diff --git a/accounts/abi/type_test.go b/accounts/abi/type_test.go
index ae69872ad8..95922548c4 100644
--- a/accounts/abi/type_test.go
+++ b/accounts/abi/type_test.go
@@ -25,7 +25,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 )
 
-// typeWithoutStringer is a alias for the Type type which simply doesn't implement
+// typeWithoutStringer is an alias for the Type type which simply doesn't implement
 // the stringer interface to allow printing type details in the tests below.
 type typeWithoutStringer Type
 
diff --git a/beacon/blsync/block_sync.go b/beacon/blsync/block_sync.go
index 3ab156354d..ff689a922f 100755
--- a/beacon/blsync/block_sync.go
+++ b/beacon/blsync/block_sync.go
@@ -41,7 +41,7 @@ type beaconBlockSync struct {
 
 type headTracker interface {
 	PrefetchHead() types.HeadInfo
-	ValidatedHead() (types.SignedHeader, bool)
+	ValidatedOptimistic() (types.OptimisticUpdate, bool)
 	ValidatedFinality() (types.FinalityUpdate, bool)
 }
 
@@ -66,6 +66,7 @@ func (s *beaconBlockSync) Process(requester request.Requester, events []request.
 		case request.EvResponse, request.EvFail, request.EvTimeout:
 			sid, req, resp := event.RequestInfo()
 			blockRoot := common.Hash(req.(sync.ReqBeaconBlock))
+			log.Debug("Beacon block event", "type", event.Type.Name, "hash", blockRoot)
 			if resp != nil {
 				s.recentBlocks.Add(blockRoot, resp.(*types.BeaconBlock))
 			}
@@ -80,8 +81,8 @@ func (s *beaconBlockSync) Process(requester request.Requester, events []request.
 	}
 	s.updateEventFeed()
 	// request validated head block if unavailable and not yet requested
-	if vh, ok := s.headTracker.ValidatedHead(); ok {
-		s.tryRequestBlock(requester, vh.Header.Hash(), false)
+	if vh, ok := s.headTracker.ValidatedOptimistic(); ok {
+		s.tryRequestBlock(requester, vh.Attested.Hash(), false)
 	}
 	// request prefetch head if the given server has announced it
 	if prefetchHead := s.headTracker.PrefetchHead().BlockRoot; prefetchHead != (common.Hash{}) {
@@ -114,12 +115,12 @@ func blockHeadInfo(block *types.BeaconBlock) types.HeadInfo {
 }
 
 func (s *beaconBlockSync) updateEventFeed() {
-	head, ok := s.headTracker.ValidatedHead()
+	optimistic, ok := s.headTracker.ValidatedOptimistic()
 	if !ok {
 		return
 	}
 
-	validatedHead := head.Header.Hash()
+	validatedHead := optimistic.Attested.Hash()
 	headBlock, ok := s.recentBlocks.Get(validatedHead)
 	if !ok {
 		return
@@ -127,7 +128,7 @@ func (s *beaconBlockSync) updateEventFeed() {
 
 	var finalizedHash common.Hash
 	if finality, ok := s.headTracker.ValidatedFinality(); ok {
-		he := head.Header.Epoch()
+		he := optimistic.Attested.Epoch()
 		fe := finality.Attested.Header.Epoch()
 		switch {
 		case he == fe:
@@ -135,10 +136,9 @@ func (s *beaconBlockSync) updateEventFeed() {
 		case he < fe:
 			return
 		case he == fe+1:
-			parent, ok := s.recentBlocks.Get(head.Header.ParentRoot)
+			parent, ok := s.recentBlocks.Get(optimistic.Attested.ParentRoot)
 			if !ok || parent.Slot()/params.EpochLength == fe {
 				return // head is at first slot of next epoch, wait for finality update
-				//TODO: try to fetch finality update directly if subscription does not deliver
 			}
 		}
 	}
@@ -156,7 +156,7 @@ func (s *beaconBlockSync) updateEventFeed() {
 		return
 	}
 	s.chainHeadFeed.Send(types.ChainHeadEvent{
-		BeaconHead: head.Header,
+		BeaconHead: optimistic.Attested.Header,
 		Block:      execBlock,
 		Finalized:  finalizedHash,
 	})
diff --git a/beacon/blsync/block_sync_test.go b/beacon/blsync/block_sync_test.go
index 0525e95a89..3d3b9e5e8d 100644
--- a/beacon/blsync/block_sync_test.go
+++ b/beacon/blsync/block_sync_test.go
@@ -140,8 +140,12 @@ func (h *testHeadTracker) PrefetchHead() types.HeadInfo {
 	return h.prefetch
 }
 
-func (h *testHeadTracker) ValidatedHead() (types.SignedHeader, bool) {
-	return h.validated, h.validated.Header != (types.Header{})
+func (h *testHeadTracker) ValidatedOptimistic() (types.OptimisticUpdate, bool) {
+	return types.OptimisticUpdate{
+		Attested:      types.HeaderWithExecProof{Header: h.validated.Header},
+		Signature:     h.validated.Signature,
+		SignatureSlot: h.validated.SignatureSlot,
+	}, h.validated.Header != (types.Header{})
 }
 
 // TODO add test case for finality
diff --git a/beacon/blsync/engineclient.go b/beacon/blsync/engineclient.go
index 5a2d292a7d..97ef6f5cb8 100644
--- a/beacon/blsync/engineclient.go
+++ b/beacon/blsync/engineclient.go
@@ -62,6 +62,7 @@ func (ec *engineClient) updateLoop(headCh <-chan types.ChainHeadEvent) {
 	for {
 		select {
 		case <-ec.rootCtx.Done():
+			log.Debug("Stopping engine API update loop")
 			return
 
 		case event := <-headCh:
@@ -73,12 +74,14 @@ func (ec *engineClient) updateLoop(headCh <-chan types.ChainHeadEvent) {
 			fork := ec.config.ForkAtEpoch(event.BeaconHead.Epoch())
 			forkName := strings.ToLower(fork.Name)
 
+			log.Debug("Calling NewPayload", "number", event.Block.NumberU64(), "hash", event.Block.Hash())
 			if status, err := ec.callNewPayload(forkName, event); err == nil {
 				log.Info("Successful NewPayload", "number", event.Block.NumberU64(), "hash", event.Block.Hash(), "status", status)
 			} else {
 				log.Error("Failed NewPayload", "number", event.Block.NumberU64(), "hash", event.Block.Hash(), "error", err)
 			}
 
+			log.Debug("Calling ForkchoiceUpdated", "head", event.Block.Hash())
 			if status, err := ec.callForkchoiceUpdated(forkName, event); err == nil {
 				log.Info("Successful ForkchoiceUpdated", "head", event.Block.Hash(), "status", status)
 			} else {
diff --git a/beacon/light/api/api_server.go b/beacon/light/api/api_server.go
index 4b885cb8e1..2579854d82 100755
--- a/beacon/light/api/api_server.go
+++ b/beacon/light/api/api_server.go
@@ -46,13 +46,13 @@ func (s *ApiServer) Subscribe(eventCallback func(event request.Event)) {
 			log.Debug("New head received", "slot", slot, "blockRoot", blockRoot)
 			eventCallback(request.Event{Type: sync.EvNewHead, Data: types.HeadInfo{Slot: slot, BlockRoot: blockRoot}})
 		},
-		OnSignedHead: func(head types.SignedHeader) {
-			log.Debug("New signed head received", "slot", head.Header.Slot, "blockRoot", head.Header.Hash(), "signerCount", head.Signature.SignerCount())
-			eventCallback(request.Event{Type: sync.EvNewSignedHead, Data: head})
+		OnOptimistic: func(update types.OptimisticUpdate) {
+			log.Debug("New optimistic update received", "slot", update.Attested.Slot, "blockRoot", update.Attested.Hash(), "signerCount", update.Signature.SignerCount())
+			eventCallback(request.Event{Type: sync.EvNewOptimisticUpdate, Data: update})
 		},
-		OnFinality: func(head types.FinalityUpdate) {
-			log.Debug("New finality update received", "slot", head.Attested.Slot, "blockRoot", head.Attested.Hash(), "signerCount", head.Signature.SignerCount())
-			eventCallback(request.Event{Type: sync.EvNewFinalityUpdate, Data: head})
+		OnFinality: func(update types.FinalityUpdate) {
+			log.Debug("New finality update received", "slot", update.Attested.Slot, "blockRoot", update.Attested.Hash(), "signerCount", update.Signature.SignerCount())
+			eventCallback(request.Event{Type: sync.EvNewFinalityUpdate, Data: update})
 		},
 		OnError: func(err error) {
 			log.Warn("Head event stream error", "err", err)
@@ -83,6 +83,9 @@ func (s *ApiServer) SendRequest(id request.ID, req request.Request) {
 		case sync.ReqBeaconBlock:
 			log.Debug("Beacon API: requesting block", "reqid", id, "hash", common.Hash(data))
 			resp, err = s.api.GetBeaconBlock(common.Hash(data))
+		case sync.ReqFinality:
+			log.Debug("Beacon API: requesting finality update")
+			resp, err = s.api.GetFinalityUpdate()
 		default:
 		}
 
@@ -90,6 +93,7 @@ func (s *ApiServer) SendRequest(id request.ID, req request.Request) {
 			log.Warn("Beacon API request failed", "type", reflect.TypeOf(req), "reqid", id, "err", err)
 			s.eventCallback(request.Event{Type: request.EvFail, Data: request.RequestResponse{ID: id, Request: req}})
 		} else {
+			log.Debug("Beacon API request answered", "type", reflect.TypeOf(req), "reqid", id)
 			s.eventCallback(request.Event{Type: request.EvResponse, Data: request.RequestResponse{ID: id, Request: req, Response: resp}})
 		}
 	}()
diff --git a/beacon/light/api/light_api.go b/beacon/light/api/light_api.go
index 6892407caf..903db57344 100755
--- a/beacon/light/api/light_api.go
+++ b/beacon/light/api/light_api.go
@@ -32,6 +32,7 @@ import (
 	"github.com/ethereum/go-ethereum/beacon/types"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/log"
 )
 
 var (
@@ -184,46 +185,56 @@ func (api *BeaconLightApi) GetBestUpdatesAndCommittees(firstPeriod, count uint64
 	return updates, committees, nil
 }
 
-// GetOptimisticHeadUpdate fetches a signed header based on the latest available
-// optimistic update. Note that the signature should be verified by the caller
-// as its validity depends on the update chain.
+// GetOptimisticUpdate fetches the latest available optimistic update.
+// Note that the signature should be verified by the caller as its validity
+// depends on the update chain.
 //
 // See data structure definition here:
 // https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/light-client/sync-protocol.md#lightclientoptimisticupdate
-func (api *BeaconLightApi) GetOptimisticHeadUpdate() (types.SignedHeader, error) {
+func (api *BeaconLightApi) GetOptimisticUpdate() (types.OptimisticUpdate, error) {
 	resp, err := api.httpGet("/eth/v1/beacon/light_client/optimistic_update")
 	if err != nil {
-		return types.SignedHeader{}, err
+		return types.OptimisticUpdate{}, err
 	}
-	return decodeOptimisticHeadUpdate(resp)
+	return decodeOptimisticUpdate(resp)
 }
 
-func decodeOptimisticHeadUpdate(enc []byte) (types.SignedHeader, error) {
+func decodeOptimisticUpdate(enc []byte) (types.OptimisticUpdate, error) {
 	var data struct {
-		Data struct {
-			Header        jsonBeaconHeader    `json:"attested_header"`
-			Aggregate     types.SyncAggregate `json:"sync_aggregate"`
-			SignatureSlot common.Decimal      `json:"signature_slot"`
+		Version string
+		Data    struct {
+			Attested      jsonHeaderWithExecProof `json:"attested_header"`
+			Aggregate     types.SyncAggregate     `json:"sync_aggregate"`
+			SignatureSlot common.Decimal          `json:"signature_slot"`
 		} `json:"data"`
 	}
 	if err := json.Unmarshal(enc, &data); err != nil {
-		return types.SignedHeader{}, err
+		return types.OptimisticUpdate{}, err
 	}
-	if data.Data.Header.Beacon.StateRoot == (common.Hash{}) {
+	// Decode the execution payload headers.
+	attestedExecHeader, err := types.ExecutionHeaderFromJSON(data.Version, data.Data.Attested.Execution)
+	if err != nil {
+		return types.OptimisticUpdate{}, fmt.Errorf("invalid attested header: %v", err)
+	}
+	if data.Data.Attested.Beacon.StateRoot == (common.Hash{}) {
 		// workaround for different event encoding format in Lodestar
 		if err := json.Unmarshal(enc, &data.Data); err != nil {
-			return types.SignedHeader{}, err
+			return types.OptimisticUpdate{}, err
 		}
 	}
 
 	if len(data.Data.Aggregate.Signers) != params.SyncCommitteeBitmaskSize {
-		return types.SignedHeader{}, errors.New("invalid sync_committee_bits length")
+		return types.OptimisticUpdate{}, errors.New("invalid sync_committee_bits length")
 	}
 	if len(data.Data.Aggregate.Signature) != params.BLSSignatureSize {
-		return types.SignedHeader{}, errors.New("invalid sync_committee_signature length")
+		return types.OptimisticUpdate{}, errors.New("invalid sync_committee_signature length")
 	}
-	return types.SignedHeader{
-		Header:        data.Data.Header.Beacon,
+	return types.OptimisticUpdate{
+		Attested: types.HeaderWithExecProof{
+			Header:        data.Data.Attested.Beacon,
+			PayloadHeader: attestedExecHeader,
+			PayloadBranch: data.Data.Attested.ExecutionBranch,
+		},
 		Signature:     data.Data.Aggregate,
 		SignatureSlot: uint64(data.Data.SignatureSlot),
 	}, nil
@@ -411,7 +422,7 @@ func decodeHeadEvent(enc []byte) (uint64, common.Hash, error) {
 
 type HeadEventListener struct {
 	OnNewHead    func(slot uint64, blockRoot common.Hash)
-	OnSignedHead func(head types.SignedHeader)
+	OnOptimistic func(head types.OptimisticUpdate)
 	OnFinality   func(head types.FinalityUpdate)
 	OnError      func(err error)
 }
@@ -449,21 +460,35 @@ func (api *BeaconLightApi) StartHeadListener(listener HeadEventListener) func()
 		defer wg.Done()
 
 		// Request initial data.
+		log.Trace("Requesting initial head header")
 		if head, _, _, err := api.GetHeader(common.Hash{}); err == nil {
+			log.Trace("Retrieved initial head header", "slot", head.Slot, "hash", head.Hash())
 			listener.OnNewHead(head.Slot, head.Hash())
+		} else {
+			log.Debug("Failed to retrieve initial head header", "error", err)
 		}
-		if signedHead, err := api.GetOptimisticHeadUpdate(); err == nil {
-			listener.OnSignedHead(signedHead)
+		log.Trace("Requesting initial optimistic update")
+		if optimisticUpdate, err := api.GetOptimisticUpdate(); err == nil {
+			log.Trace("Retrieved initial optimistic update", "slot", optimisticUpdate.Attested.Slot, "hash", optimisticUpdate.Attested.Hash())
+			listener.OnOptimistic(optimisticUpdate)
+		} else {
+			log.Debug("Failed to retrieve initial optimistic update", "error", err)
 		}
+		log.Trace("Requesting initial finality update")
 		if finalityUpdate, err := api.GetFinalityUpdate(); err == nil {
+			log.Trace("Retrieved initial finality update", "slot", finalityUpdate.Finalized.Slot, "hash", finalityUpdate.Finalized.Hash())
 			listener.OnFinality(finalityUpdate)
+		} else {
+			log.Debug("Failed to retrieve initial finality update", "error", err)
 		}
 
+		log.Trace("Starting event stream processing loop")
 		// Receive the stream.
 		var stream *eventsource.Stream
 		select {
 		case stream = <-streamCh:
 		case <-ctx.Done():
+			log.Trace("Stopping event stream processing loop")
 			return
 		}
 
@@ -474,8 +499,10 @@ func (api *BeaconLightApi) StartHeadListener(listener HeadEventListener) func()
 
 			case event, ok := <-stream.Events:
 				if !ok {
+					log.Trace("Event stream closed")
 					return
 				}
+				log.Trace("New event received from event stream", "type", event.Event())
 				switch event.Event() {
 				case "head":
 					slot, blockRoot, err := decodeHeadEvent([]byte(event.Data()))
@@ -485,9 +512,9 @@ func (api *BeaconLightApi) StartHeadListener(listener HeadEventListener) func()
 						listener.OnError(fmt.Errorf("error decoding head event: %v", err))
 					}
 				case "light_client_optimistic_update":
-					signedHead, err := decodeOptimisticHeadUpdate([]byte(event.Data()))
+					optimisticUpdate, err := decodeOptimisticUpdate([]byte(event.Data()))
 					if err == nil {
-						listener.OnSignedHead(signedHead)
+						listener.OnOptimistic(optimisticUpdate)
 					} else {
 						listener.OnError(fmt.Errorf("error decoding optimistic update event: %v", err))
 					}
@@ -521,7 +548,8 @@ func (api *BeaconLightApi) StartHeadListener(listener HeadEventListener) func()
 // established. It can only return nil when the context is canceled.
 func (api *BeaconLightApi) startEventStream(ctx context.Context, listener *HeadEventListener) *eventsource.Stream {
 	for retry := true; retry; retry = ctxSleep(ctx, 5*time.Second) {
-		path := "/eth/v1/events?topics=head&topics=light_client_optimistic_update&topics=light_client_finality_update"
+		path := "/eth/v1/events?topics=head&topics=light_client_finality_update&topics=light_client_optimistic_update"
+		log.Trace("Sending event subscription request")
 		req, err := http.NewRequestWithContext(ctx, "GET", api.url+path, nil)
 		if err != nil {
 			listener.OnError(fmt.Errorf("error creating event subscription request: %v", err))
@@ -535,6 +563,7 @@ func (api *BeaconLightApi) startEventStream(ctx context.Context, listener *HeadE
 			listener.OnError(fmt.Errorf("error creating event subscription: %v", err))
 			continue
 		}
+		log.Trace("Successfully created event stream")
 		return stream
 	}
 	return nil
diff --git a/beacon/light/head_tracker.go b/beacon/light/head_tracker.go
index 6036322f01..7ef93fecce 100644
--- a/beacon/light/head_tracker.go
+++ b/beacon/light/head_tracker.go
@@ -29,15 +29,15 @@ import (
 // which is the (not necessarily validated) head announced by the majority of
 // servers.
 type HeadTracker struct {
-	lock              sync.RWMutex
-	committeeChain    *CommitteeChain
-	minSignerCount    int
-	signedHead        types.SignedHeader
-	hasSignedHead     bool
-	finalityUpdate    types.FinalityUpdate
-	hasFinalityUpdate bool
-	prefetchHead      types.HeadInfo
-	changeCounter     uint64
+	lock                sync.RWMutex
+	committeeChain      *CommitteeChain
+	minSignerCount      int
+	optimisticUpdate    types.OptimisticUpdate
+	hasOptimisticUpdate bool
+	finalityUpdate      types.FinalityUpdate
+	hasFinalityUpdate   bool
+	prefetchHead        types.HeadInfo
+	changeCounter       uint64
 }
 
 // NewHeadTracker creates a new HeadTracker.
@@ -48,15 +48,15 @@ func NewHeadTracker(committeeChain *CommitteeChain, minSignerCount int) *HeadTra
 	}
 }
 
-// ValidatedHead returns the latest validated head.
-func (h *HeadTracker) ValidatedHead() (types.SignedHeader, bool) {
+// ValidatedOptimistic returns the latest validated optimistic update.
+func (h *HeadTracker) ValidatedOptimistic() (types.OptimisticUpdate, bool) {
 	h.lock.RLock()
 	defer h.lock.RUnlock()
 
-	return h.signedHead, h.hasSignedHead
+	return h.optimisticUpdate, h.hasOptimisticUpdate
 }
 
-// ValidatedFinality returns the latest validated finality.
+// ValidatedFinality returns the latest validated finality update.
 func (h *HeadTracker) ValidatedFinality() (types.FinalityUpdate, bool) {
 	h.lock.RLock()
 	defer h.lock.RUnlock()
@@ -64,26 +64,36 @@ func (h *HeadTracker) ValidatedFinality() (types.FinalityUpdate, bool) {
 	return h.finalityUpdate, h.hasFinalityUpdate
 }
 
-// ValidateHead validates the given signed head. If the head is successfully validated
-// and it is better than the old validated head (higher slot or same slot and more
-// signers) then ValidatedHead is updated. The boolean return flag signals if
-// ValidatedHead has been changed.
-func (h *HeadTracker) ValidateHead(head types.SignedHeader) (bool, error) {
+// ValidateOptimistic validates the given optimistic update. If the update is
+// successfully validated and it is better than the old validated update (higher
+// slot or same slot and more signers) then ValidatedOptimistic is updated.
+// The boolean return flag signals if ValidatedOptimistic has been changed.
+func (h *HeadTracker) ValidateOptimistic(update types.OptimisticUpdate) (bool, error) {
 	h.lock.Lock()
 	defer h.lock.Unlock()
 
-	replace, err := h.validate(head, h.signedHead)
+	if err := update.Validate(); err != nil {
+		return false, err
+	}
+	replace, err := h.validate(update.SignedHeader(), h.optimisticUpdate.SignedHeader())
 	if replace {
-		h.signedHead, h.hasSignedHead = head, true
+		h.optimisticUpdate, h.hasOptimisticUpdate = update, true
 		h.changeCounter++
 	}
 	return replace, err
 }
 
+// ValidateFinality validates the given finality update. If the update is
+// successfully validated and it is better than the old validated update (higher
+// slot or same slot and more signers) then ValidatedFinality is updated.
+// The boolean return flag signals if ValidatedFinality has been changed.
 func (h *HeadTracker) ValidateFinality(update types.FinalityUpdate) (bool, error) {
 	h.lock.Lock()
 	defer h.lock.Unlock()
 
+	if err := update.Validate(); err != nil {
+		return false, err
+	}
 	replace, err := h.validate(update.SignedHeader(), h.finalityUpdate.SignedHeader())
 	if replace {
 		h.finalityUpdate, h.hasFinalityUpdate = update, true
@@ -142,6 +152,7 @@ func (h *HeadTracker) SetPrefetchHead(head types.HeadInfo) {
 	h.changeCounter++
 }
 
+// ChangeCounter implements request.targetData
 func (h *HeadTracker) ChangeCounter() uint64 {
 	h.lock.RLock()
 	defer h.lock.RUnlock()
diff --git a/beacon/light/sync/head_sync.go b/beacon/light/sync/head_sync.go
index 5ccc2e18a2..dd05d39588 100644
--- a/beacon/light/sync/head_sync.go
+++ b/beacon/light/sync/head_sync.go
@@ -19,11 +19,13 @@ package sync
 import (
 	"github.com/ethereum/go-ethereum/beacon/light/request"
 	"github.com/ethereum/go-ethereum/beacon/types"
+	"github.com/ethereum/go-ethereum/log"
 )
 
 type headTracker interface {
-	ValidateHead(head types.SignedHeader) (bool, error)
+	ValidateOptimistic(update types.OptimisticUpdate) (bool, error)
 	ValidateFinality(head types.FinalityUpdate) (bool, error)
+	ValidatedFinality() (types.FinalityUpdate, bool)
 	SetPrefetchHead(head types.HeadInfo)
 }
 
@@ -33,16 +35,17 @@ type headTracker interface {
 // It can also postpone the validation of the latest announced signed head
 // until the committee chain is synced up to at least the required period.
 type HeadSync struct {
-	headTracker         headTracker
-	chain               committeeChain
-	nextSyncPeriod      uint64
-	chainInit           bool
-	unvalidatedHeads    map[request.Server]types.SignedHeader
-	unvalidatedFinality map[request.Server]types.FinalityUpdate
-	serverHeads         map[request.Server]types.HeadInfo
-	headServerCount     map[types.HeadInfo]headServerCount
-	headCounter         uint64
-	prefetchHead        types.HeadInfo
+	headTracker           headTracker
+	chain                 committeeChain
+	nextSyncPeriod        uint64
+	chainInit             bool
+	unvalidatedOptimistic map[request.Server]types.OptimisticUpdate
+	unvalidatedFinality   map[request.Server]types.FinalityUpdate
+	serverHeads           map[request.Server]types.HeadInfo
+	reqFinalityEpoch      map[request.Server]uint64 // next epoch to request finality update
+	headServerCount       map[types.HeadInfo]headServerCount
+	headCounter           uint64
+	prefetchHead          types.HeadInfo
 }
 
 // headServerCount is associated with most recently seen head infos; it counts
@@ -57,75 +60,98 @@ type headServerCount struct {
 // NewHeadSync creates a new HeadSync.
 func NewHeadSync(headTracker headTracker, chain committeeChain) *HeadSync {
 	s := &HeadSync{
-		headTracker:         headTracker,
-		chain:               chain,
-		unvalidatedHeads:    make(map[request.Server]types.SignedHeader),
-		unvalidatedFinality: make(map[request.Server]types.FinalityUpdate),
-		serverHeads:         make(map[request.Server]types.HeadInfo),
-		headServerCount:     make(map[types.HeadInfo]headServerCount),
+		headTracker:           headTracker,
+		chain:                 chain,
+		unvalidatedOptimistic: make(map[request.Server]types.OptimisticUpdate),
+		unvalidatedFinality:   make(map[request.Server]types.FinalityUpdate),
+		serverHeads:           make(map[request.Server]types.HeadInfo),
+		headServerCount:       make(map[types.HeadInfo]headServerCount),
+		reqFinalityEpoch:      make(map[request.Server]uint64),
 	}
 	return s
 }
 
 // Process implements request.Module.
 func (s *HeadSync) Process(requester request.Requester, events []request.Event) {
+	nextPeriod, chainInit := s.chain.NextSyncPeriod()
+	if nextPeriod != s.nextSyncPeriod || chainInit != s.chainInit {
+		s.nextSyncPeriod, s.chainInit = nextPeriod, chainInit
+		s.processUnvalidatedUpdates()
+	}
+
 	for _, event := range events {
 		switch event.Type {
 		case EvNewHead:
 			s.setServerHead(event.Server, event.Data.(types.HeadInfo))
-		case EvNewSignedHead:
-			s.newSignedHead(event.Server, event.Data.(types.SignedHeader))
+		case EvNewOptimisticUpdate:
+			update := event.Data.(types.OptimisticUpdate)
+			s.newOptimisticUpdate(event.Server, update)
+			epoch := update.Attested.Epoch()
+			if epoch < s.reqFinalityEpoch[event.Server] {
+				continue
+			}
+			if finality, ok := s.headTracker.ValidatedFinality(); ok && finality.Attested.Header.Epoch() >= epoch {
+				continue
+			}
+			requester.Send(event.Server, ReqFinality{})
+			s.reqFinalityEpoch[event.Server] = epoch + 1
 		case EvNewFinalityUpdate:
 			s.newFinalityUpdate(event.Server, event.Data.(types.FinalityUpdate))
+		case request.EvResponse:
+			_, _, resp := event.RequestInfo()
+			s.newFinalityUpdate(event.Server, resp.(types.FinalityUpdate))
 		case request.EvUnregistered:
 			s.setServerHead(event.Server, types.HeadInfo{})
 			delete(s.serverHeads, event.Server)
-			delete(s.unvalidatedHeads, event.Server)
+			delete(s.unvalidatedOptimistic, event.Server)
+			delete(s.unvalidatedFinality, event.Server)
 		}
 	}
-
-	nextPeriod, chainInit := s.chain.NextSyncPeriod()
-	if nextPeriod != s.nextSyncPeriod || chainInit != s.chainInit {
-		s.nextSyncPeriod, s.chainInit = nextPeriod, chainInit
-		s.processUnvalidated()
-	}
 }
 
-// newSignedHead handles received signed head; either validates it if the chain
-// is properly synced or stores it for further validation.
-func (s *HeadSync) newSignedHead(server request.Server, signedHead types.SignedHeader) {
-	if !s.chainInit || types.SyncPeriod(signedHead.SignatureSlot) > s.nextSyncPeriod {
-		s.unvalidatedHeads[server] = signedHead
+// newOptimisticUpdate handles received optimistic update; either validates it if
+// the chain is properly synced or stores it for further validation.
+func (s *HeadSync) newOptimisticUpdate(server request.Server, optimisticUpdate types.OptimisticUpdate) {
+	if !s.chainInit || types.SyncPeriod(optimisticUpdate.SignatureSlot) > s.nextSyncPeriod {
+		s.unvalidatedOptimistic[server] = optimisticUpdate
 		return
 	}
-	s.headTracker.ValidateHead(signedHead)
+	if _, err := s.headTracker.ValidateOptimistic(optimisticUpdate); err != nil {
+		log.Debug("Error validating optimistic update", "error", err)
+	}
 }
 
-// newFinalityUpdate handles received finality update; either validates it if the chain
-// is properly synced or stores it for further validation.
+// newFinalityUpdate handles received finality update; either validates it if
+// the chain is properly synced or stores it for further validation.
 func (s *HeadSync) newFinalityUpdate(server request.Server, finalityUpdate types.FinalityUpdate) {
 	if !s.chainInit || types.SyncPeriod(finalityUpdate.SignatureSlot) > s.nextSyncPeriod {
 		s.unvalidatedFinality[server] = finalityUpdate
 		return
 	}
-	s.headTracker.ValidateFinality(finalityUpdate)
+	if _, err := s.headTracker.ValidateFinality(finalityUpdate); err != nil {
+		log.Debug("Error validating finality update", "error", err)
+	}
 }
 
-// processUnvalidated iterates the list of unvalidated heads and validates
+// processUnvalidatedUpdates iterates the list of unvalidated updates and validates
 // those which can be validated.
-func (s *HeadSync) processUnvalidated() {
+func (s *HeadSync) processUnvalidatedUpdates() {
 	if !s.chainInit {
 		return
 	}
-	for server, signedHead := range s.unvalidatedHeads {
-		if types.SyncPeriod(signedHead.SignatureSlot) <= s.nextSyncPeriod {
-			s.headTracker.ValidateHead(signedHead)
-			delete(s.unvalidatedHeads, server)
+	for server, optimisticUpdate := range s.unvalidatedOptimistic {
+		if types.SyncPeriod(optimisticUpdate.SignatureSlot) <= s.nextSyncPeriod {
+			if _, err := s.headTracker.ValidateOptimistic(optimisticUpdate); err != nil {
+				log.Debug("Error validating deferred optimistic update", "error", err)
+			}
+			delete(s.unvalidatedOptimistic, server)
 		}
 	}
 	for server, finalityUpdate := range s.unvalidatedFinality {
 		if types.SyncPeriod(finalityUpdate.SignatureSlot) <= s.nextSyncPeriod {
-			s.headTracker.ValidateFinality(finalityUpdate)
+			if _, err := s.headTracker.ValidateFinality(finalityUpdate); err != nil {
+				log.Debug("Error validating deferred finality update", "error", err)
+			}
 			delete(s.unvalidatedFinality, server)
 		}
 	}
diff --git a/beacon/light/sync/head_sync_test.go b/beacon/light/sync/head_sync_test.go
index a2870b2732..cd7dacf7fe 100644
--- a/beacon/light/sync/head_sync_test.go
+++ b/beacon/light/sync/head_sync_test.go
@@ -19,6 +19,7 @@ package sync
 import (
 	"testing"
 
+	"github.com/ethereum/go-ethereum/beacon/light/request"
 	"github.com/ethereum/go-ethereum/beacon/types"
 	"github.com/ethereum/go-ethereum/common"
 )
@@ -28,6 +29,7 @@ var (
 	testServer2 = testServer("testServer2")
 	testServer3 = testServer("testServer3")
 	testServer4 = testServer("testServer4")
+	testServer5 = testServer("testServer5")
 
 	testHead0 = types.HeadInfo{}
 	testHead1 = types.HeadInfo{Slot: 123, BlockRoot: common.Hash{1}}
@@ -35,13 +37,21 @@ var (
 	testHead3 = types.HeadInfo{Slot: 124, BlockRoot: common.Hash{3}}
 	testHead4 = types.HeadInfo{Slot: 125, BlockRoot: common.Hash{4}}
 
-	testSHead1 = types.SignedHeader{SignatureSlot: 0x0124, Header: types.Header{Slot: 0x0123, StateRoot: common.Hash{1}}}
-	testSHead2 = types.SignedHeader{SignatureSlot: 0x2010, Header: types.Header{Slot: 0x200e, StateRoot: common.Hash{2}}}
-	// testSHead3 is at the end of period 1 but signed in period 2
-	testSHead3 = types.SignedHeader{SignatureSlot: 0x4000, Header: types.Header{Slot: 0x3fff, StateRoot: common.Hash{3}}}
-	testSHead4 = types.SignedHeader{SignatureSlot: 0x6444, Header: types.Header{Slot: 0x6443, StateRoot: common.Hash{4}}}
+	testOptUpdate1 = types.OptimisticUpdate{SignatureSlot: 0x0124, Attested: types.HeaderWithExecProof{Header: types.Header{Slot: 0x0123, StateRoot: common.Hash{1}}}}
+	testOptUpdate2 = types.OptimisticUpdate{SignatureSlot: 0x2010, Attested: types.HeaderWithExecProof{Header: types.Header{Slot: 0x200e, StateRoot: common.Hash{2}}}}
+	// testOptUpdate3 is at the end of period 1 but signed in period 2
+	testOptUpdate3 = types.OptimisticUpdate{SignatureSlot: 0x4000, Attested: types.HeaderWithExecProof{Header: types.Header{Slot: 0x3fff, StateRoot: common.Hash{3}}}}
+	testOptUpdate4 = types.OptimisticUpdate{SignatureSlot: 0x6444, Attested: types.HeaderWithExecProof{Header: types.Header{Slot: 0x6443, StateRoot: common.Hash{4}}}}
 )
 
+func finality(opt types.OptimisticUpdate) types.FinalityUpdate {
+	return types.FinalityUpdate{
+		SignatureSlot: opt.SignatureSlot,
+		Attested:      opt.Attested,
+		Finalized:     types.HeaderWithExecProof{Header: types.Header{Slot: (opt.Attested.Header.Slot - 64) & uint64(0xffffffffffffffe0)}},
+	}
+}
+
 type testServer string
 
 func (t testServer) Name() string {
@@ -57,50 +67,66 @@ func TestValidatedHead(t *testing.T) {
 	ht.ExpValidated(t, 0, nil)
 
 	ts.AddServer(testServer1, 1)
-	ts.ServerEvent(EvNewSignedHead, testServer1, testSHead1)
-	ts.Run(1)
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer1, testOptUpdate1)
+	ts.Run(1, testServer1, ReqFinality{})
 	// announced head should be queued because of uninitialized chain
 	ht.ExpValidated(t, 1, nil)
 
 	chain.SetNextSyncPeriod(0) // initialize chain
 	ts.Run(2)
 	// expect previously queued head to be validated
-	ht.ExpValidated(t, 2, []types.SignedHeader{testSHead1})
+	ht.ExpValidated(t, 2, []types.OptimisticUpdate{testOptUpdate1})
 
 	chain.SetNextSyncPeriod(1)
-	ts.ServerEvent(EvNewSignedHead, testServer1, testSHead2)
+	ts.ServerEvent(EvNewFinalityUpdate, testServer1, finality(testOptUpdate2))
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer1, testOptUpdate2)
 	ts.AddServer(testServer2, 1)
-	ts.ServerEvent(EvNewSignedHead, testServer2, testSHead2)
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer2, testOptUpdate2)
 	ts.Run(3)
 	// expect both head announcements to be validated instantly
-	ht.ExpValidated(t, 3, []types.SignedHeader{testSHead2, testSHead2})
+	ht.ExpValidated(t, 3, []types.OptimisticUpdate{testOptUpdate2, testOptUpdate2})
 
-	ts.ServerEvent(EvNewSignedHead, testServer1, testSHead3)
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer1, testOptUpdate3)
 	ts.AddServer(testServer3, 1)
-	ts.ServerEvent(EvNewSignedHead, testServer3, testSHead4)
-	ts.Run(4)
-	// future period announced heads should be queued
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer3, testOptUpdate4)
+	// finality should be requested from both servers
+	ts.Run(4, testServer1, ReqFinality{}, testServer3, ReqFinality{})
+	// future period annonced heads should be queued
 	ht.ExpValidated(t, 4, nil)
 
 	chain.SetNextSyncPeriod(2)
 	ts.Run(5)
-	// testSHead3 can be validated now but not testSHead4
-	ht.ExpValidated(t, 5, []types.SignedHeader{testSHead3})
+	// testOptUpdate3 can be validated now but not testOptUpdate4
+	ht.ExpValidated(t, 5, []types.OptimisticUpdate{testOptUpdate3})
+
+	ts.AddServer(testServer4, 1)
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer4, testOptUpdate3)
+	// new server joined with recent optimistic update but still no finality; should be requested
+	ts.Run(6, testServer4, ReqFinality{})
+	ht.ExpValidated(t, 6, []types.OptimisticUpdate{testOptUpdate3})
+
+	ts.AddServer(testServer5, 1)
+	ts.RequestEvent(request.EvResponse, ts.Request(6, 1), finality(testOptUpdate3))
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer5, testOptUpdate3)
+	// finality update request answered; new server should not be requested
+	ts.Run(7)
+	ht.ExpValidated(t, 7, []types.OptimisticUpdate{testOptUpdate3})
 
 	// server 3 disconnected without proving period 3, its announced head should be dropped
 	ts.RemoveServer(testServer3)
-	ts.Run(6)
-	ht.ExpValidated(t, 6, nil)
+	ts.Run(8)
+	ht.ExpValidated(t, 8, nil)
 
 	chain.SetNextSyncPeriod(3)
-	ts.Run(7)
-	// testSHead4 could be validated now but it's not queued by any registered server
-	ht.ExpValidated(t, 7, nil)
+	ts.Run(9)
+	// testOptUpdate4 could be validated now but it's not queued by any registered server
+	ht.ExpValidated(t, 9, nil)
 
-	ts.ServerEvent(EvNewSignedHead, testServer2, testSHead4)
-	ts.Run(8)
-	// now testSHead4 should be validated
-	ht.ExpValidated(t, 8, []types.SignedHeader{testSHead4})
+	ts.ServerEvent(EvNewFinalityUpdate, testServer2, finality(testOptUpdate4))
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer2, testOptUpdate4)
+	ts.Run(10)
+	// now testOptUpdate4 should be validated
+	ht.ExpValidated(t, 10, []types.OptimisticUpdate{testOptUpdate4})
 }
 
 func TestPrefetchHead(t *testing.T) {
diff --git a/beacon/light/sync/test_helpers.go b/beacon/light/sync/test_helpers.go
index 9f57ceebe4..cfca8ad8a4 100644
--- a/beacon/light/sync/test_helpers.go
+++ b/beacon/light/sync/test_helpers.go
@@ -212,32 +212,37 @@ func (tc *TestCommitteeChain) ExpNextSyncPeriod(t *testing.T, expNsp uint64) {
 
 type TestHeadTracker struct {
 	phead     types.HeadInfo
-	validated []types.SignedHeader
+	validated []types.OptimisticUpdate
+	finality  types.FinalityUpdate
 }
 
-func (ht *TestHeadTracker) ValidateHead(head types.SignedHeader) (bool, error) {
-	ht.validated = append(ht.validated, head)
+func (ht *TestHeadTracker) ValidateOptimistic(update types.OptimisticUpdate) (bool, error) {
+	ht.validated = append(ht.validated, update)
 	return true, nil
 }
 
-// TODO add test case for finality
-func (ht *TestHeadTracker) ValidateFinality(head types.FinalityUpdate) (bool, error) {
+func (ht *TestHeadTracker) ValidateFinality(update types.FinalityUpdate) (bool, error) {
+	ht.finality = update
 	return true, nil
 }
 
-func (ht *TestHeadTracker) ExpValidated(t *testing.T, tci int, expHeads []types.SignedHeader) {
+func (ht *TestHeadTracker) ValidatedFinality() (types.FinalityUpdate, bool) {
+	return ht.finality, ht.finality.Attested.Header != (types.Header{})
+}
+
+func (ht *TestHeadTracker) ExpValidated(t *testing.T, tci int, expHeads []types.OptimisticUpdate) {
 	for i, expHead := range expHeads {
 		if i >= len(ht.validated) {
-			t.Errorf("Missing validated head in test case #%d index #%d (expected {slot %d blockRoot %x}, got none)", tci, i, expHead.Header.Slot, expHead.Header.Hash())
+			t.Errorf("Missing validated head in test case #%d index #%d (expected {slot %d blockRoot %x}, got none)", tci, i, expHead.Attested.Header.Slot, expHead.Attested.Header.Hash())
 			continue
 		}
-		if ht.validated[i] != expHead {
-			vhead := ht.validated[i].Header
-			t.Errorf("Wrong validated head in test case #%d index #%d (expected {slot %d blockRoot %x}, got {slot %d blockRoot %x})", tci, i, expHead.Header.Slot, expHead.Header.Hash(), vhead.Slot, vhead.Hash())
+		if !reflect.DeepEqual(ht.validated[i], expHead) {
+			vhead := ht.validated[i].Attested.Header
+			t.Errorf("Wrong validated head in test case #%d index #%d (expected {slot %d blockRoot %x}, got {slot %d blockRoot %x})", tci, i, expHead.Attested.Header.Slot, expHead.Attested.Header.Hash(), vhead.Slot, vhead.Hash())
 		}
 	}
 	for i := len(expHeads); i < len(ht.validated); i++ {
-		vhead := ht.validated[i].Header
+		vhead := ht.validated[i].Attested.Header
 		t.Errorf("Unexpected validated head in test case #%d index #%d (expected none, got {slot %d blockRoot %x})", tci, i, vhead.Slot, vhead.Hash())
 	}
 	ht.validated = nil
diff --git a/beacon/light/sync/types.go b/beacon/light/sync/types.go
index 8aa4c95f46..97a3fb2111 100644
--- a/beacon/light/sync/types.go
+++ b/beacon/light/sync/types.go
@@ -23,9 +23,9 @@ import (
 )
 
 var (
-	EvNewHead           = &request.EventType{Name: "newHead"}           // data: types.HeadInfo
-	EvNewSignedHead     = &request.EventType{Name: "newSignedHead"}     // data: types.SignedHeader
-	EvNewFinalityUpdate = &request.EventType{Name: "newFinalityUpdate"} // data: types.FinalityUpdate
+	EvNewHead             = &request.EventType{Name: "newHead"}             // data: types.HeadInfo
+	EvNewOptimisticUpdate = &request.EventType{Name: "newOptimisticUpdate"} // data: types.OptimisticUpdate
+	EvNewFinalityUpdate   = &request.EventType{Name: "newFinalityUpdate"}   // data: types.FinalityUpdate
 )
 
 type (
@@ -43,4 +43,5 @@ type (
 	}
 	ReqCheckpointData common.Hash
 	ReqBeaconBlock    common.Hash
+	ReqFinality       struct{}
 )
diff --git a/beacon/light/sync/update_sync.go b/beacon/light/sync/update_sync.go
index 71801b1b60..9549ee5992 100644
--- a/beacon/light/sync/update_sync.go
+++ b/beacon/light/sync/update_sync.go
@@ -84,6 +84,7 @@ func (s *CheckpointInit) Process(requester request.Requester, events []request.E
 	if s.initialized {
 		return
 	}
+
 	for _, event := range events {
 		switch event.Type {
 		case request.EvResponse, request.EvFail, request.EvTimeout:
@@ -132,10 +133,12 @@ func (s *CheckpointInit) Process(requester request.Requester, events []request.E
 				newState.state = ssPrintStatus
 				s.serverState[sid.Server] = newState
 			}
+
 		case request.EvUnregistered:
 			delete(s.serverState, event.Server)
 		}
 	}
+
 	// start a request if possible
 	for _, server := range requester.CanSendTo() {
 		switch s.serverState[server].state {
@@ -156,6 +159,7 @@ func (s *CheckpointInit) Process(requester request.Requester, events []request.E
 			s.serverState[server] = newState
 		}
 	}
+
 	// print log message if necessary
 	for server, state := range s.serverState {
 		if state.state != ssPrintStatus {
@@ -316,9 +320,9 @@ func (s *ForwardUpdateSync) Process(requester request.Requester, events []reques
 			if !queued {
 				s.unlockRange(sid, req)
 			}
-		case EvNewSignedHead:
-			signedHead := event.Data.(types.SignedHeader)
-			s.nextSyncPeriod[event.Server] = types.SyncPeriod(signedHead.SignatureSlot + 256)
+		case EvNewOptimisticUpdate:
+			update := event.Data.(types.OptimisticUpdate)
+			s.nextSyncPeriod[event.Server] = types.SyncPeriod(update.SignatureSlot + 256)
 		case request.EvUnregistered:
 			delete(s.nextSyncPeriod, event.Server)
 		}
diff --git a/beacon/light/sync/update_sync_test.go b/beacon/light/sync/update_sync_test.go
index 1c4b3d6d76..8329bf28c9 100644
--- a/beacon/light/sync/update_sync_test.go
+++ b/beacon/light/sync/update_sync_test.go
@@ -68,9 +68,9 @@ func TestUpdateSyncParallel(t *testing.T) {
 	ts := NewTestScheduler(t, updateSync)
 	// add 2 servers, head at period 100; allow 3-3 parallel requests for each
 	ts.AddServer(testServer1, 3)
-	ts.ServerEvent(EvNewSignedHead, testServer1, types.SignedHeader{SignatureSlot: 0x2000*100 + 0x1000})
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer1, types.OptimisticUpdate{SignatureSlot: 0x2000*100 + 0x1000})
 	ts.AddServer(testServer2, 3)
-	ts.ServerEvent(EvNewSignedHead, testServer2, types.SignedHeader{SignatureSlot: 0x2000*100 + 0x1000})
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer2, types.OptimisticUpdate{SignatureSlot: 0x2000*100 + 0x1000})
 
 	// expect 6 requests to be sent
 	ts.Run(1,
@@ -150,11 +150,11 @@ func TestUpdateSyncDifferentHeads(t *testing.T) {
 	ts := NewTestScheduler(t, updateSync)
 	// add 3 servers with different announced head periods
 	ts.AddServer(testServer1, 1)
-	ts.ServerEvent(EvNewSignedHead, testServer1, types.SignedHeader{SignatureSlot: 0x2000*15 + 0x1000})
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer1, types.OptimisticUpdate{SignatureSlot: 0x2000*15 + 0x1000})
 	ts.AddServer(testServer2, 1)
-	ts.ServerEvent(EvNewSignedHead, testServer2, types.SignedHeader{SignatureSlot: 0x2000*16 + 0x1000})
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer2, types.OptimisticUpdate{SignatureSlot: 0x2000*16 + 0x1000})
 	ts.AddServer(testServer3, 1)
-	ts.ServerEvent(EvNewSignedHead, testServer3, types.SignedHeader{SignatureSlot: 0x2000*17 + 0x1000})
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer3, types.OptimisticUpdate{SignatureSlot: 0x2000*17 + 0x1000})
 
 	// expect request to the best announced head
 	ts.Run(1, testServer3, ReqUpdates{FirstPeriod: 10, Count: 7})
@@ -190,7 +190,7 @@ func TestUpdateSyncDifferentHeads(t *testing.T) {
 
 	// a new server is registered with announced head period 17
 	ts.AddServer(testServer4, 1)
-	ts.ServerEvent(EvNewSignedHead, testServer4, types.SignedHeader{SignatureSlot: 0x2000*17 + 0x1000})
+	ts.ServerEvent(EvNewOptimisticUpdate, testServer4, types.OptimisticUpdate{SignatureSlot: 0x2000*17 + 0x1000})
 	// expect request to sync one more period
 	ts.Run(7, testServer4, ReqUpdates{FirstPeriod: 16, Count: 1})
 
diff --git a/beacon/types/exec_payload.go b/beacon/types/exec_payload.go
index 604de288d2..718f98f529 100644
--- a/beacon/types/exec_payload.go
+++ b/beacon/types/exec_payload.go
@@ -66,9 +66,8 @@ func convertPayload[T payloadType](payload T, parentRoot *zrntcommon.Root) (*typ
 	block := types.NewBlockWithHeader(&header)
 	block = block.WithBody(transactions, nil)
 	block = block.WithWithdrawals(withdrawals)
-	hash := block.Hash()
-	if hash != expectedHash {
-		return block, fmt.Errorf("Sanity check failed, payload hash does not match (expected %x, got %x)", expectedHash, hash)
+	if hash := block.Hash(); hash != expectedHash {
+		return nil, fmt.Errorf("Sanity check failed, payload hash does not match (expected %x, got %x)", expectedHash, hash)
 	}
 	return block, nil
 }
diff --git a/beacon/types/light_sync.go b/beacon/types/light_sync.go
index 62becdb21c..3e9b13d0e2 100644
--- a/beacon/types/light_sync.go
+++ b/beacon/types/light_sync.go
@@ -23,7 +23,7 @@ import (
 	"github.com/ethereum/go-ethereum/beacon/merkle"
 	"github.com/ethereum/go-ethereum/beacon/params"
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/types"
+	ctypes "github.com/ethereum/go-ethereum/core/types"
 )
 
 // HeadInfo represents an unvalidated new head announcement.
@@ -142,17 +142,57 @@ func (u UpdateScore) BetterThan(w UpdateScore) bool {
 	return u.SignerCount > w.SignerCount
 }
 
+// HeaderWithExecProof contains a beacon header and proves the belonging execution
+// payload header with a Merkle proof.
 type HeaderWithExecProof struct {
 	Header
 	PayloadHeader *ExecutionHeader
 	PayloadBranch merkle.Values
 }
 
+// Validate verifies the Merkle proof of the execution payload header.
 func (h *HeaderWithExecProof) Validate() error {
-	payloadRoot := h.PayloadHeader.PayloadRoot()
-	return merkle.VerifyProof(h.BodyRoot, params.BodyIndexExecPayload, h.PayloadBranch, payloadRoot)
+	return merkle.VerifyProof(h.BodyRoot, params.BodyIndexExecPayload, h.PayloadBranch, h.PayloadHeader.PayloadRoot())
 }
 
+// OptimisticUpdate proves sync committee commitment on the attested beacon header.
+// It also proves the belonging execution payload header with a Merkle proof.
+//
+// See data structure definition here:
+// https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/light-client/sync-protocol.md#lightclientoptimisticupdate
+type OptimisticUpdate struct {
+	Attested HeaderWithExecProof
+	// Sync committee BLS signature aggregate
+	Signature SyncAggregate
+	// Slot in which the signature has been created (newer than Header.Slot,
+	// determines the signing sync committee)
+	SignatureSlot uint64
+}
+
+// SignedHeader returns the signed attested header of the update.
+func (u *OptimisticUpdate) SignedHeader() SignedHeader {
+	return SignedHeader{
+		Header:        u.Attested.Header,
+		Signature:     u.Signature,
+		SignatureSlot: u.SignatureSlot,
+	}
+}
+
+// Validate verifies the Merkle proof proving the execution payload header.
+// Note that the sync committee signature of the attested header should be
+// verified separately by a synced committee chain.
+func (u *OptimisticUpdate) Validate() error {
+	return u.Attested.Validate()
+}
+
+// FinalityUpdate proves a finalized beacon header by a sync committee commitment
+// on an attested beacon header, referring to the latest finalized header with a
+// Merkle proof.
+// It also proves the execution payload header belonging to both the attested and
+// the finalized beacon header with Merkle proofs.
+//
+// See data structure definition here:
+// https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/light-client/sync-protocol.md#lightclientfinalityupdate
 type FinalityUpdate struct {
 	Attested, Finalized HeaderWithExecProof
 	FinalityBranch      merkle.Values
@@ -163,6 +203,7 @@ type FinalityUpdate struct {
 	SignatureSlot uint64
 }
 
+// SignedHeader returns the signed attested header of the update.
 func (u *FinalityUpdate) SignedHeader() SignedHeader {
 	return SignedHeader{
 		Header:        u.Attested.Header,
@@ -171,6 +212,10 @@ func (u *FinalityUpdate) SignedHeader() SignedHeader {
 	}
 }
 
+// Validate verifies the Merkle proofs proving the finalized beacon header and
+// the execution payload headers belonging to the attested and finalized headers.
+// Note that the sync committee signature of the attested header should be
+// verified separately by a synced committee chain.
 func (u *FinalityUpdate) Validate() error {
 	if err := u.Attested.Validate(); err != nil {
 		return err
@@ -186,6 +231,6 @@ func (u *FinalityUpdate) Validate() error {
 // finalized execution block.
 type ChainHeadEvent struct {
 	BeaconHead Header
-	Block      *types.Block
+	Block      *ctypes.Block
 	Finalized  common.Hash
 }
diff --git a/core/blockchain_insert.go b/core/blockchain_insert.go
index c7c4c4bfea..49e913aada 100644
--- a/core/blockchain_insert.go
+++ b/core/blockchain_insert.go
@@ -170,7 +170,7 @@ func (it *insertIterator) current() *types.Header {
 	return it.chain[it.index].Header()
 }
 
-// first returns the first block in the it.
+// first returns the first block in it.
 func (it *insertIterator) first() *types.Block {
 	return it.chain[0]
 }
diff --git a/core/state/iterator.go b/core/state/iterator.go
index dc84ce689b..83c552ca1a 100644
--- a/core/state/iterator.go
+++ b/core/state/iterator.go
@@ -46,7 +46,7 @@ type nodeIterator struct {
 	Error error // Failure set in case of an internal error in the iterator
 }
 
-// newNodeIterator creates an post-order state node iterator.
+// newNodeIterator creates a post-order state node iterator.
 func newNodeIterator(state *StateDB) *nodeIterator {
 	return &nodeIterator{
 		state: state,
diff --git a/core/state/snapshot/context.go b/core/state/snapshot/context.go
index 67d7e41a03..8a19960501 100644
--- a/core/state/snapshot/context.go
+++ b/core/state/snapshot/context.go
@@ -46,7 +46,7 @@ type generatorStats struct {
 	storage  common.StorageSize // Total account and storage slot size(generation or recovery)
 }
 
-// Log creates an contextual log with the given message and the context pulled
+// Log creates a contextual log with the given message and the context pulled
 // from the internally maintained statistics.
 func (gs *generatorStats) Log(msg string, root common.Hash, marker []byte) {
 	var ctx []interface{}
diff --git a/core/state/snapshot/iterator_binary.go b/core/state/snapshot/iterator_binary.go
index 22184b2545..edf471213f 100644
--- a/core/state/snapshot/iterator_binary.go
+++ b/core/state/snapshot/iterator_binary.go
@@ -68,7 +68,7 @@ func (dl *diffLayer) initBinaryStorageIterator(account common.Hash) Iterator {
 	parent, ok := dl.parent.(*diffLayer)
 	if !ok {
 		// If the storage in this layer is already destructed, discard all
-		// deeper layers but still return an valid single-branch iterator.
+		// deeper layers but still return a valid single-branch iterator.
 		a, destructed := dl.StorageIterator(account, common.Hash{})
 		if destructed {
 			l := &binaryIterator{
@@ -92,7 +92,7 @@ func (dl *diffLayer) initBinaryStorageIterator(account common.Hash) Iterator {
 		return l
 	}
 	// If the storage in this layer is already destructed, discard all
-	// deeper layers but still return an valid single-branch iterator.
+	// deeper layers but still return a valid single-branch iterator.
 	a, destructed := dl.StorageIterator(account, common.Hash{})
 	if destructed {
 		l := &binaryIterator{
diff --git a/core/state/snapshot/iterator_fast.go b/core/state/snapshot/iterator_fast.go
index 9b018bac56..fa0daea7ba 100644
--- a/core/state/snapshot/iterator_fast.go
+++ b/core/state/snapshot/iterator_fast.go
@@ -25,7 +25,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 )
 
-// weightedIterator is a iterator with an assigned weight. It is used to prioritise
+// weightedIterator is an iterator with an assigned weight. It is used to prioritise
 // which account or storage slot is the correct one if multiple iterators find the
 // same one (modified in multiple consecutive blocks).
 type weightedIterator struct {
diff --git a/core/state/snapshot/snapshot.go b/core/state/snapshot/snapshot.go
index 5c38cb7252..89a4c16c20 100644
--- a/core/state/snapshot/snapshot.go
+++ b/core/state/snapshot/snapshot.go
@@ -835,7 +835,7 @@ func (t *Tree) disklayer() *diskLayer {
 	}
 }
 
-// diskRoot is a internal helper function to return the disk layer root.
+// diskRoot is an internal helper function to return the disk layer root.
 // The lock of snapTree is assumed to be held already.
 func (t *Tree) diskRoot() common.Hash {
 	disklayer := t.disklayer()
diff --git a/core/state/state_object.go b/core/state/state_object.go
index 1aa7946fd0..db3c32f2f2 100644
--- a/core/state/state_object.go
+++ b/core/state/state_object.go
@@ -376,7 +376,7 @@ func (s *stateObject) updateTrie() (Trie, error) {
 // new storage trie root.
 func (s *stateObject) updateRoot() {
 	// Flush cached storage mutations into trie, short circuit if any error
-	// is occurred or there is not change in the trie.
+	// is occurred or there is no change in the trie.
 	tr, err := s.updateTrie()
 	if err != nil || tr == nil {
 		return
diff --git a/core/vm/contracts.go b/core/vm/contracts.go
index 3d4819a74b..5f7de8007b 100644
--- a/core/vm/contracts.go
+++ b/core/vm/contracts.go
@@ -114,6 +114,16 @@ var PrecompiledContractsCancun = map[common.Address]PrecompiledContract{
 // PrecompiledContractsPrague contains the set of pre-compiled Ethereum
 // contracts used in the Prague release.
 var PrecompiledContractsPrague = map[common.Address]PrecompiledContract{
+	common.BytesToAddress([]byte{0x01}): &ecrecover{},
+	common.BytesToAddress([]byte{0x02}): &sha256hash{},
+	common.BytesToAddress([]byte{0x03}): &ripemd160hash{},
+	common.BytesToAddress([]byte{0x04}): &dataCopy{},
+	common.BytesToAddress([]byte{0x05}): &bigModExp{eip2565: true},
+	common.BytesToAddress([]byte{0x06}): &bn256AddIstanbul{},
+	common.BytesToAddress([]byte{0x07}): &bn256ScalarMulIstanbul{},
+	common.BytesToAddress([]byte{0x08}): &bn256PairingIstanbul{},
+	common.BytesToAddress([]byte{0x09}): &blake2F{},
+	common.BytesToAddress([]byte{0x0a}): &kzgPointEvaluation{},
 	common.BytesToAddress([]byte{0x0b}): &bls12381G1Add{},
 	common.BytesToAddress([]byte{0x0c}): &bls12381G1Mul{},
 	common.BytesToAddress([]byte{0x0d}): &bls12381G1MultiExp{},
diff --git a/eth/catalyst/api_test.go b/eth/catalyst/api_test.go
index ab1d78f90e..b8645d6be4 100644
--- a/eth/catalyst/api_test.go
+++ b/eth/catalyst/api_test.go
@@ -112,7 +112,7 @@ func TestEth2AssembleBlock(t *testing.T) {
 	if err != nil {
 		t.Fatalf("error signing transaction, err=%v", err)
 	}
-	ethservice.TxPool().Add([]*types.Transaction{tx}, true, false)
+	ethservice.TxPool().Add([]*types.Transaction{tx}, true, true)
 	blockParams := engine.PayloadAttributes{
 		Timestamp: blocks[9].Time() + 5,
 	}
@@ -189,7 +189,7 @@ func TestEth2PrepareAndGetPayload(t *testing.T) {
 
 	// Put the 10th block's tx in the pool and produce a new block
 	txs := blocks[9].Transactions()
-	ethservice.TxPool().Add(txs, true, false)
+	ethservice.TxPool().Add(txs, true, true)
 	blockParams := engine.PayloadAttributes{
 		Timestamp: blocks[8].Time() + 5,
 	}
@@ -310,13 +310,13 @@ func TestEth2NewBlock(t *testing.T) {
 		statedb, _ := ethservice.BlockChain().StateAt(parent.Root())
 		nonce := statedb.GetNonce(testAddr)
 		tx, _ := types.SignTx(types.NewContractCreation(nonce, new(big.Int), 1000000, big.NewInt(2*params.InitialBaseFee), logCode), types.LatestSigner(ethservice.BlockChain().Config()), testKey)
-		ethservice.TxPool().Add([]*types.Transaction{tx}, true, false)
+		ethservice.TxPool().Add([]*types.Transaction{tx}, true, true)
 
 		execData, err := assembleWithTransactions(api, parent.Hash(), &engine.PayloadAttributes{
 			Timestamp: parent.Time() + 5,
 		}, 1)
 		if err != nil {
-			t.Fatalf("Failed to create the executable data %v", err)
+			t.Fatalf("Failed to create the executable data, block %d: %v", i, err)
 		}
 		block, err := engine.ExecutableDataToBlock(*execData, nil, nil)
 		if err != nil {
diff --git a/eth/protocols/snap/gentrie.go b/eth/protocols/snap/gentrie.go
index 8ef1a00753..81c2640b62 100644
--- a/eth/protocols/snap/gentrie.go
+++ b/eth/protocols/snap/gentrie.go
@@ -132,7 +132,7 @@ func (t *pathTrie) onTrieNode(path []byte, hash common.Hash, blob []byte) {
 	//
 	// The extension node is detected if its path is the prefix of last committed
 	// one and path gap is larger than one. If the path gap is only one byte,
-	// the current node could either be a full node, or a extension with single
+	// the current node could either be a full node, or an extension with single
 	// byte key. In either case, no gaps will be left in the path.
 	if t.last != nil && bytes.HasPrefix(t.last, path) && len(t.last)-len(path) > 1 {
 		for i := len(path) + 1; i < len(t.last); i++ {
diff --git a/metrics/README.md b/metrics/README.md
index e2d7945008..85b119470a 100644
--- a/metrics/README.md
+++ b/metrics/README.md
@@ -100,24 +100,6 @@ go influxdb.InfluxDB(metrics.DefaultRegistry,
 )
 ```
 
-Periodically upload every metric to Librato using the [Librato client](https://github.com/mihasya/go-metrics-librato):
-
-**Note**: the client included with this repository under the `librato` package
-has been deprecated and moved to the repository linked above.
-
-```go
-import "github.com/mihasya/go-metrics-librato"
-
-go librato.Librato(metrics.DefaultRegistry,
-    10e9,                  // interval
-    "example@example.com", // account owner email address
-    "token",               // Librato API token
-    "hostname",            // source
-    []float64{0.95},       // percentiles to send
-    time.Millisecond,      // time unit
-)
-```
-
 Periodically emit every metric to StatHat:
 
 ```go
@@ -157,7 +139,6 @@ Publishing Metrics
 
 Clients are available for the following destinations:
 
-* Librato - https://github.com/mihasya/go-metrics-librato
 * Graphite - https://github.com/cyberdelia/go-metrics-graphite
 * InfluxDB - https://github.com/vrischmann/go-metrics-influxdb
 * Ganglia - https://github.com/appscode/metlia
diff --git a/metrics/librato/client.go b/metrics/librato/client.go
deleted file mode 100644
index f1b9e1e916..0000000000
--- a/metrics/librato/client.go
+++ /dev/null
@@ -1,104 +0,0 @@
-package librato
-
-import (
-	"bytes"
-	"encoding/json"
-	"fmt"
-	"io"
-	"net/http"
-)
-
-const Operations = "operations"
-const OperationsShort = "ops"
-
-type LibratoClient struct {
-	Email, Token string
-}
-
-// property strings
-const (
-	// display attributes
-	Color             = "color"
-	DisplayMax        = "display_max"
-	DisplayMin        = "display_min"
-	DisplayUnitsLong  = "display_units_long"
-	DisplayUnitsShort = "display_units_short"
-	DisplayStacked    = "display_stacked"
-	DisplayTransform  = "display_transform"
-	// special gauge display attributes
-	SummarizeFunction = "summarize_function"
-	Aggregate         = "aggregate"
-
-	// metric keys
-	Name        = "name"
-	Period      = "period"
-	Description = "description"
-	DisplayName = "display_name"
-	Attributes  = "attributes"
-
-	// measurement keys
-	MeasureTime = "measure_time"
-	Source      = "source"
-	Value       = "value"
-
-	// special gauge keys
-	Count      = "count"
-	Sum        = "sum"
-	Max        = "max"
-	Min        = "min"
-	SumSquares = "sum_squares"
-
-	// batch keys
-	Counters = "counters"
-	Gauges   = "gauges"
-
-	MetricsPostUrl = "https://metrics-api.librato.com/v1/metrics"
-)
-
-type Measurement map[string]interface{}
-type Metric map[string]interface{}
-
-type Batch struct {
-	Gauges      []Measurement `json:"gauges,omitempty"`
-	Counters    []Measurement `json:"counters,omitempty"`
-	MeasureTime int64         `json:"measure_time"`
-	Source      string        `json:"source"`
-}
-
-func (c *LibratoClient) PostMetrics(batch Batch) (err error) {
-	var (
-		js   []byte
-		req  *http.Request
-		resp *http.Response
-	)
-
-	if len(batch.Counters) == 0 && len(batch.Gauges) == 0 {
-		return nil
-	}
-
-	if js, err = json.Marshal(batch); err != nil {
-		return
-	}
-
-	if req, err = http.NewRequest(http.MethodPost, MetricsPostUrl, bytes.NewBuffer(js)); err != nil {
-		return
-	}
-
-	req.Header.Set("Content-Type", "application/json")
-	req.SetBasicAuth(c.Email, c.Token)
-
-	resp, err = http.DefaultClient.Do(req)
-	if err != nil {
-		return
-	}
-	defer resp.Body.Close()
-
-	if resp.StatusCode != http.StatusOK {
-		var body []byte
-		if body, err = io.ReadAll(resp.Body); err != nil {
-			body = []byte(fmt.Sprintf("(could not fetch response body for error: %s)", err))
-		}
-		err = fmt.Errorf("unable to post to Librato: %d %s %s", resp.StatusCode, resp.Status, string(body))
-	}
-	return
-}
diff --git a/metrics/librato/librato.go b/metrics/librato/librato.go
deleted file mode 100644
index a86f758637..0000000000
--- a/metrics/librato/librato.go
+++ /dev/null
@@ -1,254 +0,0 @@
-package librato
-
-import (
-	"fmt"
-	"log"
-	"math"
-	"regexp"
-	"time"
-
-	"github.com/ethereum/go-ethereum/metrics"
-)
-
-// a regexp for extracting the unit from time.Duration.String
-var unitRegexp = regexp.MustCompile(`[^\\d]+$`)
-
-// a helper that turns a time.Duration into librato display attributes for timer metrics
-func translateTimerAttributes(d time.Duration) (attrs map[string]interface{}) {
-	attrs = make(map[string]interface{})
-	attrs[DisplayTransform] = fmt.Sprintf("x/%d", int64(d))
-	attrs[DisplayUnitsShort] = string(unitRegexp.Find([]byte(d.String())))
-	return
-}
-
-type Reporter struct {
-	Email, Token    string
-	Namespace       string
-	Source          string
-	Interval        time.Duration
-	Registry        metrics.Registry
-	Percentiles     []float64              // percentiles to report on histogram metrics
-	TimerAttributes map[string]interface{} // units in which timers will be displayed
-	intervalSec     int64
-}
-
-func NewReporter(r metrics.Registry, d time.Duration, e string, t string, s string, p []float64, u time.Duration) *Reporter {
-	return &Reporter{e, t, "", s, d, r, p, translateTimerAttributes(u), int64(d / time.Second)}
-}
-
-func Librato(r metrics.Registry, d time.Duration, e string, t string, s string, p []float64, u time.Duration) {
-	NewReporter(r, d, e, t, s, p, u).Run()
-}
-
-func (rep *Reporter) Run() {
-	log.Printf("WARNING: This client has been DEPRECATED! It has been moved to https://github.com/mihasya/go-metrics-librato and will be removed from rcrowley/go-metrics on August 5th 2015")
-	ticker := time.NewTicker(rep.Interval)
-	defer ticker.Stop()
-	metricsApi := &LibratoClient{rep.Email, rep.Token}
-	for now := range ticker.C {
-		var metrics Batch
-		var err error
-		if metrics, err = rep.BuildRequest(now, rep.Registry); err != nil {
-			log.Printf("ERROR constructing librato request body %s", err)
-			continue
-		}
-		if err := metricsApi.PostMetrics(metrics); err != nil {
-			log.Printf("ERROR sending metrics to librato %s", err)
-			continue
-		}
-	}
-}
-
-// calculate sum of squares from data provided by metrics.Histogram
-// see http://en.wikipedia.org/wiki/Standard_deviation#Rapid_calculation_methods
-func sumSquares(icount int64, mean, stDev float64) float64 {
-	count := float64(icount)
-	sumSquared := math.Pow(count*mean, 2)
-	sumSquares := math.Pow(count*stDev, 2) + sumSquared/count
-	if math.IsNaN(sumSquares) {
-		return 0.0
-	}
-	return sumSquares
-}
-func sumSquaresTimer(t metrics.TimerSnapshot) float64 {
-	count := float64(t.Count())
-	sumSquared := math.Pow(count*t.Mean(), 2)
-	sumSquares := math.Pow(count*t.StdDev(), 2) + sumSquared/count
-	if math.IsNaN(sumSquares) {
-		return 0.0
-	}
-	return sumSquares
-}
-
-func (rep *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot Batch, err error) {
-	snapshot = Batch{
-		// coerce timestamps to a stepping fn so that they line up in Librato graphs
-		MeasureTime: (now.Unix() / rep.intervalSec) * rep.intervalSec,
-		Source:      rep.Source,
-	}
-	snapshot.Gauges = make([]Measurement, 0)
-	snapshot.Counters = make([]Measurement, 0)
-	histogramGaugeCount := 1 + len(rep.Percentiles)
-	r.Each(func(name string, metric interface{}) {
-		if rep.Namespace != "" {
-			name = fmt.Sprintf("%s.%s", rep.Namespace, name)
-		}
-		measurement := Measurement{}
-		measurement[Period] = rep.Interval.Seconds()
-		switch m := metric.(type) {
-		case metrics.Counter:
-			ms := m.Snapshot()
-			if ms.Count() > 0 {
-				measurement[Name] = fmt.Sprintf("%s.%s", name, "count")
-				measurement[Value] = float64(ms.Count())
-				measurement[Attributes] = map[string]interface{}{
-					DisplayUnitsLong:  Operations,
-					DisplayUnitsShort: OperationsShort,
-					DisplayMin:        "0",
-				}
-				snapshot.Counters = append(snapshot.Counters, measurement)
-			}
-		case metrics.CounterFloat64:
-			if count := m.Snapshot().Count(); count > 0 {
-				measurement[Name] = fmt.Sprintf("%s.%s", name, "count")
-				measurement[Value] = count
-				measurement[Attributes] = map[string]interface{}{
-					DisplayUnitsLong:  Operations,
-					DisplayUnitsShort: OperationsShort,
-					DisplayMin:        "0",
-				}
-				snapshot.Counters = append(snapshot.Counters, measurement)
-			}
-		case metrics.Gauge:
-			measurement[Name] = name
-			measurement[Value] = float64(m.Snapshot().Value())
-			snapshot.Gauges = append(snapshot.Gauges, measurement)
-		case metrics.GaugeFloat64:
-			measurement[Name] = name
-			measurement[Value] = m.Snapshot().Value()
-			snapshot.Gauges = append(snapshot.Gauges, measurement)
-		case metrics.GaugeInfo:
-			measurement[Name] = name
-			measurement[Value] = m.Snapshot().Value()
-			snapshot.Gauges = append(snapshot.Gauges, measurement)
-		case metrics.Histogram:
-			ms := m.Snapshot()
-			if ms.Count() > 0 {
-				gauges := make([]Measurement, histogramGaugeCount)
-				measurement[Name] = fmt.Sprintf("%s.%s", name, "hist")
-				measurement[Count] = uint64(ms.Count())
-				measurement[Max] = float64(ms.Max())
-				measurement[Min] = float64(ms.Min())
-				measurement[Sum] = float64(ms.Sum())
-				measurement[SumSquares] = sumSquares(ms.Count(), ms.Mean(), ms.StdDev())
-				gauges[0] = measurement
-				for i, p := range rep.Percentiles {
-					gauges[i+1] = Measurement{
-						Name:   fmt.Sprintf("%s.%.2f", measurement[Name], p),
-						Value:  ms.Percentile(p),
-						Period: measurement[Period],
-					}
-				}
-				snapshot.Gauges = append(snapshot.Gauges, gauges...)
-			}
-		case metrics.Meter:
-			ms := m.Snapshot()
-			measurement[Name] = name
-			measurement[Value] = float64(ms.Count())
-			snapshot.Counters = append(snapshot.Counters, measurement)
-			snapshot.Gauges = append(snapshot.Gauges,
-				Measurement{
-					Name:   fmt.Sprintf("%s.%s", name, "1min"),
-					Value:  ms.Rate1(),
-					Period: int64(rep.Interval.Seconds()),
-					Attributes: map[string]interface{}{
-						DisplayUnitsLong:  Operations,
-						DisplayUnitsShort: OperationsShort,
-						DisplayMin:        "0",
-					},
-				},
-				Measurement{
-					Name:   fmt.Sprintf("%s.%s", name, "5min"),
-					Value:  ms.Rate5(),
-					Period: int64(rep.Interval.Seconds()),
-					Attributes: map[string]interface{}{
-						DisplayUnitsLong:  Operations,
-						DisplayUnitsShort: OperationsShort,
-						DisplayMin:        "0",
-					},
-				},
-				Measurement{
-					Name:   fmt.Sprintf("%s.%s", name, "15min"),
-					Value:  ms.Rate15(),
-					Period: int64(rep.Interval.Seconds()),
-					Attributes: map[string]interface{}{
-						DisplayUnitsLong:  Operations,
-						DisplayUnitsShort: OperationsShort,
-						DisplayMin:        "0",
-					},
-				},
-			)
-		case metrics.Timer:
-			ms := m.Snapshot()
-			measurement[Name] = name
-			measurement[Value] = float64(ms.Count())
-			snapshot.Counters = append(snapshot.Counters, measurement)
-			if ms.Count() > 0 {
-				libratoName := fmt.Sprintf("%s.%s", name, "timer.mean")
-				gauges := make([]Measurement, histogramGaugeCount)
-				gauges[0] = Measurement{
-					Name:       libratoName,
-					Count:      uint64(ms.Count()),
-					Sum:        ms.Mean() * float64(ms.Count()),
-					Max:        float64(ms.Max()),
-					Min:        float64(ms.Min()),
-					SumSquares: sumSquaresTimer(ms),
-					Period:     int64(rep.Interval.Seconds()),
-					Attributes: rep.TimerAttributes,
-				}
-				for i, p := range rep.Percentiles {
-					gauges[i+1] = Measurement{
-						Name:       fmt.Sprintf("%s.timer.%2.0f", name, p*100),
-						Value:      ms.Percentile(p),
-						Period:     int64(rep.Interval.Seconds()),
-						Attributes: rep.TimerAttributes,
-					}
-				}
-				snapshot.Gauges = append(snapshot.Gauges, gauges...)
-				snapshot.Gauges = append(snapshot.Gauges,
-					Measurement{
-						Name:   fmt.Sprintf("%s.%s", name, "rate.1min"),
-						Value:  ms.Rate1(),
-						Period: int64(rep.Interval.Seconds()),
-						Attributes: map[string]interface{}{
-							DisplayUnitsLong:  Operations,
-							DisplayUnitsShort: OperationsShort,
-							DisplayMin:        "0",
-						},
-					},
-					Measurement{
-						Name:   fmt.Sprintf("%s.%s", name, "rate.5min"),
-						Value:  ms.Rate5(),
-						Period: int64(rep.Interval.Seconds()),
-						Attributes: map[string]interface{}{
-							DisplayUnitsLong:  Operations,
-							DisplayUnitsShort: OperationsShort,
-							DisplayMin:        "0",
-						},
-					},
-					Measurement{
-						Name:   fmt.Sprintf("%s.%s", name, "rate.15min"),
-						Value:  ms.Rate15(),
-						Period: int64(rep.Interval.Seconds()),
-						Attributes: map[string]interface{}{
-							DisplayUnitsLong:  Operations,
-							DisplayUnitsShort: OperationsShort,
-							DisplayMin:        "0",
-						},
-					},
-				)
-			}
-		}
-	})
-	return
-}
diff --git a/miner/worker.go b/miner/worker.go
index 4924952478..5dc3e2056b 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -339,7 +339,7 @@ func (miner *Miner) commitTransactions(env *environment, plainTxs, blobTxs *tran
 			continue
 		}
 		// Error may be ignored here. The error has already been checked
-		// during transaction acceptance is the transaction pool.
+		// during transaction acceptance in the transaction pool.
 		from, _ := types.Sender(env.signer, tx)
 
 		// Check whether the tx is replay protected. If we're not in the EIP155 hf
diff --git a/rlp/rlpgen/gen.go b/rlp/rlpgen/gen.go
index 0c65864826..ff39874737 100644
--- a/rlp/rlpgen/gen.go
+++ b/rlp/rlpgen/gen.go
@@ -158,7 +158,7 @@ type op interface {
 // basicOp handles basic types bool, uint*, string.
 type basicOp struct {
 	typ           types.Type
-	writeMethod   string     // calle write the value
+	writeMethod   string     // EncoderBuffer writer method name
 	writeArgType  types.Type // parameter type of writeMethod
 	decMethod     string
 	decResultType types.Type // return type of decMethod
diff --git a/rpc/subscription.go b/rpc/subscription.go
index d3dff32a27..d77c655bf9 100644
--- a/rpc/subscription.go
+++ b/rpc/subscription.go
@@ -97,7 +97,7 @@ func NotifierFromContext(ctx context.Context) (*Notifier, bool) {
 	return n, ok
 }
 
-// Notifier is tied to a RPC connection that supports subscriptions.
+// Notifier is tied to an RPC connection that supports subscriptions.
 // Server callbacks use the notifier to send notifications.
 type Notifier struct {
 	h         *handler
diff --git a/rpc/types.go b/rpc/types.go
index d124081786..2e53174b87 100644
--- a/rpc/types.go
+++ b/rpc/types.go
@@ -38,7 +38,7 @@ type API struct {
 }
 
 // ServerCodec implements reading, parsing and writing RPC messages for the server side of
-// a RPC session. Implementations must be go-routine safe since the codec can be called in
+// an RPC session. Implementations must be go-routine safe since the codec can be called in
 // multiple go-routines concurrently.
 type ServerCodec interface {
 	peerInfo() PeerInfo
diff --git a/trie/errors.go b/trie/errors.go
index 7be7041c7f..ce5cb13423 100644
--- a/trie/errors.go
+++ b/trie/errors.go
@@ -23,7 +23,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 )
 
-// ErrCommitted is returned when a already committed trie is requested for usage.
+// ErrCommitted is returned when an already committed trie is requested for usage.
 // The potential usages can be `Get`, `Update`, `Delete`, `NodeIterator`, `Prove`
 // and so on.
 var ErrCommitted = errors.New("trie is already committed")
diff --git a/trie/proof.go b/trie/proof.go
index fd892fb4be..a39d6b4ea3 100644
--- a/trie/proof.go
+++ b/trie/proof.go
@@ -372,7 +372,7 @@ func unset(parent node, child node, key []byte, pos int, removeLeft bool) error
 		return unset(cld, cld.Children[key[pos]], key, pos+1, removeLeft)
 	case *shortNode:
 		if len(key[pos:]) < len(cld.Key) || !bytes.Equal(cld.Key, key[pos:pos+len(cld.Key)]) {
-			// Find the fork point, it's an non-existent branch.
+			// Find the fork point, it's a non-existent branch.
 			if removeLeft {
 				if bytes.Compare(cld.Key, key[pos:]) < 0 {
 					// The key of fork shortnode is less than the path
diff --git a/triedb/pathdb/database.go b/triedb/pathdb/database.go
index 2e7c662804..18f2eeef00 100644
--- a/triedb/pathdb/database.go
+++ b/triedb/pathdb/database.go
@@ -293,6 +293,7 @@ func (db *Database) Enable(root common.Hash) error {
 	// Ensure the provided state root matches the stored one.
 	root = types.TrieRootHash(root)
 	_, stored := rawdb.ReadAccountTrieNode(db.diskdb, nil)
+	stored = types.TrieRootHash(stored)
 	if stored != root {
 		return fmt.Errorf("state root mismatch: stored %x, synced %x", stored, root)
 	}
diff --git a/triedb/pathdb/database_test.go b/triedb/pathdb/database_test.go
index 30edef2760..29de534589 100644
--- a/triedb/pathdb/database_test.go
+++ b/triedb/pathdb/database_test.go
@@ -476,13 +476,13 @@ func TestDisable(t *testing.T) {
 
 	_, stored := rawdb.ReadAccountTrieNode(tester.db.diskdb, nil)
 	if err := tester.db.Disable(); err != nil {
-		t.Fatal("Failed to deactivate database")
+		t.Fatalf("Failed to deactivate database: %v", err)
 	}
 	if err := tester.db.Enable(types.EmptyRootHash); err == nil {
-		t.Fatalf("Invalid activation should be rejected")
+		t.Fatal("Invalid activation should be rejected")
 	}
 	if err := tester.db.Enable(stored); err != nil {
-		t.Fatal("Failed to activate database")
+		t.Fatalf("Failed to activate database: %v", err)
 	}
 
 	// Ensure journal is deleted from disk