diff --git a/cl/persistence/beacon_indicies/indicies.go b/cl/persistence/beacon_indicies/indicies.go
index dac453e0d96..b3994792b52 100644
--- a/cl/persistence/beacon_indicies/indicies.go
+++ b/cl/persistence/beacon_indicies/indicies.go
@@ -244,10 +244,15 @@ func WriteParentBlockRoot(ctx context.Context, tx kv.RwTx, blockRoot, parentRoot
 	return tx.Put(kv.BlockRootToParentRoot, blockRoot[:], parentRoot[:])
 }
 
-func TruncateCanonicalChain(ctx context.Context, tx kv.RwTx, slot uint64) error {
-	return tx.ForEach(kv.CanonicalBlockRoots, base_encoding.Encode64ToBytes4(slot), func(k, _ []byte) error {
+func TruncateCanonicalChain(ctx context.Context, tx kv.RwTx, slot uint64) (uint64, common.Hash, error) {
+	var highestSlot uint64
+	var highestRoot common.Hash
+	err := tx.ForEach(kv.CanonicalBlockRoots, base_encoding.Encode64ToBytes4(slot), func(k, v []byte) error {
+		highestSlot = base_encoding.Decode64FromBytes4(k)
+		copy(highestRoot[:], v)
 		return tx.Delete(kv.CanonicalBlockRoots, k)
 	})
+	return highestSlot, highestRoot, err
 }
 
 func PruneSignedHeaders(tx kv.RwTx, from uint64) error {
diff --git a/cl/persistence/beacon_indicies/indicies_test.go b/cl/persistence/beacon_indicies/indicies_test.go
index 2df26462d8c..2bed0c10df3 100644
--- a/cl/persistence/beacon_indicies/indicies_test.go
+++ b/cl/persistence/beacon_indicies/indicies_test.go
@@ -120,13 +120,57 @@ func TestTruncateCanonicalChain(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, common.Hash(blockRoot), canonicalRoot)
 
-	require.NoError(t, TruncateCanonicalChain(context.Background(), tx, 0))
+	_, _, err = TruncateCanonicalChain(context.Background(), tx, 0)
+	require.NoError(t, err)
 
 	canonicalRoot, err = ReadCanonicalBlockRoot(tx, block.Block.Slot)
 	require.NoError(t, err)
 	require.Equal(t, common.Hash{}, canonicalRoot)
 }
 
+// TestTruncateCanonicalChainReturnsHighest verifies that TruncateCanonicalChain
+// returns the slot and root of the highest entry it deleted, and preserves
+// entries below the truncation point.
+func TestTruncateCanonicalChainReturnsHighest(t *testing.T) {
+	db := setupTestDB(t)
+	defer db.Close()
+	tx, err := db.BeginRw(context.Background())
+	require.NoError(t, err)
+	defer tx.Rollback()
+
+	slots := []uint64{100, 101, 102, 103, 104}
+	roots := make([]common.Hash, len(slots))
+	for i, slot := range slots {
+		block := cltypes.NewSignedBeaconBlock(&clparams.MainnetBeaconConfig, clparams.Phase0Version)
+		block.Block.Slot = slot
+		block.Block.ParentRoot = common.Hash{byte(i + 1)}
+		require.NoError(t, WriteBeaconBlockHeaderAndIndicies(context.Background(), tx, block.SignedBeaconBlockHeader(), true))
+		root, err := block.Block.HashSSZ()
+		require.NoError(t, err)
+		roots[i] = common.Hash(root)
+	}
+
+	// Truncate from slot 102: deletes 102/103/104, preserves 100/101.
+	highestSlot, highestRoot, err := TruncateCanonicalChain(context.Background(), tx, 102)
+	require.NoError(t, err)
+	require.Equal(t, uint64(104), highestSlot)
+	require.Equal(t, roots[4], highestRoot)
+
+	// Slots 100, 101 must still be canonical.
+	for i, slot := range []uint64{100, 101} {
+		preserved, err := ReadCanonicalBlockRoot(tx, slot)
+		require.NoError(t, err)
+		require.Equal(t, roots[i], preserved)
+	}
+
+	// Slots 102, 103, 104 must be gone.
+	for _, slot := range []uint64{102, 103, 104} {
+		gone, err := ReadCanonicalBlockRoot(tx, slot)
+		require.NoError(t, err)
+		require.Equal(t, common.Hash{}, gone)
+	}
+}
+
 func TestReadBeaconBlockHeader(t *testing.T) {
 	db := setupTestDB(t)
 	defer db.Close()
diff --git a/cl/phase1/stages/forkchoice.go b/cl/phase1/stages/forkchoice.go
index acbb8d3f1eb..5ec15961f37 100644
--- a/cl/phase1/stages/forkchoice.go
+++ b/cl/phase1/stages/forkchoice.go
@@ -107,18 +107,6 @@ func updateCanonicalChainInTheDatabase(ctx context.Context, tx kv.RwTx, headSlot
 		return fmt.Errorf("failed to read canonical block root: %w", err)
 	}
 
-	oldCanonical := common.Hash{}
-	// Guard against uint64 underflow: currentSlot=0 → currentSlot-1 = MaxUint64 → infinite loop.
-	for i := currentSlot; i > 1; i-- {
-		oldCanonical, err = beacon_indicies.ReadCanonicalBlockRoot(tx, i-1)
-		if err != nil {
-			return fmt.Errorf("failed to read canonical block root: %w", err)
-		}
-		if oldCanonical != (common.Hash{}) {
-			break
-		}
-	}
-
 	// List of new canonical chain entries
 	reconnectionRoots := []canonicalEntry{{currentSlot, currentRoot}}
 
@@ -151,8 +139,10 @@ func updateCanonicalChainInTheDatabase(ctx context.Context, tx kv.RwTx, headSlot
 		reconnectionRoots = append(reconnectionRoots, canonicalEntry{currentSlot, currentRoot})
 	}
 
-	// Truncate the canonical chain at the current slot
-	if err := beacon_indicies.TruncateCanonicalChain(ctx, tx, currentSlot); err != nil {
+	// Truncate the canonical chain at the common ancestor and capture the
+	// previous canonical tip (highest slot/root deleted) for the chain_reorg event.
+	oldCanonicalSlot, oldCanonical, err := beacon_indicies.TruncateCanonicalChain(ctx, tx, currentSlot)
+	if err != nil {
 		return fmt.Errorf("failed to truncate canonical chain: %w", err)
 	}
 
@@ -168,12 +158,9 @@ func updateCanonicalChainInTheDatabase(ctx context.Context, tx kv.RwTx, headSlot
 		return fmt.Errorf("failed to mark root canonical: %w", err)
 	}
 
-	// check reorg
-	parentRoot, err := beacon_indicies.ReadParentBlockRoot(ctx, tx, headRoot)
-	if err != nil {
-		return fmt.Errorf("failed to read parent block root: %w", err)
-	}
-	if parentRoot != oldCanonical {
+	// A reorg occurred if the previous canonical chain extended past the
+	// common ancestor. currentSlot is the common ancestor's slot here.
+	if oldCanonical != (common.Hash{}) && currentSlot < oldCanonicalSlot {
 		log.Debug("cl reorg", "new_head_slot", headSlot, "fork_slot", currentSlot, "old_canonical", oldCanonical, "new_canonical", headRoot)
 		oldStateRoot, err := beacon_indicies.ReadStateRootByBlockRoot(ctx, tx, oldCanonical)
 		if err != nil {
@@ -187,7 +174,7 @@ func updateCanonicalChainInTheDatabase(ctx context.Context, tx kv.RwTx, headSlot
 		}
 		reorgEvent := &beaconevents.ChainReorgData{
 			Slot:                headSlot,
-			Depth:               currentSlot - headSlot,
+			Depth:               oldCanonicalSlot - currentSlot,
 			OldHeadBlock:        oldCanonical,
 			NewHeadBlock:        headRoot,
 			OldHeadState:        oldStateRoot,