op-program: Add chain ID to hints when using interop (#13735)

* op-program: Add L2 chain ID to hints when using interop

* op-program: Add L2 chain ID to OutputRoot hints when using interop

* Fix label in error message.
Co-authored-by: Inphi <mlaw2501@gmail.com>

---------
Co-authored-by: Inphi <mlaw2501@gmail.com>

op-e2e/actions/interop/interop_test.go

@@ -319,7 +319,6 @@ func TestInteropFaultProofs(gt *testing.T) {
 			agreedClaim:    step1Expected,
 			disputedClaim:  step2Expected,
 			expectValid:    true,
-			skip:           true,
 		},
 		{
 			name:           "PaddingStep",

op-program/client/l2/cache.go

@@ -39,42 +39,42 @@ func NewCachingOracle(oracle Oracle) *CachingOracle {
 	}
 }
 
-func (o *CachingOracle) NodeByHash(nodeHash common.Hash) []byte {
+func (o *CachingOracle) NodeByHash(nodeHash common.Hash, chainID uint64) []byte {
 	node, ok := o.nodes.Get(nodeHash)
 	if ok {
 		return node
 	}
-	node = o.oracle.NodeByHash(nodeHash)
+	node = o.oracle.NodeByHash(nodeHash, chainID)
 	o.nodes.Add(nodeHash, node)
 	return node
 }
 
-func (o *CachingOracle) CodeByHash(codeHash common.Hash) []byte {
+func (o *CachingOracle) CodeByHash(codeHash common.Hash, chainID uint64) []byte {
 	code, ok := o.codes.Get(codeHash)
 	if ok {
 		return code
 	}
-	code = o.oracle.CodeByHash(codeHash)
+	code = o.oracle.CodeByHash(codeHash, chainID)
 	o.codes.Add(codeHash, code)
 	return code
 }
 
-func (o *CachingOracle) BlockByHash(blockHash common.Hash) *types.Block {
+func (o *CachingOracle) BlockByHash(blockHash common.Hash, chainID uint64) *types.Block {
 	block, ok := o.blocks.Get(blockHash)
 	if ok {
 		return block
 	}
-	block = o.oracle.BlockByHash(blockHash)
+	block = o.oracle.BlockByHash(blockHash, chainID)
 	o.blocks.Add(blockHash, block)
 	return block
 }
 
-func (o *CachingOracle) OutputByRoot(root common.Hash) eth.Output {
+func (o *CachingOracle) OutputByRoot(root common.Hash, chainID uint64) eth.Output {
 	output, ok := o.outputs.Get(root)
 	if ok {
 		return output
 	}
-	output = o.oracle.OutputByRoot(root)
+	output = o.oracle.OutputByRoot(root, chainID)
 	o.outputs.Add(root, output)
 	return output
 }

op-program/client/l2/cache_test.go

@@ -15,6 +15,7 @@ import (
 var _ Oracle = (*CachingOracle)(nil)
 
 func TestBlockByHash(t *testing.T) {
+	chainID := uint64(48294)
 	stub, _ := test.NewStubOracle(t)
 	oracle := NewCachingOracle(stub)
 
@@ -23,12 +24,12 @@ func TestBlockByHash(t *testing.T) {
 
 	// Initial call retrieves from the stub
 	stub.Blocks[block.Hash()] = block
-	actual := oracle.BlockByHash(block.Hash())
+	actual := oracle.BlockByHash(block.Hash(), chainID)
 	require.Equal(t, block, actual)
 
-	// Later calls should retrieve from cache
+	// Later calls should retrieve from cache (even if chain ID is different)
 	delete(stub.Blocks, block.Hash())
-	actual = oracle.BlockByHash(block.Hash())
+	actual = oracle.BlockByHash(block.Hash(), 9982)
 	require.Equal(t, block, actual)
 }
 
@@ -41,12 +42,12 @@ func TestNodeByHash(t *testing.T) {
 
 	// Initial call retrieves from the stub
 	stateStub.Data[hash] = node
-	actual := oracle.NodeByHash(hash)
+	actual := oracle.NodeByHash(hash, 1234)
 	require.Equal(t, node, actual)
 
-	// Later calls should retrieve from cache
+	// Later calls should retrieve from cache (even if chain ID is different)
 	delete(stateStub.Data, hash)
-	actual = oracle.NodeByHash(hash)
+	actual = oracle.NodeByHash(hash, 997845)
 	require.Equal(t, node, actual)
 }
 
@@ -59,12 +60,12 @@ func TestCodeByHash(t *testing.T) {
 
 	// Initial call retrieves from the stub
 	stateStub.Code[hash] = node
-	actual := oracle.CodeByHash(hash)
+	actual := oracle.CodeByHash(hash, 342)
 	require.Equal(t, node, actual)
 
-	// Later calls should retrieve from cache
+	// Later calls should retrieve from cache (even if the chain ID is different)
 	delete(stateStub.Code, hash)
-	actual = oracle.CodeByHash(hash)
+	actual = oracle.CodeByHash(hash, 986776)
 	require.Equal(t, node, actual)
 }
 
@@ -78,11 +79,11 @@ func TestOutputByRoot(t *testing.T) {
 	// Initial call retrieves from the stub
 	root := common.Hash(eth.OutputRoot(output))
 	stub.Outputs[root] = output
-	actual := oracle.OutputByRoot(root)
+	actual := oracle.OutputByRoot(root, 59284)
 	require.Equal(t, output, actual)
 
-	// Later calls should retrieve from cache
+	// Later calls should retrieve from cache (even if the chain ID is different)
 	delete(stub.Outputs, root)
-	actual = oracle.OutputByRoot(root)
+	actual = oracle.OutputByRoot(root, 9193)
 	require.Equal(t, output, actual)
 }

op-program/client/l2/db.go

@@ -18,12 +18,14 @@ var ErrInvalidKeyLength = errors.New("pre-images must be identified by 32-byte h
 type OracleKeyValueStore struct {
 	db      ethdb.KeyValueStore
 	oracle  StateOracle
+	chainID uint64
 }
 
-func NewOracleBackedDB(oracle StateOracle) *OracleKeyValueStore {
+func NewOracleBackedDB(oracle StateOracle, chainID uint64) *OracleKeyValueStore {
 	return &OracleKeyValueStore{
 		db:      memorydb.New(),
 		oracle:  oracle,
+		chainID: chainID,
 	}
 }
 
@@ -38,12 +40,12 @@ func (o *OracleKeyValueStore) Get(key []byte) ([]byte, error) {
 
 	if len(key) == codePrefixedKeyLength && bytes.HasPrefix(key, rawdb.CodePrefix) {
 		key = key[len(rawdb.CodePrefix):]
-		return o.oracle.CodeByHash(*(*[common.HashLength]byte)(key)), nil
+		return o.oracle.CodeByHash(*(*[common.HashLength]byte)(key), o.chainID), nil
 	}
 	if len(key) != common.HashLength {
 		return nil, ErrInvalidKeyLength
 	}
-	return o.oracle.NodeByHash(*(*[common.HashLength]byte)(key)), nil
+	return o.oracle.NodeByHash(*(*[common.HashLength]byte)(key), o.chainID), nil
 }
 
 func (o *OracleKeyValueStore) NewBatch() ethdb.Batch {

op-program/client/l2/db_test.go

@@ -34,7 +34,7 @@ var _ ethdb.KeyValueStore = (*OracleKeyValueStore)(nil)
 func TestGet(t *testing.T) {
 	t.Run("IncorrectLengthKey", func(t *testing.T) {
 		oracle := test.NewStubStateOracle(t)
-		db := NewOracleBackedDB(oracle)
+		db := NewOracleBackedDB(oracle, 1234)
 		val, err := db.Get([]byte{1, 2, 3})
 		require.ErrorIs(t, err, ErrInvalidKeyLength)
 		require.Nil(t, val)
@@ -42,7 +42,7 @@ func TestGet(t *testing.T) {
 
 	t.Run("KeyWithCodePrefix", func(t *testing.T) {
 		oracle := test.NewStubStateOracle(t)
-		db := NewOracleBackedDB(oracle)
+		db := NewOracleBackedDB(oracle, 1234)
 		key := common.HexToHash("0x12345678")
 		prefixedKey := append(rawdb.CodePrefix, key.Bytes()...)
 
@@ -56,7 +56,7 @@ func TestGet(t *testing.T) {
 
 	t.Run("NormalKeyThatHappensToStartWithCodePrefix", func(t *testing.T) {
 		oracle := test.NewStubStateOracle(t)
-		db := NewOracleBackedDB(oracle)
+		db := NewOracleBackedDB(oracle, 1234)
 		key := make([]byte, common.HashLength)
 		copy(rawdb.CodePrefix, key)
 		fmt.Println(key[0])
@@ -73,7 +73,7 @@ func TestGet(t *testing.T) {
 		expected := []byte{2, 6, 3, 8}
 		oracle := test.NewStubStateOracle(t)
 		oracle.Data[key] = expected
-		db := NewOracleBackedDB(oracle)
+		db := NewOracleBackedDB(oracle, 1234)
 		val, err := db.Get(key.Bytes())
 		require.NoError(t, err)
 		require.Equal(t, expected, val)
@@ -83,7 +83,7 @@ func TestGet(t *testing.T) {
 func TestPut(t *testing.T) {
 	t.Run("NewKey", func(t *testing.T) {
 		oracle := test.NewStubStateOracle(t)
-		db := NewOracleBackedDB(oracle)
+		db := NewOracleBackedDB(oracle, 1234)
 		key := common.HexToHash("0xAA4488")
 		value := []byte{2, 6, 3, 8}
 		err := db.Put(key.Bytes(), value)
@@ -95,7 +95,7 @@ func TestPut(t *testing.T) {
 	})
 	t.Run("ReplaceKey", func(t *testing.T) {
 		oracle := test.NewStubStateOracle(t)
-		db := NewOracleBackedDB(oracle)
+		db := NewOracleBackedDB(oracle, 1234)
 		key := common.HexToHash("0xAA4488")
 		value1 := []byte{2, 6, 3, 8}
 		value2 := []byte{1, 2, 3}
@@ -117,13 +117,13 @@ func TestSupportsStateDBOperations(t *testing.T) {
 	genesisBlock := l2Genesis.MustCommit(realDb, trieDB)
 
 	loader := test.NewKvStateOracle(t, realDb)
-	assertStateDataAvailable(t, NewOracleBackedDB(loader), l2Genesis, genesisBlock)
+	assertStateDataAvailable(t, NewOracleBackedDB(loader, 1234), l2Genesis, genesisBlock)
 }
 
 func TestUpdateState(t *testing.T) {
 	l2Genesis := createGenesis()
 	oracle := test.NewStubStateOracle(t)
-	db := rawdb.NewDatabase(NewOracleBackedDB(oracle))
+	db := rawdb.NewDatabase(NewOracleBackedDB(oracle, 1234))
 
 	trieDB := triedb.NewDatabase(db, &triedb.Config{HashDB: hashdb.Defaults})
 	genesisBlock := l2Genesis.MustCommit(db, trieDB)

op-program/client/l2/engine_backend.go

@@ -45,12 +45,13 @@ type OracleBackedL2Chain struct {
 var _ engineapi.CachingEngineBackend = (*OracleBackedL2Chain)(nil)
 
 func NewOracleBackedL2Chain(logger log.Logger, oracle Oracle, precompileOracle engineapi.PrecompileOracle, chainCfg *params.ChainConfig, l2OutputRoot common.Hash) (*OracleBackedL2Chain, error) {
-	output := oracle.OutputByRoot(l2OutputRoot)
+	chainID := chainCfg.ChainID.Uint64()
+	output := oracle.OutputByRoot(l2OutputRoot, chainID)
 	outputV0, ok := output.(*eth.OutputV0)
 	if !ok {
 		return nil, fmt.Errorf("unsupported L2 output version: %d", output.Version())
 	}
-	head := oracle.BlockByHash(outputV0.BlockHash)
+	head := oracle.BlockByHash(outputV0.BlockHash, chainID)
 	logger.Info("Loaded L2 head", "hash", head.Hash(), "number", head.Number())
 	return &OracleBackedL2Chain{
 		log:      logger,
@@ -69,7 +70,7 @@ func NewOracleBackedL2Chain(logger log.Logger, oracle Oracle, precompileOracle e
 		finalized:  head.Header(),
 		oracleHead: head.Header(),
 		blocks:     make(map[common.Hash]*types.Block),
-		db:         NewOracleBackedDB(oracle),
+		db:         NewOracleBackedDB(oracle, chainID),
 		vmCfg: vm.Config{
 			PrecompileOverrides: engineapi.CreatePrecompileOverrides(precompileOracle),
 		},
@@ -122,7 +123,7 @@ func (o *OracleBackedL2Chain) GetBlockByHash(hash common.Hash) *types.Block {
 		return block
 	}
 	// Retrieve from the oracle
-	return o.oracle.BlockByHash(hash)
+	return o.oracle.BlockByHash(hash, o.chainCfg.ChainID.Uint64())
 }
 
 func (o *OracleBackedL2Chain) GetBlock(hash common.Hash, number uint64) *types.Block {

op-program/client/l2/engine_backend_test.go

@@ -378,7 +378,7 @@ func createBlock(t *testing.T, chain *OracleBackedL2Chain, opts ...blockCreateOp
 	require.NoError(t, err)
 	nonce := parentDB.GetNonce(fundedAddress)
 	config := chain.Config()
-	db := rawdb.NewDatabase(NewOracleBackedDB(chain.oracle))
+	db := rawdb.NewDatabase(NewOracleBackedDB(chain.oracle, config.ChainID.Uint64()))
 	blocks, _ := core.GenerateChain(config, parent, chain.Engine(), db, 1, func(i int, gen *core.BlockGen) {
 		rawTx := &types.DynamicFeeTx{
 			ChainID:   config.ChainID,

op-program/client/l2/hints.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
 
 	preimage "github.com/ethereum-optimism/optimism/op-preimage"
 )
@@ -19,43 +20,95 @@ const (
 	HintAgreedPrestate = "agreed-pre-state"
 )
 
-type BlockHeaderHint common.Hash
+type LegacyBlockHeaderHint common.Hash
+
+var _ preimage.Hint = LegacyBlockHeaderHint{}
+
+func (l LegacyBlockHeaderHint) Hint() string {
+	return HintL2BlockHeader + " " + (common.Hash)(l).String()
+}
+
+type HashAndChainID struct {
+	Hash    common.Hash
+	ChainID uint64
+}
+
+func (h HashAndChainID) Marshal() []byte {
+	d := make([]byte, 32+8)
+	copy(d[:32], h.Hash[:])
+	binary.BigEndian.PutUint64(d[32:], h.ChainID)
+	return d
+}
+
+type BlockHeaderHint HashAndChainID
 
 var _ preimage.Hint = BlockHeaderHint{}
 
 func (l BlockHeaderHint) Hint() string {
-	return HintL2BlockHeader + " " + (common.Hash)(l).String()
+	return HintL2BlockHeader + " " + hexutil.Encode(HashAndChainID(l).Marshal())
 }
 
-type TransactionsHint common.Hash
+type LegacyTransactionsHint common.Hash
+
+var _ preimage.Hint = LegacyTransactionsHint{}
+
+func (l LegacyTransactionsHint) Hint() string {
+	return HintL2Transactions + " " + (common.Hash)(l).String()
+}
+
+type TransactionsHint HashAndChainID
 
 var _ preimage.Hint = TransactionsHint{}
 
 func (l TransactionsHint) Hint() string {
-	return HintL2Transactions + " " + (common.Hash)(l).String()
+	return HintL2Transactions + " " + hexutil.Encode(HashAndChainID(l).Marshal())
 }
 
-type CodeHint common.Hash
+type CodeHint HashAndChainID
 
 var _ preimage.Hint = CodeHint{}
 
 func (l CodeHint) Hint() string {
+	return HintL2Code + " " + hexutil.Encode(HashAndChainID(l).Marshal())
+}
+
+type LegacyCodeHint common.Hash
+
+var _ preimage.Hint = LegacyCodeHint{}
+
+func (l LegacyCodeHint) Hint() string {
 	return HintL2Code + " " + (common.Hash)(l).String()
 }
 
-type StateNodeHint common.Hash
+type StateNodeHint HashAndChainID
 
 var _ preimage.Hint = StateNodeHint{}
 
 func (l StateNodeHint) Hint() string {
+	return HintL2StateNode + " " + hexutil.Encode(HashAndChainID(l).Marshal())
+}
+
+type LegacyStateNodeHint common.Hash
+
+var _ preimage.Hint = LegacyStateNodeHint{}
+
+func (l LegacyStateNodeHint) Hint() string {
 	return HintL2StateNode + " " + (common.Hash)(l).String()
 }
 
-type L2OutputHint common.Hash
+type L2OutputHint HashAndChainID
 
 var _ preimage.Hint = L2OutputHint{}
 
 func (l L2OutputHint) Hint() string {
+	return HintL2Output + " " + hexutil.Encode(HashAndChainID(l).Marshal())
+}
+
+type LegacyL2OutputHint common.Hash
+
+var _ preimage.Hint = LegacyL2OutputHint{}
+
+func (l LegacyL2OutputHint) Hint() string {
 	return HintL2Output + " " + (common.Hash)(l).String()
 }
 

op-program/client/l2/oracle.go

@@ -19,11 +19,11 @@ type StateOracle interface {
 	// NodeByHash retrieves the merkle-patricia trie node pre-image for a given hash.
 	// Trie nodes may be from the world state trie or any account storage trie.
 	// Contract code is not stored as part of the trie and must be retrieved via CodeByHash
-	NodeByHash(nodeHash common.Hash) []byte
+	NodeByHash(nodeHash common.Hash, chainID uint64) []byte
 
 	// CodeByHash retrieves the contract code pre-image for a given hash.
 	// codeHash should be retrieved from the world state account for a contract.
-	CodeByHash(codeHash common.Hash) []byte
+	CodeByHash(codeHash common.Hash, chainID uint64) []byte
 }
 
 // Oracle defines the high-level API used to retrieve L2 data.
@@ -32,9 +32,9 @@ type Oracle interface {
 	StateOracle
 
 	// BlockByHash retrieves the block with the given hash.
-	BlockByHash(blockHash common.Hash) *types.Block
+	BlockByHash(blockHash common.Hash, chainID uint64) *types.Block
 
-	OutputByRoot(root common.Hash) eth.Output
+	OutputByRoot(root common.Hash, chainID uint64) eth.Output
 
 	// BlockDataByHash retrieves the block, including all data used to construct it.
 	BlockDataByHash(agreedBlockHash, blockHash common.Hash, chainID uint64) *types.Block
@@ -47,19 +47,25 @@ type Oracle interface {
 type PreimageOracle struct {
 	oracle         preimage.Oracle
 	hint           preimage.Hinter
+	hintL2ChainIDs bool
 }
 
 var _ Oracle = (*PreimageOracle)(nil)
 
-func NewPreimageOracle(raw preimage.Oracle, hint preimage.Hinter) *PreimageOracle {
+func NewPreimageOracle(raw preimage.Oracle, hint preimage.Hinter, hintL2ChainIDs bool) *PreimageOracle {
 	return &PreimageOracle{
 		oracle:         raw,
 		hint:           hint,
+		hintL2ChainIDs: hintL2ChainIDs,
 	}
 }
 
-func (p *PreimageOracle) headerByBlockHash(blockHash common.Hash) *types.Header {
-	p.hint.Hint(BlockHeaderHint(blockHash))
+func (p *PreimageOracle) headerByBlockHash(blockHash common.Hash, chainID uint64) *types.Header {
+	if p.hintL2ChainIDs {
+		p.hint.Hint(BlockHeaderHint{Hash: blockHash, ChainID: chainID})
+	} else {
+		p.hint.Hint(LegacyBlockHeaderHint(blockHash))
+	}
 	headerRlp := p.oracle.Get(preimage.Keccak256Key(blockHash))
 	var header types.Header
 	if err := rlp.DecodeBytes(headerRlp, &header); err != nil {
@@ -68,15 +74,19 @@ func (p *PreimageOracle) headerByBlockHash(blockHash common.Hash) *types.Header
 	return &header
 }
 
-func (p *PreimageOracle) BlockByHash(blockHash common.Hash) *types.Block {
-	header := p.headerByBlockHash(blockHash)
-	txs := p.LoadTransactions(blockHash, header.TxHash)
+func (p *PreimageOracle) BlockByHash(blockHash common.Hash, chainID uint64) *types.Block {
+	header := p.headerByBlockHash(blockHash, chainID)
+	txs := p.LoadTransactions(blockHash, header.TxHash, chainID)
 
 	return types.NewBlockWithHeader(header).WithBody(types.Body{Transactions: txs})
 }
 
-func (p *PreimageOracle) LoadTransactions(blockHash common.Hash, txHash common.Hash) []*types.Transaction {
-	p.hint.Hint(TransactionsHint(blockHash))
+func (p *PreimageOracle) LoadTransactions(blockHash common.Hash, txHash common.Hash, chainID uint64) []*types.Transaction {
+	if p.hintL2ChainIDs {
+		p.hint.Hint(TransactionsHint{Hash: blockHash, ChainID: chainID})
+	} else {
+		p.hint.Hint(LegacyTransactionsHint(blockHash))
+	}
 
 	opaqueTxs := mpt.ReadTrie(txHash, func(key common.Hash) []byte {
 		return p.oracle.Get(preimage.Keccak256Key(key))
@@ -89,18 +99,30 @@ func (p *PreimageOracle) LoadTransactions(blockHash common.Hash, txHash common.H
 	return txs
 }
 
-func (p *PreimageOracle) NodeByHash(nodeHash common.Hash) []byte {
-	p.hint.Hint(StateNodeHint(nodeHash))
+func (p *PreimageOracle) NodeByHash(nodeHash common.Hash, chainID uint64) []byte {
+	if p.hintL2ChainIDs {
+		p.hint.Hint(StateNodeHint{Hash: nodeHash, ChainID: chainID})
+	} else {
+		p.hint.Hint(LegacyStateNodeHint(nodeHash))
+	}
 	return p.oracle.Get(preimage.Keccak256Key(nodeHash))
 }
 
-func (p *PreimageOracle) CodeByHash(codeHash common.Hash) []byte {
-	p.hint.Hint(CodeHint(codeHash))
+func (p *PreimageOracle) CodeByHash(codeHash common.Hash, chainID uint64) []byte {
+	if p.hintL2ChainIDs {
+		p.hint.Hint(CodeHint{Hash: codeHash, ChainID: chainID})
+	} else {
+		p.hint.Hint(LegacyCodeHint(codeHash))
+	}
 	return p.oracle.Get(preimage.Keccak256Key(codeHash))
 }
 
-func (p *PreimageOracle) OutputByRoot(l2OutputRoot common.Hash) eth.Output {
-	p.hint.Hint(L2OutputHint(l2OutputRoot))
+func (p *PreimageOracle) OutputByRoot(l2OutputRoot common.Hash, chainID uint64) eth.Output {
+	if p.hintL2ChainIDs {
+		p.hint.Hint(L2OutputHint{Hash: l2OutputRoot, ChainID: chainID})
+	} else {
+		p.hint.Hint(LegacyL2OutputHint(l2OutputRoot))
+	}
 	data := p.oracle.Get(preimage.Keccak256Key(l2OutputRoot))
 	output, err := eth.UnmarshalOutput(data)
 	if err != nil {
@@ -116,8 +138,8 @@ func (p *PreimageOracle) BlockDataByHash(agreedBlockHash, blockHash common.Hash,
 		ChainID:         chainID,
 	}
 	p.hint.Hint(hint)
-	header := p.headerByBlockHash(blockHash)
-	txs := p.LoadTransactions(blockHash, header.TxHash)
+	header := p.headerByBlockHash(blockHash, chainID)
+	txs := p.LoadTransactions(blockHash, header.TxHash, chainID)
 	return types.NewBlockWithHeader(header).WithBody(types.Body{Transactions: txs})
 }
 

op-program/client/l2/oracle_test.go

@@ -19,29 +19,27 @@ import (
 	"github.com/ethereum-optimism/optimism/op-service/testutils"
 )
 
-func mockPreimageOracle(t *testing.T) (po *PreimageOracle, hintsMock *mock.Mock, preimages map[common.Hash][]byte) {
+func mockPreimageOracle(t *testing.T, hintL2ChainIDs bool) (po *PreimageOracle, hintsMock *mock.Mock, preimages map[common.Hash][]byte) {
 	// Prepare the pre-images
 	preimages = make(map[common.Hash][]byte)
 
 	hintsMock = new(mock.Mock)
 
-	po = &PreimageOracle{
-		oracle: preimage.OracleFn(func(key preimage.Key) []byte {
+	rawOracle := preimage.OracleFn(func(key preimage.Key) []byte {
 		v, ok := preimages[key.PreimageKey()]
 		require.True(t, ok, "preimage must exist")
 		return v
-		}),
-		hint: preimage.HinterFn(func(v preimage.Hint) {
+	})
+	hinter := preimage.HinterFn(func(v preimage.Hint) {
 		hintsMock.MethodCalled("hint", v.Hint())
-		}),
-	}
-
-	return po, hintsMock, preimages
+	})
+	po = NewPreimageOracle(rawOracle, hinter, hintL2ChainIDs)
+	return
 }
 
 // testBlock tests that the given block can be passed through the preimage oracle.
-func testBlock(t *testing.T, block *types.Block) {
-	po, hints, preimages := mockPreimageOracle(t)
+func testBlock(t *testing.T, block *types.Block, hintL2ChainIDs bool) {
+	po, hints, preimages := mockPreimageOracle(t, hintL2ChainIDs)
 
 	hdrBytes, err := rlp.EncodeToBytes(block.Header())
 	require.NoError(t, err)
@@ -54,12 +52,19 @@ func testBlock(t *testing.T, block *types.Block) {
 		preimages[preimage.Keccak256Key(crypto.Keccak256Hash(p)).PreimageKey()] = p
 	}
 
+	chainID := uint64(4924)
+
 	// Prepare a raw mock pre-image oracle that will serve the pre-image data and handle hints
 
 	// Check if blocks with txs work
-	hints.On("hint", BlockHeaderHint(block.Hash()).Hint()).Once().Return()
-	hints.On("hint", TransactionsHint(block.Hash()).Hint()).Once().Return()
-	gotBlock := po.BlockByHash(block.Hash())
+	if hintL2ChainIDs {
+		hints.On("hint", BlockHeaderHint{Hash: block.Hash(), ChainID: chainID}.Hint()).Once().Return()
+		hints.On("hint", TransactionsHint{Hash: block.Hash(), ChainID: chainID}.Hint()).Once().Return()
+	} else {
+		hints.On("hint", LegacyBlockHeaderHint(block.Hash()).Hint()).Once().Return()
+		hints.On("hint", LegacyTransactionsHint(block.Hash()).Hint()).Once().Return()
+	}
+	gotBlock := po.BlockByHash(block.Hash(), chainID)
 	hints.AssertExpectations(t)
 
 	require.Equal(t, gotBlock.Hash(), block.Hash())
@@ -75,8 +80,12 @@ func TestPreimageOracleBlockByHash(t *testing.T) {
 
 	for i := 0; i < 10; i++ {
 		block, _ := testutils.RandomBlock(rng, 10)
+		t.Run(fmt.Sprintf("legacy_block_%d", i), func(t *testing.T) {
+			testBlock(t, block, false)
+		})
+
 		t.Run(fmt.Sprintf("block_%d", i), func(t *testing.T) {
-			testBlock(t, block)
+			testBlock(t, block, true)
 		})
 	}
 }
@@ -85,8 +94,24 @@ func TestPreimageOracleNodeByHash(t *testing.T) {
 	rng := rand.New(rand.NewSource(123))
 
 	for i := 0; i < 10; i++ {
+		chainID := rng.Uint64()
+		t.Run(fmt.Sprintf("legacy_node_%d", i), func(t *testing.T) {
+			po, hints, preimages := mockPreimageOracle(t, false)
+
+			node := make([]byte, 123)
+			rng.Read(node)
+
+			h := crypto.Keccak256Hash(node)
+			preimages[preimage.Keccak256Key(h).PreimageKey()] = node
+
+			hints.On("hint", LegacyStateNodeHint(h).Hint()).Once().Return()
+			gotNode := po.NodeByHash(h, chainID)
+			hints.AssertExpectations(t)
+			require.Equal(t, hexutil.Bytes(node), hexutil.Bytes(gotNode), "node matches")
+		})
+
 		t.Run(fmt.Sprintf("node_%d", i), func(t *testing.T) {
-			po, hints, preimages := mockPreimageOracle(t)
+			po, hints, preimages := mockPreimageOracle(t, true)
 
 			node := make([]byte, 123)
 			rng.Read(node)
@@ -94,8 +119,8 @@ func TestPreimageOracleNodeByHash(t *testing.T) {
 			h := crypto.Keccak256Hash(node)
 			preimages[preimage.Keccak256Key(h).PreimageKey()] = node
 
-			hints.On("hint", StateNodeHint(h).Hint()).Once().Return()
-			gotNode := po.NodeByHash(h)
+			hints.On("hint", StateNodeHint{Hash: h, ChainID: chainID}.Hint()).Once().Return()
+			gotNode := po.NodeByHash(h, chainID)
 			hints.AssertExpectations(t)
 			require.Equal(t, hexutil.Bytes(node), hexutil.Bytes(gotNode), "node matches")
 		})
@@ -106,8 +131,24 @@ func TestPreimageOracleCodeByHash(t *testing.T) {
 	rng := rand.New(rand.NewSource(123))
 
 	for i := 0; i < 10; i++ {
+		chainID := rng.Uint64()
+		t.Run(fmt.Sprintf("legacy_code_%d", i), func(t *testing.T) {
+			po, hints, preimages := mockPreimageOracle(t, false)
+
+			node := make([]byte, 123)
+			rng.Read(node)
+
+			h := crypto.Keccak256Hash(node)
+			preimages[preimage.Keccak256Key(h).PreimageKey()] = node
+
+			hints.On("hint", LegacyCodeHint(h).Hint()).Once().Return()
+			gotNode := po.CodeByHash(h, chainID)
+			hints.AssertExpectations(t)
+			require.Equal(t, hexutil.Bytes(node), hexutil.Bytes(gotNode), "code matches")
+		})
+
 		t.Run(fmt.Sprintf("code_%d", i), func(t *testing.T) {
-			po, hints, preimages := mockPreimageOracle(t)
+			po, hints, preimages := mockPreimageOracle(t, true)
 
 			node := make([]byte, 123)
 			rng.Read(node)
@@ -115,8 +156,8 @@ func TestPreimageOracleCodeByHash(t *testing.T) {
 			h := crypto.Keccak256Hash(node)
 			preimages[preimage.Keccak256Key(h).PreimageKey()] = node
 
-			hints.On("hint", CodeHint(h).Hint()).Once().Return()
-			gotNode := po.CodeByHash(h)
+			hints.On("hint", CodeHint{Hash: h, ChainID: chainID}.Hint()).Once().Return()
+			gotNode := po.CodeByHash(h, chainID)
 			hints.AssertExpectations(t)
 			require.Equal(t, hexutil.Bytes(node), hexutil.Bytes(gotNode), "code matches")
 		})
@@ -127,14 +168,26 @@ func TestPreimageOracleOutputByRoot(t *testing.T) {
 	rng := rand.New(rand.NewSource(123))
 
 	for i := 0; i < 10; i++ {
+		chainID := rng.Uint64()
+		t.Run(fmt.Sprintf("legacy_output_%d", i), func(t *testing.T) {
+			po, hints, preimages := mockPreimageOracle(t, false)
+			output := testutils.RandomOutputV0(rng)
+
+			h := common.Hash(eth.OutputRoot(output))
+			preimages[preimage.Keccak256Key(h).PreimageKey()] = output.Marshal()
+			hints.On("hint", LegacyL2OutputHint(h).Hint()).Once().Return()
+			gotOutput := po.OutputByRoot(h, chainID)
+			hints.AssertExpectations(t)
+			require.Equal(t, hexutil.Bytes(output.Marshal()), hexutil.Bytes(gotOutput.Marshal()), "output matches")
+		})
 		t.Run(fmt.Sprintf("output_%d", i), func(t *testing.T) {
-			po, hints, preimages := mockPreimageOracle(t)
+			po, hints, preimages := mockPreimageOracle(t, true)
 			output := testutils.RandomOutputV0(rng)
 
 			h := common.Hash(eth.OutputRoot(output))
 			preimages[preimage.Keccak256Key(h).PreimageKey()] = output.Marshal()
-			hints.On("hint", L2OutputHint(h).Hint()).Once().Return()
-			gotOutput := po.OutputByRoot(h)
+			hints.On("hint", L2OutputHint{Hash: h, ChainID: chainID}.Hint()).Once().Return()
+			gotOutput := po.OutputByRoot(h, chainID)
 			hints.AssertExpectations(t)
 			require.Equal(t, hexutil.Bytes(output.Marshal()), hexutil.Bytes(gotOutput.Marshal()), "output matches")
 		})

op-program/client/l2/test/stub_oracle.go

@@ -15,8 +15,8 @@ import (
 
 // Same as l2.StateOracle but need to use our own copy to avoid dependency loops
 type stateOracle interface {
-	NodeByHash(nodeHash common.Hash) []byte
-	CodeByHash(codeHash common.Hash) []byte
+	NodeByHash(nodeHash common.Hash, chainID uint64) []byte
+	CodeByHash(codeHash common.Hash, chainID uint64) []byte
 }
 
 type StubBlockOracle struct {
@@ -56,7 +56,7 @@ func NewStubOracleWithBlocks(t *testing.T, chain []*gethTypes.Block, outputs []e
 	}
 }
 
-func (o StubBlockOracle) BlockByHash(blockHash common.Hash) *gethTypes.Block {
+func (o StubBlockOracle) BlockByHash(blockHash common.Hash, chainID uint64) *gethTypes.Block {
 	block, ok := o.Blocks[blockHash]
 	if !ok {
 		o.t.Fatalf("requested unknown block %s", blockHash)
@@ -64,7 +64,7 @@ func (o StubBlockOracle) BlockByHash(blockHash common.Hash) *gethTypes.Block {
 	return block
 }
 
-func (o StubBlockOracle) OutputByRoot(root common.Hash) eth.Output {
+func (o StubBlockOracle) OutputByRoot(root common.Hash, chainID uint64) eth.Output {
 	output, ok := o.Outputs[root]
 	if !ok {
 		o.t.Fatalf("requested unknown output root %s", root)
@@ -100,7 +100,7 @@ func NewKvStateOracle(t *testing.T, db ethdb.KeyValueStore) *KvStateOracle {
 	}
 }
 
-func (o *KvStateOracle) NodeByHash(nodeHash common.Hash) []byte {
+func (o *KvStateOracle) NodeByHash(nodeHash common.Hash, chainID uint64) []byte {
 	val, err := o.Source.Get(nodeHash.Bytes())
 	if err != nil {
 		o.t.Fatalf("error retrieving node %v: %v", nodeHash, err)
@@ -108,7 +108,7 @@ func (o *KvStateOracle) NodeByHash(nodeHash common.Hash) []byte {
 	return val
 }
 
-func (o *KvStateOracle) CodeByHash(hash common.Hash) []byte {
+func (o *KvStateOracle) CodeByHash(hash common.Hash, chainID uint64) []byte {
 	return rawdb.ReadCode(o.Source, hash)
 }
 
@@ -127,7 +127,7 @@ type StubStateOracle struct {
 	Code map[common.Hash][]byte
 }
 
-func (o *StubStateOracle) NodeByHash(nodeHash common.Hash) []byte {
+func (o *StubStateOracle) NodeByHash(nodeHash common.Hash, chainID uint64) []byte {
 	data, ok := o.Data[nodeHash]
 	if !ok {
 		o.t.Fatalf("no value for node %v", nodeHash)
@@ -135,7 +135,7 @@ func (o *StubStateOracle) NodeByHash(nodeHash common.Hash) []byte {
 	return data
 }
 
-func (o *StubStateOracle) CodeByHash(hash common.Hash) []byte {
+func (o *StubStateOracle) CodeByHash(hash common.Hash, chainID uint64) []byte {
 	data, ok := o.Code[hash]
 	if !ok {
 		o.t.Fatalf("no value for code %v", hash)

op-program/client/program.go

@@ -45,7 +45,7 @@ func RunProgram(logger log.Logger, preimageOracle io.ReadWriter, preimageHinter
 	pClient := preimage.NewOracleClient(preimageOracle)
 	hClient := preimage.NewHintWriter(preimageHinter)
 	l1PreimageOracle := l1.NewCachingOracle(l1.NewPreimageOracle(pClient, hClient))
-	l2PreimageOracle := l2.NewCachingOracle(l2.NewPreimageOracle(pClient, hClient))
+	l2PreimageOracle := l2.NewCachingOracle(l2.NewPreimageOracle(pClient, hClient, cfg.InteropEnabled))
 
 	if cfg.InteropEnabled {
 		bootInfo := boot.BootstrapInterop(pClient)

op-program/host/common/l2_client.go

@@ -32,3 +32,7 @@ func NewL2Client(client client.RPC, log log.Logger, metrics caching.Metrics, con
 func (s *L2Client) OutputByRoot(ctx context.Context, blockRoot common.Hash) (eth.Output, error) {
 	return s.OutputV0AtBlock(ctx, blockRoot)
 }
+
+func (s *L2Client) OutputByNumber(ctx context.Context, blockNum uint64) (eth.Output, error) {
+	return s.OutputV0AtBlockNumber(ctx, blockNum)
+}

op-program/host/common/l2_source.go

@@ -117,6 +117,14 @@ func (l *L2Source) OutputByRoot(ctx context.Context, blockRoot common.Hash) (eth
 	return l.canonicalEthClient.OutputByRoot(ctx, blockRoot)
 }
 
+// OutputByBlockNumber implements prefetcher.L2Source.
+func (l *L2Source) OutputByNumber(ctx context.Context, blockNum uint64) (eth.Output, error) {
+	if l.ExperimentalEnabled() {
+		return l.experimentalClient.OutputByNumber(ctx, blockNum)
+	}
+	return l.canonicalEthClient.OutputByNumber(ctx, blockNum)
+}
+
 // ExecutionWitness implements prefetcher.L2Source.
 func (l *L2Source) ExecutionWitness(ctx context.Context, blockNum uint64) (*eth.ExecutionWitness, error) {
 	if !l.ExperimentalEnabled() {

op-program/host/prefetcher/prefetcher.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	preimage "github.com/ethereum-optimism/optimism/op-preimage"
+	clientTypes "github.com/ethereum-optimism/optimism/op-program/client/interop/types"
 	"github.com/ethereum-optimism/optimism/op-program/client/l1"
 	"github.com/ethereum-optimism/optimism/op-program/client/l2"
 	"github.com/ethereum-optimism/optimism/op-program/client/mpt"
@@ -258,11 +259,11 @@ func (p *Prefetcher) prefetch(ctx context.Context, hint string) error {
 		}
 		return p.kvStore.Put(preimage.PrecompileKey(inputHash).PreimageKey(), result)
 	case l2.HintL2BlockHeader, l2.HintL2Transactions:
-		if len(hintBytes) != 32 {
-			return fmt.Errorf("invalid L2 header/tx hint: %x", hint)
+		hash, chainID, err := p.parseHashAndChainID("L2 header/tx", hintBytes)
+		if err != nil {
+			return err
 		}
-		hash := common.Hash(hintBytes)
-		source, err := p.l2Sources.ForChainID(p.defaultChainID)
+		source, err := p.l2Sources.ForChainID(chainID)
 		if err != nil {
 			return err
 		}
@@ -280,11 +281,11 @@ func (p *Prefetcher) prefetch(ctx context.Context, hint string) error {
 		}
 		return p.storeTransactions(txs)
 	case l2.HintL2StateNode:
-		if len(hintBytes) != 32 {
-			return fmt.Errorf("invalid L2 state node hint: %x", hint)
+		hash, chainID, err := p.parseHashAndChainID("L2 state node", hintBytes)
+		if err != nil {
+			return err
 		}
-		hash := common.Hash(hintBytes)
-		source, err := p.l2Sources.ForChainID(p.defaultChainID)
+		source, err := p.l2Sources.ForChainID(chainID)
 		if err != nil {
 			return err
 		}
@@ -294,11 +295,11 @@ func (p *Prefetcher) prefetch(ctx context.Context, hint string) error {
 		}
 		return p.kvStore.Put(preimage.Keccak256Key(hash).PreimageKey(), node)
 	case l2.HintL2Code:
-		if len(hintBytes) != 32 {
-			return fmt.Errorf("invalid L2 code hint: %x", hint)
+		hash, chainID, err := p.parseHashAndChainID("L2 code", hintBytes)
+		if err != nil {
+			return err
 		}
-		hash := common.Hash(hintBytes)
-		source, err := p.l2Sources.ForChainID(p.defaultChainID)
+		source, err := p.l2Sources.ForChainID(chainID)
 		if err != nil {
 			return err
 		}
@@ -308,14 +309,15 @@ func (p *Prefetcher) prefetch(ctx context.Context, hint string) error {
 		}
 		return p.kvStore.Put(preimage.Keccak256Key(hash).PreimageKey(), code)
 	case l2.HintL2Output:
-		if len(hintBytes) != 32 {
-			return fmt.Errorf("invalid L2 output hint: %x", hint)
+		requestedHash, chainID, err := p.parseHashAndChainID("L2 output", hintBytes)
+		if err != nil {
+			return err
 		}
-		requestedHash := common.Hash(hintBytes)
-		source, err := p.l2Sources.ForChainID(p.defaultChainID)
+		source, err := p.l2Sources.ForChainID(chainID)
 		if err != nil {
 			return err
 		}
+		if len(p.agreedPrestate) == 0 {
 			output, err := source.OutputByRoot(ctx, p.l2Head)
 			if err != nil {
 				return fmt.Errorf("failed to fetch L2 output root for block %s: %w", p.l2Head, err)
@@ -325,6 +327,29 @@ func (p *Prefetcher) prefetch(ctx context.Context, hint string) error {
 				return fmt.Errorf("output root %v from block %v does not match requested root: %v", hash, p.l2Head, requestedHash)
 			}
 			return p.kvStore.Put(preimage.Keccak256Key(hash).PreimageKey(), output.Marshal())
+		} else {
+			prestate, err := clientTypes.UnmarshalTransitionState(p.agreedPrestate)
+			if err != nil {
+				return fmt.Errorf("cannot fetch output root, invalid agreed prestate: %w", err)
+			}
+			superRoot, err := eth.UnmarshalSuperRoot(prestate.SuperRoot)
+			if err != nil {
+				return fmt.Errorf("cannot fetch output root, invalid super root in prestate: %w", err)
+			}
+			superV1, ok := superRoot.(*eth.SuperV1)
+			if !ok {
+				return fmt.Errorf("cannot fetch output root, unsupported super root version in prestate: %v", superRoot.Version())
+			}
+			blockNum, err := source.RollupConfig().TargetBlockNumber(superV1.Timestamp)
+			if err != nil {
+				return fmt.Errorf("cannot fetch output root, failed to calculate block number at timestamp %v: %w", superV1.Timestamp, err)
+			}
+			output, err := source.OutputByNumber(ctx, blockNum)
+			if err != nil {
+				return fmt.Errorf("failed to fetch L2 output root for block %v: %w", blockNum, err)
+			}
+			return p.kvStore.Put(preimage.Keccak256Key(eth.OutputRoot(output)).PreimageKey(), output.Marshal())
+		}
 	case l2.HintL2BlockData:
 		if p.executor == nil {
 			return fmt.Errorf("this prefetcher does not support native block execution")
@@ -353,6 +378,17 @@ func (p *Prefetcher) prefetch(ctx context.Context, hint string) error {
 	return fmt.Errorf("unknown hint type: %v", hintType)
 }
 
+func (p *Prefetcher) parseHashAndChainID(hintType string, hintBytes []byte) (common.Hash, uint64, error) {
+	switch len(hintBytes) {
+	case 32:
+		return common.Hash(hintBytes), p.defaultChainID, nil
+	case 40:
+		return common.Hash(hintBytes[0:32]), binary.BigEndian.Uint64(hintBytes[32:]), nil
+	default:
+		return common.Hash{}, 0, fmt.Errorf("invalid %s hint: %x", hintType, hintBytes)
+	}
+}
+
 type BlockDataKey [32]byte
 
 func (p BlockDataKey) Key() [32]byte {

op-program/host/prefetcher/retry.go

@@ -152,6 +152,17 @@ func (s *RetryingL2Source) OutputByRoot(ctx context.Context, blockRoot common.Ha
 	})
 }
 
+func (s *RetryingL2Source) OutputByNumber(ctx context.Context, blockNum uint64) (eth.Output, error) {
+	return retry.Do(ctx, maxAttempts, s.strategy, func() (eth.Output, error) {
+		o, err := s.source.OutputByNumber(ctx, blockNum)
+		if err != nil {
+			s.logger.Warn("Failed to fetch l2 output", "block", blockNum, "err", err)
+			return o, err
+		}
+		return o, nil
+	})
+}
+
 func NewRetryingL2Source(logger log.Logger, source hosttypes.L2Source) *RetryingL2Source {
 	return &RetryingL2Source{
 		logger:   logger,

op-program/host/prefetcher/retry_test.go

@@ -226,7 +226,8 @@ func createL1BlobSource(t *testing.T) (*RetryingL1BlobSource, *testutils.MockBlo
 func TestRetryingL2Source(t *testing.T) {
 	ctx := context.Background()
 	hash := common.Hash{0xab}
-	info := &testutils.MockBlockInfo{InfoHash: hash}
+	blockNum := uint64(14982)
+	info := &testutils.MockBlockInfo{InfoHash: hash, InfoNum: blockNum}
 	// The mock really doesn't like returning nil for a eth.BlockInfo so return a value we expect to be ignored instead
 	wrongInfo := &testutils.MockBlockInfo{InfoHash: common.Hash{0x99}}
 	txs := types.Transactions{
@@ -325,6 +326,28 @@ func TestRetryingL2Source(t *testing.T) {
 		require.NoError(t, err)
 		require.Equal(t, output, actualOutput)
 	})
+
+	t.Run("OutputByNumber Success", func(t *testing.T) {
+		source, mock := createL2Source(t)
+		defer mock.AssertExpectations(t)
+		mock.ExpectOutputByNumber(blockNum, output, nil)
+
+		actualOutput, err := source.OutputByNumber(ctx, blockNum)
+		require.NoError(t, err)
+		require.Equal(t, output, actualOutput)
+	})
+
+	t.Run("OutputByNumber Error", func(t *testing.T) {
+		source, mock := createL2Source(t)
+		defer mock.AssertExpectations(t)
+		expectedErr := errors.New("boom")
+		mock.ExpectOutputByNumber(blockNum, wrongOutput, expectedErr)
+		mock.ExpectOutputByNumber(blockNum, output, nil)
+
+		actualOutput, err := source.OutputByNumber(ctx, blockNum)
+		require.NoError(t, err)
+		require.Equal(t, output, actualOutput)
+	})
 }
 
 func createL2Source(t *testing.T) (*RetryingL2Source, *MockL2Source) {
@@ -370,6 +393,11 @@ func (m *MockL2Source) OutputByRoot(ctx context.Context, blockRoot common.Hash)
 	return out[0].(eth.Output), *out[1].(*error)
 }
 
+func (m *MockL2Source) OutputByNumber(ctx context.Context, blockNum uint64) (eth.Output, error) {
+	out := m.Mock.MethodCalled("OutputByNumber", blockNum)
+	return out[0].(eth.Output), *out[1].(*error)
+}
+
 func (m *MockL2Source) ExpectInfoAndTxsByHash(blockHash common.Hash, info eth.BlockInfo, txs types.Transactions, err error) {
 	m.Mock.On("InfoAndTxsByHash", blockHash).Once().Return(info, txs, &err)
 }
@@ -386,4 +414,8 @@ func (m *MockL2Source) ExpectOutputByRoot(blockHash common.Hash, output eth.Outp
 	m.Mock.On("OutputByRoot", blockHash).Once().Return(output, &err)
 }
 
+func (m *MockL2Source) ExpectOutputByNumber(blockNum uint64, output eth.Output, err error) {
+	m.Mock.On("OutputByNumber", blockNum).Once().Return(output, &err)
+}
+
 var _ hosttypes.L2Source = (*MockL2Source)(nil)

op-program/host/types/types.go

@@ -24,6 +24,7 @@ type L2Source interface {
 	NodeByHash(ctx context.Context, hash common.Hash) ([]byte, error)
 	CodeByHash(ctx context.Context, hash common.Hash) ([]byte, error)
 	OutputByRoot(ctx context.Context, blockRoot common.Hash) (eth.Output, error)
+	OutputByNumber(ctx context.Context, blockNumber uint64) (eth.Output, error)
 	RollupConfig() *rollup.Config
 	ExperimentalEnabled() bool
 }

op-service/sources/l2_client.go

@@ -172,15 +172,26 @@ func (s *L2Client) SystemConfigByL2Hash(ctx context.Context, hash common.Hash) (
 	return cfg, nil
 }
 
+func (s *L2Client) OutputV0AtBlockNumber(ctx context.Context, blockNum uint64) (*eth.OutputV0, error) {
+	head, err := s.InfoByNumber(ctx, blockNum)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get L2 block by hash: %w", err)
+	}
+	return s.outputV0(ctx, head)
+}
 func (s *L2Client) OutputV0AtBlock(ctx context.Context, blockHash common.Hash) (*eth.OutputV0, error) {
 	head, err := s.InfoByHash(ctx, blockHash)
 	if err != nil {
 		return nil, fmt.Errorf("failed to get L2 block by hash: %w", err)
 	}
-	if head == nil {
+	return s.outputV0(ctx, head)
+}
+
+func (s *L2Client) outputV0(ctx context.Context, block eth.BlockInfo) (*eth.OutputV0, error) {
+	if block == nil {
 		return nil, ethereum.NotFound
 	}
-
+	blockHash := block.Hash()
 	proof, err := s.GetProof(ctx, predeploys.L2ToL1MessagePasserAddr, []common.Hash{}, blockHash.String())
 	if err != nil {
 		return nil, fmt.Errorf("failed to get contract proof at block %s: %w", blockHash, err)
@@ -189,10 +200,10 @@ func (s *L2Client) OutputV0AtBlock(ctx context.Context, blockHash common.Hash) (
 		return nil, fmt.Errorf("proof %w", ethereum.NotFound)
 	}
 	// make sure that the proof (including storage hash) that we retrieved is correct by verifying it against the state-root
-	if err := proof.Verify(head.Root()); err != nil {
-		return nil, fmt.Errorf("invalid withdrawal root hash, state root was %s: %w", head.Root(), err)
+	if err := proof.Verify(block.Root()); err != nil {
+		return nil, fmt.Errorf("invalid withdrawal root hash, state root was %s: %w", block.Root(), err)
 	}
-	stateRoot := head.Root()
+	stateRoot := block.Root()
 	return &eth.OutputV0{
 		StateRoot:                eth.Bytes32(stateRoot),
 		MessagePasserStorageRoot: eth.Bytes32(proof.StorageHash),