beacon/engine/ssz: update types

beacon/engine/ssz/attributes_forks.go

@@ -1,136 +0,0 @@
-// Copyright 2026 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package ssz
-
-import (
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/karalabe/ssz"
-)
-
-// PayloadAttributesCancun is the Cancun/Prague/Osaka build attribute shape.
-type PayloadAttributesCancun struct {
-	Timestamp             uint64
-	PrevRandao            common.Hash
-	SuggestedFeeRecipient common.Address
-	Withdrawals           []*Withdrawal
-	ParentBeaconBlockRoot common.Hash
-}
-
-func (a *PayloadAttributesCancun) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	// 8 + 32 + 20 + 4(offset) + 32 = 96
-	size := uint32(96)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeSliceOfStaticObjects(siz, a.Withdrawals)
-	return size
-}
-
-func (a *PayloadAttributesCancun) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineUint64(c, &a.Timestamp)
-	ssz.DefineStaticBytes(c, &a.PrevRandao)
-	ssz.DefineStaticBytes(c, &a.SuggestedFeeRecipient)
-	ssz.DefineSliceOfStaticObjectsOffset(c, &a.Withdrawals, MaxWithdrawalsPerPayload)
-	ssz.DefineStaticBytes(c, &a.ParentBeaconBlockRoot)
-
-	ssz.DefineSliceOfStaticObjectsContent(c, &a.Withdrawals, MaxWithdrawalsPerPayload)
-}
-
-// PayloadAttributesShanghai = Cancun minus parent_beacon_block_root.
-type PayloadAttributesShanghai struct {
-	Timestamp             uint64
-	PrevRandao            common.Hash
-	SuggestedFeeRecipient common.Address
-	Withdrawals           []*Withdrawal
-}
-
-func (a *PayloadAttributesShanghai) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	size := uint32(8 + 32 + 20 + 4)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeSliceOfStaticObjects(siz, a.Withdrawals)
-	return size
-}
-
-func (a *PayloadAttributesShanghai) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineUint64(c, &a.Timestamp)
-	ssz.DefineStaticBytes(c, &a.PrevRandao)
-	ssz.DefineStaticBytes(c, &a.SuggestedFeeRecipient)
-	ssz.DefineSliceOfStaticObjectsOffset(c, &a.Withdrawals, MaxWithdrawalsPerPayload)
-
-	ssz.DefineSliceOfStaticObjectsContent(c, &a.Withdrawals, MaxWithdrawalsPerPayload)
-}
-
-// PayloadAttributesParis is the original (no withdrawals) shape.
-type PayloadAttributesParis struct {
-	Timestamp             uint64
-	PrevRandao            common.Hash
-	SuggestedFeeRecipient common.Address
-}
-
-func (*PayloadAttributesParis) SizeSSZ(*ssz.Sizer) uint32 { return 60 }
-
-func (a *PayloadAttributesParis) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineUint64(c, &a.Timestamp)
-	ssz.DefineStaticBytes(c, &a.PrevRandao)
-	ssz.DefineStaticBytes(c, &a.SuggestedFeeRecipient)
-}
-
-// ExecutionPayloadBodyCancun = Shanghai-shaped body (no BAL).
-type ExecutionPayloadBodyCancun struct {
-	Transactions [][]byte
-	Withdrawals  []*Withdrawal
-}
-
-func (b *ExecutionPayloadBodyCancun) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	size := uint32(8)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeSliceOfDynamicBytes(siz, b.Transactions)
-	size += ssz.SizeSliceOfStaticObjects(siz, b.Withdrawals)
-	return size
-}
-
-func (b *ExecutionPayloadBodyCancun) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineSliceOfDynamicBytesOffset(c, &b.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsOffset(c, &b.Withdrawals, MaxWithdrawalsPerPayload)
-
-	ssz.DefineSliceOfDynamicBytesContent(c, &b.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsContent(c, &b.Withdrawals, MaxWithdrawalsPerPayload)
-}
-
-// ExecutionPayloadBodyParis is the original transactions-only body.
-type ExecutionPayloadBodyParis struct {
-	Transactions [][]byte
-}
-
-func (b *ExecutionPayloadBodyParis) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	size := uint32(4)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeSliceOfDynamicBytes(siz, b.Transactions)
-	return size
-}
-
-func (b *ExecutionPayloadBodyParis) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineSliceOfDynamicBytesOffset(c, &b.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-
-	ssz.DefineSliceOfDynamicBytesContent(c, &b.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-}

beacon/engine/ssz/bodies.go

@@ -17,6 +17,8 @@
 package ssz
 
 import (
+	"fmt"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/karalabe/ssz"
 )
@@ -40,13 +42,70 @@ func (r *BodiesByHashRequest) DefineSSZ(c *ssz.Codec) {
 	ssz.DefineSliceOfStaticBytesContent(c, &r.BlockHashes, MaxBodiesRequest)
 }
 
-// BodyEntryAmsterdam is the per-block entry returned by /amsterdam/bodies/...
-type BodyEntryAmsterdam struct {
-	Available bool
-	Body      *ExecutionPayloadBodyAmsterdam
+// ExecutionPayloadBody is the monolithic body shape returned by /{fork}/bodies.
+//
+// Field groups:
+//   - base (Paris): Transactions
+//   - withdrawals (Shanghai): Withdrawals
+//   - bal (Amsterdam): BlockAccessList
+type ExecutionPayloadBody struct {
+	Transactions    [][]byte
+	Withdrawals     []*Withdrawal // Shanghai+
+	BlockAccessList []byte        // Amsterdam+
 }
 
-func (e *BodyEntryAmsterdam) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
+func (b *ExecutionPayloadBody) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
+	var size uint32 = 4 // transactions offset
+	if siz.Fork() >= ssz.ForkShapella {
+		size += 4 // withdrawals offset
+	}
+	if siz.Fork() >= forkAmsterdam {
+		size += 4 // block_access_list offset
+	}
+	if fixed {
+		return size
+	}
+	size += ssz.SizeSliceOfDynamicBytes(siz, b.Transactions)
+	if siz.Fork() >= ssz.ForkShapella {
+		size += ssz.SizeSliceOfStaticObjects(siz, b.Withdrawals)
+	}
+	if siz.Fork() >= forkAmsterdam {
+		size += ssz.SizeDynamicBytes(siz, b.BlockAccessList)
+	}
+	return size
+}
+
+func (b *ExecutionPayloadBody) DefineSSZ(c *ssz.Codec) {
+	// offset phase
+	ssz.DefineSliceOfDynamicBytesOffset(c, &b.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
+	ssz.DefineSliceOfStaticObjectsOffsetOnFork(c, &b.Withdrawals, MaxWithdrawalsPerPayload, fromShanghai)
+	ssz.DefineDynamicBytesOffsetOnFork(c, &b.BlockAccessList, MaxBalBytes, fromAmsterdam)
+
+	// content phase
+	ssz.DefineSliceOfDynamicBytesContent(c, &b.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
+	ssz.DefineSliceOfStaticObjectsContentOnFork(c, &b.Withdrawals, MaxWithdrawalsPerPayload, fromShanghai)
+	ssz.DefineDynamicBytesContentOnFork(c, &b.BlockAccessList, MaxBalBytes, fromAmsterdam)
+}
+
+// Validate enforces that fields absent for the given fork are empty.
+func (b *ExecutionPayloadBody) Validate(fork ssz.Fork) error {
+	if fork < ssz.ForkShapella && len(b.Withdrawals) > 0 {
+		return fmt.Errorf("withdrawals set but fork %d predates Shanghai", fork)
+	}
+	if fork < forkAmsterdam && len(b.BlockAccessList) > 0 {
+		return fmt.Errorf("block_access_list set but fork %d predates Amsterdam", fork)
+	}
+	return nil
+}
+
+// BodyEntry is the per-block entry returned by /{fork}/bodies/... The Body's
+// wire shape follows the codec fork, so this single type spans all forks.
+type BodyEntry struct {
+	Available bool
+	Body      *ExecutionPayloadBody
+}
+
+func (e *BodyEntry) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
 	size := uint32(1 + 4) // bool + offset
 	if fixed {
 		return size
@@ -55,19 +114,19 @@ func (e *BodyEntryAmsterdam) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
 	return size
 }
 
-func (e *BodyEntryAmsterdam) DefineSSZ(c *ssz.Codec) {
+func (e *BodyEntry) DefineSSZ(c *ssz.Codec) {
 	ssz.DefineBool(c, &e.Available)
 	ssz.DefineDynamicObjectOffset(c, &e.Body)
 
 	ssz.DefineDynamicObjectContent(c, &e.Body)
 }
 
-// BodiesResponseAmsterdam is the SSZ response of /amsterdam/bodies/...
-type BodiesResponseAmsterdam struct {
-	Entries []*BodyEntryAmsterdam
+// BodiesResponse is the SSZ response of /{fork}/bodies/...
+type BodiesResponse struct {
+	Entries []*BodyEntry
 }
 
-func (r *BodiesResponseAmsterdam) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
+func (r *BodiesResponse) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
 	size := uint32(4)
 	if fixed {
 		return size
@@ -76,87 +135,7 @@ func (r *BodiesResponseAmsterdam) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
 	return size
 }
 
-func (r *BodiesResponseAmsterdam) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineSliceOfDynamicObjectsOffset(c, &r.Entries, MaxBodiesRequest)
-	ssz.DefineSliceOfDynamicObjectsContent(c, &r.Entries, MaxBodiesRequest)
-}
-
-// BodyEntryCancun is the /cancun/bodies/... entry (Shanghai-shape body).
-type BodyEntryCancun struct {
-	Available bool
-	Body      *ExecutionPayloadBodyCancun
-}
-
-func (e *BodyEntryCancun) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	size := uint32(1 + 4)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeDynamicObject(siz, e.Body)
-	return size
-}
-
-func (e *BodyEntryCancun) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineBool(c, &e.Available)
-	ssz.DefineDynamicObjectOffset(c, &e.Body)
-
-	ssz.DefineDynamicObjectContent(c, &e.Body)
-}
-
-type BodiesResponseCancun struct {
-	Entries []*BodyEntryCancun
-}
-
-func (r *BodiesResponseCancun) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	size := uint32(4)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeSliceOfDynamicObjects(siz, r.Entries)
-	return size
-}
-
-func (r *BodiesResponseCancun) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineSliceOfDynamicObjectsOffset(c, &r.Entries, MaxBodiesRequest)
-	ssz.DefineSliceOfDynamicObjectsContent(c, &r.Entries, MaxBodiesRequest)
-}
-
-// BodyEntryParis is the /paris/bodies/... entry (transactions only).
-type BodyEntryParis struct {
-	Available bool
-	Body      *ExecutionPayloadBodyParis
-}
-
-func (e *BodyEntryParis) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	size := uint32(1 + 4)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeDynamicObject(siz, e.Body)
-	return size
-}
-
-func (e *BodyEntryParis) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineBool(c, &e.Available)
-	ssz.DefineDynamicObjectOffset(c, &e.Body)
-
-	ssz.DefineDynamicObjectContent(c, &e.Body)
-}
-
-type BodiesResponseParis struct {
-	Entries []*BodyEntryParis
-}
-
-func (r *BodiesResponseParis) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	size := uint32(4)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeSliceOfDynamicObjects(siz, r.Entries)
-	return size
-}
-
-func (r *BodiesResponseParis) DefineSSZ(c *ssz.Codec) {
+func (r *BodiesResponse) DefineSSZ(c *ssz.Codec) {
 	ssz.DefineSliceOfDynamicObjectsOffset(c, &r.Entries, MaxBodiesRequest)
 	ssz.DefineSliceOfDynamicObjectsContent(c, &r.Entries, MaxBodiesRequest)
 }

beacon/engine/ssz/bytecompat_test.go

@@ -0,0 +1,146 @@
+// Copyright 2026 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// Byte-compatibility guard for the monolith refactor. The golden hex strings
+// below were captured from the original per-fork structs (ExecutionPayload
+// {Paris,Shanghai,Cancun,Amsterdam} etc.) before they were collapsed into the
+// monolith types. Encoding the monolith with the same sample data on the
+// corresponding fork MUST reproduce these bytes exactly — that is the proof
+// the refactor is wire-compatible.
+
+package ssz
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/holiman/uint256"
+	"github.com/karalabe/ssz"
+)
+
+func encodeHexOnFork(t *testing.T, obj ssz.Object, fork ssz.Fork) string {
+	t.Helper()
+	buf := make([]byte, ssz.SizeOnFork(obj, fork))
+	if err := ssz.EncodeToBytesOnFork(buf, obj, fork); err != nil {
+		t.Fatalf("encode: %v", err)
+	}
+	return fmt.Sprintf("%x", buf)
+}
+
+// golden bytes captured from the pre-refactor per-fork structs.
+const (
+	goldenPayloadParis     = "1100000000000000000000000000000000000000000000000000000000000000220000000000000000000000000000000000000033000000000000000000000000000000000000000000000000000000000000004400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000005500000000000000000000000000000000000000000000000000000000000000640000000000000080c3c90100000000085200000000000000f1536500000000fc01000000863ba1010000000000000000000000000000000000000000000000000000006600000000000000000000000000000000000000000000000000000000000000ff010000657874080000000a000000020304"
+	goldenPayloadShanghai  = "1100000000000000000000000000000000000000000000000000000000000000220000000000000000000000000000000000000033000000000000000000000000000000000000000000000000000000000000004400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000005500000000000000000000000000000000000000000000000000000000000000640000000000000080c3c90100000000085200000000000000f15365000000000002000000863ba1010000000000000000000000000000000000000000000000000000006600000000000000000000000000000000000000000000000000000000000000030200000e020000657874080000000a0000000203040100000000000000020000000000000009000000000000000000000000000000000000000300000000000000"
+	goldenPayloadCancun    = "1100000000000000000000000000000000000000000000000000000000000000220000000000000000000000000000000000000033000000000000000000000000000000000000000000000000000000000000004400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000005500000000000000000000000000000000000000000000000000000000000000640000000000000080c3c90100000000085200000000000000f15365000000001002000000863ba1010000000000000000000000000000000000000000000000000000006600000000000000000000000000000000000000000000000000000000000000130200001e02000000000200000000000000000000000000657874080000000a0000000203040100000000000000020000000000000009000000000000000000000000000000000000000300000000000000"
+	goldenPayloadAmsterdam = "1100000000000000000000000000000000000000000000000000000000000000220000000000000000000000000000000000000033000000000000000000000000000000000000000000000000000000000000004400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000005500000000000000000000000000000000000000000000000000000000000000640000000000000080c3c90100000000085200000000000000f15365000000001c02000000863ba10100000000000000000000000000000000000000000000000000000066000000000000000000000000000000000000000000000000000000000000001f0200002a0200000000020000000000000000000000000056020000c800000000000000657874080000000a0000000203040100000000000000020000000000000009000000000000000000000000000000000000000300000000000000deadbeef"
+
+	goldenAttrsParis     = "00f153650000000055000000000000000000000000000000000000000000000000000000000000002200000000000000000000000000000000000000"
+	goldenAttrsShanghai  = "00f153650000000055000000000000000000000000000000000000000000000000000000000000002200000000000000000000000000000000000000400000000100000000000000020000000000000009000000000000000000000000000000000000000300000000000000"
+	goldenAttrsCancun    = "00f1536500000000550000000000000000000000000000000000000000000000000000000000000022000000000000000000000000000000000000006000000077000000000000000000000000000000000000000000000000000000000000000100000000000000020000000000000009000000000000000000000000000000000000000300000000000000"
+	goldenAttrsAmsterdam = "00f1536500000000550000000000000000000000000000000000000000000000000000000000000022000000000000000000000000000000000000007000000077000000000000000000000000000000000000000000000000000000000000002a0000000000000080c3c901000000000100000000000000020000000000000009000000000000000000000000000000000000000300000000000000"
+
+	goldenBodyParis     = "04000000080000000a000000020304"
+	goldenBodyCancun    = "0800000013000000080000000a0000000203040100000000000000020000000000000009000000000000000000000000000000000000000300000000000000"
+	goldenBodyAmsterdam = "0c0000001700000043000000080000000a0000000203040100000000000000020000000000000009000000000000000000000000000000000000000300000000000000deadbeef"
+)
+
+// sample field values, shared so only fork-specific fields move the bytes.
+var (
+	gParentHash   = common.Hash{0x11}
+	gFeeRecipient = common.Address{0x22}
+	gStateRoot    = common.Hash{0x33}
+	gReceiptsRoot = common.Hash{0x44}
+	gPrevRandao   = common.Hash{0x55}
+	gBlockHash    = common.Hash{0x66}
+	gExtra        = []byte("ext")
+	gTxs          = [][]byte{{0x02, 0x03}, {0x04}}
+	gWds          = []*Withdrawal{{Index: 1, ValidatorIndex: 2, Address: common.Address{0x09}, Amount: 3}}
+	gBaseFee      = uint256.NewInt(7e9)
+	gBeaconRoot   = common.Hash{0x77}
+	gBAL          = []byte{0xde, 0xad, 0xbe, 0xef}
+)
+
+// basePayload returns a monolith populated for the given fork (only the fork's
+// active fields are set, matching what the converters do).
+func basePayload(fork ssz.Fork) *ExecutionPayload {
+	p := &ExecutionPayload{
+		ParentHash: gParentHash, FeeRecipient: gFeeRecipient, StateRoot: gStateRoot,
+		ReceiptsRoot: gReceiptsRoot, PrevRandao: gPrevRandao, BlockNumber: 100,
+		GasLimit: 30000000, GasUsed: 21000, Timestamp: 1700000000, ExtraData: gExtra,
+		BaseFeePerGas: gBaseFee, BlockHash: gBlockHash, Transactions: gTxs,
+	}
+	if fork >= ssz.ForkShapella {
+		p.Withdrawals = gWds
+	}
+	if fork >= ssz.ForkDencun {
+		blob, excess := uint64(131072), uint64(0)
+		p.BlobGasUsed, p.ExcessBlobGas = &blob, &excess
+	}
+	if fork >= forkAmsterdam {
+		slot := uint64(200)
+		p.BlockAccessList = gBAL
+		p.SlotNumber = &slot
+	}
+	return p
+}
+
+func baseAttrs(fork ssz.Fork) *PayloadAttributes {
+	a := &PayloadAttributes{
+		Timestamp: 1700000000, PrevRandao: gPrevRandao, SuggestedFeeRecipient: gFeeRecipient,
+	}
+	if fork >= ssz.ForkShapella {
+		a.Withdrawals = gWds
+	}
+	if fork >= ssz.ForkDencun {
+		root := gBeaconRoot
+		a.ParentBeaconBlockRoot = &root
+	}
+	if fork >= forkAmsterdam {
+		slot, tgl := uint64(42), uint64(30000000)
+		a.SlotNumber, a.TargetGasLimit = &slot, &tgl
+	}
+	return a
+}
+
+func baseBody(fork ssz.Fork) *ExecutionPayloadBody {
+	b := &ExecutionPayloadBody{Transactions: gTxs}
+	if fork >= ssz.ForkShapella {
+		b.Withdrawals = gWds
+	}
+	if fork >= forkAmsterdam {
+		b.BlockAccessList = gBAL
+	}
+	return b
+}
+
+func TestMonolithByteCompat(t *testing.T) {
+	cases := []struct {
+		name string
+		fork ssz.Fork
+		obj  ssz.Object
+		want string
+	}{
+		{"payload.paris", ssz.ForkParis, basePayload(ssz.ForkParis), goldenPayloadParis},
+		{"payload.shanghai", ssz.ForkShapella, basePayload(ssz.ForkShapella), goldenPayloadShanghai},
+		{"payload.cancun", ssz.ForkDencun, basePayload(ssz.ForkDencun), goldenPayloadCancun},
+		{"payload.amsterdam", forkAmsterdam, basePayload(forkAmsterdam), goldenPayloadAmsterdam},
+
+		{"attrs.paris", ssz.ForkParis, baseAttrs(ssz.ForkParis), goldenAttrsParis},
+		{"attrs.shanghai", ssz.ForkShapella, baseAttrs(ssz.ForkShapella), goldenAttrsShanghai},
+		{"attrs.cancun", ssz.ForkDencun, baseAttrs(ssz.ForkDencun), goldenAttrsCancun},
+		{"attrs.amsterdam", forkAmsterdam, baseAttrs(forkAmsterdam), goldenAttrsAmsterdam},
+
+		{"body.paris", ssz.ForkParis, baseBody(ssz.ForkParis), goldenBodyParis},
+		{"body.cancun", ssz.ForkDencun, baseBody(ssz.ForkDencun), goldenBodyCancun},
+		{"body.amsterdam", forkAmsterdam, baseBody(forkAmsterdam), goldenBodyAmsterdam},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := encodeHexOnFork(t, tc.obj, tc.fork)
+			if got != tc.want {
+				t.Errorf("byte mismatch for %s\nwant %s\n got %s", tc.name, tc.want, got)
+			}
+		})
+	}
+}

beacon/engine/ssz/convert.go

@@ -21,6 +21,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/holiman/uint256"
+	"github.com/karalabe/ssz"
 )
 
 // statusToEnum maps the JSON-RPC PayloadStatusV1.Status string to the SSZ
@@ -127,46 +128,68 @@ func withdrawalsToTypes(ws []*Withdrawal) []*types.Withdrawal {
 	return out
 }
 
-// PayloadAttributesAmsterdamFromEngine converts a JSON-RPC engine.PayloadAttributes
-// into its Amsterdam SSZ form. The caller is responsible for ensuring the
-// attributes carry every Amsterdam-required field.
-func PayloadAttributesAmsterdamFromEngine(a *engine.PayloadAttributes) *PayloadAttributesAmsterdam {
-	out := &PayloadAttributesAmsterdam{
+// PayloadAttributesFromEngine converts a JSON-RPC engine.PayloadAttributes into
+// the monolithic SSZ form for the given fork. Only the fields the fork's wire
+// shape carries are populated; the caller should pass the same fork to the
+// codec. target_gas_limit has no representation in engine.PayloadAttributes
+// today, so it is left nil for Amsterdam unless explicitly populated by the
+// caller afterwards.
+func PayloadAttributesFromEngine(a *engine.PayloadAttributes, fork ssz.Fork) *PayloadAttributes {
+	out := &PayloadAttributes{
 		Timestamp:             a.Timestamp,
 		PrevRandao:            a.Random,
 		SuggestedFeeRecipient: a.SuggestedFeeRecipient,
-		Withdrawals:           withdrawalsFromTypes(a.Withdrawals),
 	}
-	if a.BeaconRoot != nil {
-		out.ParentBeaconBlockRoot = *a.BeaconRoot
+	if fork >= ssz.ForkShapella {
+		out.Withdrawals = withdrawalsFromTypes(a.Withdrawals)
 	}
-	if a.SlotNumber != nil {
-		out.SlotNumber = *a.SlotNumber
+	if fork >= ssz.ForkDencun {
+		root := common.Hash{}
+		if a.BeaconRoot != nil {
+			root = *a.BeaconRoot
+		}
+		out.ParentBeaconBlockRoot = &root
+	}
+	if fork >= forkAmsterdam {
+		slot := uint64(0)
+		if a.SlotNumber != nil {
+			slot = *a.SlotNumber
+		}
+		out.SlotNumber = &slot
+		// target_gas_limit not carried by engine.PayloadAttributes; default 0.
+		tgl := uint64(0)
+		out.TargetGasLimit = &tgl
 	}
 	return out
 }
 
-// PayloadAttributesAmsterdamToEngine is the inverse of the From helper. The
-// target_gas_limit field has no representation in engine.PayloadAttributes
-// today and is dropped on the way down; the caller can fish it out of the SSZ
-// struct directly.
-func PayloadAttributesAmsterdamToEngine(a *PayloadAttributesAmsterdam) *engine.PayloadAttributes {
-	root := a.ParentBeaconBlockRoot
-	slot := a.SlotNumber
-	return &engine.PayloadAttributes{
+// PayloadAttributesToEngine is the inverse of PayloadAttributesFromEngine. The
+// target_gas_limit field has no representation in engine.PayloadAttributes and
+// is dropped; the caller can read it from the SSZ struct directly.
+func PayloadAttributesToEngine(a *PayloadAttributes) *engine.PayloadAttributes {
+	out := &engine.PayloadAttributes{
 		Timestamp:             a.Timestamp,
 		Random:                a.PrevRandao,
 		SuggestedFeeRecipient: a.SuggestedFeeRecipient,
 		Withdrawals:           withdrawalsToTypes(a.Withdrawals),
-		BeaconRoot:            &root,
-		SlotNumber:            &slot,
 	}
+	if a.ParentBeaconBlockRoot != nil {
+		root := *a.ParentBeaconBlockRoot
+		out.BeaconRoot = &root
+	}
+	if a.SlotNumber != nil {
+		slot := *a.SlotNumber
+		out.SlotNumber = &slot
+	}
+	return out
 }
 
-// ExecutionPayloadAmsterdamFromEngine converts an ExecutableData into the SSZ
-// Amsterdam payload shape. The block_access_list and slot_number fields are
-// expected to be present; missing values yield empty/zero defaults.
-func ExecutionPayloadAmsterdamFromEngine(d *engine.ExecutableData) *ExecutionPayloadAmsterdam {
+// ExecutionPayloadFromEngine converts an ExecutableData into the monolithic SSZ
+// payload for the given fork. Only the fork's active fields are populated so
+// the codec (driven by the same fork) and Validate(fork) stay consistent.
+// BlockAccessList is not yet wired through ExecutableData; the caller sets it
+// separately for Amsterdam.
+func ExecutionPayloadFromEngine(d *engine.ExecutableData, fork ssz.Fork) *ExecutionPayload {
 	var bloom [256]byte
 	copy(bloom[:], d.LogsBloom)
 	var fee *uint256.Int
@@ -174,7 +197,7 @@ func ExecutionPayloadAmsterdamFromEngine(d *engine.ExecutableData) *ExecutionPay
 		fee = new(uint256.Int)
 		fee.SetFromBig(d.BaseFeePerGas)
 	}
-	out := &ExecutionPayloadAmsterdam{
+	out := &ExecutionPayload{
 		ParentHash:    d.ParentHash,
 		FeeRecipient:  d.FeeRecipient,
 		StateRoot:     d.StateRoot,
@@ -189,48 +212,66 @@ func ExecutionPayloadAmsterdamFromEngine(d *engine.ExecutableData) *ExecutionPay
 		BaseFeePerGas: fee,
 		BlockHash:     d.BlockHash,
 		Transactions:  d.Transactions,
-		Withdrawals:   withdrawalsFromTypes(d.Withdrawals),
 	}
-	if d.BlobGasUsed != nil {
-		out.BlobGasUsed = *d.BlobGasUsed
+	if fork >= ssz.ForkShapella {
+		out.Withdrawals = withdrawalsFromTypes(d.Withdrawals)
 	}
-	if d.ExcessBlobGas != nil {
-		out.ExcessBlobGas = *d.ExcessBlobGas
+	if fork >= ssz.ForkDencun {
+		blobGas := uint64(0)
+		if d.BlobGasUsed != nil {
+			blobGas = *d.BlobGasUsed
+		}
+		excess := uint64(0)
+		if d.ExcessBlobGas != nil {
+			excess = *d.ExcessBlobGas
+		}
+		out.BlobGasUsed = &blobGas
+		out.ExcessBlobGas = &excess
 	}
-	if d.SlotNumber != nil {
-		out.SlotNumber = *d.SlotNumber
+	if fork >= forkAmsterdam {
+		slot := uint64(0)
+		if d.SlotNumber != nil {
+			slot = *d.SlotNumber
+		}
+		out.SlotNumber = &slot
 	}
-	// BlockAccessList is not yet wired through ExecutableData; the caller
-	// passes it as a separate field on the envelope when constructing the
-	// final wire form.
 	return out
 }
 
-// ExecutionPayloadAmsterdamToEngine is the inverse helper. The caller is
-// responsible for the BAL payload that ExecutableData doesn't yet carry.
-func ExecutionPayloadAmsterdamToEngine(p *ExecutionPayloadAmsterdam) *engine.ExecutableData {
+// ExecutionPayloadToEngine is the inverse helper. The caller is responsible for
+// the BAL payload that ExecutableData doesn't yet carry.
+func ExecutionPayloadToEngine(p *ExecutionPayload) *engine.ExecutableData {
 	bloom := append([]byte(nil), p.LogsBloom[:]...)
 	out := &engine.ExecutableData{
-		ParentHash:    p.ParentHash,
-		FeeRecipient:  p.FeeRecipient,
-		StateRoot:     p.StateRoot,
-		ReceiptsRoot:  p.ReceiptsRoot,
-		LogsBloom:     bloom,
-		Random:        p.PrevRandao,
-		Number:        p.BlockNumber,
-		GasLimit:      p.GasLimit,
-		GasUsed:       p.GasUsed,
-		Timestamp:     p.Timestamp,
-		ExtraData:     append([]byte(nil), p.ExtraData...),
-		BlockHash:     p.BlockHash,
-		Transactions:  p.Transactions,
-		Withdrawals:   withdrawalsToTypes(p.Withdrawals),
-		BlobGasUsed:   &p.BlobGasUsed,
-		ExcessBlobGas: &p.ExcessBlobGas,
-		SlotNumber:    &p.SlotNumber,
+		ParentHash:   p.ParentHash,
+		FeeRecipient: p.FeeRecipient,
+		StateRoot:    p.StateRoot,
+		ReceiptsRoot: p.ReceiptsRoot,
+		LogsBloom:    bloom,
+		Random:       p.PrevRandao,
+		Number:       p.BlockNumber,
+		GasLimit:     p.GasLimit,
+		GasUsed:      p.GasUsed,
+		Timestamp:    p.Timestamp,
+		ExtraData:    append([]byte(nil), p.ExtraData...),
+		BlockHash:    p.BlockHash,
+		Transactions: p.Transactions,
+		Withdrawals:  withdrawalsToTypes(p.Withdrawals),
 	}
 	if p.BaseFeePerGas != nil {
 		out.BaseFeePerGas = p.BaseFeePerGas.ToBig()
 	}
+	if p.BlobGasUsed != nil {
+		blobGas := *p.BlobGasUsed
+		out.BlobGasUsed = &blobGas
+	}
+	if p.ExcessBlobGas != nil {
+		excess := *p.ExcessBlobGas
+		out.ExcessBlobGas = &excess
+	}
+	if p.SlotNumber != nil {
+		slot := *p.SlotNumber
+		out.SlotNumber = &slot
+	}
 	return out
 }

beacon/engine/ssz/envelopes.go

@@ -25,7 +25,7 @@ import (
 // ExecutionPayloadEnvelopeAmsterdam is the request body of
 // POST /amsterdam/payloads.
 type ExecutionPayloadEnvelopeAmsterdam struct {
-	Payload               *ExecutionPayloadAmsterdam
+	Payload               *ExecutionPayload
 	ParentBeaconBlockRoot common.Hash
 	ExecutionRequests     [][]byte
 }
@@ -82,7 +82,7 @@ func (b *BlobsBundleV2) DefineSSZ(c *ssz.Codec) {
 
 // BuiltPayloadAmsterdam is the response of GET /amsterdam/payloads/{id}.
 type BuiltPayloadAmsterdam struct {
-	Payload               *ExecutionPayloadAmsterdam
+	Payload               *ExecutionPayload
 	BlockValue            *uint256.Int
 	BlobsBundle           *BlobsBundleV2
 	ExecutionRequests     [][]byte
@@ -120,7 +120,7 @@ func (p *BuiltPayloadAmsterdam) DefineSSZ(c *ssz.Codec) {
 // length 0 or 1 of the 16-byte Bitvector wrapper.
 type ForkchoiceUpdateAmsterdam struct {
 	ForkchoiceState   *ForkchoiceState
-	PayloadAttributes []*PayloadAttributesAmsterdam
+	PayloadAttributes []*PayloadAttributes
 	CustodyColumns    []*Bitvector128
 }
 

beacon/engine/ssz/forkmap.go

@@ -0,0 +1,60 @@
+// Copyright 2026 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ssz
+
+import (
+	"github.com/ethereum/go-ethereum/params/forks"
+	"github.com/karalabe/ssz"
+)
+
+// karalabe/ssz's Fork enum currently stops at Pectra (Prague). The monolith
+// types below gate fields with ForkFilter{Added,Removed}, and the codec only
+// performs ordered comparisons (`fork < Added`, `fork >= Removed`) against
+// Codec.fork. Any strictly-monotonic values placed after ForkPectra therefore
+// behave correctly. We define local aliases for the forks the library doesn't
+// name yet.
+//
+// IMPORTANT: these are only meaningful relative to one another and to the
+// library's own enum; never persist them. If a future karalabe/ssz release
+// adds Osaka/Amsterdam (or new forks between Pectra and these), revisit this
+// table so the ordering stays gap-consistent with the upstream enum.
+const (
+	forkOsaka     = ssz.ForkPectra + 1
+	forkAmsterdam = ssz.ForkPectra + 2
+)
+
+// ForkFor maps a geth params/forks.Fork onto the karalabe/ssz Fork value
+// the codec multiplexes on. The bool is false for forks that predate the
+// Engine API (and thus have no SSZ wire representation here).
+func ForkFor(f forks.Fork) (ssz.Fork, bool) {
+	switch f {
+	case forks.Paris:
+		return ssz.ForkParis, true
+	case forks.Shanghai:
+		return ssz.ForkShapella, true // EL Shanghai == CL Shapella
+	case forks.Cancun:
+		return ssz.ForkDencun, true // EL Cancun == CL Dencun
+	case forks.Prague:
+		return ssz.ForkPectra, true // EL Prague == CL Pectra
+	case forks.Osaka:
+		return forkOsaka, true
+	case forks.Amsterdam:
+		return forkAmsterdam, true
+	default:
+		return ssz.ForkUnknown, false
+	}
+}

beacon/engine/ssz/payload.go

@@ -0,0 +1,251 @@
+// Copyright 2026 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ssz
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/holiman/uint256"
+	"github.com/karalabe/ssz"
+)
+
+// Fork-boundary filters. Fields gated by these only participate in size,
+// encode, decode and hash when Codec.fork is in range — see forkmap.go for how
+// the geth fork maps onto ssz.Fork. Grouping the filters here (rather than one
+// flag per field) keeps the "field-group" structure visible: each filter is a
+// group boundary, and DefineSSZ applies it to every field the group owns.
+var (
+	// withdrawals group, introduced in Shanghai (Shapella).
+	fromShanghai = ssz.ForkFilter{Added: ssz.ForkShapella}
+	// blob-gas group, introduced in Cancun (Dencun).
+	fromCancun = ssz.ForkFilter{Added: ssz.ForkDencun}
+	// beacon-root attribute, introduced in Cancun (Dencun).
+	// (shares the Cancun boundary but kept named for clarity at call sites)
+	// bal + slot group, introduced in Amsterdam.
+	fromAmsterdam = ssz.ForkFilter{Added: forkAmsterdam}
+)
+
+// ExecutionPayload is the monolithic execution payload spanning every fork from
+// Paris onward. Fork-specific fields are gated with ...OnFork; the in-memory
+// struct is a superset and the fork passed to the codec selects the wire shape.
+//
+// Field groups (see the filter vars above):
+//   - base (Paris): ParentHash … Transactions
+//   - withdrawals (Shanghai): Withdrawals
+//   - blobGas (Cancun): BlobGasUsed, ExcessBlobGas
+//   - bal (Amsterdam): BlockAccessList, SlotNumber
+//
+// Gated scalars are pointers so the codec can distinguish "absent for this
+// fork" (nil) from "present and zero"; Validate(fork) enforces that invariant.
+type ExecutionPayload struct {
+	// base group (Paris)
+	ParentHash    common.Hash
+	FeeRecipient  common.Address
+	StateRoot     common.Hash
+	ReceiptsRoot  common.Hash
+	LogsBloom     [256]byte
+	PrevRandao    common.Hash
+	BlockNumber   uint64
+	GasLimit      uint64
+	GasUsed       uint64
+	Timestamp     uint64
+	ExtraData     []byte
+	BaseFeePerGas *uint256.Int
+	BlockHash     common.Hash
+	Transactions  [][]byte
+
+	// withdrawals group (Shanghai)
+	Withdrawals []*Withdrawal
+
+	// blobGas group (Cancun)
+	BlobGasUsed   *uint64
+	ExcessBlobGas *uint64
+
+	// bal group (Amsterdam)
+	BlockAccessList []byte
+	SlotNumber      *uint64
+}
+
+func (p *ExecutionPayload) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
+	// Fixed portion is fork-dependent; let the codec primitives account for it
+	// via the active fork rather than hand-summing magic byte constants.
+	var size uint32
+	// base fixed: 5 hashes(32) + addr(20) + bloom(256) + 4 u64s + uint256(32)
+	// + 2 offsets(extra, txs)(4)
+	size += 5*32 + 20 + 256 + 4*8 + 32 + 2*4
+	if siz.Fork() >= ssz.ForkShapella {
+		size += 4 // withdrawals offset
+	}
+	if siz.Fork() >= ssz.ForkDencun {
+		size += 2 * 8 // blob_gas_used, excess_blob_gas
+	}
+	if siz.Fork() >= forkAmsterdam {
+		size += 4 + 8 // block_access_list offset, slot_number
+	}
+	if fixed {
+		return size
+	}
+	size += ssz.SizeDynamicBytes(siz, p.ExtraData)
+	size += ssz.SizeSliceOfDynamicBytes(siz, p.Transactions)
+	if siz.Fork() >= ssz.ForkShapella {
+		size += ssz.SizeSliceOfStaticObjects(siz, p.Withdrawals)
+	}
+	if siz.Fork() >= forkAmsterdam {
+		size += ssz.SizeDynamicBytes(siz, p.BlockAccessList)
+	}
+	return size
+}
+
+func (p *ExecutionPayload) DefineSSZ(c *ssz.Codec) {
+	// --- offset phase ---
+	ssz.DefineStaticBytes(c, &p.ParentHash)
+	ssz.DefineStaticBytes(c, &p.FeeRecipient)
+	ssz.DefineStaticBytes(c, &p.StateRoot)
+	ssz.DefineStaticBytes(c, &p.ReceiptsRoot)
+	ssz.DefineStaticBytes(c, &p.LogsBloom)
+	ssz.DefineStaticBytes(c, &p.PrevRandao)
+	ssz.DefineUint64(c, &p.BlockNumber)
+	ssz.DefineUint64(c, &p.GasLimit)
+	ssz.DefineUint64(c, &p.GasUsed)
+	ssz.DefineUint64(c, &p.Timestamp)
+	ssz.DefineDynamicBytesOffset(c, &p.ExtraData, MaxExtraDataBytes)
+	ssz.DefineUint256(c, &p.BaseFeePerGas)
+	ssz.DefineStaticBytes(c, &p.BlockHash)
+	ssz.DefineSliceOfDynamicBytesOffset(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
+	ssz.DefineSliceOfStaticObjectsOffsetOnFork(c, &p.Withdrawals, MaxWithdrawalsPerPayload, fromShanghai)
+	ssz.DefineUint64PointerOnFork(c, &p.BlobGasUsed, fromCancun)
+	ssz.DefineUint64PointerOnFork(c, &p.ExcessBlobGas, fromCancun)
+	ssz.DefineDynamicBytesOffsetOnFork(c, &p.BlockAccessList, MaxBalBytes, fromAmsterdam)
+	ssz.DefineUint64PointerOnFork(c, &p.SlotNumber, fromAmsterdam)
+
+	// --- content phase ---
+	ssz.DefineDynamicBytesContent(c, &p.ExtraData, MaxExtraDataBytes)
+	ssz.DefineSliceOfDynamicBytesContent(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
+	ssz.DefineSliceOfStaticObjectsContentOnFork(c, &p.Withdrawals, MaxWithdrawalsPerPayload, fromShanghai)
+	ssz.DefineDynamicBytesContentOnFork(c, &p.BlockAccessList, MaxBalBytes, fromAmsterdam)
+}
+
+// Validate checks that the in-memory field set matches what the given fork's
+// wire shape carries: gated scalars must be present iff active, and absent
+// fields must be empty so the codec doesn't silently drop populated data.
+func (p *ExecutionPayload) Validate(fork ssz.Fork) error {
+	// withdrawals (Shanghai+)
+	if fork < ssz.ForkShapella && len(p.Withdrawals) > 0 {
+		return fmt.Errorf("withdrawals set but fork %d predates Shanghai", fork)
+	}
+	// blobGas (Cancun+)
+	if fork >= ssz.ForkDencun {
+		if p.BlobGasUsed == nil || p.ExcessBlobGas == nil {
+			return fmt.Errorf("blob gas fields required at fork %d", fork)
+		}
+	} else if p.BlobGasUsed != nil || p.ExcessBlobGas != nil {
+		return fmt.Errorf("blob gas fields set but fork %d predates Cancun", fork)
+	}
+	// bal + slot (Amsterdam+)
+	if fork >= forkAmsterdam {
+		if p.SlotNumber == nil {
+			return fmt.Errorf("slot_number required at fork %d", fork)
+		}
+	} else {
+		if len(p.BlockAccessList) > 0 {
+			return fmt.Errorf("block_access_list set but fork %d predates Amsterdam", fork)
+		}
+		if p.SlotNumber != nil {
+			return fmt.Errorf("slot_number set but fork %d predates Amsterdam", fork)
+		}
+	}
+	return nil
+}
+
+// PayloadAttributes is the monolithic build-attributes container spanning every
+// fork from Paris onward.
+//
+// Field groups:
+//   - base (Paris): Timestamp, PrevRandao, SuggestedFeeRecipient
+//   - withdrawals (Shanghai): Withdrawals
+//   - beaconRoot (Cancun): ParentBeaconBlockRoot
+//   - amsterdam (Amsterdam): SlotNumber, TargetGasLimit
+type PayloadAttributes struct {
+	Timestamp             uint64
+	PrevRandao            common.Hash
+	SuggestedFeeRecipient common.Address
+
+	Withdrawals []*Withdrawal // Shanghai+
+
+	ParentBeaconBlockRoot *common.Hash // Cancun+
+
+	SlotNumber     *uint64 // Amsterdam+
+	TargetGasLimit *uint64 // Amsterdam+
+}
+
+func (a *PayloadAttributes) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
+	// base fixed: timestamp(8) + randao(32) + fee_recipient(20)
+	var size uint32 = 8 + 32 + 20
+	if siz.Fork() >= ssz.ForkShapella {
+		size += 4 // withdrawals offset
+	}
+	if siz.Fork() >= ssz.ForkDencun {
+		size += 32 // parent_beacon_block_root
+	}
+	if siz.Fork() >= forkAmsterdam {
+		size += 8 + 8 // slot_number, target_gas_limit
+	}
+	if fixed {
+		return size
+	}
+	if siz.Fork() >= ssz.ForkShapella {
+		size += ssz.SizeSliceOfStaticObjects(siz, a.Withdrawals)
+	}
+	return size
+}
+
+func (a *PayloadAttributes) DefineSSZ(c *ssz.Codec) {
+	// offset phase
+	ssz.DefineUint64(c, &a.Timestamp)
+	ssz.DefineStaticBytes(c, &a.PrevRandao)
+	ssz.DefineStaticBytes(c, &a.SuggestedFeeRecipient)
+	ssz.DefineSliceOfStaticObjectsOffsetOnFork(c, &a.Withdrawals, MaxWithdrawalsPerPayload, fromShanghai)
+	ssz.DefineStaticBytesPointerOnFork(c, &a.ParentBeaconBlockRoot, fromCancun)
+	ssz.DefineUint64PointerOnFork(c, &a.SlotNumber, fromAmsterdam)
+	ssz.DefineUint64PointerOnFork(c, &a.TargetGasLimit, fromAmsterdam)
+
+	// content phase
+	ssz.DefineSliceOfStaticObjectsContentOnFork(c, &a.Withdrawals, MaxWithdrawalsPerPayload, fromShanghai)
+}
+
+// Validate enforces presence/absence of gated fields for the given fork.
+func (a *PayloadAttributes) Validate(fork ssz.Fork) error {
+	if fork < ssz.ForkShapella && len(a.Withdrawals) > 0 {
+		return fmt.Errorf("withdrawals set but fork %d predates Shanghai", fork)
+	}
+	if fork >= ssz.ForkDencun {
+		if a.ParentBeaconBlockRoot == nil {
+			return fmt.Errorf("parent_beacon_block_root required at fork %d", fork)
+		}
+	} else if a.ParentBeaconBlockRoot != nil {
+		return fmt.Errorf("parent_beacon_block_root set but fork %d predates Cancun", fork)
+	}
+	if fork >= forkAmsterdam {
+		if a.SlotNumber == nil || a.TargetGasLimit == nil {
+			return fmt.Errorf("slot_number and target_gas_limit required at fork %d", fork)
+		}
+	} else if a.SlotNumber != nil || a.TargetGasLimit != nil {
+		return fmt.Errorf("amsterdam attributes set but fork %d predates Amsterdam", fork)
+	}
+	return nil
+}

beacon/engine/ssz/payload_amsterdam.go

@@ -1,150 +0,0 @@
-// Copyright 2026 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package ssz
-
-import (
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/holiman/uint256"
-	"github.com/karalabe/ssz"
-)
-
-// ExecutionPayloadAmsterdam carries the Amsterdam-shaped payload over the wire.
-type ExecutionPayloadAmsterdam struct {
-	ParentHash      common.Hash
-	FeeRecipient    common.Address
-	StateRoot       common.Hash
-	ReceiptsRoot    common.Hash
-	LogsBloom       [256]byte
-	PrevRandao      common.Hash
-	BlockNumber     uint64
-	GasLimit        uint64
-	GasUsed         uint64
-	Timestamp       uint64
-	ExtraData       []byte
-	BaseFeePerGas   *uint256.Int
-	BlockHash       common.Hash
-	Transactions    [][]byte
-	Withdrawals     []*Withdrawal
-	BlobGasUsed     uint64
-	ExcessBlobGas   uint64
-	BlockAccessList []byte
-	SlotNumber      uint64
-}
-
-func (p *ExecutionPayloadAmsterdam) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	// 5 hashes(32) + addr(20) + bloom(256) + 4 u64s + uint256(32)
-	// + 4 offsets(4) + 2 u64s (blob gas) + u64 (slot) = 540
-	size := uint32(5*32 + 20 + 256 + 4*8 + 32 + 4*4 + 2*8 + 8)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeDynamicBytes(siz, p.ExtraData)
-	size += ssz.SizeSliceOfDynamicBytes(siz, p.Transactions)
-	size += ssz.SizeSliceOfStaticObjects(siz, p.Withdrawals)
-	size += ssz.SizeDynamicBytes(siz, p.BlockAccessList)
-	return size
-}
-
-func (p *ExecutionPayloadAmsterdam) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineStaticBytes(c, &p.ParentHash)
-	ssz.DefineStaticBytes(c, &p.FeeRecipient)
-	ssz.DefineStaticBytes(c, &p.StateRoot)
-	ssz.DefineStaticBytes(c, &p.ReceiptsRoot)
-	ssz.DefineStaticBytes(c, &p.LogsBloom)
-	ssz.DefineStaticBytes(c, &p.PrevRandao)
-	ssz.DefineUint64(c, &p.BlockNumber)
-	ssz.DefineUint64(c, &p.GasLimit)
-	ssz.DefineUint64(c, &p.GasUsed)
-	ssz.DefineUint64(c, &p.Timestamp)
-	ssz.DefineDynamicBytesOffset(c, &p.ExtraData, MaxExtraDataBytes)
-	ssz.DefineUint256(c, &p.BaseFeePerGas)
-	ssz.DefineStaticBytes(c, &p.BlockHash)
-	ssz.DefineSliceOfDynamicBytesOffset(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsOffset(c, &p.Withdrawals, MaxWithdrawalsPerPayload)
-	ssz.DefineUint64(c, &p.BlobGasUsed)
-	ssz.DefineUint64(c, &p.ExcessBlobGas)
-	ssz.DefineDynamicBytesOffset(c, &p.BlockAccessList, MaxBalBytes)
-	ssz.DefineUint64(c, &p.SlotNumber)
-
-	ssz.DefineDynamicBytesContent(c, &p.ExtraData, MaxExtraDataBytes)
-	ssz.DefineSliceOfDynamicBytesContent(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsContent(c, &p.Withdrawals, MaxWithdrawalsPerPayload)
-	ssz.DefineDynamicBytesContent(c, &p.BlockAccessList, MaxBalBytes)
-}
-
-// PayloadAttributesAmsterdam carries Amsterdam build attributes.
-type PayloadAttributesAmsterdam struct {
-	Timestamp             uint64
-	PrevRandao            common.Hash
-	SuggestedFeeRecipient common.Address
-	Withdrawals           []*Withdrawal
-	ParentBeaconBlockRoot common.Hash
-	SlotNumber            uint64
-	TargetGasLimit        uint64
-}
-
-func (a *PayloadAttributesAmsterdam) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	// timestamp(8) + randao(32) + fee_recipient(20) + offset(4)
-	// + parent_beacon_block_root(32) + slot(8) + target_gas(8) = 112
-	size := uint32(112)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeSliceOfStaticObjects(siz, a.Withdrawals)
-	return size
-}
-
-func (a *PayloadAttributesAmsterdam) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineUint64(c, &a.Timestamp)
-	ssz.DefineStaticBytes(c, &a.PrevRandao)
-	ssz.DefineStaticBytes(c, &a.SuggestedFeeRecipient)
-	ssz.DefineSliceOfStaticObjectsOffset(c, &a.Withdrawals, MaxWithdrawalsPerPayload)
-	ssz.DefineStaticBytes(c, &a.ParentBeaconBlockRoot)
-	ssz.DefineUint64(c, &a.SlotNumber)
-	ssz.DefineUint64(c, &a.TargetGasLimit)
-
-	ssz.DefineSliceOfStaticObjectsContent(c, &a.Withdrawals, MaxWithdrawalsPerPayload)
-}
-
-// ExecutionPayloadBodyAmsterdam mirrors the /amsterdam/bodies response shape.
-type ExecutionPayloadBodyAmsterdam struct {
-	Transactions    [][]byte
-	Withdrawals     []*Withdrawal
-	BlockAccessList []byte
-}
-
-func (b *ExecutionPayloadBodyAmsterdam) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	// 3 offsets
-	size := uint32(12)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeSliceOfDynamicBytes(siz, b.Transactions)
-	size += ssz.SizeSliceOfStaticObjects(siz, b.Withdrawals)
-	size += ssz.SizeDynamicBytes(siz, b.BlockAccessList)
-	return size
-}
-
-func (b *ExecutionPayloadBodyAmsterdam) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineSliceOfDynamicBytesOffset(c, &b.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsOffset(c, &b.Withdrawals, MaxWithdrawalsPerPayload)
-	ssz.DefineDynamicBytesOffset(c, &b.BlockAccessList, MaxBalBytes)
-
-	ssz.DefineSliceOfDynamicBytesContent(c, &b.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsContent(c, &b.Withdrawals, MaxWithdrawalsPerPayload)
-	ssz.DefineDynamicBytesContent(c, &b.BlockAccessList, MaxBalBytes)
-}

beacon/engine/ssz/payload_forks.go

@@ -1,185 +0,0 @@
-// Copyright 2026 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package ssz
-
-import (
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/holiman/uint256"
-	"github.com/karalabe/ssz"
-)
-
-// ExecutionPayloadCancun is the Cancun/Prague/Osaka payload shape.
-// Prague and Osaka don't change the inner payload — execution_requests
-// and the BlobsBundle revision change at the envelope level, not here.
-type ExecutionPayloadCancun struct {
-	ParentHash    common.Hash
-	FeeRecipient  common.Address
-	StateRoot     common.Hash
-	ReceiptsRoot  common.Hash
-	LogsBloom     [256]byte
-	PrevRandao    common.Hash
-	BlockNumber   uint64
-	GasLimit      uint64
-	GasUsed       uint64
-	Timestamp     uint64
-	ExtraData     []byte
-	BaseFeePerGas *uint256.Int
-	BlockHash     common.Hash
-	Transactions  [][]byte
-	Withdrawals   []*Withdrawal
-	BlobGasUsed   uint64
-	ExcessBlobGas uint64
-}
-
-func (p *ExecutionPayloadCancun) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	// 5 hashes(32) + addr(20) + bloom(256) + 4 u64s + uint256(32)
-	// + 3 offsets(4) + 2 u64s (blob gas) = 528
-	size := uint32(5*32 + 20 + 256 + 4*8 + 32 + 3*4 + 2*8)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeDynamicBytes(siz, p.ExtraData)
-	size += ssz.SizeSliceOfDynamicBytes(siz, p.Transactions)
-	size += ssz.SizeSliceOfStaticObjects(siz, p.Withdrawals)
-	return size
-}
-
-func (p *ExecutionPayloadCancun) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineStaticBytes(c, &p.ParentHash)
-	ssz.DefineStaticBytes(c, &p.FeeRecipient)
-	ssz.DefineStaticBytes(c, &p.StateRoot)
-	ssz.DefineStaticBytes(c, &p.ReceiptsRoot)
-	ssz.DefineStaticBytes(c, &p.LogsBloom)
-	ssz.DefineStaticBytes(c, &p.PrevRandao)
-	ssz.DefineUint64(c, &p.BlockNumber)
-	ssz.DefineUint64(c, &p.GasLimit)
-	ssz.DefineUint64(c, &p.GasUsed)
-	ssz.DefineUint64(c, &p.Timestamp)
-	ssz.DefineDynamicBytesOffset(c, &p.ExtraData, MaxExtraDataBytes)
-	ssz.DefineUint256(c, &p.BaseFeePerGas)
-	ssz.DefineStaticBytes(c, &p.BlockHash)
-	ssz.DefineSliceOfDynamicBytesOffset(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsOffset(c, &p.Withdrawals, MaxWithdrawalsPerPayload)
-	ssz.DefineUint64(c, &p.BlobGasUsed)
-	ssz.DefineUint64(c, &p.ExcessBlobGas)
-
-	ssz.DefineDynamicBytesContent(c, &p.ExtraData, MaxExtraDataBytes)
-	ssz.DefineSliceOfDynamicBytesContent(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsContent(c, &p.Withdrawals, MaxWithdrawalsPerPayload)
-}
-
-// ExecutionPayloadShanghai is the Shanghai payload shape (Cancun minus blob gas).
-type ExecutionPayloadShanghai struct {
-	ParentHash    common.Hash
-	FeeRecipient  common.Address
-	StateRoot     common.Hash
-	ReceiptsRoot  common.Hash
-	LogsBloom     [256]byte
-	PrevRandao    common.Hash
-	BlockNumber   uint64
-	GasLimit      uint64
-	GasUsed       uint64
-	Timestamp     uint64
-	ExtraData     []byte
-	BaseFeePerGas *uint256.Int
-	BlockHash     common.Hash
-	Transactions  [][]byte
-	Withdrawals   []*Withdrawal
-}
-
-func (p *ExecutionPayloadShanghai) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	// 5 hashes(32) + addr(20) + bloom(256) + 4 u64s + uint256(32) + 3 offsets(4) = 512
-	size := uint32(5*32 + 20 + 256 + 4*8 + 32 + 3*4)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeDynamicBytes(siz, p.ExtraData)
-	size += ssz.SizeSliceOfDynamicBytes(siz, p.Transactions)
-	size += ssz.SizeSliceOfStaticObjects(siz, p.Withdrawals)
-	return size
-}
-
-func (p *ExecutionPayloadShanghai) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineStaticBytes(c, &p.ParentHash)
-	ssz.DefineStaticBytes(c, &p.FeeRecipient)
-	ssz.DefineStaticBytes(c, &p.StateRoot)
-	ssz.DefineStaticBytes(c, &p.ReceiptsRoot)
-	ssz.DefineStaticBytes(c, &p.LogsBloom)
-	ssz.DefineStaticBytes(c, &p.PrevRandao)
-	ssz.DefineUint64(c, &p.BlockNumber)
-	ssz.DefineUint64(c, &p.GasLimit)
-	ssz.DefineUint64(c, &p.GasUsed)
-	ssz.DefineUint64(c, &p.Timestamp)
-	ssz.DefineDynamicBytesOffset(c, &p.ExtraData, MaxExtraDataBytes)
-	ssz.DefineUint256(c, &p.BaseFeePerGas)
-	ssz.DefineStaticBytes(c, &p.BlockHash)
-	ssz.DefineSliceOfDynamicBytesOffset(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsOffset(c, &p.Withdrawals, MaxWithdrawalsPerPayload)
-
-	ssz.DefineDynamicBytesContent(c, &p.ExtraData, MaxExtraDataBytes)
-	ssz.DefineSliceOfDynamicBytesContent(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-	ssz.DefineSliceOfStaticObjectsContent(c, &p.Withdrawals, MaxWithdrawalsPerPayload)
-}
-
-// ExecutionPayloadParis is the original Bellatrix/Paris payload shape.
-type ExecutionPayloadParis struct {
-	ParentHash    common.Hash
-	FeeRecipient  common.Address
-	StateRoot     common.Hash
-	ReceiptsRoot  common.Hash
-	LogsBloom     [256]byte
-	PrevRandao    common.Hash
-	BlockNumber   uint64
-	GasLimit      uint64
-	GasUsed       uint64
-	Timestamp     uint64
-	ExtraData     []byte
-	BaseFeePerGas *uint256.Int
-	BlockHash     common.Hash
-	Transactions  [][]byte
-}
-
-func (p *ExecutionPayloadParis) SizeSSZ(siz *ssz.Sizer, fixed bool) uint32 {
-	// 5 hashes(32) + addr(20) + bloom(256) + 4 u64s + uint256(32) + 2 offsets(4) = 508
-	size := uint32(5*32 + 20 + 256 + 4*8 + 32 + 2*4)
-	if fixed {
-		return size
-	}
-	size += ssz.SizeDynamicBytes(siz, p.ExtraData)
-	size += ssz.SizeSliceOfDynamicBytes(siz, p.Transactions)
-	return size
-}
-
-func (p *ExecutionPayloadParis) DefineSSZ(c *ssz.Codec) {
-	ssz.DefineStaticBytes(c, &p.ParentHash)
-	ssz.DefineStaticBytes(c, &p.FeeRecipient)
-	ssz.DefineStaticBytes(c, &p.StateRoot)
-	ssz.DefineStaticBytes(c, &p.ReceiptsRoot)
-	ssz.DefineStaticBytes(c, &p.LogsBloom)
-	ssz.DefineStaticBytes(c, &p.PrevRandao)
-	ssz.DefineUint64(c, &p.BlockNumber)
-	ssz.DefineUint64(c, &p.GasLimit)
-	ssz.DefineUint64(c, &p.GasUsed)
-	ssz.DefineUint64(c, &p.Timestamp)
-	ssz.DefineDynamicBytesOffset(c, &p.ExtraData, MaxExtraDataBytes)
-	ssz.DefineUint256(c, &p.BaseFeePerGas)
-	ssz.DefineStaticBytes(c, &p.BlockHash)
-	ssz.DefineSliceOfDynamicBytesOffset(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-
-	ssz.DefineDynamicBytesContent(c, &p.ExtraData, MaxExtraDataBytes)
-	ssz.DefineSliceOfDynamicBytesContent(c, &p.Transactions, MaxTxsPerPayload, MaxBytesPerTx)
-}

beacon/engine/ssz/roundtrip_test.go

@@ -77,8 +77,30 @@ func TestPayloadStatusRoundtrip(t *testing.T) {
 	encDec(t, &PayloadStatus{Status: StatusSyncing}, func() *PayloadStatus { return new(PayloadStatus) })
 }
 
+// encDecOnFork is the fork-aware sibling of encDec for monolith types.
+func encDecOnFork[T ssz.Object](t *testing.T, obj T, fork ssz.Fork, newEmpty func() T) {
+	t.Helper()
+	size := ssz.SizeOnFork(obj, fork)
+	buf := make([]byte, size)
+	if err := ssz.EncodeToBytesOnFork(buf, obj, fork); err != nil {
+		t.Fatalf("encode: %v", err)
+	}
+	got := newEmpty()
+	if err := ssz.DecodeFromBytesOnFork(buf, got, fork); err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	rebuf := make([]byte, ssz.SizeOnFork(got, fork))
+	if err := ssz.EncodeToBytesOnFork(rebuf, got, fork); err != nil {
+		t.Fatalf("re-encode: %v", err)
+	}
+	if !reflect.DeepEqual(buf, rebuf) {
+		t.Fatalf("round-trip mismatch\nwant bytes: %x\n got bytes: %x", buf, rebuf)
+	}
+}
+
 func TestExecutionPayloadAmsterdamRoundtrip(t *testing.T) {
-	p := &ExecutionPayloadAmsterdam{
+	blob, excess, slot := uint64(131072), uint64(0), uint64(200)
+	p := &ExecutionPayload{
 		ParentHash:      common.Hash{0x11},
 		FeeRecipient:    common.Address{0x22},
 		StateRoot:       common.Hash{0x33},
@@ -93,26 +115,28 @@ func TestExecutionPayloadAmsterdamRoundtrip(t *testing.T) {
 		BlockHash:       common.Hash{0x66},
 		Transactions:    [][]byte{{0x02, 0x03}, {0x04}},
 		Withdrawals:     []*Withdrawal{{Index: 1, ValidatorIndex: 2, Amount: 3}},
-		BlobGasUsed:     131072,
-		ExcessBlobGas:   0,
+		BlobGasUsed:     &blob,
+		ExcessBlobGas:   &excess,
 		BlockAccessList: []byte{0xde, 0xad, 0xbe, 0xef},
-		SlotNumber:      200,
+		SlotNumber:      &slot,
 	}
-	encDec(t, p, func() *ExecutionPayloadAmsterdam { return new(ExecutionPayloadAmsterdam) })
+	encDecOnFork(t, p, forkAmsterdam, func() *ExecutionPayload { return new(ExecutionPayload) })
 }
 
 func TestForkchoiceUpdateAmsterdamRoundtrip(t *testing.T) {
 	// With payload_attributes and custody_columns present.
 	bits := &Bitvector128{Bytes: make([]byte, CellsPerExtBlob/8)}
 	bits.Bytes[0] = 0x01
-	attrs := &PayloadAttributesAmsterdam{
+	root := common.Hash{0x77}
+	slot, tgl := uint64(42), uint64(30000000)
+	attrs := &PayloadAttributes{
 		Timestamp:             1700000000,
 		PrevRandao:            common.Hash{0x55},
 		SuggestedFeeRecipient: common.Address{0x66},
 		Withdrawals:           []*Withdrawal{},
-		ParentBeaconBlockRoot: common.Hash{0x77},
-		SlotNumber:            42,
-		TargetGasLimit:        30000000,
+		ParentBeaconBlockRoot: &root,
+		SlotNumber:            &slot,
+		TargetGasLimit:        &tgl,
 	}
 	fcu := &ForkchoiceUpdateAmsterdam{
 		ForkchoiceState: &ForkchoiceState{
@@ -120,10 +144,10 @@ func TestForkchoiceUpdateAmsterdamRoundtrip(t *testing.T) {
 			SafeBlockHash:      common.Hash{0xbb},
 			FinalizedBlockHash: common.Hash{0xcc},
 		},
-		PayloadAttributes: []*PayloadAttributesAmsterdam{attrs},
+		PayloadAttributes: []*PayloadAttributes{attrs},
 		CustodyColumns:    []*Bitvector128{bits},
 	}
-	encDec(t, fcu, func() *ForkchoiceUpdateAmsterdam { return new(ForkchoiceUpdateAmsterdam) })
+	encDecOnFork(t, fcu, forkAmsterdam, func() *ForkchoiceUpdateAmsterdam { return new(ForkchoiceUpdateAmsterdam) })
 
 	// Without optionals.
 	bare := &ForkchoiceUpdateAmsterdam{
@@ -131,5 +155,5 @@ func TestForkchoiceUpdateAmsterdamRoundtrip(t *testing.T) {
 			HeadBlockHash: common.Hash{0xdd},
 		},
 	}
-	encDec(t, bare, func() *ForkchoiceUpdateAmsterdam { return new(ForkchoiceUpdateAmsterdam) })
+	encDecOnFork(t, bare, forkAmsterdam, func() *ForkchoiceUpdateAmsterdam { return new(ForkchoiceUpdateAmsterdam) })
 }

beacon/engine/ssz/validate_test.go

@@ -0,0 +1,120 @@
+// Copyright 2026 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ssz
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/karalabe/ssz"
+)
+
+func u64p(v uint64) *uint64 { return &v }
+
+func TestExecutionPayloadValidate(t *testing.T) {
+	tests := []struct {
+		name    string
+		fork    ssz.Fork
+		mutate  func(*ExecutionPayload)
+		wantErr bool
+	}{
+		{"paris ok", ssz.ForkParis, func(p *ExecutionPayload) {}, false},
+		{"paris with withdrawals", ssz.ForkParis, func(p *ExecutionPayload) {
+			p.Withdrawals = []*Withdrawal{{}}
+		}, true},
+		{"paris with blob gas", ssz.ForkParis, func(p *ExecutionPayload) {
+			p.BlobGasUsed = u64p(1)
+		}, true},
+		{"cancun missing blob gas", ssz.ForkDencun, func(p *ExecutionPayload) {
+			p.BlobGasUsed, p.ExcessBlobGas = nil, nil
+		}, true},
+		{"cancun ok", ssz.ForkDencun, func(p *ExecutionPayload) {
+			p.BlobGasUsed, p.ExcessBlobGas = u64p(0), u64p(0)
+		}, false},
+		{"cancun with bal", ssz.ForkDencun, func(p *ExecutionPayload) {
+			p.BlobGasUsed, p.ExcessBlobGas = u64p(0), u64p(0)
+			p.BlockAccessList = []byte{0x01}
+		}, true},
+		{"amsterdam missing slot", forkAmsterdam, func(p *ExecutionPayload) {
+			p.BlobGasUsed, p.ExcessBlobGas = u64p(0), u64p(0)
+			p.SlotNumber = nil
+		}, true},
+		{"amsterdam ok", forkAmsterdam, func(p *ExecutionPayload) {
+			p.BlobGasUsed, p.ExcessBlobGas = u64p(0), u64p(0)
+			p.SlotNumber = u64p(1)
+			p.BlockAccessList = []byte{0x01}
+		}, false},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			p := &ExecutionPayload{}
+			tc.mutate(p)
+			err := p.Validate(tc.fork)
+			if (err != nil) != tc.wantErr {
+				t.Fatalf("Validate(%d) err=%v wantErr=%v", tc.fork, err, tc.wantErr)
+			}
+		})
+	}
+}
+
+func TestPayloadAttributesValidate(t *testing.T) {
+	root := common.Hash{0x77}
+	tests := []struct {
+		name    string
+		fork    ssz.Fork
+		mutate  func(*PayloadAttributes)
+		wantErr bool
+	}{
+		{"paris ok", ssz.ForkParis, func(a *PayloadAttributes) {}, false},
+		{"cancun missing beacon root", ssz.ForkDencun, func(a *PayloadAttributes) {}, true},
+		{"cancun ok", ssz.ForkDencun, func(a *PayloadAttributes) {
+			a.ParentBeaconBlockRoot = &root
+		}, false},
+		{"paris with beacon root", ssz.ForkParis, func(a *PayloadAttributes) {
+			a.ParentBeaconBlockRoot = &root
+		}, true},
+		{"amsterdam missing slot/tgl", forkAmsterdam, func(a *PayloadAttributes) {
+			a.ParentBeaconBlockRoot = &root
+		}, true},
+		{"amsterdam ok", forkAmsterdam, func(a *PayloadAttributes) {
+			a.ParentBeaconBlockRoot = &root
+			a.SlotNumber, a.TargetGasLimit = u64p(1), u64p(2)
+		}, false},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			a := &PayloadAttributes{}
+			tc.mutate(a)
+			err := a.Validate(tc.fork)
+			if (err != nil) != tc.wantErr {
+				t.Fatalf("Validate(%d) err=%v wantErr=%v", tc.fork, err, tc.wantErr)
+			}
+		})
+	}
+}
+
+func TestExecutionPayloadBodyValidate(t *testing.T) {
+	if err := (&ExecutionPayloadBody{Withdrawals: []*Withdrawal{{}}}).Validate(ssz.ForkParis); err == nil {
+		t.Error("expected error for withdrawals at Paris")
+	}
+	if err := (&ExecutionPayloadBody{BlockAccessList: []byte{1}}).Validate(ssz.ForkDencun); err == nil {
+		t.Error("expected error for bal at Cancun")
+	}
+	if err := (&ExecutionPayloadBody{Withdrawals: []*Withdrawal{{}}}).Validate(forkAmsterdam); err != nil {
+		t.Errorf("unexpected error at Amsterdam: %v", err)
+	}
+}

eth/engineapi/blobs.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/beacon/engine"
 	sszt "github.com/ethereum/go-ethereum/beacon/engine/ssz"
+	"github.com/karalabe/ssz"
 )
 
 // handleBlobs dispatches POST /engine/v2/blobs/v{1,2,3,4}.
@@ -46,7 +47,7 @@ func (rt *Router) handleBlobs(w http.ResponseWriter, r *http.Request, suffix str
 
 func (rt *Router) handleBlobsV1(w http.ResponseWriter, r *http.Request) {
 	req := new(sszt.BlobsVersionedHashesRequest)
-	if !readSSZRequest(w, r, req, maxPayloadBytes) {
+	if !readSSZRequest(w, r, req, ssz.ForkUnknown, maxPayloadBytes) {
 		return
 	}
 	if len(req.VersionedHashes) > sszt.MaxBlobsRequest {
@@ -69,14 +70,14 @@ func (rt *Router) handleBlobsV1(w http.ResponseWriter, r *http.Request) {
 		}
 		resp.Entries[i] = e
 	}
-	writeSSZResponse(w, resp)
+	writeSSZResponse(w, resp, ssz.ForkUnknown)
 }
 
 // handleBlobsV2 serves both /v2 (all-or-nothing) and /v3 (partial). The
 // allowPartial flag selects between them.
 func (rt *Router) handleBlobsV2(w http.ResponseWriter, r *http.Request, allowPartial bool) {
 	req := new(sszt.BlobsVersionedHashesRequest)
-	if !readSSZRequest(w, r, req, maxPayloadBytes) {
+	if !readSSZRequest(w, r, req, ssz.ForkUnknown, maxPayloadBytes) {
 		return
 	}
 	if len(req.VersionedHashes) > sszt.MaxBlobsRequest {
@@ -106,7 +107,7 @@ func (rt *Router) handleBlobsV2(w http.ResponseWriter, r *http.Request, allowPar
 		}
 		resp.Entries[i] = e
 	}
-	writeSSZResponse(w, resp)
+	writeSSZResponse(w, resp, ssz.ForkUnknown)
 }
 
 // handleBlobsV4 implements POST /engine/v2/blobs/v4 (cell-range selection).
@@ -115,7 +116,7 @@ func (rt *Router) handleBlobsV2(w http.ResponseWriter, r *http.Request, allowPar
 // request body and the indices_bitarray length to keep the wire contract live.
 func (rt *Router) handleBlobsV4(w http.ResponseWriter, r *http.Request) {
 	req := new(sszt.BlobsV4Request)
-	if !readSSZRequest(w, r, req, maxPayloadBytes) {
+	if !readSSZRequest(w, r, req, ssz.ForkUnknown, maxPayloadBytes) {
 		return
 	}
 	if req.IndicesBitarray == nil || len(req.IndicesBitarray.Bytes) != sszt.CellsPerExtBlob/8 {

eth/engineapi/bodies.go

@@ -23,16 +23,17 @@ import (
 	sszt "github.com/ethereum/go-ethereum/beacon/engine/ssz"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/params/forks"
+	"github.com/karalabe/ssz"
 )
 
 // handleBodiesByHash implements POST /engine/v2/{fork}/bodies/hash.
 func (rt *Router) handleBodiesByHash(w http.ResponseWriter, r *http.Request, fork forks.Fork) {
-	if fork != forks.Amsterdam {
-		writeProblem(w, http.StatusBadRequest, ErrUnsupportedFork, "")
+	sf, ok := resolveFork(w, fork, forks.Paris)
+	if !ok {
 		return
 	}
 	req := new(sszt.BodiesByHashRequest)
-	if !readSSZRequest(w, r, req, maxPayloadBytes) {
+	if !readSSZRequest(w, r, req, sf, maxPayloadBytes) {
 		return
 	}
 	if len(req.BlockHashes) > sszt.MaxBodiesRequest {
@@ -40,13 +41,13 @@ func (rt *Router) handleBodiesByHash(w http.ResponseWriter, r *http.Request, for
 		return
 	}
 	bodies, timestamps := rt.backend.BodiesByHash(req.BlockHashes)
-	writeSSZResponse(w, buildBodiesResponseAmsterdam(rt.backend, fork, bodies, timestamps))
+	writeSSZResponse(w, buildBodiesResponse(rt.backend, fork, sf, bodies, timestamps), sf)
 }
 
 // handleBodiesByRange implements GET /engine/v2/{fork}/bodies?from=&count=.
 func (rt *Router) handleBodiesByRange(w http.ResponseWriter, r *http.Request, fork forks.Fork) {
-	if fork != forks.Amsterdam {
-		writeProblem(w, http.StatusBadRequest, ErrUnsupportedFork, "")
+	sf, ok := resolveFork(w, fork, forks.Paris)
+	if !ok {
 		return
 	}
 	q := r.URL.Query()
@@ -65,43 +66,49 @@ func (rt *Router) handleBodiesByRange(w http.ResponseWriter, r *http.Request, fo
 		return
 	}
 	bodies, timestamps := rt.backend.BodiesByRange(from, count)
-	writeSSZResponse(w, buildBodiesResponseAmsterdam(rt.backend, fork, bodies, timestamps))
+	writeSSZResponse(w, buildBodiesResponse(rt.backend, fork, sf, bodies, timestamps), sf)
 }
 
-// buildBodiesResponseAmsterdam assembles a BodiesResponseAmsterdam, marking
-// out-of-era blocks as available=false per the URL fork window.
-func buildBodiesResponseAmsterdam(b Backend, fork forks.Fork, bodies []*types.Body, ts []uint64) *sszt.BodiesResponseAmsterdam {
-	out := &sszt.BodiesResponseAmsterdam{
-		Entries: make([]*sszt.BodyEntryAmsterdam, len(bodies)),
+// buildBodiesResponse assembles a BodiesResponse for the given fork, marking
+// out-of-era blocks as available=false per the URL fork window. The body shape
+// is fork-driven by the codec; bodyToSSZ populates the superset and the codec
+// emits only the fork's active fields.
+func buildBodiesResponse(b Backend, fork forks.Fork, sf ssz.Fork, bodies []*types.Body, ts []uint64) *sszt.BodiesResponse {
+	out := &sszt.BodiesResponse{
+		Entries: make([]*sszt.BodyEntry, len(bodies)),
 	}
 	for i, body := range bodies {
-		entry := &sszt.BodyEntryAmsterdam{Body: new(sszt.ExecutionPayloadBodyAmsterdam)}
+		entry := &sszt.BodyEntry{Body: new(sszt.ExecutionPayloadBody)}
 		if body != nil && b.ForkFromTimestamp(ts[i]) == fork {
 			entry.Available = true
-			entry.Body = bodyToAmsterdamSSZ(body)
+			entry.Body = bodyToSSZ(body, sf)
 		}
 		out.Entries[i] = entry
 	}
 	return out
 }
 
-// bodyToAmsterdamSSZ flattens a *types.Body into the Amsterdam body shape.
-func bodyToAmsterdamSSZ(body *types.Body) *sszt.ExecutionPayloadBodyAmsterdam {
-	out := &sszt.ExecutionPayloadBodyAmsterdam{
+// bodyToSSZ flattens a *types.Body into the monolithic body shape. Withdrawals
+// are only attached from Shanghai on, matching the fork's wire shape.
+func bodyToSSZ(body *types.Body, sf ssz.Fork) *sszt.ExecutionPayloadBody {
+	out := &sszt.ExecutionPayloadBody{
 		Transactions: make([][]byte, len(body.Transactions)),
-		Withdrawals:  make([]*sszt.Withdrawal, len(body.Withdrawals)),
 	}
 	for i, tx := range body.Transactions {
 		out.Transactions[i], _ = tx.MarshalBinary()
 	}
-	for i, w := range body.Withdrawals {
-		out.Withdrawals[i] = &sszt.Withdrawal{
-			Index:          w.Index,
-			ValidatorIndex: w.Validator,
-			Address:        w.Address,
-			Amount:         w.Amount,
+	if sf >= ssz.ForkShapella {
+		out.Withdrawals = make([]*sszt.Withdrawal, len(body.Withdrawals))
+		for i, w := range body.Withdrawals {
+			out.Withdrawals[i] = &sszt.Withdrawal{
+				Index:          w.Index,
+				ValidatorIndex: w.Validator,
+				Address:        w.Address,
+				Amount:         w.Amount,
+			}
 		}
 	}
-	// BlockAccessList is not yet on types.Body; once wired through, copy here.
+	// BlockAccessList is not yet on types.Body; once wired through, copy here
+	// (gated by sf >= forkAmsterdam).
 	return out
 }

eth/engineapi/forkchoice.go

@@ -26,12 +26,14 @@ import (
 
 // handleForkchoice implements POST /engine/v2/{fork}/forkchoice.
 func (rt *Router) handleForkchoice(w http.ResponseWriter, r *http.Request, fork forks.Fork) {
-	if fork != forks.Amsterdam {
-		writeProblem(w, http.StatusBadRequest, ErrUnsupportedFork, "")
+	// The execution-apis spec currently only defines the forkchoice envelope
+	// for Amsterdam; the inner attributes shape is fork-driven by the codec.
+	sf, ok := resolveFork(w, fork, forks.Amsterdam)
+	if !ok {
 		return
 	}
 	fcu := new(sszt.ForkchoiceUpdateAmsterdam)
-	if !readSSZRequest(w, r, fcu, maxPayloadBytes) {
+	if !readSSZRequest(w, r, fcu, sf, maxPayloadBytes) {
 		return
 	}
 	if err := fcu.Validate(); err != nil {
@@ -41,17 +43,21 @@ func (rt *Router) handleForkchoice(w http.ResponseWriter, r *http.Request, fork
 	state := sszt.ForkchoiceStateToV1(fcu.ForkchoiceState)
 	var attrs *engine.PayloadAttributes
 	if len(fcu.PayloadAttributes) == 1 {
-		ssz := fcu.PayloadAttributes[0]
+		attr := fcu.PayloadAttributes[0]
+		if err := attr.Validate(sf); err != nil {
+			writeProblem(w, http.StatusBadRequest, ErrInvalidAttributes, err.Error())
+			return
+		}
 		// If PayloadAttributes is present the URL fork MUST match the fork
 		// the new payload would belong to. Today only Amsterdam URL exists
 		// in this implementation so the timestamp check is implicit; we
 		// keep an explicit guard for future fork URLs.
-		if rt.backend.ForkFromTimestamp(ssz.Timestamp) != fork {
+		if rt.backend.ForkFromTimestamp(attr.Timestamp) != fork {
 			writeProblem(w, http.StatusBadRequest, ErrUnsupportedFork,
 				"payload_attributes timestamp does not match URL fork")
 			return
 		}
-		attrs = sszt.PayloadAttributesAmsterdamToEngine(ssz)
+		attrs = sszt.PayloadAttributesToEngine(attr)
 		// target_gas_limit and custody_columns are not yet plumbed into
 		// the JSON-RPC engine API. Custody is parsed-but-stubbed per
 		// agreed scope; target_gas_limit will be picked up when the
@@ -73,5 +79,5 @@ func (rt *Router) handleForkchoice(w http.ResponseWriter, r *http.Request, fork
 	if resp.PayloadID != nil {
 		out.PayloadID = [][8]byte{[8]byte(*resp.PayloadID)}
 	}
-	writeSSZResponse(w, out)
+	writeSSZResponse(w, out, sf)
 }

eth/engineapi/forkresolve.go

@@ -0,0 +1,41 @@
+// Copyright 2026 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package engineapi
+
+import (
+	"net/http"
+
+	sszt "github.com/ethereum/go-ethereum/beacon/engine/ssz"
+	"github.com/ethereum/go-ethereum/params/forks"
+	"github.com/karalabe/ssz"
+)
+
+// resolveFork maps the URL fork onto the ssz.Fork the codec multiplexes on,
+// enforcing that it is at least min. On failure it writes the appropriate
+// problem response and returns ok=false; the caller should return immediately.
+func resolveFork(w http.ResponseWriter, fork, min forks.Fork) (ssz.Fork, bool) {
+	if fork < min {
+		writeProblem(w, http.StatusBadRequest, ErrUnsupportedFork, "")
+		return ssz.ForkUnknown, false
+	}
+	sf, ok := sszt.ForkFor(fork)
+	if !ok {
+		writeProblem(w, http.StatusBadRequest, ErrUnsupportedFork, "")
+		return ssz.ForkUnknown, false
+	}
+	return sf, true
+}

eth/engineapi/get_payload.go

@@ -24,12 +24,13 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/params/forks"
 	"github.com/holiman/uint256"
+	"github.com/karalabe/ssz"
 )
 
 // handleGetPayload implements GET /engine/v2/{fork}/payloads/{payloadId}.
 func (rt *Router) handleGetPayload(w http.ResponseWriter, r *http.Request, fork forks.Fork, idHex string) {
-	if fork != forks.Amsterdam {
-		writeProblem(w, http.StatusBadRequest, ErrUnsupportedFork, "")
+	sf, ok := resolveFork(w, fork, forks.Amsterdam)
+	if !ok {
 		return
 	}
 	raw, err := hexutil.Decode(idHex)
@@ -46,17 +47,17 @@ func (rt *Router) handleGetPayload(w http.ResponseWriter, r *http.Request, fork
 		return
 	}
 
-	out := buildBuiltPayloadAmsterdam(env)
+	out := buildBuiltPayloadAmsterdam(env, sf)
 	w.Header().Set("Cache-Control", "no-store")
-	writeSSZResponse(w, out)
+	writeSSZResponse(w, out, sf)
 }
 
 // buildBuiltPayloadAmsterdam packages an engine.ExecutionPayloadEnvelope into
 // the SSZ BuiltPayload shape. BlockValue/BlobsBundle/Requests come straight
 // across; the inner payload goes through the SSZ converter.
-func buildBuiltPayloadAmsterdam(env *engine.ExecutionPayloadEnvelope) *sszt.BuiltPayloadAmsterdam {
+func buildBuiltPayloadAmsterdam(env *engine.ExecutionPayloadEnvelope, sf ssz.Fork) *sszt.BuiltPayloadAmsterdam {
 	out := &sszt.BuiltPayloadAmsterdam{
-		Payload:               sszt.ExecutionPayloadAmsterdamFromEngine(env.ExecutionPayload),
+		Payload:               sszt.ExecutionPayloadFromEngine(env.ExecutionPayload, sf),
 		BlockValue:            new(uint256.Int),
 		ExecutionRequests:     env.Requests,
 		ShouldOverrideBuilder: env.Override,

eth/engineapi/media.go

@@ -34,9 +34,10 @@ const (
 )
 
 // readSSZRequest enforces the SSZ content-type and Content-Length cap, then
-// decodes the request body into obj. Writes the appropriate problem response
-// on failure and returns false; the caller should return immediately.
-func readSSZRequest(w http.ResponseWriter, r *http.Request, obj ssz.Object, max int64) bool {
+// decodes the request body into obj for the given fork. Writes the appropriate
+// problem response on failure and returns false; the caller should return
+// immediately.
+func readSSZRequest(w http.ResponseWriter, r *http.Request, obj ssz.Object, fork ssz.Fork, max int64) bool {
 	if !strings.EqualFold(r.Header.Get("Content-Type"), sszContentType) {
 		writeProblem(w, http.StatusUnsupportedMediaType, ErrUnsupportedMedia, "expected "+sszContentType)
 		return false
@@ -54,18 +55,18 @@ func readSSZRequest(w http.ResponseWriter, r *http.Request, obj ssz.Object, max
 		writeProblem(w, http.StatusRequestEntityTooLarge, ErrRequestTooLarge, "")
 		return false
 	}
-	if err := ssz.DecodeFromBytes(body, obj); err != nil {
+	if err := ssz.DecodeFromBytesOnFork(body, obj, fork); err != nil {
 		writeProblem(w, http.StatusBadRequest, ErrSSZDecode, "")
 		return false
 	}
 	return true
 }
 
-// writeSSZResponse encodes obj into the response body. On encode failure it
-// writes an internal-error problem and returns false.
-func writeSSZResponse(w http.ResponseWriter, obj ssz.Object) bool {
-	buf := make([]byte, ssz.Size(obj))
-	if err := ssz.EncodeToBytes(buf, obj); err != nil {
+// writeSSZResponse encodes obj into the response body for the given fork. On
+// encode failure it writes an internal-error problem and returns false.
+func writeSSZResponse(w http.ResponseWriter, obj ssz.Object, fork ssz.Fork) bool {
+	buf := make([]byte, ssz.SizeOnFork(obj, fork))
+	if err := ssz.EncodeToBytesOnFork(buf, obj, fork); err != nil {
 		writeProblem(w, http.StatusInternalServerError, ErrInternal, err.Error())
 		return false
 	}

eth/engineapi/payloads.go

@@ -27,15 +27,21 @@ import (
 
 // handleNewPayload implements POST /engine/v2/{fork}/payloads.
 func (rt *Router) handleNewPayload(w http.ResponseWriter, r *http.Request, fork forks.Fork) {
-	if fork != forks.Amsterdam {
-		writeProblem(w, http.StatusBadRequest, ErrUnsupportedFork, "")
+	// The execution-apis spec currently only defines the payload envelope for
+	// Amsterdam; the inner payload shape is fork-driven by the codec.
+	sf, ok := resolveFork(w, fork, forks.Amsterdam)
+	if !ok {
 		return
 	}
 	env := new(sszt.ExecutionPayloadEnvelopeAmsterdam)
-	if !readSSZRequest(w, r, env, maxPayloadBytes) {
+	if !readSSZRequest(w, r, env, sf, maxPayloadBytes) {
 		return
 	}
-	data := sszt.ExecutionPayloadAmsterdamToEngine(env.Payload)
+	if err := env.Payload.Validate(sf); err != nil {
+		writeProblem(w, http.StatusUnprocessableEntity, ErrInvalidBody, err.Error())
+		return
+	}
+	data := sszt.ExecutionPayloadToEngine(env.Payload)
 
 	// The spec drops expectedBlobVersionedHashes; we recompute them from the
 	// payload's transactions before passing to the EL.
@@ -50,7 +56,7 @@ func (rt *Router) handleNewPayload(w http.ResponseWriter, r *http.Request, fork
 		mapBackendErr(w, err)
 		return
 	}
-	writeSSZResponse(w, sszt.PayloadStatusFromV1(&status))
+	writeSSZResponse(w, sszt.PayloadStatusFromV1(&status), sf)
 }
 
 // versionedHashesFromTxs extracts the blob versioned-hash list from the

eth/engineapi/router_test.go

@@ -103,10 +103,10 @@ func newTestServer(t *testing.T, b Backend) *httptest.Server {
 	return httptest.NewServer(http.StripPrefix(BasePath, NewRouter(b)))
 }
 
-func sszPost(t *testing.T, srv *httptest.Server, path string, body ssz.Object) *http.Response {
+func sszPost(t *testing.T, srv *httptest.Server, path string, body ssz.Object, fork ssz.Fork) *http.Response {
 	t.Helper()
-	buf := make([]byte, ssz.Size(body))
-	if err := ssz.EncodeToBytes(buf, body); err != nil {
+	buf := make([]byte, ssz.SizeOnFork(body, fork))
+	if err := ssz.EncodeToBytesOnFork(buf, body, fork); err != nil {
 		t.Fatalf("encode: %v", err)
 	}
 	req, _ := http.NewRequest(http.MethodPost, srv.URL+BasePath+path, bytes.NewReader(buf))
@@ -118,14 +118,14 @@ func sszPost(t *testing.T, srv *httptest.Server, path string, body ssz.Object) *
 	return resp
 }
 
-func decodeSSZ[T ssz.Object](t *testing.T, resp *http.Response, obj T) {
+func decodeSSZ[T ssz.Object](t *testing.T, resp *http.Response, obj T, fork ssz.Fork) {
 	t.Helper()
 	defer resp.Body.Close()
 	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		t.Fatalf("read body: %v", err)
 	}
-	if err := ssz.DecodeFromBytes(body, obj); err != nil {
+	if err := ssz.DecodeFromBytesOnFork(body, obj, fork); err != nil {
 		t.Fatalf("decode response: %v\nbody: %x", err, body)
 	}
 }
@@ -139,19 +139,24 @@ func TestRouterNewPayload(t *testing.T) {
 	srv := newTestServer(t, b)
 	defer srv.Close()
 
+	amsterdam, _ := sszt.ForkFor(forks.Amsterdam)
+	blob, excess, slot := uint64(0), uint64(0), uint64(0)
 	env := &sszt.ExecutionPayloadEnvelopeAmsterdam{
-		Payload: &sszt.ExecutionPayloadAmsterdam{
+		Payload: &sszt.ExecutionPayload{
 			BaseFeePerGas: uint256.NewInt(7e9),
 			LogsBloom:     [256]byte{},
+			BlobGasUsed:   &blob,
+			ExcessBlobGas: &excess,
+			SlotNumber:    &slot,
 		},
 		ParentBeaconBlockRoot: common.Hash{0x55},
 	}
-	resp := sszPost(t, srv, "/amsterdam/payloads", env)
+	resp := sszPost(t, srv, "/amsterdam/payloads", env, amsterdam)
 	if resp.StatusCode != 200 {
 		t.Fatalf("want 200, got %d", resp.StatusCode)
 	}
 	got := new(sszt.PayloadStatus)
-	decodeSSZ(t, resp, got)
+	decodeSSZ(t, resp, got, amsterdam)
 	if got.Status != sszt.StatusValid {
 		t.Errorf("status=%d want VALID(%d)", got.Status, sszt.StatusValid)
 	}
@@ -169,15 +174,16 @@ func TestRouterForkchoice(t *testing.T) {
 	srv := newTestServer(t, b)
 	defer srv.Close()
 
+	amsterdam, _ := sszt.ForkFor(forks.Amsterdam)
 	fcu := &sszt.ForkchoiceUpdateAmsterdam{
 		ForkchoiceState: &sszt.ForkchoiceState{HeadBlockHash: common.Hash{0xaa}},
 	}
-	resp := sszPost(t, srv, "/amsterdam/forkchoice", fcu)
+	resp := sszPost(t, srv, "/amsterdam/forkchoice", fcu, amsterdam)
 	if resp.StatusCode != 200 {
 		t.Fatalf("want 200, got %d", resp.StatusCode)
 	}
 	got := new(sszt.ForkchoiceUpdateResponseAmsterdam)
-	decodeSSZ(t, resp, got)
+	decodeSSZ(t, resp, got, amsterdam)
 	if got.PayloadStatus == nil || got.PayloadStatus.Status != sszt.StatusValid {
 		t.Errorf("status: %#v", got.PayloadStatus)
 	}
@@ -310,7 +316,7 @@ func TestRouterBlobsV2AllOrNothing(t *testing.T) {
 	srv := newTestServer(t, b)
 	defer srv.Close()
 	req := &sszt.BlobsVersionedHashesRequest{VersionedHashes: []common.Hash{{0x01}}}
-	resp := sszPost(t, srv, "/blobs/v2", req)
+	resp := sszPost(t, srv, "/blobs/v2", req, ssz.ForkUnknown)
 	defer resp.Body.Close()
 	if resp.StatusCode != 204 {
 		t.Fatalf("want 204, got %d", resp.StatusCode)
@@ -322,12 +328,12 @@ func TestRouterBlobsV3PartialOK(t *testing.T) {
 	srv := newTestServer(t, b)
 	defer srv.Close()
 	req := &sszt.BlobsVersionedHashesRequest{VersionedHashes: []common.Hash{{0x01}, {0x02}}}
-	resp := sszPost(t, srv, "/blobs/v3", req)
+	resp := sszPost(t, srv, "/blobs/v3", req, ssz.ForkUnknown)
 	if resp.StatusCode != 200 {
 		t.Fatalf("want 200, got %d", resp.StatusCode)
 	}
 	got := new(sszt.BlobsV2Response)
-	decodeSSZ(t, resp, got)
+	decodeSSZ(t, resp, got, ssz.ForkUnknown)
 	if len(got.Entries) != 2 {
 		t.Fatalf("entries=%d", len(got.Entries))
 	}