier(s.newBlobVerifier, verification.InitsyncBlobSidecarRequirements)
+	persistentStore := das.NewLazilyPersistentStore(s.cfg.BlobStorage, batchVerifier)
+	s.logBatchSyncStatus(firstBlock, bwbCount)
+
+	for _, bwb := range bwbs {
+		if len(bwb.Blobs) == 0 {
 			continue
 		}
 
-		sidecars := blocks.NewSidecarsFromBlobSidecars(bb.Blobs)
-
-		if err := avs.Persist(s.clock.CurrentSlot(), sidecars...); err != nil {
-			return 0, err
+		if err := persistentStore.Persist(s.clock.CurrentSlot(), bwb.Blobs...); err != nil {
+			return errors.Wrap(err, "persisting blobs")
 		}
 	}
 
-	robs := blocks.BlockWithROBlobsSlice(bwb).ROBlocks()
-	return uint64(len(bwb)), bFunc(ctx, robs, avs)
+	robs := blocks.BlockWithROBlobsSlice(bwbs).ROBlocks()
+	if err := bFunc(ctx, robs, persistentStore); err != nil {
+		return errors.Wrap(err, "processing blocks with blobs")
+	}
+
+	return nil
+}
+
+func (s *Service) processBlocksWithDataColumns(ctx context.Context, bwbs []blocks.BlockWithROSidecars, bFunc batchBlockReceiverFn, firstBlock blocks.ROBlock) error {
+	bwbCount := len(bwbs)
+	if bwbCount == 0 {
+		return nil
+	}
+
+	s.logBatchSyncStatus(firstBlock, bwbCount)
+
+	// Save data column sidecars.
+	count := 0
+	for _, bwb := range bwbs {
+		count += len(bwb.Columns)
+	}
+
+	sidecarsToSave := make([]blocks.VerifiedRODataColumn, 0, count)
+	for _, blockWithDataColumns := range bwbs {
+		sidecarsToSave = append(sidecarsToSave, blockWithDataColumns.Columns...)
+	}
+
+	if err := s.cfg.DataColumnStorage.Save(sidecarsToSave); err != nil {
+		return errors.Wrap(err, "save data column sidecars")
+	}
+
+	robs := blocks.BlockWithROBlobsSlice(bwbs).ROBlocks()
+	if err := bFunc(ctx, robs, nil); err != nil {
+		return errors.Wrap(err, "process post-Fulu blocks")
+	}
+
+	return nil
 }
 
 func isPunishableError(err error) bool {

beacon-chain/sync/initial-sync/round_robin_test.go

@@ -8,9 +8,11 @@ import (
 	"github.com/OffchainLabs/prysm/v6/async/abool"
 	mock "github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain/testing"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/das"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/filesystem"
 	dbtest "github.com/OffchainLabs/prysm/v6/beacon-chain/db/testing"
 	p2pt "github.com/OffchainLabs/prysm/v6/beacon-chain/p2p/testing"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/startup"
+	fieldparams "github.com/OffchainLabs/prysm/v6/config/fieldparams"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/interfaces"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/primitives"
@@ -373,7 +375,7 @@ func TestService_processBlock(t *testing.T) {
 		require.NoError(t, err)
 		rowsb, err := blocks.NewROBlock(wsb)
 		require.NoError(t, err)
-		err = s.processBlock(ctx, genesis, blocks.BlockWithROBlobs{Block: rowsb}, func(
+		err = s.processBlock(ctx, genesis, blocks.BlockWithROSidecars{Block: rowsb}, func(
 			ctx context.Context, block interfaces.ReadOnlySignedBeaconBlock, blockRoot [32]byte, _ das.AvailabilityStore) error {
 			assert.NoError(t, s.cfg.Chain.ReceiveBlock(ctx, block, blockRoot, nil))
 			return nil
@@ -385,7 +387,7 @@ func TestService_processBlock(t *testing.T) {
 		require.NoError(t, err)
 		rowsb, err = blocks.NewROBlock(wsb)
 		require.NoError(t, err)
-		err = s.processBlock(ctx, genesis, blocks.BlockWithROBlobs{Block: rowsb}, func(
+		err = s.processBlock(ctx, genesis, blocks.BlockWithROSidecars{Block: rowsb}, func(
 			ctx context.Context, block interfaces.ReadOnlySignedBeaconBlock, blockRoot [32]byte, _ das.AvailabilityStore) error {
 			return nil
 		}, nil)
@@ -396,7 +398,7 @@ func TestService_processBlock(t *testing.T) {
 		require.NoError(t, err)
 		rowsb, err = blocks.NewROBlock(wsb)
 		require.NoError(t, err)
-		err = s.processBlock(ctx, genesis, blocks.BlockWithROBlobs{Block: rowsb}, func(
+		err = s.processBlock(ctx, genesis, blocks.BlockWithROSidecars{Block: rowsb}, func(
 			ctx context.Context, block interfaces.ReadOnlySignedBeaconBlock, blockRoot [32]byte, _ das.AvailabilityStore) error {
 			assert.NoError(t, s.cfg.Chain.ReceiveBlock(ctx, block, blockRoot, nil))
 			return nil
@@ -432,7 +434,7 @@ func TestService_processBlockBatch(t *testing.T) {
 	s.genesisTime = genesis
 
 	t.Run("process non-linear batch", func(t *testing.T) {
-		var batch []blocks.BlockWithROBlobs
+		var batch []blocks.BlockWithROSidecars
 		currBlockRoot := genesisBlkRoot
 		for i := primitives.Slot(1); i < 10; i++ {
 			parentRoot := currBlockRoot
@@ -446,11 +448,11 @@ func TestService_processBlockBatch(t *testing.T) {
 			require.NoError(t, err)
 			rowsb, err := blocks.NewROBlock(wsb)
 			require.NoError(t, err)
-			batch = append(batch, blocks.BlockWithROBlobs{Block: rowsb})
+			batch = append(batch, blocks.BlockWithROSidecars{Block: rowsb})
 			currBlockRoot = blk1Root
 		}
 
-		var batch2 []blocks.BlockWithROBlobs
+		var batch2 []blocks.BlockWithROSidecars
 		for i := primitives.Slot(10); i < 20; i++ {
 			parentRoot := currBlockRoot
 			blk1 := util.NewBeaconBlock()
@@ -463,7 +465,7 @@ func TestService_processBlockBatch(t *testing.T) {
 			require.NoError(t, err)
 			rowsb, err := blocks.NewROBlock(wsb)
 			require.NoError(t, err)
-			batch2 = append(batch2, blocks.BlockWithROBlobs{Block: rowsb})
+			batch2 = append(batch2, blocks.BlockWithROSidecars{Block: rowsb})
 			currBlockRoot = blk1Root
 		}
 
@@ -485,7 +487,7 @@ func TestService_processBlockBatch(t *testing.T) {
 		assert.ErrorContains(t, "block is already processed", err)
 		require.Equal(t, uint64(0), count)
 
-		var badBatch2 []blocks.BlockWithROBlobs
+		var badBatch2 []blocks.BlockWithROSidecars
 		for i, b := range batch2 {
 			// create a non-linear batch
 			if i%3 == 0 && i != 0 {
@@ -685,7 +687,7 @@ func TestService_ValidUnprocessed(t *testing.T) {
 	require.NoError(t, err)
 	util.SaveBlock(t, t.Context(), beaconDB, genesisBlk)
 
-	var batch []blocks.BlockWithROBlobs
+	var batch []blocks.BlockWithROSidecars
 	currBlockRoot := genesisBlkRoot
 	for i := primitives.Slot(1); i < 10; i++ {
 		parentRoot := currBlockRoot
@@ -699,7 +701,7 @@ func TestService_ValidUnprocessed(t *testing.T) {
 		require.NoError(t, err)
 		rowsb, err := blocks.NewROBlock(wsb)
 		require.NoError(t, err)
-		batch = append(batch, blocks.BlockWithROBlobs{Block: rowsb})
+		batch = append(batch, blocks.BlockWithROSidecars{Block: rowsb})
 		currBlockRoot = blk1Root
 	}
 
@@ -712,3 +714,155 @@ func TestService_ValidUnprocessed(t *testing.T) {
 	// Ensure that the unprocessed batch is returned correctly.
 	assert.Equal(t, len(retBlocks), len(batch)-2)
 }
+
+func TestService_PropcessFetchedDataRegSync(t *testing.T) {
+	ctx := t.Context()
+
+	// Create a data columns storage.
+	dir := t.TempDir()
+	dataColumnStorage, err := filesystem.NewDataColumnStorage(ctx, filesystem.WithDataColumnBasePath(dir))
+	require.NoError(t, err)
+
+	// Create Fulu blocks.
+	fuluBlock1 := util.NewBeaconBlockFulu()
+	signedFuluBlock1, err := blocks.NewSignedBeaconBlock(fuluBlock1)
+	require.NoError(t, err)
+	roFuluBlock1, err := blocks.NewROBlock(signedFuluBlock1)
+	require.NoError(t, err)
+	block1Root := roFuluBlock1.Root()
+
+	fuluBlock2 := util.NewBeaconBlockFulu()
+	fuluBlock2.Block.Body.BlobKzgCommitments = [][]byte{make([]byte, fieldparams.KzgCommitmentSize)} // Dummy commitment.
+	fuluBlock2.Block.Slot = 1
+	fuluBlock2.Block.ParentRoot = block1Root[:]
+	signedFuluBlock2, err := blocks.NewSignedBeaconBlock(fuluBlock2)
+	require.NoError(t, err)
+
+	roFuluBlock2, err := blocks.NewROBlock(signedFuluBlock2)
+	require.NoError(t, err)
+	block2Root := roFuluBlock2.Root()
+	parentRoot2 := roFuluBlock2.Block().ParentRoot()
+	bodyRoot2, err := roFuluBlock2.Block().Body().HashTreeRoot()
+	require.NoError(t, err)
+
+	// Create a mock chain service.
+	const validatorCount = uint64(64)
+	state, _ := util.DeterministicGenesisState(t, validatorCount)
+	chain := &mock.ChainService{
+		FinalizedCheckPoint: &eth.Checkpoint{},
+		DB:                  dbtest.SetupDB(t),
+		State:               state,
+		Root:                block1Root[:],
+	}
+
+	// Create a new service instance.
+	service := &Service{
+		cfg: &Config{
+			Chain:             chain,
+			DataColumnStorage: dataColumnStorage,
+		},
+		counter: ratecounter.NewRateCounter(counterSeconds * time.Second),
+	}
+
+	// Save the parent block in the database.
+	err = chain.DB.SaveBlock(ctx, roFuluBlock1)
+	require.NoError(t, err)
+
+	// Create data column sidecars.
+	const count = uint64(3)
+	params := make([]util.DataColumnParam, 0, count)
+	for i := range count {
+		param := util.DataColumnParam{Index: i, BodyRoot: bodyRoot2[:], ParentRoot: parentRoot2[:], Slot: roFuluBlock2.Block().Slot()}
+		params = append(params, param)
+	}
+	_, verifiedRoDataColumnSidecars := util.CreateTestVerifiedRoDataColumnSidecars(t, params)
+
+	blocksWithSidecars := []blocks.BlockWithROSidecars{
+		{Block: roFuluBlock2, Columns: verifiedRoDataColumnSidecars},
+	}
+
+	data := &blocksQueueFetchedData{
+		bwb: blocksWithSidecars,
+	}
+
+	actual, err := service.processFetchedDataRegSync(ctx, data)
+	require.NoError(t, err)
+	require.Equal(t, uint64(1), actual)
+
+	// Check block and data column sidecars were saved correctly.
+	require.Equal(t, true, chain.DB.HasBlock(ctx, block2Root))
+
+	summary := dataColumnStorage.Summary(block2Root)
+	for i := range count {
+		require.Equal(t, true, summary.HasIndex(i))
+	}
+}
+
+func TestService_processBlocksWithDataColumns(t *testing.T) {
+	ctx := t.Context()
+
+	t.Run("no blocks", func(t *testing.T) {
+		fuluBlock := util.NewBeaconBlockFulu()
+
+		signedFuluBlock, err := blocks.NewSignedBeaconBlock(fuluBlock)
+		require.NoError(t, err)
+		roFuluBlock, err := blocks.NewROBlock(signedFuluBlock)
+		require.NoError(t, err)
+
+		service := new(Service)
+		err = service.processBlocksWithDataColumns(ctx, nil, nil, roFuluBlock)
+		require.NoError(t, err)
+	})
+
+	t.Run("nominal", func(t *testing.T) {
+		fuluBlock := util.NewBeaconBlockFulu()
+		fuluBlock.Block.Body.BlobKzgCommitments = [][]byte{make([]byte, fieldparams.KzgCommitmentSize)} // Dummy commitment.
+		signedFuluBlock, err := blocks.NewSignedBeaconBlock(fuluBlock)
+		require.NoError(t, err)
+		roFuluBlock, err := blocks.NewROBlock(signedFuluBlock)
+		require.NoError(t, err)
+		bodyRoot, err := roFuluBlock.Block().Body().HashTreeRoot()
+		require.NoError(t, err)
+
+		// Create data column sidecars.
+		const count = uint64(3)
+		params := make([]util.DataColumnParam, 0, count)
+		for i := range count {
+			param := util.DataColumnParam{Index: i, BodyRoot: bodyRoot[:]}
+			params = append(params, param)
+		}
+		_, verifiedRoDataColumnSidecars := util.CreateTestVerifiedRoDataColumnSidecars(t, params)
+
+		blocksWithSidecars := []blocks.BlockWithROSidecars{
+			{Block: roFuluBlock, Columns: verifiedRoDataColumnSidecars},
+		}
+
+		// Create a data columns storage.
+		dir := t.TempDir()
+		dataColumnStorage, err := filesystem.NewDataColumnStorage(ctx, filesystem.WithDataColumnBasePath(dir))
+		require.NoError(t, err)
+
+		// Create a service.
+		service := &Service{
+			cfg: &Config{
+				P2P:               p2pt.NewTestP2P(t),
+				DataColumnStorage: dataColumnStorage,
+			},
+			counter: ratecounter.NewRateCounter(counterSeconds * time.Second),
+		}
+
+		receiverFunc := func(ctx context.Context, blks []blocks.ROBlock, avs das.AvailabilityStore) error {
+			require.Equal(t, 1, len(blks))
+			return nil
+		}
+
+		err = service.processBlocksWithDataColumns(ctx, blocksWithSidecars, receiverFunc, roFuluBlock)
+		require.NoError(t, err)
+
+		// Verify that the data columns were saved correctly.
+		summary := dataColumnStorage.Summary(roFuluBlock.Root())
+		for i := range count {
+			require.Equal(t, true, summary.HasIndex(i))
+		}
+	})
+}

beacon-chain/sync/initial-sync/service.go

@@ -12,6 +12,7 @@ import (
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/blockchain"
 	blockfeed "github.com/OffchainLabs/prysm/v6/beacon-chain/core/feed/block"
 	statefeed "github.com/OffchainLabs/prysm/v6/beacon-chain/core/feed/state"
+	"github.com/OffchainLabs/prysm/v6/beacon-chain/core/peerdas"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/das"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/db"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/filesystem"
@@ -21,6 +22,7 @@ import (
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/sync"
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/verification"
 	"github.com/OffchainLabs/prysm/v6/cmd/beacon-chain/flags"
+	fieldparams "github.com/OffchainLabs/prysm/v6/config/fieldparams"
 	"github.com/OffchainLabs/prysm/v6/config/params"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/blocks"
 	"github.com/OffchainLabs/prysm/v6/crypto/rand"
@@ -53,22 +55,24 @@ type Config struct {
 	ClockWaiter         startup.ClockWaiter
 	InitialSyncComplete chan struct{}
 	BlobStorage         *filesystem.BlobStorage
+	DataColumnStorage   *filesystem.DataColumnStorage
 }
 
 // Service service.
 type Service struct {
-	cfg             *Config
-	ctx             context.Context
-	cancel          context.CancelFunc
-	synced          *abool.AtomicBool
-	chainStarted    *abool.AtomicBool
-	counter         *ratecounter.RateCounter
-	genesisChan     chan time.Time
-	clock           *startup.Clock
-	verifierWaiter  *verification.InitializerWaiter
-	newBlobVerifier verification.NewBlobVerifier
-	ctxMap          sync.ContextByteVersions
-	genesisTime     time.Time
+	cfg                    *Config
+	ctx                    context.Context
+	cancel                 context.CancelFunc
+	synced                 *abool.AtomicBool
+	chainStarted           *abool.AtomicBool
+	counter                *ratecounter.RateCounter
+	genesisChan            chan time.Time
+	clock                  *startup.Clock
+	verifierWaiter         *verification.InitializerWaiter
+	newBlobVerifier        verification.NewBlobVerifier
+	newDataColumnsVerifier verification.NewDataColumnsVerifier
+	ctxMap                 sync.ContextByteVersions
+	genesisTime            time.Time
 }
 
 // Option is a functional option for the initial-sync Service.
@@ -149,6 +153,7 @@ func (s *Service) Start() {
 		return
 	}
 	s.newBlobVerifier = newBlobVerifierFromInitializer(v)
+	s.newDataColumnsVerifier = newDataColumnsVerifierFromInitializer(v)
 
 	gt := clock.GenesisTime()
 	if gt.IsZero() {
@@ -175,19 +180,22 @@ func (s *Service) Start() {
 	}
 	s.chainStarted.Set()
 	log.Info("Starting initial chain sync...")
+
 	// Are we already in sync, or close to it?
 	if slots.ToEpoch(s.cfg.Chain.HeadSlot()) == slots.ToEpoch(currentSlot) {
 		log.Info("Already synced to the current chain head")
 		s.markSynced()
 		return
 	}
+
 	peers, err := s.waitForMinimumPeers()
 	if err != nil {
 		log.WithError(err).Error("Error waiting for minimum number of peers")
 		return
 	}
-	if err := s.fetchOriginBlobs(peers); err != nil {
-		log.WithError(err).Error("Failed to fetch missing blobs for checkpoint origin")
+
+	if err := s.fetchOriginSidecars(peers); err != nil {
+		log.WithError(err).Error("Error fetching origin sidecars")
 		return
 	}
 	if err := s.roundRobinSync(); err != nil {
@@ -200,6 +208,50 @@ func (s *Service) Start() {
 	s.markSynced()
 }
 
+// fetchOriginSidecars fetches origin sidecars
+func (s *Service) fetchOriginSidecars(peers []peer.ID) error {
+	const delay = 10 * time.Second // The delay between each attempt to fetch origin data column sidecars
+
+	blockRoot, err := s.cfg.DB.OriginCheckpointBlockRoot(s.ctx)
+	if errors.Is(err, db.ErrNotFoundOriginBlockRoot) {
+		return nil
+	}
+
+	block, err := s.cfg.DB.Block(s.ctx, blockRoot)
+	if err != nil {
+		return errors.Wrap(err, "block")
+	}
+
+	currentSlot, blockSlot := s.clock.CurrentSlot(), block.Block().Slot()
+	currentEpoch, blockEpoch := slots.ToEpoch(currentSlot), slots.ToEpoch(blockSlot)
+
+	if !params.WithinDAPeriod(blockEpoch, currentEpoch) {
+		return nil
+	}
+
+	roBlock, err := blocks.NewROBlockWithRoot(block, blockRoot)
+	if err != nil {
+		return errors.Wrap(err, "new ro block with root")
+	}
+
+	blockVersion := roBlock.Version()
+
+	if blockVersion >= version.Fulu {
+		if err := s.fetchOriginColumns(roBlock, delay); err != nil {
+			return errors.Wrap(err, "fetch origin columns")
+		}
+		return nil
+	}
+
+	if blockVersion >= version.Deneb {
+		if err := s.fetchOriginBlobs(peers, roBlock); err != nil {
+			return errors.Wrap(err, "fetch origin blobs")
+		}
+	}
+
+	return nil
+}
+
 // Stop initial sync.
 func (s *Service) Stop() error {
 	s.cancel()
@@ -304,23 +356,9 @@ func missingBlobRequest(blk blocks.ROBlock, store *filesystem.BlobStorage) (p2pt
 	return req, nil
 }
 
-func (s *Service) fetchOriginBlobs(pids []peer.ID) error {
-	r, err := s.cfg.DB.OriginCheckpointBlockRoot(s.ctx)
-	if errors.Is(err, db.ErrNotFoundOriginBlockRoot) {
-		return nil
-	}
-	blk, err := s.cfg.DB.Block(s.ctx, r)
-	if err != nil {
-		log.WithField("root", fmt.Sprintf("%#x", r)).Error("Block for checkpoint sync origin root not found in db")
-		return err
-	}
-	if !params.WithinDAPeriod(slots.ToEpoch(blk.Block().Slot()), slots.ToEpoch(s.clock.CurrentSlot())) {
-		return nil
-	}
-	rob, err := blocks.NewROBlockWithRoot(blk, r)
-	if err != nil {
-		return err
-	}
+func (s *Service) fetchOriginBlobs(pids []peer.ID, rob blocks.ROBlock) error {
+	r := rob.Root()
+
 	req, err := missingBlobRequest(rob, s.cfg.BlobStorage)
 	if err != nil {
 		return err
@@ -335,16 +373,17 @@ func (s *Service) fetchOriginBlobs(pids []peer.ID) error {
 		if err != nil {
 			continue
 		}
+
 		if len(blobSidecars) != len(req) {
 			continue
 		}
 		bv := verification.NewBlobBatchVerifier(s.newBlobVerifier, verification.InitsyncBlobSidecarRequirements)
 		avs := das.NewLazilyPersistentStore(s.cfg.BlobStorage, bv)
 		current := s.clock.CurrentSlot()
-		sidecars := blocks.NewSidecarsFromBlobSidecars(blobSidecars)
-		if err := avs.Persist(current, sidecars...); err != nil {
+		if err := avs.Persist(current, blobSidecars...); err != nil {
 			return err
 		}
+
 		if err := avs.IsDataAvailable(s.ctx, current, rob); err != nil {
 			log.WithField("root", fmt.Sprintf("%#x", r)).WithField("peerID", pids[i]).Warn("Blobs from peer for origin block were unusable")
 			continue
@@ -355,6 +394,90 @@ func (s *Service) fetchOriginBlobs(pids []peer.ID) error {
 	return fmt.Errorf("no connected peer able to provide blobs for checkpoint sync block %#x", r)
 }
 
+func (s *Service) fetchOriginColumns(roBlock blocks.ROBlock, delay time.Duration) error {
+	const (
+		errorMessage     = "Failed to fetch origin data column sidecars"
+		warningIteration = 10
+	)
+	samplesPerSlot := params.BeaconConfig().SamplesPerSlot
+
+	// Return early if the origin block has no blob commitments.
+	commitments, err := roBlock.Block().Body().BlobKzgCommitments()
+	if err != nil {
+		return errors.Wrap(err, "fetch blob commitments")
+	}
+
+	if len(commitments) == 0 {
+		return nil
+	}
+
+	// Compute the columns to request.
+	custodyGroupCount, err := s.cfg.P2P.CustodyGroupCount()
+	if err != nil {
+		return errors.Wrap(err, "custody group count")
+	}
+
+	samplingSize := max(custodyGroupCount, samplesPerSlot)
+	info, _, err := peerdas.Info(s.cfg.P2P.NodeID(), samplingSize)
+	if err != nil {
+		return errors.Wrap(err, "fetch peer info")
+	}
+
+	// Fetch origin data column sidecars.
+	root := roBlock.Root()
+
+	params := sync.DataColumnSidecarsParams{
+		Ctx:                     s.ctx,
+		Tor:                     s.clock,
+		P2P:                     s.cfg.P2P,
+		CtxMap:                  s.ctxMap,
+		Storage:                 s.cfg.DataColumnStorage,
+		NewVerifier:             s.newDataColumnsVerifier,
+		DownscorePeerOnRPCFault: true,
+	}
+
+	var verifiedRoDataColumnsByRoot map[[fieldparams.RootLength]byte][]blocks.VerifiedRODataColumn
+	for attempt := uint64(0); ; attempt++ {
+		verifiedRoDataColumnsByRoot, err = sync.FetchDataColumnSidecars(params, []blocks.ROBlock{roBlock}, info.CustodyColumns)
+		if err == nil {
+			break
+		}
+
+		log := log.WithError(err).WithFields(logrus.Fields{
+			"attempt": attempt,
+			"delay":   delay,
+		})
+
+		if attempt%warningIteration == 0 && attempt > 0 {
+			log.Warning(errorMessage)
+			time.Sleep(delay)
+
+			continue
+		}
+
+		log.Debug(errorMessage)
+		time.Sleep(delay)
+	}
+
+	// Save origin data columns to disk.
+	verifiedRoDataColumnsSidecars, ok := verifiedRoDataColumnsByRoot[root]
+	if !ok {
+		return fmt.Errorf("cannot extract origins data column sidecars for block root %#x - should never happen", root)
+	}
+
+	if err := s.cfg.DataColumnStorage.Save(verifiedRoDataColumnsSidecars); err != nil {
+		return errors.Wrap(err, "save data column sidecars")
+	}
+
+	log.WithFields(logrus.Fields{
+		"blockRoot":   fmt.Sprintf("%#x", roBlock.Root()),
+		"blobCount":   len(commitments),
+		"columnCount": len(verifiedRoDataColumnsSidecars),
+	}).Info("Successfully downloaded data column sidecars for checkpoint sync block")
+
+	return nil
+}
+
 func shufflePeers(pids []peer.ID) {
 	rg := rand.NewGenerator()
 	rg.Shuffle(len(pids), func(i, j int) {
@@ -367,3 +490,9 @@ func newBlobVerifierFromInitializer(ini *verification.Initializer) verification.
 		return ini.NewBlobVerifier(b, reqs)
 	}
 }
+
+func newDataColumnsVerifierFromInitializer(ini *verification.Initializer) verification.NewDataColumnsVerifier {
+	return func(roDataColumns []blocks.RODataColumn, reqs []verification.Requirement) verification.DataColumnsVerifier {
+		return ini.NewDataColumnsVerifier(roDataColumns, reqs)
+	}
+}