fix stategen fallback when hdiff root lookup misses

beacon-chain/db/kv/error.go

@@ -26,6 +26,15 @@ var ErrNotFoundMetadataSeqNum = errors.Wrap(ErrNotFound, "metadata sequence numb
 // but the database was created without state-diff support.
 var ErrStateDiffIncompatible = errors.New("state-diff feature enabled but database was created without state-diff support")
 
+// ErrStateDiffCorrupted is returned when state-diff metadata or data is missing or invalid.
+var ErrStateDiffCorrupted = errors.New("state-diff database corrupted")
+
+// ErrStateDiffExponentMismatch is returned when configured exponents differ from stored metadata.
+var ErrStateDiffExponentMismatch = errors.New("state-diff exponents mismatch")
+
+// ErrStateDiffMissingSnapshot is returned when the offset snapshot is missing.
+var ErrStateDiffMissingSnapshot = errors.New("state-diff offset snapshot missing")
+
 var errEmptyBlockSlice = errors.New("[]blocks.ROBlock is empty")
 var errIncorrectBlockParent = errors.New("unexpected missing or forked blocks in a []ROBlock")
 var errFinalizedChildNotFound = errors.New("unable to find finalized root descending from backfill batch")

beacon-chain/db/kv/kv.go

@@ -7,9 +7,11 @@ import (
 	"fmt"
 	"os"
 	"path"
+	"slices"
 	"time"
 
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/db/iface"
+	"github.com/OffchainLabs/prysm/v7/cmd/beacon-chain/flags"
 	"github.com/OffchainLabs/prysm/v7/config/features"
 	"github.com/OffchainLabs/prysm/v7/config/params"
 	"github.com/OffchainLabs/prysm/v7/consensus-types/blocks"
@@ -21,6 +23,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	prombolt "github.com/prysmaticlabs/prombbolt"
+	logrus "github.com/sirupsen/logrus"
 	bolt "go.etcd.io/bbolt"
 )
 
@@ -223,8 +226,42 @@ func (kv *Store) startStateDiff(ctx context.Context) error {
 	}
 
 	if hasOffset {
-		// Existing state-diff database - restarts not yet supported.
-		return errors.New("restarting with existing state-diff database not yet supported")
+		storedExponents, err := kv.loadStateDiffExponents()
+		if err != nil {
+			return fmt.Errorf("%w: state-diff metadata missing or invalid; re-sync required: %v", ErrStateDiffCorrupted, err)
+		}
+		currentExponents := flags.Get().StateDiffExponents
+		if !slices.Equal(storedExponents, currentExponents) {
+			return errors.Wrapf(
+				ErrStateDiffExponentMismatch,
+				"state-diff exponents changed; database incompatible. "+
+					"Database was initialized with: %v. "+
+					"Current configuration: %v. "+
+					"Options: use original exponents (--state-diff-exponents=%s) or delete database and re-sync from genesis/checkpoint.",
+				storedExponents,
+				currentExponents,
+				formatStateDiffExponents(storedExponents),
+			)
+		}
+		offset, err := kv.loadOffset()
+		if err != nil {
+			return err
+		}
+		cache, err := populateStateDiffCacheFromDB(kv, offset)
+		if err != nil {
+			return err
+		}
+		kv.stateDiffCache = cache
+		if flags.Get().StateDiffValidateOnStartup {
+			if err := validateStateDiffCache(ctx, kv, cache); err != nil {
+				return err
+			}
+		}
+		log.WithFields(logrus.Fields{
+			"offset":    offset,
+			"exponents": storedExponents,
+		}).Info("State-diff cache initialized from existing database")
+		return nil
 	}
 
 	// Check if this is a new database (no head block).

beacon-chain/db/kv/kv_test.go

@@ -3,12 +3,15 @@ package kv
 import (
 	"bytes"
 	"context"
+	"encoding/binary"
 	"fmt"
 	"testing"
 
+	"github.com/OffchainLabs/prysm/v7/cmd/beacon-chain/flags"
 	"github.com/OffchainLabs/prysm/v7/config/features"
 	"github.com/OffchainLabs/prysm/v7/consensus-types/blocks"
 	ethpb "github.com/OffchainLabs/prysm/v7/proto/prysm/v1alpha1"
+	"github.com/OffchainLabs/prysm/v7/runtime/version"
 	"github.com/OffchainLabs/prysm/v7/testing/require"
 	"github.com/OffchainLabs/prysm/v7/testing/util"
 	bolt "go.etcd.io/bbolt"
@@ -27,6 +30,108 @@ func setupDB(t testing.TB) *Store {
 	return db
 }
 
+func TestStartStateDiff_ExponentMismatch(t *testing.T) {
+	resetCfg := features.InitWithReset(&features.Flags{EnableStateDiff: true})
+	defer resetCfg()
+	setDefaultStateDiffExponents()
+
+	store := setupDB(t)
+	require.NoError(t, store.db.Update(func(tx *bolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bolt.ErrBucketNotFound
+		}
+		offsetBytes := make([]byte, 8)
+		binary.LittleEndian.PutUint64(offsetBytes, 0)
+		if err := bucket.Put(offsetKey, offsetBytes); err != nil {
+			return err
+		}
+		encoded, err := encodeStateDiffExponents([]int{20, 10})
+		if err != nil {
+			return err
+		}
+		return bucket.Put(exponentsKey, encoded)
+	}))
+
+	ctx := t.Context()
+	err := store.startStateDiff(ctx)
+	require.ErrorContains(t, "state-diff exponents changed", err)
+}
+
+func TestStartStateDiff_MissingOffsetSnapshot(t *testing.T) {
+	resetCfg := features.InitWithReset(&features.Flags{EnableStateDiff: true})
+	defer resetCfg()
+	setDefaultStateDiffExponents()
+
+	store := setupDB(t)
+	require.NoError(t, store.db.Update(func(tx *bolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bolt.ErrBucketNotFound
+		}
+		offsetBytes := make([]byte, 8)
+		binary.LittleEndian.PutUint64(offsetBytes, 0)
+		if err := bucket.Put(offsetKey, offsetBytes); err != nil {
+			return err
+		}
+		encoded, err := encodeStateDiffExponents(flags.Get().StateDiffExponents)
+		if err != nil {
+			return err
+		}
+		return bucket.Put(exponentsKey, encoded)
+	}))
+
+	ctx := t.Context()
+	err := store.startStateDiff(ctx)
+	require.ErrorContains(t, "missing offset snapshot", err)
+}
+
+func TestStartStateDiff_ValidateOnStartup(t *testing.T) {
+	resetCfg := features.InitWithReset(&features.Flags{EnableStateDiff: true})
+	defer resetCfg()
+	setDefaultStateDiffExponents()
+
+	globalFlags := flags.GlobalFlags{
+		StateDiffExponents:         flags.Get().StateDiffExponents,
+		StateDiffValidateOnStartup: true,
+	}
+	flags.Init(&globalFlags)
+
+	store := setupDB(t)
+	require.NoError(t, store.db.Update(func(tx *bolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bolt.ErrBucketNotFound
+		}
+		st, _ := createState(t, 0, version.Phase0)
+		stateBytes, err := st.MarshalSSZ()
+		if err != nil {
+			return err
+		}
+		enc, err := addKey(st.Version(), stateBytes)
+		if err != nil {
+			return err
+		}
+		offsetBytes := make([]byte, 8)
+		binary.LittleEndian.PutUint64(offsetBytes, 0)
+		if err := bucket.Put(offsetKey, offsetBytes); err != nil {
+			return err
+		}
+		encoded, err := encodeStateDiffExponents(flags.Get().StateDiffExponents)
+		if err != nil {
+			return err
+		}
+		if err := bucket.Put(exponentsKey, encoded); err != nil {
+			return err
+		}
+		key := makeKeyForStateDiffTree(0, 0)
+		return bucket.Put(key, enc)
+	}))
+
+	err := store.startStateDiff(t.Context())
+	require.NoError(t, err)
+}
+
 func Test_setupBlockStorageType(t *testing.T) {
 	ctx := t.Context()
 	t.Run("fresh database with feature enabled to store full blocks should store full blocks", func(t *testing.T) {

beacon-chain/db/kv/state.go

@@ -1048,10 +1048,15 @@ func (s *Store) isStateValidatorMigrationOver() (bool, error) {
 }
 
 func (s *Store) getStateUsingStateDiff(ctx context.Context, blockRoot [32]byte) (state.BeaconState, error) {
-	slot, err := s.SlotByBlockRoot(ctx, blockRoot)
+	stateSummary, err := s.StateSummary(ctx, blockRoot)
 	if err != nil {
 		return nil, err
 	}
+	if stateSummary == nil {
+		return nil, ErrNotFoundState
+	}
+
+	slot := stateSummary.Slot
 
 	if uint64(slot) < s.getOffset() {
 		return nil, ErrSlotBeforeOffset
@@ -1065,14 +1070,33 @@ func (s *Store) getStateUsingStateDiff(ctx context.Context, blockRoot [32]byte)
 		return nil, errors.New("state not found")
 	}
 
+	blk, err := s.Block(ctx, blockRoot)
+	if err != nil {
+		return nil, err
+	}
+	if blk != nil && !blk.IsNil() {
+		stateRoot, err := st.HashTreeRoot(ctx)
+		if err != nil {
+			return nil, err
+		}
+		if stateRoot != blk.Block().StateRoot() {
+			return nil, errors.Wrap(ErrNotFoundState, "state root mismatch for block")
+		}
+	}
+
 	return st, nil
 }
 
 func (s *Store) hasStateUsingStateDiff(ctx context.Context, blockRoot [32]byte) (bool, error) {
-	slot, err := s.SlotByBlockRoot(ctx, blockRoot)
+	stateSummary, err := s.StateSummary(ctx, blockRoot)
 	if err != nil {
 		return false, err
 	}
+	if stateSummary == nil {
+		return false, nil
+	}
+
+	slot := stateSummary.Slot
 
 	if uint64(slot) < s.getOffset() {
 		return false, ErrSlotBeforeOffset

beacon-chain/db/kv/state_diff.go

@@ -133,6 +133,9 @@ func (s *Store) saveHdiff(lvl int, anchor, st state.ReadOnlyBeaconState) error {
 			return err
 		}
 	}
+	if err := s.stateDiffCache.setLevelHasData(lvl); err != nil {
+		return err
+	}
 
 	return nil
 }
@@ -172,6 +175,9 @@ func (s *Store) saveFullSnapshot(st state.ReadOnlyBeaconState) error {
 	if err != nil {
 		return err
 	}
+	if err := s.stateDiffCache.setLevelHasData(0); err != nil {
+		return err
+	}
 
 	return nil
 }

beacon-chain/db/kv/state_diff_cache.go

@@ -1,19 +1,131 @@
 package kv
 
 import (
+	"context"
 	"encoding/binary"
 	"errors"
 	"sync"
 
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/state"
 	"github.com/OffchainLabs/prysm/v7/cmd/beacon-chain/flags"
+	"github.com/OffchainLabs/prysm/v7/consensus-types/primitives"
+	pkgerrors "github.com/pkg/errors"
 	"go.etcd.io/bbolt"
 )
 
 type stateDiffCache struct {
 	sync.RWMutex
-	anchors []state.ReadOnlyBeaconState
-	offset  uint64
+	anchors        []state.ReadOnlyBeaconState
+	levelsWithData []bool
+	offset         uint64
+}
+
+func populateStateDiffCacheFromDB(s *Store, offset uint64) (*stateDiffCache, error) {
+	cache := &stateDiffCache{
+		anchors:        make([]state.ReadOnlyBeaconState, len(flags.Get().StateDiffExponents)-1),
+		levelsWithData: make([]bool, len(flags.Get().StateDiffExponents)),
+		offset:         offset,
+	}
+
+	if err := s.db.View(func(tx *bbolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bbolt.ErrBucketNotFound
+		}
+		for level := range cache.levelsWithData {
+			if level == 0 {
+				if bucket.Get(makeKeyForStateDiffTree(0, offset)) != nil {
+					cache.levelsWithData[level] = true
+				}
+				continue
+			}
+			cursor := bucket.Cursor()
+			prefix := []byte{byte(level)}
+			key, _ := cursor.Seek(prefix)
+			if key != nil && key[0] == byte(level) {
+				slot, ok := slotFromStateDiffKey(key)
+				if !ok {
+					return ErrStateDiffCorrupted
+				}
+				if slot < offset {
+					return ErrStateDiffCorrupted
+				}
+				if level == 0 && slot != offset {
+					return ErrStateDiffCorrupted
+				}
+				if computeLevel(offset, primitives.Slot(slot)) != level {
+					return ErrStateDiffCorrupted
+				}
+				cache.levelsWithData[level] = true
+			}
+		}
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+
+	anchor0, err := s.getFullSnapshot(offset)
+	if err != nil {
+		return nil, pkgerrors.Wrapf(ErrStateDiffMissingSnapshot, "state diff cache: missing offset snapshot at %d", offset)
+	}
+	cache.anchors[0] = anchor0
+	cache.levelsWithData[0] = true
+
+	return cache, nil
+}
+
+func validateStateDiffCache(ctx context.Context, s *Store, cache *stateDiffCache) error {
+	for level, hasData := range cache.levelsWithData {
+		if !hasData || level == 0 {
+			continue
+		}
+		maxSlot, err := latestSlotForLevel(s, level)
+		if err != nil {
+			return err
+		}
+		if _, err := s.stateByDiff(ctx, primitives.Slot(maxSlot)); err != nil {
+			return pkgerrors.Wrapf(ErrStateDiffCorrupted, "state diff validation failed for level %d slot %d: %v", level, maxSlot, err)
+		}
+	}
+	return nil
+}
+
+func latestSlotForLevel(s *Store, level int) (uint64, error) {
+	var maxSlot uint64
+	found := false
+	err := s.db.View(func(tx *bbolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bbolt.ErrBucketNotFound
+		}
+		cursor := bucket.Cursor()
+		prefix := []byte{byte(level)}
+		for key, _ := cursor.Seek(prefix); key != nil && key[0] == byte(level); key, _ = cursor.Next() {
+			slot, ok := slotFromStateDiffKey(key)
+			if !ok {
+				return ErrStateDiffCorrupted
+			}
+			if !found || slot > maxSlot {
+				maxSlot = slot
+				found = true
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return 0, err
+	}
+	if !found {
+		return 0, ErrStateDiffCorrupted
+	}
+	return maxSlot, nil
+}
+
+func slotFromStateDiffKey(key []byte) (uint64, bool) {
+	if len(key) < 9 {
+		return 0, false
+	}
+	return binary.LittleEndian.Uint64(key[1:9]), true
 }
 
 func newStateDiffCache(s *Store) (*stateDiffCache, error) {
@@ -37,8 +149,9 @@ func newStateDiffCache(s *Store) (*stateDiffCache, error) {
 	}
 
 	return &stateDiffCache{
-		anchors: make([]state.ReadOnlyBeaconState, len(flags.Get().StateDiffExponents)-1), // -1 because last level doesn't need to be cached
-		offset:  offset,
+		anchors:        make([]state.ReadOnlyBeaconState, len(flags.Get().StateDiffExponents)-1), // -1 because last level doesn't need to be cached
+		levelsWithData: make([]bool, len(flags.Get().StateDiffExponents)),
+		offset:         offset,
 	}, nil
 }
 
@@ -58,6 +171,25 @@ func (c *stateDiffCache) setAnchor(level int, anchor state.ReadOnlyBeaconState)
 	return nil
 }
 
+func (c *stateDiffCache) levelHasData(level int) bool {
+	c.RLock()
+	defer c.RUnlock()
+	if level < 0 || level >= len(c.levelsWithData) {
+		return false
+	}
+	return c.levelsWithData[level]
+}
+
+func (c *stateDiffCache) setLevelHasData(level int) error {
+	c.Lock()
+	defer c.Unlock()
+	if level < 0 || level >= len(c.levelsWithData) {
+		return errors.New("state diff cache: level data index out of range")
+	}
+	c.levelsWithData[level] = true
+	return nil
+}
+
 func (c *stateDiffCache) getOffset() uint64 {
 	c.RLock()
 	defer c.RUnlock()

beacon-chain/db/kv/state_diff_helpers.go

@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/state"
 	statenative "github.com/OffchainLabs/prysm/v7/beacon-chain/state/state-native"
@@ -21,9 +22,78 @@ import (
 
 var (
 	offsetKey           = []byte("offset")
+	exponentsKey        = []byte("exponents")
 	ErrSlotBeforeOffset = errors.New("slot is before state-diff root offset")
 )
 
+func encodeStateDiffExponents(exponents []int) ([]byte, error) {
+	if len(exponents) == 0 {
+		return nil, errors.New("state diff exponents cannot be empty")
+	}
+	if len(exponents) > 255 {
+		return nil, fmt.Errorf("state diff exponents length %d exceeds max 255", len(exponents))
+	}
+	encoded := make([]byte, len(exponents)+1)
+	encoded[0] = byte(len(exponents))
+	for i, exp := range exponents {
+		if exp < 2 || exp > flags.MaxStateDiffExponent {
+			return nil, fmt.Errorf("state diff exponent %d out of range for encoding", exp)
+		}
+		encoded[i+1] = byte(exp)
+	}
+	return encoded, nil
+}
+
+func decodeStateDiffExponents(encoded []byte) ([]int, error) {
+	if len(encoded) == 0 {
+		return nil, errors.New("state diff exponents missing length prefix")
+	}
+	count := int(encoded[0])
+	if count == 0 {
+		return nil, errors.New("state diff exponents length cannot be zero")
+	}
+	if len(encoded) != count+1 {
+		return nil, fmt.Errorf("state diff exponents length mismatch: expected %d got %d", count, len(encoded)-1)
+	}
+	exponents := make([]int, count)
+	for i := range count {
+		exponents[i] = int(encoded[i+1])
+	}
+	return exponents, nil
+}
+
+func formatStateDiffExponents(exponents []int) string {
+	if len(exponents) == 0 {
+		return ""
+	}
+	parts := make([]string, len(exponents))
+	for i, exp := range exponents {
+		parts[i] = fmt.Sprintf("%d", exp)
+	}
+	return strings.Join(parts, ",")
+}
+
+func (s *Store) loadStateDiffExponents() ([]int, error) {
+	var encoded []byte
+	err := s.db.View(func(tx *bbolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bbolt.ErrBucketNotFound
+		}
+		value := bucket.Get(exponentsKey)
+		if value == nil {
+			return errors.New("state diff exponents not found")
+		}
+		encoded = make([]byte, len(value))
+		copy(encoded, value)
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	return decodeStateDiffExponents(encoded)
+}
+
 func makeKeyForStateDiffTree(level int, slot uint64) []byte {
 	buf := make([]byte, 16)
 	buf[0] = byte(level)
@@ -124,6 +194,29 @@ func (s *Store) getOffset() uint64 {
 	return s.stateDiffCache.getOffset()
 }
 
+func (s *Store) loadOffset() (uint64, error) {
+	var offset uint64
+	err := s.db.View(func(tx *bbolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bbolt.ErrBucketNotFound
+		}
+		offsetBytes := bucket.Get(offsetKey)
+		if offsetBytes == nil {
+			return errors.New("state diff offset not found")
+		}
+		if len(offsetBytes) != 8 {
+			return fmt.Errorf("state diff offset has invalid length %d", len(offsetBytes))
+		}
+		offset = binary.LittleEndian.Uint64(offsetBytes)
+		return nil
+	})
+	if err != nil {
+		return 0, err
+	}
+	return offset, nil
+}
+
 // hasStateDiffOffset checks if the state-diff offset has been set in the database.
 // This is used to detect if an existing database has state-diff enabled.
 func (s *Store) hasStateDiffOffset() (bool, error) {
@@ -153,8 +246,13 @@ func (s *Store) initializeStateDiff(slot primitives.Slot, initialState state.Rea
 			return nil
 		}
 	}
-	// Write offset directly to the database (without using cache which doesn't exist yet).
-	err := s.db.Update(func(tx *bbolt.Tx) error {
+	exponentsBytes, err := encodeStateDiffExponents(flags.Get().StateDiffExponents)
+	if err != nil {
+		return pkgerrors.Wrap(err, "failed to encode state diff exponents")
+	}
+
+	// Write metadata directly to the database (without using cache which doesn't exist yet).
+	err = s.db.Update(func(tx *bbolt.Tx) error {
 		bucket := tx.Bucket(stateDiffBucket)
 		if bucket == nil {
 			return bbolt.ErrBucketNotFound
@@ -162,7 +260,10 @@ func (s *Store) initializeStateDiff(slot primitives.Slot, initialState state.Rea
 
 		offsetBytes := make([]byte, 8)
 		binary.LittleEndian.PutUint64(offsetBytes, uint64(slot))
-		return bucket.Put(offsetKey, offsetBytes)
+		if err := bucket.Put(offsetKey, offsetBytes); err != nil {
+			return err
+		}
+		return bucket.Put(exponentsKey, exponentsBytes)
 	})
 	if err != nil {
 		return pkgerrors.Wrap(err, "failed to set offset")
@@ -286,15 +387,20 @@ func (s *Store) getBaseAndDiffChain(offset uint64, slot primitives.Slot) (state.
 	}
 
 	var diffChainItems []diffItem
-	lastSeenAnchorSlot := baseAnchorSlot
+	lastSeenAnchorRelSlot := baseAnchorSlot - offset
 	for i, exp := range exponents[1 : lvl+1] {
 		span := math.PowerOf2(uint64(exp))
 		diffSlot := rel / span * span
-		if diffSlot == lastSeenAnchorSlot {
+		if diffSlot == lastSeenAnchorRelSlot {
 			continue
 		}
-		diffChainItems = append(diffChainItems, diffItem{level: i + 1, slot: diffSlot + offset})
-		lastSeenAnchorSlot = diffSlot
+		level := i + 1
+		if s.stateDiffCache != nil && !s.stateDiffCache.levelHasData(level) {
+			lastSeenAnchorRelSlot = diffSlot
+			continue
+		}
+		diffChainItems = append(diffChainItems, diffItem{level: level, slot: diffSlot + offset})
+		lastSeenAnchorRelSlot = diffSlot
 	}
 
 	baseSnapshot, err := s.getFullSnapshot(baseAnchorSlot)

beacon-chain/db/kv/state_diff_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/state"
 	"github.com/OffchainLabs/prysm/v7/cmd/beacon-chain/flags"
+	"github.com/OffchainLabs/prysm/v7/config/features"
 	"github.com/OffchainLabs/prysm/v7/config/params"
 	"github.com/OffchainLabs/prysm/v7/consensus-types/primitives"
 	"github.com/OffchainLabs/prysm/v7/math"
@@ -34,6 +35,81 @@ func TestStateDiff_LoadOrInitOffset(t *testing.T) {
 	require.Equal(t, uint64(10), offset)
 }
 
+func TestStateDiff_LoadOffset(t *testing.T) {
+	setDefaultStateDiffExponents()
+
+	db := setupDB(t)
+	_, err := db.loadOffset()
+	require.ErrorContains(t, "offset not found", err)
+
+	err = setOffsetInDB(db, 10)
+	require.NoError(t, err)
+	offset, err := db.loadOffset()
+	require.NoError(t, err)
+	require.Equal(t, uint64(10), offset)
+}
+
+func TestStateDiff_EncodeDecodeExponents(t *testing.T) {
+	t.Run("roundtrip", func(t *testing.T) {
+		exponents := []int{21, 18, 16, 13}
+		encoded, err := encodeStateDiffExponents(exponents)
+		require.NoError(t, err)
+		decoded, err := decodeStateDiffExponents(encoded)
+		require.NoError(t, err)
+		require.DeepEqual(t, exponents, decoded)
+	})
+
+	t.Run("encode-empty", func(t *testing.T) {
+		_, err := encodeStateDiffExponents(nil)
+		require.ErrorContains(t, "cannot be empty", err)
+	})
+
+	t.Run("encode-negative", func(t *testing.T) {
+		_, err := encodeStateDiffExponents([]int{21, -1})
+		require.ErrorContains(t, "out of range", err)
+	})
+
+	t.Run("encode-too-large", func(t *testing.T) {
+		_, err := encodeStateDiffExponents([]int{flags.MaxStateDiffExponent + 1})
+		require.ErrorContains(t, "out of range", err)
+	})
+
+	t.Run("decode-empty", func(t *testing.T) {
+		_, err := decodeStateDiffExponents(nil)
+		require.ErrorContains(t, "missing length prefix", err)
+	})
+
+	t.Run("decode-zero-length", func(t *testing.T) {
+		_, err := decodeStateDiffExponents([]byte{0})
+		require.ErrorContains(t, "length cannot be zero", err)
+	})
+
+	t.Run("decode-length-mismatch", func(t *testing.T) {
+		_, err := decodeStateDiffExponents([]byte{2, 10})
+		require.ErrorContains(t, "length mismatch", err)
+	})
+}
+
+func TestStateDiff_InitializeStoresExponents(t *testing.T) {
+	setDefaultStateDiffExponents()
+	resetCfg := features.InitWithReset(&features.Flags{EnableStateDiff: true})
+	defer resetCfg()
+
+	db := setupDB(t)
+	st, _ := createState(t, 0, version.Phase0)
+	require.NoError(t, db.initializeStateDiff(0, st))
+
+	stored, err := db.loadStateDiffExponents()
+	require.NoError(t, err)
+	require.DeepEqual(t, flags.Get().StateDiffExponents, stored)
+}
+
+func TestStateDiff_LoadExponentsMissing(t *testing.T) {
+	db := setupDB(t)
+	_, err := db.loadStateDiffExponents()
+	require.ErrorContains(t, "exponents not found", err)
+}
+
 func TestStateDiff_ComputeLevel(t *testing.T) {
 	db := setupDB(t)
 	setDefaultStateDiffExponents()
@@ -154,6 +230,124 @@ func TestStateDiff_SaveFullSnapshot(t *testing.T) {
 	}
 }
 
+func TestStateDiff_StateByDiff_NonZeroOffsetSkipsRedundantLevelDiff(t *testing.T) {
+	setStateDiffExponents([]int{6, 5, 4})
+
+	db := setupDB(t)
+
+	offset := uint64(1000)
+	require.NoError(t, setOffsetInDB(db, offset))
+
+	stOffset, _ := createState(t, primitives.Slot(offset), version.Phase0)
+	require.NoError(t, db.saveStateByDiff(context.Background(), stOffset))
+
+	st32, _ := createState(t, primitives.Slot(offset+32), version.Phase0)
+	require.NoError(t, db.saveStateByDiff(context.Background(), st32))
+
+	st64, _ := createState(t, primitives.Slot(offset+64), version.Phase0)
+	require.NoError(t, db.saveStateByDiff(context.Background(), st64))
+
+	st80, _ := createState(t, primitives.Slot(offset+80), version.Phase0)
+	require.NoError(t, db.saveStateByDiff(context.Background(), st80))
+
+	readSt, err := db.stateByDiff(context.Background(), primitives.Slot(offset+80))
+	require.NoError(t, err)
+
+	stWantSSZ, err := st80.MarshalSSZ()
+	require.NoError(t, err)
+	stGotSSZ, err := readSt.MarshalSSZ()
+	require.NoError(t, err)
+	require.DeepSSZEqual(t, stWantSSZ, stGotSSZ)
+}
+
+func TestStateDiff_PopulateStateDiffCacheFromDB(t *testing.T) {
+	setDefaultStateDiffExponents()
+
+	db := setupDB(t)
+	_, err := populateStateDiffCacheFromDB(db, 0)
+	require.ErrorContains(t, "missing offset snapshot", err)
+
+	st, _ := createState(t, 0, version.Phase0)
+	require.NoError(t, setOffsetInDB(db, 0))
+	require.NoError(t, db.saveStateByDiff(context.Background(), st))
+
+	err = db.db.Update(func(tx *bbolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bbolt.ErrBucketNotFound
+		}
+		key := makeKeyForStateDiffTree(2, math.PowerOf2(16))
+		return bucket.Put(append(key, stateSuffix...), []byte{1})
+	})
+	require.NoError(t, err)
+
+	cache, err := populateStateDiffCacheFromDB(db, 0)
+	require.NoError(t, err)
+	require.NotNil(t, cache)
+	require.Equal(t, uint64(0), cache.getOffset())
+	require.NotNil(t, cache.getAnchor(0))
+	require.Equal(t, true, cache.levelHasData(0))
+	require.Equal(t, false, cache.levelHasData(1))
+	require.Equal(t, true, cache.levelHasData(2))
+}
+
+func TestStateDiff_PopulateStateDiffCacheFromDB_InvalidLevelKey(t *testing.T) {
+	setDefaultStateDiffExponents()
+
+	db := setupDB(t)
+	st, _ := createState(t, 0, version.Phase0)
+	require.NoError(t, setOffsetInDB(db, 0))
+	require.NoError(t, db.saveStateByDiff(context.Background(), st))
+
+	require.NoError(t, db.db.Update(func(tx *bbolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bbolt.ErrBucketNotFound
+		}
+		key := makeKeyForStateDiffTree(2, 1)
+		return bucket.Put(append(key, stateSuffix...), []byte{1})
+	}))
+
+	_, err := populateStateDiffCacheFromDB(db, 0)
+	require.ErrorIs(t, ErrStateDiffCorrupted, err)
+}
+
+func TestStateDiff_GetBaseAndDiffChainSkipsEmptyLevels(t *testing.T) {
+	setDefaultStateDiffExponents()
+
+	db := setupDB(t)
+	require.NoError(t, setOffsetInDB(db, 0))
+	st, _ := createState(t, 0, version.Phase0)
+	require.NoError(t, db.saveFullSnapshot(st))
+
+	cache, err := populateStateDiffCacheFromDB(db, 0)
+	require.NoError(t, err)
+	cache.levelsWithData[0] = true
+	cache.levelsWithData[1] = false
+	cache.levelsWithData[2] = true
+	db.stateDiffCache = cache
+
+	slot := primitives.Slot(math.PowerOf2(18) + math.PowerOf2(16))
+	key := makeKeyForStateDiffTree(2, uint64(slot))
+	require.NoError(t, db.db.Update(func(tx *bbolt.Tx) error {
+		bucket := tx.Bucket(stateDiffBucket)
+		if bucket == nil {
+			return bbolt.ErrBucketNotFound
+		}
+		if err := bucket.Put(append(key, stateSuffix...), []byte{1}); err != nil {
+			return err
+		}
+		if err := bucket.Put(append(key, validatorSuffix...), []byte{2}); err != nil {
+			return err
+		}
+		return bucket.Put(append(key, balancesSuffix...), []byte{3})
+	}))
+
+	_, diffChain, err := db.getBaseAndDiffChain(0, slot)
+	require.NoError(t, err)
+	require.Equal(t, 1, len(diffChain))
+}
+
 func TestStateDiff_SaveAndReadFullSnapshot(t *testing.T) {
 	setDefaultStateDiffExponents()
 
@@ -659,8 +853,10 @@ func setOffsetInDB(s *Store, offset uint64) error {
 }
 
 func setDefaultStateDiffExponents() {
-	globalFlags := flags.GlobalFlags{
-		StateDiffExponents: []int{21, 18, 16, 13, 11, 9, 5},
-	}
+	setStateDiffExponents([]int{21, 18, 16, 13, 11, 9, 5})
+}
+
+func setStateDiffExponents(exponents []int) {
+	globalFlags := flags.GlobalFlags{StateDiffExponents: exponents}
 	flags.Init(&globalFlags)
 }

beacon-chain/db/kv/state_test.go

@@ -26,7 +26,6 @@ import (
 	"github.com/OffchainLabs/prysm/v7/testing/assert"
 	"github.com/OffchainLabs/prysm/v7/testing/require"
 	"github.com/OffchainLabs/prysm/v7/testing/util"
-	logTest "github.com/sirupsen/logrus/hooks/test"
 	bolt "go.etcd.io/bbolt"
 )
 
@@ -1349,7 +1348,7 @@ func TestStore_CanSaveRetrieveStateUsingStateDiff(t *testing.T) {
 
 		readSt, err := db.State(context.Background(), [32]byte{'A'})
 		require.IsNil(t, readSt)
-		require.ErrorContains(t, "neither state summary nor block found", err)
+		require.ErrorIs(t, err, ErrNotFoundState)
 	})
 
 	t.Run("Slot not in tree", func(t *testing.T) {
@@ -1477,14 +1476,8 @@ func TestStore_CanSaveRetrieveStateUsingStateDiff(t *testing.T) {
 					require.NoError(t, err)
 
 					readSt, err := db.State(context.Background(), r)
-					require.NoError(t, err)
-					require.NotNil(t, readSt)
-
-					stSSZ, err := st.MarshalSSZ()
-					require.NoError(t, err)
-					readStSSZ, err := readSt.MarshalSSZ()
-					require.NoError(t, err)
-					require.DeepSSZEqual(t, stSSZ, readStSSZ)
+					require.ErrorIs(t, err, ErrNotFoundState)
+					require.IsNil(t, readSt)
 				})
 			}
 		})
@@ -1578,14 +1571,8 @@ func TestStore_CanSaveRetrieveStateUsingStateDiff(t *testing.T) {
 					require.NoError(t, err)
 
 					readSt, err := db.State(context.Background(), r)
-					require.NoError(t, err)
-					require.NotNil(t, readSt)
-
-					stSSZ, err := st.MarshalSSZ()
-					require.NoError(t, err)
-					readStSSZ, err := readSt.MarshalSSZ()
-					require.NoError(t, err)
-					require.DeepSSZEqual(t, stSSZ, readStSSZ)
+					require.ErrorIs(t, err, ErrNotFoundState)
+					require.IsNil(t, readSt)
 				})
 			}
 		})
@@ -1594,7 +1581,6 @@ func TestStore_CanSaveRetrieveStateUsingStateDiff(t *testing.T) {
 
 func TestStore_HasStateUsingStateDiff(t *testing.T) {
 	t.Run("No state summary or block", func(t *testing.T) {
-		hook := logTest.NewGlobal()
 		db := setupDB(t)
 		featCfg := &features.Flags{}
 		featCfg.EnableStateDiff = true
@@ -1607,7 +1593,6 @@ func TestStore_HasStateUsingStateDiff(t *testing.T) {
 
 		hasSt := db.HasState(t.Context(), [32]byte{'A'})
 		require.Equal(t, false, hasSt)
-		require.LogsContain(t, hook, "neither state summary nor block found")
 	})
 
 	t.Run("slot in tree or not", func(t *testing.T) {

beacon-chain/node/node.go

@@ -550,6 +550,12 @@ func openDB(ctx context.Context, dbPath string, clearer *dbClearer) (*kv.Store,
 		cfg := features.Get()
 		cfg.EnableStateDiff = false
 		features.Init(cfg)
+	} else if errors.Is(err, kv.ErrStateDiffExponentMismatch) {
+		log.WithError(err).Error("State-diff configuration mismatch; restart aborted. Use the stored exponents or re-sync the database.")
+		return nil, err
+	} else if errors.Is(err, kv.ErrStateDiffMissingSnapshot) || errors.Is(err, kv.ErrStateDiffCorrupted) {
+		log.WithError(err).Error("State-diff database corrupted; restart aborted. Delete database and re-sync from genesis/checkpoint.")
+		return nil, err
 	} else if err != nil {
 		return nil, errors.Wrapf(err, "could not create database at %s", dbPath)
 	}

beacon-chain/state/stategen/getter.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/core/helpers"
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/core/time"
+	"github.com/OffchainLabs/prysm/v7/beacon-chain/db"
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/state"
 	"github.com/OffchainLabs/prysm/v7/config/params"
 	"github.com/OffchainLabs/prysm/v7/consensus-types/blocks"
@@ -122,8 +123,13 @@ func (s *State) StateByRootInitialSync(ctx context.Context, blockRoot [32]byte)
 	}
 
 	if s.beaconDB.HasState(ctx, blockRoot) {
-		s, err := s.beaconDB.State(ctx, blockRoot)
-		return s, errors.Wrap(err, "failed to retrieve init-sync state from db")
+		st, err := s.beaconDB.State(ctx, blockRoot)
+		if err == nil {
+			return st, nil
+		}
+		if !stderrors.Is(err, db.ErrNotFoundState) {
+			return nil, errors.Wrap(err, "failed to retrieve init-sync state from db")
+		}
 	}
 
 	startState, err := s.latestAncestor(ctx, blockRoot)
@@ -213,7 +219,13 @@ func (s *State) loadStateByRoot(ctx context.Context, blockRoot [32]byte) (state.
 
 	// Short circuit if the state is already in the DB.
 	if s.beaconDB.HasState(ctx, blockRoot) {
-		return s.beaconDB.State(ctx, blockRoot)
+		st, err := s.beaconDB.State(ctx, blockRoot)
+		if err == nil {
+			return st, nil
+		}
+		if !stderrors.Is(err, db.ErrNotFoundState) {
+			return nil, err
+		}
 	}
 
 	summary, err := s.stateSummary(ctx, blockRoot)

beacon-chain/state/stategen/getter_test.go

@@ -185,6 +185,71 @@ type testSetupSlots struct {
 	lastblock primitives.Slot
 }
 
+type notFoundOnRootDB struct {
+	db.NoHeadAccessDatabase
+	target [32]byte
+}
+
+func (d *notFoundOnRootDB) HasState(ctx context.Context, blockRoot [32]byte) bool {
+	if blockRoot == d.target {
+		return true
+	}
+	return d.NoHeadAccessDatabase.HasState(ctx, blockRoot)
+}
+
+func (d *notFoundOnRootDB) State(ctx context.Context, blockRoot [32]byte) (state.BeaconState, error) {
+	if blockRoot == d.target {
+		return nil, db.ErrNotFoundState
+	}
+	return d.NoHeadAccessDatabase.State(ctx, blockRoot)
+}
+
+func TestStateByRoot_FallsBackToReplayOnNotFoundStateFromDirectRead(t *testing.T) {
+	ctx := t.Context()
+	beaconDB := testDB.SetupDB(t)
+
+	st9, _ := util.DeterministicGenesisState(t, 32)
+	st9, err := ReplayProcessSlots(ctx, st9, 9)
+	require.NoError(t, err)
+
+	hdr := st9.LatestBlockHeader()
+	hdrRoot, err := hdr.HashTreeRoot()
+	require.NoError(t, err)
+
+	st10 := st9.Copy()
+	blk10 := util.NewBeaconBlock()
+	blk10.Block.Slot = 10
+	blk10.Block.ParentRoot = hdrRoot[:]
+	idx10, err := helpers.BeaconProposerIndexAtSlot(ctx, st10, blk10.Block.Slot)
+	require.NoError(t, err)
+	blk10.Block.ProposerIndex = idx10
+	ib10, err := blt.NewSignedBeaconBlock(blk10)
+	require.NoError(t, err)
+
+	st10, err = executeStateTransitionStateGen(ctx, st10, ib10)
+	require.NoError(t, err)
+	st10Root, err := st10.HashTreeRoot(ctx)
+	require.NoError(t, err)
+	blk10.Block.StateRoot = st10Root[:]
+
+	util.SaveBlock(t, ctx, beaconDB, blk10)
+	require.NoError(t, beaconDB.SaveState(ctx, st9, hdrRoot))
+
+	ib10, err = blt.NewSignedBeaconBlock(blk10)
+	require.NoError(t, err)
+	rob10, err := blt.NewROBlock(ib10)
+	require.NoError(t, err)
+
+	service := New(&notFoundOnRootDB{NoHeadAccessDatabase: beaconDB, target: rob10.Root()}, doublylinkedtree.New())
+
+	got, err := service.StateByRoot(ctx, rob10.Root())
+	require.NoError(t, err)
+
+	gotRoot, err := got.HashTreeRoot(ctx)
+	require.NoError(t, err)
+	require.Equal(t, st10Root, gotRoot)
+}
+
 func TestLoadStateByRoot(t *testing.T) {
 	ctx := t.Context()
 	persistEpochBoundary := func(r testChain, slot primitives.Slot) {

cmd/beacon-chain/flags/base.go

@@ -356,6 +356,11 @@ var (
 		Usage: "A comma-separated list of exponents (of 2) in decreasing order, defining the state diff hierarchy levels. The last exponent must be greater than or equal to 5.",
 		Value: cli.NewIntSlice(21, 18, 16, 13, 11, 9, 5),
 	}
+	// StateDiffValidateOnStartup validates state diff data on startup.
+	StateDiffValidateOnStartup = &cli.BoolFlag{
+		Name:  "disable-hdiff-validate-on-startup",
+		Usage: "Disables state-diff validation on startup (enabled by default).",
+	}
 	// DisableEphemeralLogFile disables the 24 hour debug log file.
 	DisableEphemeralLogFile = &cli.BoolFlag{
 		Name:  "disable-ephemeral-log-file",

cmd/beacon-chain/flags/config.go

@@ -9,24 +9,25 @@ import (
 	"github.com/urfave/cli/v2"
 )
 
-const maxStateDiffExponents = 30
+const MaxStateDiffExponent = 30
 
 // GlobalFlags specifies all the global flags for the
 // beacon node.
 type GlobalFlags struct {
-	SubscribeToAllSubnets           bool
+	StateDiffValidateOnStartup      bool
 	Supernode                       bool
-	SemiSupernode                   bool
 	DisableGetBlobsV2               bool
-	MinimumSyncPeers                int
-	MinimumPeersPerSubnet           int
-	MaxConcurrentDials              int
-	BlockBatchLimit                 int
-	BlockBatchLimitBurstFactor      int
-	BlobBatchLimit                  int
+	SemiSupernode                   bool
+	SubscribeToAllSubnets           bool
 	BlobBatchLimitBurstFactor       int
 	DataColumnBatchLimit            int
+	BlockBatchLimit                 int
+	MaxConcurrentDials              int
+	MinimumPeersPerSubnet           int
+	MinimumSyncPeers                int
 	DataColumnBatchLimitBurstFactor int
+	BlockBatchLimitBurstFactor      int
+	BlobBatchLimit                  int
 	StateDiffExponents              []int
 }
 
@@ -80,6 +81,7 @@ func ConfigureGlobalFlags(ctx *cli.Context) error {
 
 	// State-diff-exponents
 	cfg.StateDiffExponents = ctx.IntSlice(StateDiffExponents.Name)
+	cfg.StateDiffValidateOnStartup = !ctx.Bool(StateDiffValidateOnStartup.Name)
 	if features.Get().EnableStateDiff {
 		if err := validateStateDiffExponents(cfg.StateDiffExponents); err != nil {
 			return err
@@ -88,6 +90,9 @@ func ConfigureGlobalFlags(ctx *cli.Context) error {
 		if ctx.IsSet(StateDiffExponents.Name) {
 			log.Warn("--state-diff-exponents is set but --enable-state-diff is not; the value will be ignored.")
 		}
+		if ctx.IsSet(StateDiffValidateOnStartup.Name) {
+			log.Warn("--disable-hdiff-validate-on-startup is set but --enable-state-diff is not; the value will be ignored.")
+		}
 	}
 
 	cfg.BlockBatchLimit = ctx.Int(BlockBatchLimit.Name)
@@ -132,7 +137,7 @@ func validateStateDiffExponents(exponents []int) error {
 	if exponents[length-1] < 5 {
 		return errors.New("the last state diff exponent must be at least 5")
 	}
-	prev := maxStateDiffExponents + 1
+	prev := MaxStateDiffExponent + 1
 	for _, exp := range exponents {
 		if exp >= prev {
 			return errors.New("state diff exponents must be in strictly decreasing order, and each exponent must be <= 30")

cmd/beacon-chain/main.go

@@ -161,6 +161,7 @@ var appFlags = []cli.Flag{
 	dasFlags.BlobRetentionEpochFlag,
 	flags.BatchVerifierLimit,
 	flags.StateDiffExponents,
+	flags.StateDiffValidateOnStartup,
 	flags.DisableEphemeralLogFile,
 }
 

cmd/beacon-chain/usage.go

@@ -75,6 +75,7 @@ var appHelpFlagGroups = []flagGroup{
 			flags.RPCPort,
 			flags.BatchVerifierLimit,
 			flags.StateDiffExponents,
+			flags.StateDiffValidateOnStartup,
 		},
 	},
 	{