feat(preconf): trigger optimistic FCU for whitelisted proposers

Author: fridrik01

beacon/blockchain/payload_test.go

@@ -134,6 +134,7 @@ func TestOptimisticBlockBuildingRejectedBlockStateChecks(t *testing.T) {
 		ctx.ConsensusCtx(),
 		types.NewConsensusBlock(invalidBlk, proposerAddress, consensusTime),
 		true, // this block is next block proposer
+		proposerAddress,
 	)
 	require.ErrorIs(t, err, core.ErrProposerMismatch)
 
@@ -241,6 +242,7 @@ func TestOptimisticBlockBuildingVerifiedBlockStateChecks(t *testing.T) {
 		ctx.ConsensusCtx(),
 		types.NewConsensusBlock(validBlk, ctx.ProposerAddress(), consensusTime),
 		true, // this block is next block proposer
+		ctx.ProposerAddress(),
 	)
 	require.NoError(t, err)
 
@@ -282,6 +284,8 @@ func setupOptimisticPayloadTests(t *testing.T, cs chain.Spec) (
 		b,
 		sp,
 		ts,
+		nil, // preconf.Config unused in this test
+		nil, // preconf.Whitelist unused in this test
 	)
 	return chain, st, cms, ctx, sp, b, sb, eng, depStore
 }

beacon/blockchain/process_proposal.go

@@ -155,6 +155,7 @@ func (s *Service) ProcessProposal(
 		ctx,
 		consensusBlk,
 		bytes.Equal(thisNodeAddress, req.NextProposerAddress),
+		req.NextProposerAddress,
 	)
 	if err != nil {
 		s.logger.Error("failed to verify incoming block", "error", err)
@@ -259,6 +260,7 @@ func (s *Service) VerifyIncomingBlock(
 	ctx context.Context,
 	blk *types.ConsensusBlock,
 	isNextBlockProposer bool,
+	nextProposerAddress []byte,
 ) (transition.ValidatorUpdates, error) {
 	beaconBlk := blk.GetBeaconBlock()
 	state := s.storageBackend.StateFromContext(ctx)
@@ -302,7 +304,7 @@ func (s *Service) VerifyIncomingBlock(
 	var (
 		nextBlockData          *builder.RequestPayloadData
 		errFetch               error
-		shouldBuildNextPayload = s.shouldBuildNextPayload(isNextBlockProposer)
+		shouldBuildNextPayload = s.shouldBuildNextPayload(isNextBlockProposer, state, nextProposerAddress)
 	)
 
 	if shouldBuildNextPayload {
@@ -398,8 +400,51 @@ func (s *Service) verifyStateRoot(
 	return valUpdates, err
 }
 
-// shouldBuildNextPayload returns true if optimistic
-// payload builds are enabled.
-func (s *Service) shouldBuildNextPayload(isNextBlockProposer bool) bool {
-	return isNextBlockProposer && s.localBuilder.Enabled()
+// shouldBuildNextPayload returns true if optimistic payload builds should be triggered.
+// In normal mode, builds only when this node is the next proposer.
+// In sequencer mode, also builds when the next proposer is whitelisted.
+func (s *Service) shouldBuildNextPayload(isNextBlockProposer bool, st *statedb.StateDB, nextProposerAddress []byte) bool {
+	if !s.localBuilder.Enabled() {
+		return false
+	}
+
+	// Normal behavior: build if we are the proposer
+	if isNextBlockProposer {
+		return true
+	}
+
+	// Sequencer mode: build if next proposer is whitelisted
+	if s.preconfCfg != nil && s.preconfCfg.IsSequencer() {
+		nextProposerPubkey, err := s.getNextProposerPubkey(st, nextProposerAddress)
+		if err != nil {
+			s.logger.Error("Failed to get next proposer pubkey", "error", err)
+			return false
+		}
+
+		isWhitelisted := s.preconfWhitelist.IsWhitelisted(nextProposerPubkey)
+		if isWhitelisted {
+			s.logger.Info("Sequencer mode: next proposer is whitelisted, triggering optimistic build")
+		}
+
+		return isWhitelisted
+	}
+
+	return false
+}
+
+// getNextProposerPubkey retrieves the BLS public key for the next proposer given their CometBFT address.
+func (s *Service) getNextProposerPubkey(st *statedb.StateDB, nextProposerAddress []byte) (crypto.BLSPubkey, error) {
+	// Convert CometBFT address to validator index
+	proposerIndex, err := st.ValidatorIndexByCometBFTAddress(nextProposerAddress)
+	if err != nil {
+		return crypto.BLSPubkey{}, fmt.Errorf("failed to get validator index: %w", err)
+	}
+
+	// Get validator record
+	validator, err := st.ValidatorByIndex(proposerIndex)
+	if err != nil {
+		return crypto.BLSPubkey{}, fmt.Errorf("failed to get validator: %w", err)
+	}
+
+	return validator.GetPubkey(), nil
 }

beacon/blockchain/service.go

@@ -26,6 +26,7 @@ import (
 	"sync"
 	"sync/atomic"
 
+	"github.com/berachain/beacon-kit/beacon/preconf"
 	engineprimitives "github.com/berachain/beacon-kit/engine-primitives/engine-primitives"
 	"github.com/berachain/beacon-kit/execution/deposit"
 	"github.com/berachain/beacon-kit/log"
@@ -69,6 +70,16 @@ type Service struct {
 	// It helps avoid resending the same FCU data (and spares a network call)
 	// in case optimistic block building is active
 	latestFcuReq atomic.Pointer[engineprimitives.ForkchoiceStateV1]
+
+	// preconfCfg holds the preconfirmation configuration.
+	preconfCfg *preconf.Config
+
+	// preconfWhitelist contains whitelisted validator pubkeys for preconfirmation.
+	// Used by both sequencer and validators:
+	// - Sequencer: checks if next proposer is whitelisted to trigger optimistic FCU
+	// - Validator: checks if self is whitelisted to fetch payload from sequencer
+	// Can be nil if preconf is disabled.
+	preconfWhitelist preconf.Whitelist
 }
 
 // NewService creates a new validator service.
@@ -82,6 +93,8 @@ func NewService(
 	localBuilder LocalBuilder,
 	stateProcessor StateProcessor,
 	telemetrySink TelemetrySink,
+	preconfCfg *preconf.Config,
+	preconfWhitelist preconf.Whitelist,
 ) *Service {
 	return &Service{
 		storageBackend:       storageBackend,
@@ -96,6 +109,8 @@ func NewService(
 		stateProcessor:       stateProcessor,
 		metrics:              newChainMetrics(telemetrySink),
 		forceStartupSyncOnce: new(sync.Once),
+		preconfCfg:           preconfCfg,
+		preconfWhitelist:     preconfWhitelist,
 	}
 }
 

beacon/preconf/loader.go

@@ -35,7 +35,7 @@ func LoadWhitelist(path string) ([]crypto.BLSPubkey, error) {
 		return nil, errors.New("whitelist path is empty")
 	}
 
-	data, err := os.ReadFile(path)
+	data, err := os.ReadFile(path) // #nosec G304 -- path from operator-controlled config
 	if err != nil {
 		return nil, errors.Wrapf(err, "failed to read whitelist file: %s", path)
 	}

cmd/beacond/defaults.go

@@ -42,6 +42,7 @@ func DefaultComponents() []any {
 		components.ProvideExecutionEngine,
 		components.ProvideJWTSecret,
 		components.ProvideLocalBuilder,
+		components.ProvidePreconfWhitelist,
 		components.ProvideReportingService,
 		components.ProvideCometBFTService,
 		components.ProvideServiceRegistry,

node-core/components/chain_service.go

@@ -23,7 +23,9 @@ package components
 import (
 	"cosmossdk.io/depinject"
 	"github.com/berachain/beacon-kit/beacon/blockchain"
+	"github.com/berachain/beacon-kit/beacon/preconf"
 	"github.com/berachain/beacon-kit/chain"
+	"github.com/berachain/beacon-kit/config"
 	"github.com/berachain/beacon-kit/execution/deposit"
 	"github.com/berachain/beacon-kit/execution/engine"
 	"github.com/berachain/beacon-kit/log/phuslu"
@@ -35,6 +37,7 @@ import (
 type ChainServiceInput struct {
 	depinject.In
 
+	Cfg                   *config.Config
 	ChainSpec             chain.Spec
 	ExecutionEngine       *engine.Engine
 	LocalBuilder          LocalBuilder
@@ -44,6 +47,7 @@ type ChainServiceInput struct {
 	BlobProcessor         BlobProcessor
 	TelemetrySink         *metrics.TelemetrySink
 	BeaconDepositContract deposit.Contract
+	PreconfWhitelist      preconf.Whitelist
 }
 
 // ProvideChainService is a depinject provider for the blockchain service.
@@ -58,5 +62,7 @@ func ProvideChainService(in ChainServiceInput) *blockchain.Service {
 		in.LocalBuilder,
 		in.StateProcessor,
 		in.TelemetrySink,
+		&in.Cfg.Preconf,
+		in.PreconfWhitelist,
 	)
 }

testing/simulated/components.go

@@ -49,6 +49,7 @@ func FixedComponents(t *testing.T) []any {
 		components.ProvideExecutionEngine,
 		components.ProvideJWTSecret,
 		components.ProvideLocalBuilder,
+		components.ProvidePreconfWhitelist,
 		components.ProvideReportingService,
 		components.ProvideServiceRegistry,
 		components.ProvideSidecarFactory,