beacon/engin: add unmarshalJSON for epe and bapl structs

beacon/engine/codec_bapl.go

@@ -16,6 +16,8 @@
 
 package engine
 
+import "encoding/json"
+
 // estimateBlobAndProofV1Size returns a rough estimate of the JSON size for a BlobAndProofV1.
 func estimateBlobAndProofV1Size(item *BlobAndProofV1) int {
 	if item == nil {
@@ -87,6 +89,39 @@ func (list BlobAndProofListV1) MarshalJSON() ([]byte, error) {
 	return buf, nil
 }
 
+// UnmarshalJSON implements json.Unmarshaler.
+func (list *BlobAndProofListV1) UnmarshalJSON(input []byte) error {
+	if isJSONNull(input) {
+		*list = nil
+		return nil
+	}
+	items := make(BlobAndProofListV1, 0)
+	if err := decodeJSONArray(input, func(value json.RawMessage) error {
+		if isJSONNull(value) {
+			items = append(items, nil)
+			return nil
+		}
+		item := new(BlobAndProofV1)
+		if err := decodeJSONObject(value, func(key string, value json.RawMessage) error {
+			switch key {
+			case "blob":
+				return item.Blob.UnmarshalJSON(value)
+			case "proof":
+				return item.Proof.UnmarshalJSON(value)
+			}
+			return nil
+		}); err != nil {
+			return err
+		}
+		items = append(items, item)
+		return nil
+	}); err != nil {
+		return err
+	}
+	*list = items
+	return nil
+}
+
 // MarshalJSON implements json.Marshaler.
 func (list BlobAndProofListV2) MarshalJSON() ([]byte, error) {
 	// Estimate buffer size.
@@ -107,3 +142,40 @@ func (list BlobAndProofListV2) MarshalJSON() ([]byte, error) {
 	buf = append(buf, ']')
 	return buf, nil
 }
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (list *BlobAndProofListV2) UnmarshalJSON(input []byte) error {
+	if isJSONNull(input) {
+		*list = nil
+		return nil
+	}
+	items := make(BlobAndProofListV2, 0)
+	if err := decodeJSONArray(input, func(value json.RawMessage) error {
+		if isJSONNull(value) {
+			items = append(items, nil)
+			return nil
+		}
+		item := new(BlobAndProofV2)
+		if err := decodeJSONObject(value, func(key string, value json.RawMessage) error {
+			switch key {
+			case "blob":
+				return item.Blob.UnmarshalJSON(value)
+			case "proofs":
+				proofs, err := unmarshalHexBytesArray(value)
+				if err != nil {
+					return err
+				}
+				item.CellProofs = proofs
+			}
+			return nil
+		}); err != nil {
+			return err
+		}
+		items = append(items, item)
+		return nil
+	}); err != nil {
+		return err
+	}
+	*list = items
+	return nil
+}

beacon/engine/codec_bapl_test.go

@@ -122,6 +122,57 @@ func TestBlobAndProofListV1MarshalJSON(t *testing.T) {
 	}
 }
 
+func TestBlobAndProofListV1UnmarshalJSON(t *testing.T) {
+	tests := []struct {
+		name string
+		json string
+		want BlobAndProofListV1
+	}{
+		{
+			name: "multiple items",
+			json: `[{"blob":"0x0102","proof":"0x0304"},{"blob":"0x","proof":"0x05"}]`,
+			want: BlobAndProofListV1{
+				{
+					Blob:  hexutil.Bytes{0x01, 0x02},
+					Proof: hexutil.Bytes{0x03, 0x04},
+				},
+				{
+					Blob:  hexutil.Bytes{},
+					Proof: hexutil.Bytes{0x05},
+				},
+			},
+		},
+		{
+			name: "nil item",
+			json: `[null,{"blob":"0xaa","proof":"0xbb"}]`,
+			want: BlobAndProofListV1{
+				nil,
+				{
+					Blob:  hexutil.Bytes{0xaa},
+					Proof: hexutil.Bytes{0xbb},
+				},
+			},
+		},
+		{
+			name: "null list",
+			json: `null`,
+			want: nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var got BlobAndProofListV1
+			if err := got.UnmarshalJSON([]byte(tt.json)); err != nil {
+				t.Fatalf("UnmarshalJSON error: %v", err)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Fatalf("decoded mismatch\ngot:  %#v\nwant: %#v", got, tt.want)
+			}
+		})
+	}
+}
+
 func TestBlobAndProofListV2MarshalJSON(t *testing.T) {
 	tests := []struct {
 		name string
@@ -186,6 +237,57 @@ func TestBlobAndProofListV2MarshalJSON(t *testing.T) {
 	}
 }
 
+func TestBlobAndProofListV2UnmarshalJSON(t *testing.T) {
+	tests := []struct {
+		name string
+		json string
+		want BlobAndProofListV2
+	}{
+		{
+			name: "multiple items",
+			json: `[{"blob":"0x0102","proofs":["0x0304","0x05"]},{"blob":"0x","proofs":[]}]`,
+			want: BlobAndProofListV2{
+				{
+					Blob:       hexutil.Bytes{0x01, 0x02},
+					CellProofs: []hexutil.Bytes{{0x03, 0x04}, {0x05}},
+				},
+				{
+					Blob:       hexutil.Bytes{},
+					CellProofs: []hexutil.Bytes{},
+				},
+			},
+		},
+		{
+			name: "nil item and nil proofs",
+			json: `[null,{"blob":"0xcc","proofs":null}]`,
+			want: BlobAndProofListV2{
+				nil,
+				{
+					Blob:       hexutil.Bytes{0xcc},
+					CellProofs: nil,
+				},
+			},
+		},
+		{
+			name: "null list",
+			json: `null`,
+			want: nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var got BlobAndProofListV2
+			if err := got.UnmarshalJSON([]byte(tt.json)); err != nil {
+				t.Fatalf("UnmarshalJSON error: %v", err)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Fatalf("decoded mismatch\ngot:  %#v\nwant: %#v", got, tt.want)
+			}
+		})
+	}
+}
+
 func TestBlobAndProofFieldCoverage(t *testing.T) {
 	tests := []struct {
 		name     string

beacon/engine/codec_epe.go

@@ -17,10 +17,9 @@
 package engine
 
 import (
-	"encoding/hex"
 	"encoding/json"
 	"errors"
-	"slices"
+	"math/big"
 
 	"github.com/ethereum/go-ethereum/common/hexutil"
 )
@@ -55,32 +54,26 @@ func marshalBlobsBundle(buf []byte, b *BlobsBundle) []byte {
 	return buf
 }
 
-// marshalHexBytesArray writes an array of hex-encoded byte slices to buf.
-// A nil slice is written as "null" to match encoding/json semantics.
-func marshalHexBytesArray(buf []byte, items []hexutil.Bytes) []byte {
-	if items == nil {
-		return append(buf, "null"...)
+func unmarshalBlobsBundle(input []byte) (*BlobsBundle, error) {
+	if isJSONNull(input) {
+		return nil, nil
 	}
-	buf = append(buf, '[')
-	for i, item := range items {
-		if i > 0 {
-			buf = append(buf, ',')
+	var bundle BlobsBundle
+	if err := decodeJSONObject(input, func(key string, value json.RawMessage) error {
+		var err error
+		switch key {
+		case "commitments":
+			bundle.Commitments, err = unmarshalHexBytesArray(value)
+		case "proofs":
+			bundle.Proofs, err = unmarshalHexBytesArray(value)
+		case "blobs":
+			bundle.Blobs, err = unmarshalHexBytesArray(value)
 		}
-		buf = writeHexBytes(buf, item)
+		return err
+	}); err != nil {
+		return nil, err
 	}
-	buf = append(buf, ']')
-	return buf
-}
-
-// writeHexBytes writes a hex-encoded byte slice as a JSON string ("0x...") to buf.
-func writeHexBytes(buf []byte, data []byte) []byte {
-	buf = append(buf, '"', '0', 'x')
-	buf = slices.Grow(buf, len(data)*2+1)
-	cur := len(buf)
-	buf = buf[:cur+len(data)*2]
-	hex.Encode(buf[cur:], data)
-	buf = append(buf, '"')
-	return buf
+	return &bundle, nil
 }
 
 // MarshalJSON implements json.Marshaler.
@@ -175,3 +168,85 @@ func (e ExecutionPayloadEnvelope) MarshalJSON() ([]byte, error) {
 	buf = append(buf, '}')
 	return buf, nil
 }
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (e *ExecutionPayloadEnvelope) UnmarshalJSON(input []byte) error {
+	var (
+		payloadSeen    bool
+		blockValueSeen bool
+	)
+	*e = ExecutionPayloadEnvelope{}
+	if err := decodeJSONObject(input, func(key string, value json.RawMessage) error {
+		switch key {
+		case "executionPayload":
+			payloadSeen = true
+			if isJSONNull(value) {
+				e.ExecutionPayload = nil
+				return nil
+			}
+			var payload ExecutableData
+			if err := payload.UnmarshalJSON(value); err != nil {
+				return err
+			}
+			e.ExecutionPayload = &payload
+		case "blockValue":
+			blockValueSeen = true
+			if isJSONNull(value) {
+				e.BlockValue = nil
+				return nil
+			}
+			var blockValue hexutil.Big
+			if err := blockValue.UnmarshalJSON(value); err != nil {
+				return err
+			}
+			e.BlockValue = (*big.Int)(&blockValue)
+		case "blobsBundle":
+			bundle, err := unmarshalBlobsBundle(value)
+			if err != nil {
+				return err
+			}
+			e.BlobsBundle = bundle
+		case "executionRequests":
+			requests, err := unmarshalHexBytesArray(value)
+			if err != nil {
+				return err
+			}
+			if requests == nil {
+				e.Requests = nil
+				return nil
+			}
+			e.Requests = make([][]byte, len(requests))
+			for i, req := range requests {
+				e.Requests[i] = req
+			}
+		case "shouldOverrideBuilder":
+			if isJSONNull(value) {
+				e.Override = false
+				return nil
+			}
+			if err := json.Unmarshal(value, &e.Override); err != nil {
+				return err
+			}
+		case "witness":
+			if isJSONNull(value) {
+				e.Witness = nil
+				return nil
+			}
+			var witness hexutil.Bytes
+			if err := witness.UnmarshalJSON(value); err != nil {
+				return err
+			}
+			e.Witness = &witness
+		}
+		return nil
+	}); err != nil {
+		return err
+	}
+	if !payloadSeen || e.ExecutionPayload == nil {
+		return errors.New("missing required field 'executionPayload' for ExecutionPayloadEnvelope")
+	}
+	if !blockValueSeen || e.BlockValue == nil {
+		return errors.New("missing required field 'blockValue' for ExecutionPayloadEnvelope")
+	}
+	return nil
+}

beacon/engine/codec_epe_test.go

@@ -214,6 +214,100 @@ func TestMarshalJSONRoundtrip(t *testing.T) {
 	}
 }
 
+func TestUnmarshalJSON(t *testing.T) {
+	witness := hexutil.Bytes{0xde, 0xad}
+	tests := []struct {
+		name string
+		env  ExecutionPayloadEnvelope
+	}{
+		{
+			name: "full envelope with blobs",
+			env: ExecutionPayloadEnvelope{
+				ExecutionPayload: makeTestPayload(),
+				BlockValue:       big.NewInt(12345),
+				BlobsBundle: &BlobsBundle{
+					Commitments: []hexutil.Bytes{{0x01, 0x02}},
+					Proofs:      []hexutil.Bytes{{0x03, 0x04}},
+					Blobs:       []hexutil.Bytes{{0x05, 0x06}},
+				},
+				Requests: [][]byte{{0xaa}, {0xbb, 0xcc}},
+				Override: true,
+				Witness:  &witness,
+			},
+		},
+		{
+			name: "null optional fields",
+			env: ExecutionPayloadEnvelope{
+				ExecutionPayload: makeTestPayload(),
+				BlockValue:       big.NewInt(1),
+				BlobsBundle:      nil,
+				Requests:         nil,
+				Override:         false,
+				Witness:          nil,
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			input, err := json.Marshal(toCanonical(&tt.env))
+			if err != nil {
+				t.Fatalf("canonical marshal error: %v", err)
+			}
+
+			var got ExecutionPayloadEnvelope
+			if err := got.UnmarshalJSON(input); err != nil {
+				t.Fatalf("UnmarshalJSON error: %v", err)
+			}
+
+			gotJSON, err := json.Marshal(toCanonical(&got))
+			if err != nil {
+				t.Fatalf("canonical marshal after unmarshal error: %v", err)
+			}
+			if !bytes.Equal(compactJSON(gotJSON), compactJSON(input)) {
+				t.Errorf("JSON mismatch after unmarshal\ngot:  %s\nwant: %s", gotJSON, input)
+			}
+		})
+	}
+}
+
+func TestUnmarshalJSONMissingRequiredFields(t *testing.T) {
+	tests := []struct {
+		name string
+		json func(t *testing.T) []byte
+	}{
+		{
+			name: "missing executionPayload",
+			json: func(t *testing.T) []byte {
+				return []byte(`{"blockValue":"0x1"}`)
+			},
+		},
+		{
+			name: "missing blockValue",
+			json: func(t *testing.T) []byte {
+				input, err := json.Marshal(struct {
+					ExecutionPayload *ExecutableData `json:"executionPayload"`
+				}{
+					ExecutionPayload: makeTestPayload(),
+				})
+				if err != nil {
+					t.Fatalf("marshal input: %v", err)
+				}
+				return input
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var env ExecutionPayloadEnvelope
+			if err := env.UnmarshalJSON(tt.json(t)); err == nil {
+				t.Fatal("expected error")
+			}
+		})
+	}
+}
+
 func TestMarshalJSONNilPayload(t *testing.T) {
 	env := ExecutionPayloadEnvelope{
 		ExecutionPayload: nil,

beacon/engine/codec_helper.go

@@ -0,0 +1,158 @@
+// 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 engine
+
+import (
+	"bytes"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"slices"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+)
+
+// marshalHexBytesArray writes an array of hex-encoded byte slices to buf.
+// A nil slice is written as "null" to match encoding/json semantics.
+func marshalHexBytesArray(buf []byte, items []hexutil.Bytes) []byte {
+	if items == nil {
+		return append(buf, "null"...)
+	}
+	buf = append(buf, '[')
+	for i, item := range items {
+		if i > 0 {
+			buf = append(buf, ',')
+		}
+		buf = writeHexBytes(buf, item)
+	}
+	buf = append(buf, ']')
+	return buf
+}
+
+// writeHexBytes writes a hex-encoded byte slice as a JSON string ("0x...") to buf.
+func writeHexBytes(buf []byte, data []byte) []byte {
+	buf = append(buf, '"', '0', 'x')
+	buf = slices.Grow(buf, len(data)*2+1)
+	cur := len(buf)
+	buf = buf[:cur+len(data)*2]
+	hex.Encode(buf[cur:], data)
+	buf = append(buf, '"')
+	return buf
+}
+
+func decodeJSONObject(input []byte, fn func(key string, value json.RawMessage) error) error {
+	dec := json.NewDecoder(bytes.NewReader(input))
+	tok, err := dec.Token()
+	if err != nil {
+		return err
+	}
+	delim, ok := tok.(json.Delim)
+	if !ok || delim != '{' {
+		return fmt.Errorf("expected JSON object")
+	}
+	for dec.More() {
+		tok, err := dec.Token()
+		if err != nil {
+			return err
+		}
+		key, ok := tok.(string)
+		if !ok {
+			return fmt.Errorf("expected JSON object key")
+		}
+		var value json.RawMessage
+		if err := dec.Decode(&value); err != nil {
+			return err
+		}
+		if err := fn(key, value); err != nil {
+			return err
+		}
+	}
+	tok, err = dec.Token()
+	if err != nil {
+		return err
+	}
+	delim, ok = tok.(json.Delim)
+	if !ok || delim != '}' {
+		return fmt.Errorf("expected end of JSON object")
+	}
+	if _, err := dec.Token(); err != io.EOF {
+		if err == nil {
+			return fmt.Errorf("unexpected trailing data")
+		}
+		return err
+	}
+	return nil
+}
+
+func decodeJSONArray(input []byte, fn func(value json.RawMessage) error) error {
+	dec := json.NewDecoder(bytes.NewReader(input))
+	tok, err := dec.Token()
+	if err != nil {
+		return err
+	}
+	delim, ok := tok.(json.Delim)
+	if !ok || delim != '[' {
+		return fmt.Errorf("expected JSON array")
+	}
+	for dec.More() {
+		var value json.RawMessage
+		if err := dec.Decode(&value); err != nil {
+			return err
+		}
+		if err := fn(value); err != nil {
+			return err
+		}
+	}
+	tok, err = dec.Token()
+	if err != nil {
+		return err
+	}
+	delim, ok = tok.(json.Delim)
+	if !ok || delim != ']' {
+		return fmt.Errorf("expected end of JSON array")
+	}
+	if _, err := dec.Token(); err != io.EOF {
+		if err == nil {
+			return fmt.Errorf("unexpected trailing data")
+		}
+		return err
+	}
+	return nil
+}
+
+func isJSONNull(input []byte) bool {
+	return bytes.Equal(bytes.TrimSpace(input), []byte("null"))
+}
+
+func unmarshalHexBytesArray(input []byte) ([]hexutil.Bytes, error) {
+	if isJSONNull(input) {
+		return nil, nil
+	}
+	items := make([]hexutil.Bytes, 0)
+	if err := decodeJSONArray(input, func(value json.RawMessage) error {
+		var item hexutil.Bytes
+		if err := item.UnmarshalJSON(value); err != nil {
+			return err
+		}
+		items = append(items, item)
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+	return items, nil
+}

beacon/engine/gen_epe.go

@@ -1,53 +0,0 @@
-// Code generated by github.com/fjl/gencodec. DO NOT EDIT.
-
-package engine
-
-import (
-	"encoding/json"
-	"errors"
-	"math/big"
-
-	"github.com/ethereum/go-ethereum/common/hexutil"
-)
-
-var _ = (*executionPayloadEnvelopeMarshaling)(nil)
-
-// UnmarshalJSON unmarshals from JSON.
-func (e *ExecutionPayloadEnvelope) UnmarshalJSON(input []byte) error {
-	type ExecutionPayloadEnvelope struct {
-		ExecutionPayload *ExecutableData `json:"executionPayload"  gencodec:"required"`
-		BlockValue       *hexutil.Big    `json:"blockValue"  gencodec:"required"`
-		BlobsBundle      *BlobsBundle    `json:"blobsBundle"`
-		Requests         []hexutil.Bytes `json:"executionRequests"`
-		Override         *bool           `json:"shouldOverrideBuilder"`
-		Witness          *hexutil.Bytes  `json:"witness,omitempty"`
-	}
-	var dec ExecutionPayloadEnvelope
-	if err := json.Unmarshal(input, &dec); err != nil {
-		return err
-	}
-	if dec.ExecutionPayload == nil {
-		return errors.New("missing required field 'executionPayload' for ExecutionPayloadEnvelope")
-	}
-	e.ExecutionPayload = dec.ExecutionPayload
-	if dec.BlockValue == nil {
-		return errors.New("missing required field 'blockValue' for ExecutionPayloadEnvelope")
-	}
-	e.BlockValue = (*big.Int)(dec.BlockValue)
-	if dec.BlobsBundle != nil {
-		e.BlobsBundle = dec.BlobsBundle
-	}
-	if dec.Requests != nil {
-		e.Requests = make([][]byte, len(dec.Requests))
-		for k, v := range dec.Requests {
-			e.Requests[k] = v
-		}
-	}
-	if dec.Override != nil {
-		e.Override = *dec.Override
-	}
-	if dec.Witness != nil {
-		e.Witness = dec.Witness
-	}
-	return nil
-}

beacon/engine/types.go

@@ -165,12 +165,6 @@ type BlobAndProofV2 struct {
 // that avoids the overhead of encoding/json for large blob payloads.
 type BlobAndProofListV2 []*BlobAndProofV2
 
-// JSON type overrides for ExecutionPayloadEnvelope.
-type executionPayloadEnvelopeMarshaling struct {
-	BlockValue *hexutil.Big
-	Requests   []hexutil.Bytes
-}
-
 type PayloadStatusV1 struct {
 	Status          string         `json:"status"`
 	Witness         *hexutil.Bytes `json:"witness,omitempty"`