Merge branch 'develop' into dont_fcu_to_nil

subscribeToSubnets: Remove unused parameter. (#15079 )
* `subscribeToSubnets`: Remove unused parameter. * Changelog: Change `Fixed` to `Ignored`.
2026-01-10 05:47:59 -05:00 · 2025-03-20 14:14:56 -03:00 · 2025-03-20 15:57:55 +00:00 · 2025-03-20 10:00:40 +00:00 · 2025-03-19 18:04:15 +00:00 · 2025-03-19 15:10:30 +00:00
289 changed files with 6216 additions and 1946 deletions
--- a/.github/actions/gomodtidy/Dockerfile
+++ b/.github/actions/gomodtidy/Dockerfile
@@ -1,4 +1,4 @@
-FROM golang:1.23-alpine
+FROM golang:1.24-alpine

 COPY entrypoint.sh /entrypoint.sh

--- a/.github/workflows/changelog.yml
+++ b/.github/workflows/changelog.yml
@@ -12,7 +12,7 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout source code
-        uses: actions/checkout@v3
+        uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3.6.0

      - name: Download unclog binary
        uses: dsaltares/fetch-gh-release-asset@aa2ab1243d6e0d5b405b973c89fa4d06a2d0fff7 # 1.1.2
@@ -23,7 +23,7 @@ jobs:

      - name: Get new changelog files
        id: new-changelog-files
-        uses: tj-actions/changed-files@v45
+        uses: OffchainLabs/gh-action-changed-files@9200e69727eb73eb060652b19946b8a2fdfb654b # v4.0.8
        with:
          files: |
            changelog/**.md
--- a/.github/workflows/go.yml
+++ b/.github/workflows/go.yml
@@ -28,15 +28,15 @@ jobs:
    steps:
      - name: Checkout
        uses: actions/checkout@v4
-      - name: Set up Go 1.23
+      - name: Set up Go 1.24
        uses: actions/setup-go@v4
        with:
-          go-version: '1.23.5'
+          go-version: '1.24.0'
      - name: Run Gosec Security Scanner
        run: | # https://github.com/securego/gosec/issues/469
          export PATH=$PATH:$(go env GOPATH)/bin
-          go install github.com/securego/gosec/v2/cmd/gosec@v2.19.0
-          gosec -exclude-generated -exclude=G307 -exclude-dir=crypto/bls/herumi ./...
+          go install github.com/securego/gosec/v2/cmd/gosec@v2.22.1
+          gosec -exclude-generated -exclude=G307,G115 -exclude-dir=crypto/bls/herumi ./...

  lint:
    name: Lint
@@ -45,16 +45,16 @@ jobs:
      - name: Checkout
        uses: actions/checkout@v4

-      - name: Set up Go 1.23
+      - name: Set up Go 1.24
        uses: actions/setup-go@v4
        with:
-          go-version: '1.23.5'
+          go-version: '1.24.0'
          id: go

      - name: Golangci-lint
        uses: golangci/golangci-lint-action@v5
        with:
-          version: v1.63.4
+          version: v1.64.5
          args: --config=.golangci.yml --out-${NO_FUTURE}format colored-line-number

  build:
@@ -64,7 +64,7 @@ jobs:
      - name: Set up Go 1.x
        uses: actions/setup-go@v4
        with:
-          go-version: '1.23.5'
+          go-version: '1.24.0'
        id: go

      - name: Check out code into the Go module directory
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -75,6 +75,7 @@ linters:
    - tagliatelle
    - thelper
    - unparam
+    - usetesting
    - varnamelen
    - wrapcheck
    - wsl
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -165,7 +165,7 @@ STATICCHECK_ANALYZERS = [
    "sa6006",
    "sa9001",
    "sa9002",
-    #"sa9003", # Doesn't build. See https://github.com/dominikh/go-tools/pull/1483
+    "sa9003",
    "sa9004",
    "sa9005",
    "sa9006",
@@ -197,6 +197,7 @@ nogo(
        "//tools/analyzers/logruswitherror:go_default_library",
        "//tools/analyzers/maligned:go_default_library",
        "//tools/analyzers/nop:go_default_library",
+        "//tools/analyzers/nopanic:go_default_library",
        "//tools/analyzers/properpermissions:go_default_library",
        "//tools/analyzers/recursivelock:go_default_library",
        "//tools/analyzers/shadowpredecl:go_default_library",
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,102 @@ All notable changes to this project will be documented in this file.

 The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

+## [v5.3.1](https://github.com/prysmaticlabs/prysm/compare/v5.3.0...v5.3.1) - 2025-03-13
+
+This release is packed with critical fixes for **Electra** and some important fixes for mainnet too. 
+
+The release highlights include:
+
+- Ensure that deleting a block from the database clears its entry in the slot->root db index. This issue was causing some operators to have a bricked database, requiring a full resync. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15011)
+- Updated go to go1.24.0. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14969)
+- Added a feature flag to sync from an arbitrary beacon block root at startup. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15000)
+- Updated default gas limit from 30M to 36M. Override this with `--suggested-gas-limit=` in the validator client. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14858)
+
+Known issues in **Electra**:
+
+- Duplicate attestations are needlessly processed. This is being addressed in [[PR]](https://github.com/prysmaticlabs/prysm/pull/15034).
+
+Testnet operators are strongly encouraged to update to this release. There are many fixes and improvements from the Holesky upgrade incident.
+
+Mainner operators are recommended to update to this release at their regular cadence. 
+
+### Added
+
+- enable E2E for minimal and mainnet tests. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14842)
+- enable web3signer E2E for electra. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14936)
+- Enable multiclient E2E for electra. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14946)
+- Enable Scenario E2E tests with electra. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14946)
+- Add endpoint for getting pending deposits. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14941)
+- Add request hash to header for builder: executable data to block. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14955)
+- Log execution requests in each block. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14956)
+- Add endpoint for getting pending partial withdrawals. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14949)
+- Tracked validators cache: Added the `ItemCount` method. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14957)
+- Tracked validators cache: Added the `Indices` method. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14957)
+- Added deposit request testing for electra. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14964)
+- Added support for otel tracing transport in HTTP clients in Prysm. This allows for tracing headers to be sent with http requests such that spans between the validator and beacon chain can be connected in the tracing graph. This change does nothing without `--enable-tracing`. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14972)
+- Add SSZ support to light client finality and optimistic APIs. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14836)
+- add log to committee index when committeebits are not the expected length of 1. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14993)
+- Add acceptable address types for static peers. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14886)
+- Added a feature flag to sync from an arbitrary beacon block root at startup. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15000)
+
+### Changed
+
+- updates geth to 1.15.0. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14842)
+- Updates blst to v3.14.0 and fixes the references in our deps.bzl file. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14921)
+- Updated tracing exporter from jaeger to otelhttp. This should not be a breaking change. Jaeger supports otel format, however you may need to update your URL as the default otel-collector port is 4318. See the [OpenTelemtry Protocol Exporter docs](https://opentelemetry.io/docs/specs/otel/protocol/exporter/) for more details. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14928)
+- Don't use MaxCover for Electra on-chain attestations. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14925)
+- Tracked validators cache: Remove validators from the cache if not seen after 1 hour. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14957)
+- execution requests errors on ssz length have been improved. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14962)
+- deprecate beacon api endpoints based on [3.0.0 release](https://github.com/ethereum/beacon-APIs/pull/506) for electra. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14967)
+- Use go-cmp for printing better diffs for assertions.DeepEqual. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14978)
+- Reorganized beacon chain flags in `--help` text into logical sections. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14959)
+- `--validators-registration-batch-size`: Change default value from `0` to `200`. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14981)
+- Updated go to go1.24.0. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14969)
+- Updated gosec to v2.22.1 and golangci to v1.64.5. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14969)
+- Updated github.com/trailofbits/go-mutexasserts. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14969)
+- Updated rules_go to cf3c3af34bd869b864f5f2b98e2f41c2b220d6c9 to support go1.24.0. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14969)
+- Validate blob sidecar re-order signature and bad parent block. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15013)
+- Updated default gas limit from 30M to 36M. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14858)
+- Ignore errors from `hasSeenBit` and don't pack unaggregated attestations. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15018)
+
+### Removed
+
+- Remove Fulu state and block. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14905)
+- Removed the log summarizing all started services. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14958)
+
+### Fixed
+
+- fixed max and target blob per block from static to dynamic values. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14911)
+- refactored publish block and block ssz functions to fix gocognit. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14913)
+- refactored publish blinded block and blinded block ssz to correctly deal with version headers and sent blocks. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14913)
+- Only check for electra related engine methods if electra is active. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14924)
+- Fixed bug that breaks new blob storage layout code on Windows, caused by accidental use of platform-dependent path parsing package. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14931)
+- Fix E2E Process Deposit Evaluator for Electra. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14933)
+- Fixed the `bazel run //:gazelle` command in `DEPENDENCIES.md`. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14934)
+- Fix E2E Deposit Activation Evaluator for Electra. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14938)
+- Dedicated processing of `SingleAttestation` in the monitor service. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14965)
+- adding in content type and accept headers for builder API call on registration. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14961)
+- fixed gocognit in block conversions between json and proto types. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14953)
+- Lint: Fix violations of S1009: should omit nil check; len() for nil slices is defined as zero. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14973)
+- Lint: Fix violations of non-constant format string in call. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14974)
+- Fixed violations of gosec G301. This is a check that created files and directories have file permissions 0750 and 0600 respectively. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14980)
+- Check for the correct attester slashing type during gossip validation. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14985)
+- cosmetic fix for post electra validator logs displaying attestation committee information correctly. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14992)
+- fix inserting the wrong committee index into the seen cache for electra attestations. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14998)
+- Allow any block type to be unmarshaled rather than only phase0 blocks in `slotByBlockRoot`. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15008)
+- Fixed pruner to not block while pruning large database by introducing batchSize. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14929)
+- Decompose Electra block attestations to prevent redundant packing. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14896)
+- Fixed use of deprecated rand.Seed. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14969)
+- Fixed build issue with SszGen where the go binary was not present in the $PATH. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14969)
+- fixed /eth/v1/config/spec displays BLOB_SIDECAR_SUBNET_COUNT,BLOB_SIDECAR_SUBNET_COUNT_ELECTRA. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15016)
+- Ensure that deleting a block from the database clears its entry in the slot->root db index. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15011)
+- Broadcasting BLS to execution changes should not use the request context in a go routine. Use context.Background() for the broadcasting go routine. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15019)
+- /eth/v1/validator/sync_committee_contribution should check for optimistic status and return a 503 if it's optimistic. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15022)
+- Fixes printing superfluous response.WriteHeader call from error in builder. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15025)
+- Fixes e2e run with builder having wrong gaslimit header due to not being set on eth1 nodes. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15025)
+- Fixed a bug in the event stream handler when processing payload attribute events where the timestamp and slot of the event would be based on the head rather than the current slot. [[PR]](https://github.com/prysmaticlabs/prysm/pull/14963)
+- Handle unaggregated attestations when decomposing Electra block attestations. [[PR]](https://github.com/prysmaticlabs/prysm/pull/15027)
+
 ## [v5.3.0](https://github.com/prysmaticlabs/prysm/compare/v5.2.0...v5.3.0) - 2025-02-12

 This release includes support for Pectra activation in the [Holesky](https://github.com/eth-clients/holesky) and [Sepolia](https://github.com/eth-clients/sepolia) testnets! The release contains many fixes for Electra that have been found in rigorous testing through devnets in the last few months.
--- a/48
+++ b/48
@@ -160,15 +160,15 @@ oci_register_toolchains(

 http_archive(
    name = "io_bazel_rules_go",
+    integrity = "sha256-JD8o94crTb2DFiJJR8nMAGdBAW95zIENB4cbI+JnrI4=",
    patch_args = ["-p1"],
    patches = [
        # Expose internals of go_test for custom build transitions.
        "//third_party:io_bazel_rules_go_test.patch",
    ],
-    sha256 = "b2038e2de2cace18f032249cb4bb0048abf583a36369fa98f687af1b3f880b26",
+    strip_prefix = "rules_go-cf3c3af34bd869b864f5f2b98e2f41c2b220d6c9",
    urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/rules_go/releases/download/v0.48.1/rules_go-v0.48.1.zip",
-        "https://github.com/bazelbuild/rules_go/releases/download/v0.48.1/rules_go-v0.48.1.zip",
+        "https://github.com/bazel-contrib/rules_go/archive/cf3c3af34bd869b864f5f2b98e2f41c2b220d6c9.tar.gz",
    ],
 )

@@ -210,7 +210,7 @@ load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_depe
 go_rules_dependencies()

 go_register_toolchains(
-    go_version = "1.23.5",
+    go_version = "1.24.0",
    nogo = "@//:nogo",
 )

@@ -255,7 +255,7 @@ filegroup(
    url = "https://github.com/ethereum/EIPs/archive/5480440fe51742ed23342b68cf106cefd427e39d.tar.gz",
 )

-consensus_spec_version = "v1.5.0-beta.2"
+consensus_spec_version = "v1.5.0-beta.3"

 bls_test_version = "v0.1.1"

@@ -271,7 +271,7 @@ filegroup(
    visibility = ["//visibility:public"],
 )
    """,
-    integrity = "sha256-X/bMxbKg1clo2aFEjBoeuFq/U+BF1eQopgRP/7nI3Qg=",
+    integrity = "sha256-z+j0BEJuXMBKbGL+7jq35zddzZMW1je8/uvTz5+wboQ=",
    url = "https://github.com/ethereum/consensus-spec-tests/releases/download/%s/general.tar.gz" % consensus_spec_version,
 )

@@ -287,7 +287,7 @@ filegroup(
    visibility = ["//visibility:public"],
 )
    """,
-    integrity = "sha256-WSxdri5OJGuNApW+odKle5UzToDyEOx+F3lMiqamJAg=",
+    integrity = "sha256-5/YUOXH65CmM1plZ8twJ3BQxwM51jgSpOB8/VSBI19k=",
    url = "https://github.com/ethereum/consensus-spec-tests/releases/download/%s/minimal.tar.gz" % consensus_spec_version,
 )

@@ -303,7 +303,7 @@ filegroup(
    visibility = ["//visibility:public"],
 )
    """,
-    integrity = "sha256-LYE8l3y/zSt4YVrehrJ3ralqtgeYNildiIp+HR6+xAI=",
+    integrity = "sha256-iZ2eNhwRnbxrjR+5gMBUYakaCXicvPChwFUkZtQUbbI=",
    url = "https://github.com/ethereum/consensus-spec-tests/releases/download/%s/mainnet.tar.gz" % consensus_spec_version,
 )

@@ -318,7 +318,7 @@ filegroup(
    visibility = ["//visibility:public"],
 )
    """,
-    integrity = "sha256-jvZQ90qcJMTOqMsPO7sgeEVQmewZTHcz7LVDkNqwTFQ=",
+    integrity = "sha256-inAXV7xNM5J1aUdP7JNXFO2iFFZ7dth38Ji+mJW50Ts=",
    strip_prefix = "consensus-specs-" + consensus_spec_version[1:],
    url = "https://github.com/ethereum/consensus-specs/archive/refs/tags/%s.tar.gz" % consensus_spec_version,
 )
@@ -365,9 +365,9 @@ filegroup(
    visibility = ["//visibility:public"],
 )
 """,
-    integrity = "sha256-b7ZTT+olF+VXEJYNTV5jggNtCkt9dOejm1i2VE+zy+0=",
-    strip_prefix = "holesky-874c199423ccd180607320c38cbaca05d9a1573a",
-    url = "https://github.com/eth-clients/holesky/archive/874c199423ccd180607320c38cbaca05d9a1573a.tar.gz",  # 2024-06-18
+    integrity = "sha256-YVFFrCmjoGZ3fXMWpsCpSsYbANy1grnqYwOLKIg2SsA=",
+    strip_prefix = "holesky-32a72e21c6e53c262f27d50dd540cb654517d03a",
+    url = "https://github.com/eth-clients/holesky/archive/32a72e21c6e53c262f27d50dd540cb654517d03a.tar.gz",  # 2025-03-17
 )

 http_archive(
@@ -381,9 +381,25 @@ filegroup(
    visibility = ["//visibility:public"],
 )
 """,
-    integrity = "sha256-cY/UgpCcYEhQf7JefD65FI8tn/A+rAvKhcm2/qiVdqY=",
-    strip_prefix = "sepolia-f2c219a93c4491cee3d90c18f2f8e82aed850eab",
-    url = "https://github.com/eth-clients/sepolia/archive/f2c219a93c4491cee3d90c18f2f8e82aed850eab.tar.gz",  # 2024-09-19
+    integrity = "sha256-b5F7Wg9LLMqGRIpP2uqb/YsSFVn2ynzlV7g/Nb1EFLk=",
+    strip_prefix = "sepolia-562d9938f08675e9ba490a1dfba21fb05843f39f",
+    url = "https://github.com/eth-clients/sepolia/archive/562d9938f08675e9ba490a1dfba21fb05843f39f.tar.gz",  # 2025-03-17
+)
+
+http_archive(
+    name = "hoodi_testnet",
+    build_file_content = """
+filegroup(
+    name = "configs",
+    srcs = [
+        "metadata/config.yaml",
+    ],
+    visibility = ["//visibility:public"],
+)
+""",
+    integrity = "sha256-dPiEWUd8QvbYGwGtIm0QtCekitVLOLsW5rpQIGzz8PU=",
+    strip_prefix = "hoodi-828c2c940e1141092bd4bb979cef547ea926d272",
+    url = "https://github.com/eth-clients/hoodi/archive/828c2c940e1141092bd4bb979cef547ea926d272.tar.gz",
 )

 http_archive(
@@ -431,7 +447,7 @@ gometalinter_dependencies()

 load("@bazel_gazelle//:deps.bzl", "gazelle_dependencies")

-gazelle_dependencies()
+gazelle_dependencies(go_sdk = "go_sdk")

 load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")

--- a/api/client/beacon/BUILD.bazel
+++ b/api/client/beacon/BUILD.bazel
@@ -7,6 +7,7 @@ go_library(
        "doc.go",
        "health.go",
        "log.go",
+        "template.go",
    ],
    importpath = "github.com/prysmaticlabs/prysm/v5/api/client/beacon",
    visibility = ["//visibility:public"],
--- a/api/client/beacon/client.go
+++ b/api/client/beacon/client.go
@@ -11,7 +11,6 @@ import (
 	"regexp"
 	"sort"
 	"strconv"
-	"text/template"

 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/pkg/errors"
@@ -64,23 +63,6 @@ func IdFromSlot(s primitives.Slot) StateOrBlockId {
 	return StateOrBlockId(strconv.FormatUint(uint64(s), 10))
 }

-// idTemplate is used to create template functions that can interpolate StateOrBlockId values.
-func idTemplate(ts string) func(StateOrBlockId) string {
-	t := template.Must(template.New("").Parse(ts))
-	f := func(id StateOrBlockId) string {
-		b := bytes.NewBuffer(nil)
-		err := t.Execute(b, struct{ Id string }{Id: string(id)})
-		if err != nil {
-			panic(fmt.Sprintf("invalid idTemplate: %s", ts))
-		}
-		return b.String()
-	}
-	// run the template to ensure that it is valid
-	// this should happen load time (using package scoped vars) to ensure runtime errors aren't possible
-	_ = f(IdGenesis)
-	return f
-}
-
 // RenderGetBlockPath formats a block id into a path for the GetBlock API endpoint.
 func RenderGetBlockPath(id StateOrBlockId) string {
 	return path.Join(getSignedBlockPath, string(id))
@@ -114,8 +96,6 @@ func (c *Client) GetBlock(ctx context.Context, blockId StateOrBlockId) ([]byte,
 	return b, nil
 }

-var getBlockRootTpl = idTemplate(getBlockRootPath)
-
 // GetBlockRoot retrieves the hash_tree_root of the BeaconBlock for the given block id.
 // Block identifier can be one of: "head" (canonical head in node's view), "genesis", "finalized",
 // <slot>, <hex encoded blockRoot with 0x prefix>. Variables of type StateOrBlockId are exported by this package
@@ -138,8 +118,6 @@ func (c *Client) GetBlockRoot(ctx context.Context, blockId StateOrBlockId) ([32]
 	return bytesutil.ToBytes32(rs), nil
 }

-var getForkTpl = idTemplate(getForkForStatePath)
-
 // GetFork queries the Beacon Node API for the Fork from the state identified by stateId.
 // Block identifier can be one of: "head" (canonical head in node's view), "genesis", "finalized",
 // <slot>, <hex encoded blockRoot with 0x prefix>. Variables of type StateOrBlockId are exported by this package
--- a/api/client/beacon/template.go
+++ b/api/client/beacon/template.go
@@ -0,0 +1,34 @@
+package beacon
+
+import (
+	"bytes"
+	"fmt"
+	"text/template"
+)
+
+type templateFn func(StateOrBlockId) string
+
+var getBlockRootTpl templateFn
+var getForkTpl templateFn
+
+func init() {
+	// idTemplate is used to create template functions that can interpolate StateOrBlockId values.
+	idTemplate := func(ts string) func(StateOrBlockId) string {
+		t := template.Must(template.New("").Parse(ts))
+		f := func(id StateOrBlockId) string {
+			b := bytes.NewBuffer(nil)
+			err := t.Execute(b, struct{ Id string }{Id: string(id)})
+			if err != nil {
+				panic(fmt.Sprintf("invalid idTemplate: %s", ts))
+			}
+			return b.String()
+		}
+		// run the template to ensure that it is valid
+		// this should happen load time (using package scoped vars) to ensure runtime errors aren't possible
+		_ = f(IdGenesis)
+		return f
+	}
+
+	getBlockRootTpl = idTemplate(getBlockRootPath)
+	getForkTpl = idTemplate(getForkForStatePath)
+}
--- a/api/client/builder/client.go
+++ b/api/client/builder/client.go
@@ -16,6 +16,7 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/api"
 	"github.com/prysmaticlabs/prysm/v5/api/client"
 	"github.com/prysmaticlabs/prysm/v5/api/server/structs"
+	"github.com/prysmaticlabs/prysm/v5/config/params"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
@@ -35,9 +36,14 @@ const (
 	postRegisterValidatorPath  = "/eth/v1/builder/validators"
 )

-var errMalformedHostname = errors.New("hostname must include port, separated by one colon, like example.com:3500")
-var errMalformedRequest = errors.New("required request data are missing")
-var errNotBlinded = errors.New("submitted block is not blinded")
+var (
+	vrExample             = &ethpb.SignedValidatorRegistrationV1{}
+	vrSize                = vrExample.SizeSSZ()
+	errMalformedHostname  = errors.New("hostname must include port, separated by one colon, like example.com:3500")
+	errMalformedRequest   = errors.New("required request data are missing")
+	errNotBlinded         = errors.New("submitted block is not blinded")
+	errVersionUnsupported = errors.New("version is not supported")
+)

 // ClientOpt is a functional option for the Client type (http.Client wrapper)
 type ClientOpt func(*Client)
@@ -52,6 +58,12 @@ func WithObserver(m observer) ClientOpt {
 	}
 }

+func WithSSZ() ClientOpt {
+	return func(c *Client) {
+		c.sszEnabled = true
+	}
+}
+
 type requestLogger struct{}

 func (*requestLogger) observe(r *http.Request) (e error) {
@@ -95,9 +107,10 @@ type BuilderClient interface {

 // Client provides a collection of helper methods for calling Builder API endpoints.
 type Client struct {
-	hc      *http.Client
-	baseURL *url.URL
-	obvs    []observer
+	hc         *http.Client
+	baseURL    *url.URL
+	obvs       []observer
+	sszEnabled bool
 }

 // NewClient constructs a new client with the provided options (ex WithTimeout).
@@ -139,7 +152,7 @@ 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, err error) {
+func (c *Client) do(ctx context.Context, method string, path string, body io.Reader, opts ...reqOption) (res []byte, header http.Header, err error) {
 	ctx, span := trace.StartSpan(ctx, "builder.client.do")
 	defer func() {
 		tracing.AnnotateError(span, err)
@@ -155,10 +168,6 @@ func (c *Client) do(ctx context.Context, method string, path string, body io.Rea
 	if err != nil {
 		return
 	}
-	if method == http.MethodPost {
-		req.Header.Set("Content-Type", api.JsonMediaType)
-	}
-	req.Header.Set("Accept", api.JsonMediaType)
 	req.Header.Add("User-Agent", version.BuildData())
 	for _, o := range opts {
 		o(req)
@@ -187,6 +196,7 @@ func (c *Client) do(ctx context.Context, method string, path string, body io.Rea
 		err = errors.Wrap(err, "error reading http response body from builder server")
 		return
 	}
+	header = r.Header
 	return
 }

@@ -216,64 +226,145 @@ func (c *Client) GetHeader(ctx context.Context, slot primitives.Slot, parentHash
 	if err != nil {
 		return nil, err
 	}
-	hb, err := c.do(ctx, http.MethodGet, path, nil)
-	if err != nil {
-		return nil, err
+	var getOpts reqOption
+	if c.sszEnabled {
+		getOpts = func(r *http.Request) {
+			r.Header.Set("Accept", api.OctetStreamMediaType)
+		}
+	} else {
+		getOpts = func(r *http.Request) {
+			r.Header.Set("Accept", api.JsonMediaType)
+		}
 	}
-	v := &VersionResponse{}
-	if err := json.Unmarshal(hb, v); err != nil {
-		return nil, errors.Wrapf(err, "error unmarshaling the builder GetHeader response, using slot=%d, parentHash=%#x, pubkey=%#x", slot, parentHash, pubkey)
+	data, header, err := c.do(ctx, http.MethodGet, path, nil, getOpts)
+	if err != nil {
+		return nil, errors.Wrap(err, "error getting header from builder server")
 	}

-	ver, err := version.FromString(strings.ToLower(v.Version))
+	bid, err := c.parseHeaderResponse(data, header)
 	if err != nil {
-		return nil, errors.Wrap(err, fmt.Sprintf("unsupported header version %s", strings.ToLower(v.Version)))
+		return nil, errors.Wrapf(
+			err,
+			"error rendering exec header template with slot=%d, parentHash=%#x, pubkey=%#x",
+			slot,
+			parentHash,
+			pubkey,
+		)
 	}
+	return bid, nil
+}
+
+func (c *Client) parseHeaderResponse(data []byte, header http.Header) (SignedBid, error) {
+	var versionHeader string
+	if c.sszEnabled || header.Get(api.VersionHeader) != "" {
+		versionHeader = header.Get(api.VersionHeader)
+	} else {
+		// If we don't have a version header, attempt to parse JSON for version
+		v := &VersionResponse{}
+		if err := json.Unmarshal(data, v); err != nil {
+			return nil, errors.Wrap(
+				err,
+				"error unmarshaling builder GetHeader response",
+			)
+		}
+		versionHeader = strings.ToLower(v.Version)
+	}
+
+	ver, err := version.FromString(versionHeader)
+	if err != nil {
+		return nil, errors.Wrap(err, fmt.Sprintf("unsupported header version %s", versionHeader))
+	}
+
 	if ver >= version.Electra {
-		hr := &ExecHeaderResponseElectra{}
-		if err := json.Unmarshal(hb, hr); err != nil {
-			return nil, errors.Wrapf(err, "error unmarshaling the builder GetHeader response, using slot=%d, parentHash=%#x, pubkey=%#x", slot, parentHash, pubkey)
-		}
-		p, err := hr.ToProto()
-		if err != nil {
-			return nil, errors.Wrapf(err, "could not extract proto message from header")
-		}
-		return WrappedSignedBuilderBidElectra(p)
+		return c.parseHeaderElectra(data)
 	}
 	if ver >= version.Deneb {
-		hr := &ExecHeaderResponseDeneb{}
-		if err := json.Unmarshal(hb, hr); err != nil {
-			return nil, errors.Wrapf(err, "error unmarshaling the builder GetHeader response, using slot=%d, parentHash=%#x, pubkey=%#x", slot, parentHash, pubkey)
-		}
-		p, err := hr.ToProto()
-		if err != nil {
-			return nil, errors.Wrapf(err, "could not extract proto message from header")
-		}
-		return WrappedSignedBuilderBidDeneb(p)
+		return c.parseHeaderDeneb(data)
 	}
 	if ver >= version.Capella {
-		hr := &ExecHeaderResponseCapella{}
-		if err := json.Unmarshal(hb, hr); err != nil {
-			return nil, errors.Wrapf(err, "error unmarshaling the builder GetHeader response, using slot=%d, parentHash=%#x, pubkey=%#x", slot, parentHash, pubkey)
-		}
-		p, err := hr.ToProto()
-		if err != nil {
-			return nil, errors.Wrapf(err, "could not extract proto message from header")
-		}
-		return WrappedSignedBuilderBidCapella(p)
+		return c.parseHeaderCapella(data)
 	}
 	if ver >= version.Bellatrix {
-		hr := &ExecHeaderResponse{}
-		if err := json.Unmarshal(hb, hr); err != nil {
-			return nil, errors.Wrapf(err, "error unmarshaling the builder GetHeader response, using slot=%d, parentHash=%#x, pubkey=%#x", slot, parentHash, pubkey)
-		}
-		p, err := hr.ToProto()
-		if err != nil {
-			return nil, errors.Wrap(err, "could not extract proto message from header")
-		}
-		return WrappedSignedBuilderBid(p)
+		return c.parseHeaderBellatrix(data)
 	}
-	return nil, fmt.Errorf("unsupported header version %s", strings.ToLower(v.Version))
+
+	return nil, fmt.Errorf("unsupported header version %s", versionHeader)
+}
+
+func (c *Client) parseHeaderElectra(data []byte) (SignedBid, error) {
+	if c.sszEnabled {
+		sb := &ethpb.SignedBuilderBidElectra{}
+		if err := sb.UnmarshalSSZ(data); err != nil {
+			return nil, errors.Wrap(err, "could not unmarshal SignedBuilderBidElectra SSZ")
+		}
+		return WrappedSignedBuilderBidElectra(sb)
+	}
+	hr := &ExecHeaderResponseElectra{}
+	if err := json.Unmarshal(data, hr); err != nil {
+		return nil, errors.Wrap(err, "could not unmarshal ExecHeaderResponseElectra JSON")
+	}
+	p, err := hr.ToProto()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not convert ExecHeaderResponseElectra to proto")
+	}
+	return WrappedSignedBuilderBidElectra(p)
+}
+
+func (c *Client) parseHeaderDeneb(data []byte) (SignedBid, error) {
+	if c.sszEnabled {
+		sb := &ethpb.SignedBuilderBidDeneb{}
+		if err := sb.UnmarshalSSZ(data); err != nil {
+			return nil, errors.Wrap(err, "could not unmarshal SignedBuilderBidDeneb SSZ")
+		}
+		return WrappedSignedBuilderBidDeneb(sb)
+	}
+	hr := &ExecHeaderResponseDeneb{}
+	if err := json.Unmarshal(data, hr); err != nil {
+		return nil, errors.Wrap(err, "could not unmarshal ExecHeaderResponseDeneb JSON")
+	}
+	p, err := hr.ToProto()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not convert ExecHeaderResponseDeneb to proto")
+	}
+	return WrappedSignedBuilderBidDeneb(p)
+}
+
+func (c *Client) parseHeaderCapella(data []byte) (SignedBid, error) {
+	if c.sszEnabled {
+		sb := &ethpb.SignedBuilderBidCapella{}
+		if err := sb.UnmarshalSSZ(data); err != nil {
+			return nil, errors.Wrap(err, "could not unmarshal SignedBuilderBidCapella SSZ")
+		}
+		return WrappedSignedBuilderBidCapella(sb)
+	}
+	hr := &ExecHeaderResponseCapella{}
+	if err := json.Unmarshal(data, hr); err != nil {
+		return nil, errors.Wrap(err, "could not unmarshal ExecHeaderResponseCapella JSON")
+	}
+	p, err := hr.ToProto()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not convert ExecHeaderResponseCapella to proto")
+	}
+	return WrappedSignedBuilderBidCapella(p)
+}
+
+func (c *Client) parseHeaderBellatrix(data []byte) (SignedBid, error) {
+	if c.sszEnabled {
+		sb := &ethpb.SignedBuilderBid{}
+		if err := sb.UnmarshalSSZ(data); err != nil {
+			return nil, errors.Wrap(err, "could not unmarshal SignedBuilderBid SSZ")
+		}
+		return WrappedSignedBuilderBid(sb)
+	}
+	hr := &ExecHeaderResponse{}
+	if err := json.Unmarshal(data, hr); err != nil {
+		return nil, errors.Wrap(err, "could not unmarshal ExecHeaderResponse JSON")
+	}
+	p, err := hr.ToProto()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not convert ExecHeaderResponse to proto")
+	}
+	return WrappedSignedBuilderBid(p)
 }

 // RegisterValidator encodes the SignedValidatorRegistrationV1 message to json (including hex-encoding the byte
@@ -288,70 +379,243 @@ func (c *Client) RegisterValidator(ctx context.Context, svr []*ethpb.SignedValid
 		tracing.AnnotateError(span, err)
 		return err
 	}
+
+	var (
+		body     []byte
+		err      error
+		postOpts reqOption
+	)
+	if c.sszEnabled {
+		postOpts = func(r *http.Request) {
+			r.Header.Set("Content-Type", api.OctetStreamMediaType)
+			r.Header.Set("Accept", api.OctetStreamMediaType)
+		}
+		body, err = sszValidatorRegisterRequest(svr)
+		if err != nil {
+			err := errors.Wrap(err, "error ssz encoding the SignedValidatorRegistration value body in RegisterValidator")
+			tracing.AnnotateError(span, err)
+			return err
+		}
+	} else {
+		postOpts = func(r *http.Request) {
+			r.Header.Set("Content-Type", api.JsonMediaType)
+			r.Header.Set("Accept", api.JsonMediaType)
+		}
+		body, err = jsonValidatorRegisterRequest(svr)
+		if err != nil {
+			err := errors.Wrap(err, "error json encoding the SignedValidatorRegistration value body in RegisterValidator")
+			tracing.AnnotateError(span, err)
+			return err
+		}
+	}
+
+	if _, _, err = c.do(ctx, http.MethodPost, postRegisterValidatorPath, bytes.NewBuffer(body), postOpts); err != nil {
+		return errors.Wrap(err, "do")
+	}
+	log.WithField("registrationCount", len(svr)).Debug("Successfully registered validator(s) on builder")
+	return nil
+}
+
+func jsonValidatorRegisterRequest(svr []*ethpb.SignedValidatorRegistrationV1) ([]byte, error) {
 	vs := make([]*structs.SignedValidatorRegistration, len(svr))
 	for i := 0; i < len(svr); i++ {
 		vs[i] = structs.SignedValidatorRegistrationFromConsensus(svr[i])
 	}
 	body, err := json.Marshal(vs)
 	if err != nil {
-		err := errors.Wrap(err, "error encoding the SignedValidatorRegistration value body in RegisterValidator")
-		tracing.AnnotateError(span, err)
-		return err
+		return nil, err
 	}
+	return body, nil
+}

-	_, err = c.do(ctx, http.MethodPost, postRegisterValidatorPath, bytes.NewBuffer(body))
-	if err != nil {
-		return err
+func sszValidatorRegisterRequest(svr []*ethpb.SignedValidatorRegistrationV1) ([]byte, error) {
+	if uint64(len(svr)) > params.BeaconConfig().ValidatorRegistryLimit {
+		return nil, errors.Wrap(errMalformedRequest, "validator registry limit exceeded")
 	}
-	log.WithField("registrationCount", len(svr)).Debug("Successfully registered validator(s) on builder")
-	return nil
+	ssz := make([]byte, vrSize*len(svr))
+	for i, vr := range svr {
+		sszrep, err := vr.MarshalSSZ()
+		if err != nil {
+			return nil, errors.Wrap(err, "failed to marshal validator registry ssz")
+		}
+		copy(ssz[i*vrSize:(i+1)*vrSize], sszrep)
+	}
+	return ssz, nil
 }

 var errResponseVersionMismatch = errors.New("builder API response uses a different version than requested in " + api.VersionHeader + " header")

+func getVersionsBlockToPayload(blockVersion int) (int, error) {
+	if blockVersion >= version.Deneb {
+		return version.Deneb, nil
+	}
+	if blockVersion == version.Capella {
+		return version.Capella, nil
+	}
+	if blockVersion == version.Bellatrix {
+		return version.Bellatrix, nil
+	}
+	return 0, errors.Wrapf(errVersionUnsupported, "block version %d", blockVersion)
+}
+
 // SubmitBlindedBlock calls the builder API endpoint that binds the validator to the builder and submits the block.
 // The response is the full execution payload used to create the blinded block.
 func (c *Client) SubmitBlindedBlock(ctx context.Context, sb interfaces.ReadOnlySignedBeaconBlock) (interfaces.ExecutionData, *v1.BlobsBundle, error) {
+	body, postOpts, err := c.buildBlindedBlockRequest(sb)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// 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)
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "error posting the blinded block to the builder api")
+	}
+
+	ver, err := c.checkBlockVersion(data, header)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	expectedPayloadVer, err := getVersionsBlockToPayload(sb.Version())
+	if err != nil {
+		return nil, nil, err
+	}
+	gotPayloadVer, err := getVersionsBlockToPayload(ver)
+	if err != nil {
+		return nil, nil, err
+	}
+	if expectedPayloadVer != gotPayloadVer {
+		return nil, nil, errors.Wrapf(errResponseVersionMismatch, "expected payload version %d, got %d", expectedPayloadVer, gotPayloadVer)
+	}
+
+	ed, blobs, err := c.parseBlindedBlockResponse(data, ver)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return ed, blobs, nil
+}
+
+func (c *Client) checkBlockVersion(respBytes []byte, header http.Header) (int, error) {
+	var versionHeader string
+	if c.sszEnabled {
+		versionHeader = strings.ToLower(header.Get(api.VersionHeader))
+	} else {
+		// fallback to JSON-based version extraction
+		v := &VersionResponse{}
+		if err := json.Unmarshal(respBytes, v); err != nil {
+			return 0, errors.Wrapf(err, "error unmarshaling JSON version fallback")
+		}
+		versionHeader = strings.ToLower(v.Version)
+	}
+
+	ver, err := version.FromString(versionHeader)
+	if err != nil {
+		return 0, errors.Wrapf(err, "unsupported header version %s", versionHeader)
+	}
+
+	return ver, nil
+}
+
+// Helper: build request body for SubmitBlindedBlock
+func (c *Client) buildBlindedBlockRequest(sb interfaces.ReadOnlySignedBeaconBlock) ([]byte, reqOption, error) {
 	if !sb.IsBlinded() {
 		return nil, nil, errNotBlinded
 	}

-	// massage the proto struct type data into the api response type.
+	if c.sszEnabled {
+		body, err := sb.MarshalSSZ()
+		if err != nil {
+			return nil, nil, errors.Wrap(err, "could not marshal SSZ for blinded block")
+		}
+		opt := func(r *http.Request) {
+			r.Header.Set(api.VersionHeader, version.String(sb.Version()))
+			r.Header.Set("Content-Type", api.OctetStreamMediaType)
+			r.Header.Set("Accept", api.OctetStreamMediaType)
+		}
+		return body, opt, nil
+	}
+
 	mj, err := structs.SignedBeaconBlockMessageJsoner(sb)
 	if err != nil {
 		return nil, nil, errors.Wrap(err, "error generating blinded beacon block post request")
 	}
-
 	body, err := json.Marshal(mj)
 	if err != nil {
-		return nil, nil, errors.Wrap(err, "error marshaling blinded block post request to json")
+		return nil, nil, errors.Wrap(err, "error marshaling blinded block to JSON")
 	}
-	postOpts := func(r *http.Request) {
-		r.Header.Add("Eth-Consensus-Version", version.String(sb.Version()))
+	opt := func(r *http.Request) {
+		r.Header.Set(api.VersionHeader, version.String(sb.Version()))
 		r.Header.Set("Content-Type", api.JsonMediaType)
 		r.Header.Set("Accept", api.JsonMediaType)
 	}
-	// post the blinded block - the execution payload response should contain the unblinded payload, along with the
-	// blobs bundle if it is post deneb.
-	rb, err := c.do(ctx, http.MethodPost, postBlindedBeaconBlockPath, bytes.NewBuffer(body), postOpts)
-	if err != nil {
-		return nil, nil, errors.Wrap(err, "error posting the blinded block to the builder api")
+	return body, opt, nil
+}
+
+// Helper: parse the response returned by SubmitBlindedBlock
+func (c *Client) parseBlindedBlockResponse(
+	respBytes []byte,
+	forkVersion int,
+) (interfaces.ExecutionData, *v1.BlobsBundle, error) {
+	if c.sszEnabled {
+		return c.parseBlindedBlockResponseSSZ(respBytes, forkVersion)
 	}
-	// ExecutionPayloadResponse parses just the outer container and the Value key, enabling it to use the .Value
-	// key to determine which underlying data type to use to finish the unmarshaling.
+	return c.parseBlindedBlockResponseJSON(respBytes, forkVersion)
+}
+
+func (c *Client) parseBlindedBlockResponseSSZ(
+	respBytes []byte,
+	forkVersion int,
+) (interfaces.ExecutionData, *v1.BlobsBundle, error) {
+	if forkVersion >= version.Deneb {
+		payloadAndBlobs := &v1.ExecutionPayloadDenebAndBlobsBundle{}
+		if err := payloadAndBlobs.UnmarshalSSZ(respBytes); err != nil {
+			return nil, nil, errors.Wrap(err, "unable to unmarshal ExecutionPayloadDenebAndBlobsBundle SSZ")
+		}
+		ed, err := blocks.NewWrappedExecutionData(payloadAndBlobs.Payload)
+		if err != nil {
+			return nil, nil, errors.Wrapf(err, "unable to wrap execution data for %s", version.String(forkVersion))
+		}
+		return ed, payloadAndBlobs.BlobsBundle, nil
+	} else if forkVersion >= version.Capella {
+		payload := &v1.ExecutionPayloadCapella{}
+		if err := payload.UnmarshalSSZ(respBytes); err != nil {
+			return nil, nil, errors.Wrap(err, "unable to unmarshal ExecutionPayloadCapella SSZ")
+		}
+		ed, err := blocks.NewWrappedExecutionData(payload)
+		if err != nil {
+			return nil, nil, errors.Wrapf(err, "unable to wrap execution data for %s", version.String(forkVersion))
+		}
+		return ed, nil, nil
+	} else if forkVersion >= version.Bellatrix {
+		payload := &v1.ExecutionPayload{}
+		if err := payload.UnmarshalSSZ(respBytes); err != nil {
+			return nil, nil, errors.Wrap(err, "unable to unmarshal ExecutionPayload SSZ")
+		}
+		ed, err := blocks.NewWrappedExecutionData(payload)
+		if err != nil {
+			return nil, nil, errors.Wrapf(err, "unable to wrap execution data for %s", version.String(forkVersion))
+		}
+		return ed, nil, nil
+	} else {
+		return nil, nil, fmt.Errorf("unsupported header version %s", version.String(forkVersion))
+	}
+}
+
+func (c *Client) parseBlindedBlockResponseJSON(
+	respBytes []byte,
+	forkVersion int,
+) (interfaces.ExecutionData, *v1.BlobsBundle, error) {
 	ep := &ExecutionPayloadResponse{}
-	if err := json.Unmarshal(rb, ep); err != nil {
-		return nil, nil, errors.Wrap(err, "error unmarshaling the builder ExecutionPayloadResponse")
+	if err := json.Unmarshal(respBytes, ep); err != nil {
+		return nil, nil, errors.Wrap(err, "error unmarshaling ExecutionPayloadResponse")
 	}
-	if strings.ToLower(ep.Version) != version.String(sb.Version()) {
-		return nil, nil, errors.Wrapf(errResponseVersionMismatch, "req=%s, recv=%s", strings.ToLower(ep.Version), version.String(sb.Version()))
-	}
-	// This parses the rest of the response and returns the inner data field.
 	pp, err := ep.ParsePayload()
 	if err != nil {
-		return nil, nil, errors.Wrapf(err, "failed to parse execution payload from builder with version=%s", ep.Version)
+		return nil, nil, errors.Wrapf(err, "failed to parse payload with version=%s", ep.Version)
 	}
-	// Get the payload as a proto.Message so it can be wrapped as an execution payload interface.
 	pb, err := pp.PayloadProto()
 	if err != nil {
 		return nil, nil, err
@@ -360,11 +624,13 @@ func (c *Client) SubmitBlindedBlock(ctx context.Context, sb interfaces.ReadOnlyS
 	if err != nil {
 		return nil, nil, err
 	}
+
+	// Check if it contains blobs
 	bb, ok := pp.(BlobBundler)
 	if ok {
 		bbpb, err := bb.BundleProto()
 		if err != nil {
-			return nil, nil, errors.Wrapf(err, "failed to extract blobs bundle from builder response with version=%s", ep.Version)
+			return nil, nil, errors.Wrapf(err, "failed to extract blobs bundle from version=%s", ep.Version)
 		}
 		return ed, bbpb, nil
 	}
@@ -375,7 +641,10 @@ func (c *Client) SubmitBlindedBlock(ctx context.Context, sb interfaces.ReadOnlyS
 // response, and an error response may have an error message. This method will return a nil value for error in the
 // happy path, and an error with information about the server response body for a non-200 response.
 func (c *Client) Status(ctx context.Context) error {
-	_, err := c.do(ctx, http.MethodGet, getStatus, nil)
+	getOpts := func(r *http.Request) {
+		r.Header.Set("Accept", api.JsonMediaType)
+	}
+	_, _, err := c.do(ctx, http.MethodGet, getStatus, nil, getOpts)
 	return err
 }

@@ -390,6 +659,18 @@ func non200Err(response *http.Response) error {
 	}
 	msg := fmt.Sprintf("code=%d, url=%s, body=%s", response.StatusCode, response.Request.URL, body)
 	switch response.StatusCode {
+	case http.StatusUnsupportedMediaType:
+		log.WithError(ErrUnsupportedMediaType).Debug(msg)
+		if jsonErr := json.Unmarshal(bodyBytes, &errMessage); jsonErr != nil {
+			return errors.Wrap(jsonErr, "unable to read response body")
+		}
+		return errors.Wrap(ErrUnsupportedMediaType, errMessage.Message)
+	case http.StatusNotAcceptable:
+		log.WithError(ErrNotAcceptable).Debug(msg)
+		if jsonErr := json.Unmarshal(bodyBytes, &errMessage); jsonErr != nil {
+			return errors.Wrap(jsonErr, "unable to read response body")
+		}
+		return errors.Wrap(ErrNotAcceptable, errMessage.Message)
 	case http.StatusNoContent:
 		log.WithError(ErrNoContent).Debug(msg)
 		return ErrNoContent
--- a/api/client/builder/client_test.go
+++ b/api/client/builder/client_test.go
@@ -8,7 +8,6 @@ import (
 	"io"
 	"net/http"
 	"net/url"
-	"strconv"
 	"testing"

 	"github.com/prysmaticlabs/go-bitfield"
@@ -88,39 +87,84 @@ func TestClient_RegisterValidator(t *testing.T) {
 	ctx := context.Background()
 	expectedBody := `[{"message":{"fee_recipient":"0x0000000000000000000000000000000000000000","gas_limit":"23","timestamp":"42","pubkey":"0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a"},"signature":"0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"}]`
 	expectedPath := "/eth/v1/builder/validators"
-	hc := &http.Client{
-		Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
-			require.Equal(t, api.JsonMediaType, r.Header.Get("Content-Type"))
-			require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
-			body, err := io.ReadAll(r.Body)
-			defer func() {
-				require.NoError(t, r.Body.Close())
-			}()
-			require.NoError(t, err)
-			require.Equal(t, expectedBody, string(body))
-			require.Equal(t, expectedPath, r.URL.Path)
-			require.Equal(t, http.MethodPost, r.Method)
-			return &http.Response{
-				StatusCode: http.StatusOK,
-				Body:       io.NopCloser(bytes.NewBuffer(nil)),
-				Request:    r.Clone(ctx),
-			}, nil
-		}),
-	}
-	c := &Client{
-		hc:      hc,
-		baseURL: &url.URL{Host: "localhost:3500", Scheme: "http"},
-	}
-	reg := &eth.SignedValidatorRegistrationV1{
-		Message: &eth.ValidatorRegistrationV1{
-			FeeRecipient: ezDecode(t, params.BeaconConfig().EthBurnAddressHex),
-			GasLimit:     23,
-			Timestamp:    42,
-			Pubkey:       ezDecode(t, "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a"),
-		},
-		Signature: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
-	}
-	require.NoError(t, c.RegisterValidator(ctx, []*eth.SignedValidatorRegistrationV1{reg}))
+	t.Run("JSON success", func(t *testing.T) {
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Content-Type"))
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
+				body, err := io.ReadAll(r.Body)
+				defer func() {
+					require.NoError(t, r.Body.Close())
+				}()
+				require.NoError(t, err)
+				require.Equal(t, expectedBody, string(body))
+				require.Equal(t, expectedPath, r.URL.Path)
+				require.Equal(t, http.MethodPost, r.Method)
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Body:       io.NopCloser(bytes.NewBuffer(nil)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:      hc,
+			baseURL: &url.URL{Host: "localhost:3500", Scheme: "http"},
+		}
+		reg := &eth.SignedValidatorRegistrationV1{
+			Message: &eth.ValidatorRegistrationV1{
+				FeeRecipient: ezDecode(t, params.BeaconConfig().EthBurnAddressHex),
+				GasLimit:     23,
+				Timestamp:    42,
+				Pubkey:       ezDecode(t, "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a"),
+			},
+			Signature: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+		}
+		require.NoError(t, c.RegisterValidator(ctx, []*eth.SignedValidatorRegistrationV1{reg}))
+	})
+	t.Run("SSZ success", func(t *testing.T) {
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Content-Type"))
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+				body, err := io.ReadAll(r.Body)
+				defer func() {
+					require.NoError(t, r.Body.Close())
+				}()
+				require.NoError(t, err)
+				request := &eth.SignedValidatorRegistrationV1{}
+				itemBytes := body[:request.SizeSSZ()]
+				require.NoError(t, request.UnmarshalSSZ(itemBytes))
+				jsRequest := structs.SignedValidatorRegistrationFromConsensus(request)
+				js, err := json.Marshal([]*structs.SignedValidatorRegistration{jsRequest})
+				require.NoError(t, err)
+
+				require.Equal(t, expectedBody, string(js))
+				require.Equal(t, expectedPath, r.URL.Path)
+				require.Equal(t, http.MethodPost, r.Method)
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Body:       io.NopCloser(bytes.NewBuffer(nil)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:         hc,
+			baseURL:    &url.URL{Host: "localhost:3500", Scheme: "http"},
+			sszEnabled: true,
+		}
+		reg := &eth.SignedValidatorRegistrationV1{
+			Message: &eth.ValidatorRegistrationV1{
+				FeeRecipient: ezDecode(t, params.BeaconConfig().EthBurnAddressHex),
+				GasLimit:     23,
+				Timestamp:    42,
+				Pubkey:       ezDecode(t, "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a"),
+			},
+			Signature: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+		}
+		require.NoError(t, c.RegisterValidator(ctx, []*eth.SignedValidatorRegistrationV1{reg}))
+	})
 }

 func TestClient_GetHeader(t *testing.T) {
@@ -176,6 +220,7 @@ func TestClient_GetHeader(t *testing.T) {
 		hc := &http.Client{
 			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
 				require.Equal(t, expectedPath, r.URL.Path)
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
 				return &http.Response{
 					StatusCode: http.StatusOK,
 					Body:       io.NopCloser(bytes.NewBufferString(testExampleHeaderResponse)),
@@ -207,9 +252,56 @@ func TestClient_GetHeader(t *testing.T) {
 		require.Equal(t, 0, value.Int.Cmp(primitives.WeiToBigInt(bid.Value())))
 		require.Equal(t, bidStr, primitives.WeiToBigInt(bid.Value()).String())
 	})
+	t.Run("bellatrix ssz", func(t *testing.T) {
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+				require.Equal(t, expectedPath, r.URL.Path)
+				epr := &ExecHeaderResponse{}
+				require.NoError(t, json.Unmarshal([]byte(testExampleHeaderResponse), epr))
+				pro, err := epr.ToProto()
+				require.NoError(t, err)
+				ssz, err := pro.MarshalSSZ()
+				require.NoError(t, err)
+				header := http.Header{}
+				header.Set(api.VersionHeader, "bellatrix")
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     header,
+					Body:       io.NopCloser(bytes.NewBuffer(ssz)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:         hc,
+			baseURL:    &url.URL{Host: "localhost:3500", Scheme: "http"},
+			sszEnabled: true,
+		}
+		h, err := c.GetHeader(ctx, slot, bytesutil.ToBytes32(parentHash), bytesutil.ToBytes48(pubkey))
+		require.NoError(t, err)
+		expectedSig := ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505")
+		require.Equal(t, true, bytes.Equal(expectedSig, h.Signature()))
+		expectedTxRoot := ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")
+		bid, err := h.Message()
+		require.NoError(t, err)
+		bidHeader, err := bid.Header()
+		require.NoError(t, err)
+		withdrawalsRoot, err := bidHeader.TransactionsRoot()
+		require.NoError(t, err)
+		require.Equal(t, true, bytes.Equal(expectedTxRoot, withdrawalsRoot))
+		require.Equal(t, uint64(1), bidHeader.GasUsed())
+		// this matches the value in the testExampleHeaderResponse
+		bidStr := "652312848583266388373324160190187140051835877600158453279131187530910662656"
+		value, err := stringToUint256(bidStr)
+		require.NoError(t, err)
+		require.Equal(t, 0, value.Int.Cmp(primitives.WeiToBigInt(bid.Value())))
+		require.Equal(t, bidStr, primitives.WeiToBigInt(bid.Value()).String())
+	})
 	t.Run("capella", func(t *testing.T) {
 		hc := &http.Client{
 			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
 				require.Equal(t, expectedPath, r.URL.Path)
 				return &http.Response{
 					StatusCode: http.StatusOK,
@@ -238,9 +330,52 @@ func TestClient_GetHeader(t *testing.T) {
 		require.Equal(t, 0, value.Int.Cmp(primitives.WeiToBigInt(bid.Value())))
 		require.Equal(t, bidStr, primitives.WeiToBigInt(bid.Value()).String())
 	})
+	t.Run("capella ssz", func(t *testing.T) {
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+				require.Equal(t, expectedPath, r.URL.Path)
+				epr := &ExecHeaderResponseCapella{}
+				require.NoError(t, json.Unmarshal([]byte(testExampleHeaderResponseCapella), epr))
+				pro, err := epr.ToProto()
+				require.NoError(t, err)
+				ssz, err := pro.MarshalSSZ()
+				require.NoError(t, err)
+				header := http.Header{}
+				header.Set(api.VersionHeader, "capella")
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     header,
+					Body:       io.NopCloser(bytes.NewBuffer(ssz)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:         hc,
+			baseURL:    &url.URL{Host: "localhost:3500", Scheme: "http"},
+			sszEnabled: true,
+		}
+		h, err := c.GetHeader(ctx, slot, bytesutil.ToBytes32(parentHash), bytesutil.ToBytes48(pubkey))
+		require.NoError(t, err)
+		expectedWithdrawalsRoot := ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")
+		bid, err := h.Message()
+		require.NoError(t, err)
+		bidHeader, err := bid.Header()
+		require.NoError(t, err)
+		withdrawalsRoot, err := bidHeader.WithdrawalsRoot()
+		require.NoError(t, err)
+		require.Equal(t, true, bytes.Equal(expectedWithdrawalsRoot, withdrawalsRoot))
+		bidStr := "652312848583266388373324160190187140051835877600158453279131187530910662656"
+		value, err := stringToUint256(bidStr)
+		require.NoError(t, err)
+		require.Equal(t, 0, value.Int.Cmp(primitives.WeiToBigInt(bid.Value())))
+		require.Equal(t, bidStr, primitives.WeiToBigInt(bid.Value()).String())
+	})
 	t.Run("deneb", func(t *testing.T) {
 		hc := &http.Client{
 			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
 				require.Equal(t, expectedPath, r.URL.Path)
 				return &http.Response{
 					StatusCode: http.StatusOK,
@@ -277,6 +412,56 @@ func TestClient_GetHeader(t *testing.T) {
 			require.Equal(t, len(kcgCommitments[i]) == 48, true)
 		}
 	})
+	t.Run("deneb ssz", func(t *testing.T) {
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+				require.Equal(t, expectedPath, r.URL.Path)
+				epr := &ExecHeaderResponseDeneb{}
+				require.NoError(t, json.Unmarshal([]byte(testExampleHeaderResponseDeneb), epr))
+				pro, err := epr.ToProto()
+				require.NoError(t, err)
+				ssz, err := pro.MarshalSSZ()
+				require.NoError(t, err)
+				header := http.Header{}
+				header.Set(api.VersionHeader, "deneb")
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     header,
+					Body:       io.NopCloser(bytes.NewBuffer(ssz)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:         hc,
+			baseURL:    &url.URL{Host: "localhost:3500", Scheme: "http"},
+			sszEnabled: true,
+		}
+		h, err := c.GetHeader(ctx, slot, bytesutil.ToBytes32(parentHash), bytesutil.ToBytes48(pubkey))
+		require.NoError(t, err)
+		expectedWithdrawalsRoot := ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")
+		bid, err := h.Message()
+		require.NoError(t, err)
+		bidHeader, err := bid.Header()
+		require.NoError(t, err)
+		withdrawalsRoot, err := bidHeader.WithdrawalsRoot()
+		require.NoError(t, err)
+		require.Equal(t, true, bytes.Equal(expectedWithdrawalsRoot, withdrawalsRoot))
+
+		bidStr := "652312848583266388373324160190187140051835877600158453279131187530910662656"
+		value, err := stringToUint256(bidStr)
+		require.NoError(t, err)
+		require.Equal(t, 0, value.Int.Cmp(primitives.WeiToBigInt(bid.Value())))
+		require.Equal(t, bidStr, primitives.WeiToBigInt(bid.Value()).String())
+		dbid, ok := bid.(builderBidDeneb)
+		require.Equal(t, true, ok)
+		kcgCommitments := dbid.BlobKzgCommitments()
+		require.Equal(t, len(kcgCommitments) > 0, true)
+		for i := range kcgCommitments {
+			require.Equal(t, len(kcgCommitments[i]) == 48, true)
+		}
+	})
 	t.Run("deneb, too many kzg commitments", func(t *testing.T) {
 		hc := &http.Client{
 			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
@@ -293,11 +478,12 @@ func TestClient_GetHeader(t *testing.T) {
 			baseURL: &url.URL{Host: "localhost:3500", Scheme: "http"},
 		}
 		_, err := c.GetHeader(ctx, slot, bytesutil.ToBytes32(parentHash), bytesutil.ToBytes48(pubkey))
-		require.ErrorContains(t, "could not extract proto message from header: too many blob commitments: 7", err)
+		require.ErrorContains(t, "could not convert ExecHeaderResponseDeneb to proto: too many blob commitments: 7", err)
 	})
 	t.Run("electra", func(t *testing.T) {
 		hc := &http.Client{
 			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
 				require.Equal(t, expectedPath, r.URL.Path)
 				return &http.Response{
 					StatusCode: http.StatusOK,
@@ -338,6 +524,61 @@ func TestClient_GetHeader(t *testing.T) {
 		require.Equal(t, 1, len(requests.Withdrawals))
 		require.Equal(t, 1, len(requests.Consolidations))

+	})
+	t.Run("electra ssz", func(t *testing.T) {
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+				require.Equal(t, expectedPath, r.URL.Path)
+				epr := &ExecHeaderResponseElectra{}
+				require.NoError(t, json.Unmarshal([]byte(testExampleHeaderResponseElectra), epr))
+				pro, err := epr.ToProto()
+				require.NoError(t, err)
+				ssz, err := pro.MarshalSSZ()
+				require.NoError(t, err)
+				header := http.Header{}
+				header.Set(api.VersionHeader, "electra")
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     header,
+					Body:       io.NopCloser(bytes.NewBuffer(ssz)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:         hc,
+			baseURL:    &url.URL{Host: "localhost:3500", Scheme: "http"},
+			sszEnabled: true,
+		}
+		h, err := c.GetHeader(ctx, slot, bytesutil.ToBytes32(parentHash), bytesutil.ToBytes48(pubkey))
+		require.NoError(t, err)
+		expectedWithdrawalsRoot := ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")
+		bid, err := h.Message()
+		require.NoError(t, err)
+		bidHeader, err := bid.Header()
+		require.NoError(t, err)
+		withdrawalsRoot, err := bidHeader.WithdrawalsRoot()
+		require.NoError(t, err)
+		require.Equal(t, true, bytes.Equal(expectedWithdrawalsRoot, withdrawalsRoot))
+
+		bidStr := "652312848583266388373324160190187140051835877600158453279131187530910662656"
+		value, err := stringToUint256(bidStr)
+		require.NoError(t, err)
+		require.Equal(t, 0, value.Int.Cmp(primitives.WeiToBigInt(bid.Value())))
+		require.Equal(t, bidStr, primitives.WeiToBigInt(bid.Value()).String())
+		ebid, ok := bid.(builderBidElectra)
+		require.Equal(t, true, ok)
+		kcgCommitments := ebid.BlobKzgCommitments()
+		require.Equal(t, len(kcgCommitments) > 0, true)
+		for i := range kcgCommitments {
+			require.Equal(t, len(kcgCommitments[i]) == 48, true)
+		}
+		requests := ebid.ExecutionRequests()
+		require.Equal(t, 1, len(requests.Deposits))
+		require.Equal(t, 1, len(requests.Withdrawals))
+		require.Equal(t, 1, len(requests.Consolidations))
+
 	})
 	t.Run("unsupported version", func(t *testing.T) {
 		hc := &http.Client{
@@ -390,11 +631,51 @@ func TestSubmitBlindedBlock(t *testing.T) {
 		require.Equal(t, fmt.Sprintf("%#x", bfpg.SSZBytes()), fmt.Sprintf("%#x", ep.BaseFeePerGas()))
 		require.Equal(t, uint64(1), ep.GasLimit())
 	})
+	t.Run("bellatrix 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"))
+				epr := &ExecutionPayloadResponse{}
+				require.NoError(t, json.Unmarshal([]byte(testExampleExecutionPayload), epr))
+				ep := &ExecutionPayload{}
+				require.NoError(t, json.Unmarshal(epr.Data, ep))
+				pro, err := ep.ToProto()
+				require.NoError(t, err)
+				ssz, err := pro.MarshalSSZ()
+				require.NoError(t, err)
+				header := http.Header{}
+				header.Set(api.VersionHeader, "bellatrix")
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     header,
+					Body:       io.NopCloser(bytes.NewBuffer(ssz)),
+					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)
+		ep, _, err := c.SubmitBlindedBlock(ctx, sbbb)
+		require.NoError(t, err)
+		require.Equal(t, true, bytes.Equal(ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"), ep.ParentHash()))
+		bfpg, err := stringToUint256("452312848583266388373324160190187140051835877600158453279131187530910662656")
+		require.NoError(t, err)
+		require.Equal(t, fmt.Sprintf("%#x", bfpg.SSZBytes()), fmt.Sprintf("%#x", ep.BaseFeePerGas()))
+		require.Equal(t, uint64(1), ep.GasLimit())
+	})
 	t.Run("capella", 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, "capella", r.Header.Get("Eth-Consensus-Version"))
+				require.Equal(t, "capella", r.Header.Get(api.VersionHeader))
 				require.Equal(t, api.JsonMediaType, r.Header.Get("Content-Type"))
 				require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
 				return &http.Response{
@@ -420,12 +701,54 @@ func TestSubmitBlindedBlock(t *testing.T) {
 		assert.DeepEqual(t, ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943"), withdrawals[0].Address)
 		assert.Equal(t, uint64(1), withdrawals[0].Amount)
 	})
+	t.Run("capella 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, "capella", r.Header.Get(api.VersionHeader))
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Content-Type"))
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+				epr := &ExecutionPayloadResponse{}
+				require.NoError(t, json.Unmarshal([]byte(testExampleExecutionPayloadCapella), epr))
+				ep := &ExecutionPayloadCapella{}
+				require.NoError(t, json.Unmarshal(epr.Data, ep))
+				pro, err := ep.ToProto()
+				require.NoError(t, err)
+				ssz, err := pro.MarshalSSZ()
+				require.NoError(t, err)
+				header := http.Header{}
+				header.Set(api.VersionHeader, "capella")
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     header,
+					Body:       io.NopCloser(bytes.NewBuffer(ssz)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:         hc,
+			baseURL:    &url.URL{Host: "localhost:3500", Scheme: "http"},
+			sszEnabled: true,
+		}
+		sbb, err := blocks.NewSignedBeaconBlock(testSignedBlindedBeaconBlockCapella(t))
+		require.NoError(t, err)
+		ep, _, err := c.SubmitBlindedBlock(ctx, sbb)
+		require.NoError(t, err)
+		withdrawals, err := ep.Withdrawals()
+		require.NoError(t, err)
+		require.Equal(t, 1, len(withdrawals))
+		assert.Equal(t, uint64(1), withdrawals[0].Index)
+		assert.Equal(t, primitives.ValidatorIndex(1), withdrawals[0].ValidatorIndex)
+		assert.DeepEqual(t, ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943"), withdrawals[0].Address)
+		assert.Equal(t, uint64(1), withdrawals[0].Amount)
+	})
 	t.Run("deneb", func(t *testing.T) {
 		test := testSignedBlindedBeaconBlockDeneb(t)
 		hc := &http.Client{
 			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
 				require.Equal(t, postBlindedBeaconBlockPath, r.URL.Path)
-				require.Equal(t, "deneb", r.Header.Get("Eth-Consensus-Version"))
+				require.Equal(t, "deneb", r.Header.Get(api.VersionHeader))
 				require.Equal(t, api.JsonMediaType, r.Header.Get("Content-Type"))
 				require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
 				var req structs.SignedBlindedBeaconBlockDeneb
@@ -460,6 +783,140 @@ func TestSubmitBlindedBlock(t *testing.T) {
 		assert.Equal(t, uint64(1), withdrawals[0].Amount)
 		require.NotNil(t, blobBundle)
 	})
+	t.Run("deneb ssz", func(t *testing.T) {
+		test := testSignedBlindedBeaconBlockDeneb(t)
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, postBlindedBeaconBlockPath, r.URL.Path)
+				require.Equal(t, "deneb", r.Header.Get(api.VersionHeader))
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Content-Type"))
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+				epr := &ExecPayloadResponseDeneb{}
+				require.NoError(t, json.Unmarshal([]byte(testExampleExecutionPayloadDeneb), epr))
+				pro, blob, err := epr.ToProto()
+				require.NoError(t, err)
+				combined := &v1.ExecutionPayloadDenebAndBlobsBundle{
+					Payload:     pro,
+					BlobsBundle: blob,
+				}
+				ssz, err := combined.MarshalSSZ()
+				require.NoError(t, err)
+				header := http.Header{}
+				header.Set(api.VersionHeader, "deneb")
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     header,
+					Body:       io.NopCloser(bytes.NewBuffer(ssz)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:         hc,
+			baseURL:    &url.URL{Host: "localhost:3500", Scheme: "http"},
+			sszEnabled: true,
+		}
+		sbb, err := blocks.NewSignedBeaconBlock(test)
+		require.NoError(t, err)
+
+		ep, blobBundle, err := c.SubmitBlindedBlock(ctx, sbb)
+		require.NoError(t, err)
+		withdrawals, err := ep.Withdrawals()
+		require.NoError(t, err)
+		require.Equal(t, 1, len(withdrawals))
+		assert.Equal(t, uint64(1), withdrawals[0].Index)
+		assert.Equal(t, primitives.ValidatorIndex(1), withdrawals[0].ValidatorIndex)
+		assert.DeepEqual(t, ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943"), withdrawals[0].Address)
+		assert.Equal(t, uint64(1), withdrawals[0].Amount)
+		require.NotNil(t, blobBundle)
+	})
+	t.Run("electra", func(t *testing.T) {
+		test := testSignedBlindedBeaconBlockElectra(t)
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, postBlindedBeaconBlockPath, r.URL.Path)
+				require.Equal(t, "electra", r.Header.Get(api.VersionHeader))
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Content-Type"))
+				require.Equal(t, api.JsonMediaType, r.Header.Get("Accept"))
+				var req structs.SignedBlindedBeaconBlockElectra
+				err := json.NewDecoder(r.Body).Decode(&req)
+				require.NoError(t, err)
+				block, err := req.ToConsensus()
+				require.NoError(t, err)
+				require.DeepEqual(t, block, test)
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Body:       io.NopCloser(bytes.NewBufferString(testExampleExecutionPayloadDeneb)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:      hc,
+			baseURL: &url.URL{Host: "localhost:3500", Scheme: "http"},
+		}
+
+		sbb, err := blocks.NewSignedBeaconBlock(test)
+		require.NoError(t, err)
+
+		ep, blobBundle, err := c.SubmitBlindedBlock(ctx, sbb)
+		require.NoError(t, err)
+		withdrawals, err := ep.Withdrawals()
+		require.NoError(t, err)
+		require.Equal(t, 1, len(withdrawals))
+		assert.Equal(t, uint64(1), withdrawals[0].Index)
+		assert.Equal(t, primitives.ValidatorIndex(1), withdrawals[0].ValidatorIndex)
+		assert.DeepEqual(t, ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943"), withdrawals[0].Address)
+		assert.Equal(t, uint64(1), withdrawals[0].Amount)
+		require.NotNil(t, blobBundle)
+	})
+	t.Run("electra ssz", func(t *testing.T) {
+		test := testSignedBlindedBeaconBlockElectra(t)
+		hc := &http.Client{
+			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
+				require.Equal(t, postBlindedBeaconBlockPath, r.URL.Path)
+				require.Equal(t, "electra", r.Header.Get(api.VersionHeader))
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Content-Type"))
+				require.Equal(t, api.OctetStreamMediaType, r.Header.Get("Accept"))
+				epr := &ExecPayloadResponseDeneb{}
+				require.NoError(t, json.Unmarshal([]byte(testExampleExecutionPayloadDeneb), epr))
+				pro, blob, err := epr.ToProto()
+				require.NoError(t, err)
+				combined := &v1.ExecutionPayloadDenebAndBlobsBundle{
+					Payload:     pro,
+					BlobsBundle: blob,
+				}
+				ssz, err := combined.MarshalSSZ()
+				require.NoError(t, err)
+				header := http.Header{}
+				header.Set(api.VersionHeader, "electra")
+				return &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     header,
+					Body:       io.NopCloser(bytes.NewBuffer(ssz)),
+					Request:    r.Clone(ctx),
+				}, nil
+			}),
+		}
+		c := &Client{
+			hc:         hc,
+			baseURL:    &url.URL{Host: "localhost:3500", Scheme: "http"},
+			sszEnabled: true,
+		}
+		sbb, err := blocks.NewSignedBeaconBlock(test)
+		require.NoError(t, err)
+
+		ep, blobBundle, err := c.SubmitBlindedBlock(ctx, sbb)
+		require.NoError(t, err)
+		withdrawals, err := ep.Withdrawals()
+		require.NoError(t, err)
+		require.Equal(t, 1, len(withdrawals))
+		assert.Equal(t, uint64(1), withdrawals[0].Index)
+		assert.Equal(t, primitives.ValidatorIndex(1), withdrawals[0].ValidatorIndex)
+		assert.DeepEqual(t, ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943"), withdrawals[0].Address)
+		assert.Equal(t, uint64(1), withdrawals[0].Amount)
+		require.NotNil(t, blobBundle)
+	})
 	t.Run("mismatched versions, expected bellatrix got capella", func(t *testing.T) {
 		hc := &http.Client{
 			Transport: roundtrip(func(r *http.Request) (*http.Response, error) {
@@ -586,7 +1043,13 @@ func testSignedBlindedBeaconBlockBellatrix(t *testing.T) *eth.SignedBlindedBeaco
 				},
 				Deposits: []*eth.Deposit{
 					{
-						Proof: [][]byte{ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")},
+						Proof: func() [][]byte {
+							b := make([][]byte, 33)
+							for i := range b {
+								b[i] = ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")
+							}
+							return b
+						}(),
 						Data: &eth.Deposit_Data{
 							PublicKey:             ezDecode(t, "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a"),
 							WithdrawalCredentials: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
@@ -605,8 +1068,8 @@ func testSignedBlindedBeaconBlockBellatrix(t *testing.T) *eth.SignedBlindedBeaco
 					},
 				},
 				SyncAggregate: &eth.SyncAggregate{
-					SyncCommitteeSignature: make([]byte, 48),
-					SyncCommitteeBits:      bitfield.Bitvector512{0x01},
+					SyncCommitteeSignature: make([]byte, 96),
+					SyncCommitteeBits:      make(bitfield.Bitvector512, 64),
 				},
 				ExecutionPayloadHeader: &v1.ExecutionPayloadHeader{
 					ParentHash:       ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
@@ -620,7 +1083,7 @@ func testSignedBlindedBeaconBlockBellatrix(t *testing.T) *eth.SignedBlindedBeaco
 					GasUsed:          1,
 					Timestamp:        1,
 					ExtraData:        ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
-					BaseFeePerGas:    []byte(strconv.FormatUint(1, 10)),
+					BaseFeePerGas:    ezDecode(t, "0x4523128485832663883733241601901871400518358776001584532791311875"),
 					BlockHash:        ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
 					TransactionsRoot: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
 				},
@@ -728,7 +1191,13 @@ func testSignedBlindedBeaconBlockCapella(t *testing.T) *eth.SignedBlindedBeaconB
 				},
 				Deposits: []*eth.Deposit{
 					{
-						Proof: [][]byte{ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")},
+						Proof: func() [][]byte {
+							b := make([][]byte, 33)
+							for i := range b {
+								b[i] = ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")
+							}
+							return b
+						}(),
 						Data: &eth.Deposit_Data{
 							PublicKey:             ezDecode(t, "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a"),
 							WithdrawalCredentials: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
@@ -747,8 +1216,8 @@ func testSignedBlindedBeaconBlockCapella(t *testing.T) *eth.SignedBlindedBeaconB
 					},
 				},
 				SyncAggregate: &eth.SyncAggregate{
-					SyncCommitteeSignature: make([]byte, 48),
-					SyncCommitteeBits:      bitfield.Bitvector512{0x01},
+					SyncCommitteeSignature: make([]byte, 96),
+					SyncCommitteeBits:      make(bitfield.Bitvector512, 64),
 				},
 				ExecutionPayloadHeader: &v1.ExecutionPayloadHeaderCapella{
 					ParentHash:       ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
@@ -762,7 +1231,7 @@ func testSignedBlindedBeaconBlockCapella(t *testing.T) *eth.SignedBlindedBeaconB
 					GasUsed:          1,
 					Timestamp:        1,
 					ExtraData:        ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
-					BaseFeePerGas:    []byte(strconv.FormatUint(1, 10)),
+					BaseFeePerGas:    ezDecode(t, "0x4523128485832663883733241601901871400518358776001584532791311875"),
 					BlockHash:        ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
 					TransactionsRoot: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
 					WithdrawalsRoot:  ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
@@ -875,7 +1344,13 @@ func testSignedBlindedBeaconBlockDeneb(t *testing.T) *eth.SignedBlindedBeaconBlo
 				},
 				Deposits: []*eth.Deposit{
 					{
-						Proof: [][]byte{ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")},
+						Proof: func() [][]byte {
+							b := make([][]byte, 33)
+							for i := range b {
+								b[i] = ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")
+							}
+							return b
+						}(),
 						Data: &eth.Deposit_Data{
 							PublicKey:             ezDecode(t, "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a"),
 							WithdrawalCredentials: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
@@ -922,6 +1397,163 @@ func testSignedBlindedBeaconBlockDeneb(t *testing.T) *eth.SignedBlindedBeaconBlo
 	}
 }

+func testSignedBlindedBeaconBlockElectra(t *testing.T) *eth.SignedBlindedBeaconBlockElectra {
+	basebytes, err := bytesutil.Uint256ToSSZBytes("14074904626401341155369551180448584754667373453244490859944217516317499064576")
+	if err != nil {
+		log.Error(err)
+	}
+	return &eth.SignedBlindedBeaconBlockElectra{
+		Message: &eth.BlindedBeaconBlockElectra{
+			Slot:          1,
+			ProposerIndex: 1,
+			ParentRoot:    ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+			StateRoot:     ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+			Body: &eth.BlindedBeaconBlockBodyElectra{
+				RandaoReveal: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+				Eth1Data: &eth.Eth1Data{
+					DepositRoot:  ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+					DepositCount: 1,
+					BlockHash:    ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+				},
+				Graffiti: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+				ProposerSlashings: []*eth.ProposerSlashing{
+					{
+						Header_1: &eth.SignedBeaconBlockHeader{
+							Header: &eth.BeaconBlockHeader{
+								Slot:          1,
+								ProposerIndex: 1,
+								ParentRoot:    ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								StateRoot:     ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								BodyRoot:      ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+							},
+							Signature: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+						},
+						Header_2: &eth.SignedBeaconBlockHeader{
+							Header: &eth.BeaconBlockHeader{
+								Slot:          1,
+								ProposerIndex: 1,
+								ParentRoot:    ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								StateRoot:     ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								BodyRoot:      ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+							},
+							Signature: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+						},
+					},
+				},
+				AttesterSlashings: []*eth.AttesterSlashingElectra{
+					{
+						Attestation_1: &eth.IndexedAttestationElectra{
+							AttestingIndices: []uint64{1},
+							Data: &eth.AttestationData{
+								Slot:            1,
+								CommitteeIndex:  1,
+								BeaconBlockRoot: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								Source: &eth.Checkpoint{
+									Epoch: 1,
+									Root:  ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								},
+								Target: &eth.Checkpoint{
+									Epoch: 1,
+									Root:  ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								},
+							},
+							Signature: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+						},
+						Attestation_2: &eth.IndexedAttestationElectra{
+							AttestingIndices: []uint64{1},
+							Data: &eth.AttestationData{
+								Slot:            1,
+								CommitteeIndex:  1,
+								BeaconBlockRoot: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								Source: &eth.Checkpoint{
+									Epoch: 1,
+									Root:  ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								},
+								Target: &eth.Checkpoint{
+									Epoch: 1,
+									Root:  ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+								},
+							},
+							Signature: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+						},
+					},
+				},
+				Attestations: []*eth.AttestationElectra{
+					{
+						AggregationBits: bitfield.Bitlist{0x01},
+						Data: &eth.AttestationData{
+							Slot:            1,
+							CommitteeIndex:  1,
+							BeaconBlockRoot: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+							Source: &eth.Checkpoint{
+								Epoch: 1,
+								Root:  ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+							},
+							Target: &eth.Checkpoint{
+								Epoch: 1,
+								Root:  ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+							},
+						},
+						CommitteeBits: make(bitfield.Bitvector64, 8),
+						Signature:     ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+					},
+				},
+				Deposits: []*eth.Deposit{
+					{
+						Proof: func() [][]byte {
+							b := make([][]byte, 33)
+							for i := range b {
+								b[i] = ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2")
+							}
+							return b
+						}(),
+						Data: &eth.Deposit_Data{
+							PublicKey:             ezDecode(t, "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a"),
+							WithdrawalCredentials: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+							Amount:                1,
+							Signature:             ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+						},
+					},
+				},
+				VoluntaryExits: []*eth.SignedVoluntaryExit{
+					{
+						Exit: &eth.VoluntaryExit{
+							Epoch:          1,
+							ValidatorIndex: 1,
+						},
+						Signature: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+					},
+				},
+				SyncAggregate: &eth.SyncAggregate{
+					SyncCommitteeSignature: make([]byte, 96),
+					SyncCommitteeBits:      ezDecode(t, "0x6451e9f951ebf05edc01de67e593484b672877054f055903ff0df1a1a945cf30ca26bb4d4b154f94a1bc776bcf5d0efb3603e1f9b8ee2499ccdcfe2a18cef458"),
+				},
+				ExecutionRequests: &v1.ExecutionRequests{},
+				ExecutionPayloadHeader: &v1.ExecutionPayloadHeaderDeneb{
+					ParentHash:       ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+					FeeRecipient:     ezDecode(t, "0xabcf8e0d4e9587369b2301d0790347320302cc09"),
+					StateRoot:        ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+					ReceiptsRoot:     ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+					LogsBloom:        ezDecode(t, "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"),
+					PrevRandao:       ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+					BlockNumber:      1,
+					GasLimit:         1,
+					GasUsed:          1,
+					Timestamp:        1,
+					ExtraData:        ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+					BaseFeePerGas:    basebytes,
+					BlockHash:        ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+					TransactionsRoot: ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+					WithdrawalsRoot:  ezDecode(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"),
+					BlobGasUsed:      1,
+					ExcessBlobGas:    2,
+				},
+			},
+		},
+		Signature: ezDecode(t, "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"),
+	}
+}
+
 func TestRequestLogger(t *testing.T) {
 	wo := WithObserver(&requestLogger{})
 	c, err := NewClient("localhost:3500", wo)
--- a/api/client/builder/errors.go
+++ b/api/client/builder/errors.go
@@ -15,3 +15,9 @@ var ErrBadRequest = errors.Wrap(ErrNotOK, "recv 400 BadRequest response from API
 // ErrNoContent specifically means that a '204 - No Content' response was received from the API.
 // Typically, a 204 is a success but in this case for the Header API means No header is available
 var ErrNoContent = errors.New("recv 204 no content response from API, No header is available")
+
+// ErrUnsupportedMediaType specifically means that a '415 - Unsupported Media Type' was received from the API.
+var ErrUnsupportedMediaType = errors.Wrap(ErrNotOK, "The media type in \"Content-Type\" header is unsupported, and the request has been rejected. This occurs when a HTTP request supplies a payload in a content-type that the server is not able to handle.")
+
+// ErrNotAcceptable specifically means that a '406 - Not Acceptable' was received from the API.
+var ErrNotAcceptable = errors.Wrap(ErrNotOK, "The accept header value is not acceptable")
--- a/api/server/structs/endpoints_beacon.go
+++ b/api/server/structs/endpoints_beacon.go
@@ -78,8 +78,8 @@ type GetBlockHeaderResponse struct {
 }

 type GetValidatorsRequest struct {
-	Ids      []string `json:"ids"`
-	Statuses []string `json:"statuses"`
+	Ids      []string `json:"ids,omitempty"`
+	Statuses []string `json:"statuses,omitempty"`
 }

 type GetValidatorsResponse struct {
--- a/api/server/structs/endpoints_debug.go
+++ b/api/server/structs/endpoints_debug.go
@@ -54,4 +54,5 @@ type ForkChoiceNodeExtraData struct {
 	Balance                  string `json:"balance"`
 	ExecutionOptimistic      bool   `json:"execution_optimistic"`
 	TimeStamp                string `json:"timestamp"`
+	Target                   string `json:"target"`
 }
--- a/api/server/structs/endpoints_events.go
+++ b/api/server/structs/endpoints_events.go
@@ -20,6 +20,11 @@ type BlockEvent struct {
 	ExecutionOptimistic bool   `json:"execution_optimistic"`
 }

+type BlockGossipEvent struct {
+	Slot  string `json:"slot"`
+	Block string `json:"block"`
+}
+
 type AggregatedAttEventSource struct {
 	Aggregate *Attestation `json:"aggregate"`
 }
--- a/async/event/subscription.go
+++ b/async/event/subscription.go
@@ -154,7 +154,7 @@ retry:
 				continue retry
 			}
 			if sub == nil {
-				panic("event: ResubscribeFunc returned nil subscription and no error")
+				panic("event: ResubscribeFunc returned nil subscription and no error") // lint:nopanic -- This should never happen.
 			}
 			return sub
 		case <-s.unsub:
--- a/beacon-chain/blockchain/BUILD.bazel
+++ b/beacon-chain/blockchain/BUILD.bazel
@@ -26,6 +26,7 @@ go_library(
        "receive_blob.go",
        "receive_block.go",
        "service.go",
+        "setup_forchoice.go",
        "tracked_proposer.go",
        "weak_subjectivity_checks.go",
    ],
@@ -96,6 +97,7 @@ go_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",
+        "@com_github_prysmaticlabs_go_bitfield//:go_default_library",
        "@com_github_sirupsen_logrus//:go_default_library",
        "@org_golang_x_sync//errgroup:go_default_library",
    ],
@@ -126,6 +128,7 @@ go_test(
        "receive_block_test.go",
        "service_norace_test.go",
        "service_test.go",
+        "setup_forkchoice_test.go",
        "setup_test.go",
        "weak_subjectivity_checks_test.go",
    ],
@@ -154,6 +157,7 @@ go_test(
        "//beacon-chain/forkchoice/doubly-linked-tree:go_default_library",
        "//beacon-chain/forkchoice/types:go_default_library",
        "//beacon-chain/operations/attestations:go_default_library",
+        "//beacon-chain/operations/attestations/kv:go_default_library",
        "//beacon-chain/operations/blstoexec:go_default_library",
        "//beacon-chain/operations/slashings:go_default_library",
        "//beacon-chain/operations/voluntaryexits:go_default_library",
@@ -185,6 +189,7 @@ go_test(
        "@com_github_ethereum_go_ethereum//core/types:go_default_library",
        "@com_github_holiman_uint256//: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",
--- a/beacon-chain/blockchain/chain_info_test.go
+++ b/beacon-chain/blockchain/chain_info_test.go
@@ -582,6 +582,7 @@ func TestService_IsOptimisticForRoot_StateSummaryRecovered(t *testing.T) {
 	br, err := b.Block.HashTreeRoot()
 	require.NoError(t, err)
 	util.SaveBlock(t, context.Background(), beaconDB, b)
+	require.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, [32]byte{}))
 	_, err = c.IsOptimisticForRoot(ctx, br)
 	assert.NoError(t, err)
 	summ, err := beaconDB.StateSummary(ctx, br)
--- a/beacon-chain/blockchain/execution_engine.go
+++ b/beacon-chain/blockchain/execution_engine.go
@@ -69,10 +69,13 @@ func (s *Service) notifyForkchoiceUpdate(ctx context.Context, arg *fcuConfig) (*
 		SafeBlockHash:      justifiedHash[:],
 		FinalizedBlockHash: finalizedHash[:],
 	}
+	if len(fcs.HeadBlockHash) != 32 || [32]byte(fcs.HeadBlockHash) == [32]byte{} {
+		log.Error("Sending nil head block hash to execution engine")
+		return nil, nil
+	}
 	if arg.attributes == nil {
 		arg.attributes = payloadattribute.EmptyWithVersion(headBlk.Version())
 	}
-	go firePayloadAttributesEvent(ctx, s.cfg.StateNotifier.StateFeed(), arg)
 	payloadID, lastValidHash, err := s.cfg.ExecutionEngineCaller.ForkchoiceUpdated(ctx, fcs, arg.attributes)
 	if err != nil {
 		switch {
@@ -159,6 +162,7 @@ func (s *Service) notifyForkchoiceUpdate(ctx context.Context, arg *fcuConfig) (*
 		log.WithFields(logrus.Fields{
 			"blockRoot": fmt.Sprintf("%#x", bytesutil.Trunc(arg.headRoot[:])),
 			"headSlot":  headBlk.Slot(),
+			"nextSlot":  nextSlot,
 			"payloadID": fmt.Sprintf("%#x", bytesutil.Trunc(payloadID[:])),
 		}).Info("Forkchoice updated with payload attributes for proposal")
 		s.cfg.PayloadIDCache.Set(nextSlot, arg.headRoot, pId)
@@ -166,40 +170,19 @@ func (s *Service) notifyForkchoiceUpdate(ctx context.Context, arg *fcuConfig) (*
 		log.WithFields(logrus.Fields{
 			"blockHash": fmt.Sprintf("%#x", headPayload.BlockHash()),
 			"slot":      headBlk.Slot(),
+			"nextSlot":  nextSlot,
 		}).Error("Received nil payload ID on VALID engine response")
 	}
 	return payloadID, nil
 }

-func firePayloadAttributesEvent(ctx context.Context, f event.SubscriberSender, cfg *fcuConfig) {
-	pidx, err := helpers.BeaconProposerIndex(ctx, cfg.headState)
-	if err != nil {
-		log.WithError(err).
-			WithField("head_root", cfg.headRoot[:]).
-			Error("Could not get proposer index for PayloadAttributes event")
-		return
-	}
-	evd := payloadattribute.EventData{
-		ProposerIndex:   pidx,
-		ProposalSlot:    cfg.headState.Slot(),
-		ParentBlockRoot: cfg.headRoot[:],
-		Attributer:      cfg.attributes,
-		HeadRoot:        cfg.headRoot,
-		HeadState:       cfg.headState,
-		HeadBlock:       cfg.headBlock,
-	}
-	if cfg.headBlock != nil && !cfg.headBlock.IsNil() {
-		headPayload, err := cfg.headBlock.Block().Body().Execution()
-		if err != nil {
-			log.WithError(err).Error("Could not get execution payload for head block")
-			return
-		}
-		evd.ParentBlockHash = headPayload.BlockHash()
-		evd.ParentBlockNumber = headPayload.BlockNumber()
-	}
+func firePayloadAttributesEvent(_ context.Context, f event.SubscriberSender, nextSlot primitives.Slot) {
+	// the fcu args have differing amounts of completeness based on the code path,
+	// and there is work we only want to do if a client is actually listening to the events beacon api endpoint.
+	// temporary solution: just fire a blank event and fill in the details in the api handler.
 	f.Send(&feed.Event{
 		Type: statefeed.PayloadAttributes,
-		Data: evd,
+		Data: payloadattribute.EventData{ProposalSlot: nextSlot},
 	})
 }

--- a/beacon-chain/blockchain/forkchoice_update_execution.go
+++ b/beacon-chain/blockchain/forkchoice_update_execution.go
@@ -102,10 +102,10 @@ func (s *Service) forkchoiceUpdateWithExecution(ctx context.Context, args *fcuCo
 		log.WithError(err).Error("could not save head")
 	}

+	go firePayloadAttributesEvent(ctx, s.cfg.StateNotifier.StateFeed(), s.CurrentSlot()+1)
+
 	// Only need to prune attestations from pool if the head has changed.
-	if err := s.pruneAttsFromPool(args.headBlock); err != nil {
-		log.WithError(err).Error("could not prune attestations from pool")
-	}
+	s.pruneAttsFromPool(s.ctx, args.headState, args.headBlock)
 	return nil
 }

--- a/beacon-chain/blockchain/mock_test.go
+++ b/beacon-chain/blockchain/mock_test.go
@@ -3,6 +3,7 @@ package blockchain
 import (
 	"testing"

+	mock "github.com/prysmaticlabs/prysm/v5/beacon-chain/blockchain/testing"
 	testDB "github.com/prysmaticlabs/prysm/v5/beacon-chain/db/testing"
 	doublylinkedtree "github.com/prysmaticlabs/prysm/v5/beacon-chain/forkchoice/doubly-linked-tree"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/startup"
@@ -18,6 +19,7 @@ func testServiceOptsWithDB(t *testing.T) []Option {
 		WithStateGen(stategen.New(beaconDB, fcs)),
 		WithForkChoiceStore(fcs),
 		WithClockSynchronizer(cs),
+		WithStateNotifier(&mock.MockStateNotifier{RecordEvents: true}),
 	}
 }

--- a/beacon-chain/blockchain/options.go
+++ b/beacon-chain/blockchain/options.go
@@ -213,3 +213,10 @@ func WithSyncChecker(checker Checker) Option {
 		return nil
 	}
 }
+
+func WithSlasherEnabled(enabled bool) Option {
+	return func(s *Service) error {
+		s.slasherEnabled = enabled
+		return nil
+	}
+}
--- a/beacon-chain/blockchain/process_attestation.go
+++ b/beacon-chain/blockchain/process_attestation.go
@@ -80,7 +80,7 @@ func (s *Service) OnAttestation(ctx context.Context, a ethpb.Att, disparity time
 	}

 	// Use the target state to verify attesting indices are valid.
-	committees, err := helpers.AttestationCommittees(ctx, baseState, a)
+	committees, err := helpers.AttestationCommitteesFromState(ctx, baseState, a)
 	if err != nil {
 		return err
 	}
--- a/beacon-chain/blockchain/process_block.go
+++ b/beacon-chain/blockchain/process_block.go
@@ -6,6 +6,7 @@ import (
 	"time"

 	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/go-bitfield"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/blocks"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/helpers"
 	coreTime "github.com/prysmaticlabs/prysm/v5/beacon-chain/core/time"
@@ -15,6 +16,7 @@ import (
 	forkchoicetypes "github.com/prysmaticlabs/prysm/v5/beacon-chain/forkchoice/types"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state"
 	"github.com/prysmaticlabs/prysm/v5/config/features"
+	fieldparams "github.com/prysmaticlabs/prysm/v5/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/v5/config/params"
 	consensusblocks "github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
@@ -368,7 +370,7 @@ func (s *Service) handleEpochBoundary(ctx context.Context, slot primitives.Slot,
 func (s *Service) handleBlockAttestations(ctx context.Context, blk interfaces.ReadOnlyBeaconBlock, st state.BeaconState) error {
 	// Feed in block's attestations to fork choice store.
 	for _, a := range blk.Body().Attestations() {
-		committees, err := helpers.AttestationCommittees(ctx, st, a)
+		committees, err := helpers.AttestationCommitteesFromState(ctx, st, a)
 		if err != nil {
 			return err
 		}
@@ -419,24 +421,98 @@ func (s *Service) savePostStateInfo(ctx context.Context, r [32]byte, b interface
 	return nil
 }

-// This removes the attestations in block `b` from the attestation mem pool.
-func (s *Service) pruneAttsFromPool(headBlock interfaces.ReadOnlySignedBeaconBlock) error {
-	atts := headBlock.Block().Body().Attestations()
-	for _, att := range atts {
-		if features.Get().EnableExperimentalAttestationPool {
-			if err := s.cfg.AttestationCache.DeleteCovered(att); err != nil {
-				return errors.Wrap(err, "could not delete attestation")
-			}
-		} else if att.IsAggregated() {
-			if err := s.cfg.AttPool.DeleteAggregatedAttestation(att); err != nil {
-				return err
-			}
-		} else {
-			if err := s.cfg.AttPool.DeleteUnaggregatedAttestation(att); err != nil {
-				return err
-			}
+// pruneAttsFromPool removes these attestations from the attestation pool
+// which are covered by attestations from the received block.
+func (s *Service) pruneAttsFromPool(ctx context.Context, headState state.BeaconState, headBlock interfaces.ReadOnlySignedBeaconBlock) {
+	for _, att := range headBlock.Block().Body().Attestations() {
+		if err := s.pruneCoveredAttsFromPool(ctx, headState, att); err != nil {
+			log.WithError(err).Warn("Could not prune attestations covered by a received block's attestation")
 		}
 	}
+}
+
+func (s *Service) pruneCoveredAttsFromPool(ctx context.Context, headState state.BeaconState, att ethpb.Att) error {
+	switch {
+	case !att.IsAggregated():
+		return s.cfg.AttPool.DeleteUnaggregatedAttestation(att)
+	case att.Version() == version.Phase0:
+		if features.Get().EnableExperimentalAttestationPool {
+			return errors.Wrap(s.cfg.AttestationCache.DeleteCovered(att), "could not delete covered attestation")
+		}
+		return errors.Wrap(s.cfg.AttPool.DeleteAggregatedAttestation(att), "could not delete aggregated attestation")
+	default:
+		return s.pruneCoveredElectraAttsFromPool(ctx, headState, att)
+	}
+}
+
+// pruneCoveredElectraAttsFromPool handles removing aggregated Electra attestations from the pool after receiving a block.
+// Because in Electra block attestations can combine aggregates for multiple committees, comparing attestation bits
+// of a block attestation with attestations bits of an aggregate can cause unexpected results, leading to covered
+// aggregates not being removed from the pool.
+//
+// To make sure aggregates are removed, we decompose the block attestation into dummy aggregates, with each
+// aggregate accounting for one committee. This allows us to compare aggregates in the same way it's done for
+// Phase0. Even though we can't provide a valid signature for the dummy aggregate, it does not matter because
+// signatures play no part in pruning attestations.
+func (s *Service) pruneCoveredElectraAttsFromPool(ctx context.Context, headState state.BeaconState, att ethpb.Att) error {
+	if att.Version() == version.Phase0 {
+		log.Error("Called pruneCoveredElectraAttsFromPool with a Phase0 attestation")
+		return nil
+	}
+
+	// We don't want to recompute committees. If they are not cached already,
+	// we allow attestations to stay in the pool. If these attestations are
+	// included in a later block, they will be redundant. But given that
+	// they were not cached in the first place, it's unlikely that they
+	// will be chosen into a block.
+	ok, committees, err := helpers.AttestationCommitteesFromCache(ctx, headState, att)
+	if err != nil {
+		return errors.Wrap(err, "could not get attestation committees")
+	}
+	if !ok {
+		log.Debug("Attestation committees are not cached. Skipping attestation pruning.")
+		return nil
+	}
+
+	committeeIndices := att.CommitteeBitsVal().BitIndices()
+	offset := uint64(0)
+
+	// Sanity check as this should never happen
+	if len(committeeIndices) != len(committees) {
+		return errors.New("committee indices and committees have different lengths")
+	}
+
+	for i, c := range committees {
+		ab := bitfield.NewBitlist(uint64(len(c)))
+		for j := uint64(0); j < uint64(len(c)); j++ {
+			ab.SetBitAt(j, att.GetAggregationBits().BitAt(j+offset))
+		}
+
+		cb := primitives.NewAttestationCommitteeBits()
+		cb.SetBitAt(uint64(committeeIndices[i]), true)
+
+		a := &ethpb.AttestationElectra{
+			AggregationBits: ab,
+			Data:            att.GetData(),
+			CommitteeBits:   cb,
+			Signature:       make([]byte, fieldparams.BLSSignatureLength),
+		}
+
+		if features.Get().EnableExperimentalAttestationPool {
+			if err = s.cfg.AttestationCache.DeleteCovered(a); err != nil {
+				return errors.Wrap(err, "could not delete covered attestation")
+			}
+		} else if !a.IsAggregated() {
+			if err = s.cfg.AttPool.DeleteUnaggregatedAttestation(a); err != nil {
+				return errors.Wrap(err, "could not delete unaggregated attestation")
+			}
+		} else if err = s.cfg.AttPool.DeleteAggregatedAttestation(a); err != nil {
+			return errors.Wrap(err, "could not delete aggregated attestation")
+		}
+
+		offset += uint64(len(c))
+	}
+
 	return nil
 }

@@ -650,13 +726,9 @@ func (s *Service) lateBlockTasks(ctx context.Context) {
 	attribute := s.getPayloadAttribute(ctx, headState, s.CurrentSlot()+1, headRoot[:])
 	// return early if we are not proposing next slot
 	if attribute.IsEmpty() {
-		fcuArgs := &fcuConfig{
-			headState:  headState,
-			headRoot:   headRoot,
-			headBlock:  nil,
-			attributes: attribute,
-		}
-		go firePayloadAttributesEvent(ctx, s.cfg.StateNotifier.StateFeed(), fcuArgs)
+		// notifyForkchoiceUpdate fires the payload attribute event. But in this case, we won't
+		// call notifyForkchoiceUpdate, so the event is fired here.
+		go firePayloadAttributesEvent(ctx, s.cfg.StateNotifier.StateFeed(), s.CurrentSlot()+1)
 		return
 	}

--- a/beacon-chain/blockchain/process_block_test.go
+++ b/beacon-chain/blockchain/process_block_test.go
@@ -12,8 +12,10 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	gethtypes "github.com/ethereum/go-ethereum/core/types"
 	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/go-bitfield"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/cache"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/blocks"
+	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/helpers"
 	lightClient "github.com/prysmaticlabs/prysm/v5/beacon-chain/core/light-client"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/signing"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/transition"
@@ -25,6 +27,7 @@ import (
 	mockExecution "github.com/prysmaticlabs/prysm/v5/beacon-chain/execution/testing"
 	doublylinkedtree "github.com/prysmaticlabs/prysm/v5/beacon-chain/forkchoice/doubly-linked-tree"
 	forkchoicetypes "github.com/prysmaticlabs/prysm/v5/beacon-chain/forkchoice/types"
+	"github.com/prysmaticlabs/prysm/v5/beacon-chain/operations/attestations/kv"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state"
 	"github.com/prysmaticlabs/prysm/v5/config/features"
 	fieldparams "github.com/prysmaticlabs/prysm/v5/config/fieldparams"
@@ -45,6 +48,94 @@ import (
 	logTest "github.com/sirupsen/logrus/hooks/test"
 )

+func Test_pruneAttsFromPool_Electra(t *testing.T) {
+	ctx := context.Background()
+	logHook := logTest.NewGlobal()
+
+	params.SetupTestConfigCleanup(t)
+	cfg := params.BeaconConfig().Copy()
+	cfg.TargetCommitteeSize = 8
+	params.OverrideBeaconConfig(cfg)
+
+	s := Service{
+		cfg: &config{
+			AttPool: kv.NewAttCaches(),
+		},
+	}
+
+	data := &ethpb.AttestationData{
+		BeaconBlockRoot: make([]byte, 32),
+		Source:          &ethpb.Checkpoint{Root: make([]byte, 32)},
+		Target:          &ethpb.Checkpoint{Root: make([]byte, 32)},
+	}
+
+	cb := primitives.NewAttestationCommitteeBits()
+	cb.SetBitAt(0, true)
+	att1 := &ethpb.AttestationElectra{
+		AggregationBits: bitfield.Bitlist{0b10000000, 0b00000001},
+		Data:            data,
+		Signature:       make([]byte, 96),
+		CommitteeBits:   cb,
+	}
+
+	cb = primitives.NewAttestationCommitteeBits()
+	cb.SetBitAt(1, true)
+	att2 := &ethpb.AttestationElectra{
+		AggregationBits: bitfield.Bitlist{0b11110111, 0b00000001},
+		Data:            data,
+		Signature:       make([]byte, 96),
+		CommitteeBits:   cb,
+	}
+
+	cb = primitives.NewAttestationCommitteeBits()
+	cb.SetBitAt(3, true)
+	att3 := &ethpb.AttestationElectra{
+		AggregationBits: bitfield.Bitlist{0b11110111, 0b00000001},
+		Data:            data,
+		Signature:       make([]byte, 96),
+		CommitteeBits:   cb,
+	}
+
+	require.NoError(t, s.cfg.AttPool.SaveUnaggregatedAttestation(att1))
+	require.NoError(t, s.cfg.AttPool.SaveAggregatedAttestation(att2))
+	require.NoError(t, s.cfg.AttPool.SaveAggregatedAttestation(att3))
+
+	cb = primitives.NewAttestationCommitteeBits()
+	cb.SetBitAt(0, true)
+	cb.SetBitAt(1, true)
+	onChainAtt := &ethpb.AttestationElectra{
+		AggregationBits: bitfield.Bitlist{0b10000000, 0b11110111, 0b00000001},
+		Data:            data,
+		Signature:       make([]byte, 96),
+		CommitteeBits:   cb,
+	}
+	bl := &ethpb.SignedBeaconBlockElectra{
+		Block: &ethpb.BeaconBlockElectra{
+			Body: &ethpb.BeaconBlockBodyElectra{
+				Attestations: []*ethpb.AttestationElectra{onChainAtt},
+			},
+		},
+		Signature: make([]byte, 96),
+	}
+	rob, err := consensusblocks.NewSignedBeaconBlock(bl)
+	require.NoError(t, err)
+	st, _ := util.DeterministicGenesisStateElectra(t, 1024)
+	committees, err := helpers.BeaconCommittees(ctx, st, 0)
+	require.NoError(t, err)
+	// Sanity check to make sure the on-chain att will be decomposed
+	// into the correct number of aggregates.
+	require.Equal(t, 4, len(committees))
+
+	s.pruneAttsFromPool(ctx, st, rob)
+	require.LogsDoNotContain(t, logHook, "Could not prune attestations")
+
+	attsInPool := s.cfg.AttPool.UnaggregatedAttestations()
+	assert.Equal(t, 0, len(attsInPool))
+	attsInPool = s.cfg.AttPool.AggregatedAttestations()
+	require.Equal(t, 1, len(attsInPool))
+	assert.DeepEqual(t, att3, attsInPool[0])
+}
+
 func TestStore_OnBlockBatch(t *testing.T) {
 	service, tr := minimalTestService(t)
 	ctx := tr.ctx
@@ -821,6 +912,8 @@ func TestInsertFinalizedDeposits_MultipleFinalizedRoutines(t *testing.T) {
 }

 func TestRemoveBlockAttestationsInPool(t *testing.T) {
+	logHook := logTest.NewGlobal()
+
 	genesis, keys := util.DeterministicGenesisState(t, 64)
 	b, err := util.GenerateFullBlock(genesis, keys, util.DefaultBlockGenConfig(), 1)
 	assert.NoError(t, err)
@@ -840,7 +933,8 @@ func TestRemoveBlockAttestationsInPool(t *testing.T) {
 	require.NoError(t, service.cfg.AttPool.SaveAggregatedAttestations(atts))
 	wsb, err := consensusblocks.NewSignedBeaconBlock(b)
 	require.NoError(t, err)
-	require.NoError(t, service.pruneAttsFromPool(wsb))
+	service.pruneAttsFromPool(context.Background(), nil /* state not needed pre-Electra */, wsb)
+	require.LogsDoNotContain(t, logHook, "Could not prune attestations")
 	require.Equal(t, 0, service.cfg.AttPool.AggregatedAttestationCount())
 }

@@ -1896,6 +1990,7 @@ func TestNoViableHead_Reboot(t *testing.T) {

 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, genesisState, genesisRoot), "Could not save genesis state")
 	require.NoError(t, service.cfg.BeaconDB.SaveHeadBlockRoot(ctx, genesisRoot), "Could not save genesis state")
+	require.NoError(t, service.cfg.BeaconDB.SaveGenesisBlockRoot(ctx, genesisRoot), "Could not save genesis state")

 	for i := 1; i < 6; i++ {
 		driftGenesisTime(service, int64(i), 0)
@@ -2030,6 +2125,7 @@ func TestNoViableHead_Reboot(t *testing.T) {
 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, genesisState, jroot))
 	service.cfg.ForkChoiceStore.SetBalancesByRooter(service.cfg.StateGen.ActiveNonSlashedBalancesByRoot)
 	require.NoError(t, service.StartFromSavedState(genesisState))
+	require.NoError(t, service.cfg.BeaconDB.SaveGenesisBlockRoot(ctx, genesisRoot))

 	// Forkchoice has the genesisRoot loaded at startup
 	require.Equal(t, genesisRoot, service.ensureRootNotZeros(service.cfg.ForkChoiceStore.CachedHeadRoot()))
--- a/beacon-chain/blockchain/receive_block.go
+++ b/beacon-chain/blockchain/receive_block.go
@@ -16,7 +16,6 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/das"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/slasher/types"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state"
-	"github.com/prysmaticlabs/prysm/v5/config/features"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
@@ -121,7 +120,7 @@ func (s *Service) ReceiveBlock(ctx context.Context, block interfaces.ReadOnlySig
 		return err
 	}
 	// If slasher is configured, forward the attestations in the block via an event feed for processing.
-	if features.Get().EnableSlasher {
+	if s.slasherEnabled {
 		go s.sendBlockAttestationsToSlasher(blockCopy, preState)
 	}

@@ -548,7 +547,7 @@ func (s *Service) sendBlockAttestationsToSlasher(signed interfaces.ReadOnlySigne
 	// is done in the background to avoid adding more load to this critical code path.
 	ctx := context.TODO()
 	for _, att := range signed.Block().Body().Attestations() {
-		committees, err := helpers.AttestationCommittees(ctx, preState, att)
+		committees, err := helpers.AttestationCommitteesFromState(ctx, preState, att)
 		if err != nil {
 			log.WithError(err).Error("Could not get attestation committees")
 			return
--- a/beacon-chain/blockchain/service.go
+++ b/beacon-chain/blockchain/service.go
@@ -3,7 +3,6 @@
 package blockchain

 import (
-	"bytes"
 	"context"
 	"fmt"
 	"runtime"
@@ -23,7 +22,6 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/db/filesystem"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/execution"
 	f "github.com/prysmaticlabs/prysm/v5/beacon-chain/forkchoice"
-	forkchoicetypes "github.com/prysmaticlabs/prysm/v5/beacon-chain/forkchoice/types"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/operations/attestations"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/operations/blstoexec"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/operations/slashings"
@@ -32,7 +30,6 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/startup"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state/stategen"
-	"github.com/prysmaticlabs/prysm/v5/config/features"
 	"github.com/prysmaticlabs/prysm/v5/config/params"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
@@ -42,6 +39,7 @@ import (
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
 	prysmTime "github.com/prysmaticlabs/prysm/v5/time"
 	"github.com/prysmaticlabs/prysm/v5/time/slots"
+	"github.com/sirupsen/logrus"
 )

 // Service represents a service that handles the internal
@@ -65,6 +63,7 @@ type Service struct {
 	blobNotifiers        *blobNotifierMap
 	blockBeingSynced     *currentlySyncingBlock
 	blobStorage          *filesystem.BlobStorage
+	slasherEnabled       bool
 }

 // config options for the service.
@@ -269,69 +268,18 @@ func (s *Service) StartFromSavedState(saved state.BeaconState) error {
 		return err
 	}
 	s.originBlockRoot = originRoot
-
-	if err := s.initializeHeadFromDB(s.ctx); err != nil {
-		return errors.Wrap(err, "could not set up chain info")
+	st, err := s.cfg.StateGen.Resume(s.ctx, s.cfg.FinalizedStateAtStartUp)
+	if err != nil {
+		return errors.Wrap(err, "could not get finalized state from db")
 	}
 	spawnCountdownIfPreGenesis(s.ctx, s.genesisTime, s.cfg.BeaconDB)
-
-	justified, err := s.cfg.BeaconDB.JustifiedCheckpoint(s.ctx)
-	if err != nil {
-		return errors.Wrap(err, "could not get justified checkpoint")
-	}
-	if justified == nil {
-		return errNilJustifiedCheckpoint
-	}
-	finalized, err := s.cfg.BeaconDB.FinalizedCheckpoint(s.ctx)
-	if err != nil {
-		return errors.Wrap(err, "could not get finalized checkpoint")
-	}
-	if finalized == nil {
-		return errNilFinalizedCheckpoint
-	}
-
-	fRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(finalized.Root))
-	s.cfg.ForkChoiceStore.Lock()
-	defer s.cfg.ForkChoiceStore.Unlock()
-	if err := s.cfg.ForkChoiceStore.UpdateJustifiedCheckpoint(s.ctx, &forkchoicetypes.Checkpoint{Epoch: justified.Epoch,
-		Root: bytesutil.ToBytes32(justified.Root)}); err != nil {
-		return errors.Wrap(err, "could not update forkchoice's justified checkpoint")
-	}
-	if err := s.cfg.ForkChoiceStore.UpdateFinalizedCheckpoint(&forkchoicetypes.Checkpoint{Epoch: finalized.Epoch,
-		Root: bytesutil.ToBytes32(finalized.Root)}); err != nil {
-		return errors.Wrap(err, "could not update forkchoice's finalized checkpoint")
-	}
-	s.cfg.ForkChoiceStore.SetGenesisTime(uint64(s.genesisTime.Unix()))
-
-	st, err := s.cfg.StateGen.StateByRoot(s.ctx, fRoot)
-	if err != nil {
-		return errors.Wrap(err, "could not get finalized checkpoint state")
-	}
-	finalizedBlock, err := s.cfg.BeaconDB.Block(s.ctx, fRoot)
-	if err != nil {
-		return errors.Wrap(err, "could not get finalized checkpoint block")
-	}
-	roblock, err := blocks.NewROBlockWithRoot(finalizedBlock, fRoot)
-	if err != nil {
-		return err
-	}
-	if err := s.cfg.ForkChoiceStore.InsertNode(s.ctx, st, roblock); err != nil {
-		return errors.Wrap(err, "could not insert finalized block to forkchoice")
-	}
-	if !features.Get().EnableStartOptimistic {
-		lastValidatedCheckpoint, err := s.cfg.BeaconDB.LastValidatedCheckpoint(s.ctx)
-		if err != nil {
-			return errors.Wrap(err, "could not get last validated checkpoint")
-		}
-		if bytes.Equal(finalized.Root, lastValidatedCheckpoint.Root) {
-			if err := s.cfg.ForkChoiceStore.SetOptimisticToValid(s.ctx, fRoot); err != nil {
-				return errors.Wrap(err, "could not set finalized block as validated")
-			}
-		}
+	if err := s.setupForkchoice(st); err != nil {
+		return errors.Wrap(err, "could not set up forkchoice")
 	}
 	// not attempting to save initial sync blocks here, because there shouldn't be any until
 	// after the statefeed.Initialized event is fired (below)
-	if err := s.wsVerifier.VerifyWeakSubjectivity(s.ctx, finalized.Epoch); err != nil {
+	cp := s.FinalizedCheckpt()
+	if err := s.wsVerifier.VerifyWeakSubjectivity(s.ctx, cp.Epoch); err != nil {
 		// Exit run time if the node failed to verify weak subjectivity checkpoint.
 		return errors.Wrap(err, "could not verify initial checkpoint provided for chain sync")
 	}
@@ -340,7 +288,6 @@ func (s *Service) StartFromSavedState(saved state.BeaconState) error {
 	if err := s.clockSetter.SetClock(startup.NewClock(s.genesisTime, vr)); err != nil {
 		return errors.Wrap(err, "failed to initialize blockchain service")
 	}
-
 	return nil
 }

@@ -370,45 +317,36 @@ func (s *Service) originRootFromSavedState(ctx context.Context) ([32]byte, error
 	return genesisBlkRoot, nil
 }

-// initializeHeadFromDB uses the finalized checkpoint and head block found in the database to set the current head.
+// initializeHeadFromDB uses the finalized checkpoint and head block root from forkchoice to set the current head.
 // Note that this may block until stategen replays blocks between the finalized and head blocks
 // if the head sync flag was specified and the gap between the finalized and head blocks is at least 128 epochs long.
-func (s *Service) initializeHeadFromDB(ctx context.Context) error {
-	finalized, err := s.cfg.BeaconDB.FinalizedCheckpoint(ctx)
-	if err != nil {
-		return errors.Wrap(err, "could not get finalized checkpoint from db")
-	}
-	if finalized == nil {
-		// This should never happen. At chain start, the finalized checkpoint
-		// would be the genesis state and block.
-		return errors.New("no finalized epoch in the database")
-	}
-	finalizedRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(finalized.Root))
-	var finalizedState state.BeaconState
-
-	finalizedState, err = s.cfg.StateGen.Resume(ctx, s.cfg.FinalizedStateAtStartUp)
-	if err != nil {
-		return errors.Wrap(err, "could not get finalized state from db")
-	}
-
-	if finalizedState == nil || finalizedState.IsNil() {
+func (s *Service) initializeHead(ctx context.Context, st state.BeaconState) error {
+	cp := s.FinalizedCheckpt()
+	fRoot := s.ensureRootNotZeros([32]byte(cp.Root))
+	if st == nil || st.IsNil() {
 		return errors.New("finalized state can't be nil")
 	}

-	finalizedBlock, err := s.getBlock(ctx, finalizedRoot)
+	s.cfg.ForkChoiceStore.RLock()
+	root := s.cfg.ForkChoiceStore.HighestReceivedBlockRoot()
+	s.cfg.ForkChoiceStore.RUnlock()
+	blk, err := s.cfg.BeaconDB.Block(ctx, root)
 	if err != nil {
-		return errors.Wrap(err, "could not get finalized block")
+		return errors.Wrap(err, "could not get head block")
 	}
-	if err := s.setHead(&head{
-		finalizedRoot,
-		finalizedBlock,
-		finalizedState,
-		finalizedBlock.Block().Slot(),
-		false,
-	}); err != nil {
+	if root != fRoot {
+		st, err = s.cfg.StateGen.StateByRoot(ctx, root)
+		if err != nil {
+			return errors.Wrap(err, "could not get head state")
+		}
+	}
+	if err := s.setHead(&head{root, blk, st, blk.Block().Slot(), false}); err != nil {
 		return errors.Wrap(err, "could not set head")
 	}
-
+	log.WithFields(logrus.Fields{
+		"root": fmt.Sprintf("%#x", root),
+		"slot": blk.Block().Slot(),
+	}).Info("Initialized head block from DB")
 	return nil
 }

--- a/beacon-chain/blockchain/setup_forchoice.go
+++ b/beacon-chain/blockchain/setup_forchoice.go
@@ -0,0 +1,175 @@
+package blockchain
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+
+	"github.com/pkg/errors"
+	forkchoicetypes "github.com/prysmaticlabs/prysm/v5/beacon-chain/forkchoice/types"
+	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state"
+	"github.com/prysmaticlabs/prysm/v5/config/features"
+	"github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
+	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
+	"github.com/prysmaticlabs/prysm/v5/encoding/bytesutil"
+	"github.com/prysmaticlabs/prysm/v5/time/slots"
+)
+
+func (s *Service) setupForkchoice(st state.BeaconState) error {
+	if err := s.setupForkchoiceCheckpoints(); err != nil {
+		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")
+	}
+	if err := s.initializeHead(s.ctx, st); err != nil {
+		return errors.Wrap(err, "could not initialize head from db")
+	}
+	return nil
+}
+
+func (s *Service) startupHeadRoot() [32]byte {
+	headStr := features.Get().ForceHead
+	cp := s.FinalizedCheckpt()
+	fRoot := s.ensureRootNotZeros([32]byte(cp.Root))
+	if headStr == "" {
+		return fRoot
+	}
+	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.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
+	}
+	return [32]byte(root)
+}
+
+func (s *Service) setupForkchoiceTree(st state.BeaconState) error {
+	headRoot := s.startupHeadRoot()
+	cp := s.FinalizedCheckpt()
+	fRoot := s.ensureRootNotZeros([32]byte(cp.Root))
+	if err := s.setupForkchoiceRoot(st); err != nil {
+		return errors.Wrap(err, "could not set up forkchoice root")
+	}
+	if headRoot == fRoot {
+		return nil
+	}
+	blk, err := s.cfg.BeaconDB.Block(s.ctx, headRoot)
+	if err != nil {
+		log.WithError(err).Error("could not get head block, starting with finalized block as head")
+		return nil
+	}
+	if slots.ToEpoch(blk.Block().Slot()) < cp.Epoch {
+		log.WithField("headRoot", fmt.Sprintf("%#x", headRoot)).Error("head block is older than finalized block, starting with finalized block as head")
+		return nil
+	}
+	chain, err := s.buildForkchoiceChain(s.ctx, blk)
+	if err != nil {
+		log.WithError(err).Error("could not build forkchoice chain, starting with finalized block as head")
+		return nil
+	}
+	s.cfg.ForkChoiceStore.Lock()
+	defer s.cfg.ForkChoiceStore.Unlock()
+	return s.cfg.ForkChoiceStore.InsertChain(s.ctx, chain)
+}
+
+func (s *Service) buildForkchoiceChain(ctx context.Context, head interfaces.ReadOnlySignedBeaconBlock) ([]*forkchoicetypes.BlockAndCheckpoints, error) {
+	chain := []*forkchoicetypes.BlockAndCheckpoints{}
+	cp := s.FinalizedCheckpt()
+	fRoot := s.ensureRootNotZeros([32]byte(cp.Root))
+	jp := s.CurrentJustifiedCheckpt()
+	root, err := head.Block().HashTreeRoot()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not get head block root")
+	}
+	for {
+		roblock, err := blocks.NewROBlockWithRoot(head, root)
+		if err != nil {
+			return nil, err
+		}
+		// This chain sets the justified checkpoint for every block, including some that are older than jp.
+		// This should be however safe for forkchoice at startup. An alternative would be to hook during the
+		// block processing pipeline when setting the head state, to compute the right states for the justified
+		// checkpoint.
+		chain = append(chain, &forkchoicetypes.BlockAndCheckpoints{Block: roblock, JustifiedCheckpoint: jp, FinalizedCheckpoint: cp})
+		root = head.Block().ParentRoot()
+		if root == fRoot {
+			break
+		}
+		head, err = s.cfg.BeaconDB.Block(s.ctx, root)
+		if err != nil {
+			return nil, errors.Wrap(err, "could not get block")
+		}
+		if slots.ToEpoch(head.Block().Slot()) < cp.Epoch {
+			return nil, errors.New("head block is not a descendant of the finalized checkpoint")
+		}
+	}
+	return chain, nil
+}
+
+func (s *Service) setupForkchoiceRoot(st state.BeaconState) error {
+	cp := s.FinalizedCheckpt()
+	fRoot := s.ensureRootNotZeros([32]byte(cp.Root))
+	finalizedBlock, err := s.cfg.BeaconDB.Block(s.ctx, fRoot)
+	if err != nil {
+		return errors.Wrap(err, "could not get finalized checkpoint block")
+	}
+	roblock, err := blocks.NewROBlockWithRoot(finalizedBlock, fRoot)
+	if err != nil {
+		return err
+	}
+	if err := s.cfg.ForkChoiceStore.InsertNode(s.ctx, st, roblock); err != nil {
+		return errors.Wrap(err, "could not insert finalized block to forkchoice")
+	}
+	if !features.Get().EnableStartOptimistic {
+		lastValidatedCheckpoint, err := s.cfg.BeaconDB.LastValidatedCheckpoint(s.ctx)
+		if err != nil {
+			return errors.Wrap(err, "could not get last validated checkpoint")
+		}
+		if bytes.Equal(fRoot[:], lastValidatedCheckpoint.Root) {
+			if err := s.cfg.ForkChoiceStore.SetOptimisticToValid(s.ctx, fRoot); err != nil {
+				return errors.Wrap(err, "could not set finalized block as validated")
+			}
+		}
+	}
+	return nil
+}
+
+func (s *Service) setupForkchoiceCheckpoints() error {
+	justified, err := s.cfg.BeaconDB.JustifiedCheckpoint(s.ctx)
+	if err != nil {
+		return errors.Wrap(err, "could not get justified checkpoint")
+	}
+	if justified == nil {
+		return errNilJustifiedCheckpoint
+	}
+	finalized, err := s.cfg.BeaconDB.FinalizedCheckpoint(s.ctx)
+	if err != nil {
+		return errors.Wrap(err, "could not get finalized checkpoint")
+	}
+	if finalized == nil {
+		return errNilFinalizedCheckpoint
+	}
+
+	fRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(finalized.Root))
+	s.cfg.ForkChoiceStore.Lock()
+	defer s.cfg.ForkChoiceStore.Unlock()
+	if err := s.cfg.ForkChoiceStore.UpdateJustifiedCheckpoint(s.ctx, &forkchoicetypes.Checkpoint{Epoch: justified.Epoch,
+		Root: bytesutil.ToBytes32(justified.Root)}); err != nil {
+		return errors.Wrap(err, "could not update forkchoice's justified checkpoint")
+	}
+	if err := s.cfg.ForkChoiceStore.UpdateFinalizedCheckpoint(&forkchoicetypes.Checkpoint{Epoch: finalized.Epoch,
+		Root: fRoot}); err != nil {
+		return errors.Wrap(err, "could not update forkchoice's finalized checkpoint")
+	}
+	s.cfg.ForkChoiceStore.SetGenesisTime(uint64(s.genesisTime.Unix()))
+	return nil
+}
--- a/beacon-chain/blockchain/setup_forkchoice_test.go
+++ b/beacon-chain/blockchain/setup_forkchoice_test.go
@@ -0,0 +1,128 @@
+package blockchain
+
+import (
+	"testing"
+
+	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/blocks"
+	"github.com/prysmaticlabs/prysm/v5/config/features"
+	"github.com/prysmaticlabs/prysm/v5/config/params"
+	consensusblocks "github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
+	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
+	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/v5/testing/require"
+	"github.com/prysmaticlabs/prysm/v5/testing/util"
+	logTest "github.com/sirupsen/logrus/hooks/test"
+)
+
+func Test_startupHeadRoot(t *testing.T) {
+	service, tr := minimalTestService(t)
+	ctx := tr.ctx
+	hook := logTest.NewGlobal()
+	cp := service.FinalizedCheckpt()
+	require.DeepEqual(t, cp.Root, params.BeaconConfig().ZeroHash[:])
+	gr := [32]byte{'r', 'o', 'o', 't'}
+	service.originBlockRoot = gr
+	require.NoError(t, service.cfg.BeaconDB.SaveGenesisBlockRoot(ctx, gr))
+	t.Run("start from finalized", func(t *testing.T) {
+		require.Equal(t, service.startupHeadRoot(), gr)
+	})
+	t.Run("head requested, error path", func(t *testing.T) {
+		resetCfg := features.InitWithReset(&features.Flags{
+			ForceHead: "head",
+		})
+		defer resetCfg()
+		require.Equal(t, service.startupHeadRoot(), gr)
+		require.LogsContain(t, hook, "could not get head block root, starting with finalized block as head")
+	})
+
+	st, _ := util.DeterministicGenesisState(t, 64)
+	hr := [32]byte{'h', 'e', 'a', 'd'}
+	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, st, hr), "Could not save genesis state")
+	require.NoError(t, service.cfg.BeaconDB.SaveHeadBlockRoot(ctx, hr), "Could not save genesis state")
+	require.NoError(t, service.cfg.BeaconDB.SaveHeadBlockRoot(ctx, hr))
+
+	t.Run("start from head", func(t *testing.T) {
+		resetCfg := features.InitWithReset(&features.Flags{
+			ForceHead: "head",
+		})
+		defer resetCfg()
+		require.Equal(t, service.startupHeadRoot(), hr)
+	})
+}
+
+func Test_setupForkchoiceTree_Finalized(t *testing.T) {
+	service, tr := minimalTestService(t)
+	ctx := tr.ctx
+
+	st, _ := util.DeterministicGenesisState(t, 64)
+	stateRoot, err := st.HashTreeRoot(ctx)
+	require.NoError(t, err, "Could not hash genesis state")
+
+	require.NoError(t, service.saveGenesisData(ctx, st))
+
+	genesis := blocks.NewGenesisBlock(stateRoot[:])
+	wsb, err := consensusblocks.NewSignedBeaconBlock(genesis)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb), "Could not save genesis block")
+	parentRoot, err := genesis.Block.HashTreeRoot()
+	require.NoError(t, err, "Could not get signing root")
+	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, st, parentRoot), "Could not save genesis state")
+	require.NoError(t, service.cfg.BeaconDB.SaveHeadBlockRoot(ctx, parentRoot), "Could not save genesis state")
+	require.NoError(t, service.cfg.BeaconDB.SaveJustifiedCheckpoint(ctx, &ethpb.Checkpoint{Root: parentRoot[:]}))
+	require.NoError(t, service.cfg.BeaconDB.SaveFinalizedCheckpoint(ctx, &ethpb.Checkpoint{Root: parentRoot[:]}))
+	require.NoError(t, service.setupForkchoiceTree(st))
+	require.Equal(t, 1, service.cfg.ForkChoiceStore.NodeCount())
+}
+
+func Test_setupForkchoiceTree_Head(t *testing.T) {
+	service, tr := minimalTestService(t)
+	ctx := tr.ctx
+	resetCfg := features.InitWithReset(&features.Flags{
+		ForceHead: "head",
+	})
+	defer resetCfg()
+
+	genesisState, keys := util.DeterministicGenesisState(t, 64)
+	stateRoot, err := genesisState.HashTreeRoot(ctx)
+	require.NoError(t, err, "Could not hash genesis state")
+	genesis := blocks.NewGenesisBlock(stateRoot[:])
+	wsb, err := consensusblocks.NewSignedBeaconBlock(genesis)
+	require.NoError(t, err)
+	genesisRoot, err := genesis.Block.HashTreeRoot()
+	require.NoError(t, err, "Could not get signing root")
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb), "Could not save genesis block")
+	require.NoError(t, service.saveGenesisData(ctx, genesisState))
+
+	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, genesisState, genesisRoot), "Could not save genesis state")
+	require.NoError(t, service.cfg.BeaconDB.SaveHeadBlockRoot(ctx, genesisRoot), "Could not save genesis state")
+
+	st, err := service.HeadState(ctx)
+	require.NoError(t, err)
+	b, err := util.GenerateFullBlock(st, keys, util.DefaultBlockGenConfig(), primitives.Slot(1))
+	require.NoError(t, err)
+	wsb, err = consensusblocks.NewSignedBeaconBlock(b)
+	require.NoError(t, err)
+	root, err := b.Block.HashTreeRoot()
+	require.NoError(t, err)
+	preState, err := service.getBlockPreState(ctx, wsb.Block())
+	require.NoError(t, err)
+	postState, err := service.validateStateTransition(ctx, preState, wsb)
+	require.NoError(t, err)
+	require.NoError(t, service.savePostStateInfo(ctx, root, wsb, postState))
+
+	b, err = util.GenerateFullBlock(postState, keys, util.DefaultBlockGenConfig(), primitives.Slot(2))
+	require.NoError(t, err)
+	wsb, err = consensusblocks.NewSignedBeaconBlock(b)
+	require.NoError(t, err)
+	root, err = b.Block.HashTreeRoot()
+	require.NoError(t, err)
+	require.NoError(t, service.savePostStateInfo(ctx, root, wsb, preState))
+
+	require.NoError(t, service.cfg.BeaconDB.SaveHeadBlockRoot(ctx, root))
+	cp := service.FinalizedCheckpt()
+	fRoot := service.ensureRootNotZeros([32]byte(cp.Root))
+	require.NotEqual(t, fRoot, root)
+	require.Equal(t, root, service.startupHeadRoot())
+	require.NoError(t, service.setupForkchoiceTree(st))
+	require.Equal(t, 2, service.cfg.ForkChoiceStore.NodeCount())
+}
--- a/beacon-chain/builder/BUILD.bazel
+++ b/beacon-chain/builder/BUILD.bazel
@@ -3,6 +3,7 @@ load("@prysm//tools/go:def.bzl", "go_library", "go_test")
 go_library(
    name = "go_default_library",
    srcs = [
+        "log.go",
        "metric.go",
        "option.go",
        "service.go",
--- a/beacon-chain/builder/log.go
+++ b/beacon-chain/builder/log.go
@@ -0,0 +1,5 @@
+package builder
+
+import "github.com/sirupsen/logrus"
+
+var log = logrus.WithField("prefix", "builder")
--- a/beacon-chain/builder/option.go
+++ b/beacon-chain/builder/option.go
@@ -14,10 +14,16 @@ type Option func(s *Service) error
 // FlagOptions for builder service flag configurations.
 func FlagOptions(c *cli.Context) ([]Option, error) {
 	endpoint := c.String(flags.MevRelayEndpoint.Name)
+	sszEnabled := c.Bool(flags.EnableBuilderSSZ.Name)
 	var client *builder.Client
 	if endpoint != "" {
+		var opts []builder.ClientOpt
+		if sszEnabled {
+			log.Info("Using APIs with SSZ enabled")
+			opts = append(opts, builder.WithSSZ())
+		}
 		var err error
-		client, err = builder.NewClient(endpoint)
+		client, err = builder.NewClient(endpoint, opts...)
 		if err != nil {
 			return nil, err
 		}
--- a/beacon-chain/builder/service.go
+++ b/beacon-chain/builder/service.go
@@ -17,7 +17,6 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/monitoring/tracing/trace"
 	v1 "github.com/prysmaticlabs/prysm/v5/proto/engine/v1"
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
-	log "github.com/sirupsen/logrus"
 )

 // ErrNoBuilder is used when builder endpoint is not configured.
--- a/beacon-chain/cache/tracked_validators.go
+++ b/beacon-chain/cache/tracked_validators.go
@@ -25,7 +25,7 @@ type (
 	}

 	TrackedValidatorsCache struct {
-		trackedValidators cache.Cache
+		trackedValidators *cache.Cache
 	}
 )

@@ -50,7 +50,7 @@ var (
 // NewTrackedValidatorsCache creates a new cache for tracking validators.
 func NewTrackedValidatorsCache() *TrackedValidatorsCache {
 	return &TrackedValidatorsCache{
-		trackedValidators: *cache.New(defaultExpiration, cleanupInterval),
+		trackedValidators: cache.New(defaultExpiration, cleanupInterval),
 	}
 }

--- a/beacon-chain/core/altair/attestation.go
+++ b/beacon-chain/core/altair/attestation.go
@@ -66,7 +66,7 @@ func ProcessAttestationNoVerifySignature(
 	if err != nil {
 		return nil, err
 	}
-	committees, err := helpers.AttestationCommittees(ctx, beaconState, att)
+	committees, err := helpers.AttestationCommitteesFromState(ctx, beaconState, att)
 	if err != nil {
 		return nil, err
 	}
--- a/beacon-chain/core/blocks/signature.go
+++ b/beacon-chain/core/blocks/signature.go
@@ -192,7 +192,7 @@ func createAttestationSignatureBatch(
 	descs := make([]string, len(atts))
 	for i, a := range atts {
 		sigs[i] = a.GetSignature()
-		committees, err := helpers.AttestationCommittees(ctx, beaconState, a)
+		committees, err := helpers.AttestationCommitteesFromState(ctx, beaconState, a)
 		if err != nil {
 			return nil, err
 		}
--- a/beacon-chain/core/electra/BUILD.bazel
+++ b/beacon-chain/core/electra/BUILD.bazel
@@ -79,7 +79,6 @@ go_test(
        "//consensus-types/blocks:go_default_library",
        "//consensus-types/primitives:go_default_library",
        "//crypto/bls:go_default_library",
-        "//crypto/bls/common:go_default_library",
        "//encoding/bytesutil:go_default_library",
        "//proto/engine/v1:go_default_library",
        "//proto/prysm/v1alpha1:go_default_library",
--- a/beacon-chain/core/electra/deposits_test.go
+++ b/beacon-chain/core/electra/deposits_test.go
@@ -14,7 +14,6 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/config/params"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
 	"github.com/prysmaticlabs/prysm/v5/crypto/bls"
-	"github.com/prysmaticlabs/prysm/v5/crypto/bls/common"
 	"github.com/prysmaticlabs/prysm/v5/encoding/bytesutil"
 	enginev1 "github.com/prysmaticlabs/prysm/v5/proto/engine/v1"
 	eth "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
@@ -196,7 +195,7 @@ func TestProcessPendingDeposits(t *testing.T) {
 			},
 		},
 		{
-			name: "process excess balance that uses a point to infinity signature, processed as a topup",
+			name: "process excess balance as a topup",
 			state: func() state.BeaconState {
 				excessBalance := uint64(100)
 				st := stateWithActiveBalanceETH(t, 32)
@@ -209,7 +208,6 @@ func TestProcessPendingDeposits(t *testing.T) {
 				validators[0].PublicKey = sk.PublicKey().Marshal()
 				validators[0].WithdrawalCredentials = wc
 				dep := stateTesting.GeneratePendingDeposit(t, sk, excessBalance, bytesutil.ToBytes32(wc), 0)
-				dep.Signature = common.InfiniteSignature[:]
 				require.NoError(t, st.SetValidators(validators))
 				require.NoError(t, st.SetPendingDeposits([]*eth.PendingDeposit{dep}))
 				return st
@@ -558,7 +556,6 @@ func TestApplyPendingDeposit_TopUp(t *testing.T) {
 	validators[0].PublicKey = sk.PublicKey().Marshal()
 	validators[0].WithdrawalCredentials = wc
 	dep := stateTesting.GeneratePendingDeposit(t, sk, excessBalance, bytesutil.ToBytes32(wc), 0)
-	dep.Signature = common.InfiniteSignature[:]
 	require.NoError(t, st.SetValidators(validators))

 	require.NoError(t, electra.ApplyPendingDeposit(context.Background(), st, dep))
--- a/beacon-chain/core/feed/operation/BUILD.bazel
+++ b/beacon-chain/core/feed/operation/BUILD.bazel
@@ -11,6 +11,7 @@ go_library(
    deps = [
        "//async/event:go_default_library",
        "//consensus-types/blocks:go_default_library",
+        "//consensus-types/interfaces:go_default_library",
        "//proto/prysm/v1alpha1:go_default_library",
    ],
 )
--- a/beacon-chain/core/feed/operation/events.go
+++ b/beacon-chain/core/feed/operation/events.go
@@ -3,6 +3,7 @@ package operation

 import (
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
+	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
 )

@@ -35,6 +36,9 @@ const (

 	// SingleAttReceived is sent after a single attestation object is received from gossip or rpc
 	SingleAttReceived = 9
+
+	// BlockGossipReceived is sent after a block has been received from gossip or API that passes validation rules.
+	BlockGossipReceived = 10
 )

 // UnAggregatedAttReceivedData is the data sent with UnaggregatedAttReceived events.
@@ -85,3 +89,9 @@ type AttesterSlashingReceivedData struct {
 type SingleAttReceivedData struct {
 	Attestation ethpb.Att
 }
+
+// BlockGossipReceivedData is the data sent with BlockGossipReceived events.
+type BlockGossipReceivedData struct {
+	// SignedBlock is the block that was received.
+	SignedBlock interfaces.ReadOnlySignedBeaconBlock
+}
--- a/beacon-chain/core/helpers/beacon_committee.go
+++ b/beacon-chain/core/helpers/beacon_committee.go
@@ -30,6 +30,13 @@ var (
 	proposerIndicesCache = cache.NewProposerIndicesCache()
 )

+type beaconCommitteeFunc = func(
+	ctx context.Context,
+	state state.ReadOnlyBeaconState,
+	slot primitives.Slot,
+	committeeIndex primitives.CommitteeIndex,
+) ([]primitives.ValidatorIndex, error)
+
 // SlotCommitteeCount returns the number of beacon committees of a slot. The
 // active validator count is provided as an argument rather than an imported implementation
 // from the spec definition. Having the active validator count as an argument allows for
@@ -59,21 +66,48 @@ func SlotCommitteeCount(activeValidatorCount uint64) uint64 {
 	return committeesPerSlot
 }

-// AttestationCommittees returns beacon state committees that reflect attestation's committee indices.
-func AttestationCommittees(ctx context.Context, st state.ReadOnlyBeaconState, att ethpb.Att) ([][]primitives.ValidatorIndex, error) {
+// AttestationCommitteesFromState returns beacon state committees that reflect attestation's committee indices.
+func AttestationCommitteesFromState(ctx context.Context, st state.ReadOnlyBeaconState, att ethpb.Att) ([][]primitives.ValidatorIndex, error) {
+	return attestationCommittees(ctx, st, att, BeaconCommitteeFromState)
+}
+
+// AttestationCommitteesFromCache has the same functionality as AttestationCommitteesFromState, but only returns a value
+// when all attestation committees are already cached.
+func AttestationCommitteesFromCache(ctx context.Context, st state.ReadOnlyBeaconState, att ethpb.Att) (bool, [][]primitives.ValidatorIndex, error) {
+	committees, err := attestationCommittees(ctx, st, att, BeaconCommitteeFromCache)
+	if err != nil {
+		return false, nil, err
+	}
+	if len(committees) == 0 {
+		return false, nil, nil
+	}
+	for _, c := range committees {
+		if len(c) == 0 {
+			return false, nil, nil
+		}
+	}
+	return true, committees, nil
+}
+
+func attestationCommittees(
+	ctx context.Context,
+	st state.ReadOnlyBeaconState,
+	att ethpb.Att,
+	committeeFunc beaconCommitteeFunc,
+) ([][]primitives.ValidatorIndex, error) {
 	var committees [][]primitives.ValidatorIndex
 	if att.Version() >= version.Electra {
 		committeeIndices := att.CommitteeBitsVal().BitIndices()
 		committees = make([][]primitives.ValidatorIndex, len(committeeIndices))
 		for i, ci := range committeeIndices {
-			committee, err := BeaconCommitteeFromState(ctx, st, att.GetData().Slot, primitives.CommitteeIndex(ci))
+			committee, err := committeeFunc(ctx, st, att.GetData().Slot, primitives.CommitteeIndex(ci))
 			if err != nil {
 				return nil, err
 			}
 			committees[i] = committee
 		}
 	} else {
-		committee, err := BeaconCommitteeFromState(ctx, st, att.GetData().Slot, att.GetData().CommitteeIndex)
+		committee, err := committeeFunc(ctx, st, att.GetData().Slot, att.GetData().CommitteeIndex)
 		if err != nil {
 			return nil, err
 		}
@@ -164,6 +198,27 @@ func BeaconCommitteeFromState(ctx context.Context, state state.ReadOnlyBeaconSta
 	return BeaconCommittee(ctx, activeIndices, seed, slot, committeeIndex)
 }

+// BeaconCommitteeFromCache has the same functionality as BeaconCommitteeFromState, but only returns a value
+// when the committee is already cached.
+func BeaconCommitteeFromCache(
+	ctx context.Context,
+	state state.ReadOnlyBeaconState,
+	slot primitives.Slot,
+	committeeIndex primitives.CommitteeIndex,
+) ([]primitives.ValidatorIndex, error) {
+	epoch := slots.ToEpoch(slot)
+	seed, err := Seed(state, epoch, params.BeaconConfig().DomainBeaconAttester)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not get seed")
+	}
+
+	committee, err := committeeCache.Committee(ctx, slot, seed, committeeIndex)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not interface with committee cache")
+	}
+	return committee, nil
+}
+
 // BeaconCommittee returns the beacon committee of a given slot and committee index. The
 // validator indices and seed are provided as an argument rather than an imported implementation
 // from the spec definition. Having them as an argument allows for cheaper computation run time.
--- a/beacon-chain/core/helpers/beacon_committee_test.go
+++ b/beacon-chain/core/helpers/beacon_committee_test.go
@@ -729,7 +729,9 @@ func TestCommitteeIndices(t *testing.T) {
 	assert.DeepEqual(t, []primitives.CommitteeIndex{0, 1, 3}, indices)
 }

-func TestAttestationCommittees(t *testing.T) {
+func TestAttestationCommitteesFromState(t *testing.T) {
+	ctx := context.Background()
+
 	validators := make([]*ethpb.Validator, params.BeaconConfig().SlotsPerEpoch.Mul(params.BeaconConfig().TargetCommitteeSize))
 	for i := 0; i < len(validators); i++ {
 		validators[i] = &ethpb.Validator{
@@ -745,7 +747,7 @@ func TestAttestationCommittees(t *testing.T) {

 	t.Run("pre-Electra", func(t *testing.T) {
 		att := &ethpb.Attestation{Data: &ethpb.AttestationData{CommitteeIndex: 0}}
-		committees, err := helpers.AttestationCommittees(context.Background(), state, att)
+		committees, err := helpers.AttestationCommitteesFromState(ctx, state, att)
 		require.NoError(t, err)
 		require.Equal(t, 1, len(committees))
 		assert.Equal(t, params.BeaconConfig().TargetCommitteeSize, uint64(len(committees[0])))
@@ -755,7 +757,7 @@ func TestAttestationCommittees(t *testing.T) {
 		bits.SetBitAt(0, true)
 		bits.SetBitAt(1, true)
 		att := &ethpb.AttestationElectra{CommitteeBits: bits, Data: &ethpb.AttestationData{}}
-		committees, err := helpers.AttestationCommittees(context.Background(), state, att)
+		committees, err := helpers.AttestationCommitteesFromState(ctx, state, att)
 		require.NoError(t, err)
 		require.Equal(t, 2, len(committees))
 		assert.Equal(t, params.BeaconConfig().TargetCommitteeSize, uint64(len(committees[0])))
@@ -763,9 +765,58 @@ func TestAttestationCommittees(t *testing.T) {
 	})
 }

-func TestBeaconCommittees(t *testing.T) {
-	prevConfig := params.BeaconConfig().Copy()
-	defer params.OverrideBeaconConfig(prevConfig)
+func TestAttestationCommitteesFromCache(t *testing.T) {
+	ctx := context.Background()
+
+	validators := make([]*ethpb.Validator, params.BeaconConfig().SlotsPerEpoch.Mul(params.BeaconConfig().TargetCommitteeSize))
+	for i := 0; i < len(validators); i++ {
+		validators[i] = &ethpb.Validator{
+			ExitEpoch: params.BeaconConfig().FarFutureEpoch,
+		}
+	}
+
+	state, err := state_native.InitializeFromProtoPhase0(&ethpb.BeaconState{
+		Validators:  validators,
+		RandaoMixes: make([][]byte, params.BeaconConfig().EpochsPerHistoricalVector),
+	})
+	require.NoError(t, err)
+
+	t.Run("pre-Electra", func(t *testing.T) {
+		helpers.ClearCache()
+		att := &ethpb.Attestation{Data: &ethpb.AttestationData{CommitteeIndex: 0}}
+		ok, _, err := helpers.AttestationCommitteesFromCache(ctx, state, att)
+		require.NoError(t, err)
+		require.Equal(t, false, ok)
+		require.NoError(t, helpers.UpdateCommitteeCache(ctx, state, 0))
+		ok, committees, err := helpers.AttestationCommitteesFromCache(ctx, state, att)
+		require.NoError(t, err)
+		require.Equal(t, true, ok)
+		require.Equal(t, 1, len(committees))
+		assert.Equal(t, params.BeaconConfig().TargetCommitteeSize, uint64(len(committees[0])))
+	})
+	t.Run("post-Electra", func(t *testing.T) {
+		helpers.ClearCache()
+		bits := primitives.NewAttestationCommitteeBits()
+		bits.SetBitAt(0, true)
+		bits.SetBitAt(1, true)
+		att := &ethpb.AttestationElectra{CommitteeBits: bits, Data: &ethpb.AttestationData{}}
+		ok, _, err := helpers.AttestationCommitteesFromCache(ctx, state, att)
+		require.NoError(t, err)
+		require.Equal(t, false, ok)
+		require.NoError(t, helpers.UpdateCommitteeCache(ctx, state, 0))
+		ok, committees, err := helpers.AttestationCommitteesFromCache(ctx, state, att)
+		require.NoError(t, err)
+		require.Equal(t, true, ok)
+		require.Equal(t, 2, len(committees))
+		assert.Equal(t, params.BeaconConfig().TargetCommitteeSize, uint64(len(committees[0])))
+		assert.Equal(t, params.BeaconConfig().TargetCommitteeSize, uint64(len(committees[1])))
+	})
+}
+
+func TestBeaconCommitteesFromState(t *testing.T) {
+	ctx := context.Background()
+
+	params.SetupTestConfigCleanup(t)
 	c := params.BeaconConfig().Copy()
 	c.MinGenesisActiveValidatorCount = 128
 	c.SlotsPerEpoch = 4
@@ -774,15 +825,49 @@ func TestBeaconCommittees(t *testing.T) {

 	state, _ := util.DeterministicGenesisState(t, 256)

-	activeCount, err := helpers.ActiveValidatorCount(context.Background(), state, 0)
+	activeCount, err := helpers.ActiveValidatorCount(ctx, state, 0)
 	require.NoError(t, err)
 	committeesPerSlot := helpers.SlotCommitteeCount(activeCount)
-	committees, err := helpers.BeaconCommittees(context.Background(), state, 0)
+	committees, err := helpers.BeaconCommittees(ctx, state, 0)
 	require.NoError(t, err)
 	require.Equal(t, committeesPerSlot, uint64(len(committees)))
 	for idx := primitives.CommitteeIndex(0); idx < primitives.CommitteeIndex(len(committees)); idx++ {
-		committee, err := helpers.BeaconCommitteeFromState(context.Background(), state, 0, idx)
+		committee, err := helpers.BeaconCommitteeFromState(ctx, state, 0, idx)
 		require.NoError(t, err)
-		require.DeepEqual(t, committees[idx], committee)
+		assert.DeepEqual(t, committees[idx], committee)
+	}
+}
+
+func TestBeaconCommitteesFromCache(t *testing.T) {
+	ctx := context.Background()
+
+	params.SetupTestConfigCleanup(t)
+	c := params.BeaconConfig().Copy()
+	c.MinGenesisActiveValidatorCount = 128
+	c.SlotsPerEpoch = 4
+	c.TargetCommitteeSize = 16
+	params.OverrideBeaconConfig(c)
+
+	state, _ := util.DeterministicGenesisState(t, 256)
+
+	activeCount, err := helpers.ActiveValidatorCount(ctx, state, 0)
+	require.NoError(t, err)
+	committeesPerSlot := helpers.SlotCommitteeCount(activeCount)
+	committees, err := helpers.BeaconCommittees(ctx, state, 0)
+	require.NoError(t, err)
+	require.Equal(t, committeesPerSlot, uint64(len(committees)))
+
+	helpers.ClearCache()
+	for idx := primitives.CommitteeIndex(0); idx < primitives.CommitteeIndex(len(committees)); idx++ {
+		committee, err := helpers.BeaconCommitteeFromCache(ctx, state, 0, idx)
+		require.NoError(t, err)
+		assert.Equal(t, 0, len(committee))
+	}
+
+	require.NoError(t, helpers.UpdateCommitteeCache(ctx, state, 0))
+	for idx := primitives.CommitteeIndex(0); idx < primitives.CommitteeIndex(len(committees)); idx++ {
+		committee, err := helpers.BeaconCommitteeFromCache(ctx, state, 0, idx)
+		require.NoError(t, err)
+		assert.DeepEqual(t, committees[idx], committee)
 	}
 }
--- a/beacon-chain/db/iface/interface.go
+++ b/beacon-chain/db/iface/interface.go
@@ -101,7 +101,7 @@ type NoHeadAccessDatabase interface {
 	SaveLightClientBootstrap(ctx context.Context, blockRoot []byte, bootstrap interfaces.LightClientBootstrap) error

 	CleanUpDirtyStates(ctx context.Context, slotsPerArchivedPoint primitives.Slot) error
-	DeleteHistoricalDataBeforeSlot(ctx context.Context, slot primitives.Slot) error
+	DeleteHistoricalDataBeforeSlot(ctx context.Context, slot primitives.Slot, batchSize int) (int, error)
 }

 // HeadAccessDatabase defines a struct with access to reading chain head data.
@@ -110,6 +110,7 @@ type HeadAccessDatabase interface {

 	// Block related methods.
 	HeadBlock(ctx context.Context) (interfaces.ReadOnlySignedBeaconBlock, error)
+	HeadBlockRoot() ([32]byte, error)
 	SaveHeadBlockRoot(ctx context.Context, blockRoot [32]byte) error

 	// Genesis operations.
--- a/beacon-chain/db/kv/archived_point.go
+++ b/beacon-chain/db/kv/archived_point.go
@@ -35,7 +35,7 @@ func (s *Store) LastArchivedRoot(ctx context.Context) [32]byte {
 		_, blockRoot = bkt.Cursor().Last()
 		return nil
 	}); err != nil { // This view never returns an error, but we'll handle anyway for sanity.
-		panic(err)
+		panic(err) // lint:nopanic -- View never returns an error.
 	}

 	return bytesutil.ToBytes32(blockRoot)
@@ -53,7 +53,7 @@ func (s *Store) ArchivedPointRoot(ctx context.Context, slot primitives.Slot) [32
 		blockRoot = bucket.Get(bytesutil.SlotToBytesBigEndian(slot))
 		return nil
 	}); err != nil { // This view never returns an error, but we'll handle anyway for sanity.
-		panic(err)
+		panic(err) // lint:nopanic -- View never returns an error.
 	}

 	return bytesutil.ToBytes32(blockRoot)
@@ -69,7 +69,7 @@ func (s *Store) HasArchivedPoint(ctx context.Context, slot primitives.Slot) bool
 		exists = iBucket.Get(bytesutil.SlotToBytesBigEndian(slot)) != nil
 		return nil
 	}); err != nil { // This view never returns an error, but we'll handle anyway for sanity.
-		panic(err)
+		panic(err) // lint:nopanic -- View never returns an error.
 	}
 	return exists
 }
--- a/beacon-chain/db/kv/blocks.go
+++ b/beacon-chain/db/kv/blocks.go
@@ -30,22 +30,32 @@ var errInvalidSlotRange = errors.New("invalid end slot and start slot provided")
 func (s *Store) Block(ctx context.Context, blockRoot [32]byte) (interfaces.ReadOnlySignedBeaconBlock, error) {
 	ctx, span := trace.StartSpan(ctx, "BeaconDB.Block")
 	defer span.End()
-	// Return block from cache if it exists.
+	blk, err := s.getBlock(ctx, blockRoot, nil)
+	if errors.Is(err, ErrNotFound) {
+		return nil, nil
+	}
+	return blk, err
+}
+
+func (s *Store) getBlock(ctx context.Context, blockRoot [32]byte, tx *bolt.Tx) (interfaces.ReadOnlySignedBeaconBlock, error) {
 	if v, ok := s.blockCache.Get(string(blockRoot[:])); v != nil && ok {
 		return v.(interfaces.ReadOnlySignedBeaconBlock), nil
 	}
-	var blk interfaces.ReadOnlySignedBeaconBlock
-	err := s.db.View(func(tx *bolt.Tx) error {
-		bkt := tx.Bucket(blocksBucket)
-		enc := bkt.Get(blockRoot[:])
-		if enc == nil {
-			return nil
-		}
+	// This method allows the caller to pass in its tx if one is already open.
+	// Or if a nil value is used, a transaction will be managed intenally.
+	if tx == nil {
 		var err error
-		blk, err = unmarshalBlock(ctx, enc)
-		return err
-	})
-	return blk, err
+		tx, err = s.db.Begin(false)
+		if err != nil {
+			return nil, err
+		}
+		defer func() {
+			if err := tx.Rollback(); err != nil {
+				log.WithError(err).Error("could not rollback read-only getBlock transaction")
+			}
+		}()
+	}
+	return unmarshalBlock(ctx, tx.Bucket(blocksBucket).Get(blockRoot[:]))
 }

 // OriginCheckpointBlockRoot returns the value written to the db in SaveOriginCheckpointBlockRoot
@@ -70,6 +80,21 @@ func (s *Store) OriginCheckpointBlockRoot(ctx context.Context) ([32]byte, error)
 	return root, err
 }

+// HeadBlockRoot returns the latest canonical block root in the Ethereum Beacon Chain.
+func (s *Store) HeadBlockRoot() ([32]byte, error) {
+	var root [32]byte
+	err := s.db.View(func(tx *bolt.Tx) error {
+		bkt := tx.Bucket(blocksBucket)
+		headRoot := bkt.Get(headBlockRootKey)
+		if len(headRoot) == 0 {
+			return errors.New("no head block root found")
+		}
+		copy(root[:], headRoot)
+		return nil
+	})
+	return root, err
+}
+
 // HeadBlock returns the latest canonical block in the Ethereum Beacon Chain.
 func (s *Store) HeadBlock(ctx context.Context) (interfaces.ReadOnlySignedBeaconBlock, error) {
 	ctx, span := trace.StartSpan(ctx, "BeaconDB.HeadBlock")
@@ -160,7 +185,7 @@ func (s *Store) HasBlock(ctx context.Context, blockRoot [32]byte) bool {
 		exists = bkt.Get(blockRoot[:]) != nil
 		return nil
 	}); err != nil { // This view never returns an error, but we'll handle anyway for sanity.
-		panic(err)
+		panic(err) // lint:nopanic -- View never returns an error.
 	}
 	return exists
 }
@@ -227,6 +252,21 @@ func (s *Store) DeleteBlock(ctx context.Context, root [32]byte) error {
 			return ErrDeleteJustifiedAndFinalized
 		}

+		// Look up the block to find its slot; needed to remove the slot index entry.
+		blk, err := s.getBlock(ctx, root, tx)
+		if err != nil {
+			// getBlock can return ErrNotFound, in which case we won't even try to delete it.
+			if errors.Is(err, ErrNotFound) {
+				return nil
+			}
+			return err
+		}
+		if err := s.deleteSlotIndexEntry(tx, blk.Block().Slot(), root); err != nil {
+			return err
+		}
+		if err := s.deleteMatchingParentIndex(tx, blk.Block().ParentRoot(), root); err != nil {
+			return err
+		}
 		if err := s.deleteBlock(tx, root[:]); err != nil {
 			return err
 		}
@@ -245,77 +285,82 @@ func (s *Store) DeleteBlock(ctx context.Context, root [32]byte) error {
 // - blockRootValidatorHashesBucket
 // - blockSlotIndicesBucket
 // - stateSlotIndicesBucket
-func (s *Store) DeleteHistoricalDataBeforeSlot(ctx context.Context, cutoffSlot primitives.Slot) error {
+func (s *Store) DeleteHistoricalDataBeforeSlot(ctx context.Context, cutoffSlot primitives.Slot, batchSize int) (int, error) {
 	ctx, span := trace.StartSpan(ctx, "BeaconDB.DeleteHistoricalDataBeforeSlot")
 	defer span.End()

 	// Collect slot/root pairs to perform deletions in a separate read only transaction.
-	var (
-		roots [][]byte
-		slts  []primitives.Slot
-	)
-	err := s.db.View(func(tx *bolt.Tx) error {
-		var err error
-		roots, slts, err = blockRootsBySlotRange(ctx, tx.Bucket(blockSlotIndicesBucket), primitives.Slot(0), cutoffSlot, nil, nil, nil)
-		if err != nil {
-			return errors.Wrap(err, "could not retrieve block roots")
-		}
-		return nil
-	})
+	slotRoots, err := s.slotRootsInRange(ctx, primitives.Slot(0), cutoffSlot, batchSize)
 	if err != nil {
-		return errors.Wrap(err, "could not retrieve block roots and slots")
+		return 0, err
+	}
+
+	// Return early if there's nothing to delete.
+	if len(slotRoots) == 0 {
+		return 0, nil
 	}

 	// Perform all deletions in a single transaction for atomicity
-	return s.db.Update(func(tx *bolt.Tx) error {
-		for _, root := range roots {
+	var numSlotsDeleted int
+	err = s.db.Update(func(tx *bolt.Tx) error {
+		for _, sr := range slotRoots {
+			// Return if context is cancelled or deadline is exceeded.
+			if ctx.Err() != nil {
+				//nolint:nilerr
+				return nil
+			}
+
 			// Delete block
-			if err = s.deleteBlock(tx, root); err != nil {
+			if err = s.deleteBlock(tx, sr.root[:]); err != nil {
 				return err
 			}

 			// Delete finalized block roots index
-			if err = tx.Bucket(finalizedBlockRootsIndexBucket).Delete(root); err != nil {
+			if err = tx.Bucket(finalizedBlockRootsIndexBucket).Delete(sr.root[:]); err != nil {
 				return errors.Wrap(err, "could not delete finalized block root index")
 			}

 			// Delete state
-			if err = tx.Bucket(stateBucket).Delete(root); err != nil {
+			if err = tx.Bucket(stateBucket).Delete(sr.root[:]); err != nil {
 				return errors.Wrap(err, "could not delete state")
 			}

 			// Delete state summary
-			if err = tx.Bucket(stateSummaryBucket).Delete(root); err != nil {
+			if err = tx.Bucket(stateSummaryBucket).Delete(sr.root[:]); err != nil {
 				return errors.Wrap(err, "could not delete state summary")
 			}

 			// Delete validator entries
-			if err = s.deleteValidatorHashes(tx, root); err != nil {
+			if err = s.deleteValidatorHashes(tx, sr.root[:]); err != nil {
 				return errors.Wrap(err, "could not delete validators")
 			}
+
+			numSlotsDeleted++
 		}

-		for _, slot := range slts {
+		for _, sr := range slotRoots {
 			// Delete slot indices
-			if err = tx.Bucket(blockSlotIndicesBucket).Delete(bytesutil.SlotToBytesBigEndian(slot)); err != nil {
+			if err = tx.Bucket(blockSlotIndicesBucket).Delete(bytesutil.SlotToBytesBigEndian(sr.slot)); err != nil {
 				return errors.Wrap(err, "could not delete block slot index")
 			}
-			if err = tx.Bucket(stateSlotIndicesBucket).Delete(bytesutil.SlotToBytesBigEndian(slot)); err != nil {
+			if err = tx.Bucket(stateSlotIndicesBucket).Delete(bytesutil.SlotToBytesBigEndian(sr.slot)); err != nil {
 				return errors.Wrap(err, "could not delete state slot index")
 			}
 		}

 		// Delete all caches after we have deleted everything from buckets.
 		// This is done after the buckets are deleted to avoid any issues in case of transaction rollback.
-		for _, root := range roots {
+		for _, sr := range slotRoots {
 			// Delete block from cache
-			s.blockCache.Del(string(root))
+			s.blockCache.Del(string(sr.root[:]))
 			// Delete state summary from cache
-			s.stateSummaryCache.delete([32]byte(root))
+			s.stateSummaryCache.delete(sr.root)
 		}

 		return nil
 	})
+
+	return numSlotsDeleted, err
 }

 // SaveBlock to the db.
@@ -336,7 +381,7 @@ func (s *Store) SaveBlock(ctx context.Context, signed interfaces.ReadOnlySignedB
 // if a `saveBlindedBeaconBlocks` key exists in the database. Otherwise, we check if the last
 // blocked stored to check if it is blinded, and then write that `saveBlindedBeaconBlocks` key
 // to the DB for future checks.
-func (s *Store) shouldSaveBlinded(ctx context.Context) (bool, error) {
+func (s *Store) shouldSaveBlinded() (bool, error) {
 	var saveBlinded bool
 	if err := s.db.View(func(tx *bolt.Tx) error {
 		metadataBkt := tx.Bucket(chainMetadataBucket)
@@ -398,7 +443,7 @@ func prepareBlockBatch(blks []blocks.ROBlock, shouldBlind bool) ([]blockBatchEnt
 }

 func (s *Store) SaveROBlocks(ctx context.Context, blks []blocks.ROBlock, cache bool) error {
-	shouldBlind, err := s.shouldSaveBlinded(ctx)
+	shouldBlind, err := s.shouldSaveBlinded()
 	if err != nil {
 		return err
 	}
@@ -669,6 +714,49 @@ func (s *Store) SaveRegistrationsByValidatorIDs(ctx context.Context, ids []primi
 	})
 }

+type slotRoot struct {
+	slot primitives.Slot
+	root [32]byte
+}
+
+// slotRootsInRange returns slot and block root pairs of length min(batchSize, end-slot)
+func (s *Store) slotRootsInRange(ctx context.Context, start, end primitives.Slot, batchSize int) ([]slotRoot, error) {
+	_, span := trace.StartSpan(ctx, "BeaconDB.slotRootsInRange")
+	defer span.End()
+	if end < start {
+		return nil, errInvalidSlotRange
+	}
+
+	var pairs []slotRoot
+	key := bytesutil.SlotToBytesBigEndian(end)
+	err := s.db.View(func(tx *bolt.Tx) error {
+		bkt := tx.Bucket(blockSlotIndicesBucket)
+		c := bkt.Cursor()
+		for k, v := c.Seek(key); k != nil; k, v = c.Prev() {
+			slot := bytesutil.BytesToSlotBigEndian(k)
+			if slot > end {
+				continue // Seek will seek to the next key *after* the given one if not present
+			}
+			if slot < start {
+				return nil
+			}
+			roots, err := splitRoots(v)
+			if err != nil {
+				return errors.Wrapf(err, "corrupt value %v in block slot index for slot=%d", v, slot)
+			}
+			for _, r := range roots {
+				pairs = append(pairs, slotRoot{slot: slot, root: r})
+			}
+			if len(pairs) >= batchSize {
+				return nil // allows code to easily cap the number of items pruned
+			}
+		}
+		return nil
+	})
+
+	return pairs, err
+}
+
 // blockRootsByFilter retrieves the block roots given the filter criteria.
 func blockRootsByFilter(ctx context.Context, tx *bolt.Tx, f *filters.QueryFilter) ([][]byte, error) {
 	ctx, span := trace.StartSpan(ctx, "BeaconDB.blockRootsByFilter")
@@ -689,7 +777,7 @@ func blockRootsByFilter(ctx context.Context, tx *bolt.Tx, f *filters.QueryFilter

 	// We retrieve block roots that match a filter criteria of slot ranges, if specified.
 	filtersMap := f.Filters()
-	rootsBySlotRange, _, err := blockRootsBySlotRange(
+	rootsBySlotRange, err := blockRootsBySlotRange(
 		ctx,
 		tx.Bucket(blockSlotIndicesBucket),
 		filtersMap[filters.StartSlot],
@@ -734,13 +822,13 @@ func blockRootsBySlotRange(
 	ctx context.Context,
 	bkt *bolt.Bucket,
 	startSlotEncoded, endSlotEncoded, startEpochEncoded, endEpochEncoded, slotStepEncoded interface{},
-) ([][]byte, []primitives.Slot, error) {
+) ([][]byte, error) {
 	_, span := trace.StartSpan(ctx, "BeaconDB.blockRootsBySlotRange")
 	defer span.End()

 	// Return nothing when all slot parameters are missing
 	if startSlotEncoded == nil && endSlotEncoded == nil && startEpochEncoded == nil && endEpochEncoded == nil {
-		return [][]byte{}, nil, nil
+		return [][]byte{}, nil
 	}

 	var startSlot, endSlot primitives.Slot
@@ -761,11 +849,11 @@ func blockRootsBySlotRange(
 	if startEpochOk && endEpochOk {
 		startSlot, err = slots.EpochStart(startEpoch)
 		if err != nil {
-			return nil, nil, err
+			return nil, err
 		}
 		endSlot, err = slots.EpochStart(endEpoch)
 		if err != nil {
-			return nil, nil, err
+			return nil, err
 		}
 		endSlot = endSlot + params.BeaconConfig().SlotsPerEpoch - 1
 	}
@@ -776,11 +864,10 @@ func blockRootsBySlotRange(
 		return key != nil && bytes.Compare(key, max) <= 0
 	}
 	if endSlot < startSlot {
-		return nil, nil, errInvalidSlotRange
+		return nil, errInvalidSlotRange
 	}
 	rootsRange := endSlot.SubSlot(startSlot).Div(step)
 	roots := make([][]byte, 0, rootsRange)
-	var slts []primitives.Slot
 	c := bkt.Cursor()
 	for k, v := c.Seek(min); conditional(k, max); k, v = c.Next() {
 		slot := bytesutil.BytesToSlotBigEndian(k)
@@ -795,9 +882,8 @@ func blockRootsBySlotRange(
 			splitRoots = append(splitRoots, v[i:i+32])
 		}
 		roots = append(roots, splitRoots...)
-		slts = append(slts, slot)
 	}
-	return roots, slts, nil
+	return roots, nil
 }

 // blockRootsBySlot retrieves the block roots by slot
@@ -853,6 +939,9 @@ func createBlockIndicesFromFilters(ctx context.Context, f *filters.QueryFilter)

 // unmarshal block from marshaled proto beacon block bytes to versioned beacon block struct type.
 func unmarshalBlock(_ context.Context, enc []byte) (interfaces.ReadOnlySignedBeaconBlock, error) {
+	if len(enc) == 0 {
+		return nil, errors.Wrap(ErrNotFound, "empty block bytes in db")
+	}
 	var err error
 	enc, err = snappy.Decode(nil, enc)
 	if err != nil {
@@ -1004,6 +1093,47 @@ func (s *Store) deleteBlock(tx *bolt.Tx, root []byte) error {
 	return nil
 }

+func (s *Store) deleteMatchingParentIndex(tx *bolt.Tx, parent, child [32]byte) error {
+	bkt := tx.Bucket(blockParentRootIndicesBucket)
+	if err := deleteRootIndexEntry(bkt, parent[:], child); err != nil {
+		return errors.Wrap(err, "could not delete parent root index entry")
+	}
+	return nil
+}
+
+func (s *Store) deleteSlotIndexEntry(tx *bolt.Tx, slot primitives.Slot, root [32]byte) error {
+	key := bytesutil.SlotToBytesBigEndian(slot)
+	bkt := tx.Bucket(blockSlotIndicesBucket)
+	if err := deleteRootIndexEntry(bkt, key, root); err != nil {
+		return errors.Wrap(err, "could not delete slot index entry")
+	}
+	return nil
+}
+
+func deleteRootIndexEntry(bkt *bolt.Bucket, key []byte, root [32]byte) error {
+	packed := bkt.Get(key)
+	if len(packed) == 0 {
+		return nil
+	}
+	updated, err := removeRoot(packed, root)
+	if err != nil {
+		return err
+	}
+	// Don't update the value if the root was not found.
+	if bytes.Equal(updated, packed) {
+		return nil
+	}
+	// If there are no other roots in the key, just delete it.
+	if len(updated) == 0 {
+		if err := bkt.Delete(key); err != nil {
+			return err
+		}
+		return nil
+	}
+	// Update the key with the root removed.
+	return bkt.Put(key, updated)
+}
+
 func (s *Store) deleteValidatorHashes(tx *bolt.Tx, root []byte) error {
 	ok, err := s.isStateValidatorMigrationOver()
 	if err != nil {
--- a/beacon-chain/db/kv/blocks_test.go
+++ b/beacon-chain/db/kv/blocks_test.go
@@ -196,9 +196,13 @@ func TestStore_BlocksCRUD(t *testing.T) {
 			blockRoot, err := blk.Block().HashTreeRoot()
 			require.NoError(t, err)

+			_, err = db.getBlock(ctx, blockRoot, nil)
+			require.ErrorIs(t, err, ErrNotFound)
 			retrievedBlock, err := db.Block(ctx, blockRoot)
 			require.NoError(t, err)
 			assert.DeepEqual(t, nil, retrievedBlock, "Expected nil block")
+			_, err = db.getBlock(ctx, blockRoot, nil)
+			require.ErrorIs(t, err, ErrNotFound)

 			require.NoError(t, db.SaveBlock(ctx, blk))
 			assert.Equal(t, true, db.HasBlock(ctx, blockRoot), "Expected block to exist in the db")
@@ -214,10 +218,34 @@ func TestStore_BlocksCRUD(t *testing.T) {
 			retrievedPb, err := retrievedBlock.Proto()
 			require.NoError(t, err)
 			assert.Equal(t, true, proto.Equal(wantedPb, retrievedPb), "Wanted: %v, received: %v", wanted, retrievedBlock)
+			// Check that the block is in the slot->block index
+			found, roots, err := db.BlockRootsBySlot(ctx, blk.Block().Slot())
+			require.NoError(t, err)
+			require.Equal(t, true, found)
+			require.Equal(t, 1, len(roots))
+			require.Equal(t, blockRoot, roots[0])
+			// Delete the block, then check that it is no longer in the index.
+
+			parent := blk.Block().ParentRoot()
+			testCheckParentIndices(t, db.db, parent, true)
+			require.NoError(t, db.DeleteBlock(ctx, blockRoot))
+			require.NoError(t, err)
+			testCheckParentIndices(t, db.db, parent, false)
+			found, roots, err = db.BlockRootsBySlot(ctx, blk.Block().Slot())
+			require.NoError(t, err)
+			require.Equal(t, false, found)
+			require.Equal(t, 0, len(roots))
 		})
 	}
 }

+func testCheckParentIndices(t *testing.T, db *bolt.DB, parent [32]byte, expected bool) {
+	require.NoError(t, db.View(func(tx *bolt.Tx) error {
+		require.Equal(t, expected, tx.Bucket(blockParentRootIndicesBucket).Get(parent[:]) != nil)
+		return nil
+	}))
+}
+
 func TestStore_BlocksHandleZeroCase(t *testing.T) {
 	for _, tt := range blockTests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -359,184 +387,221 @@ func TestStore_DeleteFinalizedBlock(t *testing.T) {

 func TestStore_HistoricalDataBeforeSlot(t *testing.T) {
 	slotsPerEpoch := uint64(params.BeaconConfig().SlotsPerEpoch)
-	db := setupDB(t)
 	ctx := context.Background()

-	// Save genesis block root
-	require.NoError(t, db.SaveGenesisBlockRoot(ctx, genesisBlockRoot))
+	tests := []struct {
+		name             string
+		batchSize        int
+		numOfEpochs      uint64
+		deleteBeforeSlot uint64
+	}{
+		{
+			name:             "batchSize less than delete range",
+			batchSize:        10,
+			numOfEpochs:      4,
+			deleteBeforeSlot: 25,
+		},
+		{
+			name:             "batchSize greater than delete range",
+			batchSize:        30,
+			numOfEpochs:      4,
+			deleteBeforeSlot: 15,
+		},
+	}

-	// Create and save blocks for 4 epochs
-	blks := makeBlocks(t, 0, slotsPerEpoch*4, genesisBlockRoot)
-	require.NoError(t, db.SaveBlocks(ctx, blks))
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			db := setupDB(t)
+			// Save genesis block root
+			require.NoError(t, db.SaveGenesisBlockRoot(ctx, genesisBlockRoot))

-	// Mark state validator migration as complete
-	err := db.db.Update(func(tx *bolt.Tx) error {
-		return tx.Bucket(migrationsBucket).Put(migrationStateValidatorsKey, migrationCompleted)
-	})
-	require.NoError(t, err)
+			// Create and save blocks for given epochs
+			blks := makeBlocks(t, 0, slotsPerEpoch*tt.numOfEpochs, genesisBlockRoot)
+			require.NoError(t, db.SaveBlocks(ctx, blks))

-	migrated, err := db.isStateValidatorMigrationOver()
-	require.NoError(t, err)
-	require.Equal(t, true, migrated)
+			// Mark state validator migration as complete
+			err := db.db.Update(func(tx *bolt.Tx) error {
+				return tx.Bucket(migrationsBucket).Put(migrationStateValidatorsKey, migrationCompleted)
+			})
+			require.NoError(t, err)

-	// Create state summaries and states for each block
-	ss := make([]*ethpb.StateSummary, len(blks))
-	states := make([]state.BeaconState, len(blks))
+			migrated, err := db.isStateValidatorMigrationOver()
+			require.NoError(t, err)
+			require.Equal(t, true, migrated)

-	for i, blk := range blks {
-		slot := blk.Block().Slot()
-		r, err := blk.Block().HashTreeRoot()
-		require.NoError(t, err)
+			// Create state summaries and states for each block
+			ss := make([]*ethpb.StateSummary, len(blks))
+			states := make([]state.BeaconState, len(blks))

-		// Create and save state summary
-		ss[i] = &ethpb.StateSummary{
-			Slot: slot,
-			Root: r[:],
-		}
+			for i, blk := range blks {
+				slot := blk.Block().Slot()
+				r, err := blk.Block().HashTreeRoot()
+				require.NoError(t, err)

-		// Create and save state with validator entries
-		vals := make([]*ethpb.Validator, 2)
-		for j := range vals {
-			vals[j] = &ethpb.Validator{
-				PublicKey:             bytesutil.PadTo([]byte{byte(i*j + 1)}, 48),
-				WithdrawalCredentials: bytesutil.PadTo([]byte{byte(i*j + 2)}, 32),
+				// Create and save state summary
+				ss[i] = &ethpb.StateSummary{
+					Slot: slot,
+					Root: r[:],
+				}
+
+				// Create and save state with validator entries
+				vals := make([]*ethpb.Validator, 2)
+				for j := range vals {
+					vals[j] = &ethpb.Validator{
+						PublicKey:             bytesutil.PadTo([]byte{byte(i*j + 1)}, 48),
+						WithdrawalCredentials: bytesutil.PadTo([]byte{byte(i*j + 2)}, 32),
+					}
+				}
+
+				st, err := util.NewBeaconState(func(state *ethpb.BeaconState) error {
+					state.Validators = vals
+					state.Slot = slot
+					return nil
+				})
+				require.NoError(t, err)
+				require.NoError(t, db.SaveState(ctx, st, r))
+				states[i] = st
+
+				// Verify validator entries are saved to db
+				valsActual, err := db.validatorEntries(ctx, r)
+				require.NoError(t, err)
+				for j, val := range valsActual {
+					require.DeepEqual(t, vals[j], val)
+				}
 			}
-		}
+			require.NoError(t, db.SaveStateSummaries(ctx, ss))

-		st, err := util.NewBeaconState(func(state *ethpb.BeaconState) error {
-			state.Validators = vals
-			state.Slot = slot
-			return nil
-		})
-		require.NoError(t, err)
-		require.NoError(t, db.SaveState(ctx, st, r))
-		states[i] = st
-
-		// Verify validator entries are saved to db
-		valsActual, err := db.validatorEntries(ctx, r)
-		require.NoError(t, err)
-		for j, val := range valsActual {
-			require.DeepEqual(t, vals[j], val)
-		}
-	}
-	require.NoError(t, db.SaveStateSummaries(ctx, ss))
-
-	// Verify slot indices exist before deletion
-	err = db.db.View(func(tx *bolt.Tx) error {
-		blockSlotBkt := tx.Bucket(blockSlotIndicesBucket)
-		stateSlotBkt := tx.Bucket(stateSlotIndicesBucket)
-
-		for i := uint64(0); i < slotsPerEpoch; i++ {
-			slot := bytesutil.SlotToBytesBigEndian(primitives.Slot(i + 1))
-			assert.NotNil(t, blockSlotBkt.Get(slot), "Expected block slot index to exist")
-			assert.NotNil(t, stateSlotBkt.Get(slot), "Expected state slot index to exist", i)
-		}
-		return nil
-	})
-	require.NoError(t, err)
-
-	// Delete data before slot at epoch 1
-	require.NoError(t, db.DeleteHistoricalDataBeforeSlot(ctx, primitives.Slot(slotsPerEpoch)))
-
-	// Verify blocks from epoch 0 are deleted
-	for i := uint64(0); i < slotsPerEpoch; i++ {
-		root, err := blks[i].Block().HashTreeRoot()
-		require.NoError(t, err)
-
-		// Check block is deleted
-		retrievedBlocks, err := db.BlocksBySlot(ctx, primitives.Slot(i))
-		require.NoError(t, err)
-		assert.Equal(t, 0, len(retrievedBlocks))
-
-		// Verify block does not exist
-		assert.Equal(t, false, db.HasBlock(ctx, root))
-
-		// Verify block parent root does not exist
-		err = db.db.View(func(tx *bolt.Tx) error {
-			require.Equal(t, 0, len(tx.Bucket(blockParentRootIndicesBucket).Get(root[:])))
-			return nil
-		})
-		require.NoError(t, err)
-
-		// Verify state is deleted
-		hasState := db.HasState(ctx, root)
-		assert.Equal(t, false, hasState)
-
-		// Verify state summary is deleted
-		hasSummary := db.HasStateSummary(ctx, root)
-		assert.Equal(t, false, hasSummary)
-
-		// Verify validator hashes for block roots are deleted
-		err = db.db.View(func(tx *bolt.Tx) error {
-			assert.Equal(t, 0, len(tx.Bucket(blockRootValidatorHashesBucket).Get(root[:])))
-			return nil
-		})
-		require.NoError(t, err)
-	}
-
-	// Verify slot indices are deleted
-	err = db.db.View(func(tx *bolt.Tx) error {
-		blockSlotBkt := tx.Bucket(blockSlotIndicesBucket)
-		stateSlotBkt := tx.Bucket(stateSlotIndicesBucket)
-
-		for i := uint64(0); i < slotsPerEpoch; i++ {
-			slot := bytesutil.SlotToBytesBigEndian(primitives.Slot(i + 1))
-			assert.Equal(t, 0, len(blockSlotBkt.Get(slot)), fmt.Sprintf("Expected block slot index to be deleted, slot: %d", slot))
-			assert.Equal(t, 0, len(stateSlotBkt.Get(slot)), fmt.Sprintf("Expected state slot index to be deleted, slot: %d", slot))
-		}
-		return nil
-	})
-	require.NoError(t, err)
-
-	// Verify blocks from epochs 1-3 still exist
-	for i := slotsPerEpoch; i < slotsPerEpoch*4; i++ {
-		root, err := blks[i].Block().HashTreeRoot()
-		require.NoError(t, err)
-
-		// Verify block exists
-		assert.Equal(t, true, db.HasBlock(ctx, root))
-
-		// Verify remaining block parent root exists, except last slot since we store parent roots of each block.
-		if i < slotsPerEpoch*4-1 {
+			// Verify slot indices exist before deletion
 			err = db.db.View(func(tx *bolt.Tx) error {
-				require.NotNil(t, tx.Bucket(blockParentRootIndicesBucket).Get(root[:]), fmt.Sprintf("Expected block parent index to be deleted, slot: %d", i))
+				blockSlotBkt := tx.Bucket(blockSlotIndicesBucket)
+				stateSlotBkt := tx.Bucket(stateSlotIndicesBucket)
+
+				for i := uint64(0); i < uint64(tt.deleteBeforeSlot); i++ {
+					slot := bytesutil.SlotToBytesBigEndian(primitives.Slot(i + 1))
+					assert.NotNil(t, blockSlotBkt.Get(slot), "Expected block slot index to exist")
+					assert.NotNil(t, stateSlotBkt.Get(slot), "Expected state slot index to exist", i)
+				}
 				return nil
 			})
 			require.NoError(t, err)
-		}

-		// Verify state exists
-		hasState := db.HasState(ctx, root)
-		assert.Equal(t, true, hasState)
+			// Delete data before slot
+			slotsDeleted, err := db.DeleteHistoricalDataBeforeSlot(ctx, primitives.Slot(tt.deleteBeforeSlot), tt.batchSize)
+			require.NoError(t, err)

-		// Verify state summary exists
-		hasSummary := db.HasStateSummary(ctx, root)
-		assert.Equal(t, true, hasSummary)
+			var startSlotDeleted, endSlotDeleted uint64
+			if tt.batchSize >= int(tt.deleteBeforeSlot) {
+				startSlotDeleted = 1
+				endSlotDeleted = tt.deleteBeforeSlot
+			} else {
+				startSlotDeleted = tt.deleteBeforeSlot - uint64(tt.batchSize) + 1
+				endSlotDeleted = tt.deleteBeforeSlot
+			}

-		// Verify slot indices still exist
-		err = db.db.View(func(tx *bolt.Tx) error {
-			blockSlotBkt := tx.Bucket(blockSlotIndicesBucket)
-			stateSlotBkt := tx.Bucket(stateSlotIndicesBucket)
+			require.Equal(t, endSlotDeleted-startSlotDeleted+1, uint64(slotsDeleted))

-			slot := bytesutil.SlotToBytesBigEndian(primitives.Slot(i + 1))
-			assert.NotNil(t, blockSlotBkt.Get(slot), "Expected block slot index to exist")
-			assert.NotNil(t, stateSlotBkt.Get(slot), "Expected state slot index to exist")
-			return nil
+			// Verify blocks before given slot/batch are deleted
+			for i := startSlotDeleted; i < endSlotDeleted; i++ {
+				root, err := blks[i].Block().HashTreeRoot()
+				require.NoError(t, err)
+
+				// Check block is deleted
+				retrievedBlocks, err := db.BlocksBySlot(ctx, primitives.Slot(i))
+				require.NoError(t, err)
+				assert.Equal(t, 0, len(retrievedBlocks), fmt.Sprintf("Expected %d blocks, got %d for slot %d", 0, len(retrievedBlocks), i))
+
+				// Verify block does not exist
+				assert.Equal(t, false, db.HasBlock(ctx, root), fmt.Sprintf("Expected block index to not exist for slot %d", i))
+
+				// Verify block parent root does not exist
+				err = db.db.View(func(tx *bolt.Tx) error {
+					require.Equal(t, 0, len(tx.Bucket(blockParentRootIndicesBucket).Get(root[:])))
+					return nil
+				})
+				require.NoError(t, err)
+
+				// Verify state is deleted
+				hasState := db.HasState(ctx, root)
+				assert.Equal(t, false, hasState)
+
+				// Verify state summary is deleted
+				hasSummary := db.HasStateSummary(ctx, root)
+				assert.Equal(t, false, hasSummary)
+
+				// Verify validator hashes for block roots are deleted
+				err = db.db.View(func(tx *bolt.Tx) error {
+					assert.Equal(t, 0, len(tx.Bucket(blockRootValidatorHashesBucket).Get(root[:])))
+					return nil
+				})
+				require.NoError(t, err)
+			}
+
+			// Verify slot indices are deleted
+			err = db.db.View(func(tx *bolt.Tx) error {
+				blockSlotBkt := tx.Bucket(blockSlotIndicesBucket)
+				stateSlotBkt := tx.Bucket(stateSlotIndicesBucket)
+
+				for i := startSlotDeleted; i < endSlotDeleted; i++ {
+					slot := bytesutil.SlotToBytesBigEndian(primitives.Slot(i + 1))
+					assert.Equal(t, 0, len(blockSlotBkt.Get(slot)), fmt.Sprintf("Expected block slot index to be deleted, slot: %d", slot))
+					assert.Equal(t, 0, len(stateSlotBkt.Get(slot)), fmt.Sprintf("Expected state slot index to be deleted, slot: %d", slot))
+				}
+				return nil
+			})
+			require.NoError(t, err)
+
+			// Verify blocks from expectedLastDeletedSlot till numEpochs still exist
+			for i := endSlotDeleted; i < slotsPerEpoch*tt.numOfEpochs; i++ {
+				root, err := blks[i].Block().HashTreeRoot()
+				require.NoError(t, err)
+
+				// Verify block exists
+				assert.Equal(t, true, db.HasBlock(ctx, root))
+
+				// Verify remaining block parent root exists, except last slot since we store parent roots of each block.
+				if i < slotsPerEpoch*tt.numOfEpochs-1 {
+					err = db.db.View(func(tx *bolt.Tx) error {
+						require.NotNil(t, tx.Bucket(blockParentRootIndicesBucket).Get(root[:]), fmt.Sprintf("Expected block parent index to be deleted, slot: %d", i))
+						return nil
+					})
+					require.NoError(t, err)
+				}
+
+				// Verify state exists
+				hasState := db.HasState(ctx, root)
+				assert.Equal(t, true, hasState)
+
+				// Verify state summary exists
+				hasSummary := db.HasStateSummary(ctx, root)
+				assert.Equal(t, true, hasSummary)
+
+				// Verify slot indices still exist
+				err = db.db.View(func(tx *bolt.Tx) error {
+					blockSlotBkt := tx.Bucket(blockSlotIndicesBucket)
+					stateSlotBkt := tx.Bucket(stateSlotIndicesBucket)
+
+					slot := bytesutil.SlotToBytesBigEndian(primitives.Slot(i + 1))
+					assert.NotNil(t, blockSlotBkt.Get(slot), "Expected block slot index to exist")
+					assert.NotNil(t, stateSlotBkt.Get(slot), "Expected state slot index to exist")
+					return nil
+				})
+				require.NoError(t, err)
+
+				// Verify validator entries still exist
+				valsActual, err := db.validatorEntries(ctx, root)
+				require.NoError(t, err)
+				assert.NotNil(t, valsActual)
+
+				// Verify remaining validator hashes for block roots exists
+				err = db.db.View(func(tx *bolt.Tx) error {
+					assert.NotNil(t, tx.Bucket(blockRootValidatorHashesBucket).Get(root[:]))
+					return nil
+				})
+				require.NoError(t, err)
+			}
 		})
-		require.NoError(t, err)
-
-		// Verify validator entries still exist
-		valsActual, err := db.validatorEntries(ctx, root)
-		require.NoError(t, err)
-		assert.NotNil(t, valsActual)
-
-		// Verify remaining validator hashes for block roots exists
-		err = db.db.View(func(tx *bolt.Tx) error {
-			assert.NotNil(t, tx.Bucket(blockRootValidatorHashesBucket).Get(root[:]))
-			return nil
-		})
-		require.NoError(t, err)
 	}
+
 }

 func TestStore_GenesisBlock(t *testing.T) {
--- a/beacon-chain/db/kv/deposit_contract.go
+++ b/beacon-chain/db/kv/deposit_contract.go
@@ -20,7 +20,7 @@ func (s *Store) DepositContractAddress(ctx context.Context) ([]byte, error) {
 		addr = chainInfo.Get(depositContractAddressKey)
 		return nil
 	}); err != nil { // This view never returns an error, but we'll handle anyway for sanity.
-		panic(err)
+		panic(err) // lint:nopanic -- View never returns an error.
 	}
 	return addr, nil
 }
--- a/beacon-chain/db/kv/state.go
+++ b/beacon-chain/db/kv/state.go
@@ -407,7 +407,7 @@ func (s *Store) HasState(ctx context.Context, blockRoot [32]byte) bool {
 		return nil
 	})
 	if err != nil {
-		panic(err)
+		panic(err) // lint:nopanic -- View never returns an error.
 	}
 	return hasState
 }
@@ -820,30 +820,25 @@ func (s *Store) slotByBlockRoot(ctx context.Context, tx *bolt.Tx, blockRoot []by
 			// no need to construct the validator entries as it is not used here.
 			s, err := s.unmarshalState(ctx, enc, nil)
 			if err != nil {
-				return 0, err
+				return 0, errors.Wrap(err, "could not unmarshal state")
 			}
 			if s == nil || s.IsNil() {
 				return 0, errors.New("state can't be nil")
 			}
 			return s.Slot(), nil
 		}
-		b := &ethpb.SignedBeaconBlock{}
-		err := decode(ctx, enc, b)
+		b, err := unmarshalBlock(ctx, enc)
 		if err != nil {
+			return 0, errors.Wrap(err, "could not unmarshal block")
+		}
+		if err := blocks.BeaconBlockIsNil(b); err != nil {
 			return 0, err
 		}
-		wsb, err := blocks.NewSignedBeaconBlock(b)
-		if err != nil {
-			return 0, err
-		}
-		if err := blocks.BeaconBlockIsNil(wsb); err != nil {
-			return 0, err
-		}
-		return b.Block.Slot, nil
+		return b.Block().Slot(), nil
 	}
 	stateSummary := &ethpb.StateSummary{}
 	if err := decode(ctx, enc, stateSummary); err != nil {
-		return 0, err
+		return 0, errors.Wrap(err, "could not unmarshal state summary")
 	}
 	return stateSummary.Slot, nil
 }
--- a/beacon-chain/db/kv/state_test.go
+++ b/beacon-chain/db/kv/state_test.go
@@ -5,7 +5,6 @@ import (
 	"crypto/rand"
 	"encoding/binary"
 	mathRand "math/rand"
-
 	"strconv"
 	"testing"
 	"time"
@@ -1070,6 +1069,31 @@ func TestBellatrixState_CanDelete(t *testing.T) {
 	require.Equal(t, state.ReadOnlyBeaconState(nil), savedS, "Unsaved state should've been nil")
 }

+func TestBellatrixState_CanDeleteWithBlock(t *testing.T) {
+	db := setupDB(t)
+
+	b := util.NewBeaconBlockBellatrix()
+	b.Block.Slot = 100
+	r, err := b.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wsb, err := blocks.NewSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, db.SaveBlock(context.Background(), wsb))
+
+	require.Equal(t, false, db.HasState(context.Background(), r))
+
+	st, _ := util.DeterministicGenesisStateBellatrix(t, 1)
+	require.NoError(t, st.SetSlot(100))
+
+	require.NoError(t, db.SaveState(context.Background(), st, r))
+	require.Equal(t, true, db.HasState(context.Background(), r))
+
+	require.NoError(t, db.DeleteState(context.Background(), r))
+	savedS, err := db.State(context.Background(), r)
+	require.NoError(t, err)
+	require.Equal(t, state.ReadOnlyBeaconState(nil), savedS, "Unsaved state should've been nil")
+}
+
 func TestDenebState_CanSaveRetrieve(t *testing.T) {
 	db := setupDB(t)

--- a/beacon-chain/db/kv/utils.go
+++ b/beacon-chain/db/kv/utils.go
@@ -114,3 +114,27 @@ func splitRoots(b []byte) ([][32]byte, error) {
 	}
 	return rl, nil
 }
+
+func removeRoot(roots []byte, root [32]byte) ([]byte, error) {
+	if len(roots) == 0 {
+		return []byte{}, nil
+	}
+	if len(roots) == 32 && bytes.Equal(roots, root[:]) {
+		return []byte{}, nil
+	}
+	if len(roots)%32 != 0 {
+		return nil, errors.Wrapf(errMisalignedRootList, "root list len=%d", len(roots))
+	}
+
+	search := root[:]
+	for i := 0; i <= len(roots)-32; i += 32 {
+		if bytes.Equal(roots[i:i+32], search) {
+			result := make([]byte, len(roots)-32)
+			copy(result, roots[:i])
+			copy(result[i:], roots[i+32:])
+			return result, nil
+		}
+	}
+
+	return roots, nil
+}
--- a/beacon-chain/db/kv/utils_test.go
+++ b/beacon-chain/db/kv/utils_test.go
@@ -1,6 +1,7 @@
 package kv

 import (
+	"bytes"
 	"context"
 	"crypto/rand"
 	"testing"
@@ -195,3 +196,85 @@ func TestSplitRoots(t *testing.T) {
 		})
 	}
 }
+
+func tPad(p ...[]byte) []byte {
+	r := make([]byte, 32*len(p))
+	for i, b := range p {
+		copy(r[i*32:], b)
+	}
+	return r
+}
+
+func TestRemoveRoot(t *testing.T) {
+	cases := []struct {
+		name   string
+		roots  []byte
+		root   [32]byte
+		expect []byte
+		err    error
+	}{
+		{
+			name:   "empty",
+			roots:  []byte{},
+			root:   [32]byte{0xde, 0xad, 0xbe, 0xef},
+			expect: []byte{},
+		},
+		{
+			name:   "single",
+			roots:  tPad([]byte{0xde, 0xad, 0xbe, 0xef}),
+			root:   [32]byte{0xde, 0xad, 0xbe, 0xef},
+			expect: []byte{},
+		},
+		{
+			name:   "single, different",
+			roots:  tPad([]byte{0xde, 0xad, 0xbe, 0xef}),
+			root:   [32]byte{0xde, 0xad, 0xbe, 0xee},
+			expect: tPad([]byte{0xde, 0xad, 0xbe, 0xef}),
+		},
+		{
+			name:   "multi",
+			roots:  tPad([]byte{0xde, 0xad, 0xbe, 0xef}, []byte{0xac, 0x1d, 0xfa, 0xce}),
+			root:   [32]byte{0xac, 0x1d, 0xfa, 0xce},
+			expect: tPad([]byte{0xde, 0xad, 0xbe, 0xef}),
+		},
+		{
+			name:   "multi, reordered",
+			roots:  tPad([]byte{0xac, 0x1d, 0xfa, 0xce}, []byte{0xde, 0xad, 0xbe, 0xef}),
+			root:   [32]byte{0xac, 0x1d, 0xfa, 0xce},
+			expect: tPad([]byte{0xde, 0xad, 0xbe, 0xef}),
+		},
+		{
+			name:   "multi, 3",
+			roots:  tPad([]byte{0xac, 0x1d, 0xfa, 0xce}, []byte{0xbe, 0xef, 0xca, 0xb5}, []byte{0xde, 0xad, 0xbe, 0xef}),
+			root:   [32]byte{0xac, 0x1d, 0xfa, 0xce},
+			expect: tPad([]byte{0xbe, 0xef, 0xca, 0xb5}, []byte{0xde, 0xad, 0xbe, 0xef}),
+		},
+		{
+			name:   "multi, different",
+			roots:  tPad([]byte{0xde, 0xad, 0xbe, 0xef}, []byte{0xac, 0x1d, 0xfa, 0xce}),
+			root:   [32]byte{0xac, 0x1d, 0xbe, 0xa7},
+			expect: tPad([]byte{0xde, 0xad, 0xbe, 0xef}, []byte{0xac, 0x1d, 0xfa, 0xce}),
+		},
+		{
+			name:  "misaligned",
+			roots: make([]byte, 61),
+			root:  [32]byte{0xac, 0x1d, 0xbe, 0xa7},
+			err:   errMisalignedRootList,
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			before := make([]byte, len(c.roots))
+			copy(before, c.roots)
+			r, err := removeRoot(c.roots, c.root)
+			if c.err != nil {
+				require.ErrorIs(t, err, c.err)
+				return
+			}
+			require.NoError(t, err)
+			require.Equal(t, len(c.expect), len(r))
+			require.Equal(t, true, bytes.Equal(c.expect, r))
+			require.Equal(t, true, bytes.Equal(before, c.roots))
+		})
+	}
+}
--- a/beacon-chain/db/kv/validated_checkpoint.go
+++ b/beacon-chain/db/kv/validated_checkpoint.go
@@ -1,8 +1,10 @@
 package kv

 import (
+	"bytes"
 	"context"

+	"github.com/prysmaticlabs/prysm/v5/config/params"
 	"github.com/prysmaticlabs/prysm/v5/monitoring/tracing/trace"
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
 	bolt "go.etcd.io/bbolt"
@@ -19,7 +21,17 @@ func (s *Store) LastValidatedCheckpoint(ctx context.Context) (*ethpb.Checkpoint,
 		if enc == nil {
 			var finErr error
 			checkpoint, finErr = s.FinalizedCheckpoint(ctx)
-			return finErr
+			if finErr != nil {
+				return finErr
+			}
+			if bytes.Equal(checkpoint.Root, params.BeaconConfig().ZeroHash[:]) {
+				bkt = tx.Bucket(blocksBucket)
+				r := bkt.Get(genesisBlockRootKey)
+				if r != nil {
+					checkpoint.Root = r
+				}
+			}
+			return nil
 		}
 		checkpoint = &ethpb.Checkpoint{}
 		return decode(ctx, enc, checkpoint)
--- a/beacon-chain/db/pruner/pruner.go
+++ b/beacon-chain/db/pruner/pruner.go
@@ -16,6 +16,15 @@ import (

 var log = logrus.WithField("prefix", "db-pruner")

+const (
+	// defaultPrunableBatchSize is the number of slots that can be pruned at once.
+	defaultPrunableBatchSize = 32
+	// defaultPruningWindow is the duration of one pruning window.
+	defaultPruningWindow = time.Second * 3
+	// defaultNumBatchesToPrune is the number of batches to prune in one pruning window.
+	defaultNumBatchesToPrune = 15
+)
+
 type ServiceOption func(*Service)

 // WithRetentionPeriod allows the user to specify a different data retention period than the spec default.
@@ -143,14 +152,17 @@ func (p *Service) prune(slot primitives.Slot) error {
 	}).Debug("Pruning chain data")

 	tt := time.Now()
-	if err := p.db.DeleteHistoricalDataBeforeSlot(p.ctx, pruneUpto); err != nil {
-		return errors.Wrapf(err, "could not delete upto slot %d", pruneUpto)
+	numBatches, err := p.pruneBatches(pruneUpto)
+	if err != nil {
+		return errors.Wrap(err, "failed to prune batches")
 	}

 	log.WithFields(logrus.Fields{
 		"prunedUpto":  pruneUpto,
 		"duration":    time.Since(tt),
 		"currentSlot": slot,
+		"batchSize":   defaultPrunableBatchSize,
+		"numBatches":  numBatches,
 	}).Debug("Successfully pruned chain data")

 	// Update pruning checkpoint.
@@ -159,6 +171,33 @@ func (p *Service) prune(slot primitives.Slot) error {
 	return nil
 }

+func (p *Service) pruneBatches(pruneUpto primitives.Slot) (int, error) {
+	ctx, cancel := context.WithTimeout(p.ctx, defaultPruningWindow)
+	defer cancel()
+
+	numBatches := 0
+	for {
+		select {
+		case <-ctx.Done():
+			return numBatches, nil
+		default:
+			for i := 0; i < defaultNumBatchesToPrune; i++ {
+				slotsDeleted, err := p.db.DeleteHistoricalDataBeforeSlot(ctx, pruneUpto, defaultPrunableBatchSize)
+				if err != nil {
+					return 0, errors.Wrapf(err, "could not delete upto slot %d", pruneUpto)
+				}
+
+				// Return if there's nothing to delete.
+				if slotsDeleted == 0 {
+					return numBatches, nil
+				}
+
+				numBatches++
+			}
+		}
+	}
+}
+
 // pruneStartSlotFunc returns the function to determine the start slot to start pruning.
 func pruneStartSlotFunc(retentionEpochs primitives.Epoch) func(primitives.Slot) primitives.Slot {
 	return func(current primitives.Slot) primitives.Slot {
--- a/beacon-chain/execution/block_cache.go
+++ b/beacon-chain/execution/block_cache.go
@@ -158,7 +158,7 @@ func trim(queue *cache.FIFO, maxSize uint64) {
 	for s := uint64(len(queue.ListKeys())); s > maxSize; s-- {
 		// #nosec G104 popProcessNoopFunc never returns an error
 		if _, err := queue.Pop(popProcessNoopFunc); err != nil { // This never returns an error, but we'll handle anyway for sanity.
-			panic(err)
+			panic(err) // lint:nopanic -- popProcessNoopFunc never returns an error.
 		}
 	}
 }
--- a/beacon-chain/execution/testing/mock_faulty_powchain.go
+++ b/beacon-chain/execution/testing/mock_faulty_powchain.go
@@ -57,7 +57,7 @@ func (*FaultyExecutionChain) ChainStartEth1Data() *ethpb.Eth1Data {
 func (*FaultyExecutionChain) PreGenesisState() state.BeaconState {
 	s, err := state_native.InitializeFromProtoUnsafePhase0(&ethpb.BeaconState{})
 	if err != nil {
-		panic("could not initialize state")
+		panic("could not initialize state") // lint:nopanic -- test code.
 	}
 	return s
 }
--- a/beacon-chain/forkchoice/doubly-linked-tree/node.go
+++ b/beacon-chain/forkchoice/doubly-linked-tree/node.go
@@ -156,6 +156,10 @@ func (n *Node) nodeTreeDump(ctx context.Context, nodes []*forkchoice2.Node) ([]*
 	if n.parent != nil {
 		parentRoot = n.parent.root
 	}
+	target := [32]byte{}
+	if n.target != nil {
+		target = n.target.root
+	}
 	thisNode := &forkchoice2.Node{
 		Slot:                     n.slot,
 		BlockRoot:                n.root[:],
@@ -169,6 +173,7 @@ func (n *Node) nodeTreeDump(ctx context.Context, nodes []*forkchoice2.Node) ([]*
 		ExecutionOptimistic:      n.optimistic,
 		ExecutionBlockHash:       n.payloadHash[:],
 		Timestamp:                n.timestamp,
+		Target:                   target[:],
 	}
 	if n.optimistic {
 		thisNode.Validity = forkchoice2.Optimistic
--- a/beacon-chain/forkchoice/doubly-linked-tree/store.go
+++ b/beacon-chain/forkchoice/doubly-linked-tree/store.go
@@ -252,6 +252,13 @@ func (s *Store) tips() ([][32]byte, []primitives.Slot) {
 	return roots, slots
 }

+func (f *ForkChoice) HighestReceivedBlockRoot() [32]byte {
+	if f.store.highestReceivedNode == nil {
+		return [32]byte{}
+	}
+	return f.store.highestReceivedNode.root
+}
+
 // HighestReceivedBlockSlot returns the highest slot received by the forkchoice
 func (f *ForkChoice) HighestReceivedBlockSlot() primitives.Slot {
 	if f.store.highestReceivedNode == nil {
--- a/beacon-chain/forkchoice/interfaces.go
+++ b/beacon-chain/forkchoice/interfaces.go
@@ -65,6 +65,7 @@ type FastGetter interface {
 	FinalizedPayloadBlockHash() [32]byte
 	HasNode([32]byte) bool
 	HighestReceivedBlockSlot() primitives.Slot
+	HighestReceivedBlockRoot() [32]byte
 	HighestReceivedBlockDelay() primitives.Slot
 	IsCanonical(root [32]byte) bool
 	IsOptimistic(root [32]byte) (bool, error)
--- a/beacon-chain/forkchoice/ro.go
+++ b/beacon-chain/forkchoice/ro.go
@@ -114,6 +114,13 @@ func (ro *ROForkChoice) HighestReceivedBlockSlot() primitives.Slot {
 	return ro.getter.HighestReceivedBlockSlot()
 }

+// HighestReceivedBlockRoot delegates to the underlying forkchoice call, under a lock.
+func (ro *ROForkChoice) HighestReceivedBlockRoot() [32]byte {
+	ro.l.RLock()
+	defer ro.l.RUnlock()
+	return ro.getter.HighestReceivedBlockRoot()
+}
+
 // HighestReceivedBlockDelay delegates to the underlying forkchoice call, under a lock.
 func (ro *ROForkChoice) HighestReceivedBlockDelay() primitives.Slot {
 	ro.l.RLock()
--- a/beacon-chain/forkchoice/ro_test.go
+++ b/beacon-chain/forkchoice/ro_test.go
@@ -29,6 +29,7 @@ const (
 	unrealizedJustifiedPayloadBlockHashCalled
 	nodeCountCalled
 	highestReceivedBlockSlotCalled
+	highestReceivedBlockRootCalled
 	highestReceivedBlockDelayCalled
 	receivedBlocksLastEpochCalled
 	weightCalled
@@ -252,6 +253,11 @@ func (ro *mockROForkchoice) HighestReceivedBlockSlot() primitives.Slot {
 	return 0
 }

+func (ro *mockROForkchoice) HighestReceivedBlockRoot() [32]byte {
+	ro.calls = append(ro.calls, highestReceivedBlockRootCalled)
+	return [32]byte{}
+}
+
 func (ro *mockROForkchoice) HighestReceivedBlockDelay() primitives.Slot {
 	ro.calls = append(ro.calls, highestReceivedBlockDelayCalled)
 	return 0
--- a/beacon-chain/node/node.go
+++ b/beacon-chain/node/node.go
@@ -122,6 +122,7 @@ type BeaconNode struct {
 	BlobStorageOptions      []filesystem.BlobStorageOption
 	verifyInitWaiter        *verification.InitializerWaiter
 	syncChecker             *initialsync.SyncChecker
+	slasherEnabled          bool
 }

 // New creates a new node instance, sets up configuration options, and registers
@@ -159,6 +160,7 @@ func New(cliCtx *cli.Context, cancel context.CancelFunc, opts ...Option) (*Beaco
 		serviceFlagOpts:         &serviceFlagOpts{},
 		initialSyncComplete:     make(chan struct{}),
 		syncChecker:             &initialsync.SyncChecker{},
+		slasherEnabled:          cliCtx.Bool(flags.SlasherFlag.Name),
 	}

 	for _, opt := range opts {
@@ -342,7 +344,7 @@ func registerServices(cliCtx *cli.Context, beacon *BeaconNode, synchronizer *sta
 		return errors.Wrap(err, "could not register slashing pool service")
 	}

-	log.Debugln("Registering Slasher Service")
+	log.WithField("enabled", beacon.slasherEnabled).Debugln("Registering Slasher Service")
 	if err := beacon.registerSlasherService(); err != nil {
 		return errors.Wrap(err, "could not register slasher service")
 	}
@@ -438,7 +440,7 @@ func (b *BeaconNode) Start() {
 				log.WithField("times", i-1).Info("Already shutting down, interrupt more to panic")
 			}
 		}
-		panic("Panic closing the beacon node")
+		panic("Panic closing the beacon node") // lint:nopanic -- Panic is requested by user.
 	}()

 	// Wait for stop channel to be closed.
@@ -587,7 +589,7 @@ func (b *BeaconNode) startDB(cliCtx *cli.Context, depositAddress string) error {
 }

 func (b *BeaconNode) startSlasherDB(cliCtx *cli.Context) error {
-	if !features.Get().EnableSlasher {
+	if !b.slasherEnabled {
 		return nil
 	}
 	baseDir := cliCtx.String(cmd.DataDirFlag.Name)
@@ -704,7 +706,7 @@ func (b *BeaconNode) registerP2P(cliCtx *cli.Context) error {
 func (b *BeaconNode) fetchP2P() p2p.P2P {
 	var p *p2p.Service
 	if err := b.services.FetchService(&p); err != nil {
-		panic(err)
+		panic(err) // lint:nopanic -- This could panic application start if the services are misconfigured.
 	}
 	return p
 }
@@ -712,7 +714,7 @@ func (b *BeaconNode) fetchP2P() p2p.P2P {
 func (b *BeaconNode) fetchBuilderService() *builder.Service {
 	var s *builder.Service
 	if err := b.services.FetchService(&s); err != nil {
-		panic(err)
+		panic(err) // lint:nopanic -- This could panic application start if the services are misconfigured.
 	}
 	return s
 }
@@ -775,6 +777,7 @@ func (b *BeaconNode) registerBlockchainService(fc forkchoice.ForkChoicer, gs *st
 		blockchain.WithTrackedValidatorsCache(b.trackedValidatorsCache),
 		blockchain.WithPayloadIDCache(b.payloadIDCache),
 		blockchain.WithSyncChecker(b.syncChecker),
+		blockchain.WithSlasherEnabled(b.slasherEnabled),
 	)

 	blockchainService, err := blockchain.NewService(b.ctx, opts...)
@@ -859,6 +862,7 @@ func (b *BeaconNode) registerSyncService(initialSyncComplete chan struct{}, bFil
 		regularsync.WithBlobStorage(b.BlobStorage),
 		regularsync.WithVerifierWaiter(b.verifyInitWaiter),
 		regularsync.WithAvailableBlocker(bFillStore),
+		regularsync.WithSlasherEnabled(b.slasherEnabled),
 	)
 	return b.services.RegisterService(rs)
 }
@@ -887,7 +891,7 @@ func (b *BeaconNode) registerInitialSyncService(complete chan struct{}) error {
 }

 func (b *BeaconNode) registerSlasherService() error {
-	if !features.Get().EnableSlasher {
+	if !b.slasherEnabled {
 		return nil
 	}
 	var chainService *blockchain.Service
@@ -934,7 +938,7 @@ func (b *BeaconNode) registerRPCService(router *http.ServeMux) error {
 	}

 	var slasherService *slasher.Service
-	if features.Get().EnableSlasher {
+	if b.slasherEnabled {
 		if err := b.services.FetchService(&slasherService); err != nil {
 			return err
 		}
@@ -1014,13 +1018,13 @@ func (b *BeaconNode) registerPrometheusService(_ *cli.Context) error {
 	var additionalHandlers []prometheus.Handler
 	var p *p2p.Service
 	if err := b.services.FetchService(&p); err != nil {
-		panic(err)
+		panic(err) // lint:nopanic -- This could panic application start if the services are misconfigured.
 	}
 	additionalHandlers = append(additionalHandlers, prometheus.Handler{Path: "/p2p", Handler: p.InfoHandler})

 	var c *blockchain.Service
 	if err := b.services.FetchService(&c); err != nil {
-		panic(err)
+		panic(err) // lint:nopanic -- This could panic application start if the services are misconfigured.
 	}

 	service := prometheus.NewService(
--- a/beacon-chain/operations/attestations/kv/aggregated.go
+++ b/beacon-chain/operations/attestations/kv/aggregated.go
@@ -23,10 +23,7 @@ import (
 func (c *AttCaches) AggregateUnaggregatedAttestations(ctx context.Context) error {
 	ctx, span := trace.StartSpan(ctx, "operations.attestations.kv.AggregateUnaggregatedAttestations")
 	defer span.End()
-	unaggregatedAtts, err := c.UnaggregatedAttestations()
-	if err != nil {
-		return err
-	}
+	unaggregatedAtts := c.UnaggregatedAttestations()
 	return c.aggregateUnaggregatedAtts(ctx, unaggregatedAtts)
 }

--- a/beacon-chain/operations/attestations/kv/unaggregated.go
+++ b/beacon-chain/operations/attestations/kv/unaggregated.go
@@ -9,6 +9,7 @@ import (
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1/attestation"
 	"github.com/prysmaticlabs/prysm/v5/runtime/version"
+	log "github.com/sirupsen/logrus"
 )

 // SaveUnaggregatedAttestation saves an unaggregated attestation in cache.
@@ -52,7 +53,7 @@ func (c *AttCaches) SaveUnaggregatedAttestations(atts []ethpb.Att) error {
 }

 // UnaggregatedAttestations returns all the unaggregated attestations in cache.
-func (c *AttCaches) UnaggregatedAttestations() ([]ethpb.Att, error) {
+func (c *AttCaches) UnaggregatedAttestations() []ethpb.Att {
 	c.unAggregateAttLock.RLock()
 	defer c.unAggregateAttLock.RUnlock()
 	unAggregatedAtts := c.unAggregatedAtt
@@ -60,13 +61,14 @@ func (c *AttCaches) UnaggregatedAttestations() ([]ethpb.Att, error) {
 	for _, att := range unAggregatedAtts {
 		seen, err := c.hasSeenBit(att)
 		if err != nil {
-			return nil, err
+			log.WithError(err).Debug("Could not check if unaggregated attestation's bit has been seen. Attestation will not be returned")
+			continue
 		}
 		if !seen {
 			atts = append(atts, att.Clone())
 		}
 	}
-	return atts, nil
+	return atts
 }

 // UnaggregatedAttestationsBySlotIndex returns the unaggregated attestations in cache,
@@ -137,7 +139,7 @@ func (c *AttCaches) DeleteUnaggregatedAttestation(att ethpb.Att) error {
 	}

 	if err := c.insertSeenBit(att); err != nil {
-		return err
+		log.WithError(err).Debug("Could not insert seen bit of unaggregated attestation. Attestation will be deleted")
 	}

 	id, err := attestation.NewId(att, attestation.Full)
@@ -163,7 +165,12 @@ func (c *AttCaches) DeleteSeenUnaggregatedAttestations() (int, error) {
 		if att == nil || att.IsNil() || att.IsAggregated() {
 			continue
 		}
-		if seen, err := c.hasSeenBit(att); err == nil && seen {
+		seen, err := c.hasSeenBit(att)
+		if err != nil {
+			log.WithError(err).Debug("Could not check if unaggregated attestation's bit has been seen. Attestation will be deleted")
+			seen = true
+		}
+		if seen {
 			delete(c.unAggregatedAtt, r)
 			count++
 		}
--- a/beacon-chain/operations/attestations/kv/unaggregated_test.go
+++ b/beacon-chain/operations/attestations/kv/unaggregated_test.go
@@ -17,6 +17,23 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/testing/util"
 )

+func TestKV_Unaggregated_UnaggregatedAttestations(t *testing.T) {
+	t.Run("not returned when hasSeenBit fails", func(t *testing.T) {
+		att := util.HydrateAttestation(&ethpb.Attestation{Data: &ethpb.AttestationData{Slot: 1}, AggregationBits: bitfield.Bitlist{0b101}})
+		id, err := attestation.NewId(att, attestation.Data)
+		require.NoError(t, err)
+
+		cache := NewAttCaches()
+		require.NoError(t, cache.SaveUnaggregatedAttestation(att))
+		cache.seenAtt.Delete(id.String())
+		// cache a bitlist whose length is different from the attestation bitlist's length
+		cache.seenAtt.Set(id.String(), []bitfield.Bitlist{{0b1001}}, c.DefaultExpiration)
+
+		atts := cache.UnaggregatedAttestations()
+		assert.Equal(t, 0, len(atts))
+	})
+}
+
 func TestKV_Unaggregated_SaveUnaggregatedAttestation(t *testing.T) {
 	tests := []struct {
 		name          string
@@ -151,10 +168,24 @@ func TestKV_Unaggregated_DeleteUnaggregatedAttestation(t *testing.T) {
 		for _, att := range atts {
 			assert.NoError(t, cache.DeleteUnaggregatedAttestation(att))
 		}
-		returned, err := cache.UnaggregatedAttestations()
-		require.NoError(t, err)
+		returned := cache.UnaggregatedAttestations()
 		assert.DeepEqual(t, []ethpb.Att{}, returned)
 	})
+
+	t.Run("deleted when insertSeenBit fails", func(t *testing.T) {
+		att := util.HydrateAttestation(&ethpb.Attestation{Data: &ethpb.AttestationData{Slot: 1}, AggregationBits: bitfield.Bitlist{0b101}})
+		id, err := attestation.NewId(att, attestation.Data)
+		require.NoError(t, err)
+
+		cache := NewAttCaches()
+		require.NoError(t, cache.SaveUnaggregatedAttestation(att))
+		cache.seenAtt.Delete(id.String())
+		// cache a bitlist whose length is different from the attestation bitlist's length
+		cache.seenAtt.Set(id.String(), []bitfield.Bitlist{{0b1001}}, c.DefaultExpiration)
+
+		require.NoError(t, cache.DeleteUnaggregatedAttestation(att))
+		assert.Equal(t, 0, len(cache.unAggregatedAtt), "Attestation was not deleted")
+	})
 }

 func TestKV_Unaggregated_DeleteSeenUnaggregatedAttestations(t *testing.T) {
@@ -201,11 +232,10 @@ func TestKV_Unaggregated_DeleteSeenUnaggregatedAttestations(t *testing.T) {
 		assert.NoError(t, err)
 		assert.Equal(t, 1, count)
 		assert.Equal(t, 2, cache.UnaggregatedAttestationCount())
-		returned, err := cache.UnaggregatedAttestations()
+		returned := cache.UnaggregatedAttestations()
 		sort.Slice(returned, func(i, j int) bool {
 			return bytes.Compare(returned[i].GetAggregationBits(), returned[j].GetAggregationBits()) < 0
 		})
-		require.NoError(t, err)
 		assert.DeepEqual(t, []ethpb.Att{atts[0], atts[2]}, returned)
 	})

@@ -228,10 +258,26 @@ func TestKV_Unaggregated_DeleteSeenUnaggregatedAttestations(t *testing.T) {
 		assert.NoError(t, err)
 		assert.Equal(t, 3, count)
 		assert.Equal(t, 0, cache.UnaggregatedAttestationCount())
-		returned, err := cache.UnaggregatedAttestations()
-		require.NoError(t, err)
+		returned := cache.UnaggregatedAttestations()
 		assert.DeepEqual(t, []ethpb.Att{}, returned)
 	})
+
+	t.Run("deleted when hasSeenBit fails", func(t *testing.T) {
+		att := util.HydrateAttestation(&ethpb.Attestation{Data: &ethpb.AttestationData{Slot: 1}, AggregationBits: bitfield.Bitlist{0b101}})
+		id, err := attestation.NewId(att, attestation.Data)
+		require.NoError(t, err)
+
+		cache := NewAttCaches()
+		require.NoError(t, cache.SaveUnaggregatedAttestation(att))
+		cache.seenAtt.Delete(id.String())
+		// cache a bitlist whose length is different from the attestation bitlist's length
+		cache.seenAtt.Set(id.String(), []bitfield.Bitlist{{0b1001}}, c.DefaultExpiration)
+
+		count, err := cache.DeleteSeenUnaggregatedAttestations()
+		require.NoError(t, err)
+		assert.Equal(t, 1, count)
+		assert.Equal(t, 0, len(cache.unAggregatedAtt), "Attestation was not deleted")
+	})
 }

 func TestKV_Unaggregated_UnaggregatedAttestationsBySlotIndex(t *testing.T) {
--- a/beacon-chain/operations/attestations/mock/mock.go
+++ b/beacon-chain/operations/attestations/mock/mock.go
@@ -1,3 +1,4 @@
+// lint:nopanic -- Mock / test code, panic is allowed.
 package mock

 import (
@@ -79,8 +80,8 @@ func (m *PoolMock) SaveUnaggregatedAttestations(atts []ethpb.Att) error {
 }

 // UnaggregatedAttestations --
-func (m *PoolMock) UnaggregatedAttestations() ([]ethpb.Att, error) {
-	return m.UnaggregatedAtts, nil
+func (m *PoolMock) UnaggregatedAttestations() []ethpb.Att {
+	return m.UnaggregatedAtts
 }

 // UnaggregatedAttestationsBySlotIndex --
--- a/beacon-chain/operations/attestations/pool.go
+++ b/beacon-chain/operations/attestations/pool.go
@@ -26,7 +26,7 @@ type Pool interface {
 	// For unaggregated attestations.
 	SaveUnaggregatedAttestation(att ethpb.Att) error
 	SaveUnaggregatedAttestations(atts []ethpb.Att) error
-	UnaggregatedAttestations() ([]ethpb.Att, error)
+	UnaggregatedAttestations() []ethpb.Att
 	UnaggregatedAttestationsBySlotIndex(ctx context.Context, slot primitives.Slot, committeeIndex primitives.CommitteeIndex) []*ethpb.Attestation
 	UnaggregatedAttestationsBySlotIndexElectra(ctx context.Context, slot primitives.Slot, committeeIndex primitives.CommitteeIndex) []*ethpb.AttestationElectra
 	DeleteUnaggregatedAttestation(att ethpb.Att) error
--- a/beacon-chain/operations/attestations/prune_expired.go
+++ b/beacon-chain/operations/attestations/prune_expired.go
@@ -61,12 +61,8 @@ func (s *Service) pruneExpiredAtts() {
 	if _, err := s.cfg.Pool.DeleteSeenUnaggregatedAttestations(); err != nil {
 		log.WithError(err).Error("Cannot delete seen attestations")
 	}
-	unAggregatedAtts, err := s.cfg.Pool.UnaggregatedAttestations()
-	if err != nil {
-		log.WithError(err).Error("Could not get unaggregated attestations")
-		return
-	}
-	for _, att := range unAggregatedAtts {
+
+	for _, att := range s.cfg.Pool.UnaggregatedAttestations() {
 		if s.expired(att.GetData().Slot) {
 			if err := s.cfg.Pool.DeleteUnaggregatedAttestation(att); err != nil {
 				log.WithError(err).Error("Could not delete expired unaggregated attestation")
--- a/beacon-chain/operations/attestations/prune_expired_test.go
+++ b/beacon-chain/operations/attestations/prune_expired_test.go
@@ -54,9 +54,7 @@ func TestPruneExpired_Ticker(t *testing.T) {

 	done := make(chan struct{}, 1)
 	async.RunEvery(ctx, 500*time.Millisecond, func() {
-		atts, err := s.cfg.Pool.UnaggregatedAttestations()
-		require.NoError(t, err)
-		for _, attestation := range atts {
+		for _, attestation := range s.cfg.Pool.UnaggregatedAttestations() {
 			if attestation.GetData().Slot == 0 {
 				return
 			}
--- a/beacon-chain/operations/blstoexec/mock/mock.go
+++ b/beacon-chain/operations/blstoexec/mock/mock.go
@@ -28,10 +28,10 @@ func (m *PoolMock) InsertBLSToExecChange(change *eth.SignedBLSToExecutionChange)

 // MarkIncluded --
 func (*PoolMock) MarkIncluded(_ *eth.SignedBLSToExecutionChange) {
-	panic("implement me")
+	panic("implement me") // lint:nopanic -- mock / test code.
 }

 // ValidatorExists --
 func (*PoolMock) ValidatorExists(_ primitives.ValidatorIndex) bool {
-	panic("implement me")
+	panic("implement me") // lint:nopanic -- mock / test code.
 }
--- a/beacon-chain/operations/slashings/mock/mock.go
+++ b/beacon-chain/operations/slashings/mock/mock.go
@@ -40,10 +40,10 @@ func (*PoolMock) ConvertToElectra() {}

 // MarkIncludedAttesterSlashing --
 func (*PoolMock) MarkIncludedAttesterSlashing(_ ethpb.AttSlashing) {
-	panic("implement me")
+	panic("implement me") // lint:nopanic -- Test / mock code.
 }

 // MarkIncludedProposerSlashing --
 func (*PoolMock) MarkIncludedProposerSlashing(_ *ethpb.ProposerSlashing) {
-	panic("implement me")
+	panic("implement me") // lint:nopanic -- Test / mock code.
 }
--- a/beacon-chain/operations/voluntaryexits/mock/mock.go
+++ b/beacon-chain/operations/voluntaryexits/mock/mock.go
@@ -28,5 +28,5 @@ func (m *PoolMock) InsertVoluntaryExit(exit *eth.SignedVoluntaryExit) {

 // MarkIncluded --
 func (*PoolMock) MarkIncluded(_ *eth.SignedVoluntaryExit) {
-	panic("implement me")
+	panic("implement me") // lint:nopanic -- Mock / test code.
 }
--- a/beacon-chain/p2p/encoder/ssz.go
+++ b/beacon-chain/p2p/encoder/ssz.go
@@ -15,9 +15,8 @@ import (

 var _ NetworkEncoding = (*SszNetworkEncoder)(nil)

-// MaxGossipSize allowed for gossip messages.
-var MaxGossipSize = params.BeaconConfig().GossipMaxSize // 10 Mib.
-var MaxChunkSize = params.BeaconConfig().MaxChunkSize   // 10 Mib.
+// MaxPayloadSize allowed for gossip and rpc messages.
+var MaxPayloadSize = params.BeaconConfig().MaxPayloadSize // 10 Mib.

 // This pool defines the sync pool for our buffered snappy writers, so that they
 // can be constantly reused.
@@ -43,8 +42,8 @@ func (_ SszNetworkEncoder) EncodeGossip(w io.Writer, msg fastssz.Marshaler) (int
 	if err != nil {
 		return 0, err
 	}
-	if uint64(len(b)) > MaxGossipSize {
-		return 0, errors.Errorf("gossip message exceeds max gossip size: %d bytes > %d bytes", len(b), MaxGossipSize)
+	if uint64(len(b)) > MaxPayloadSize {
+		return 0, errors.Errorf("gossip message exceeds max gossip size: %d bytes > %d bytes", len(b), MaxPayloadSize)
 	}
 	b = snappy.Encode(nil /*dst*/, b)
 	return w.Write(b)
@@ -60,11 +59,11 @@ func (_ SszNetworkEncoder) EncodeWithMaxLength(w io.Writer, msg fastssz.Marshale
 	if err != nil {
 		return 0, err
 	}
-	if uint64(len(b)) > MaxChunkSize {
+	if uint64(len(b)) > MaxPayloadSize {
 		return 0, fmt.Errorf(
 			"size of encoded message is %d which is larger than the provided max limit of %d",
 			len(b),
-			MaxChunkSize,
+			MaxPayloadSize,
 		)
 	}
 	// write varint first
@@ -81,7 +80,10 @@ func doDecode(b []byte, to fastssz.Unmarshaler) error {

 // DecodeGossip decodes the bytes to the protobuf gossip message provided.
 func (_ SszNetworkEncoder) DecodeGossip(b []byte, to fastssz.Unmarshaler) error {
-	b, err := DecodeSnappy(b, MaxGossipSize)
+	if uint64(len(b)) > MaxCompressedLen(MaxPayloadSize) {
+		return fmt.Errorf("gossip message exceeds maximum compressed limit: %d", MaxCompressedLen(MaxPayloadSize))
+	}
+	b, err := DecodeSnappy(b, MaxPayloadSize)
 	if err != nil {
 		return err
 	}
@@ -111,11 +113,11 @@ func (e SszNetworkEncoder) DecodeWithMaxLength(r io.Reader, to fastssz.Unmarshal
 	if err != nil {
 		return err
 	}
-	if msgLen > MaxChunkSize {
+	if msgLen > MaxPayloadSize {
 		return fmt.Errorf(
 			"remaining bytes %d goes over the provided max limit of %d",
 			msgLen,
-			MaxChunkSize,
+			MaxPayloadSize,
 		)
 	}
 	msgMax, err := e.MaxLength(msgLen)
@@ -156,6 +158,18 @@ func (_ SszNetworkEncoder) MaxLength(length uint64) (int, error) {
 	return maxLen, nil
 }

+// MaxCompressedLen returns the maximum compressed size for a given payload size.
+//
+// Spec pseudocode definition:
+// def max_compressed_len(n: uint64) -> uint64:
+//
+//	# Worst-case compressed length for a given payload of size n when using snappy:
+//	# https://github.com/google/snappy/blob/32ded457c0b1fe78ceb8397632c416568d6714a0/snappy.cc#L218C1-L218C47
+//	return uint64(32 + n + n / 6)
+func MaxCompressedLen(n uint64) uint64 {
+	return 32 + n + n/6
+}
+
 // Writes a bytes value through a snappy buffered writer.
 func writeSnappyBuffer(w io.Writer, b []byte) (int, error) {
 	bufWriter := newBufferedWriter(w)
--- a/beacon-chain/p2p/encoder/ssz_test.go
+++ b/beacon-chain/p2p/encoder/ssz_test.go
@@ -555,11 +555,19 @@ func TestSszNetworkEncoder_FailsSnappyLength(t *testing.T) {
 	e := &encoder.SszNetworkEncoder{}
 	att := &ethpb.Fork{}
 	data := make([]byte, 32)
-	binary.PutUvarint(data, encoder.MaxGossipSize+32)
+	binary.PutUvarint(data, encoder.MaxPayloadSize+1)
 	err := e.DecodeGossip(data, att)
 	require.ErrorContains(t, "snappy message exceeds max size", err)
 }

+func TestSszNetworkEncoder_ExceedsMaxCompressedLimit(t *testing.T) {
+	e := &encoder.SszNetworkEncoder{}
+	att := &ethpb.Fork{}
+	data := make([]byte, encoder.MaxCompressedLen(encoder.MaxPayloadSize)+1)
+	err := e.DecodeGossip(data, att)
+	require.ErrorContains(t, "gossip message exceeds maximum compressed limit", err)
+}
+
 func testRoundTripWithLength(t *testing.T, e *encoder.SszNetworkEncoder) {
 	buf := new(bytes.Buffer)
 	msg := &ethpb.Fork{
@@ -604,31 +612,28 @@ func TestSszNetworkEncoder_EncodeWithMaxLength(t *testing.T) {
 	e := &encoder.SszNetworkEncoder{}
 	params.SetupTestConfigCleanup(t)
 	c := params.BeaconNetworkConfig()
-	encoder.MaxChunkSize = uint64(5)
+	encoder.MaxPayloadSize = uint64(5)
 	params.OverrideBeaconNetworkConfig(c)
 	_, err := e.EncodeWithMaxLength(buf, msg)
-	wanted := fmt.Sprintf("which is larger than the provided max limit of %d", encoder.MaxChunkSize)
+	wanted := fmt.Sprintf("which is larger than the provided max limit of %d", encoder.MaxPayloadSize)
 	assert.ErrorContains(t, wanted, err)
 }

 func TestSszNetworkEncoder_DecodeWithMaxLength(t *testing.T) {
 	buf := new(bytes.Buffer)
-	msg := &ethpb.Fork{
-		PreviousVersion: []byte("fooo"),
-		CurrentVersion:  []byte("barr"),
-		Epoch:           4242,
-	}
 	e := &encoder.SszNetworkEncoder{}
 	params.SetupTestConfigCleanup(t)
 	c := params.BeaconNetworkConfig()
-	maxChunkSize := uint64(5)
-	encoder.MaxChunkSize = maxChunkSize
-	params.OverrideBeaconNetworkConfig(c)
-	_, err := e.EncodeGossip(buf, msg)
+	maxPayloadSize := uint64(5)
+	encoder.MaxPayloadSize = maxPayloadSize
+	_, err := buf.Write(gogo.EncodeVarint(maxPayloadSize + 1))
 	require.NoError(t, err)
+	_, err = buf.Write(make([]byte, maxPayloadSize+1))
+	require.NoError(t, err)
+	params.OverrideBeaconNetworkConfig(c)
 	decoded := &ethpb.Fork{}
 	err = e.DecodeWithMaxLength(buf, decoded)
-	wanted := fmt.Sprintf("goes over the provided max limit of %d", maxChunkSize)
+	wanted := fmt.Sprintf("goes over the provided max limit of %d", maxPayloadSize)
 	assert.ErrorContains(t, wanted, err)
 }

@@ -639,8 +644,8 @@ func TestSszNetworkEncoder_DecodeWithMultipleFrames(t *testing.T) {
 	params.SetupTestConfigCleanup(t)
 	c := params.BeaconNetworkConfig()
 	// 4 * 1 Mib
-	maxChunkSize := uint64(1 << 22)
-	encoder.MaxChunkSize = maxChunkSize
+	maxPayloadSize := uint64(1 << 22)
+	encoder.MaxPayloadSize = maxPayloadSize
 	params.OverrideBeaconNetworkConfig(c)
 	_, err := e.EncodeWithMaxLength(buf, st.ToProtoUnsafe().(*ethpb.BeaconState))
 	require.NoError(t, err)
--- a/beacon-chain/p2p/message_id.go
+++ b/beacon-chain/p2p/message_id.go
@@ -50,7 +50,7 @@ func MsgID(genesisValidatorsRoot []byte, pmsg *pubsubpb.Message) string {
 	if fEpoch >= params.BeaconConfig().AltairForkEpoch {
 		return postAltairMsgID(pmsg, fEpoch)
 	}
-	decodedData, err := encoder.DecodeSnappy(pmsg.Data, params.BeaconConfig().GossipMaxSize)
+	decodedData, err := encoder.DecodeSnappy(pmsg.Data, params.BeaconConfig().MaxPayloadSize)
 	if err != nil {
 		combinedData := append(params.BeaconConfig().MessageDomainInvalidSnappy[:], pmsg.Data...)
 		h := hash.Hash(combinedData)
@@ -77,10 +77,9 @@ func postAltairMsgID(pmsg *pubsubpb.Message, fEpoch primitives.Epoch) string {
 	topicLen := len(topic)
 	topicLenBytes := bytesutil.Uint64ToBytesLittleEndian(uint64(topicLen)) // topicLen cannot be negative

-	// beyond Bellatrix epoch, allow 10 Mib gossip data size
-	gossipPubSubSize := params.BeaconConfig().GossipMaxSize
+	gossipPayloadSize := params.BeaconConfig().MaxPayloadSize

-	decodedData, err := encoder.DecodeSnappy(pmsg.Data, gossipPubSubSize)
+	decodedData, err := encoder.DecodeSnappy(pmsg.Data, gossipPayloadSize)
 	if err != nil {
 		totalLength, err := math.AddInt(
 			len(params.BeaconConfig().MessageDomainInvalidSnappy),
@@ -95,7 +94,7 @@ func postAltairMsgID(pmsg *pubsubpb.Message, fEpoch primitives.Epoch) string {
 			copy(msg, "invalid")
 			return bytesutil.UnsafeCastToString(msg)
 		}
-		if uint64(totalLength) > gossipPubSubSize {
+		if uint64(totalLength) > gossipPayloadSize {
 			// this should never happen
 			msg := make([]byte, 20)
 			copy(msg, "invalid")
--- a/beacon-chain/p2p/pubsub.go
+++ b/beacon-chain/p2p/pubsub.go
@@ -11,9 +11,11 @@ import (
 	pubsubpb "github.com/libp2p/go-libp2p-pubsub/pb"
 	"github.com/libp2p/go-libp2p/core/peer"
 	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/prysm/v5/beacon-chain/p2p/encoder"
 	"github.com/prysmaticlabs/prysm/v5/cmd/beacon-chain/flags"
 	"github.com/prysmaticlabs/prysm/v5/config/params"
 	"github.com/prysmaticlabs/prysm/v5/encoding/bytesutil"
+	mathutil "github.com/prysmaticlabs/prysm/v5/math"
 	pbrpc "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
 )

@@ -141,7 +143,7 @@ func (s *Service) pubsubOptions() []pubsub.Option {
 		}),
 		pubsub.WithSubscriptionFilter(s),
 		pubsub.WithPeerOutboundQueueSize(int(s.cfg.QueueSize)),
-		pubsub.WithMaxMessageSize(int(params.BeaconConfig().GossipMaxSize)),
+		pubsub.WithMaxMessageSize(int(MaxMessageSize())), // lint:ignore uintcast -- Max Message Size is a config value and is naturally bounded by networking limitations.
 		pubsub.WithValidateQueueSize(int(s.cfg.QueueSize)),
 		pubsub.WithPeerScore(peerScoringParams()),
 		pubsub.WithPeerScoreInspect(s.peerInspector, time.Minute),
@@ -235,3 +237,14 @@ func ExtractGossipDigest(topic string) ([4]byte, error) {
 	}
 	return bytesutil.ToBytes4(digest), nil
 }
+
+// MaxMessageSize returns the maximum allowed compressed message size.
+//
+// Spec pseudocode definition:
+// def max_message_size() -> uint64:
+//
+//	# Allow 1024 bytes for framing and encoding overhead but at least 1MiB in case MAX_PAYLOAD_SIZE is small.
+//	return max(max_compressed_len(MAX_PAYLOAD_SIZE) + 1024, 1024 * 1024)
+func MaxMessageSize() uint64 {
+	return mathutil.Max(encoder.MaxCompressedLen(params.BeaconConfig().MaxPayloadSize)+1024, 1024*1024)
+}
--- a/beacon-chain/p2p/types/object_mapping.go
+++ b/beacon-chain/p2p/types/object_mapping.go
@@ -33,6 +33,9 @@ var (
 	// AggregateAttestationMap maps the fork-version to the underlying data type for that
 	// particular fork period.
 	AggregateAttestationMap map[[4]byte]func() (ethpb.SignedAggregateAttAndProof, error)
+	// AttesterSlashingMap maps the fork-version to the underlying data type for that particular
+	// fork period.
+	AttesterSlashingMap map[[4]byte]func() (ethpb.AttSlashing, error)
 )

 // InitializeDataMaps initializes all the relevant object maps. This function is called to
@@ -151,4 +154,29 @@ func InitializeDataMaps() {
 			return &ethpb.SignedAggregateAttestationAndProofElectra{}, nil
 		},
 	}
+
+	// Reset our aggregate attestation map.
+	AttesterSlashingMap = map[[4]byte]func() (ethpb.AttSlashing, error){
+		bytesutil.ToBytes4(params.BeaconConfig().GenesisForkVersion): func() (ethpb.AttSlashing, error) {
+			return &ethpb.AttesterSlashing{}, nil
+		},
+		bytesutil.ToBytes4(params.BeaconConfig().AltairForkVersion): func() (ethpb.AttSlashing, error) {
+			return &ethpb.AttesterSlashing{}, nil
+		},
+		bytesutil.ToBytes4(params.BeaconConfig().BellatrixForkVersion): func() (ethpb.AttSlashing, error) {
+			return &ethpb.AttesterSlashing{}, nil
+		},
+		bytesutil.ToBytes4(params.BeaconConfig().CapellaForkVersion): func() (ethpb.AttSlashing, error) {
+			return &ethpb.AttesterSlashing{}, nil
+		},
+		bytesutil.ToBytes4(params.BeaconConfig().DenebForkVersion): func() (ethpb.AttSlashing, error) {
+			return &ethpb.AttesterSlashing{}, nil
+		},
+		bytesutil.ToBytes4(params.BeaconConfig().ElectraForkVersion): func() (ethpb.AttSlashing, error) {
+			return &ethpb.AttesterSlashingElectra{}, nil
+		},
+		bytesutil.ToBytes4(params.BeaconConfig().FuluForkVersion): func() (ethpb.AttSlashing, error) {
+			return &ethpb.AttesterSlashingElectra{}, nil
+		},
+	}
 }
--- a/beacon-chain/p2p/types/object_mapping_test.go
+++ b/beacon-chain/p2p/types/object_mapping_test.go
@@ -76,6 +76,13 @@ func TestInitializeDataMaps(t *testing.T) {
 				require.NoError(t, err)
 				assert.Equal(t, version.Phase0, agg.Version())
 			}
+			attSlashFunc, ok := AttesterSlashingMap[bytesutil.ToBytes4(params.BeaconConfig().GenesisForkVersion)]
+			assert.Equal(t, tt.exists, ok)
+			if tt.exists {
+				attSlash, err := attSlashFunc()
+				require.NoError(t, err)
+				assert.Equal(t, version.Phase0, attSlash.Version())
+			}
 		})
 	}
 }
--- a/beacon-chain/rpc/eth/beacon/handlers_pool.go
+++ b/beacon-chain/rpc/eth/beacon/handlers_pool.go
@@ -55,11 +55,7 @@ func (s *Server) ListAttestations(w http.ResponseWriter, r *http.Request) {
 		attestations = s.AttestationCache.GetAll()
 	} else {
 		attestations = s.AttestationsPool.AggregatedAttestations()
-		unaggAtts, err := s.AttestationsPool.UnaggregatedAttestations()
-		if err != nil {
-			httputil.HandleError(w, "Could not get unaggregated attestations: "+err.Error(), http.StatusInternalServerError)
-			return
-		}
+		unaggAtts := s.AttestationsPool.UnaggregatedAttestations()
 		attestations = append(attestations, unaggAtts...)
 	}

@@ -114,11 +110,7 @@ func (s *Server) ListAttestationsV2(w http.ResponseWriter, r *http.Request) {
 		attestations = s.AttestationCache.GetAll()
 	} else {
 		attestations = s.AttestationsPool.AggregatedAttestations()
-		unaggAtts, err := s.AttestationsPool.UnaggregatedAttestations()
-		if err != nil {
-			httputil.HandleError(w, "Could not get unaggregated attestations: "+err.Error(), http.StatusInternalServerError)
-			return
-		}
+		unaggAtts := s.AttestationsPool.UnaggregatedAttestations()
 		attestations = append(attestations, unaggAtts...)
 	}

@@ -633,7 +625,7 @@ func (s *Server) SubmitBLSToExecutionChanges(w http.ResponseWriter, r *http.Requ
 			toBroadcast = append(toBroadcast, sbls)
 		}
 	}
-	go s.broadcastBLSChanges(ctx, toBroadcast)
+	go s.broadcastBLSChanges(context.Background(), toBroadcast)
 	if len(failures) > 0 {
 		failuresErr := &server.IndexedVerificationFailureError{
 			Code:     http.StatusBadRequest,
--- a/beacon-chain/rpc/eth/config/handlers_test.go
+++ b/beacon-chain/rpc/eth/config/handlers_test.go
@@ -160,6 +160,8 @@ func TestGetSpec(t *testing.T) {
 	config.MaxTransactionsPerPayload = 99
 	config.FieldElementsPerBlob = 100
 	config.KzgCommitmentInclusionProofDepth = 101
+	config.BlobsidecarSubnetCount = 102
+	config.BlobsidecarSubnetCountElectra = 103

 	var dbp [4]byte
 	copy(dbp[:], []byte{'0', '0', '0', '1'})
@@ -198,7 +200,7 @@ func TestGetSpec(t *testing.T) {
 	data, ok := resp.Data.(map[string]interface{})
 	require.Equal(t, true, ok)

-	assert.Equal(t, 168, len(data))
+	assert.Equal(t, 169, len(data))
 	for k, v := range data {
 		t.Run(k, func(t *testing.T) {
 			switch k {
@@ -479,9 +481,7 @@ func TestGetSpec(t *testing.T) {
 				assert.Equal(t, "5", v)
 			case "MIN_EPOCHS_FOR_BLOCK_REQUESTS":
 				assert.Equal(t, "33024", v)
-			case "GOSSIP_MAX_SIZE":
-				assert.Equal(t, "10485760", v)
-			case "MAX_CHUNK_SIZE":
+			case "MAX_PAYLOAD_SIZE":
 				assert.Equal(t, "10485760", v)
 			case "ATTESTATION_SUBNET_COUNT":
 				assert.Equal(t, "64", v)
@@ -559,6 +559,10 @@ func TestGetSpec(t *testing.T) {
 				assert.Equal(t, "100", v)
 			case "KZG_COMMITMENT_INCLUSION_PROOF_DEPTH":
 				assert.Equal(t, "101", v)
+			case "BLOB_SIDECAR_SUBNET_COUNT":
+				assert.Equal(t, "102", v)
+			case "BLOB_SIDECAR_SUBNET_COUNT_ELECTRA":
+				assert.Equal(t, "103", v)
 			default:
 				t.Errorf("Incorrect key: %s", k)
 			}
--- a/beacon-chain/rpc/eth/debug/handlers.go
+++ b/beacon-chain/rpc/eth/debug/handlers.go
@@ -190,6 +190,7 @@ func (s *Server) GetForkChoice(w http.ResponseWriter, r *http.Request) {
 				Balance:                  fmt.Sprintf("%d", n.Balance),
 				ExecutionOptimistic:      n.ExecutionOptimistic,
 				TimeStamp:                fmt.Sprintf("%d", n.Timestamp),
+				Target:                   fmt.Sprintf("%#x", n.Target),
 			},
 		}
 	}
--- a/beacon-chain/rpc/eth/events/BUILD.bazel
+++ b/beacon-chain/rpc/eth/events/BUILD.bazel
@@ -18,7 +18,8 @@ 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/time:go_default_library",
+        "//beacon-chain/core/transition:go_default_library",
+        "//beacon-chain/state:go_default_library",
        "//config/params:go_default_library",
        "//consensus-types/interfaces:go_default_library",
        "//consensus-types/payload-attribute:go_default_library",
@@ -58,6 +59,7 @@ go_test(
        "//consensus-types/interfaces:go_default_library",
        "//consensus-types/payload-attribute:go_default_library",
        "//consensus-types/primitives:go_default_library",
+        "//proto/engine/v1:go_default_library",
        "//proto/eth/v1:go_default_library",
        "//proto/prysm/v1alpha1:go_default_library",
        "//testing/require:go_default_library",
--- a/beacon-chain/rpc/eth/events/events.go
+++ b/beacon-chain/rpc/eth/events/events.go
@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"runtime/debug"
 	"strconv"
 	"time"

@@ -20,7 +21,8 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/feed/operation"
 	statefeed "github.com/prysmaticlabs/prysm/v5/beacon-chain/core/feed/state"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/helpers"
-	chaintime "github.com/prysmaticlabs/prysm/v5/beacon-chain/core/time"
+	"github.com/prysmaticlabs/prysm/v5/beacon-chain/core/transition"
+	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state"
 	"github.com/prysmaticlabs/prysm/v5/config/params"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
 	payloadattribute "github.com/prysmaticlabs/prysm/v5/consensus-types/payload-attribute"
@@ -43,6 +45,8 @@ const (
 	HeadTopic = "head"
 	// BlockTopic represents a new produced block event topic.
 	BlockTopic = "block"
+	// BlockGossipTopic represents a block received from gossip or API that passes validation rules.
+	BlockGossipTopic = "block_gossip"
 	// AttestationTopic represents a new submitted attestation event topic.
 	AttestationTopic = "attestation"
 	// SingleAttestationTopic represents a new submitted single attestation event topic.
@@ -101,6 +105,7 @@ var opsFeedEventTopics = map[feed.EventType]string{
 	operation.BlobSidecarReceived:               BlobSidecarTopic,
 	operation.AttesterSlashingReceived:          AttesterSlashingTopic,
 	operation.ProposerSlashingReceived:          ProposerSlashingTopic,
+	operation.BlockGossipReceived:               BlockGossipTopic,
 }

 var stateFeedEventTopics = map[feed.EventType]string{
@@ -352,9 +357,18 @@ func writeLazyReaderWithRecover(w *streamingResponseWriterController, lr lazyRea
 		if r := recover(); r != nil {
 			log.WithField("panic", r).Error("Recovered from panic while writing event to client.")
 			err = errWriterUnusable
+			debug.PrintStack()
 		}
 	}()
+	if lr == nil {
+		log.Warn("Event stream skipping a nil lazy event reader callback")
+		return nil
+	}
 	r := lr()
+	if r == nil {
+		log.Warn("Event stream skipping a nil event reader")
+		return nil
+	}
 	out, err := io.ReadAll(r)
 	if err != nil {
 		return err
@@ -432,6 +446,8 @@ func topicForEvent(event *feed.Event) string {
 		return AttesterSlashingTopic
 	case *operation.ProposerSlashingReceivedData:
 		return ProposerSlashingTopic
+	case *operation.BlockGossipReceivedData:
+		return BlockGossipTopic
 	case *ethpb.EventHead:
 		return HeadTopic
 	case *ethpb.EventFinalizedCheckpoint:
@@ -468,6 +484,18 @@ func (s *Server) lazyReaderForEvent(ctx context.Context, event *feed.Event, topi
 		return func() io.Reader {
 			return jsonMarshalReader(eventName, structs.HeadEventFromV1(v))
 		}, nil
+	case *operation.BlockGossipReceivedData:
+		blockRoot, err := v.SignedBlock.Block().HashTreeRoot()
+		if err != nil {
+			return nil, errors.Wrap(err, "could not compute block root for BlockGossipReceivedData")
+		}
+		return func() io.Reader {
+			blk := &structs.BlockGossipEvent{
+				Slot:  fmt.Sprintf("%d", v.SignedBlock.Block().Slot()),
+				Block: hexutil.Encode(blockRoot[:]),
+			}
+			return jsonMarshalReader(eventName, blk)
+		}, nil
 	case *operation.AggregatedAttReceivedData:
 		switch att := v.Attestation.AggregateVal().(type) {
 		case *eth.Attestation:
@@ -600,27 +628,14 @@ func (s *Server) lazyReaderForEvent(ctx context.Context, event *feed.Event, topi

 var errUnsupportedPayloadAttribute = errors.New("cannot compute payload attributes pre-Bellatrix")

-func (s *Server) computePayloadAttributes(ctx context.Context, ev payloadattribute.EventData) (payloadattribute.Attributer, error) {
-	v := ev.HeadState.Version()
+func (s *Server) computePayloadAttributes(ctx context.Context, st state.ReadOnlyBeaconState, root [32]byte, proposer primitives.ValidatorIndex, timestamp uint64, randao []byte) (payloadattribute.Attributer, error) {
+	v := st.Version()
 	if v < version.Bellatrix {
 		return nil, errors.Wrapf(errUnsupportedPayloadAttribute, "%s is not supported", version.String(v))
 	}

-	t, err := slots.ToTime(ev.HeadState.GenesisTime(), ev.HeadState.Slot())
-	if err != nil {
-		return nil, errors.Wrap(err, "could not get head state slot time")
-	}
-	timestamp := uint64(t.Unix())
-	prevRando, err := helpers.RandaoMix(ev.HeadState, chaintime.CurrentEpoch(ev.HeadState))
-	if err != nil {
-		return nil, errors.Wrap(err, "could not get head state randao mix")
-	}
-	proposerIndex, err := helpers.BeaconProposerIndex(ctx, ev.HeadState)
-	if err != nil {
-		return nil, errors.Wrap(err, "could not get head state proposer index")
-	}
 	feeRecpt := params.BeaconConfig().DefaultFeeRecipient.Bytes()
-	tValidator, exists := s.TrackedValidatorsCache.Validator(proposerIndex)
+	tValidator, exists := s.TrackedValidatorsCache.Validator(proposer)
 	if exists {
 		feeRecpt = tValidator.FeeRecipient[:]
 	}
@@ -628,34 +643,30 @@ func (s *Server) computePayloadAttributes(ctx context.Context, ev payloadattribu
 	if v == version.Bellatrix {
 		return payloadattribute.New(&engine.PayloadAttributes{
 			Timestamp:             timestamp,
-			PrevRandao:            prevRando,
+			PrevRandao:            randao,
 			SuggestedFeeRecipient: feeRecpt,
 		})
 	}

-	w, _, err := ev.HeadState.ExpectedWithdrawals()
+	w, _, err := st.ExpectedWithdrawals()
 	if err != nil {
 		return nil, errors.Wrap(err, "could not get withdrawals from head state")
 	}
 	if v == version.Capella {
 		return payloadattribute.New(&engine.PayloadAttributesV2{
 			Timestamp:             timestamp,
-			PrevRandao:            prevRando,
+			PrevRandao:            randao,
 			SuggestedFeeRecipient: feeRecpt,
 			Withdrawals:           w,
 		})
 	}

-	pr, err := ev.HeadBlock.Block().HashTreeRoot()
-	if err != nil {
-		return nil, errors.Wrap(err, "could not compute head block root")
-	}
 	return payloadattribute.New(&engine.PayloadAttributesV3{
 		Timestamp:             timestamp,
-		PrevRandao:            prevRando,
+		PrevRandao:            randao,
 		SuggestedFeeRecipient: feeRecpt,
 		Withdrawals:           w,
-		ParentBeaconBlockRoot: pr[:],
+		ParentBeaconBlockRoot: root[:],
 	})
 }

@@ -665,37 +676,75 @@ type asyncPayloadAttrData struct {
 	err     error
 }

+var zeroRoot [32]byte
+
+// needsFill allows tests to provide filled EventData values. An ordinary event data value fired by the blockchain package will have
+// all of the checked fields empty, so the logical short circuit should hit immediately.
+func needsFill(ev payloadattribute.EventData) bool {
+	return ev.HeadState == nil || ev.HeadState.IsNil() || ev.HeadState.LatestBlockHeader() == nil ||
+		ev.HeadBlock == nil || ev.HeadBlock.IsNil() ||
+		ev.HeadRoot == zeroRoot || len(ev.ParentBlockRoot) == 0 || len(ev.ParentBlockHash) == 0 ||
+		ev.Attributer == nil || ev.Attributer.IsEmpty()
+}
+
 func (s *Server) fillEventData(ctx context.Context, ev payloadattribute.EventData) (payloadattribute.EventData, error) {
-	if ev.HeadBlock == nil || ev.HeadBlock.IsNil() {
-		hb, err := s.HeadFetcher.HeadBlock(ctx)
-		if err != nil {
-			return ev, errors.Wrap(err, "Could not look up head block")
-		}
-		root, err := hb.Block().HashTreeRoot()
-		if err != nil {
-			return ev, errors.Wrap(err, "Could not compute head block root")
-		}
-		if ev.HeadRoot != root {
-			return ev, errors.Wrap(err, "head root changed before payload attribute event handler execution")
-		}
-		ev.HeadBlock = hb
-		payload, err := hb.Block().Body().Execution()
-		if err != nil {
-			return ev, errors.Wrap(err, "Could not get execution payload for head block")
-		}
-		ev.ParentBlockHash = payload.BlockHash()
-		ev.ParentBlockNumber = payload.BlockNumber()
+	var err error
+
+	if !needsFill(ev) {
+		return ev, nil
 	}

-	attr := ev.Attributer
-	if attr == nil || attr.IsEmpty() {
-		attr, err := s.computePayloadAttributes(ctx, ev)
-		if err != nil {
-			return ev, errors.Wrap(err, "Could not compute payload attributes")
-		}
-		ev.Attributer = attr
+	ev.HeadState, err = s.HeadFetcher.HeadState(ctx)
+	if err != nil {
+		return ev, errors.Wrap(err, "could not get head state")
 	}
-	return ev, nil
+
+	ev.HeadBlock, err = s.HeadFetcher.HeadBlock(ctx)
+	if err != nil {
+		return ev, errors.Wrap(err, "could not look up head block")
+	}
+	ev.HeadRoot, err = ev.HeadBlock.Block().HashTreeRoot()
+	if err != nil {
+		return ev, errors.Wrap(err, "could not compute head block root")
+	}
+	pr := ev.HeadBlock.Block().ParentRoot()
+	ev.ParentBlockRoot = pr[:]
+
+	hsr, err := ev.HeadState.LatestBlockHeader().HashTreeRoot()
+	if err != nil {
+		return ev, errors.Wrap(err, "could not compute latest block header root")
+	}
+
+	pse := slots.ToEpoch(ev.ProposalSlot)
+	st := ev.HeadState
+	if slots.ToEpoch(st.Slot()) != pse {
+		st, err = transition.ProcessSlotsUsingNextSlotCache(ctx, st, hsr[:], ev.ProposalSlot)
+		if err != nil {
+			return ev, errors.Wrap(err, "could not run process blocks on head state into the proposal slot epoch")
+		}
+	}
+	ev.ProposerIndex, err = helpers.BeaconProposerIndexAtSlot(ctx, st, ev.ProposalSlot)
+	if err != nil {
+		return ev, errors.Wrap(err, "failed to compute proposer index")
+	}
+	randao, err := helpers.RandaoMix(st, pse)
+	if err != nil {
+		return ev, errors.Wrap(err, "could not get head state randado")
+	}
+
+	payload, err := ev.HeadBlock.Block().Body().Execution()
+	if err != nil {
+		return ev, errors.Wrap(err, "could not get execution payload for head block")
+	}
+	ev.ParentBlockHash = payload.BlockHash()
+	ev.ParentBlockNumber = payload.BlockNumber()
+
+	t, err := slots.ToTime(st.GenesisTime(), ev.ProposalSlot)
+	if err != nil {
+		return ev, errors.Wrap(err, "could not get head state slot time")
+	}
+	ev.Attributer, err = s.computePayloadAttributes(ctx, st, hsr, ev.ProposerIndex, uint64(t.Unix()), randao)
+	return ev, err
 }

 // This event stream is intended to be used by builders and relays.
@@ -704,10 +753,7 @@ func (s *Server) payloadAttributesReader(ctx context.Context, ev payloadattribut
 	ctx, cancel := context.WithTimeout(ctx, payloadAttributeTimeout)
 	edc := make(chan asyncPayloadAttrData)
 	go func() {
-		d := asyncPayloadAttrData{
-			version: version.String(ev.HeadState.Version()),
-		}
-
+		d := asyncPayloadAttrData{}
 		defer func() {
 			edc <- d
 		}()
@@ -716,6 +762,7 @@ func (s *Server) payloadAttributesReader(ctx context.Context, ev payloadattribut
 			d.err = errors.Wrap(err, "Could not fill event data")
 			return
 		}
+		d.version = version.String(ev.HeadBlock.Version())
 		attributesBytes, err := marshalAttributes(ev.Attributer)
 		if err != nil {
 			d.err = errors.Wrap(err, "errors marshaling payload attributes to json")
--- a/beacon-chain/rpc/eth/events/events_test.go
+++ b/beacon-chain/rpc/eth/events/events_test.go
@@ -2,6 +2,7 @@ package events

 import (
 	"context"
+	"encoding/binary"
 	"fmt"
 	"io"
 	"math"
@@ -24,6 +25,7 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
 	payloadattribute "github.com/prysmaticlabs/prysm/v5/consensus-types/payload-attribute"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
+	enginev1 "github.com/prysmaticlabs/prysm/v5/proto/engine/v1"
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/eth/v1"
 	eth "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/v5/testing/require"
@@ -117,12 +119,19 @@ func operationEventsFixtures(t *testing.T) (*topicRequest, []*feed.Event) {
 		BlobSidecarTopic,
 		AttesterSlashingTopic,
 		ProposerSlashingTopic,
+		BlockGossipTopic,
 	})
 	require.NoError(t, err)
 	ro, err := blocks.NewROBlob(util.HydrateBlobSidecar(&eth.BlobSidecar{}))
 	require.NoError(t, err)
 	vblob := blocks.NewVerifiedROBlob(ro)

+	// Create a test block for block gossip event
+	block := util.NewBeaconBlock()
+	block.Block.Slot = 123
+	signedBlock, err := blocks.NewSignedBeaconBlock(block)
+	require.NoError(t, err)
+
 	return topics, []*feed.Event{
 		{
 			Type: operation.UnaggregatedAttReceived,
@@ -285,6 +294,12 @@ func operationEventsFixtures(t *testing.T) (*topicRequest, []*feed.Event) {
 				},
 			},
 		},
+		{
+			Type: operation.BlockGossipReceived,
+			Data: &operation.BlockGossipReceivedData{
+				SignedBlock: signedBlock,
+			},
+		},
 	}
 }

@@ -557,6 +572,110 @@ func TestStreamEvents_OperationsEvents(t *testing.T) {
 	})
 }

+func TestFillEventData(t *testing.T) {
+	ctx := context.Background()
+	t.Run("AlreadyFilledData_ShouldShortCircuitWithoutError", func(t *testing.T) {
+		st, err := util.NewBeaconStateBellatrix()
+		require.NoError(t, err)
+		b, err := blocks.NewSignedBeaconBlock(util.HydrateSignedBeaconBlockBellatrix(&eth.SignedBeaconBlockBellatrix{}))
+		require.NoError(t, err)
+		attributor, err := payloadattribute.New(&enginev1.PayloadAttributes{
+			Timestamp: uint64(time.Now().Unix()),
+		})
+		require.NoError(t, err)
+		alreadyFilled := payloadattribute.EventData{
+			HeadState:       st,
+			HeadBlock:       b,
+			HeadRoot:        [32]byte{1, 2, 3},
+			Attributer:      attributor,
+			ParentBlockRoot: []byte{1, 2, 3},
+			ParentBlockHash: []byte{4, 5, 6},
+		}
+		srv := &Server{} // No real HeadFetcher needed here since it won't be called.
+		result, err := srv.fillEventData(ctx, alreadyFilled)
+		require.NoError(t, err)
+		require.DeepEqual(t, alreadyFilled, result)
+	})
+	t.Run("Electra PartialData_ShouldFetchHeadStateAndBlock", func(t *testing.T) {
+		st, err := util.NewBeaconStateElectra()
+		require.NoError(t, err)
+		valCount := 10
+		setActiveValidators(t, st, valCount)
+		inactivityScores := make([]uint64, valCount)
+		for i := range inactivityScores {
+			inactivityScores[i] = 10
+		}
+		require.NoError(t, st.SetInactivityScores(inactivityScores))
+		b, err := blocks.NewSignedBeaconBlock(util.HydrateSignedBeaconBlockElectra(&eth.SignedBeaconBlockElectra{}))
+		require.NoError(t, err)
+		attributor, err := payloadattribute.New(&enginev1.PayloadAttributes{
+			Timestamp: uint64(time.Now().Unix()),
+		})
+		require.NoError(t, err)
+		// Create an event data object missing certain fields:
+		partial := payloadattribute.EventData{
+			// The presence of a nil HeadState, nil HeadBlock, zeroed HeadRoot, etc.
+			// will cause fillEventData to try to fill the values.
+			ProposalSlot: 42,         // different epoch from current slot
+			Attributer:   attributor, // Must be Bellatrix or later
+		}
+		currentSlot := primitives.Slot(0)
+		// to avoid slot processing
+		require.NoError(t, st.SetSlot(currentSlot+1))
+		mockChainService := &mockChain.ChainService{
+			Root:  make([]byte, 32),
+			State: st,
+			Block: b,
+			Slot:  &currentSlot,
+		}
+
+		stn := mockChain.NewEventFeedWrapper()
+		opn := mockChain.NewEventFeedWrapper()
+		srv := &Server{
+			StateNotifier:          &mockChain.SimpleNotifier{Feed: stn},
+			OperationNotifier:      &mockChain.SimpleNotifier{Feed: opn},
+			HeadFetcher:            mockChainService,
+			ChainInfoFetcher:       mockChainService,
+			TrackedValidatorsCache: cache.NewTrackedValidatorsCache(),
+			EventWriteTimeout:      testEventWriteTimeout,
+		}
+
+		filled, err := srv.fillEventData(ctx, partial)
+		require.NoError(t, err, "expected successful fill of partial event data")
+
+		// Verify that fields have been updated from the mock data:
+		require.NotNil(t, filled.HeadState, "HeadState should be assigned")
+		require.NotNil(t, filled.HeadBlock, "HeadBlock should be assigned")
+		require.NotEqual(t, [32]byte{}, filled.HeadRoot, "HeadRoot should no longer be zero")
+		require.NotEmpty(t, filled.ParentBlockRoot, "ParentBlockRoot should be filled")
+		require.NotEmpty(t, filled.ParentBlockHash, "ParentBlockHash should be filled")
+		require.Equal(t, uint64(0), filled.ParentBlockNumber, "ParentBlockNumber must match mock block")
+
+		// Check that a valid Attributer was set:
+		require.NotNil(t, filled.Attributer, "Should have a valid payload attributes object")
+		require.Equal(t, false, filled.Attributer.IsEmpty(), "Attributer should not be empty after fill")
+	})
+}
+
+func setActiveValidators(t *testing.T, st state.BeaconState, count int) {
+	balances := make([]uint64, count)
+	validators := make([]*eth.Validator, 0, count)
+	for i := 0; i < count; i++ {
+		pubKey := make([]byte, params.BeaconConfig().BLSPubkeyLength)
+		binary.LittleEndian.PutUint64(pubKey, uint64(i))
+		balances[i] = uint64(i)
+		validators = append(validators, &eth.Validator{
+			PublicKey:             pubKey,
+			ActivationEpoch:       0,
+			ExitEpoch:             params.BeaconConfig().FarFutureEpoch,
+			WithdrawalCredentials: make([]byte, 32),
+		})
+	}
+
+	require.NoError(t, st.SetValidators(validators))
+	require.NoError(t, st.SetBalances(balances))
+}
+
 func TestStuckReaderScenarios(t *testing.T) {
 	cases := []struct {
 		name       string
@@ -584,7 +703,7 @@ func TestStuckReaderScenarios(t *testing.T) {

 func wedgedWriterTestCase(t *testing.T, queueDepth func([]*feed.Event) int) {
 	topics, events := operationEventsFixtures(t)
-	require.Equal(t, 10, len(events))
+	require.Equal(t, 11, len(events))

 	// set eventFeedDepth to a number lower than the events we intend to send to force the server to drop the reader.
 	stn := mockChain.NewEventFeedWrapper()
--- a/beacon-chain/rpc/eth/light-client/BUILD.bazel
+++ b/beacon-chain/rpc/eth/light-client/BUILD.bazel
@@ -4,7 +4,6 @@ go_library(
    name = "go_default_library",
    srcs = [
        "handlers.go",
-        "helpers.go",
        "server.go",
    ],
    importpath = "github.com/prysmaticlabs/prysm/v5/beacon-chain/rpc/eth/light-client",
@@ -17,11 +16,9 @@ go_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",
        "//config/features:go_default_library",
        "//config/params:go_default_library",
        "//consensus-types/interfaces:go_default_library",
-        "//consensus-types/primitives:go_default_library",
        "//monitoring/tracing/trace:go_default_library",
        "//network/httputil:go_default_library",
        "//runtime/version:go_default_library",
--- a/beacon-chain/rpc/eth/light-client/handlers.go
+++ b/beacon-chain/rpc/eth/light-client/handlers.go
@@ -10,6 +10,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/prysmaticlabs/prysm/v5/api"
 	"github.com/prysmaticlabs/prysm/v5/api/server/structs"
+	lightclient "github.com/prysmaticlabs/prysm/v5/beacon-chain/core/light-client"
 	"github.com/prysmaticlabs/prysm/v5/beacon-chain/rpc/eth/shared"
 	"github.com/prysmaticlabs/prysm/v5/config/features"
 	"github.com/prysmaticlabs/prysm/v5/config/params"
@@ -182,18 +183,31 @@ func (s *Server) GetLightClientFinalityUpdate(w http.ResponseWriter, req *http.R
 		return
 	}

-	update, err := newLightClientFinalityUpdateFromBeaconState(ctx, s.ChainInfoFetcher.CurrentSlot(), st, block, attestedState, attestedBlock, finalizedBlock)
+	update, err := lightclient.NewLightClientFinalityUpdateFromBeaconState(ctx, s.ChainInfoFetcher.CurrentSlot(), st, block, attestedState, attestedBlock, finalizedBlock)
 	if err != nil {
 		httputil.HandleError(w, "Could not get light client finality update: "+err.Error(), http.StatusInternalServerError)
 		return
 	}

-	response := &structs.LightClientFinalityUpdateResponse{
-		Version: version.String(attestedState.Version()),
-		Data:    update,
+	if httputil.RespondWithSsz(req) {
+		ssz, err := update.MarshalSSZ()
+		if err != nil {
+			httputil.HandleError(w, "Could not marshal finality update to SSZ: "+err.Error(), http.StatusInternalServerError)
+			return
+		}
+		httputil.WriteSsz(w, ssz, "light_client_finality_update.ssz")
+	} else {
+		updateStruct, err := structs.LightClientFinalityUpdateFromConsensus(update)
+		if err != nil {
+			httputil.HandleError(w, "Could not convert light client finality update to API struct: "+err.Error(), http.StatusInternalServerError)
+			return
+		}
+		response := &structs.LightClientFinalityUpdateResponse{
+			Version: version.String(attestedState.Version()),
+			Data:    updateStruct,
+		}
+		httputil.WriteJson(w, response)
 	}
-
-	httputil.WriteJson(w, response)
 }

 // GetLightClientOptimisticUpdate - implements https://github.com/ethereum/beacon-APIs/blob/263f4ed6c263c967f13279c7a9f5629b51c5fc55/apis/beacon/light_client/optimistic_update.yaml
@@ -232,18 +246,31 @@ func (s *Server) GetLightClientOptimisticUpdate(w http.ResponseWriter, req *http
 		return
 	}

-	update, err := newLightClientOptimisticUpdateFromBeaconState(ctx, s.ChainInfoFetcher.CurrentSlot(), st, block, attestedState, attestedBlock)
+	update, err := lightclient.NewLightClientOptimisticUpdateFromBeaconState(ctx, s.ChainInfoFetcher.CurrentSlot(), st, block, attestedState, attestedBlock)
 	if err != nil {
 		httputil.HandleError(w, "Could not get light client optimistic update: "+err.Error(), http.StatusInternalServerError)
 		return
 	}

-	response := &structs.LightClientOptimisticUpdateResponse{
-		Version: version.String(attestedState.Version()),
-		Data:    update,
+	if httputil.RespondWithSsz(req) {
+		ssz, err := update.MarshalSSZ()
+		if err != nil {
+			httputil.HandleError(w, "Could not marshal optimistic update to SSZ: "+err.Error(), http.StatusInternalServerError)
+			return
+		}
+		httputil.WriteSsz(w, ssz, "light_client_optimistic_update.ssz")
+	} else {
+		updateStruct, err := structs.LightClientOptimisticUpdateFromConsensus(update)
+		if err != nil {
+			httputil.HandleError(w, "Could not convert light client optimistic update to API struct: "+err.Error(), http.StatusInternalServerError)
+			return
+		}
+		response := &structs.LightClientOptimisticUpdateResponse{
+			Version: version.String(attestedState.Version()),
+			Data:    updateStruct,
+		}
+		httputil.WriteJson(w, response)
 	}
-
-	httputil.WriteJson(w, response)
 }

 // suitableBlock returns the latest block that satisfies all criteria required for creating a new update
--- a/beacon-chain/rpc/eth/light-client/handlers_test.go
+++ b/beacon-chain/rpc/eth/light-client/handlers_test.go
@@ -1105,116 +1105,226 @@ func TestLightClientHandler_GetLightClientFinalityUpdate(t *testing.T) {
 		EnableLightClient: true,
 	})
 	defer resetFn()
-
 	helpers.ClearCache()
-	ctx := context.Background()
 	config := params.BeaconConfig()
-	slot := primitives.Slot(config.AltairForkEpoch * primitives.Epoch(config.SlotsPerEpoch)).Add(1)

-	attestedState, err := util.NewBeaconStateAltair()
-	require.NoError(t, err)
-	err = attestedState.SetSlot(slot.Sub(1))
-	require.NoError(t, err)
+	t.Run("altair", func(t *testing.T) {
+		ctx := context.Background()
+		slot := primitives.Slot(config.AltairForkEpoch * primitives.Epoch(config.SlotsPerEpoch)).Add(1)

-	require.NoError(t, attestedState.SetFinalizedCheckpoint(&pb.Checkpoint{
-		Epoch: config.AltairForkEpoch - 10,
-		Root:  make([]byte, 32),
-	}))
+		attestedState, err := util.NewBeaconStateAltair()
+		require.NoError(t, err)
+		err = attestedState.SetSlot(slot.Sub(1))
+		require.NoError(t, err)

-	parent := util.NewBeaconBlockAltair()
-	parent.Block.Slot = slot.Sub(1)
+		require.NoError(t, attestedState.SetFinalizedCheckpoint(&pb.Checkpoint{
+			Epoch: config.AltairForkEpoch - 10,
+			Root:  make([]byte, 32),
+		}))

-	signedParent, err := blocks.NewSignedBeaconBlock(parent)
-	require.NoError(t, err)
+		parent := util.NewBeaconBlockAltair()
+		parent.Block.Slot = slot.Sub(1)

-	parentHeader, err := signedParent.Header()
-	require.NoError(t, err)
-	attestedHeader := parentHeader.Header
+		signedParent, err := blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)

-	err = attestedState.SetLatestBlockHeader(attestedHeader)
-	require.NoError(t, err)
-	attestedStateRoot, err := attestedState.HashTreeRoot(ctx)
-	require.NoError(t, err)
+		parentHeader, err := signedParent.Header()
+		require.NoError(t, err)
+		attestedHeader := parentHeader.Header

-	// get a new signed block so the root is updated with the new state root
-	parent.Block.StateRoot = attestedStateRoot[:]
-	signedParent, err = blocks.NewSignedBeaconBlock(parent)
-	require.NoError(t, err)
+		err = attestedState.SetLatestBlockHeader(attestedHeader)
+		require.NoError(t, err)
+		attestedStateRoot, err := attestedState.HashTreeRoot(ctx)
+		require.NoError(t, err)

-	st, err := util.NewBeaconStateAltair()
-	require.NoError(t, err)
-	err = st.SetSlot(slot)
-	require.NoError(t, err)
+		// get a new signed block so the root is updated with the new state root
+		parent.Block.StateRoot = attestedStateRoot[:]
+		signedParent, err = blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)

-	parentRoot, err := signedParent.Block().HashTreeRoot()
-	require.NoError(t, err)
+		st, err := util.NewBeaconStateAltair()
+		require.NoError(t, err)
+		err = st.SetSlot(slot)
+		require.NoError(t, err)

-	block := util.NewBeaconBlockAltair()
-	block.Block.Slot = slot
-	block.Block.ParentRoot = parentRoot[:]
+		parentRoot, err := signedParent.Block().HashTreeRoot()
+		require.NoError(t, err)

-	for i := uint64(0); i < config.SyncCommitteeSize; i++ {
-		block.Block.Body.SyncAggregate.SyncCommitteeBits.SetBitAt(i, true)
-	}
+		block := util.NewBeaconBlockAltair()
+		block.Block.Slot = slot
+		block.Block.ParentRoot = parentRoot[:]

-	signedBlock, err := blocks.NewSignedBeaconBlock(block)
-	require.NoError(t, err)
+		for i := uint64(0); i < config.SyncCommitteeSize; i++ {
+			block.Block.Body.SyncAggregate.SyncCommitteeBits.SetBitAt(i, true)
+		}

-	h, err := signedBlock.Header()
-	require.NoError(t, err)
+		signedBlock, err := blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)

-	err = st.SetLatestBlockHeader(h.Header)
-	require.NoError(t, err)
-	stateRoot, err := st.HashTreeRoot(ctx)
-	require.NoError(t, err)
+		h, err := signedBlock.Header()
+		require.NoError(t, err)

-	// get a new signed block so the root is updated with the new state root
-	block.Block.StateRoot = stateRoot[:]
-	signedBlock, err = blocks.NewSignedBeaconBlock(block)
-	require.NoError(t, err)
+		err = st.SetLatestBlockHeader(h.Header)
+		require.NoError(t, err)
+		stateRoot, err := st.HashTreeRoot(ctx)
+		require.NoError(t, err)

-	root, err := block.Block.HashTreeRoot()
-	require.NoError(t, err)
+		// get a new signed block so the root is updated with the new state root
+		block.Block.StateRoot = stateRoot[:]
+		signedBlock, err = blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)

-	mockBlocker := &testutil.MockBlocker{
-		RootBlockMap: map[[32]byte]interfaces.ReadOnlySignedBeaconBlock{
-			parentRoot: signedParent,
-			root:       signedBlock,
-		},
-		SlotBlockMap: map[primitives.Slot]interfaces.ReadOnlySignedBeaconBlock{
-			slot.Sub(1): signedParent,
-			slot:        signedBlock,
-		},
-	}
-	mockChainService := &mock.ChainService{Optimistic: true, Slot: &slot, State: st, FinalizedRoots: map[[32]byte]bool{
-		root: true,
-	}}
-	mockChainInfoFetcher := &mock.ChainService{Slot: &slot}
-	s := &Server{
-		Stater: &testutil.MockStater{StatesBySlot: map[primitives.Slot]state.BeaconState{
-			slot.Sub(1): attestedState,
-			slot:        st,
-		}},
-		Blocker:          mockBlocker,
-		HeadFetcher:      mockChainService,
-		ChainInfoFetcher: mockChainInfoFetcher,
-	}
-	request := httptest.NewRequest("GET", "http://foo.com", nil)
-	writer := httptest.NewRecorder()
-	writer.Body = &bytes.Buffer{}
+		root, err := block.Block.HashTreeRoot()
+		require.NoError(t, err)

-	s.GetLightClientFinalityUpdate(writer, request)
+		mockBlocker := &testutil.MockBlocker{
+			RootBlockMap: map[[32]byte]interfaces.ReadOnlySignedBeaconBlock{
+				parentRoot: signedParent,
+				root:       signedBlock,
+			},
+			SlotBlockMap: map[primitives.Slot]interfaces.ReadOnlySignedBeaconBlock{
+				slot.Sub(1): signedParent,
+				slot:        signedBlock,
+			},
+		}
+		mockChainService := &mock.ChainService{Optimistic: true, Slot: &slot, State: st, FinalizedRoots: map[[32]byte]bool{
+			root: true,
+		}}
+		mockChainInfoFetcher := &mock.ChainService{Slot: &slot}
+		s := &Server{
+			Stater: &testutil.MockStater{StatesBySlot: map[primitives.Slot]state.BeaconState{
+				slot.Sub(1): attestedState,
+				slot:        st,
+			}},
+			Blocker:          mockBlocker,
+			HeadFetcher:      mockChainService,
+			ChainInfoFetcher: mockChainInfoFetcher,
+		}
+		request := httptest.NewRequest("GET", "http://foo.com", nil)
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}

-	require.Equal(t, http.StatusOK, writer.Code)
-	var resp *structs.LightClientUpdateResponse
-	err = json.Unmarshal(writer.Body.Bytes(), &resp)
-	require.NoError(t, err)
-	var respHeader structs.LightClientHeader
-	err = json.Unmarshal(resp.Data.AttestedHeader, &respHeader)
-	require.NoError(t, err)
-	require.Equal(t, "altair", resp.Version)
-	require.Equal(t, hexutil.Encode(attestedHeader.BodyRoot), respHeader.Beacon.BodyRoot)
-	require.NotNil(t, resp.Data)
+		s.GetLightClientFinalityUpdate(writer, request)
+
+		require.Equal(t, http.StatusOK, writer.Code)
+		var resp *structs.LightClientUpdateResponse
+		err = json.Unmarshal(writer.Body.Bytes(), &resp)
+		require.NoError(t, err)
+		var respHeader structs.LightClientHeader
+		err = json.Unmarshal(resp.Data.AttestedHeader, &respHeader)
+		require.NoError(t, err)
+		require.Equal(t, "altair", resp.Version)
+		require.Equal(t, hexutil.Encode(attestedHeader.BodyRoot), respHeader.Beacon.BodyRoot)
+		require.NotNil(t, resp.Data)
+	})
+
+	t.Run("altair SSZ", func(t *testing.T) {
+		ctx := context.Background()
+		slot := primitives.Slot(config.AltairForkEpoch * primitives.Epoch(config.SlotsPerEpoch)).Add(1)
+
+		attestedState, err := util.NewBeaconStateAltair()
+		require.NoError(t, err)
+		err = attestedState.SetSlot(slot.Sub(1))
+		require.NoError(t, err)
+
+		require.NoError(t, attestedState.SetFinalizedCheckpoint(&pb.Checkpoint{
+			Epoch: config.AltairForkEpoch - 10,
+			Root:  make([]byte, 32),
+		}))
+
+		parent := util.NewBeaconBlockAltair()
+		parent.Block.Slot = slot.Sub(1)
+
+		signedParent, err := blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)
+
+		parentHeader, err := signedParent.Header()
+		require.NoError(t, err)
+		attestedHeader := parentHeader.Header
+
+		err = attestedState.SetLatestBlockHeader(attestedHeader)
+		require.NoError(t, err)
+		attestedStateRoot, err := attestedState.HashTreeRoot(ctx)
+		require.NoError(t, err)
+
+		// get a new signed block so the root is updated with the new state root
+		parent.Block.StateRoot = attestedStateRoot[:]
+		signedParent, err = blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)
+
+		st, err := util.NewBeaconStateAltair()
+		require.NoError(t, err)
+		err = st.SetSlot(slot)
+		require.NoError(t, err)
+
+		parentRoot, err := signedParent.Block().HashTreeRoot()
+		require.NoError(t, err)
+
+		block := util.NewBeaconBlockAltair()
+		block.Block.Slot = slot
+		block.Block.ParentRoot = parentRoot[:]
+
+		for i := uint64(0); i < config.SyncCommitteeSize; i++ {
+			block.Block.Body.SyncAggregate.SyncCommitteeBits.SetBitAt(i, true)
+		}
+
+		signedBlock, err := blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)
+
+		h, err := signedBlock.Header()
+		require.NoError(t, err)
+
+		err = st.SetLatestBlockHeader(h.Header)
+		require.NoError(t, err)
+		stateRoot, err := st.HashTreeRoot(ctx)
+		require.NoError(t, err)
+
+		// get a new signed block so the root is updated with the new state root
+		block.Block.StateRoot = stateRoot[:]
+		signedBlock, err = blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)
+
+		root, err := block.Block.HashTreeRoot()
+		require.NoError(t, err)
+
+		mockBlocker := &testutil.MockBlocker{
+			RootBlockMap: map[[32]byte]interfaces.ReadOnlySignedBeaconBlock{
+				parentRoot: signedParent,
+				root:       signedBlock,
+			},
+			SlotBlockMap: map[primitives.Slot]interfaces.ReadOnlySignedBeaconBlock{
+				slot.Sub(1): signedParent,
+				slot:        signedBlock,
+			},
+		}
+		mockChainService := &mock.ChainService{Optimistic: true, Slot: &slot, State: st, FinalizedRoots: map[[32]byte]bool{
+			root: true,
+		}}
+		mockChainInfoFetcher := &mock.ChainService{Slot: &slot}
+		s := &Server{
+			Stater: &testutil.MockStater{StatesBySlot: map[primitives.Slot]state.BeaconState{
+				slot.Sub(1): attestedState,
+				slot:        st,
+			}},
+			Blocker:          mockBlocker,
+			HeadFetcher:      mockChainService,
+			ChainInfoFetcher: mockChainInfoFetcher,
+		}
+		request := httptest.NewRequest("GET", "http://foo.com", nil)
+		request.Header.Add("Accept", "application/octet-stream")
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+
+		s.GetLightClientFinalityUpdate(writer, request)
+
+		require.Equal(t, http.StatusOK, writer.Code)
+
+		var resp pb.LightClientFinalityUpdateAltair
+		err = resp.UnmarshalSSZ(writer.Body.Bytes())
+		require.NoError(t, err)
+		require.Equal(t, attestedHeader.Slot, resp.AttestedHeader.Beacon.Slot)
+		require.DeepEqual(t, attestedHeader.BodyRoot, resp.AttestedHeader.Beacon.BodyRoot)
+	})
 }

 func TestLightClientHandler_GetLightClientOptimisticUpdate(t *testing.T) {
@@ -1335,6 +1445,114 @@ func TestLightClientHandler_GetLightClientOptimisticUpdate(t *testing.T) {
 		require.NotNil(t, resp.Data)
 	})

+	t.Run("altair SSZ", func(t *testing.T) {
+		ctx := context.Background()
+		slot := primitives.Slot(config.AltairForkEpoch * primitives.Epoch(config.SlotsPerEpoch)).Add(1)
+
+		attestedState, err := util.NewBeaconStateAltair()
+		require.NoError(t, err)
+		err = attestedState.SetSlot(slot.Sub(1))
+		require.NoError(t, err)
+
+		require.NoError(t, attestedState.SetFinalizedCheckpoint(&pb.Checkpoint{
+			Epoch: config.AltairForkEpoch - 10,
+			Root:  make([]byte, 32),
+		}))
+
+		parent := util.NewBeaconBlockAltair()
+		parent.Block.Slot = slot.Sub(1)
+
+		signedParent, err := blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)
+
+		parentHeader, err := signedParent.Header()
+		require.NoError(t, err)
+		attestedHeader := parentHeader.Header
+
+		err = attestedState.SetLatestBlockHeader(attestedHeader)
+		require.NoError(t, err)
+		attestedStateRoot, err := attestedState.HashTreeRoot(ctx)
+		require.NoError(t, err)
+
+		// get a new signed block so the root is updated with the new state root
+		parent.Block.StateRoot = attestedStateRoot[:]
+		signedParent, err = blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)
+
+		st, err := util.NewBeaconStateAltair()
+		require.NoError(t, err)
+		err = st.SetSlot(slot)
+		require.NoError(t, err)
+
+		parentRoot, err := signedParent.Block().HashTreeRoot()
+		require.NoError(t, err)
+
+		block := util.NewBeaconBlockAltair()
+		block.Block.Slot = slot
+		block.Block.ParentRoot = parentRoot[:]
+
+		for i := uint64(0); i < config.SyncCommitteeSize; i++ {
+			block.Block.Body.SyncAggregate.SyncCommitteeBits.SetBitAt(i, true)
+		}
+
+		signedBlock, err := blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)
+
+		h, err := signedBlock.Header()
+		require.NoError(t, err)
+
+		err = st.SetLatestBlockHeader(h.Header)
+		require.NoError(t, err)
+		stateRoot, err := st.HashTreeRoot(ctx)
+		require.NoError(t, err)
+
+		// get a new signed block so the root is updated with the new state root
+		block.Block.StateRoot = stateRoot[:]
+		signedBlock, err = blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)
+
+		root, err := block.Block.HashTreeRoot()
+		require.NoError(t, err)
+
+		mockBlocker := &testutil.MockBlocker{
+			RootBlockMap: map[[32]byte]interfaces.ReadOnlySignedBeaconBlock{
+				parentRoot: signedParent,
+				root:       signedBlock,
+			},
+			SlotBlockMap: map[primitives.Slot]interfaces.ReadOnlySignedBeaconBlock{
+				slot.Sub(1): signedParent,
+				slot:        signedBlock,
+			},
+		}
+		mockChainService := &mock.ChainService{Optimistic: true, Slot: &slot, State: st, FinalizedRoots: map[[32]byte]bool{
+			root: true,
+		}}
+		mockChainInfoFetcher := &mock.ChainService{Slot: &slot}
+		s := &Server{
+			Stater: &testutil.MockStater{StatesBySlot: map[primitives.Slot]state.BeaconState{
+				slot.Sub(1): attestedState,
+				slot:        st,
+			}},
+			Blocker:          mockBlocker,
+			HeadFetcher:      mockChainService,
+			ChainInfoFetcher: mockChainInfoFetcher,
+		}
+		request := httptest.NewRequest("GET", "http://foo.com", nil)
+		request.Header.Add("Accept", "application/octet-stream")
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+
+		s.GetLightClientOptimisticUpdate(writer, request)
+
+		require.Equal(t, http.StatusOK, writer.Code)
+
+		var resp pb.LightClientOptimisticUpdateAltair
+		err = resp.UnmarshalSSZ(writer.Body.Bytes())
+		require.NoError(t, err)
+		require.Equal(t, resp.AttestedHeader.Beacon.Slot, attestedHeader.Slot)
+		require.DeepEqual(t, resp.AttestedHeader.Beacon.BodyRoot, attestedHeader.BodyRoot)
+	})
+
 	t.Run("capella", func(t *testing.T) {
 		ctx := context.Background()
 		slot := primitives.Slot(config.CapellaForkEpoch * primitives.Epoch(config.SlotsPerEpoch)).Add(1)
@@ -1445,6 +1663,114 @@ func TestLightClientHandler_GetLightClientOptimisticUpdate(t *testing.T) {
 		require.NotNil(t, resp.Data)
 	})

+	t.Run("capella SSZ", func(t *testing.T) {
+		ctx := context.Background()
+		slot := primitives.Slot(config.CapellaForkEpoch * primitives.Epoch(config.SlotsPerEpoch)).Add(1)
+
+		attestedState, err := util.NewBeaconStateCapella()
+		require.NoError(t, err)
+		err = attestedState.SetSlot(slot.Sub(1))
+		require.NoError(t, err)
+
+		require.NoError(t, attestedState.SetFinalizedCheckpoint(&pb.Checkpoint{
+			Epoch: config.AltairForkEpoch - 10,
+			Root:  make([]byte, 32),
+		}))
+
+		parent := util.NewBeaconBlockCapella()
+		parent.Block.Slot = slot.Sub(1)
+
+		signedParent, err := blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)
+
+		parentHeader, err := signedParent.Header()
+		require.NoError(t, err)
+		attestedHeader := parentHeader.Header
+
+		err = attestedState.SetLatestBlockHeader(attestedHeader)
+		require.NoError(t, err)
+		attestedStateRoot, err := attestedState.HashTreeRoot(ctx)
+		require.NoError(t, err)
+
+		// get a new signed block so the root is updated with the new state root
+		parent.Block.StateRoot = attestedStateRoot[:]
+		signedParent, err = blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)
+
+		st, err := util.NewBeaconStateCapella()
+		require.NoError(t, err)
+		err = st.SetSlot(slot)
+		require.NoError(t, err)
+
+		parentRoot, err := signedParent.Block().HashTreeRoot()
+		require.NoError(t, err)
+
+		block := util.NewBeaconBlockCapella()
+		block.Block.Slot = slot
+		block.Block.ParentRoot = parentRoot[:]
+
+		for i := uint64(0); i < config.SyncCommitteeSize; i++ {
+			block.Block.Body.SyncAggregate.SyncCommitteeBits.SetBitAt(i, true)
+		}
+
+		signedBlock, err := blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)
+
+		h, err := signedBlock.Header()
+		require.NoError(t, err)
+
+		err = st.SetLatestBlockHeader(h.Header)
+		require.NoError(t, err)
+		stateRoot, err := st.HashTreeRoot(ctx)
+		require.NoError(t, err)
+
+		// get a new signed block so the root is updated with the new state root
+		block.Block.StateRoot = stateRoot[:]
+		signedBlock, err = blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)
+
+		root, err := block.Block.HashTreeRoot()
+		require.NoError(t, err)
+
+		mockBlocker := &testutil.MockBlocker{
+			RootBlockMap: map[[32]byte]interfaces.ReadOnlySignedBeaconBlock{
+				parentRoot: signedParent,
+				root:       signedBlock,
+			},
+			SlotBlockMap: map[primitives.Slot]interfaces.ReadOnlySignedBeaconBlock{
+				slot.Sub(1): signedParent,
+				slot:        signedBlock,
+			},
+		}
+		mockChainService := &mock.ChainService{Optimistic: true, Slot: &slot, State: st, FinalizedRoots: map[[32]byte]bool{
+			root: true,
+		}}
+		mockChainInfoFetcher := &mock.ChainService{Slot: &slot}
+		s := &Server{
+			Stater: &testutil.MockStater{StatesBySlot: map[primitives.Slot]state.BeaconState{
+				slot.Sub(1): attestedState,
+				slot:        st,
+			}},
+			Blocker:          mockBlocker,
+			HeadFetcher:      mockChainService,
+			ChainInfoFetcher: mockChainInfoFetcher,
+		}
+		request := httptest.NewRequest("GET", "http://foo.com", nil)
+		request.Header.Add("Accept", "application/octet-stream")
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+
+		s.GetLightClientOptimisticUpdate(writer, request)
+
+		require.Equal(t, http.StatusOK, writer.Code)
+
+		var resp pb.LightClientOptimisticUpdateCapella
+		err = resp.UnmarshalSSZ(writer.Body.Bytes())
+		require.NoError(t, err)
+		require.Equal(t, resp.AttestedHeader.Beacon.Slot, attestedHeader.Slot)
+		require.DeepEqual(t, resp.AttestedHeader.Beacon.BodyRoot, attestedHeader.BodyRoot)
+	})
+
 	t.Run("deneb", func(t *testing.T) {
 		ctx := context.Background()
 		slot := primitives.Slot(config.DenebForkEpoch * primitives.Epoch(config.SlotsPerEpoch)).Add(1)
@@ -1554,6 +1880,114 @@ func TestLightClientHandler_GetLightClientOptimisticUpdate(t *testing.T) {
 		require.Equal(t, hexutil.Encode(attestedHeader.BodyRoot), respHeader.Beacon.BodyRoot)
 		require.NotNil(t, resp.Data)
 	})
+
+	t.Run("deneb SSZ", func(t *testing.T) {
+		ctx := context.Background()
+		slot := primitives.Slot(config.DenebForkEpoch * primitives.Epoch(config.SlotsPerEpoch)).Add(1)
+
+		attestedState, err := util.NewBeaconStateDeneb()
+		require.NoError(t, err)
+		err = attestedState.SetSlot(slot.Sub(1))
+		require.NoError(t, err)
+
+		require.NoError(t, attestedState.SetFinalizedCheckpoint(&pb.Checkpoint{
+			Epoch: config.AltairForkEpoch - 10,
+			Root:  make([]byte, 32),
+		}))
+
+		parent := util.NewBeaconBlockDeneb()
+		parent.Block.Slot = slot.Sub(1)
+
+		signedParent, err := blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)
+
+		parentHeader, err := signedParent.Header()
+		require.NoError(t, err)
+		attestedHeader := parentHeader.Header
+
+		err = attestedState.SetLatestBlockHeader(attestedHeader)
+		require.NoError(t, err)
+		attestedStateRoot, err := attestedState.HashTreeRoot(ctx)
+		require.NoError(t, err)
+
+		// get a new signed block so the root is updated with the new state root
+		parent.Block.StateRoot = attestedStateRoot[:]
+		signedParent, err = blocks.NewSignedBeaconBlock(parent)
+		require.NoError(t, err)
+
+		st, err := util.NewBeaconStateDeneb()
+		require.NoError(t, err)
+		err = st.SetSlot(slot)
+		require.NoError(t, err)
+
+		parentRoot, err := signedParent.Block().HashTreeRoot()
+		require.NoError(t, err)
+
+		block := util.NewBeaconBlockDeneb()
+		block.Block.Slot = slot
+		block.Block.ParentRoot = parentRoot[:]
+
+		for i := uint64(0); i < config.SyncCommitteeSize; i++ {
+			block.Block.Body.SyncAggregate.SyncCommitteeBits.SetBitAt(i, true)
+		}
+
+		signedBlock, err := blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)
+
+		h, err := signedBlock.Header()
+		require.NoError(t, err)
+
+		err = st.SetLatestBlockHeader(h.Header)
+		require.NoError(t, err)
+		stateRoot, err := st.HashTreeRoot(ctx)
+		require.NoError(t, err)
+
+		// get a new signed block so the root is updated with the new state root
+		block.Block.StateRoot = stateRoot[:]
+		signedBlock, err = blocks.NewSignedBeaconBlock(block)
+		require.NoError(t, err)
+
+		root, err := block.Block.HashTreeRoot()
+		require.NoError(t, err)
+
+		mockBlocker := &testutil.MockBlocker{
+			RootBlockMap: map[[32]byte]interfaces.ReadOnlySignedBeaconBlock{
+				parentRoot: signedParent,
+				root:       signedBlock,
+			},
+			SlotBlockMap: map[primitives.Slot]interfaces.ReadOnlySignedBeaconBlock{
+				slot.Sub(1): signedParent,
+				slot:        signedBlock,
+			},
+		}
+		mockChainService := &mock.ChainService{Optimistic: true, Slot: &slot, State: st, FinalizedRoots: map[[32]byte]bool{
+			root: true,
+		}}
+		mockChainInfoFetcher := &mock.ChainService{Slot: &slot}
+		s := &Server{
+			Stater: &testutil.MockStater{StatesBySlot: map[primitives.Slot]state.BeaconState{
+				slot.Sub(1): attestedState,
+				slot:        st,
+			}},
+			Blocker:          mockBlocker,
+			HeadFetcher:      mockChainService,
+			ChainInfoFetcher: mockChainInfoFetcher,
+		}
+		request := httptest.NewRequest("GET", "http://foo.com", nil)
+		request.Header.Add("Accept", "application/octet-stream")
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+
+		s.GetLightClientOptimisticUpdate(writer, request)
+
+		require.Equal(t, http.StatusOK, writer.Code)
+
+		var resp pb.LightClientOptimisticUpdateDeneb
+		err = resp.UnmarshalSSZ(writer.Body.Bytes())
+		require.NoError(t, err)
+		require.Equal(t, resp.AttestedHeader.Beacon.Slot, attestedHeader.Slot)
+		require.DeepEqual(t, resp.AttestedHeader.Beacon.BodyRoot, attestedHeader.BodyRoot)
+	})
 }

 func TestLightClientHandler_GetLightClientEventBlock(t *testing.T) {
--- a/beacon-chain/rpc/eth/light-client/helpers.go
+++ b/beacon-chain/rpc/eth/light-client/helpers.go
@@ -1,45 +0,0 @@
-package lightclient
-
-import (
-	"context"
-
-	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
-
-	"github.com/prysmaticlabs/prysm/v5/api/server/structs"
-	lightclient "github.com/prysmaticlabs/prysm/v5/beacon-chain/core/light-client"
-	"github.com/prysmaticlabs/prysm/v5/beacon-chain/state"
-	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
-)
-
-func newLightClientFinalityUpdateFromBeaconState(
-	ctx context.Context,
-	currentSlot primitives.Slot,
-	state state.BeaconState,
-	block interfaces.ReadOnlySignedBeaconBlock,
-	attestedState state.BeaconState,
-	attestedBlock interfaces.ReadOnlySignedBeaconBlock,
-	finalizedBlock interfaces.ReadOnlySignedBeaconBlock,
-) (*structs.LightClientFinalityUpdate, error) {
-	result, err := lightclient.NewLightClientFinalityUpdateFromBeaconState(ctx, currentSlot, state, block, attestedState, attestedBlock, finalizedBlock)
-	if err != nil {
-		return nil, err
-	}
-
-	return structs.LightClientFinalityUpdateFromConsensus(result)
-}
-
-func newLightClientOptimisticUpdateFromBeaconState(
-	ctx context.Context,
-	currentSlot primitives.Slot,
-	state state.BeaconState,
-	block interfaces.ReadOnlySignedBeaconBlock,
-	attestedState state.BeaconState,
-	attestedBlock interfaces.ReadOnlySignedBeaconBlock,
-) (*structs.LightClientOptimisticUpdate, error) {
-	result, err := lightclient.NewLightClientOptimisticUpdateFromBeaconState(ctx, currentSlot, state, block, attestedState, attestedBlock)
-	if err != nil {
-		return nil, err
-	}
-
-	return structs.LightClientOptimisticUpdateFromConsensus(result)
-}
--- a/beacon-chain/rpc/eth/validator/BUILD.bazel
+++ b/beacon-chain/rpc/eth/validator/BUILD.bazel
@@ -37,6 +37,7 @@ go_library(
        "//consensus-types/blocks:go_default_library",
        "//consensus-types/primitives:go_default_library",
        "//consensus-types/validator:go_default_library",
+        "//crypto/bls/common:go_default_library",
        "//encoding/bytesutil:go_default_library",
        "//monitoring/tracing/trace:go_default_library",
        "//network/httputil:go_default_library",
--- a/beacon-chain/rpc/eth/validator/handlers.go
+++ b/beacon-chain/rpc/eth/validator/handlers.go
@@ -162,11 +162,7 @@ func (s *Server) aggregatedAttestation(w http.ResponseWriter, slot primitives.Sl
 		return nil
 	}

-	atts, err := s.AttestationsPool.UnaggregatedAttestations()
-	if err != nil {
-		httputil.HandleError(w, "Could not get unaggregated attestations: "+err.Error(), http.StatusInternalServerError)
-		return nil
-	}
+	atts := s.AttestationsPool.UnaggregatedAttestations()
 	match, err = matchingAtts(atts, slot, attDataRoot, index)
 	if err != nil {
 		httputil.HandleError(w, "Could not get matching attestations: "+err.Error(), http.StatusInternalServerError)
@@ -636,6 +632,16 @@ func (s *Server) ProduceSyncCommitteeContribution(w http.ResponseWriter, r *http
 	ctx, span := trace.StartSpan(r.Context(), "validator.ProduceSyncCommitteeContribution")
 	defer span.End()

+	isOptimistic, err := s.OptimisticModeFetcher.IsOptimistic(ctx)
+	if err != nil {
+		httputil.HandleError(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	if isOptimistic {
+		httputil.HandleError(w, "Beacon node is currently syncing and not serving request on that endpoint", http.StatusServiceUnavailable)
+		return
+	}
+
 	_, index, ok := shared.UintFromQuery(w, r, "subcommittee_index", true)
 	if !ok {
 		return
--- a/beacon-chain/rpc/eth/validator/handlers_block.go
+++ b/beacon-chain/rpc/eth/validator/handlers_block.go
@@ -16,6 +16,7 @@ import (
 	fieldparams "github.com/prysmaticlabs/prysm/v5/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/blocks"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
+	"github.com/prysmaticlabs/prysm/v5/crypto/bls/common"
 	"github.com/prysmaticlabs/prysm/v5/encoding/bytesutil"
 	"github.com/prysmaticlabs/prysm/v5/monitoring/tracing/trace"
 	"github.com/prysmaticlabs/prysm/v5/network/httputil"
@@ -57,7 +58,7 @@ func (s *Server) ProduceBlockV2(w http.ResponseWriter, r *http.Request) {

 	var randaoReveal []byte
 	if rawSkipRandaoVerification == "true" {
-		randaoReveal = primitives.PointAtInfinity
+		randaoReveal = common.InfiniteSignature[:]
 	} else {
 		rr, err := bytesutil.DecodeHexWithLength(rawRandaoReveal, fieldparams.BLSSignatureLength)
 		if err != nil {
@@ -109,7 +110,7 @@ func (s *Server) ProduceBlindedBlock(w http.ResponseWriter, r *http.Request) {

 	var randaoReveal []byte
 	if rawSkipRandaoVerification == "true" {
-		randaoReveal = primitives.PointAtInfinity
+		randaoReveal = common.InfiniteSignature[:]
 	} else {
 		rr, err := bytesutil.DecodeHexWithLength(rawRandaoReveal, fieldparams.BLSSignatureLength)
 		if err != nil {
@@ -174,7 +175,7 @@ func (s *Server) ProduceBlockV3(w http.ResponseWriter, r *http.Request) {

 	var randaoReveal []byte
 	if rawSkipRandaoVerification == "true" {
-		randaoReveal = primitives.PointAtInfinity
+		randaoReveal = common.InfiniteSignature[:]
 	} else {
 		rr, err := bytesutil.DecodeHexWithLength(rawRandaoReveal, fieldparams.BLSSignatureLength)
 		if err != nil {
--- a/beacon-chain/rpc/eth/validator/handlers_test.go
+++ b/beacon-chain/rpc/eth/validator/handlers_test.go
@@ -118,8 +118,7 @@ func TestGetAggregateAttestation(t *testing.T) {

 		pool := attestations.NewPool()
 		require.NoError(t, pool.SaveUnaggregatedAttestations([]ethpbalpha.Att{unaggSlot3_Root1_1, unaggSlot3_Root1_2, unaggSlot3_Root2, unaggSlot4}), "Failed to save unaggregated attestations")
-		unagg, err := pool.UnaggregatedAttestations()
-		require.NoError(t, err)
+		unagg := pool.UnaggregatedAttestations()
 		require.Equal(t, 4, len(unagg), "Expected 4 unaggregated attestations")
 		require.NoError(t, pool.SaveAggregatedAttestations([]ethpbalpha.Att{aggSlot1_Root1_1, aggSlot1_Root1_2, aggSlot1_Root2, aggSlot2}), "Failed to save aggregated attestations")
 		agg := pool.AggregatedAttestations()
@@ -268,8 +267,7 @@ func TestGetAggregateAttestation(t *testing.T) {

 			pool := attestations.NewPool()
 			require.NoError(t, pool.SaveUnaggregatedAttestations([]ethpbalpha.Att{unaggSlot3_Root1_1, unaggSlot3_Root1_2, unaggSlot3_Root2, unaggSlot4}), "Failed to save unaggregated attestations")
-			unagg, err := pool.UnaggregatedAttestations()
-			require.NoError(t, err)
+			unagg := pool.UnaggregatedAttestations()
 			require.Equal(t, 4, len(unagg), "Expected 4 unaggregated attestations")
 			require.NoError(t, pool.SaveAggregatedAttestations([]ethpbalpha.Att{aggSlot1_Root1_1, aggSlot1_Root1_2, aggSlot1_Root2, aggSlot2, postElectraAtt}), "Failed to save aggregated attestations")
 			agg := pool.AggregatedAttestations()
@@ -373,8 +371,7 @@ func TestGetAggregateAttestation(t *testing.T) {

 			pool := attestations.NewPool()
 			require.NoError(t, pool.SaveUnaggregatedAttestations([]ethpbalpha.Att{unaggSlot3_Root1_1, unaggSlot3_Root1_2, unaggSlot3_Root2, unaggSlot4}), "Failed to save unaggregated attestations")
-			unagg, err := pool.UnaggregatedAttestations()
-			require.NoError(t, err)
+			unagg := pool.UnaggregatedAttestations()
 			require.Equal(t, 4, len(unagg), "Expected 4 unaggregated attestations")
 			require.NoError(t, pool.SaveAggregatedAttestations([]ethpbalpha.Att{aggSlot1_Root1_1, aggSlot1_Root1_2, aggSlot1_Root2, aggSlot2, preElectraAtt}), "Failed to save aggregated attestations")
 			agg := pool.AggregatedAttestations()
@@ -1584,7 +1581,8 @@ func TestProduceSyncCommitteeContribution(t *testing.T) {
 				SyncCommitteeIndices: []primitives.CommitteeIndex{0},
 			},
 		},
-		SyncCommitteePool: syncCommitteePool,
+		SyncCommitteePool:     syncCommitteePool,
+		OptimisticModeFetcher: &mockChain.ChainService{},
 	}
 	t.Run("ok", func(t *testing.T) {
 		url := "http://example.com?slot=1&subcommittee_index=1&beacon_block_root=0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"
@@ -1672,7 +1670,8 @@ func TestProduceSyncCommitteeContribution(t *testing.T) {
 					SyncCommitteeIndices: []primitives.CommitteeIndex{0},
 				},
 			},
-			SyncCommitteePool: syncCommitteePool,
+			SyncCommitteePool:     syncCommitteePool,
+			OptimisticModeFetcher: &mockChain.ChainService{},
 		}
 		server.ProduceSyncCommitteeContribution(writer, request)
 		assert.Equal(t, http.StatusNotFound, writer.Code)
@@ -1680,6 +1679,26 @@ func TestProduceSyncCommitteeContribution(t *testing.T) {
 		require.NoError(t, json.Unmarshal(writer.Body.Bytes(), resp2))
 		require.ErrorContains(t, "No subcommittee messages found", errors.New(writer.Body.String()))
 	})
+	t.Run("Optimistic returns 503", func(t *testing.T) {
+		url := "http://example.com?slot=1&subcommittee_index=1&beacon_block_root=0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"
+		request := httptest.NewRequest(http.MethodGet, url, nil)
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+		syncCommitteePool = synccommittee.NewStore()
+		server = Server{
+			CoreService: &core.Service{
+				HeadFetcher: &mockChain.ChainService{
+					SyncCommitteeIndices: []primitives.CommitteeIndex{0},
+				},
+			},
+			SyncCommitteePool: syncCommitteePool,
+			OptimisticModeFetcher: &mockChain.ChainService{
+				Optimistic: true,
+			},
+		}
+		server.ProduceSyncCommitteeContribution(writer, request)
+		assert.Equal(t, http.StatusServiceUnavailable, writer.Code)
+	})
 }

 func TestServer_RegisterValidator(t *testing.T) {
--- a/beacon-chain/rpc/prysm/v1alpha1/validator/BUILD.bazel
+++ b/beacon-chain/rpc/prysm/v1alpha1/validator/BUILD.bazel
@@ -73,6 +73,7 @@ go_library(
        "//container/trie:go_default_library",
        "//contracts/deposit:go_default_library",
        "//crypto/bls:go_default_library",
+        "//crypto/bls/common:go_default_library",
        "//crypto/hash:go_default_library",
        "//crypto/rand:go_default_library",
        "//encoding/bytesutil:go_default_library",
--- a/beacon-chain/rpc/prysm/v1alpha1/validator/proposer_altair.go
+++ b/beacon-chain/rpc/prysm/v1alpha1/validator/proposer_altair.go
@@ -8,6 +8,7 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
 	"github.com/prysmaticlabs/prysm/v5/crypto/bls"
+	"github.com/prysmaticlabs/prysm/v5/crypto/bls/common"
 	"github.com/prysmaticlabs/prysm/v5/encoding/bytesutil"
 	"github.com/prysmaticlabs/prysm/v5/monitoring/tracing/trace"
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
@@ -96,7 +97,7 @@ func (vs *Server) getSyncAggregate(ctx context.Context, slot primitives.Slot, ro
 	syncSig := bls.AggregateSignatures(sigsHolder)
 	var syncSigBytes [96]byte
 	if syncSig == nil {
-		syncSigBytes = [96]byte{0xC0} // Infinity signature if itself is nil.
+		syncSigBytes = common.InfiniteSignature // Infinity signature if itself is nil.
 	} else {
 		syncSigBytes = bytesutil.ToBytes96(syncSig.Marshal())
 	}
--- a/beacon-chain/rpc/prysm/v1alpha1/validator/proposer_attestations.go
+++ b/beacon-chain/rpc/prysm/v1alpha1/validator/proposer_attestations.go
@@ -40,10 +40,7 @@ func (vs *Server) packAttestations(ctx context.Context, latestState state.Beacon
 		atts = vs.AttPool.AggregatedAttestations()
 		atts = vs.validateAndDeleteAttsInPool(ctx, latestState, atts)

-		uAtts, err := vs.AttPool.UnaggregatedAttestations()
-		if err != nil {
-			return nil, errors.Wrap(err, "could not get unaggregated attestations")
-		}
+		uAtts := vs.AttPool.UnaggregatedAttestations()
 		uAtts = vs.validateAndDeleteAttsInPool(ctx, latestState, uAtts)
 		atts = append(atts, uAtts...)
 	}
--- a/beacon-chain/rpc/prysm/v1alpha1/validator/proposer_test.go
+++ b/beacon-chain/rpc/prysm/v1alpha1/validator/proposer_test.go
@@ -2949,8 +2949,7 @@ func TestProposer_DeleteAttsInPool_Aggregated(t *testing.T) {
 	require.NoError(t, err)
 	require.NoError(t, s.deleteAttsInPool(context.Background(), append(aa, unaggregatedAtts...)))
 	assert.Equal(t, 0, len(s.AttPool.AggregatedAttestations()), "Did not delete aggregated attestation")
-	atts, err := s.AttPool.UnaggregatedAttestations()
-	require.NoError(t, err)
+	atts := s.AttPool.UnaggregatedAttestations()
 	assert.Equal(t, 0, len(atts), "Did not delete unaggregated attestation")
 }

--- a/beacon-chain/rpc/testutil/mock_blocker.go
+++ b/beacon-chain/rpc/testutil/mock_blocker.go
@@ -37,5 +37,5 @@ func (m *MockBlocker) Block(_ context.Context, b []byte) (interfaces.ReadOnlySig

 // Blobs --
 func (m *MockBlocker) Blobs(_ context.Context, _ string, _ []uint64) ([]*blocks.VerifiedROBlob, *core.RpcError) {
-	panic("implement me")
+	panic("implement me") // lint:nopanic -- Test code.
 }
--- a/beacon-chain/state/stategen/epoch_boundary_state_cache.go
+++ b/beacon-chain/state/stategen/epoch_boundary_state_cache.go
@@ -178,7 +178,7 @@ func (e *epochBoundaryState) delete(blockRoot [32]byte) error {
 func trim(queue *cache.FIFO, maxSize uint64) {
 	for s := uint64(len(queue.ListKeys())); s > maxSize; s-- {
 		if _, err := queue.Pop(popProcessNoopFunc); err != nil { // This never returns an error, but we'll handle anyway for sanity.
-			panic(err)
+			panic(err) // lint:nopanic -- Never returns an error.
 		}
 	}
 }
--- a/beacon-chain/state/stategen/mock/mock.go
+++ b/beacon-chain/state/stategen/mock/mock.go
@@ -1,3 +1,4 @@
+// lint:nopanic -- Mock code, OK to panic.
 package mock

 import (
--- a/beacon-chain/state/stategen/service.go
+++ b/beacon-chain/state/stategen/service.go
@@ -121,9 +121,10 @@ func (s *State) Resume(ctx context.Context, fState state.BeaconState) (state.Bea
 		return nil, err
 	}
 	fRoot := bytesutil.ToBytes32(c.Root)
+	st := fState
 	// Resume as genesis state if last finalized root is zero hashes.
 	if fRoot == params.BeaconConfig().ZeroHash {
-		st, err := s.beaconDB.GenesisState(ctx)
+		st, err = s.beaconDB.GenesisState(ctx)
 		if err != nil {
 			return nil, errors.Wrap(err, "could not get genesis state")
 		}
@@ -132,10 +133,13 @@ func (s *State) Resume(ctx context.Context, fState state.BeaconState) (state.Bea
 		if err != nil {
 			return nil, stderrors.Join(ErrNoGenesisBlock, err)
 		}
-		return st, s.SaveState(ctx, gbr, st)
+		fRoot = gbr
+		if err := s.SaveState(ctx, gbr, st); err != nil {
+			return nil, errors.Wrap(err, "could not save genesis state")
+		}
 	}

-	if fState == nil || fState.IsNil() {
+	if st == nil || st.IsNil() {
 		return nil, errors.New("finalized state is nil")
 	}

@@ -145,20 +149,22 @@ func (s *State) Resume(ctx context.Context, fState state.BeaconState) (state.Bea
 		}
 	}()

-	s.finalizedInfo = &finalizedInfo{slot: fState.Slot(), root: fRoot, state: fState.Copy()}
-	fEpoch := slots.ToEpoch(fState.Slot())
+	s.finalizedInfo = &finalizedInfo{slot: st.Slot(), root: fRoot, state: st.Copy()}
+	populatePubkeyCache(ctx, st)
+	return st, nil
+}

-	// Pre-populate the pubkey cache with the validator public keys from the finalized state.
-	// This process takes about 30 seconds on mainnet with 450,000 validators.
+func populatePubkeyCache(ctx context.Context, st state.BeaconState) {
+	epoch := slots.ToEpoch(st.Slot())
 	go populatePubkeyCacheOnce.Do(func() {
 		log.Debug("Populating pubkey cache")
 		start := time.Now()
-		if err := fState.ReadFromEveryValidator(func(_ int, val state.ReadOnlyValidator) error {
+		if err := st.ReadFromEveryValidator(func(_ int, val state.ReadOnlyValidator) error {
 			if ctx.Err() != nil {
 				return ctx.Err()
 			}
 			// Do not cache for non-active validators.
-			if !helpers.IsActiveValidatorUsingTrie(val, fEpoch) {
+			if !helpers.IsActiveValidatorUsingTrie(val, epoch) {
 				return nil
 			}
 			pub := val.PublicKey()
@@ -169,8 +175,6 @@ func (s *State) Resume(ctx context.Context, fState state.BeaconState) (state.Bea
 		}
 		log.WithField("duration", time.Since(start)).Debug("Done populating pubkey cache")
 	})
-
-	return fState, nil
 }

 // SaveFinalizedState saves the finalized slot, root and state into memory to be used by state gen service.
--- a/Show More
+++ b/Show More
Author	SHA1	Message	Date
Potuz	feca3ac1ef	Merge branch 'develop' into dont_fcu_to_nil	2025-03-20 14:14:56 -03:00
Manu NALEPA	d2699761ed	`subscribeToSubnets`: Remove unused parameter. (#15079 ) * `subscribeToSubnets`: Remove unused parameter. * Changelog: Change `Fixed` to `Ignored`.	2025-03-20 15:57:55 +00:00
Manu NALEPA	c73473b59d	Tracked validator cache: Make sure no to loose the reference. (#15077 )	2025-03-20 10:00:40 +00:00
Preston Van Loon	2aa52fb56a	Add static analyzer to discourage use of panic() (#15075 ) * Implement static analysis to prevent panics * Add nopanic to nogo * Fix violations and add exclusions Fix violations and add exclusions for all * Changelog fragment * Use pass.Report instead of pass.Reportf * Remove strings.ToLower for checking init method name * Add exclusion for herumi init * Move api/client/beacon template function to init and its own file * Fix nopanic testcase	2025-03-19 18:04:15 +00:00
Preston Van Loon	16d5abd21b	Update changelog for v5.3.1 release (#15045 ) * Update changelog for v5.3.1 release. * Add description for v5.3.1 * Changelog fragment	2025-03-19 15:10:30 +00:00
james-prysm	08bfaca42d	panic to error changes and changelog (#15074 )	2025-03-19 14:31:29 +00:00
Sam Calder-Mason	179cedd4a0	feat(event-stream): Support block_gossip topic (#15038 ) * feat(event-stream): Add block_gossip topic support * feat(event-stream): Add block_gossip topic support * feat(event-stream): Add block_gossip topic support * feat: add block gossip topic support to beacon api event stream * fix: sync_fuzz_test panic * fix: check for nil operationNotifier before sending block gossip The operationNotifier was not being checked for nil before being used, which could lead to a panic if it was not initialized. This commit adds a nil check to prevent the panic. --------- Co-authored-by: james-prysm <90280386+james-prysm@users.noreply.github.com>	2025-03-18 19:27:27 +00:00
terence	0f39857653	Clean up infinity signature usages (#15072 )	2025-03-18 19:27:06 +00:00
terence	645328bb9e	Clarify infinity signature deposit tests (#15071 )	2025-03-18 19:25:56 +00:00
james-prysm	9d2273c514	Move prysm specific performance endpoint (#15062 ) * adding in check for non prysm node and moving the prysm endpoint to the prysm beacon client * fixing a bug connecting to a non prysm client and moving the prysm api call to the prysm beacon client * changelog * fixing linting * Update validator/client/metrics.go Co-authored-by: Radosław Kapka <rkapka@wp.pl> --------- Co-authored-by: Radosław Kapka <rkapka@wp.pl>	2025-03-18 15:02:54 +00:00
Radosław Kapka	34429368fe	Update seen unaggregated att cache to Electra (#15034 ) * Update seen unaggregated att cache to Electra * changelog <3 * pass full att * revert extracting length check * check if 1 bit set * test fix * adding end to end unit test saving unaggregated electra att and then verifying that it's already seen in the cache * Terence's feedback * return false on errors --------- Co-authored-by: james-prysm <james@prysmaticlabs.com>	2025-03-17 16:34:34 +00:00
Nishant Das	629568c796	Handle Networking Message Limits Better (#14799 ) * Handle Message Limits * Changelog * Ignore them for now * Sort fields * Update to Latest Versions	2025-03-17 14:15:20 +00:00
terence	5c24978702	Add hoodi testnet flag (#15057 ) * Add hoodi testnet flag * Add upstream test * Fix test	2025-03-17 05:49:27 +00:00
kasey	4e44999207	OCL forked changed-files pin; pin others (#15056 ) * OCL forked changed-files pin; pin others * changelog :) --------- Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>	2025-03-15 19:56:25 +00:00
james-prysm	15ae71c0da	Builder ssz (#14976 ) * wip * refactoring functions for easier readability * allow ssz for register validator * changelog * adding in blinded block submission tests * adding in tests for header ssz * fixing linting and tests * adding in custom errors and fixing ssz validator registration * Update api/client/builder/client.go Co-authored-by: Manu NALEPA <enalepa@offchainlabs.com> * Update api/client/builder/client.go Co-authored-by: Manu NALEPA <enalepa@offchainlabs.com> * manu's feedback * linting * adding in info log to notify that this setting was turned on * fixing linting * manu's feedback * fixing import --------- Co-authored-by: Manu NALEPA <enalepa@offchainlabs.com>	2025-03-14 17:23:00 +00:00
terence	1caea86152	Update spec test to v1.5.0-beta.3 (#15050 )	2025-03-14 10:47:16 +00:00
james-prysm	7cef3b0491	adding omitempty to request object (#15031 )	2025-03-11 13:43:00 +00:00
Radosław Kapka	15462844f9	Remove error from signatures of `UnaggregatedAttestations` and `pruneAttsFromPool` (#15028 )	2025-03-10 22:28:51 +00:00
Potuz	863eee7b40	Add feature flag to start from any beacon block in db (#15000 ) * Add feature flag to start from any beacon block in db The new feature flag called --sync-from takes a string that can take values: - `head` or - a 0x-prefixed hex encoded beacon block root. The beacon block root or the head block root has to be known in db and has to be a descendant of the current justified checkpoint. * Fix Bugs In Sync From Head (#15006) * Fix Bugs * Remove log * missing save * add tests * Kasey review #1 * Kasey's review #2 * Kasey's review #3 --------- Co-authored-by: Nishant Das <nishdas93@gmail.com>	2025-03-10 15:51:25 +00:00
Radosław Kapka	6d89373583	Handle unaggregated attestations when decomposing (#15027 )	2025-03-10 13:48:43 +00:00
kasey	9a421a2feb	payload attribute computations in event handler (#14963 ) * payload attribute computations in event handler * Skip executing nil lazyReaders * adding in clarifying comments, uncommenting needs fill, adding in happy path unit test for code coverage * gaz * fixing ineffectual assignment * nil check the Reader coming from the lazyReader * Apply suggestions from code review Radek's PR suggestion to fix error/log capitalization. Co-authored-by: Radosław Kapka <rkapka@wp.pl> * Radek feedback * Move fire payload attribute event to after save head * set mock statenotifier in testServiceOptsWithDB --------- Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com> Co-authored-by: james-prysm <james@prysmaticlabs.com> Co-authored-by: Radosław Kapka <rkapka@wp.pl> Co-authored-by: terence tsao <terence@prysmaticlabs.com>	2025-03-07 23:25:12 +00:00
james-prysm	4e41d5c610	fixing e2e builder gas limit (#15025 ) * fixing e2e * linting	2025-03-07 19:00:16 +00:00
james-prysm	0b6bea43a8	adding optimistic check to /eth/v1/validator/sync_committee_contribution rest endpoint (#15022 )	2025-03-06 22:29:11 +00:00
Radosław Kapka	f89afb0fbd	Handle some errors from `hasSeenBit` and `insertSeenBit` differently (#15018 ) * Ignore errors from `hasSeenBit` and don't pack unaggregated attestations * changelog <3 * Revert "Ignore errors from `hasSeenBit` and don't pack unaggregated attestations" This reverts commit dc86cb63204d6ff735d9302142068de95a8188fd.	2025-03-06 22:26:20 +00:00
Potuz	3cd2973c92	Return the genesis block root from last validated checkpoint if zero (#15021 ) * Return the genesis block root from last validated checkpoint if zero When starting a node we load the last validated checkpoint. On tests or a new node this checkpoint can have the zero blockroot (it returns the finalized checkpoint). This PR ensures that it returns the genesis block root instead. It can't affect runnning code since the root is only used at startup in `setup_forkchoice`. But it may affect tests because now `OptimisticForRoot` will error out if there is no genesis block root set on db. * Terence review * fix test	2025-03-06 21:42:11 +00:00
james-prysm	d3e5710a63	updated gas limit (#14858 )	2025-03-06 16:37:14 +00:00
Preston Van Loon	f40b4f16c2	Beacon API: Broadcasting BLS to execution changes should not use the request context in a go routine (#15019 ) * Broadcasting BLS to execution changes should not use the request context in a go routine * Changelog fragment	2025-03-06 15:25:48 +00:00
kasey	7fd4f746d6	Clean up block-slot-indices on block deletion (#15011 ) * clean up block-slot-indices on block deletion * also remove parent root index entry * treat parent root index as packed key (like slot idx) * fix bug where input slice is modified, with test --------- Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>	2025-03-06 14:43:23 +00:00
james-prysm	2362d9f3c2	blob_sidecar_subnet configs missing from `/eth/v1/config/spec` endpoint (#15016 ) * fixing config display * fixing test	2025-03-06 14:25:53 +00:00
Jun Song	6b84f8c6b1	Add p2p address format for CLI users (#14886 ) * Add address format for CLI users * Add changelog	2025-03-05 18:21:22 +00:00
terence	997a9112d1	Validate blob sidecar: check bad parent first (#15013 )	2025-03-05 17:54:44 +00:00
Preston Van Loon	d46ca97680	Update go to 1.24.0 (#14969 ) * Update rules_go to v0.53.0 * Update staticcheck to v0.6.0 * Update to go 1.24.0 * Update github.com/trailofbits/go-mutexasserts to latest * Use rules_go @ cf3c3af34bd869b864f5f2b98e2f41c2b220d6c9 * Provide the go binary to SszGen. https://github.com/bazel-contrib/rules_go/pull/4173 * Unskip SA9003 * Update github ci checks to go1.24.0 * CI: Update gosec to v2.22.1 and golangci to v1..64.5 * Temporarily disable usetesting lint check for go1.24 * gosec: Disable G115 - integer overflow conversion * gosec: Ignore G407 for "hardcoded" IV. It's not hardcoded. * Fix uses of rand.Seed. This is a no-op in go1.24 and deprecated since go1.20. * Changelog fragment	2025-03-05 17:46:39 +00:00
Radosław Kapka	417bbf8a9e	Decompose Electra block attestations (#14896 ) * Decompose Electra block attestations * comments * changelog <3 * remove redundant comparison * typo in comment * fix changelog section name * review from James and Sammy * continue pruning on error * only prune when committees are cached * fix bad assignments in test	2025-03-05 10:01:33 +00:00
Potuz	a7b016c954	Add Target root to forkchoice dump (#15009 ) * Add Target root to forkchoice dump * review	2025-03-05 04:49:44 +00:00
Manu NALEPA	6015493de9	`--validators-registration-batch-size`: Change default value from `0` to `200`. (#14981 )	2025-03-04 16:32:24 +00:00
Dhruv Bodani	c718bdbe2b	fix pruner timing issue with batch pruning (#14929 ) * fix pruner timing issue with batch pruning * add changelog entry * add batchSize and number of slots deleted to debug logs * fix lint * prune in small batches in one prune cycle * remove noisy logs * fix number of batches to prune and return early if there's nothing to delete * use context with timeout * fix lint by ignoring nil err return	2025-03-04 16:31:17 +00:00
Preston Van Loon	0a8f947169	beacon-chain: Reorganize flags in help text (#14959 ) * Beacon flags: Comment on deprecated section * Beacon flags: Organize flags relevant to logging, comment on logging section * Beacon flags: Organize flags relevant to p2p, comment on p2p section * Beacon flags: Introduce db flag section, organize flags relevant to db, comment on db section * Beacon flags: Introduce builder flag section, organize flags relevant to builder, comment on builder section * Beacon flags: Introduce sync flag section, organize flags relevant to sync, comment on sync section * Beacon flags: Introduce execution layer flag section, organize flags relevant to execution layer, comment on execution layer section * Beacon flags: Introduce monitoring flag section, organize flags relevant to monitoring, comment on monitoring section * Beacon flags: Organizing remaining flags in cmd and beacon-chain sections * Beacon flags: Introduce slasher flag section, organize flags relevant to slasher, comment on slasher section * Move slasher flag from features to the slasher section * Changelog fragment * Beacon flags: Reorganize sections * Move MaxGoroutines to debug section	2025-03-04 16:17:29 +00:00
james-prysm	d7efccf6a5	single attestation cleanup (#14984 ) * some cleanup and minor bug fix * adding some comments back in * Update beacon-chain/sync/pending_attestations_queue.go Co-authored-by: Radosław Kapka <rkapka@wp.pl> * Update beacon-chain/sync/pending_attestations_queue.go Co-authored-by: Radosław Kapka <rkapka@wp.pl> * Update beacon-chain/sync/validate_beacon_attestation.go Co-authored-by: Radosław Kapka <rkapka@wp.pl> * Update beacon-chain/sync/validate_beacon_attestation.go Co-authored-by: Radosław Kapka <rkapka@wp.pl> * Update beacon-chain/sync/validate_beacon_attestation.go Co-authored-by: Radosław Kapka <rkapka@wp.pl> * Update beacon-chain/sync/validate_beacon_attestation.go Co-authored-by: Radosław Kapka <rkapka@wp.pl> * Update beacon-chain/sync/validate_beacon_attestation.go Co-authored-by: Radosław Kapka <rkapka@wp.pl> * Update beacon-chain/sync/pending_attestations_queue.go Co-authored-by: Radosław Kapka <rkapka@wp.pl> * adding comment back in * linting * fixing committeeIndiciesSLot * fixing changelog --------- Co-authored-by: Radosław Kapka <rkapka@wp.pl>	2025-03-04 14:50:59 +00:00
Nishant Das	334920bc9e	Fix Block Decoding During State Deletion (#15008 ) * Fix Block Decoding * Changelog	2025-03-04 11:55:32 +00:00
james-prysm	6e00db433c	cache uses wrong seen committee index for electra (#14998 ) * adding fix and unit tests * removing unneeded test for now, will handle in separate PR	2025-03-03 16:53:42 +00:00
james-prysm	c6344e7c3e	fixing electra committee logs (#14992 ) * fixing logs * fixing tests * addressing feedback * fixing tests based on feedback	2025-03-03 15:35:45 +00:00
Potuz	2131254722	Populate pubkey cache at genesis (#14995 ) When starting with a zero root finalized checkpoint instead of returning early also populate the pubkey cache.	2025-02-28 11:12:52 +00:00
Potuz	b6d1866deb	Split out forkchoice setup from service start (#14997 )	2025-02-27 20:38:29 +00:00
james-prysm	e56f489d06	add log for committee index on electra attesation (#14993 ) * adding log in the case of debugging * gaz	2025-02-27 18:11:27 +00:00
Nishant Das	bf62afb27c	Fix Gossip Validation of Electra Attester Slashings (#14985 ) * Fix Attester Slashing Validation In Electra * Changelog	2025-02-27 08:50:24 +00:00
Bastin	8369056027	SSZ Support for LC finality and optimistic update APIs (#14836 ) * bundle handlers test * ssz support for optimistic and finality updates APIs * changelog PR link * delete helpers --------- Co-authored-by: Radosław Kapka <rkapka@wp.pl>	2025-02-25 13:09:28 +00:00
Preston Van Loon	09499a732f	gosec: Fix violations of G301 (#14980 ) * gosec: Fix violations of G301 * Changelog fragment	2025-02-24 15:13:53 +00:00
Preston Van Loon	2ee015452c	Use go-cmp and protocmp for assertion diff printing (#14978 ) Fix assertion tests after switching to cmp Changelog fragment	2025-02-23 21:06:07 +00:00
Potuz	35559253f5	Do not send zero hash on FCU	2025-02-18 09:52:16 -03:00