Merge branch 'develop' into fault-proof-specs

.circleci/config.yml

@@ -61,7 +61,7 @@ jobs:
   yarn-monorepo:
     docker:
       - image: ethereumoptimism/ci-builder:latest
-    resource_class: xlarge
+    resource_class: large
     steps:
       - checkout
       - check-changed:
@@ -142,7 +142,7 @@ jobs:
         default: "oplabs-tools-artifacts/images"
     machine:
       image: ubuntu-2204:2022.07.1
-      resource_class: xlarge
+      resource_class: medium
     steps:
       - checkout
       - run:
@@ -207,7 +207,7 @@ jobs:
         default: "linux/amd64"
     machine:
       image: ubuntu-2204:2022.07.1
-      resource_class: xlarge
+      resource_class: medium
     steps:
       - gcp-oidc-authenticate
       # Below is CircleCI recommended way of specifying nameservers on an Ubuntu box:
@@ -261,7 +261,7 @@ jobs:
         default: "linux/amd64"
     machine:
       image: ubuntu-2204:2022.07.1
-      resource_class: xlarge
+      resource_class: medium
     steps:
       - gcp-cli/install
       - gcp-oidc-authenticate
@@ -379,7 +379,7 @@ jobs:
   contracts-bedrock-slither:
     docker:
       - image: ethereumoptimism/ci-builder:latest
-    resource_class: xlarge
+    resource_class: large
     steps:
       - checkout
       - attach_workspace: { at: "." }
@@ -600,7 +600,7 @@ jobs:
       - run:
           name: run lint
           command: |
-            golangci-lint run -E goimports,sqlclosecheck,bodyclose,asciicheck,misspell,errorlint --timeout 2m -e "errors.As" -e "errors.Is" ./...
+            golangci-lint run -E goimports,sqlclosecheck,bodyclose,asciicheck,misspell,errorlint --timeout 5m -e "errors.As" -e "errors.Is" ./...
           working_directory: <<parameters.module>>
 
   go-test:
@@ -900,7 +900,7 @@ jobs:
 
     docker:
       - image: returntocorp/semgrep
-    resource_class: xlarge
+    resource_class: medium
     steps:
       - checkout
       - unless:
@@ -942,7 +942,7 @@ jobs:
     machine:
       image: ubuntu-2204:2022.07.1
       docker_layer_caching: true
-      resource_class: xlarge
+      resource_class: large
     steps:
       - attach_workspace:
           at: /tmp/docker_images

op-batcher/batcher/batch_submitter.go

@@ -12,6 +12,7 @@ import (
 	gethrpc "github.com/ethereum/go-ethereum/rpc"
 	"github.com/urfave/cli"
 
+	"github.com/ethereum-optimism/optimism/op-batcher/flags"
 	"github.com/ethereum-optimism/optimism/op-batcher/metrics"
 	"github.com/ethereum-optimism/optimism/op-batcher/rpc"
 	oplog "github.com/ethereum-optimism/optimism/op-service/log"
@@ -30,6 +31,9 @@ const (
 // of a closure allows the parameters bound to the top-level main package, e.g.
 // GitVersion, to be captured and used once the function is executed.
 func Main(version string, cliCtx *cli.Context) error {
+	if err := flags.CheckRequired(cliCtx); err != nil {
+		return err
+	}
 	cfg := NewConfig(cliCtx)
 	if err := cfg.Check(); err != nil {
 		return fmt.Errorf("invalid CLI flags: %w", err)

op-batcher/batcher/channel_manager.go

@@ -82,7 +82,7 @@ func (s *channelManager) TxFailed(id txID) {
 	}
 
 	s.metr.RecordBatchTxFailed()
-	if s.closed && len(s.confirmedTransactions) == 0 && len(s.pendingTransactions) == 0 {
+	if s.closed && len(s.confirmedTransactions) == 0 && len(s.pendingTransactions) == 0 && s.pendingChannel != nil {
 		s.log.Info("Channel has no submitted transactions, clearing for shutdown", "chID", s.pendingChannel.ID())
 		s.clearPendingChannel()
 	}

op-batcher/batcher/driver.go

@@ -191,7 +191,7 @@ func (l *BatchSubmitter) loadBlocksIntoState(ctx context.Context) {
 	if err != nil {
 		l.log.Warn("Error calculating L2 block range", "err", err)
 		return
-	} else if start.Number == end.Number {
+	} else if start.Number >= end.Number {
 		return
 	}
 

op-batcher/cmd/doc/cmd.go

+package doc
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/ethereum-optimism/optimism/op-batcher/metrics"
+	"github.com/olekukonko/tablewriter"
+	"github.com/urfave/cli"
+)
+
+var Subcommands = cli.Commands{
+	{
+		Name:  "metrics",
+		Usage: "Dumps a list of supported metrics to stdout",
+		Flags: []cli.Flag{
+			cli.StringFlag{
+				Name:  "format",
+				Value: "markdown",
+				Usage: "Output format (json|markdown)",
+			},
+		},
+		Action: func(ctx *cli.Context) error {
+			m := metrics.NewMetrics("default")
+			supportedMetrics := m.Document()
+			format := ctx.String("format")
+
+			if format != "markdown" && format != "json" {
+				return fmt.Errorf("invalid format: %s", format)
+			}
+
+			if format == "json" {
+				enc := json.NewEncoder(os.Stdout)
+				return enc.Encode(supportedMetrics)
+			}
+
+			table := tablewriter.NewWriter(os.Stdout)
+			table.SetBorders(tablewriter.Border{Left: true, Top: false, Right: true, Bottom: false})
+			table.SetCenterSeparator("|")
+			table.SetAutoWrapText(false)
+			table.SetHeader([]string{"Metric", "Description", "Labels", "Type"})
+			var data [][]string
+			for _, metric := range supportedMetrics {
+				labels := strings.Join(metric.Labels, ",")
+				data = append(data, []string{metric.Name, metric.Help, labels, metric.Type})
+			}
+			table.AppendBulk(data)
+			table.Render()
+			return nil
+		},
+	},
+}

op-batcher/cmd/main.go

@@ -7,6 +7,7 @@ import (
 	"github.com/urfave/cli"
 
 	"github.com/ethereum-optimism/optimism/op-batcher/batcher"
+	"github.com/ethereum-optimism/optimism/op-batcher/cmd/doc"
 	"github.com/ethereum-optimism/optimism/op-batcher/flags"
 	oplog "github.com/ethereum-optimism/optimism/op-service/log"
 	"github.com/ethereum/go-ethereum/log"
@@ -26,10 +27,15 @@ func main() {
 	app.Version = fmt.Sprintf("%s-%s-%s", Version, GitCommit, GitDate)
 	app.Name = "op-batcher"
 	app.Usage = "Batch Submitter Service"
-	app.Description = "Service for generating and submitting L2 tx batches " +
-		"to L1"
-
+	app.Description = "Service for generating and submitting L2 tx batches to L1"
 	app.Action = curryMain(Version)
+	app.Commands = []cli.Command{
+		{
+			Name:        "doc",
+			Subcommands: doc.Subcommands,
+		},
+	}
+
 	err := app.Run(os.Args)
 	if err != nil {
 		log.Crit("Application failed", "message", err)

op-batcher/flags/flags.go

 package flags
 
 import (
+	"fmt"
+
 	"github.com/urfave/cli"
 
 	"github.com/ethereum-optimism/optimism/op-batcher/rpc"
@@ -19,19 +21,16 @@ var (
 	L1EthRpcFlag = cli.StringFlag{
 		Name:   "l1-eth-rpc",
 		Usage:  "HTTP provider URL for L1",
-		Required: true,
 		EnvVar: opservice.PrefixEnvVar(envVarPrefix, "L1_ETH_RPC"),
 	}
 	L2EthRpcFlag = cli.StringFlag{
 		Name:   "l2-eth-rpc",
 		Usage:  "HTTP provider URL for L2 execution engine",
-		Required: true,
 		EnvVar: opservice.PrefixEnvVar(envVarPrefix, "L2_ETH_RPC"),
 	}
 	RollupRpcFlag = cli.StringFlag{
 		Name:   "rollup-rpc",
 		Usage:  "HTTP provider URL for Rollup node",
-		Required: true,
 		EnvVar: opservice.PrefixEnvVar(envVarPrefix, "ROLLUP_RPC"),
 	}
 	SubSafetyMarginFlag = cli.Uint64Flag{
@@ -39,14 +38,12 @@ var (
 		Usage: "The batcher tx submission safety margin (in #L1-blocks) to subtract " +
 			"from a channel's timeout and sequencing window, to guarantee safe inclusion " +
 			"of a channel on L1.",
-		Required: true,
 		EnvVar: opservice.PrefixEnvVar(envVarPrefix, "SUB_SAFETY_MARGIN"),
 	}
 	PollIntervalFlag = cli.DurationFlag{
 		Name: "poll-interval",
 		Usage: "Delay between querying L2 for more transactions and " +
 			"creating a new batch",
-		Required: true,
 		EnvVar: opservice.PrefixEnvVar(envVarPrefix, "POLL_INTERVAL"),
 	}
 
@@ -108,8 +105,7 @@ var optionalFlags = []cli.Flag{
 }
 
 func init() {
-	requiredFlags = append(requiredFlags, oprpc.CLIFlags(envVarPrefix)...)
-
+	optionalFlags = append(optionalFlags, oprpc.CLIFlags(envVarPrefix)...)
 	optionalFlags = append(optionalFlags, oplog.CLIFlags(envVarPrefix)...)
 	optionalFlags = append(optionalFlags, opmetrics.CLIFlags(envVarPrefix)...)
 	optionalFlags = append(optionalFlags, oppprof.CLIFlags(envVarPrefix)...)
@@ -121,3 +117,12 @@ func init() {
 
 // Flags contains the list of configuration options available to the binary.
 var Flags []cli.Flag
+
+func CheckRequired(ctx *cli.Context) error {
+	for _, f := range requiredFlags {
+		if !ctx.GlobalIsSet(f.GetName()) {
+			return fmt.Errorf("flag %s is required", f.GetName())
+		}
+	}
+	return nil
+}

op-batcher/metrics/metrics.go

@@ -64,6 +64,8 @@ type Metrics struct {
 	ChannelClosedReason     prometheus.Gauge
 	ChannelNumFrames        prometheus.Gauge
 	ChannelComprRatio       prometheus.Histogram
+	ChannelInputBytesTotal  prometheus.Counter
+	ChannelOutputBytesTotal prometheus.Counter
 
 	BatcherTxEvs opmetrics.EventVec
 }
@@ -100,7 +102,7 @@ func NewMetrics(procName string) *Metrics {
 			Help:      "1 if the op-batcher has finished starting up",
 		}),
 
-		ChannelEvs: opmetrics.NewEventVec(factory, ns, "channel", "Channel", []string{"stage"}),
+		ChannelEvs: opmetrics.NewEventVec(factory, ns, "", "channel", "Channel", []string{"stage"}),
 
 		PendingBlocksCount: *factory.NewGaugeVec(prometheus.GaugeOpts{
 			Namespace: ns,
@@ -144,8 +146,18 @@ func NewMetrics(procName string) *Metrics {
 			Help:      "Compression ratios of closed channel.",
 			Buckets:   append([]float64{0.1, 0.2}, prometheus.LinearBuckets(0.3, 0.05, 14)...),
 		}),
+		ChannelInputBytesTotal: factory.NewCounter(prometheus.CounterOpts{
+			Namespace: ns,
+			Name:      "input_bytes_total",
+			Help:      "Total number of bytes to a channel.",
+		}),
+		ChannelOutputBytesTotal: factory.NewCounter(prometheus.CounterOpts{
+			Namespace: ns,
+			Name:      "output_bytes_total",
+			Help:      "Total number of compressed output bytes from a channel.",
+		}),
 
-		BatcherTxEvs: opmetrics.NewEventVec(factory, ns, "batcher_tx", "BatcherTx", []string{"stage"}),
+		BatcherTxEvs: opmetrics.NewEventVec(factory, ns, "", "batcher_tx", "BatcherTx", []string{"stage"}),
 	}
 }
 
@@ -219,6 +231,8 @@ func (m *Metrics) RecordChannelClosed(id derive.ChannelID, numPendingBlocks int,
 	m.ChannelNumFrames.Set(float64(numFrames))
 	m.ChannelInputBytes.WithLabelValues(StageClosed).Set(float64(inputBytes))
 	m.ChannelOutputBytes.Set(float64(outputComprBytes))
+	m.ChannelInputBytesTotal.Add(float64(inputBytes))
+	m.ChannelOutputBytesTotal.Add(float64(outputComprBytes))
 
 	var comprRatio float64
 	if inputBytes > 0 {

op-chain-ops/cmd/withdrawals/main.go

@@ -103,6 +103,10 @@ func main() {
 				Name:  "evm-messages",
 				Usage: "Path to evm-messages.json",
 			},
+			&cli.StringFlag{
+				Name:  "witness-file",
+				Usage: "Path to l2geth witness file",
+			},
 			&cli.StringFlag{
 				Name:  "private-key",
 				Usage: "Key to sign transactions with",
@@ -702,8 +706,9 @@ func newContracts(ctx *cli.Context, l1Backend, l2Backend bind.ContractBackend) (
 func newWithdrawals(ctx *cli.Context, l1ChainID *big.Int) ([]*crossdomain.LegacyWithdrawal, error) {
 	ovmMsgs := ctx.String("ovm-messages")
 	evmMsgs := ctx.String("evm-messages")
+	witnessFile := ctx.String("witness-file")
 
-	log.Debug("Migration data", "ovm-path", ovmMsgs, "evm-messages", evmMsgs)
+	log.Debug("Migration data", "ovm-path", ovmMsgs, "evm-messages", evmMsgs, "witness-file", witnessFile)
 	ovmMessages, err := crossdomain.NewSentMessageFromJSON(ovmMsgs)
 	if err != nil {
 		return nil, err
@@ -716,10 +721,20 @@ func newWithdrawals(ctx *cli.Context, l1ChainID *big.Int) ([]*crossdomain.Legacy
 		ovmMessages = []*crossdomain.SentMessage{}
 	}
 
-	evmMessages, err := crossdomain.NewSentMessageFromJSON(evmMsgs)
+	var evmMessages []*crossdomain.SentMessage
+	if witnessFile != "" {
+		evmMessages, _, err = crossdomain.ReadWitnessData(witnessFile)
 		if err != nil {
 			return nil, err
 		}
+	} else if evmMsgs != "" {
+		evmMessages, err = crossdomain.NewSentMessageFromJSON(evmMsgs)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		return nil, errors.New("must provide either witness file or evm messages")
+	}
 
 	migrationData := crossdomain.MigrationData{
 		OvmMessages: ovmMessages,

op-e2e/actions/blocktime_test.go

@@ -28,12 +28,11 @@ func TestBatchInLastPossibleBlocks(gt *testing.T) {
 
 	signer := types.LatestSigner(sd.L2Cfg.Config)
 	cl := sequencerEngine.EthClient()
+	aliceNonce := uint64(0) // manual nonce management to avoid geth pending-tx nonce non-determinism flakiness
 	aliceTx := func() {
-		n, err := cl.PendingNonceAt(t.Ctx(), dp.Addresses.Alice)
-		require.NoError(t, err)
 		tx := types.MustSignNewTx(dp.Secrets.Alice, signer, &types.DynamicFeeTx{
 			ChainID:   sd.L2Cfg.Config.ChainID,
-			Nonce:     n,
+			Nonce:     aliceNonce,
 			GasTipCap: big.NewInt(2 * params.GWei),
 			GasFeeCap: new(big.Int).Add(miner.l1Chain.CurrentBlock().BaseFee, big.NewInt(2*params.GWei)),
 			Gas:       params.TxGas,
@@ -41,6 +40,7 @@ func TestBatchInLastPossibleBlocks(gt *testing.T) {
 			Value:     e2eutils.Ether(2),
 		})
 		require.NoError(gt, cl.SendTransaction(t.Ctx(), tx))
+		aliceNonce += 1
 	}
 	makeL2BlockWithAliceTx := func() {
 		aliceTx()
@@ -139,12 +139,11 @@ func TestLargeL1Gaps(gt *testing.T) {
 
 	signer := types.LatestSigner(sd.L2Cfg.Config)
 	cl := sequencerEngine.EthClient()
+	aliceNonce := uint64(0) // manual nonce, avoid pending-tx nonce management, that causes flakes
 	aliceTx := func() {
-		n, err := cl.PendingNonceAt(t.Ctx(), dp.Addresses.Alice)
-		require.NoError(t, err)
 		tx := types.MustSignNewTx(dp.Secrets.Alice, signer, &types.DynamicFeeTx{
 			ChainID:   sd.L2Cfg.Config.ChainID,
-			Nonce:     n,
+			Nonce:     aliceNonce,
 			GasTipCap: big.NewInt(2 * params.GWei),
 			GasFeeCap: new(big.Int).Add(miner.l1Chain.CurrentBlock().BaseFee, big.NewInt(2*params.GWei)),
 			Gas:       params.TxGas,
@@ -152,6 +151,7 @@ func TestLargeL1Gaps(gt *testing.T) {
 			Value:     e2eutils.Ether(2),
 		})
 		require.NoError(gt, cl.SendTransaction(t.Ctx(), tx))
+		aliceNonce += 1
 	}
 	makeL2BlockWithAliceTx := func() {
 		aliceTx()

op-e2e/actions/l2_engine_test.go

@@ -191,7 +191,7 @@ func TestL2EngineAPIFail(gt *testing.T) {
 }
 
 func TestEngineAPITests(t *testing.T) {
-	test.RunEngineAPITests(t, func() engineapi.EngineBackend {
+	test.RunEngineAPITests(t, func(t *testing.T) engineapi.EngineBackend {
 		jwtPath := e2eutils.WriteDefaultJWT(t)
 		dp := e2eutils.MakeDeployParams(t, defaultRollupTestParams)
 		sd := e2eutils.Setup(t, dp, defaultAlloc)

op-e2e/actions/sync_test.go

@@ -49,3 +49,46 @@ func TestDerivationWithFlakyL1RPC(gt *testing.T) {
 	// Verifier should be synced, even though it hit lots of temporary L1 RPC errors
 	require.Equal(t, sequencer.L2Unsafe(), verifier.L2Safe(), "verifier is synced")
 }
+
+func TestFinalizeWhileSyncing(gt *testing.T) {
+	t := NewDefaultTesting(gt)
+	dp := e2eutils.MakeDeployParams(t, defaultRollupTestParams)
+	sd := e2eutils.Setup(t, dp, defaultAlloc)
+	log := testlog.Logger(t, log.LvlError) // mute all the temporary derivation errors that we forcefully create
+	_, _, miner, sequencer, _, verifier, _, batcher := setupReorgTestActors(t, dp, sd, log)
+
+	sequencer.ActL2PipelineFull(t)
+	verifier.ActL2PipelineFull(t)
+
+	verifierStartStatus := verifier.SyncStatus()
+
+	// Build an L1 chain with 64 + 1 blocks, containing batches of L2 chain.
+	// Enough to go past the finalityDelay of the engine queue,
+	// to make the verifier finalize while it syncs.
+	miner.ActEmptyBlock(t)
+	for i := 0; i < 64+1; i++ {
+		sequencer.ActL1HeadSignal(t)
+		sequencer.ActL2PipelineFull(t)
+		sequencer.ActBuildToL1Head(t)
+		batcher.ActSubmitAll(t)
+		miner.ActL1StartBlock(12)(t)
+		miner.ActL1IncludeTx(batcher.batcherAddr)(t)
+		miner.ActL1EndBlock(t)
+	}
+	l1Head := miner.l1Chain.CurrentHeader()
+	// finalize all of L1
+	miner.ActL1Safe(t, l1Head.Number.Uint64())
+	miner.ActL1Finalize(t, l1Head.Number.Uint64())
+
+	// Now signal L1 finality to the verifier, while the verifier is not synced.
+	verifier.ActL1HeadSignal(t)
+	verifier.ActL1SafeSignal(t)
+	verifier.ActL1FinalizedSignal(t)
+
+	// Now sync the verifier, without repeating the signal.
+	// While it's syncing, it should finalize on interval now, based on the future L1 finalized block it remembered.
+	verifier.ActL2PipelineFull(t)
+
+	// Verify the verifier finalized something new
+	require.Less(t, verifierStartStatus.FinalizedL2.Number, verifier.SyncStatus().FinalizedL2.Number, "verifier finalized L2 blocks during sync")
+}

op-e2e/system_test.go

@@ -589,8 +589,10 @@ func TestSystemMockP2P(t *testing.T) {
 	}
 
 	cfg := DefaultSystemConfig(t)
-	// Disable batcher, so we don't sync from L1
+	// Disable batcher, so we don't sync from L1 & set a large sequence window so we only have unsafe blocks
 	cfg.DisableBatcher = true
+	cfg.DeployConfig.SequencerWindowSize = 100_000
+	cfg.DeployConfig.MaxSequencerDrift = 100_000
 	// disable at the start, so we don't miss any gossiped blocks.
 	cfg.Nodes["sequencer"].Driver.SequencerStopped = true
 
@@ -640,11 +642,11 @@ func TestSystemMockP2P(t *testing.T) {
 	require.Nil(t, err, "Sending L2 tx to sequencer")
 
 	// Wait for tx to be mined on the L2 sequencer chain
-	receiptSeq, err := waitForTransaction(tx.Hash(), l2Seq, 10*time.Duration(sys.RollupConfig.BlockTime)*time.Second)
+	receiptSeq, err := waitForTransaction(tx.Hash(), l2Seq, 5*time.Minute)
 	require.Nil(t, err, "Waiting for L2 tx on sequencer")
 
 	// Wait until the block it was first included in shows up in the safe chain on the verifier
-	receiptVerif, err := waitForTransaction(tx.Hash(), l2Verif, 10*time.Duration(sys.RollupConfig.BlockTime)*time.Second)
+	receiptVerif, err := waitForTransaction(tx.Hash(), l2Verif, 5*time.Minute)
 	require.Nil(t, err, "Waiting for L2 tx on verifier")
 
 	require.Equal(t, receiptSeq, receiptVerif)

op-node/eth/receipts.go

+package eth
+
+import (
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+// EncodeReceipts encodes a list of receipts into raw receipts. Some non-consensus meta-data may be lost.
+func EncodeReceipts(elems []*types.Receipt) ([]hexutil.Bytes, error) {
+	out := make([]hexutil.Bytes, len(elems))
+	for i, el := range elems {
+		dat, err := el.MarshalBinary()
+		if err != nil {
+			return nil, fmt.Errorf("failed to marshal receipt %d: %w", i, err)
+		}
+		out[i] = dat
+	}
+	return out, nil
+}
+
+// DecodeRawReceipts decodes receipts and adds additional blocks metadata.
+// The contract-deployment addresses are not set however (high cost, depends on nonce values, unused by op-node).
+func DecodeRawReceipts(block BlockID, rawReceipts []hexutil.Bytes, txHashes []common.Hash) ([]*types.Receipt, error) {
+	result := make([]*types.Receipt, len(rawReceipts))
+	totalIndex := uint(0)
+	prevCumulativeGasUsed := uint64(0)
+	for i, r := range rawReceipts {
+		var x types.Receipt
+		if err := x.UnmarshalBinary(r); err != nil {
+			return nil, fmt.Errorf("failed to decode receipt %d: %w", i, err)
+		}
+		x.TxHash = txHashes[i]
+		x.BlockHash = block.Hash
+		x.BlockNumber = new(big.Int).SetUint64(block.Number)
+		x.TransactionIndex = uint(i)
+		x.GasUsed = x.CumulativeGasUsed - prevCumulativeGasUsed
+		// contract address meta-data is not computed.
+		prevCumulativeGasUsed = x.CumulativeGasUsed
+		for _, l := range x.Logs {
+			l.BlockNumber = block.Number
+			l.TxHash = x.TxHash
+			l.TxIndex = uint(i)
+			l.BlockHash = block.Hash
+			l.Index = totalIndex
+			totalIndex += 1
+		}
+		result[i] = &x
+	}
+	return result, nil
+}

op-node/eth/transactions.go

+package eth
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+// EncodeTransactions encodes a list of transactions into opaque transactions.
+func EncodeTransactions(elems []*types.Transaction) ([]hexutil.Bytes, error) {
+	out := make([]hexutil.Bytes, len(elems))
+	for i, el := range elems {
+		dat, err := el.MarshalBinary()
+		if err != nil {
+			return nil, fmt.Errorf("failed to marshal tx %d: %w", i, err)
+		}
+		out[i] = dat
+	}
+	return out, nil
+}
+
+// DecodeTransactions decodes a list of opaque transactions into transactions.
+func DecodeTransactions(data []hexutil.Bytes) ([]*types.Transaction, error) {
+	dest := make([]*types.Transaction, len(data))
+	for i := range dest {
+		var x types.Transaction
+		if err := x.UnmarshalBinary(data[i]); err != nil {
+			return nil, fmt.Errorf("failed to unmarshal tx %d: %w", i, err)
+		}
+		dest[i] = &x
+	}
+	return dest, nil
+}
+
+// TransactionsToHashes computes the transaction-hash for every transaction in the input.
+func TransactionsToHashes(elems []*types.Transaction) []common.Hash {
+	out := make([]common.Hash, len(elems))
+	for i, el := range elems {
+		out[i] = el.Hash()
+	}
+	return out
+}

op-node/flags/flags.go

@@ -256,28 +256,10 @@ func init() {
 }
 
 func CheckRequired(ctx *cli.Context) error {
-	l1NodeAddr := ctx.GlobalString(L1NodeAddr.Name)
-	if l1NodeAddr == "" {
-		return fmt.Errorf("flag %s is required", L1NodeAddr.Name)
+	for _, f := range requiredFlags {
+		if !ctx.GlobalIsSet(f.GetName()) {
+			return fmt.Errorf("flag %s is required", f.GetName())
 		}
-	l2EngineAddr := ctx.GlobalString(L2EngineAddr.Name)
-	if l2EngineAddr == "" {
-		return fmt.Errorf("flag %s is required", L2EngineAddr.Name)
-	}
-	rollupConfig := ctx.GlobalString(RollupConfig.Name)
-	network := ctx.GlobalString(Network.Name)
-	if rollupConfig == "" && network == "" {
-		return fmt.Errorf("flag %s or %s is required", RollupConfig.Name, Network.Name)
-	}
-	if rollupConfig != "" && network != "" {
-		return fmt.Errorf("cannot specify both %s and %s", RollupConfig.Name, Network.Name)
-	}
-	rpcListenAddr := ctx.GlobalString(RPCListenAddr.Name)
-	if rpcListenAddr == "" {
-		return fmt.Errorf("flag %s is required", RPCListenAddr.Name)
-	}
-	if !ctx.GlobalIsSet(RPCListenPort.Name) {
-		return fmt.Errorf("flag %s is required", RPCListenPort.Name)
 	}
 	return nil
 }

op-node/node/api.go

@@ -9,7 +9,6 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/log"
 
-	"github.com/ethereum-optimism/optimism/op-bindings/bindings"
 	"github.com/ethereum-optimism/optimism/op-bindings/predeploys"
 	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
@@ -115,12 +114,7 @@ func (n *nodeAPI) OutputAtBlock(ctx context.Context, number hexutil.Uint64) (*et
 	}
 
 	var l2OutputRootVersion eth.Bytes32 // it's zero for now
-	l2OutputRoot, err := rollup.ComputeL2OutputRoot(&bindings.TypesOutputRootProof{
-		Version:                  l2OutputRootVersion,
-		StateRoot:                head.Root(),
-		MessagePasserStorageRoot: proof.StorageHash,
-		LatestBlockhash:          head.Hash(),
-	})
+	l2OutputRoot, err := rollup.ComputeL2OutputRootV0(head, proof.StorageHash)
 	if err != nil {
 		n.log.Error("Error computing L2 output root, nil ptr passed to hashing function")
 		return nil, err

op-node/rollup/derive/engine_queue.go

@@ -17,6 +17,11 @@ import (
 	"github.com/ethereum-optimism/optimism/op-node/rollup/sync"
 )
 
+type attributesWithParent struct {
+	attributes *eth.PayloadAttributes
+	parent     eth.L2BlockRef
+}
+
 type NextAttributesProvider interface {
 	Origin() eth.L1BlockRef
 	NextAttributes(context.Context, eth.L2BlockRef) (*eth.PayloadAttributes, error)
@@ -76,6 +81,10 @@ const maxUnsafePayloadsMemory = 500 * 1024 * 1024
 // And then we add 1 to make pruning easier by leaving room for a new item without pruning the 32*4.
 const finalityLookback = 4*32 + 1
 
+// finalityDelay is the number of L1 blocks to traverse before trying to finalize L2 blocks again.
+// We do not want to do this too often, since it requires fetching a L1 block by number, so no cache data.
+const finalityDelay = 64
+
 type FinalityData struct {
 	// The last L2 block that was fully derived and inserted into the L2 engine while processing this L1 block.
 	L2Block eth.L2BlockRef
@@ -102,11 +111,15 @@ type EngineQueue struct {
 	// This update may repeat if the engine returns a temporary error.
 	needForkchoiceUpdate bool
 
+	// finalizedL1 is the currently perceived finalized L1 block.
+	// This may be ahead of the current traversed origin when syncing.
 	finalizedL1 eth.L1BlockRef
 
+	// triedFinalizeAt tracks at which origin we last tried to finalize during sync.
+	triedFinalizeAt eth.L1BlockRef
+
 	// The queued-up attributes
-	safeAttributesParent eth.L2BlockRef
-	safeAttributes       *eth.PayloadAttributes
+	safeAttributes *attributesWithParent
 	unsafePayloads *PayloadsQueue // queue of unsafe payloads, ordered by ascending block number, may have gaps and duplicates
 
 	// Tracks which L2 blocks where last derived from which L1 block. At most finalityLookback large.
@@ -171,17 +184,23 @@ func (eq *EngineQueue) Finalize(l1Origin eth.L1BlockRef) {
 		eq.log.Error("ignoring old L1 finalized block signal! Is the L1 provider corrupted?", "prev_finalized_l1", eq.finalizedL1, "signaled_finalized_l1", l1Origin)
 		return
 	}
-	// Perform a safety check: the L1 finalization signal is only accepted if we previously processed the L1 block.
-	// This prevents a corrupt L1 provider from tricking us in recognizing a L1 block inconsistent with the L1 chain we are on.
-	// Missing a finality signal due to empty buffer is fine, it will finalize when the buffer is filled again.
+
+	// remember the L1 finalization signal
+	eq.finalizedL1 = l1Origin
+
+	// Sanity check: we only try to finalize L2 immediately, without fetching additional data,
+	// if we are on the same chain as the signal.
+	// If we are on a different chain, the signal will be ignored,
+	// and tryFinalizeL1Origin() will eventually detect that we are on the wrong chain,
+	// if not resetting due to reorg elsewhere already.
 	for _, fd := range eq.finalityData {
 		if fd.L1Block == l1Origin.ID() {
-			eq.finalizedL1 = l1Origin
 			eq.tryFinalizeL2()
 			return
 		}
 	}
-	eq.log.Warn("ignoring finalization signal for unknown L1 block, waiting for new L1 blocks in buffer", "prev_finalized_l1", eq.finalizedL1, "signaled_finalized_l1", l1Origin)
+
+	eq.log.Info("received L1 finality signal, but missing data for immediate L2 finalization", "prev_finalized_l1", eq.finalizedL1, "signaled_finalized_l1", l1Origin)
 }
 
 // FinalizedL1 identifies the L1 chain (incl.) that included and/or produced all the finalized L2 blocks.
@@ -217,14 +236,20 @@ func (eq *EngineQueue) Step(ctx context.Context) error {
 	}
 	eq.origin = newOrigin
 	eq.postProcessSafeL2() // make sure we track the last L2 safe head for every new L1 block
+	// try to finalize the L2 blocks we have synced so far (no-op if L1 finality is behind)
+	if err := eq.tryFinalizePastL2Blocks(ctx); err != nil {
+		return err
+	}
 	if next, err := eq.prev.NextAttributes(ctx, eq.safeHead); err == io.EOF {
 		outOfData = true
 	} else if err != nil {
 		return err
 	} else {
-		eq.safeAttributes = next
-		eq.safeAttributesParent = eq.safeHead
-		eq.log.Debug("Adding next safe attributes", "safe_head", eq.safeHead, "next", eq.safeAttributes)
+		eq.safeAttributes = &attributesWithParent{
+			attributes: next,
+			parent:     eq.safeHead,
+		}
+		eq.log.Debug("Adding next safe attributes", "safe_head", eq.safeHead, "next", next)
 		return NotEnoughData
 	}
 
@@ -271,6 +296,38 @@ func (eq *EngineQueue) verifyNewL1Origin(ctx context.Context, newOrigin eth.L1Bl
 	return nil
 }
 
+func (eq *EngineQueue) tryFinalizePastL2Blocks(ctx context.Context) error {
+	if eq.finalizedL1 == (eth.L1BlockRef{}) {
+		return nil
+	}
+
+	// If the L1 is finalized beyond the point we are traversing (e.g. during sync),
+	// then we should check if we can finalize this L1 block we are traversing.
+	// Otherwise, nothing to act on here, we will finalize later on a new finality signal matching the recent history.
+	if eq.finalizedL1.Number < eq.origin.Number {
+		return nil
+	}
+
+	// If we recently tried finalizing, then don't try again just yet, but traverse more of L1 first.
+	if eq.triedFinalizeAt != (eth.L1BlockRef{}) && eq.origin.Number <= eq.triedFinalizeAt.Number+finalityDelay {
+		return nil
+	}
+
+	eq.log.Info("processing L1 finality information", "l1_finalized", eq.finalizedL1, "l1_origin", eq.origin, "previous", eq.triedFinalizeAt)
+
+	// Sanity check we are indeed on the finalizing chain, and not stuck on something else.
+	// We assume that the block-by-number query is consistent with the previously received finalized chain signal
+	ref, err := eq.l1Fetcher.L1BlockRefByNumber(ctx, eq.origin.Number)
+	if err != nil {
+		return NewTemporaryError(fmt.Errorf("failed to check if on finalizing L1 chain: %w", err))
+	}
+	if ref.Hash != eq.origin.Hash {
+		return NewResetError(fmt.Errorf("need to reset, we are on %s, not on the finalizing L1 chain %s (towards %s)", eq.origin, ref, eq.finalizedL1))
+	}
+	eq.tryFinalizeL2()
+	return nil
+}
+
 // tryFinalizeL2 traverses the past L1 blocks, checks if any has been finalized,
 // and then marks the latest fully derived L2 block from this as finalized,
 // or defaults to the current finalized L2 block.
@@ -278,6 +335,7 @@ func (eq *EngineQueue) tryFinalizeL2() {
 	if eq.finalizedL1 == (eth.L1BlockRef{}) {
 		return // if no L1 information is finalized yet, then skip this
 	}
+	eq.triedFinalizeAt = eq.origin
 	// default to keep the same finalized block
 	finalizedL2 := eq.finalized
 	// go through the latest inclusion data, and find the last L2 block that was derived from a finalized L1 block
@@ -430,16 +488,20 @@ func (eq *EngineQueue) tryNextSafeAttributes(ctx context.Context) error {
 		return nil
 	}
 	// validate the safe attributes before processing them. The engine may have completed processing them through other means.
-	if eq.safeHead != eq.safeAttributesParent {
-		if eq.safeHead.ParentHash != eq.safeAttributesParent.Hash {
-			return NewResetError(fmt.Errorf("safe head changed to %s with parent %s, conflicting with queued safe attributes on top of %s",
-				eq.safeHead, eq.safeHead.ParentID(), eq.safeAttributesParent))
-		}
-		eq.log.Warn("queued safe attributes are stale, safe-head progressed",
-			"safe_head", eq.safeHead, "safe_head_parent", eq.safeHead.ParentID(), "attributes_parent", eq.safeAttributesParent)
+	if eq.safeHead != eq.safeAttributes.parent {
+		// Previously the attribute's parent was the safe head. If the safe head advances so safe head's parent is the same as the
+		// attribute's parent then we need to cancel the attributes.
+		if eq.safeHead.ParentHash == eq.safeAttributes.parent.Hash {
+			eq.log.Warn("queued safe attributes are stale, safehead progressed",
+				"safe_head", eq.safeHead, "safe_head_parent", eq.safeHead.ParentID(), "attributes_parent", eq.safeAttributes.parent)
 			eq.safeAttributes = nil
 			return nil
 		}
+		// If something other than a simple advance occurred, perform a full reset
+		return NewResetError(fmt.Errorf("safe head changed to %s with parent %s, conflicting with queued safe attributes on top of %s",
+			eq.safeHead, eq.safeHead.ParentID(), eq.safeAttributes.parent))
+
+	}
 	if eq.safeHead.Number < eq.unsafeHead.Number {
 		return eq.consolidateNextSafeAttributes(ctx)
 	} else if eq.safeHead.Number == eq.unsafeHead.Number {
@@ -468,7 +530,7 @@ func (eq *EngineQueue) consolidateNextSafeAttributes(ctx context.Context) error
 		}
 		return NewTemporaryError(fmt.Errorf("failed to get existing unsafe payload to compare against derived attributes from L1: %w", err))
 	}
-	if err := AttributesMatchBlock(eq.safeAttributes, eq.safeHead.Hash, payload, eq.log); err != nil {
+	if err := AttributesMatchBlock(eq.safeAttributes.attributes, eq.safeHead.Hash, payload, eq.log); err != nil {
 		eq.log.Warn("L2 reorg: existing unsafe block does not match derived attributes from L1", "err", err, "unsafe", eq.unsafeHead, "safe", eq.safeHead)
 		// geth cannot wind back a chain without reorging to a new, previously non-canonical, block
 		return eq.forceNextSafeAttributes(ctx)
@@ -493,7 +555,7 @@ func (eq *EngineQueue) forceNextSafeAttributes(ctx context.Context) error {
 	if eq.safeAttributes == nil {
 		return nil
 	}
-	attrs := eq.safeAttributes
+	attrs := eq.safeAttributes.attributes
 	errType, err := eq.StartPayload(ctx, eq.safeHead, attrs, true)
 	if err == nil {
 		_, errType, err = eq.ConfirmPayload(ctx)
@@ -664,10 +726,12 @@ func (eq *EngineQueue) Reset(ctx context.Context, _ eth.L1BlockRef, _ eth.System
 	eq.log.Debug("Reset engine queue", "safeHead", safe, "unsafe", unsafe, "safe_timestamp", safe.Time, "unsafe_timestamp", unsafe.Time, "l1Origin", l1Origin)
 	eq.unsafeHead = unsafe
 	eq.safeHead = safe
+	eq.safeAttributes = nil
 	eq.finalized = finalized
 	eq.resetBuildingState()
 	eq.needForkchoiceUpdate = true
 	eq.finalityData = eq.finalityData[:0]
+	// note: finalizedL1 and triedFinalizeAt do not reset, since these do not change between reorgs.
 	// note: we do not clear the unsafe payloads queue; if the payloads are not applicable anymore the parent hash checks will clear out the old payloads.
 	eq.origin = pipelineOrigin
 	eq.sysCfg = l1Cfg

op-node/rollup/derive/engine_queue_test.go

@@ -15,6 +15,7 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 
 	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum-optimism/optimism/op-node/metrics"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
 	"github.com/ethereum-optimism/optimism/op-node/testlog"
 	"github.com/ethereum-optimism/optimism/op-node/testutils"
@@ -1007,3 +1008,102 @@ func TestBlockBuildingRace(t *testing.T) {
 	l1F.AssertExpectations(t)
 	eng.AssertExpectations(t)
 }
+
+func TestResetLoop(t *testing.T) {
+	logger := testlog.Logger(t, log.LvlInfo)
+	eng := &testutils.MockEngine{}
+	l1F := &testutils.MockL1Source{}
+
+	rng := rand.New(rand.NewSource(1234))
+
+	refA := testutils.RandomBlockRef(rng)
+	refA0 := eth.L2BlockRef{
+		Hash:           testutils.RandomHash(rng),
+		Number:         0,
+		ParentHash:     common.Hash{},
+		Time:           refA.Time,
+		L1Origin:       refA.ID(),
+		SequenceNumber: 0,
+	}
+	gasLimit := eth.Uint64Quantity(20_000_000)
+	cfg := &rollup.Config{
+		Genesis: rollup.Genesis{
+			L1:     refA.ID(),
+			L2:     refA0.ID(),
+			L2Time: refA0.Time,
+			SystemConfig: eth.SystemConfig{
+				BatcherAddr: common.Address{42},
+				Overhead:    [32]byte{123},
+				Scalar:      [32]byte{42},
+				GasLimit:    20_000_000,
+			},
+		},
+		BlockTime:     1,
+		SeqWindowSize: 2,
+	}
+	refA1 := eth.L2BlockRef{
+		Hash:           testutils.RandomHash(rng),
+		Number:         refA0.Number + 1,
+		ParentHash:     refA0.Hash,
+		Time:           refA0.Time + cfg.BlockTime,
+		L1Origin:       refA.ID(),
+		SequenceNumber: 1,
+	}
+	refA2 := eth.L2BlockRef{
+		Hash:           testutils.RandomHash(rng),
+		Number:         refA1.Number + 1,
+		ParentHash:     refA1.Hash,
+		Time:           refA1.Time + cfg.BlockTime,
+		L1Origin:       refA.ID(),
+		SequenceNumber: 2,
+	}
+
+	attrs := &eth.PayloadAttributes{
+		Timestamp:             eth.Uint64Quantity(refA2.Time),
+		PrevRandao:            eth.Bytes32{},
+		SuggestedFeeRecipient: common.Address{},
+		Transactions:          nil,
+		NoTxPool:              false,
+		GasLimit:              &gasLimit,
+	}
+
+	eng.ExpectL2BlockRefByLabel(eth.Finalized, refA0, nil)
+	eng.ExpectL2BlockRefByLabel(eth.Safe, refA1, nil)
+	eng.ExpectL2BlockRefByLabel(eth.Unsafe, refA2, nil)
+	eng.ExpectL2BlockRefByHash(refA1.Hash, refA1, nil)
+	eng.ExpectL2BlockRefByHash(refA0.Hash, refA0, nil)
+	eng.ExpectSystemConfigByL2Hash(refA0.Hash, cfg.Genesis.SystemConfig, nil)
+	l1F.ExpectL1BlockRefByNumber(refA.Number, refA, nil)
+	l1F.ExpectL1BlockRefByHash(refA.Hash, refA, nil)
+	l1F.ExpectL1BlockRefByHash(refA.Hash, refA, nil)
+
+	prev := &fakeAttributesQueue{origin: refA, attrs: attrs}
+
+	eq := NewEngineQueue(logger, cfg, eng, metrics.NoopMetrics, prev, l1F)
+	eq.unsafeHead = refA2
+	eq.safeHead = refA1
+	eq.finalized = refA0
+
+	// Qeueue up the safe attributes
+	require.Nil(t, eq.safeAttributes)
+	require.ErrorIs(t, eq.Step(context.Background()), NotEnoughData)
+	require.NotNil(t, eq.safeAttributes)
+
+	// Peform the reset
+	require.ErrorIs(t, eq.Reset(context.Background(), eth.L1BlockRef{}, eth.SystemConfig{}), io.EOF)
+
+	// Expect a FCU after the reset
+	preFc := &eth.ForkchoiceState{
+		HeadBlockHash:      refA2.Hash,
+		SafeBlockHash:      refA0.Hash,
+		FinalizedBlockHash: refA0.Hash,
+	}
+	eng.ExpectForkchoiceUpdate(preFc, nil, nil, nil)
+	require.NoError(t, eq.Step(context.Background()), "clean forkchoice state after reset")
+
+	// Crux of the test. Should be in a valid state after the reset.
+	require.ErrorIs(t, eq.Step(context.Background()), NotEnoughData, "Should be able to step after a reset")
+
+	l1F.AssertExpectations(t)
+	eng.AssertExpectations(t)
+}

op-node/rollup/output_root.go

@@ -24,3 +24,13 @@ func ComputeL2OutputRoot(proofElements *bindings.TypesOutputRootProof) (eth.Byte
 	)
 	return eth.Bytes32(digest), nil
 }
+
+func ComputeL2OutputRootV0(block eth.BlockInfo, storageRoot [32]byte) (eth.Bytes32, error) {
+	var l2OutputRootVersion eth.Bytes32 // it's zero for now
+	return ComputeL2OutputRoot(&bindings.TypesOutputRootProof{
+		Version:                  l2OutputRootVersion,
+		StateRoot:                block.Root(),
+		MessagePasserStorageRoot: storageRoot,
+		LatestBlockhash:          block.Hash(),
+	})
+}

op-node/sources/batching.go

@@ -24,6 +24,7 @@ type IterativeBatchCall[K any, V any] struct {
 
 	makeRequest func(K) (V, rpc.BatchElem)
 	getBatch    BatchCallContextFn
+	getSingle   CallContextFn
 
 	requestsValues []V
 	scheduled      chan rpc.BatchElem
@@ -35,6 +36,7 @@ func NewIterativeBatchCall[K any, V any](
 	requestsKeys []K,
 	makeRequest func(K) (V, rpc.BatchElem),
 	getBatch BatchCallContextFn,
+	getSingle CallContextFn,
 	batchSize int) *IterativeBatchCall[K, V] {
 
 	if len(requestsKeys) < batchSize {
@@ -47,6 +49,7 @@ func NewIterativeBatchCall[K any, V any](
 	out := &IterativeBatchCall[K, V]{
 		completed:    0,
 		getBatch:     getBatch,
+		getSingle:    getSingle,
 		requestsKeys: requestsKeys,
 		batchSize:    batchSize,
 		makeRequest:  makeRequest,
@@ -84,6 +87,11 @@ func (ibc *IterativeBatchCall[K, V]) Fetch(ctx context.Context) error {
 	ibc.resetLock.RLock()
 	defer ibc.resetLock.RUnlock()
 
+	// return early if context is Done
+	if ctx.Err() != nil {
+		return ctx.Err()
+	}
+
 	// collect a batch from the requests channel
 	batch := make([]rpc.BatchElem, 0, ibc.batchSize)
 	// wait for first element
@@ -119,12 +127,24 @@ func (ibc *IterativeBatchCall[K, V]) Fetch(ctx context.Context) error {
 		break
 	}
 
+	if len(batch) == 0 {
+		return nil
+	}
+
+	if ibc.batchSize == 1 {
+		first := batch[0]
+		if err := ibc.getSingle(ctx, &first.Result, first.Method, first.Args...); err != nil {
+			ibc.scheduled <- first
+			return err
+		}
+	} else {
 		if err := ibc.getBatch(ctx, batch); err != nil {
 			for _, r := range batch {
 				ibc.scheduled <- r
 			}
 			return fmt.Errorf("failed batch-retrieval: %w", err)
 		}
+	}
 	var result error
 	for _, elem := range batch {
 		if elem.Error != nil {

op-node/sources/batching_test.go

@@ -35,6 +35,7 @@ type batchTestCase struct {
 	batchSize int
 
 	batchCalls  []batchCall
+	singleCalls []elemCall
 
 	mock.Mock
 }
@@ -53,7 +54,14 @@ func (tc *batchTestCase) GetBatch(ctx context.Context, b []rpc.BatchElem) error
 	if ctx.Err() != nil {
 		return ctx.Err()
 	}
-	return tc.Mock.MethodCalled("get", b).Get(0).([]error)[0]
+	return tc.Mock.MethodCalled("getBatch", b).Get(0).([]error)[0]
+}
+
+func (tc *batchTestCase) GetSingle(ctx context.Context, result any, method string, args ...any) error {
+	if ctx.Err() != nil {
+		return ctx.Err()
+	}
+	return tc.Mock.MethodCalled("getSingle", (*(result.(*interface{}))).(*string), method, args[0]).Get(0).([]error)[0]
 }
 
 var mockErr = errors.New("mockErr")
@@ -64,7 +72,7 @@ func (tc *batchTestCase) Run(t *testing.T) {
 		keys[i] = i
 	}
 
-	makeMock := func(bci int, bc batchCall) func(args mock.Arguments) {
+	makeBatchMock := func(bc batchCall) func(args mock.Arguments) {
 		return func(args mock.Arguments) {
 			batch := args[0].([]rpc.BatchElem)
 			for i, elem := range batch {
@@ -83,7 +91,7 @@ func (tc *batchTestCase) Run(t *testing.T) {
 		}
 	}
 	// mock all the results of the batch calls
-	for bci, bc := range tc.batchCalls {
+	for _, bc := range tc.batchCalls {
 		var batch []rpc.BatchElem
 		for _, elem := range bc.elems {
 			batch = append(batch, rpc.BatchElem{
@@ -94,10 +102,30 @@ func (tc *batchTestCase) Run(t *testing.T) {
 			})
 		}
 		if len(bc.elems) > 0 {
-			tc.On("get", batch).Once().Run(makeMock(bci, bc)).Return([]error{bc.rpcErr}) // wrap to preserve nil as type of error
+			tc.On("getBatch", batch).Once().Run(makeBatchMock(bc)).Return([]error{bc.rpcErr}) // wrap to preserve nil as type of error
+		}
+	}
+	makeSingleMock := func(ec elemCall) func(args mock.Arguments) {
+		return func(args mock.Arguments) {
+			result := args[0].(*string)
+			id := args[2].(int)
+			require.Equal(t, ec.id, id, "element should match expected element")
+			if ec.err {
+				*result = ""
+			} else {
+				*result = fmt.Sprintf("mock result id %d", id)
+			}
+		}
+	}
+	// mock the results of unbatched calls
+	for _, ec := range tc.singleCalls {
+		var ret error
+		if ec.err {
+			ret = mockErr
 		}
+		tc.On("getSingle", new(string), "testing_foobar", ec.id).Once().Run(makeSingleMock(ec)).Return([]error{ret})
 	}
-	iter := NewIterativeBatchCall[int, *string](keys, makeTestRequest, tc.GetBatch, tc.batchSize)
+	iter := NewIterativeBatchCall[int, *string](keys, makeTestRequest, tc.GetBatch, tc.GetSingle, tc.batchSize)
 	for i, bc := range tc.batchCalls {
 		ctx := context.Background()
 		if bc.makeCtx != nil {
@@ -116,6 +144,20 @@ func (tc *batchTestCase) Run(t *testing.T) {
 			}
 		}
 	}
+	for i, ec := range tc.singleCalls {
+		ctx := context.Background()
+		err := iter.Fetch(ctx)
+		if err == io.EOF {
+			require.Equal(t, i, len(tc.singleCalls)-1, "EOF only on last call")
+		} else {
+			require.False(t, iter.Complete())
+			if ec.err {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+		}
+	}
 	require.True(t, iter.Complete(), "batch iter should be complete after the expected calls")
 	out, err := iter.Result()
 	require.NoError(t, err)
@@ -154,6 +196,37 @@ func TestFetchBatched(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:      "single element",
+			items:     1,
+			batchSize: 4,
+			singleCalls: []elemCall{
+				{id: 0, err: false},
+			},
+		},
+		{
+			name:      "unbatched",
+			items:     4,
+			batchSize: 1,
+			singleCalls: []elemCall{
+				{id: 0, err: false},
+				{id: 1, err: false},
+				{id: 2, err: false},
+				{id: 3, err: false},
+			},
+		},
+		{
+			name:      "unbatched with retry",
+			items:     4,
+			batchSize: 1,
+			singleCalls: []elemCall{
+				{id: 0, err: false},
+				{id: 1, err: true},
+				{id: 2, err: false},
+				{id: 3, err: false},
+				{id: 1, err: false},
+			},
+		},
 		{
 			name:      "split",
 			items:     5,
@@ -240,7 +313,7 @@ func TestFetchBatched(t *testing.T) {
 		},
 		{
 			name:      "context timeout",
-			items:     1,
+			items:     2,
 			batchSize: 3,
 			batchCalls: []batchCall{
 				{
@@ -255,6 +328,7 @@ func TestFetchBatched(t *testing.T) {
 				{
 					elems: []elemCall{
 						{id: 0, err: false},
+						{id: 1, err: false},
 					},
 					err: "",
 				},

op-node/sources/eth_client.go

@@ -356,10 +356,7 @@ func (s *EthClient) FetchReceipts(ctx context.Context, blockHash common.Hash) (e
 	if v, ok := s.receiptsCache.Get(blockHash); ok {
 		job = v.(*receiptsFetchingJob)
 	} else {
-		txHashes := make([]common.Hash, len(txs))
-		for i := 0; i < len(txs); i++ {
-			txHashes[i] = txs[i].Hash()
-		}
+		txHashes := eth.TransactionsToHashes(txs)
 		job = NewReceiptsFetchingJob(s, s.client, s.maxBatchSize, eth.ToBlockID(info), info.ReceiptHash(), txHashes)
 		s.receiptsCache.Add(blockHash, job)
 	}

op-node/sources/receipts.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"math/big"
 	"sync"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -373,6 +372,7 @@ func (job *receiptsFetchingJob) runFetcher(ctx context.Context) error {
 			job.txHashes,
 			makeReceiptRequest,
 			job.client.BatchCallContext,
+			job.client.CallContext,
 			job.maxBatchSize,
 		)
 	}
@@ -419,29 +419,7 @@ func (job *receiptsFetchingJob) runAltMethod(ctx context.Context, m ReceiptsFetc
 		err = job.client.CallContext(ctx, &rawReceipts, "debug_getRawReceipts", job.block.Hash)
 		if err == nil {
 			if len(rawReceipts) == len(job.txHashes) {
-				result = make([]*types.Receipt, len(rawReceipts))
-				totalIndex := uint(0)
-				prevCumulativeGasUsed := uint64(0)
-				for i, r := range rawReceipts {
-					var x types.Receipt
-					_ = x.UnmarshalBinary(r) // safe to ignore, we verify receipts against the receipts hash later
-					x.TxHash = job.txHashes[i]
-					x.BlockHash = job.block.Hash
-					x.BlockNumber = new(big.Int).SetUint64(job.block.Number)
-					x.TransactionIndex = uint(i)
-					x.GasUsed = x.CumulativeGasUsed - prevCumulativeGasUsed
-					// contract address meta-data is not computed.
-					prevCumulativeGasUsed = x.CumulativeGasUsed
-					for _, l := range x.Logs {
-						l.BlockNumber = job.block.Number
-						l.TxHash = x.TxHash
-						l.TxIndex = uint(i)
-						l.BlockHash = job.block.Hash
-						l.Index = totalIndex
-						totalIndex += 1
-					}
-					result[i] = &x
-				}
+				result, err = eth.DecodeRawReceipts(job.block, rawReceipts, job.txHashes)
 			} else {
 				err = fmt.Errorf("got %d raw receipts, but expected %d", len(rawReceipts), len(job.txHashes))
 			}

op-node/testutils/mock_eth_client.go

@@ -83,8 +83,8 @@ func (m *MockEthClient) PayloadByNumber(ctx context.Context, n uint64) (*eth.Exe
 	return out[0].(*eth.ExecutionPayload), *out[1].(*error)
 }
 
-func (m *MockEthClient) ExpectPayloadByNumber(hash common.Hash, payload *eth.ExecutionPayload, err error) {
-	m.Mock.On("PayloadByNumber", hash).Once().Return(payload, &err)
+func (m *MockEthClient) ExpectPayloadByNumber(n uint64, payload *eth.ExecutionPayload, err error) {
+	m.Mock.On("PayloadByNumber", n).Once().Return(payload, &err)
 }
 
 func (m *MockEthClient) PayloadByLabel(ctx context.Context, label eth.BlockLabel) (*eth.ExecutionPayload, error) {

op-program/client/driver/driver.go

@@ -18,17 +18,24 @@ type Derivation interface {
 	SafeL2Head() eth.L2BlockRef
 }
 
+type L2Source interface {
+	derive.Engine
+	L2OutputRoot() (eth.Bytes32, error)
+}
+
 type Driver struct {
 	logger       log.Logger
 	pipeline     Derivation
+	l2OutputRoot func() (eth.Bytes32, error)
 }
 
-func NewDriver(logger log.Logger, cfg *rollup.Config, l1Source derive.L1Fetcher, l2Source derive.Engine) *Driver {
+func NewDriver(logger log.Logger, cfg *rollup.Config, l1Source derive.L1Fetcher, l2Source L2Source) *Driver {
 	pipeline := derive.NewDerivationPipeline(logger, cfg, l1Source, l2Source, metrics.NoopMetrics)
 	pipeline.Reset()
 	return &Driver{
 		logger:       logger,
 		pipeline:     pipeline,
+		l2OutputRoot: l2Source.L2OutputRoot,
 	}
 }
 
@@ -51,3 +58,13 @@ func (d *Driver) Step(ctx context.Context) error {
 func (d *Driver) SafeHead() eth.L2BlockRef {
 	return d.pipeline.SafeL2Head()
 }
+
+func (d *Driver) ValidateClaim(claimedOutputRoot eth.Bytes32) bool {
+	outputRoot, err := d.l2OutputRoot()
+	if err != nil {
+		d.logger.Info("Failed to calculate L2 output root", "err", err)
+		return false
+	}
+	d.logger.Info("Derivation complete", "head", d.SafeHead(), "output", outputRoot, "claim", claimedOutputRoot)
+	return claimedOutputRoot == outputRoot
+}

op-program/client/driver/driver_test.go

@@ -45,6 +45,36 @@ func TestNoError(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestValidateClaim(t *testing.T) {
+	t.Run("Valid", func(t *testing.T) {
+		driver := createDriver(t, io.EOF)
+		expected := eth.Bytes32{0x11}
+		driver.l2OutputRoot = func() (eth.Bytes32, error) {
+			return expected, nil
+		}
+		valid := driver.ValidateClaim(expected)
+		require.True(t, valid)
+	})
+
+	t.Run("Invalid", func(t *testing.T) {
+		driver := createDriver(t, io.EOF)
+		driver.l2OutputRoot = func() (eth.Bytes32, error) {
+			return eth.Bytes32{0x22}, nil
+		}
+		valid := driver.ValidateClaim(eth.Bytes32{0x11})
+		require.False(t, valid)
+	})
+
+	t.Run("Error", func(t *testing.T) {
+		driver := createDriver(t, io.EOF)
+		driver.l2OutputRoot = func() (eth.Bytes32, error) {
+			return eth.Bytes32{}, errors.New("boom")
+		}
+		valid := driver.ValidateClaim(eth.Bytes32{0x11})
+		require.False(t, valid)
+	})
+}
+
 func createDriver(t *testing.T, derivationResult error) *Driver {
 	derivation := &stubDerivation{nextErr: derivationResult}
 	return &Driver{

op-program/client/l1/cache.go

+package l1
+
+import (
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/hashicorp/golang-lru/v2/simplelru"
+)
+
+// Cache size is quite high as retrieving data from the pre-image oracle can be quite expensive
+const cacheSize = 2000
+
+// CachingOracle is an implementation of Oracle that delegates to another implementation, adding caching of all results
+type CachingOracle struct {
+	oracle Oracle
+	blocks *simplelru.LRU[common.Hash, eth.BlockInfo]
+	txs    *simplelru.LRU[common.Hash, types.Transactions]
+	rcpts  *simplelru.LRU[common.Hash, types.Receipts]
+}
+
+func NewCachingOracle(oracle Oracle) *CachingOracle {
+	blockLRU, _ := simplelru.NewLRU[common.Hash, eth.BlockInfo](cacheSize, nil)
+	txsLRU, _ := simplelru.NewLRU[common.Hash, types.Transactions](cacheSize, nil)
+	rcptsLRU, _ := simplelru.NewLRU[common.Hash, types.Receipts](cacheSize, nil)
+	return &CachingOracle{
+		oracle: oracle,
+		blocks: blockLRU,
+		txs:    txsLRU,
+		rcpts:  rcptsLRU,
+	}
+}
+
+func (o *CachingOracle) HeaderByBlockHash(blockHash common.Hash) eth.BlockInfo {
+	block, ok := o.blocks.Get(blockHash)
+	if ok {
+		return block
+	}
+	block = o.oracle.HeaderByBlockHash(blockHash)
+	o.blocks.Add(blockHash, block)
+	return block
+}
+
+func (o *CachingOracle) TransactionsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Transactions) {
+	txs, ok := o.txs.Get(blockHash)
+	if ok {
+		return o.HeaderByBlockHash(blockHash), txs
+	}
+	block, txs := o.oracle.TransactionsByBlockHash(blockHash)
+	o.blocks.Add(blockHash, block)
+	o.txs.Add(blockHash, txs)
+	return block, txs
+}
+
+func (o *CachingOracle) ReceiptsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Receipts) {
+	rcpts, ok := o.rcpts.Get(blockHash)
+	if ok {
+		return o.HeaderByBlockHash(blockHash), rcpts
+	}
+	block, rcpts := o.oracle.ReceiptsByBlockHash(blockHash)
+	o.blocks.Add(blockHash, block)
+	o.rcpts.Add(blockHash, rcpts)
+	return block, rcpts
+}

op-program/client/l1/cache_test.go

+package l1
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/ethereum-optimism/optimism/op-node/testutils"
+	"github.com/stretchr/testify/require"
+)
+
+// Should implement Oracle
+var _ Oracle = (*CachingOracle)(nil)
+
+func TestCachingOracle_HeaderByBlockHash(t *testing.T) {
+	rng := rand.New(rand.NewSource(1))
+	stub := newStubOracle(t)
+	oracle := NewCachingOracle(stub)
+	block := testutils.RandomBlockInfo(rng)
+
+	// Initial call retrieves from the stub
+	stub.blocks[block.Hash()] = block
+	result := oracle.HeaderByBlockHash(block.Hash())
+	require.Equal(t, block, result)
+
+	// Later calls should retrieve from cache
+	delete(stub.blocks, block.Hash())
+	result = oracle.HeaderByBlockHash(block.Hash())
+	require.Equal(t, block, result)
+}
+
+func TestCachingOracle_TransactionsByBlockHash(t *testing.T) {
+	rng := rand.New(rand.NewSource(1))
+	stub := newStubOracle(t)
+	oracle := NewCachingOracle(stub)
+	block, _ := testutils.RandomBlock(rng, 3)
+
+	// Initial call retrieves from the stub
+	stub.blocks[block.Hash()] = block
+	stub.txs[block.Hash()] = block.Transactions()
+	actualBlock, actualTxs := oracle.TransactionsByBlockHash(block.Hash())
+	require.Equal(t, block, actualBlock)
+	require.Equal(t, block.Transactions(), actualTxs)
+
+	// Later calls should retrieve from cache
+	delete(stub.blocks, block.Hash())
+	delete(stub.txs, block.Hash())
+	actualBlock, actualTxs = oracle.TransactionsByBlockHash(block.Hash())
+	require.Equal(t, block, actualBlock)
+	require.Equal(t, block.Transactions(), actualTxs)
+}
+
+func TestCachingOracle_ReceiptsByBlockHash(t *testing.T) {
+	rng := rand.New(rand.NewSource(1))
+	stub := newStubOracle(t)
+	oracle := NewCachingOracle(stub)
+	block, rcpts := testutils.RandomBlock(rng, 3)
+
+	// Initial call retrieves from the stub
+	stub.blocks[block.Hash()] = block
+	stub.rcpts[block.Hash()] = rcpts
+	actualBlock, actualRcpts := oracle.ReceiptsByBlockHash(block.Hash())
+	require.Equal(t, block, actualBlock)
+	require.EqualValues(t, rcpts, actualRcpts)
+
+	// Later calls should retrieve from cache
+	delete(stub.blocks, block.Hash())
+	delete(stub.rcpts, block.Hash())
+	actualBlock, actualRcpts = oracle.ReceiptsByBlockHash(block.Hash())
+	require.Equal(t, block, actualBlock)
+	require.EqualValues(t, rcpts, actualRcpts)
+}

op-program/client/l1/client.go

+package l1
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+)
+
+var (
+	ErrNotFound     = ethereum.NotFound
+	ErrUnknownLabel = errors.New("unknown label")
+)
+
+type OracleL1Client struct {
+	oracle Oracle
+	head   eth.L1BlockRef
+}
+
+func NewOracleL1Client(logger log.Logger, oracle Oracle, l1Head common.Hash) *OracleL1Client {
+	head := eth.InfoToL1BlockRef(oracle.HeaderByBlockHash(l1Head))
+	logger.Info("L1 head loaded", "hash", head.Hash, "number", head.Number)
+	return &OracleL1Client{
+		oracle: oracle,
+		head:   head,
+	}
+}
+
+func (o *OracleL1Client) L1BlockRefByLabel(ctx context.Context, label eth.BlockLabel) (eth.L1BlockRef, error) {
+	if label != eth.Unsafe && label != eth.Safe && label != eth.Finalized {
+		return eth.L1BlockRef{}, fmt.Errorf("%w: %s", ErrUnknownLabel, label)
+	}
+	// The L1 head is pre-agreed and unchanging so it can be used for all of unsafe, safe and finalized
+	return o.head, nil
+}
+
+func (o *OracleL1Client) L1BlockRefByNumber(ctx context.Context, number uint64) (eth.L1BlockRef, error) {
+	if number > o.head.Number {
+		return eth.L1BlockRef{}, fmt.Errorf("%w: block number %d", ErrNotFound, number)
+	}
+	block := o.head
+	for block.Number > number {
+		block = eth.InfoToL1BlockRef(o.oracle.HeaderByBlockHash(block.ParentHash))
+	}
+	return block, nil
+}
+
+func (o *OracleL1Client) L1BlockRefByHash(ctx context.Context, hash common.Hash) (eth.L1BlockRef, error) {
+	return eth.InfoToL1BlockRef(o.oracle.HeaderByBlockHash(hash)), nil
+}
+
+func (o *OracleL1Client) InfoByHash(ctx context.Context, hash common.Hash) (eth.BlockInfo, error) {
+	return o.oracle.HeaderByBlockHash(hash), nil
+}
+
+func (o *OracleL1Client) FetchReceipts(ctx context.Context, blockHash common.Hash) (eth.BlockInfo, types.Receipts, error) {
+	info, rcpts := o.oracle.ReceiptsByBlockHash(blockHash)
+	return info, rcpts, nil
+}
+
+func (o *OracleL1Client) InfoAndTxsByHash(ctx context.Context, hash common.Hash) (eth.BlockInfo, types.Transactions, error) {
+	info, txs := o.oracle.TransactionsByBlockHash(hash)
+	return info, txs, nil
+}

op-program/client/l1/client_test.go

+package l1
+
+import (
+	"context"
+	"math/big"
+	"testing"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
+	"github.com/ethereum-optimism/optimism/op-node/sources"
+	"github.com/ethereum-optimism/optimism/op-node/testlog"
+	"github.com/ethereum-optimism/optimism/op-node/testutils"
+	"github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/stretchr/testify/require"
+)
+
+var _ derive.L1Fetcher = (*OracleL1Client)(nil)
+
+var head = blockNum(1000)
+
+func TestInfoByHash(t *testing.T) {
+	client, oracle := newClient(t)
+	hash := common.HexToHash("0xAABBCC")
+	expected := &sources.HeaderInfo{}
+	oracle.blocks[hash] = expected
+
+	info, err := client.InfoByHash(context.Background(), hash)
+	require.NoError(t, err)
+	require.Equal(t, expected, info)
+}
+
+func TestL1BlockRefByHash(t *testing.T) {
+	client, oracle := newClient(t)
+	hash := common.HexToHash("0xAABBCC")
+	header := &sources.HeaderInfo{}
+	oracle.blocks[hash] = header
+	expected := eth.InfoToL1BlockRef(header)
+
+	ref, err := client.L1BlockRefByHash(context.Background(), hash)
+	require.NoError(t, err)
+	require.Equal(t, expected, ref)
+}
+
+func TestFetchReceipts(t *testing.T) {
+	client, oracle := newClient(t)
+	hash := common.HexToHash("0xAABBCC")
+	expectedInfo := &sources.HeaderInfo{}
+	expectedReceipts := types.Receipts{
+		&types.Receipt{},
+	}
+	oracle.blocks[hash] = expectedInfo
+	oracle.rcpts[hash] = expectedReceipts
+
+	info, rcpts, err := client.FetchReceipts(context.Background(), hash)
+	require.NoError(t, err)
+	require.Equal(t, expectedInfo, info)
+	require.Equal(t, expectedReceipts, rcpts)
+}
+
+func TestInfoAndTxsByHash(t *testing.T) {
+	client, oracle := newClient(t)
+	hash := common.HexToHash("0xAABBCC")
+	expectedInfo := &sources.HeaderInfo{}
+	expectedTxs := types.Transactions{
+		&types.Transaction{},
+	}
+	oracle.blocks[hash] = expectedInfo
+	oracle.txs[hash] = expectedTxs
+
+	info, txs, err := client.InfoAndTxsByHash(context.Background(), hash)
+	require.NoError(t, err)
+	require.Equal(t, expectedInfo, info)
+	require.Equal(t, expectedTxs, txs)
+}
+
+func TestL1BlockRefByLabel(t *testing.T) {
+	t.Run("Unsafe", func(t *testing.T) {
+		client, _ := newClient(t)
+		ref, err := client.L1BlockRefByLabel(context.Background(), eth.Unsafe)
+		require.NoError(t, err)
+		require.Equal(t, eth.InfoToL1BlockRef(head), ref)
+	})
+	t.Run("Safe", func(t *testing.T) {
+		client, _ := newClient(t)
+		ref, err := client.L1BlockRefByLabel(context.Background(), eth.Safe)
+		require.NoError(t, err)
+		require.Equal(t, eth.InfoToL1BlockRef(head), ref)
+	})
+	t.Run("Finalized", func(t *testing.T) {
+		client, _ := newClient(t)
+		ref, err := client.L1BlockRefByLabel(context.Background(), eth.Finalized)
+		require.NoError(t, err)
+		require.Equal(t, eth.InfoToL1BlockRef(head), ref)
+	})
+	t.Run("UnknownLabel", func(t *testing.T) {
+		client, _ := newClient(t)
+		ref, err := client.L1BlockRefByLabel(context.Background(), eth.BlockLabel("unknown"))
+		require.ErrorIs(t, err, ErrUnknownLabel)
+		require.Equal(t, eth.L1BlockRef{}, ref)
+	})
+}
+
+func TestL1BlockRefByNumber(t *testing.T) {
+	t.Run("Head", func(t *testing.T) {
+		client, _ := newClient(t)
+		ref, err := client.L1BlockRefByNumber(context.Background(), head.NumberU64())
+		require.NoError(t, err)
+		require.Equal(t, eth.InfoToL1BlockRef(head), ref)
+	})
+	t.Run("AfterHead", func(t *testing.T) {
+		client, _ := newClient(t)
+		ref, err := client.L1BlockRefByNumber(context.Background(), head.NumberU64()+1)
+		// Must be ethereum.NotFound error so the derivation pipeline knows it has gone past the chain head
+		require.ErrorIs(t, err, ethereum.NotFound)
+		require.Equal(t, eth.L1BlockRef{}, ref)
+	})
+	t.Run("ParentOfHead", func(t *testing.T) {
+		client, oracle := newClient(t)
+		parent := blockNum(head.NumberU64() - 1)
+		oracle.blocks[parent.Hash()] = parent
+
+		ref, err := client.L1BlockRefByNumber(context.Background(), parent.NumberU64())
+		require.NoError(t, err)
+		require.Equal(t, eth.InfoToL1BlockRef(parent), ref)
+	})
+	t.Run("AncestorOfHead", func(t *testing.T) {
+		client, oracle := newClient(t)
+		block := head
+		blocks := []eth.BlockInfo{block}
+		for i := 0; i < 10; i++ {
+			block = blockNum(block.NumberU64() - 1)
+			oracle.blocks[block.Hash()] = block
+			blocks = append(blocks, block)
+		}
+
+		for _, block := range blocks {
+			ref, err := client.L1BlockRefByNumber(context.Background(), block.NumberU64())
+			require.NoError(t, err)
+			require.Equal(t, eth.InfoToL1BlockRef(block), ref)
+		}
+	})
+}
+
+func newClient(t *testing.T) (*OracleL1Client, *stubOracle) {
+	stub := newStubOracle(t)
+	stub.blocks[head.Hash()] = head
+	client := NewOracleL1Client(testlog.Logger(t, log.LvlDebug), stub, head.Hash())
+	return client, stub
+}
+
+func blockNum(num uint64) eth.BlockInfo {
+	parentNum := num - 1
+	return &testutils.MockBlockInfo{
+		InfoHash:        common.BytesToHash(big.NewInt(int64(num)).Bytes()),
+		InfoParentHash:  common.BytesToHash(big.NewInt(int64(parentNum)).Bytes()),
+		InfoCoinbase:    common.Address{},
+		InfoRoot:        common.Hash{},
+		InfoNum:         num,
+		InfoTime:        num * 2,
+		InfoMixDigest:   [32]byte{},
+		InfoBaseFee:     nil,
+		InfoReceiptRoot: common.Hash{},
+		InfoGasUsed:     0,
+	}
+}

op-program/client/l1/hints.go

+package l1
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+
+	"github.com/ethereum-optimism/optimism/op-program/preimage"
+)
+
+type BlockHeaderHint common.Hash
+
+var _ preimage.Hint = BlockHeaderHint{}
+
+func (l BlockHeaderHint) Hint() string {
+	return "l1-block-header " + (common.Hash)(l).String()
+}
+
+type TransactionsHint common.Hash
+
+var _ preimage.Hint = TransactionsHint{}
+
+func (l TransactionsHint) Hint() string {
+	return "l1-transactions " + (common.Hash)(l).String()
+}
+
+type ReceiptsHint common.Hash
+
+var _ preimage.Hint = ReceiptsHint{}
+
+func (l ReceiptsHint) Hint() string {
+	return "l1-receipts " + (common.Hash)(l).String()
+}

op-program/client/l1/oracle.go

+package l1
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/rlp"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum-optimism/optimism/op-program/client/mpt"
+	"github.com/ethereum-optimism/optimism/op-program/preimage"
+)
+
+type Oracle interface {
+	// HeaderByBlockHash retrieves the block header with the given hash.
+	HeaderByBlockHash(blockHash common.Hash) eth.BlockInfo
+
+	// TransactionsByBlockHash retrieves the transactions from the block with the given hash.
+	TransactionsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Transactions)
+
+	// ReceiptsByBlockHash retrieves the receipts from the block with the given hash.
+	ReceiptsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Receipts)
+}
+
+// PreimageOracle implements Oracle using by interfacing with the pure preimage.Oracle
+// to fetch pre-images to decode into the requested data.
+type PreimageOracle struct {
+	oracle preimage.Oracle
+	hint   preimage.Hinter
+}
+
+var _ Oracle = (*PreimageOracle)(nil)
+
+func NewPreimageOracle(raw preimage.Oracle, hint preimage.Hinter) *PreimageOracle {
+	return &PreimageOracle{
+		oracle: raw,
+		hint:   hint,
+	}
+}
+
+func (p *PreimageOracle) headerByBlockHash(blockHash common.Hash) *types.Header {
+	p.hint.Hint(BlockHeaderHint(blockHash))
+	headerRlp := p.oracle.Get(preimage.Keccak256Key(blockHash))
+	var header types.Header
+	if err := rlp.DecodeBytes(headerRlp, &header); err != nil {
+		panic(fmt.Errorf("invalid block header %s: %w", blockHash, err))
+	}
+	return &header
+}
+
+func (p *PreimageOracle) HeaderByBlockHash(blockHash common.Hash) eth.BlockInfo {
+	return eth.HeaderBlockInfo(p.headerByBlockHash(blockHash))
+}
+
+func (p *PreimageOracle) TransactionsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Transactions) {
+	header := p.headerByBlockHash(blockHash)
+	p.hint.Hint(TransactionsHint(blockHash))
+
+	opaqueTxs := mpt.ReadTrie(header.TxHash, func(key common.Hash) []byte {
+		return p.oracle.Get(preimage.Keccak256Key(key))
+	})
+
+	txs, err := eth.DecodeTransactions(opaqueTxs)
+	if err != nil {
+		panic(fmt.Errorf("failed to decode list of txs: %w", err))
+	}
+
+	return eth.HeaderBlockInfo(header), txs
+}
+
+func (p *PreimageOracle) ReceiptsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Receipts) {
+	info, txs := p.TransactionsByBlockHash(blockHash)
+
+	p.hint.Hint(ReceiptsHint(blockHash))
+
+	opaqueReceipts := mpt.ReadTrie(info.ReceiptHash(), func(key common.Hash) []byte {
+		return p.oracle.Get(preimage.Keccak256Key(key))
+	})
+
+	txHashes := eth.TransactionsToHashes(txs)
+	receipts, err := eth.DecodeRawReceipts(eth.ToBlockID(info), opaqueReceipts, txHashes)
+	if err != nil {
+		panic(fmt.Errorf("bad receipts data for block %s: %w", blockHash, err))
+	}
+
+	return info, receipts
+}

op-program/client/l1/oracle_test.go

+package l1
+
+import (
+	"encoding/json"
+	"fmt"
+	"math/rand"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum-optimism/optimism/op-node/testutils"
+	"github.com/ethereum-optimism/optimism/op-program/client/mpt"
+	"github.com/ethereum-optimism/optimism/op-program/preimage"
+)
+
+// testBlock tests that the given block with receipts can be passed through the preimage oracle.
+func testBlock(t *testing.T, block *types.Block, receipts []*types.Receipt) {
+	// Prepare the pre-images
+	preimages := make(map[common.Hash][]byte)
+
+	hdrBytes, err := rlp.EncodeToBytes(block.Header())
+	require.NoError(t, err)
+	preimages[preimage.Keccak256Key(block.Hash()).PreimageKey()] = hdrBytes
+
+	opaqueTxs, err := eth.EncodeTransactions(block.Transactions())
+	require.NoError(t, err)
+	_, txsNodes := mpt.WriteTrie(opaqueTxs)
+	for _, p := range txsNodes {
+		preimages[preimage.Keccak256Key(crypto.Keccak256Hash(p)).PreimageKey()] = p
+	}
+
+	opaqueReceipts, err := eth.EncodeReceipts(receipts)
+	require.NoError(t, err)
+	_, receiptNodes := mpt.WriteTrie(opaqueReceipts)
+	for _, p := range receiptNodes {
+		preimages[preimage.Keccak256Key(crypto.Keccak256Hash(p)).PreimageKey()] = p
+	}
+
+	// Prepare a raw mock pre-image oracle that will serve the pre-image data and handle hints
+	var hints mock.Mock
+	po := &PreimageOracle{
+		oracle: 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) {
+			hints.MethodCalled("hint", v.Hint())
+		}),
+	}
+
+	// Check if block-headers work
+	hints.On("hint", BlockHeaderHint(block.Hash()).Hint()).Once().Return()
+	gotHeader := po.HeaderByBlockHash(block.Hash())
+	hints.AssertExpectations(t)
+
+	got, err := json.MarshalIndent(gotHeader, "  ", "  ")
+	require.NoError(t, err)
+	expected, err := json.MarshalIndent(block.Header(), "  ", "  ")
+	require.NoError(t, err)
+	require.Equal(t, expected, got, "expecting matching headers")
+
+	// Check if blocks with txs work
+	hints.On("hint", BlockHeaderHint(block.Hash()).Hint()).Once().Return()
+	hints.On("hint", TransactionsHint(block.Hash()).Hint()).Once().Return()
+	inf, gotTxs := po.TransactionsByBlockHash(block.Hash())
+	hints.AssertExpectations(t)
+
+	require.Equal(t, inf.Hash(), block.Hash())
+	expectedTxs := block.Transactions()
+	require.Equal(t, len(expectedTxs), len(gotTxs), "expecting equal tx list length")
+	for i, tx := range gotTxs {
+		require.Equalf(t, tx.Hash(), expectedTxs[i].Hash(), "expecting tx %d to match", i)
+	}
+
+	// Check if blocks with receipts work
+	hints.On("hint", BlockHeaderHint(block.Hash()).Hint()).Once().Return()
+	hints.On("hint", TransactionsHint(block.Hash()).Hint()).Once().Return()
+	hints.On("hint", ReceiptsHint(block.Hash()).Hint()).Once().Return()
+	inf, gotReceipts := po.ReceiptsByBlockHash(block.Hash())
+	hints.AssertExpectations(t)
+
+	require.Equal(t, inf.Hash(), block.Hash())
+	require.Equal(t, len(receipts), len(gotReceipts), "expecting equal tx list length")
+	for i, r := range gotReceipts {
+		require.Equalf(t, r.TxHash, expectedTxs[i].Hash(), "expecting receipt to match tx %d", i)
+	}
+}
+
+func TestPreimageOracleBlockByHash(t *testing.T) {
+	rng := rand.New(rand.NewSource(123))
+
+	for i := 0; i < 10; i++ {
+		block, receipts := testutils.RandomBlock(rng, 10)
+		t.Run(fmt.Sprintf("block_%d", i), func(t *testing.T) {
+			testBlock(t, block, receipts)
+		})
+	}
+}

op-program/client/l1/stub_oracle_test.go

+package l1
+
+import (
+	"testing"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+type stubOracle struct {
+	t *testing.T
+
+	// blocks maps block hash to eth.BlockInfo
+	blocks map[common.Hash]eth.BlockInfo
+
+	// txs maps block hash to transactions
+	txs map[common.Hash]types.Transactions
+
+	// rcpts maps Block hash to receipts
+	rcpts map[common.Hash]types.Receipts
+}
+
+func newStubOracle(t *testing.T) *stubOracle {
+	return &stubOracle{
+		t:      t,
+		blocks: make(map[common.Hash]eth.BlockInfo),
+		txs:    make(map[common.Hash]types.Transactions),
+		rcpts:  make(map[common.Hash]types.Receipts),
+	}
+}
+func (o stubOracle) HeaderByBlockHash(blockHash common.Hash) eth.BlockInfo {
+	info, ok := o.blocks[blockHash]
+	if !ok {
+		o.t.Fatalf("unknown block %s", blockHash)
+	}
+	return info
+}
+
+func (o stubOracle) TransactionsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Transactions) {
+	txs, ok := o.txs[blockHash]
+	if !ok {
+		o.t.Fatalf("unknown txs %s", blockHash)
+	}
+	return o.HeaderByBlockHash(blockHash), txs
+}
+
+func (o stubOracle) ReceiptsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Receipts) {
+	rcpts, ok := o.rcpts[blockHash]
+	if !ok {
+		o.t.Fatalf("unknown rcpts %s", blockHash)
+	}
+	return o.HeaderByBlockHash(blockHash), rcpts
+}

op-program/client/l2/cache.go

+package l2
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/hashicorp/golang-lru/v2/simplelru"
+)
+
+const blockCacheSize = 2_000
+const nodeCacheSize = 100_000
+const codeCacheSize = 10_000
+
+type CachingOracle struct {
+	oracle Oracle
+	blocks *simplelru.LRU[common.Hash, *types.Block]
+	nodes  *simplelru.LRU[common.Hash, []byte]
+	codes  *simplelru.LRU[common.Hash, []byte]
+}
+
+func NewCachingOracle(oracle Oracle) *CachingOracle {
+	blockLRU, _ := simplelru.NewLRU[common.Hash, *types.Block](blockCacheSize, nil)
+	nodeLRU, _ := simplelru.NewLRU[common.Hash, []byte](nodeCacheSize, nil)
+	codeLRU, _ := simplelru.NewLRU[common.Hash, []byte](codeCacheSize, nil)
+	return &CachingOracle{
+		oracle: oracle,
+		blocks: blockLRU,
+		nodes:  nodeLRU,
+		codes:  codeLRU,
+	}
+}
+
+func (o *CachingOracle) NodeByHash(nodeHash common.Hash) []byte {
+	node, ok := o.nodes.Get(nodeHash)
+	if ok {
+		return node
+	}
+	node = o.oracle.NodeByHash(nodeHash)
+	o.nodes.Add(nodeHash, node)
+	return node
+}
+
+func (o *CachingOracle) CodeByHash(codeHash common.Hash) []byte {
+	code, ok := o.codes.Get(codeHash)
+	if ok {
+		return code
+	}
+	code = o.oracle.CodeByHash(codeHash)
+	o.codes.Add(codeHash, code)
+	return code
+}
+
+func (o *CachingOracle) BlockByHash(blockHash common.Hash) *types.Block {
+	block, ok := o.blocks.Get(blockHash)
+	if ok {
+		return block
+	}
+	block = o.oracle.BlockByHash(blockHash)
+	o.blocks.Add(blockHash, block)
+	return block
+}

op-program/client/l2/cache_test.go

+package l2
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/ethereum-optimism/optimism/op-node/testutils"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/stretchr/testify/require"
+)
+
+// Should be an Oracle implementation
+var _ Oracle = (*CachingOracle)(nil)
+
+func TestBlockByHash(t *testing.T) {
+	stub, _ := newStubOracle(t)
+	oracle := NewCachingOracle(stub)
+
+	rng := rand.New(rand.NewSource(1))
+	block, _ := testutils.RandomBlock(rng, 1)
+
+	// Initial call retrieves from the stub
+	stub.blocks[block.Hash()] = block
+	actual := oracle.BlockByHash(block.Hash())
+	require.Equal(t, block, actual)
+
+	// Later calls should retrieve from cache
+	delete(stub.blocks, block.Hash())
+	actual = oracle.BlockByHash(block.Hash())
+	require.Equal(t, block, actual)
+}
+
+func TestNodeByHash(t *testing.T) {
+	stub, stateStub := newStubOracle(t)
+	oracle := NewCachingOracle(stub)
+
+	node := []byte{12, 3, 4}
+	hash := common.Hash{0xaa}
+
+	// Initial call retrieves from the stub
+	stateStub.data[hash] = node
+	actual := oracle.NodeByHash(hash)
+	require.Equal(t, node, actual)
+
+	// Later calls should retrieve from cache
+	delete(stateStub.data, hash)
+	actual = oracle.NodeByHash(hash)
+	require.Equal(t, node, actual)
+}
+
+func TestCodeByHash(t *testing.T) {
+	stub, stateStub := newStubOracle(t)
+	oracle := NewCachingOracle(stub)
+
+	node := []byte{12, 3, 4}
+	hash := common.Hash{0xaa}
+
+	// Initial call retrieves from the stub
+	stateStub.code[hash] = node
+	actual := oracle.CodeByHash(hash)
+	require.Equal(t, node, actual)
+
+	// Later calls should retrieve from cache
+	delete(stateStub.code, hash)
+	actual = oracle.CodeByHash(hash)
+	require.Equal(t, node, actual)
+}

op-program/client/l2/db.go

@@ -40,12 +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))
+		return o.oracle.CodeByHash(*(*[common.HashLength]byte)(key)), nil
 	}
 	if len(key) != common.HashLength {
 		return nil, ErrInvalidKeyLength
 	}
-	return o.oracle.NodeByHash(*(*[common.HashLength]byte)(key))
+	return o.oracle.NodeByHash(*(*[common.HashLength]byte)(key)), nil
 }
 
 func (o *OracleKeyValueStore) NewBatch() ethdb.Batch {

op-program/client/l2/db_test.go

 package l2
 
 import (
-	"fmt"
 	"math/big"
 	"testing"
 
@@ -27,16 +26,8 @@ var (
 var _ ethdb.KeyValueStore = (*OracleKeyValueStore)(nil)
 
 func TestGet(t *testing.T) {
-	t.Run("UnknownKey", func(t *testing.T) {
-		oracle := newStubStateOracle()
-		db := NewOracleBackedDB(oracle)
-		val, err := db.Get(common.Hash{}.Bytes())
-		require.Error(t, err)
-		require.Nil(t, val)
-	})
-
 	t.Run("IncorrectLengthKey", func(t *testing.T) {
-		oracle := newStubStateOracle()
+		oracle := newStubStateOracle(t)
 		db := NewOracleBackedDB(oracle)
 		val, err := db.Get([]byte{1, 2, 3})
 		require.ErrorIs(t, err, ErrInvalidKeyLength)
@@ -44,7 +35,7 @@ func TestGet(t *testing.T) {
 	})
 
 	t.Run("KeyWithCodePrefix", func(t *testing.T) {
-		oracle := newStubStateOracle()
+		oracle := newStubStateOracle(t)
 		db := NewOracleBackedDB(oracle)
 		key := common.HexToHash("0x12345678")
 		prefixedKey := append(rawdb.CodePrefix, key.Bytes()...)
@@ -58,7 +49,7 @@ func TestGet(t *testing.T) {
 	})
 
 	t.Run("NormalKeyThatHappensToStartWithCodePrefix", func(t *testing.T) {
-		oracle := newStubStateOracle()
+		oracle := newStubStateOracle(t)
 		db := NewOracleBackedDB(oracle)
 		key := make([]byte, common.HashLength)
 		copy(rawdb.CodePrefix, key)
@@ -74,7 +65,7 @@ func TestGet(t *testing.T) {
 	t.Run("KnownKey", func(t *testing.T) {
 		key := common.HexToHash("0xAA4488")
 		expected := []byte{2, 6, 3, 8}
-		oracle := newStubStateOracle()
+		oracle := newStubStateOracle(t)
 		oracle.data[key] = expected
 		db := NewOracleBackedDB(oracle)
 		val, err := db.Get(key.Bytes())
@@ -85,7 +76,7 @@ func TestGet(t *testing.T) {
 
 func TestPut(t *testing.T) {
 	t.Run("NewKey", func(t *testing.T) {
-		oracle := newStubStateOracle()
+		oracle := newStubStateOracle(t)
 		db := NewOracleBackedDB(oracle)
 		key := common.HexToHash("0xAA4488")
 		value := []byte{2, 6, 3, 8}
@@ -97,7 +88,7 @@ func TestPut(t *testing.T) {
 		require.Equal(t, value, actual)
 	})
 	t.Run("ReplaceKey", func(t *testing.T) {
-		oracle := newStubStateOracle()
+		oracle := newStubStateOracle(t)
 		db := NewOracleBackedDB(oracle)
 		key := common.HexToHash("0xAA4488")
 		value1 := []byte{2, 6, 3, 8}
@@ -119,6 +110,7 @@ func TestSupportsStateDBOperations(t *testing.T) {
 	genesisBlock := l2Genesis.MustCommit(realDb)
 
 	loader := &kvStateOracle{
+		t:      t,
 		source: realDb,
 	}
 	assertStateDataAvailable(t, NewOracleBackedDB(loader), l2Genesis, genesisBlock)
@@ -126,7 +118,7 @@ func TestSupportsStateDBOperations(t *testing.T) {
 
 func TestUpdateState(t *testing.T) {
 	l2Genesis := createGenesis()
-	oracle := newStubStateOracle()
+	oracle := newStubStateOracle(t)
 	db := rawdb.NewDatabase(NewOracleBackedDB(oracle))
 
 	genesisBlock := l2Genesis.MustCommit(db)
@@ -202,44 +194,3 @@ func assertStateDataAvailable(t *testing.T, db ethdb.KeyValueStore, l2Genesis *c
 	require.Nil(t, statedb.GetCode(unknownAccount), "unset account code")
 	require.Equal(t, common.Hash{}, statedb.GetCodeHash(unknownAccount), "unset account code hash")
 }
-
-func newStubStateOracle() *stubStateOracle {
-	return &stubStateOracle{
-		data: make(map[common.Hash][]byte),
-		code: make(map[common.Hash][]byte),
-	}
-}
-
-type stubStateOracle struct {
-	data map[common.Hash][]byte
-	code map[common.Hash][]byte
-}
-
-func (o *stubStateOracle) NodeByHash(nodeHash common.Hash) ([]byte, error) {
-	data, ok := o.data[nodeHash]
-	if !ok {
-		return nil, fmt.Errorf("no value for node %v", nodeHash)
-	}
-	return data, nil
-}
-
-func (o *stubStateOracle) CodeByHash(hash common.Hash) ([]byte, error) {
-	data, ok := o.code[hash]
-	if !ok {
-		return nil, fmt.Errorf("no value for code %v", hash)
-	}
-	return data, nil
-}
-
-// kvStateOracle loads data from a source ethdb.KeyValueStore
-type kvStateOracle struct {
-	source ethdb.KeyValueStore
-}
-
-func (o *kvStateOracle) NodeByHash(nodeHash common.Hash) ([]byte, error) {
-	return o.source.Get(nodeHash.Bytes())
-}
-
-func (o *kvStateOracle) CodeByHash(hash common.Hash) ([]byte, error) {
-	return rawdb.ReadCode(o.source, hash), nil
-}

op-program/client/l2/engine.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/ethereum-optimism/optimism/op-bindings/predeploys"
 	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
 	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
@@ -33,19 +34,32 @@ func NewOracleEngine(rollupCfg *rollup.Config, logger log.Logger, backend engine
 	}
 }
 
-func (o OracleEngine) GetPayload(ctx context.Context, payloadId eth.PayloadID) (*eth.ExecutionPayload, error) {
+func (o *OracleEngine) L2OutputRoot() (eth.Bytes32, error) {
+	outBlock := o.backend.CurrentHeader()
+	stateDB, err := o.backend.StateAt(outBlock.Root)
+	if err != nil {
+		return eth.Bytes32{}, fmt.Errorf("failed to open L2 state db at block %s: %w", outBlock.Hash(), err)
+	}
+	withdrawalsTrie, err := stateDB.StorageTrie(predeploys.L2ToL1MessagePasserAddr)
+	if err != nil {
+		return eth.Bytes32{}, fmt.Errorf("withdrawals trie unavailable at block %v: %w", outBlock.Hash(), err)
+	}
+	return rollup.ComputeL2OutputRootV0(eth.HeaderBlockInfo(outBlock), withdrawalsTrie.Hash())
+}
+
+func (o *OracleEngine) GetPayload(ctx context.Context, payloadId eth.PayloadID) (*eth.ExecutionPayload, error) {
 	return o.api.GetPayloadV1(ctx, payloadId)
 }
 
-func (o OracleEngine) ForkchoiceUpdate(ctx context.Context, state *eth.ForkchoiceState, attr *eth.PayloadAttributes) (*eth.ForkchoiceUpdatedResult, error) {
+func (o *OracleEngine) ForkchoiceUpdate(ctx context.Context, state *eth.ForkchoiceState, attr *eth.PayloadAttributes) (*eth.ForkchoiceUpdatedResult, error) {
 	return o.api.ForkchoiceUpdatedV1(ctx, state, attr)
 }
 
-func (o OracleEngine) NewPayload(ctx context.Context, payload *eth.ExecutionPayload) (*eth.PayloadStatusV1, error) {
+func (o *OracleEngine) NewPayload(ctx context.Context, payload *eth.ExecutionPayload) (*eth.PayloadStatusV1, error) {
 	return o.api.NewPayloadV1(ctx, payload)
 }
 
-func (o OracleEngine) PayloadByHash(ctx context.Context, hash common.Hash) (*eth.ExecutionPayload, error) {
+func (o *OracleEngine) PayloadByHash(ctx context.Context, hash common.Hash) (*eth.ExecutionPayload, error) {
 	block := o.backend.GetBlockByHash(hash)
 	if block == nil {
 		return nil, ErrNotFound
@@ -53,7 +67,7 @@ func (o OracleEngine) PayloadByHash(ctx context.Context, hash common.Hash) (*eth
 	return eth.BlockAsPayload(block)
 }
 
-func (o OracleEngine) PayloadByNumber(ctx context.Context, n uint64) (*eth.ExecutionPayload, error) {
+func (o *OracleEngine) PayloadByNumber(ctx context.Context, n uint64) (*eth.ExecutionPayload, error) {
 	hash := o.backend.GetCanonicalHash(n)
 	if hash == (common.Hash{}) {
 		return nil, ErrNotFound
@@ -61,7 +75,7 @@ func (o OracleEngine) PayloadByNumber(ctx context.Context, n uint64) (*eth.Execu
 	return o.PayloadByHash(ctx, hash)
 }
 
-func (o OracleEngine) L2BlockRefByLabel(ctx context.Context, label eth.BlockLabel) (eth.L2BlockRef, error) {
+func (o *OracleEngine) L2BlockRefByLabel(ctx context.Context, label eth.BlockLabel) (eth.L2BlockRef, error) {
 	var header *types.Header
 	switch label {
 	case eth.Unsafe:
@@ -83,7 +97,7 @@ func (o OracleEngine) L2BlockRefByLabel(ctx context.Context, label eth.BlockLabe
 	return derive.L2BlockToBlockRef(block, &o.rollupCfg.Genesis)
 }
 
-func (o OracleEngine) L2BlockRefByHash(ctx context.Context, l2Hash common.Hash) (eth.L2BlockRef, error) {
+func (o *OracleEngine) L2BlockRefByHash(ctx context.Context, l2Hash common.Hash) (eth.L2BlockRef, error) {
 	block := o.backend.GetBlockByHash(l2Hash)
 	if block == nil {
 		return eth.L2BlockRef{}, ErrNotFound
@@ -91,7 +105,7 @@ func (o OracleEngine) L2BlockRefByHash(ctx context.Context, l2Hash common.Hash)
 	return derive.L2BlockToBlockRef(block, &o.rollupCfg.Genesis)
 }
 
-func (o OracleEngine) SystemConfigByL2Hash(ctx context.Context, hash common.Hash) (eth.SystemConfig, error) {
+func (o *OracleEngine) SystemConfigByL2Hash(ctx context.Context, hash common.Hash) (eth.SystemConfig, error) {
 	payload, err := o.PayloadByHash(ctx, hash)
 	if err != nil {
 		return eth.SystemConfig{}, err

op-program/client/l2/engine_backend.go

@@ -22,6 +22,7 @@ type OracleBackedL2Chain struct {
 	oracle     Oracle
 	chainCfg   *params.ChainConfig
 	engine     consensus.Engine
+	oracleHead *types.Header
 	head       *types.Header
 	safe       *types.Header
 	finalized  *types.Header
@@ -35,10 +36,8 @@ type OracleBackedL2Chain struct {
 var _ engineapi.EngineBackend = (*OracleBackedL2Chain)(nil)
 
 func NewOracleBackedL2Chain(logger log.Logger, oracle Oracle, chainCfg *params.ChainConfig, l2Head common.Hash) (*OracleBackedL2Chain, error) {
-	head, err := oracle.BlockByHash(l2Head)
-	if err != nil {
-		return nil, fmt.Errorf("loading l2 head: %w", err)
-	}
+	head := oracle.BlockByHash(l2Head)
+	logger.Info("Loaded L2 head", "hash", head.Hash(), "number", head.Number())
 	return &OracleBackedL2Chain{
 		log:      logger,
 		oracle:   oracle,
@@ -49,6 +48,7 @@ func NewOracleBackedL2Chain(logger log.Logger, oracle Oracle, chainCfg *params.C
 		head:       head.Header(),
 		safe:       head.Header(),
 		finalized:  head.Header(),
+		oracleHead: head.Header(),
 		blocks:     make(map[common.Hash]*types.Block),
 		db:         NewOracleBackedDB(oracle),
 	}, nil
@@ -84,11 +84,7 @@ func (o *OracleBackedL2Chain) CurrentFinalBlock() *types.Header {
 }
 
 func (o *OracleBackedL2Chain) GetHeaderByHash(hash common.Hash) *types.Header {
-	block := o.GetBlockByHash(hash)
-	if block == nil {
-		return nil
-	}
-	return block.Header()
+	return o.GetBlockByHash(hash).Header()
 }
 
 func (o *OracleBackedL2Chain) GetBlockByHash(hash common.Hash) *types.Block {
@@ -98,18 +94,18 @@ func (o *OracleBackedL2Chain) GetBlockByHash(hash common.Hash) *types.Block {
 		return block
 	}
 	// Retrieve from the oracle
-	block, err := o.oracle.BlockByHash(hash)
-	if err != nil {
-		handleError(err)
-	}
-	if block == nil {
-		return nil
-	}
-	return block
+	return o.oracle.BlockByHash(hash)
 }
 
 func (o *OracleBackedL2Chain) GetBlock(hash common.Hash, number uint64) *types.Block {
-	block := o.GetBlockByHash(hash)
+	var block *types.Block
+	if o.oracleHead.Number.Uint64() < number {
+		// For blocks above the chain head, only consider newly built blocks
+		// Avoids requesting an unknown block from the oracle which would panic.
+		block = o.blocks[hash]
+	} else {
+		block = o.GetBlockByHash(hash)
+	}
 	if block == nil {
 		return nil
 	}
@@ -121,9 +117,6 @@ func (o *OracleBackedL2Chain) GetBlock(hash common.Hash, number uint64) *types.B
 
 func (o *OracleBackedL2Chain) GetHeader(hash common.Hash, u uint64) *types.Header {
 	block := o.GetBlock(hash, u)
-	if block == nil {
-		return nil
-	}
 	return block.Header()
 }
 
@@ -194,7 +187,3 @@ func (o *OracleBackedL2Chain) SetFinalized(header *types.Header) {
 func (o *OracleBackedL2Chain) SetSafe(header *types.Header) {
 	o.safe = header
 }
-
-func handleError(err error) {
-	panic(err)
-}

op-program/client/l2/engine_backend_test.go

@@ -9,12 +9,12 @@ import (
 	"github.com/ethereum-optimism/optimism/op-program/client/l2/engineapi"
 	"github.com/ethereum-optimism/optimism/op-program/client/l2/engineapi/test"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/consensus/beacon"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
-	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/stretchr/testify/require"
@@ -42,17 +42,6 @@ func TestGetBlocks(t *testing.T) {
 	}
 }
 
-func TestUnknownBlock(t *testing.T) {
-	_, chain := setupOracleBackedChain(t, 1)
-	hash := common.HexToHash("0x556677881122")
-	blockNumber := uint64(1)
-	require.Nil(t, chain.GetBlockByHash(hash))
-	require.Nil(t, chain.GetHeaderByHash(hash))
-	require.Nil(t, chain.GetBlock(hash, blockNumber))
-	require.Nil(t, chain.GetHeader(hash, blockNumber))
-	require.False(t, chain.HasBlockAndState(hash, blockNumber))
-}
-
 func TestCanonicalHashNotFoundPastChainHead(t *testing.T) {
 	blocks, chain := setupOracleBackedChainWithLowerHead(t, 5, 3)
 
@@ -69,7 +58,7 @@ func TestCanonicalHashNotFoundPastChainHead(t *testing.T) {
 func TestAppendToChain(t *testing.T) {
 	blocks, chain := setupOracleBackedChainWithLowerHead(t, 4, 3)
 	newBlock := blocks[4]
-	require.Nil(t, chain.GetBlockByHash(newBlock.Hash()), "block unknown before being added")
+	require.Nil(t, chain.GetBlock(newBlock.Hash(), newBlock.NumberU64()), "block unknown before being added")
 
 	require.NoError(t, chain.InsertBlockWithoutSetHead(newBlock))
 	require.Equal(t, blocks[3].Header(), chain.CurrentHeader(), "should not update chain head yet")
@@ -113,8 +102,7 @@ func TestUpdateStateDatabaseWhenImportingBlock(t *testing.T) {
 
 	require.NotEqual(t, blocks[1].Root(), newBlock.Root(), "block should have modified world state")
 
-	_, err = chain.StateAt(newBlock.Root())
-	require.Error(t, err, "state from non-imported block should not be available")
+	require.False(t, chain.HasBlockAndState(newBlock.Root(), newBlock.NumberU64()), "state from non-imported block should not be available")
 
 	err = chain.InsertBlockWithoutSetHead(newBlock)
 	require.NoError(t, err)
@@ -162,6 +150,9 @@ func setupOracle(t *testing.T, blockCount int, headBlockNumber int) (*params.Cha
 		L2BlockTime:            2,
 		FundDevAccounts:        true,
 		L2GenesisBlockGasLimit: 30_000_000,
+		// Arbitrary non-zero difficulty in genesis.
+		// This is slightly weird for a chain starting post-merge but it happens so need to make sure it works
+		L2GenesisBlockDifficulty: (*hexutil.Big)(big.NewInt(100)),
 	}
 	l1Genesis, err := genesis.NewL1Genesis(deployConfig)
 	require.NoError(t, err)
@@ -180,7 +171,7 @@ func setupOracle(t *testing.T, blockCount int, headBlockNumber int) (*params.Cha
 	genesisBlock := l2Genesis.MustCommit(db)
 	blocks, _ := core.GenerateChain(chainCfg, genesisBlock, consensus, db, blockCount, func(i int, gen *core.BlockGen) {})
 	blocks = append([]*types.Block{genesisBlock}, blocks...)
-	oracle := newStubBlockOracle(blocks[:headBlockNumber+1], db)
+	oracle := newStubOracleWithBlocks(t, blocks[:headBlockNumber+1], db)
 	return chainCfg, blocks, oracle
 }
 
@@ -207,28 +198,8 @@ func createBlock(t *testing.T, chain *OracleBackedL2Chain) *types.Block {
 	return blocks[0]
 }
 
-type stubBlockOracle struct {
-	blocks map[common.Hash]*types.Block
-	kvStateOracle
-}
-
-func newStubBlockOracle(chain []*types.Block, db ethdb.Database) *stubBlockOracle {
-	blocks := make(map[common.Hash]*types.Block, len(chain))
-	for _, block := range chain {
-		blocks[block.Hash()] = block
-	}
-	return &stubBlockOracle{
-		blocks:        blocks,
-		kvStateOracle: kvStateOracle{source: db},
-	}
-}
-
-func (o stubBlockOracle) BlockByHash(blockHash common.Hash) (*types.Block, error) {
-	return o.blocks[blockHash], nil
-}
-
 func TestEngineAPITests(t *testing.T) {
-	test.RunEngineAPITests(t, func() engineapi.EngineBackend {
+	test.RunEngineAPITests(t, func(t *testing.T) engineapi.EngineBackend {
 		_, chain := setupOracleBackedChain(t, 0)
 		return chain
 	})

op-program/client/l2/engineapi/l2_engine_api.go

@@ -207,7 +207,7 @@ func (ea *L2EngineAPI) ForkchoiceUpdatedV1(ctx context.Context, state *eth.Forkc
 	// Block is known locally, just sanity check that the beacon client does not
 	// attempt to push us back to before the merge.
 	// Note: Differs from op-geth implementation as pre-merge blocks are never supported here
-	if block.Difficulty().BitLen() > 0 {
+	if block.Difficulty().BitLen() > 0 && block.NumberU64() > 0 {
 		return STATUS_INVALID, errors.New("pre-merge blocks not supported")
 	}
 	valid := func(id *engine.PayloadID) *eth.ForkchoiceUpdatedResult {
@@ -301,7 +301,7 @@ func (ea *L2EngineAPI) NewPayloadV1(ctx context.Context, payload *eth.ExecutionP
 	}
 	// If we already have the block locally, ignore the entire execution and just
 	// return a fake success.
-	if block := ea.backend.GetBlockByHash(payload.BlockHash); block != nil {
+	if block := ea.backend.GetBlock(payload.BlockHash, uint64(payload.BlockNumber)); block != nil {
 		ea.log.Warn("Ignoring already known beacon payload", "number", payload.BlockNumber, "hash", payload.BlockHash, "age", common.PrettyAge(time.Unix(int64(block.Time()), 0)))
 		hash := block.Hash()
 		return &eth.PayloadStatusV1{Status: eth.ExecutionValid, LatestValidHash: &hash}, nil

op-program/client/l2/engineapi/test/l2_engine_api_tests.go

@@ -18,7 +18,7 @@ import (
 var gasLimit = eth.Uint64Quantity(30_000_000)
 var feeRecipient = common.Address{}
 
-func RunEngineAPITests(t *testing.T, createBackend func() engineapi.EngineBackend) {
+func RunEngineAPITests(t *testing.T, createBackend func(t *testing.T) engineapi.EngineBackend) {
 	t.Run("CreateBlock", func(t *testing.T) {
 		api := newTestHelper(t, createBackend)
 
@@ -292,10 +292,10 @@ type testHelper struct {
 	assert  *require.Assertions
 }
 
-func newTestHelper(t *testing.T, createBackend func() engineapi.EngineBackend) *testHelper {
+func newTestHelper(t *testing.T, createBackend func(t *testing.T) engineapi.EngineBackend) *testHelper {
 	logger := testlog.Logger(t, log.LvlDebug)
 	ctx := context.Background()
-	backend := createBackend()
+	backend := createBackend(t)
 	api := engineapi.NewL2EngineAPI(logger, backend)
 	test := &testHelper{
 		t:       t,

op-program/client/l2/hints.go

+package l2
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+
+	"github.com/ethereum-optimism/optimism/op-program/preimage"
+)
+
+type BlockHeaderHint common.Hash
+
+var _ preimage.Hint = BlockHeaderHint{}
+
+func (l BlockHeaderHint) Hint() string {
+	return "l2-block-header " + (common.Hash)(l).String()
+}
+
+type TransactionsHint common.Hash
+
+var _ preimage.Hint = TransactionsHint{}
+
+func (l TransactionsHint) Hint() string {
+	return "l2-transactions " + (common.Hash)(l).String()
+}
+
+type CodeHint common.Hash
+
+var _ preimage.Hint = CodeHint{}
+
+func (l CodeHint) Hint() string {
+	return "l2-code " + (common.Hash)(l).String()
+}
+
+type StateNodeHint common.Hash
+
+var _ preimage.Hint = StateNodeHint{}
+
+func (l StateNodeHint) Hint() string {
+	return "l2-state-node " + (common.Hash)(l).String()
+}

op-program/client/l2/oracle.go

 package l2
 
 import (
+	"fmt"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/rlp"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum-optimism/optimism/op-program/client/mpt"
+	"github.com/ethereum-optimism/optimism/op-program/preimage"
 )
 
 // StateOracle defines the high-level API used to retrieve L2 state data pre-images
@@ -11,13 +18,11 @@ 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
-	// Returns an error if the pre-image is unavailable.
-	NodeByHash(nodeHash common.Hash) ([]byte, error)
+	NodeByHash(nodeHash common.Hash) []byte
 
 	// CodeByHash retrieves the contract code pre-image for a given hash.
 	// codeHash should be retrieved from the world state account for a contract.
-	// Returns an error if the pre-image is unavailable.
-	CodeByHash(codeHash common.Hash) ([]byte, error)
+	CodeByHash(codeHash common.Hash) []byte
 }
 
 // Oracle defines the high-level API used to retrieve L2 data.
@@ -26,6 +31,57 @@ type Oracle interface {
 	StateOracle
 
 	// BlockByHash retrieves the block with the given hash.
-	// Returns an error if the block is not available.
-	BlockByHash(blockHash common.Hash) (*types.Block, error)
+	BlockByHash(blockHash common.Hash) *types.Block
+}
+
+// PreimageOracle implements Oracle using by interfacing with the pure preimage.Oracle
+// to fetch pre-images to decode into the requested data.
+type PreimageOracle struct {
+	oracle preimage.Oracle
+	hint   preimage.Hinter
+}
+
+var _ Oracle = (*PreimageOracle)(nil)
+
+func NewPreimageOracle(raw preimage.Oracle, hint preimage.Hinter) *PreimageOracle {
+	return &PreimageOracle{
+		oracle: raw,
+		hint:   hint,
+	}
+}
+
+func (p *PreimageOracle) headerByBlockHash(blockHash common.Hash) *types.Header {
+	p.hint.Hint(BlockHeaderHint(blockHash))
+	headerRlp := p.oracle.Get(preimage.Keccak256Key(blockHash))
+	var header types.Header
+	if err := rlp.DecodeBytes(headerRlp, &header); err != nil {
+		panic(fmt.Errorf("invalid block header %s: %w", blockHash, err))
+	}
+	return &header
+}
+
+func (p *PreimageOracle) BlockByHash(blockHash common.Hash) *types.Block {
+	header := p.headerByBlockHash(blockHash)
+	p.hint.Hint(TransactionsHint(blockHash))
+
+	opaqueTxs := mpt.ReadTrie(header.TxHash, func(key common.Hash) []byte {
+		return p.oracle.Get(preimage.Keccak256Key(key))
+	})
+
+	txs, err := eth.DecodeTransactions(opaqueTxs)
+	if err != nil {
+		panic(fmt.Errorf("failed to decode list of txs: %w", err))
+	}
+
+	return types.NewBlockWithHeader(header).WithBody(txs, nil)
+}
+
+func (p *PreimageOracle) NodeByHash(nodeHash common.Hash) []byte {
+	p.hint.Hint(StateNodeHint(nodeHash))
+	return p.oracle.Get(preimage.Keccak256Key(nodeHash))
+}
+
+func (p *PreimageOracle) CodeByHash(codeHash common.Hash) []byte {
+	p.hint.Hint(CodeHint(codeHash))
+	return p.oracle.Get(preimage.Keccak256Key(codeHash))
 }

op-program/client/l2/oracle_test.go

+package l2
+
+import (
+	"fmt"
+	"math/rand"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum-optimism/optimism/op-node/testutils"
+	"github.com/ethereum-optimism/optimism/op-program/client/mpt"
+	"github.com/ethereum-optimism/optimism/op-program/preimage"
+)
+
+func mockPreimageOracle(t *testing.T) (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 {
+			v, ok := preimages[key.PreimageKey()]
+			require.True(t, ok, "preimage must exist")
+			return v
+		}),
+		hint: preimage.HinterFn(func(v preimage.Hint) {
+			hintsMock.MethodCalled("hint", v.Hint())
+		}),
+	}
+
+	return po, hintsMock, preimages
+}
+
+// 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)
+
+	hdrBytes, err := rlp.EncodeToBytes(block.Header())
+	require.NoError(t, err)
+	preimages[preimage.Keccak256Key(block.Hash()).PreimageKey()] = hdrBytes
+
+	opaqueTxs, err := eth.EncodeTransactions(block.Transactions())
+	require.NoError(t, err)
+	_, txsNodes := mpt.WriteTrie(opaqueTxs)
+	for _, p := range txsNodes {
+		preimages[preimage.Keccak256Key(crypto.Keccak256Hash(p)).PreimageKey()] = p
+	}
+
+	// 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())
+	hints.AssertExpectations(t)
+
+	require.Equal(t, gotBlock.Hash(), block.Hash())
+	expectedTxs := block.Transactions()
+	require.Equal(t, len(expectedTxs), len(gotBlock.Transactions()), "expecting equal tx list length")
+	for i, tx := range gotBlock.Transactions() {
+		require.Equalf(t, tx.Hash(), expectedTxs[i].Hash(), "expecting tx %d to match", i)
+	}
+}
+
+func TestPreimageOracleBlockByHash(t *testing.T) {
+	rng := rand.New(rand.NewSource(123))
+
+	for i := 0; i < 10; i++ {
+		block, _ := testutils.RandomBlock(rng, 10)
+		t.Run(fmt.Sprintf("block_%d", i), func(t *testing.T) {
+			testBlock(t, block)
+		})
+	}
+}
+
+func TestPreimageOracleNodeByHash(t *testing.T) {
+	rng := rand.New(rand.NewSource(123))
+
+	for i := 0; i < 10; i++ {
+		t.Run(fmt.Sprintf("node_%d", i), func(t *testing.T) {
+			po, hints, preimages := mockPreimageOracle(t)
+
+			node := make([]byte, 123)
+			rng.Read(node)
+
+			h := crypto.Keccak256Hash(node)
+			preimages[preimage.Keccak256Key(h).PreimageKey()] = node
+
+			hints.On("hint", StateNodeHint(h).Hint()).Once().Return()
+			gotNode := po.NodeByHash(h)
+			hints.AssertExpectations(t)
+			require.Equal(t, hexutil.Bytes(node), hexutil.Bytes(gotNode), "node matches")
+		})
+	}
+}
+
+func TestPreimageOracleCodeByHash(t *testing.T) {
+	rng := rand.New(rand.NewSource(123))
+
+	for i := 0; i < 10; i++ {
+		t.Run(fmt.Sprintf("code_%d", i), func(t *testing.T) {
+			po, hints, preimages := mockPreimageOracle(t)
+
+			node := make([]byte, 123)
+			rng.Read(node)
+
+			h := crypto.Keccak256Hash(node)
+			preimages[preimage.Keccak256Key(h).PreimageKey()] = node
+
+			hints.On("hint", CodeHint(h).Hint()).Once().Return()
+			gotNode := po.CodeByHash(h)
+			hints.AssertExpectations(t)
+			require.Equal(t, hexutil.Bytes(node), hexutil.Bytes(gotNode), "code matches")
+		})
+	}
+}

op-program/client/l2/stub_oracle_test.go

+package l2
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/rawdb"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethdb"
+)
+
+type stubBlockOracle struct {
+	t      *testing.T
+	blocks map[common.Hash]*types.Block
+	StateOracle
+}
+
+func newStubOracle(t *testing.T) (*stubBlockOracle, *stubStateOracle) {
+	stateOracle := newStubStateOracle(t)
+	blockOracle := stubBlockOracle{
+		t:           t,
+		blocks:      make(map[common.Hash]*types.Block),
+		StateOracle: stateOracle,
+	}
+	return &blockOracle, stateOracle
+}
+
+func newStubOracleWithBlocks(t *testing.T, chain []*types.Block, db ethdb.Database) *stubBlockOracle {
+	blocks := make(map[common.Hash]*types.Block, len(chain))
+	for _, block := range chain {
+		blocks[block.Hash()] = block
+	}
+	return &stubBlockOracle{
+		blocks:      blocks,
+		StateOracle: &kvStateOracle{t: t, source: db},
+	}
+}
+
+func (o stubBlockOracle) BlockByHash(blockHash common.Hash) *types.Block {
+	block, ok := o.blocks[blockHash]
+	if !ok {
+		o.t.Fatalf("requested unknown block %s", blockHash)
+	}
+	return block
+}
+
+// kvStateOracle loads data from a source ethdb.KeyValueStore
+type kvStateOracle struct {
+	t      *testing.T
+	source ethdb.KeyValueStore
+}
+
+func (o *kvStateOracle) NodeByHash(nodeHash common.Hash) []byte {
+	val, err := o.source.Get(nodeHash.Bytes())
+	if err != nil {
+		o.t.Fatalf("error retrieving node %v: %v", nodeHash, err)
+	}
+	return val
+}
+
+func (o *kvStateOracle) CodeByHash(hash common.Hash) []byte {
+	return rawdb.ReadCode(o.source, hash)
+}
+
+func newStubStateOracle(t *testing.T) *stubStateOracle {
+	return &stubStateOracle{
+		t:    t,
+		data: make(map[common.Hash][]byte),
+		code: make(map[common.Hash][]byte),
+	}
+}
+
+// Stub StateOracle implementation that reads from simple maps
+type stubStateOracle struct {
+	t    *testing.T
+	data map[common.Hash][]byte
+	code map[common.Hash][]byte
+}
+
+func (o *stubStateOracle) NodeByHash(nodeHash common.Hash) []byte {
+	data, ok := o.data[nodeHash]
+	if !ok {
+		o.t.Fatalf("no value for node %v", nodeHash)
+	}
+	return data
+}
+
+func (o *stubStateOracle) CodeByHash(hash common.Hash) []byte {
+	data, ok := o.code[hash]
+	if !ok {
+		o.t.Fatalf("no value for code %v", hash)
+	}
+	return data
+}

op-program/client/mpt/db.go

+package mpt
+
+import "github.com/ethereum/go-ethereum/ethdb"
+
+type Hooks struct {
+	Get    func(key []byte) []byte
+	Put    func(key []byte, value []byte)
+	Delete func(key []byte)
+}
+
+// DB implements the ethdb.Database to back the StateDB of Geth.
+type DB struct {
+	db Hooks
+}
+
+func (p *DB) Has(key []byte) (bool, error) {
+	panic("not supported")
+}
+
+func (p *DB) Get(key []byte) ([]byte, error) {
+	return p.db.Get(key), nil
+}
+
+func (p *DB) Put(key []byte, value []byte) error {
+	p.db.Put(key, value)
+	return nil
+}
+
+func (p DB) Delete(key []byte) error {
+	p.db.Delete(key)
+	return nil
+}
+
+func (p DB) Stat(property string) (string, error) {
+	panic("not supported")
+}
+
+func (p DB) NewBatch() ethdb.Batch {
+	panic("not supported")
+}
+
+func (p DB) NewBatchWithSize(size int) ethdb.Batch {
+	panic("not supported")
+}
+
+func (p DB) NewIterator(prefix []byte, start []byte) ethdb.Iterator {
+	panic("not supported")
+}
+
+func (p DB) Compact(start []byte, limit []byte) error {
+	return nil // no-op
+}
+
+func (p DB) NewSnapshot() (ethdb.Snapshot, error) {
+	panic("not supported")
+}
+
+func (p DB) Close() error {
+	return nil
+}
+
+// We implement the full ethdb.Database bloat because the StateDB takes this full interface,
+// even though it only uses the KeyValue subset.
+
+func (p *DB) HasAncient(kind string, number uint64) (bool, error) {
+	panic("not supported")
+}
+
+func (p *DB) Ancient(kind string, number uint64) ([]byte, error) {
+	panic("not supported")
+}
+
+func (p *DB) AncientRange(kind string, start, count, maxBytes uint64) ([][]byte, error) {
+	panic("not supported")
+}
+
+func (p *DB) Ancients() (uint64, error) {
+	panic("not supported")
+}
+
+func (p *DB) Tail() (uint64, error) {
+	panic("not supported")
+}
+
+func (p *DB) AncientSize(kind string) (uint64, error) {
+	panic("not supported")
+}
+
+func (p *DB) ReadAncients(fn func(ethdb.AncientReaderOp) error) (err error) {
+	panic("not supported")
+}
+
+func (p *DB) ModifyAncients(f func(ethdb.AncientWriteOp) error) (int64, error) {
+	panic("not supported")
+}
+
+func (p *DB) TruncateHead(n uint64) error {
+	panic("not supported")
+}
+
+func (p *DB) TruncateTail(n uint64) error {
+	panic("not supported")
+}
+
+func (p *DB) Sync() error {
+	panic("not supported")
+}
+
+func (p *DB) MigrateTable(s string, f func([]byte) ([]byte, error)) error {
+	panic("not supported")
+}
+
+func (p *DB) AncientDatadir() (string, error) {
+	panic("not supported")
+}
+
+var _ ethdb.KeyValueStore = (*DB)(nil)

op-program/client/mpt/trie.go

+package mpt
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+// ReadTrie takes a Merkle Patricia Trie (MPT) root of a "DerivableList", and a pre-image oracle getter,
+// and traverses the implied MPT to collect all raw leaf nodes in order, which are then returned.
+func ReadTrie(root common.Hash, getPreimage func(key common.Hash) []byte) []hexutil.Bytes {
+	odb := &DB{db: Hooks{
+		Get: func(key []byte) []byte {
+			if len(key) != 32 {
+				panic(fmt.Errorf("expected 32 byte key query, but got %d bytes: %x", len(key), key))
+			}
+			return getPreimage(*(*[32]byte)(key))
+		},
+		Put: func(key []byte, value []byte) {
+			panic("put not supported")
+		},
+		Delete: func(key []byte) {
+			panic("delete not supported")
+		},
+	}}
+
+	// trie.New backed with a trie.NodeReader and trie.Reader seems really promising
+	// for a simple node-fetching backend, but the interface is half-private,
+	// while we already have the full database code for doing the same thing.
+	// Maybe it's still worth a small diff in geth to expose it?
+	// Diff would be:
+	//
+	//      type Node = node
+	//
+	//      func DecodeNode(hash, buf []byte) (node, error) {
+	//      	return decodeNode(hash, buf)
+	//      }
+	//
+	// And then still some code here to implement the trie.NodeReader and trie.Reader
+	// interfaces to map to the getPreimageFunction.
+	//
+	// For now we just use the state DB trie approach.
+
+	tdb := trie.NewDatabase(odb)
+	tr, err := trie.New(trie.TrieID(root), tdb)
+	if err != nil {
+		panic(err)
+	}
+	iter := tr.NodeIterator(nil)
+
+	// With small lists the iterator seems to use 0x80 (RLP empty string, unlike the others)
+	// as key for item 0, causing it to come last.
+	// Let's just remember the keys, and reorder them in the canonical order, to ensure it is correct.
+	var values [][]byte
+	var keys []uint64
+	for iter.Next(true) {
+		if iter.Leaf() {
+			k := iter.LeafKey()
+			var x uint64
+			err := rlp.DecodeBytes(k, &x)
+			if err != nil {
+				panic(fmt.Errorf("invalid key: %w", err))
+			}
+			keys = append(keys, x)
+			values = append(values, iter.LeafBlob())
+		}
+	}
+	out := make([]hexutil.Bytes, len(values))
+	for i, x := range keys {
+		if x >= uint64(len(values)) {
+			panic(fmt.Errorf("bad key: %d", x))
+		}
+		if out[x] != nil {
+			panic(fmt.Errorf("duplicate key %d", x))
+		}
+		out[x] = values[i]
+	}
+	return out
+}
+
+type rawList []hexutil.Bytes
+
+func (r rawList) Len() int {
+	return len(r)
+}
+
+func (r rawList) EncodeIndex(i int, buf *bytes.Buffer) {
+	buf.Write(r[i])
+}
+
+var _ types.DerivableList = rawList(nil)
+
+type noResetHasher struct {
+	*trie.StackTrie
+}
+
+// Reset is intercepted and is no-op, because we want to retain the writing function when calling types.DeriveSha
+func (n noResetHasher) Reset() {}
+
+// WriteTrie takes a list of values, and merkleizes them as a "DerivableList":
+// a Merkle Patricia Trie (MPT) with values keyed by their RLP encoded index.
+// This merkleization matches that of transactions, receipts, and withdrawals lists in the block header
+// (at least up to the Shanghai L1 update).
+// This then returns the MPT root and a list of pre-images of the trie.
+// Note: empty values are illegal, and there may be less pre-images returned than values,
+// if any values are less than 32 bytes and fit into branch-node slots that way.
+func WriteTrie(values []hexutil.Bytes) (common.Hash, []hexutil.Bytes) {
+	var out []hexutil.Bytes
+	st := noResetHasher{trie.NewStackTrie(
+		func(owner common.Hash, path []byte, hash common.Hash, blob []byte) {
+			out = append(out, common.CopyBytes(blob)) // the stack hasher may mutate the blob bytes, so copy them.
+		})}
+	root := types.DeriveSha(rawList(values), st)
+	return root, out
+}

op-program/client/mpt/trie_test.go

+package mpt
+
+import (
+	"fmt"
+	"math/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+type trieCase struct {
+	name     string
+	elements []hexutil.Bytes
+}
+
+func (tc *trieCase) run(t *testing.T) {
+	root, preimages := WriteTrie(tc.elements)
+	byHash := make(map[common.Hash][]byte)
+	for _, v := range preimages {
+		k := crypto.Keccak256Hash(v)
+		byHash[k] = v
+	}
+	results := ReadTrie(root, func(key common.Hash) []byte {
+		v, ok := byHash[key]
+		if !ok {
+			panic(fmt.Errorf("missing key %s", key))
+		}
+		return v
+	})
+	require.Equal(t, len(tc.elements), len(results), "expected equal amount of values")
+	for i, result := range results {
+		// hex encoded for debugging readability
+		require.Equal(t, tc.elements[i].String(), result.String(),
+			"value %d does not match, expected equal value data", i)
+	}
+}
+
+func TestListTrieRoundtrip(t *testing.T) {
+	testCases := []trieCase{
+		{name: "empty list", elements: []hexutil.Bytes{}},
+		{name: "nil list", elements: nil},
+		{name: "simple", elements: []hexutil.Bytes{[]byte("hello"), []byte("world")}},
+	}
+	rng := rand.New(rand.NewSource(1234))
+	// add some randomized cases
+	for i := 0; i < 30; i++ {
+		n := rng.Intn(300)
+		elems := make([]hexutil.Bytes, n)
+		for i := range elems {
+			length := 1 + rng.Intn(300) // empty items not allowed
+			data := make([]byte, length)
+			rng.Read(data[:])
+			elems[i] = data
+		}
+		testCases = append(testCases, trieCase{name: fmt.Sprintf("rand_%d", i), elements: elems})
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, tc.run)
+	}
+}

op-program/host/cmd/main.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/ethereum-optimism/optimism/op-node/chaincfg"
+	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
 	cldr "github.com/ethereum-optimism/optimism/op-program/client/driver"
 	"github.com/ethereum-optimism/optimism/op-program/host/config"
@@ -41,6 +42,10 @@ var VersionWithMeta = func() string {
 	return v
 }()
 
+var (
+	ErrClaimNotValid = errors.New("invalid claim")
+)
+
 func main() {
 	args := os.Args
 	err := run(args, FaultProofProgram)
@@ -124,6 +129,9 @@ func FaultProofProgram(logger log.Logger, cfg *config.Config) error {
 			return err
 		}
 	}
-	logger.Info("Derivation complete", "head", d.SafeHead())
+	claim := cfg.L2Claim
+	if !d.ValidateClaim(eth.Bytes32(claim)) {
+		return ErrClaimNotValid
+	}
 	return nil
 }

op-program/host/cmd/main_test.go

@@ -13,7 +13,10 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-var l2HeadValue = "0x6303578b1fa9480389c51bbcef6fe045bb877da39740819e9eb5f36f94949bd0"
+// Use HexToHash(...).Hex() to ensure the strings are the correct length for a hash
+var l1HeadValue = common.HexToHash("0x111111").Hex()
+var l2HeadValue = common.HexToHash("0x222222").Hex()
+var l2ClaimValue = common.HexToHash("0x333333").Hex()
 
 func TestLogLevel(t *testing.T) {
 	t.Run("RejectInvalid", func(t *testing.T) {
@@ -32,7 +35,13 @@ func TestLogLevel(t *testing.T) {
 
 func TestDefaultCLIOptionsMatchDefaultConfig(t *testing.T) {
 	cfg := configForArgs(t, addRequiredArgs())
-	require.Equal(t, config.NewConfig(&chaincfg.Goerli, "genesis.json", common.HexToHash(l2HeadValue)), cfg)
+	defaultCfg := config.NewConfig(
+		&chaincfg.Goerli,
+		"genesis.json",
+		common.HexToHash(l1HeadValue),
+		common.HexToHash(l2HeadValue),
+		common.HexToHash(l2ClaimValue))
+	require.Equal(t, defaultCfg, cfg)
 }
 
 func TestNetwork(t *testing.T) {
@@ -102,6 +111,21 @@ func TestL2Head(t *testing.T) {
 	})
 }
 
+func TestL1Head(t *testing.T) {
+	t.Run("Required", func(t *testing.T) {
+		verifyArgsInvalid(t, "flag l1.head is required", addRequiredArgsExcept("--l1.head"))
+	})
+
+	t.Run("Valid", func(t *testing.T) {
+		cfg := configForArgs(t, replaceRequiredArg("--l1.head", l1HeadValue))
+		require.Equal(t, common.HexToHash(l1HeadValue), cfg.L1Head)
+	})
+
+	t.Run("Invalid", func(t *testing.T) {
+		verifyArgsInvalid(t, config.ErrInvalidL1Head.Error(), replaceRequiredArg("--l1.head", "something"))
+	})
+}
+
 func TestL1(t *testing.T) {
 	expected := "https://example.com:8545"
 	cfg := configForArgs(t, addRequiredArgs("--l1", expected))
@@ -149,10 +173,26 @@ func TestL1RPCKind(t *testing.T) {
 // Offline support will be added later, but for now it just bails out with an error
 func TestOfflineModeNotSupported(t *testing.T) {
 	logger := log.New()
-	err := FaultProofProgram(logger, config.NewConfig(&chaincfg.Goerli, "genesis.json", common.HexToHash(l2HeadValue)))
+	cfg := config.NewConfig(&chaincfg.Goerli, "genesis.json", common.HexToHash(l1HeadValue), common.HexToHash(l2HeadValue), common.HexToHash(l2ClaimValue))
+	err := FaultProofProgram(logger, cfg)
 	require.ErrorContains(t, err, "offline mode not supported")
 }
 
+func TestL2Claim(t *testing.T) {
+	t.Run("Required", func(t *testing.T) {
+		verifyArgsInvalid(t, "flag l2.claim is required", addRequiredArgsExcept("--l2.claim"))
+	})
+
+	t.Run("Valid", func(t *testing.T) {
+		cfg := configForArgs(t, replaceRequiredArg("--l2.claim", l2ClaimValue))
+		require.EqualValues(t, common.HexToHash(l2ClaimValue), cfg.L2Claim)
+	})
+
+	t.Run("Invalid", func(t *testing.T) {
+		verifyArgsInvalid(t, config.ErrInvalidL2Claim.Error(), replaceRequiredArg("--l2.claim", "something"))
+	})
+}
+
 func verifyArgsInvalid(t *testing.T, messageContains string, cliArgs []string) {
 	_, _, err := runWithArgs(cliArgs)
 	require.ErrorContains(t, err, messageContains)
@@ -199,8 +239,10 @@ func replaceRequiredArg(name string, value string) []string {
 func requiredArgs() map[string]string {
 	return map[string]string{
 		"--network":    "goerli",
-		"--l2.genesis": "genesis.json",
+		"--l1.head":    l1HeadValue,
 		"--l2.head":    l2HeadValue,
+		"--l2.claim":   l2ClaimValue,
+		"--l2.genesis": "genesis.json",
 	}
 }
 

op-program/host/config/config.go

@@ -14,15 +14,19 @@ import (
 var (
 	ErrMissingRollupConfig = errors.New("missing rollup config")
 	ErrMissingL2Genesis    = errors.New("missing l2 genesis")
+	ErrInvalidL1Head       = errors.New("invalid l1 head")
 	ErrInvalidL2Head       = errors.New("invalid l2 head")
 	ErrL1AndL2Inconsistent = errors.New("l1 and l2 options must be specified together or both omitted")
+	ErrInvalidL2Claim      = errors.New("invalid l2 claim")
 )
 
 type Config struct {
 	Rollup        *rollup.Config
 	L2URL         string
 	L2GenesisPath string
+	L1Head        common.Hash
 	L2Head        common.Hash
+	L2Claim       common.Hash
 	L1URL         string
 	L1TrustRPC    bool
 	L1RPCKind     sources.RPCProviderKind
@@ -35,12 +39,18 @@ func (c *Config) Check() error {
 	if err := c.Rollup.Check(); err != nil {
 		return err
 	}
-	if c.L2GenesisPath == "" {
-		return ErrMissingL2Genesis
+	if c.L1Head == (common.Hash{}) {
+		return ErrInvalidL1Head
 	}
 	if c.L2Head == (common.Hash{}) {
 		return ErrInvalidL2Head
 	}
+	if c.L2Claim == (common.Hash{}) {
+		return ErrInvalidL2Claim
+	}
+	if c.L2GenesisPath == "" {
+		return ErrMissingL2Genesis
+	}
 	if (c.L1URL != "") != (c.L2URL != "") {
 		return ErrL1AndL2Inconsistent
 	}
@@ -52,11 +62,13 @@ func (c *Config) FetchingEnabled() bool {
 }
 
 // NewConfig creates a Config with all optional values set to the CLI default value
-func NewConfig(rollupCfg *rollup.Config, l2GenesisPath string, l2Head common.Hash) *Config {
+func NewConfig(rollupCfg *rollup.Config, l2GenesisPath string, l1Head common.Hash, l2Head common.Hash, l2Claim common.Hash) *Config {
 	return &Config{
 		Rollup:        rollupCfg,
 		L2GenesisPath: l2GenesisPath,
+		L1Head:        l1Head,
 		L2Head:        l2Head,
+		L2Claim:       l2Claim,
 		L1RPCKind:     sources.RPCKindBasic,
 	}
 }
@@ -73,11 +85,21 @@ func NewConfigFromCLI(ctx *cli.Context) (*Config, error) {
 	if l2Head == (common.Hash{}) {
 		return nil, ErrInvalidL2Head
 	}
+	l2Claim := common.HexToHash(ctx.GlobalString(flags.L2Claim.Name))
+	if l2Claim == (common.Hash{}) {
+		return nil, ErrInvalidL2Claim
+	}
+	l1Head := common.HexToHash(ctx.GlobalString(flags.L1Head.Name))
+	if l1Head == (common.Hash{}) {
+		return nil, ErrInvalidL1Head
+	}
 	return &Config{
 		Rollup:        rollupCfg,
 		L2URL:         ctx.GlobalString(flags.L2NodeAddr.Name),
 		L2GenesisPath: ctx.GlobalString(flags.L2GenesisPath.Name),
 		L2Head:        l2Head,
+		L2Claim:       l2Claim,
+		L1Head:        l1Head,
 		L1URL:         ctx.GlobalString(flags.L1NodeAddr.Name),
 		L1TrustRPC:    ctx.GlobalBool(flags.L1TrustRPC.Name),
 		L1RPCKind:     sources.RPCProviderKind(ctx.GlobalString(flags.L1RPCProviderKind.Name)),

op-program/host/config/config_test.go

@@ -11,66 +11,78 @@ import (
 
 var validRollupConfig = &chaincfg.Goerli
 var validL2GenesisPath = "genesis.json"
-var validL2Head = common.HexToHash("0x6303578b1fa9480389c51bbcef6fe045bb877da39740819e9eb5f36f94949bd0")
+var validL1Head = common.Hash{0xaa}
+var validL2Head = common.Hash{0xbb}
+var validL2Claim = common.Hash{0xcc}
 
 func TestDefaultConfigIsValid(t *testing.T) {
-	err := NewConfig(validRollupConfig, validL2GenesisPath, validL2Head).Check()
+	err := validConfig().Check()
 	require.NoError(t, err)
 }
 
 func TestRollupConfig(t *testing.T) {
 	t.Run("Required", func(t *testing.T) {
-		err := NewConfig(nil, validL2GenesisPath, validL2Head).Check()
+		config := validConfig()
+		config.Rollup = nil
+		err := config.Check()
 		require.ErrorIs(t, err, ErrMissingRollupConfig)
 	})
 
 	t.Run("Invalid", func(t *testing.T) {
-		err := NewConfig(&rollup.Config{}, validL2GenesisPath, validL2Head).Check()
+		config := validConfig()
+		config.Rollup = &rollup.Config{}
+		err := config.Check()
 		require.ErrorIs(t, err, rollup.ErrBlockTimeZero)
 	})
 }
 
-func TestL2Genesis(t *testing.T) {
-	t.Run("Required", func(t *testing.T) {
-		err := NewConfig(validRollupConfig, "", validL2Head).Check()
-		require.ErrorIs(t, err, ErrMissingL2Genesis)
-	})
-
-	t.Run("Valid", func(t *testing.T) {
-		err := NewConfig(validRollupConfig, validL2GenesisPath, validL2Head).Check()
-		require.NoError(t, err)
-	})
+func TestL1HeadRequired(t *testing.T) {
+	config := validConfig()
+	config.L1Head = common.Hash{}
+	err := config.Check()
+	require.ErrorIs(t, err, ErrInvalidL1Head)
 }
 
-func TestL2Head(t *testing.T) {
-	t.Run("Required", func(t *testing.T) {
-		err := NewConfig(validRollupConfig, validL2GenesisPath, common.Hash{}).Check()
+func TestL2HeadRequired(t *testing.T) {
+	config := validConfig()
+	config.L2Head = common.Hash{}
+	err := config.Check()
 	require.ErrorIs(t, err, ErrInvalidL2Head)
-	})
+}
 
-	t.Run("Valid", func(t *testing.T) {
-		err := NewConfig(validRollupConfig, validL2GenesisPath, validL2Head).Check()
-		require.NoError(t, err)
-	})
+func TestL2ClaimRequired(t *testing.T) {
+	config := validConfig()
+	config.L2Claim = common.Hash{}
+	err := config.Check()
+	require.ErrorIs(t, err, ErrInvalidL2Claim)
+}
+
+func TestL2GenesisRequired(t *testing.T) {
+	config := validConfig()
+	config.L2GenesisPath = ""
+	err := config.Check()
+	require.ErrorIs(t, err, ErrMissingL2Genesis)
 }
 
 func TestFetchingArgConsistency(t *testing.T) {
 	t.Run("RequireL2WhenL1Set", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL2Head)
+		cfg := validConfig()
 		cfg.L1URL = "https://example.com:1234"
 		require.ErrorIs(t, cfg.Check(), ErrL1AndL2Inconsistent)
 	})
 	t.Run("RequireL1WhenL2Set", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL2Head)
+		cfg := validConfig()
 		cfg.L2URL = "https://example.com:1234"
 		require.ErrorIs(t, cfg.Check(), ErrL1AndL2Inconsistent)
 	})
 	t.Run("AllowNeitherSet", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL2Head)
+		cfg := validConfig()
+		cfg.L1URL = ""
+		cfg.L2URL = ""
 		require.NoError(t, cfg.Check())
 	})
 	t.Run("AllowBothSet", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL2Head)
+		cfg := validConfig()
 		cfg.L1URL = "https://example.com:1234"
 		cfg.L2URL = "https://example.com:4678"
 		require.NoError(t, cfg.Check())
@@ -79,32 +91,36 @@ func TestFetchingArgConsistency(t *testing.T) {
 
 func TestFetchingEnabled(t *testing.T) {
 	t.Run("FetchingNotEnabledWhenNoFetcherUrlsSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL2Head)
+		cfg := validConfig()
 		require.False(t, cfg.FetchingEnabled(), "Should not enable fetching when node URL not supplied")
 	})
 
 	t.Run("FetchingEnabledWhenFetcherUrlsSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL2Head)
+		cfg := validConfig()
 		cfg.L2URL = "https://example.com:1234"
 		require.False(t, cfg.FetchingEnabled(), "Should not enable fetching when node URL not supplied")
 	})
 
 	t.Run("FetchingNotEnabledWhenNoL1UrlSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL2Head)
+		cfg := validConfig()
 		cfg.L2URL = "https://example.com:1234"
 		require.False(t, cfg.FetchingEnabled(), "Should not enable L1 fetching when L1 node URL not supplied")
 	})
 
 	t.Run("FetchingNotEnabledWhenNoL2UrlSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL2Head)
+		cfg := validConfig()
 		cfg.L1URL = "https://example.com:1234"
 		require.False(t, cfg.FetchingEnabled(), "Should not enable L2 fetching when L2 node URL not supplied")
 	})
 
 	t.Run("FetchingEnabledWhenBothFetcherUrlsSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL2Head)
+		cfg := validConfig()
 		cfg.L1URL = "https://example.com:1234"
 		cfg.L2URL = "https://example.com:5678"
 		require.True(t, cfg.FetchingEnabled(), "Should enable fetching when node URL supplied")
 	})
 }
+
+func validConfig() *Config {
+	return NewConfig(validRollupConfig, validL2GenesisPath, validL1Head, validL2Head, validL2Claim)
+}

op-program/host/flags/flags.go

@@ -31,16 +31,26 @@ var (
 		Usage:  "Address of L2 JSON-RPC endpoint to use (eth and debug namespace required)",
 		EnvVar: service.PrefixEnvVar(envVarPrefix, "L2_RPC"),
 	}
-	L2GenesisPath = cli.StringFlag{
-		Name:   "l2.genesis",
-		Usage:  "Path to the op-geth genesis file",
-		EnvVar: service.PrefixEnvVar(envVarPrefix, "L2_GENESIS"),
+	L1Head = cli.StringFlag{
+		Name:   "l1.head",
+		Usage:  "Hash of the L1 head block. Derivation stops after this block is processed.",
+		EnvVar: service.PrefixEnvVar(envVarPrefix, "L1_HEAD"),
 	}
 	L2Head = cli.StringFlag{
 		Name:   "l2.head",
 		Usage:  "Hash of the agreed L2 block to start derivation from",
 		EnvVar: service.PrefixEnvVar(envVarPrefix, "L2_HEAD"),
 	}
+	L2Claim = cli.StringFlag{
+		Name:   "l2.claim",
+		Usage:  "Claimed L2 output root to validate",
+		EnvVar: service.PrefixEnvVar(envVarPrefix, "L2_CLAIM"),
+	}
+	L2GenesisPath = cli.StringFlag{
+		Name:   "l2.genesis",
+		Usage:  "Path to the op-geth genesis file",
+		EnvVar: service.PrefixEnvVar(envVarPrefix, "L2_GENESIS"),
+	}
 	L1NodeAddr = cli.StringFlag{
 		Name:   "l1",
 		Usage:  "Address of L1 JSON-RPC endpoint to use (eth namespace required)",
@@ -66,12 +76,16 @@ var (
 // Flags contains the list of configuration options available to the binary.
 var Flags []cli.Flag
 
+var requiredFlags = []cli.Flag{
+	L1Head,
+	L2Head,
+	L2Claim,
+	L2GenesisPath,
+}
 var programFlags = []cli.Flag{
 	RollupConfig,
 	Network,
 	L2NodeAddr,
-	L2GenesisPath,
-	L2Head,
 	L1NodeAddr,
 	L1TrustRPC,
 	L1RPCProviderKind,
@@ -79,6 +93,7 @@ var programFlags = []cli.Flag{
 
 func init() {
 	Flags = append(Flags, oplog.CLIFlags(envVarPrefix)...)
+	Flags = append(Flags, requiredFlags...)
 	Flags = append(Flags, programFlags...)
 }
 
@@ -91,11 +106,10 @@ func CheckRequired(ctx *cli.Context) error {
 	if rollupConfig != "" && network != "" {
 		return fmt.Errorf("cannot specify both %s and %s", RollupConfig.Name, Network.Name)
 	}
-	if ctx.GlobalString(L2GenesisPath.Name) == "" {
-		return fmt.Errorf("flag %s is required", L2GenesisPath.Name)
+	for _, flag := range requiredFlags {
+		if ctx.GlobalString(flag.GetName()) == "" {
+			return fmt.Errorf("flag %s is required", flag.GetName())
 		}
-	if ctx.GlobalString(L2Head.Name) == "" {
-		return fmt.Errorf("flag %s is required", L2Head.Name)
 	}
 	return nil
 }

op-program/host/kvstore/disk.go

+package kvstore
+
+import (
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"sync"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// read/write mode for user/group/other, not executable.
+const diskPermission = 0666
+
+// DiskKV is a disk-backed key-value store, every key-value pair is a hex-encoded .txt file, with the value as content.
+// DiskKV is safe for concurrent use with a single DiskKV instance.
+// DiskKV is not safe for concurrent use between different DiskKV instances of the same disk directory:
+// a Put needs to be completed before another DiskKV Get retrieves the values.
+type DiskKV struct {
+	sync.RWMutex
+	path string
+}
+
+// NewDiskKV creates a DiskKV that puts/gets pre-images as files in the given directory path.
+// The path must exist, or subsequent Put/Get calls will error when it does not.
+func NewDiskKV(path string) *DiskKV {
+	return &DiskKV{path: path}
+}
+
+func (d *DiskKV) pathKey(k common.Hash) string {
+	return path.Join(d.path, k.String()+".txt")
+}
+
+func (d *DiskKV) Put(k common.Hash, v []byte) error {
+	d.Lock()
+	defer d.Unlock()
+	f, err := os.OpenFile(d.pathKey(k), os.O_WRONLY|os.O_CREATE|os.O_EXCL|os.O_TRUNC, diskPermission)
+	if err != nil {
+		if errors.Is(err, os.ErrExist) {
+			return ErrAlreadyExists
+		}
+		return fmt.Errorf("failed to open new pre-image file %s: %w", k, err)
+	}
+	if _, err := f.Write([]byte(hex.EncodeToString(v))); err != nil {
+		_ = f.Close()
+		return fmt.Errorf("failed to write pre-image %s to disk: %w", k, err)
+	}
+	if err := f.Close(); err != nil {
+		return fmt.Errorf("failed to close pre-image %s file: %w", k, err)
+	}
+	return nil
+}
+
+func (d *DiskKV) Get(k common.Hash) ([]byte, error) {
+	d.RLock()
+	defer d.RUnlock()
+	f, err := os.OpenFile(d.pathKey(k), os.O_RDONLY, diskPermission)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, ErrNotFound
+		}
+		return nil, fmt.Errorf("failed to open pre-image file %s: %w", k, err)
+	}
+	defer f.Close() // fine to ignore closing error here
+	dat, err := io.ReadAll(f)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read pre-image from file %s: %w", k, err)
+	}
+	return hex.DecodeString(string(dat))
+}
+
+var _ KV = (*DiskKV)(nil)

op-program/host/kvstore/disk_test.go

+package kvstore
+
+import "testing"
+
+func TestDiskKV(t *testing.T) {
+	tmp := t.TempDir() // automatically removed by testing cleanup
+	kv := NewDiskKV(tmp)
+	kvTest(t, kv)
+}

op-program/host/kvstore/kv.go

+package kvstore
+
+import (
+	"errors"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// ErrNotFound is returned when a pre-image cannot be found in the KV store.
+var ErrNotFound = errors.New("not found")
+
+// ErrAlreadyExists is returned when a pre-image already exists in the KV store.
+var ErrAlreadyExists = errors.New("already exists")
+
+// KV is a Key-Value store interface for pre-image data.
+type KV interface {
+	// Put puts the pre-image value v in the key-value store with key k.
+	// It returns ErrAlreadyExists when the key already exists.
+	// KV store implementations may return additional errors specific to the KV storage.
+	Put(k common.Hash, v []byte) error
+
+	// Get retrieves the pre-image with key k from the key-value store.
+	// It returns ErrNotFound when the pre-image cannot be found.
+	// KV store implementations may return additional errors specific to the KV storage.
+	Get(k common.Hash) ([]byte, error)
+}

op-program/host/kvstore/kv_test.go

+package kvstore
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/stretchr/testify/require"
+)
+
+func kvTest(t *testing.T, kv KV) {
+	t.Run("roundtrip", func(t *testing.T) {
+		t.Parallel()
+		_, err := kv.Get(common.Hash{0xaa})
+		require.Equal(t, err, ErrNotFound, "file (in new tmp dir) does not exist yet")
+
+		require.NoError(t, kv.Put(common.Hash{0xaa}, []byte("hello world")))
+		dat, err := kv.Get(common.Hash{0xaa})
+		require.NoError(t, err, "pre-image must exist now")
+		require.Equal(t, "hello world", string(dat), "pre-image must match")
+	})
+
+	t.Run("empty pre-image", func(t *testing.T) {
+		t.Parallel()
+		require.NoError(t, kv.Put(common.Hash{0xbb}, []byte{}))
+		dat, err := kv.Get(common.Hash{0xbb})
+		require.NoError(t, err, "pre-image must exist now")
+		require.Zero(t, len(dat), "pre-image must be empty")
+	})
+
+	t.Run("zero pre-image key", func(t *testing.T) {
+		t.Parallel()
+		// in case we give a pre-image a special empty key. If it was a hash then we wouldn't know the pre-image.
+		require.NoError(t, kv.Put(common.Hash{}, []byte("hello")))
+		dat, err := kv.Get(common.Hash{})
+		require.NoError(t, err, "pre-image must exist now")
+		require.Equal(t, "hello", string(dat), "pre-image must match")
+	})
+
+	t.Run("non-string value", func(t *testing.T) {
+		t.Parallel()
+		// in case we give a pre-image a special empty key. If it was a hash then we wouldn't know the pre-image.
+		require.NoError(t, kv.Put(common.Hash{0xcc}, []byte{4, 2}))
+		dat, err := kv.Get(common.Hash{0xcc})
+		require.NoError(t, err, "pre-image must exist now")
+		require.Equal(t, []byte{4, 2}, dat, "pre-image must match")
+	})
+
+	t.Run("not overwriting pre-image", func(t *testing.T) {
+		t.Parallel()
+		require.NoError(t, kv.Put(common.Hash{0xdd}, []byte{4, 2}))
+		require.ErrorIs(t, kv.Put(common.Hash{0xdd}, []byte{4, 2}), ErrAlreadyExists)
+	})
+}

op-program/host/kvstore/mem.go

+package kvstore
+
+import (
+	"sync"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// MemKV implements the KV store interface in memory, backed by a regular Go map.
+// This should only be used in testing, as large programs may require more pre-image data than available memory.
+// MemKV is safe for concurrent use.
+type MemKV struct {
+	sync.RWMutex
+	m map[common.Hash][]byte
+}
+
+var _ KV = (*MemKV)(nil)
+
+func NewMemKV() *MemKV {
+	return &MemKV{m: make(map[common.Hash][]byte)}
+}
+
+func (m *MemKV) Put(k common.Hash, v []byte) error {
+	m.Lock()
+	defer m.Unlock()
+	if _, ok := m.m[k]; ok {
+		return ErrAlreadyExists
+	}
+	m.m[k] = v
+	return nil
+}
+
+func (m *MemKV) Get(k common.Hash) ([]byte, error) {
+	m.RLock()
+	defer m.RUnlock()
+	v, ok := m.m[k]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return v, nil
+}

op-program/host/kvstore/mem_test.go

+package kvstore
+
+import "testing"
+
+func TestMemKV(t *testing.T) {
+	kv := NewMemKV()
+	kvTest(t, kv)
+}

op-program/host/l1/fetcher.go

+package l1
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+)
+
+type Source interface {
+	InfoByHash(ctx context.Context, blockHash common.Hash) (eth.BlockInfo, error)
+	InfoAndTxsByHash(ctx context.Context, blockHash common.Hash) (eth.BlockInfo, types.Transactions, error)
+	FetchReceipts(ctx context.Context, blockHash common.Hash) (eth.BlockInfo, types.Receipts, error)
+}
+
+type FetchingL1Oracle struct {
+	ctx    context.Context
+	logger log.Logger
+	source Source
+}
+
+func NewFetchingL1Oracle(ctx context.Context, logger log.Logger, source Source) *FetchingL1Oracle {
+	return &FetchingL1Oracle{
+		ctx:    ctx,
+		logger: logger,
+		source: source,
+	}
+}
+
+func (o *FetchingL1Oracle) HeaderByBlockHash(blockHash common.Hash) eth.BlockInfo {
+	o.logger.Trace("HeaderByBlockHash", "hash", blockHash)
+	info, err := o.source.InfoByHash(o.ctx, blockHash)
+	if err != nil {
+		panic(fmt.Errorf("retrieve block %s: %w", blockHash, err))
+	}
+	if info == nil {
+		panic(fmt.Errorf("unknown block: %s", blockHash))
+	}
+	return info
+}
+
+func (o *FetchingL1Oracle) TransactionsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Transactions) {
+	o.logger.Trace("TransactionsByBlockHash", "hash", blockHash)
+	info, txs, err := o.source.InfoAndTxsByHash(o.ctx, blockHash)
+	if err != nil {
+		panic(fmt.Errorf("retrieve transactions for block %s: %w", blockHash, err))
+	}
+	if info == nil || txs == nil {
+		panic(fmt.Errorf("unknown block: %s", blockHash))
+	}
+	return info, txs
+}
+
+func (o *FetchingL1Oracle) ReceiptsByBlockHash(blockHash common.Hash) (eth.BlockInfo, types.Receipts) {
+	o.logger.Trace("ReceiptsByBlockHash", "hash", blockHash)
+	info, rcpts, err := o.source.FetchReceipts(o.ctx, blockHash)
+	if err != nil {
+		panic(fmt.Errorf("retrieve receipts for block %s: %w", blockHash, err))
+	}
+	if info == nil || rcpts == nil {
+		panic(fmt.Errorf("unknown block: %s", blockHash))
+	}
+	return info, rcpts
+}

op-program/host/l1/fetcher_test.go

+package l1
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum-optimism/optimism/op-node/sources"
+	"github.com/ethereum-optimism/optimism/op-node/testlog"
+	cll1 "github.com/ethereum-optimism/optimism/op-program/client/l1"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/stretchr/testify/require"
+)
+
+// Needs to implement the Oracle interface
+var _ cll1.Oracle = (*FetchingL1Oracle)(nil)
+
+// Want to be able to use an L1Client as the data source
+var _ Source = (*sources.L1Client)(nil)
+
+func TestHeaderByHash(t *testing.T) {
+	t.Run("Success", func(t *testing.T) {
+		expected := &sources.HeaderInfo{}
+		source := &stubSource{nextInfo: expected}
+		oracle := newFetchingOracle(t, source)
+
+		actual := oracle.HeaderByBlockHash(expected.Hash())
+		require.Equal(t, expected, actual)
+	})
+
+	t.Run("UnknownBlock", func(t *testing.T) {
+		oracle := newFetchingOracle(t, &stubSource{})
+		hash := common.HexToHash("0x4455")
+		require.PanicsWithError(t, fmt.Errorf("unknown block: %s", hash).Error(), func() {
+			oracle.HeaderByBlockHash(hash)
+		})
+	})
+
+	t.Run("Error", func(t *testing.T) {
+		err := errors.New("kaboom")
+		source := &stubSource{nextErr: err}
+		oracle := newFetchingOracle(t, source)
+
+		hash := common.HexToHash("0x8888")
+		require.PanicsWithError(t, fmt.Errorf("retrieve block %s: %w", hash, err).Error(), func() {
+			oracle.HeaderByBlockHash(hash)
+		})
+	})
+}
+
+func TestTransactionsByHash(t *testing.T) {
+	t.Run("Success", func(t *testing.T) {
+		expectedInfo := &sources.HeaderInfo{}
+		expectedTxs := types.Transactions{
+			&types.Transaction{},
+		}
+		source := &stubSource{nextInfo: expectedInfo, nextTxs: expectedTxs}
+		oracle := newFetchingOracle(t, source)
+
+		info, txs := oracle.TransactionsByBlockHash(expectedInfo.Hash())
+		require.Equal(t, expectedInfo, info)
+		require.Equal(t, expectedTxs, txs)
+	})
+
+	t.Run("UnknownBlock_NoInfo", func(t *testing.T) {
+		oracle := newFetchingOracle(t, &stubSource{})
+		hash := common.HexToHash("0x4455")
+		require.PanicsWithError(t, fmt.Errorf("unknown block: %s", hash).Error(), func() {
+			oracle.TransactionsByBlockHash(hash)
+		})
+	})
+
+	t.Run("UnknownBlock_NoTxs", func(t *testing.T) {
+		oracle := newFetchingOracle(t, &stubSource{nextInfo: &sources.HeaderInfo{}})
+		hash := common.HexToHash("0x4455")
+		require.PanicsWithError(t, fmt.Errorf("unknown block: %s", hash).Error(), func() {
+			oracle.TransactionsByBlockHash(hash)
+		})
+	})
+
+	t.Run("Error", func(t *testing.T) {
+		err := errors.New("kaboom")
+		source := &stubSource{nextErr: err}
+		oracle := newFetchingOracle(t, source)
+
+		hash := common.HexToHash("0x8888")
+		require.PanicsWithError(t, fmt.Errorf("retrieve transactions for block %s: %w", hash, err).Error(), func() {
+			oracle.TransactionsByBlockHash(hash)
+		})
+	})
+}
+
+func TestReceiptsByHash(t *testing.T) {
+	t.Run("Success", func(t *testing.T) {
+		expectedInfo := &sources.HeaderInfo{}
+		expectedRcpts := types.Receipts{
+			&types.Receipt{},
+		}
+		source := &stubSource{nextInfo: expectedInfo, nextRcpts: expectedRcpts}
+		oracle := newFetchingOracle(t, source)
+
+		info, rcpts := oracle.ReceiptsByBlockHash(expectedInfo.Hash())
+		require.Equal(t, expectedInfo, info)
+		require.Equal(t, expectedRcpts, rcpts)
+	})
+
+	t.Run("UnknownBlock_NoInfo", func(t *testing.T) {
+		oracle := newFetchingOracle(t, &stubSource{})
+		hash := common.HexToHash("0x4455")
+		require.PanicsWithError(t, fmt.Errorf("unknown block: %s", hash).Error(), func() {
+			oracle.ReceiptsByBlockHash(hash)
+		})
+	})
+
+	t.Run("UnknownBlock_NoTxs", func(t *testing.T) {
+		oracle := newFetchingOracle(t, &stubSource{nextInfo: &sources.HeaderInfo{}})
+		hash := common.HexToHash("0x4455")
+		require.PanicsWithError(t, fmt.Errorf("unknown block: %s", hash).Error(), func() {
+			oracle.ReceiptsByBlockHash(hash)
+		})
+	})
+
+	t.Run("Error", func(t *testing.T) {
+		err := errors.New("kaboom")
+		source := &stubSource{nextErr: err}
+		oracle := newFetchingOracle(t, source)
+
+		hash := common.HexToHash("0x8888")
+		require.PanicsWithError(t, fmt.Errorf("retrieve receipts for block %s: %w", hash, err).Error(), func() {
+			oracle.ReceiptsByBlockHash(hash)
+		})
+	})
+}
+
+func newFetchingOracle(t *testing.T, source Source) *FetchingL1Oracle {
+	return NewFetchingL1Oracle(context.Background(), testlog.Logger(t, log.LvlDebug), source)
+}
+
+type stubSource struct {
+	nextInfo  eth.BlockInfo
+	nextTxs   types.Transactions
+	nextRcpts types.Receipts
+	nextErr   error
+}
+
+func (s stubSource) InfoByHash(ctx context.Context, blockHash common.Hash) (eth.BlockInfo, error) {
+	return s.nextInfo, s.nextErr
+}
+
+func (s stubSource) InfoAndTxsByHash(ctx context.Context, blockHash common.Hash) (eth.BlockInfo, types.Transactions, error) {
+	return s.nextInfo, s.nextTxs, s.nextErr
+}
+
+func (s stubSource) FetchReceipts(ctx context.Context, blockHash common.Hash) (eth.BlockInfo, types.Receipts, error) {
+	return s.nextInfo, s.nextRcpts, s.nextErr
+}

op-program/host/l1/l1.go

@@ -6,6 +6,7 @@ import (
 	"github.com/ethereum-optimism/optimism/op-node/client"
 	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
 	"github.com/ethereum-optimism/optimism/op-node/sources"
+	cll1 "github.com/ethereum-optimism/optimism/op-program/client/l1"
 	"github.com/ethereum-optimism/optimism/op-program/host/config"
 	"github.com/ethereum/go-ethereum/log"
 )
@@ -16,5 +17,10 @@ func NewFetchingL1(ctx context.Context, logger log.Logger, cfg *config.Config) (
 		return nil, err
 	}
 
-	return sources.NewL1Client(rpc, logger, nil, sources.L1ClientDefaultConfig(cfg.Rollup, cfg.L1TrustRPC, cfg.L1RPCKind))
+	source, err := sources.NewL1Client(rpc, logger, nil, sources.L1ClientDefaultConfig(cfg.Rollup, cfg.L1TrustRPC, cfg.L1RPCKind))
+	if err != nil {
+		return nil, err
+	}
+	oracle := cll1.NewCachingOracle(NewFetchingL1Oracle(ctx, logger, source))
+	return cll1.NewOracleL1Client(logger, oracle, cfg.L1Head), err
 }

op-program/host/l2/fetcher.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/rawdb"
@@ -24,37 +25,50 @@ type CallContext interface {
 type FetchingL2Oracle struct {
 	ctx         context.Context
 	logger      log.Logger
+	head        eth.BlockInfo
 	blockSource BlockSource
 	callContext CallContext
 }
 
-func NewFetchingL2Oracle(ctx context.Context, logger log.Logger, l2Url string) (*FetchingL2Oracle, error) {
+func NewFetchingL2Oracle(ctx context.Context, logger log.Logger, l2Url string, l2Head common.Hash) (*FetchingL2Oracle, error) {
 	rpcClient, err := rpc.Dial(l2Url)
 	if err != nil {
 		return nil, err
 	}
 	ethClient := ethclient.NewClient(rpcClient)
+	head, err := ethClient.HeaderByHash(ctx, l2Head)
+	if err != nil {
+		return nil, fmt.Errorf("retrieve l2 head %v: %w", l2Head, err)
+	}
 	return &FetchingL2Oracle{
 		ctx:         ctx,
 		logger:      logger,
+		head:        eth.HeaderBlockInfo(head),
 		blockSource: ethClient,
 		callContext: rpcClient,
 	}, nil
 }
 
-func (o *FetchingL2Oracle) NodeByHash(hash common.Hash) ([]byte, error) {
+func (o *FetchingL2Oracle) NodeByHash(hash common.Hash) []byte {
 	// MPT nodes are stored as the hash of the node (with no prefix)
-	return o.dbGet(hash.Bytes())
+	node, err := o.dbGet(hash.Bytes())
+	if err != nil {
+		panic(err)
+	}
+	return node
 }
 
-func (o *FetchingL2Oracle) CodeByHash(hash common.Hash) ([]byte, error) {
+func (o *FetchingL2Oracle) CodeByHash(hash common.Hash) []byte {
 	// First try retrieving with the new code prefix
 	code, err := o.dbGet(append(rawdb.CodePrefix, hash.Bytes()...))
 	if err != nil {
 		// Fallback to the legacy un-prefixed version
-		return o.dbGet(hash.Bytes())
+		code, err = o.dbGet(hash.Bytes())
+		if err != nil {
+			panic(err)
+		}
 	}
-	return code, nil
+	return code
 }
 
 func (o *FetchingL2Oracle) dbGet(key []byte) ([]byte, error) {
@@ -66,10 +80,13 @@ func (o *FetchingL2Oracle) dbGet(key []byte) ([]byte, error) {
 	return node, nil
 }
 
-func (o *FetchingL2Oracle) BlockByHash(blockHash common.Hash) (*types.Block, error) {
+func (o *FetchingL2Oracle) BlockByHash(blockHash common.Hash) *types.Block {
 	block, err := o.blockSource.BlockByHash(o.ctx, blockHash)
 	if err != nil {
-		return nil, fmt.Errorf("fetch block %s: %w", blockHash.Hex(), err)
+		panic(fmt.Errorf("fetch block %s: %w", blockHash.Hex(), err))
+	}
+	if block.NumberU64() > o.head.NumberU64() {
+		panic(fmt.Errorf("fetched block %v number %d above head block number %d", blockHash, block.NumberU64(), o.head.NumberU64()))
 	}
-	return block, nil
+	return block
 }

op-program/host/l2/fetcher_test.go

@@ -5,12 +5,14 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"math/big"
 	"math/rand"
 	"reflect"
 	"testing"
 
 	"github.com/ethereum-optimism/optimism/op-node/testutils"
 	cll2 "github.com/ethereum-optimism/optimism/op-program/client/l2"
+	"github.com/ethereum/go-ethereum/trie"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
@@ -23,35 +25,7 @@ import (
 // Require the fetching oracle to implement StateOracle
 var _ cll2.StateOracle = (*FetchingL2Oracle)(nil)
 
-type callContextRequest struct {
-	ctx    context.Context
-	method string
-	args   []interface{}
-}
-type stubCallContext struct {
-	nextResult any
-	nextErr    error
-	requests   []callContextRequest
-}
-
-func (c *stubCallContext) CallContext(ctx context.Context, result any, method string, args ...interface{}) error {
-	if result != nil && reflect.TypeOf(result).Kind() != reflect.Ptr {
-		return fmt.Errorf("call result parameter must be pointer or nil interface: %v", result)
-	}
-	c.requests = append(c.requests, callContextRequest{ctx: ctx, method: method, args: args})
-	if c.nextErr != nil {
-		return c.nextErr
-	}
-	res, err := json.Marshal(c.nextResult)
-	if err != nil {
-		return fmt.Errorf("json marshal: %w", err)
-	}
-	err = json.Unmarshal(res, result)
-	if err != nil {
-		return fmt.Errorf("json unmarshal: %w", err)
-	}
-	return nil
-}
+const headBlockNumber = 1000
 
 func TestNodeByHash(t *testing.T) {
 	rng := rand.New(rand.NewSource(1234))
@@ -63,9 +37,9 @@ func TestNodeByHash(t *testing.T) {
 		}
 		fetcher := newFetcher(nil, stub)
 
-		node, err := fetcher.NodeByHash(hash)
-		require.ErrorIs(t, err, stub.nextErr)
-		require.Nil(t, node)
+		require.Panics(t, func() {
+			fetcher.NodeByHash(hash)
+		})
 	})
 
 	t.Run("Success", func(t *testing.T) {
@@ -75,8 +49,7 @@ func TestNodeByHash(t *testing.T) {
 		}
 		fetcher := newFetcher(nil, stub)
 
-		node, err := fetcher.NodeByHash(hash)
-		require.NoError(t, err)
+		node := fetcher.NodeByHash(hash)
 		require.EqualValues(t, expected, node)
 	})
 
@@ -86,7 +59,7 @@ func TestNodeByHash(t *testing.T) {
 		}
 		fetcher := newFetcher(nil, stub)
 
-		_, _ = fetcher.NodeByHash(hash)
+		fetcher.NodeByHash(hash)
 		require.Len(t, stub.requests, 1, "should make single request")
 		req := stub.requests[0]
 		require.Equal(t, "debug_dbGet", req.method)
@@ -104,9 +77,7 @@ func TestCodeByHash(t *testing.T) {
 		}
 		fetcher := newFetcher(nil, stub)
 
-		node, err := fetcher.CodeByHash(hash)
-		require.ErrorIs(t, err, stub.nextErr)
-		require.Nil(t, node)
+		require.Panics(t, func() { fetcher.CodeByHash(hash) })
 	})
 
 	t.Run("Success", func(t *testing.T) {
@@ -116,8 +87,7 @@ func TestCodeByHash(t *testing.T) {
 		}
 		fetcher := newFetcher(nil, stub)
 
-		node, err := fetcher.CodeByHash(hash)
-		require.NoError(t, err)
+		node := fetcher.CodeByHash(hash)
 		require.EqualValues(t, expected, node)
 	})
 
@@ -127,7 +97,7 @@ func TestCodeByHash(t *testing.T) {
 		}
 		fetcher := newFetcher(nil, stub)
 
-		_, _ = fetcher.CodeByHash(hash)
+		fetcher.CodeByHash(hash)
 		require.Len(t, stub.requests, 1, "should make single request")
 		req := stub.requests[0]
 		require.Equal(t, "debug_dbGet", req.method)
@@ -141,7 +111,8 @@ func TestCodeByHash(t *testing.T) {
 		}
 		fetcher := newFetcher(nil, stub)
 
-		_, _ = fetcher.CodeByHash(hash)
+		// Panics because the code can't be found with or without the prefix
+		require.Panics(t, func() { fetcher.CodeByHash(hash) })
 		require.Len(t, stub.requests, 2, "should request with and without prefix")
 		req := stub.requests[0]
 		require.Equal(t, "debug_dbGet", req.method)
@@ -155,36 +126,16 @@ func TestCodeByHash(t *testing.T) {
 	})
 }
 
-type blockRequest struct {
-	ctx       context.Context
-	blockHash common.Hash
-}
-
-type stubBlockSource struct {
-	requests   []blockRequest
-	nextErr    error
-	nextResult *types.Block
-}
-
-func (s *stubBlockSource) BlockByHash(ctx context.Context, blockHash common.Hash) (*types.Block, error) {
-	s.requests = append(s.requests, blockRequest{
-		ctx:       ctx,
-		blockHash: blockHash,
-	})
-	return s.nextResult, s.nextErr
-}
-
 func TestBlockByHash(t *testing.T) {
 	rng := rand.New(rand.NewSource(1234))
 	hash := testutils.RandomHash(rng)
 
 	t.Run("Success", func(t *testing.T) {
-		block, _ := testutils.RandomBlock(rng, 1)
+		block := blockWithNumber(rng, headBlockNumber-1)
 		stub := &stubBlockSource{nextResult: block}
 		fetcher := newFetcher(stub, nil)
 
-		res, err := fetcher.BlockByHash(hash)
-		require.NoError(t, err)
+		res := fetcher.BlockByHash(hash)
 		require.Same(t, block, res)
 	})
 
@@ -192,26 +143,101 @@ func TestBlockByHash(t *testing.T) {
 		stub := &stubBlockSource{nextErr: errors.New("boom")}
 		fetcher := newFetcher(stub, nil)
 
-		res, err := fetcher.BlockByHash(hash)
-		require.ErrorIs(t, err, stub.nextErr)
-		require.Nil(t, res)
+		require.Panics(t, func() {
+			fetcher.BlockByHash(hash)
+		})
 	})
 
 	t.Run("RequestArgs", func(t *testing.T) {
-		stub := &stubBlockSource{}
+		stub := &stubBlockSource{nextResult: blockWithNumber(rng, 1)}
 		fetcher := newFetcher(stub, nil)
 
-		_, _ = fetcher.BlockByHash(hash)
+		fetcher.BlockByHash(hash)
 
 		require.Len(t, stub.requests, 1, "should make single request")
 		req := stub.requests[0]
 		require.Equal(t, hash, req.blockHash)
 	})
+
+	t.Run("PanicWhenBlockAboveHeadRequested", func(t *testing.T) {
+		// Block that the source can provide but is above the head block number
+		block := blockWithNumber(rng, headBlockNumber+1)
+
+		stub := &stubBlockSource{nextResult: block}
+		fetcher := newFetcher(stub, nil)
+
+		require.Panics(t, func() {
+			fetcher.BlockByHash(block.Hash())
+		})
+	})
+}
+
+func blockWithNumber(rng *rand.Rand, num int64) *types.Block {
+	header := testutils.RandomHeader(rng)
+	header.Number = big.NewInt(num)
+	return types.NewBlock(header, nil, nil, nil, trie.NewStackTrie(nil))
+}
+
+type blockRequest struct {
+	ctx       context.Context
+	blockHash common.Hash
+}
+
+type stubBlockSource struct {
+	requests   []blockRequest
+	nextErr    error
+	nextResult *types.Block
+}
+
+func (s *stubBlockSource) BlockByHash(ctx context.Context, blockHash common.Hash) (*types.Block, error) {
+	s.requests = append(s.requests, blockRequest{
+		ctx:       ctx,
+		blockHash: blockHash,
+	})
+	return s.nextResult, s.nextErr
+}
+
+type callContextRequest struct {
+	ctx    context.Context
+	method string
+	args   []interface{}
+}
+
+type stubCallContext struct {
+	nextResult any
+	nextErr    error
+	requests   []callContextRequest
+}
+
+func (c *stubCallContext) CallContext(ctx context.Context, result any, method string, args ...interface{}) error {
+	if result != nil && reflect.TypeOf(result).Kind() != reflect.Ptr {
+		return fmt.Errorf("call result parameter must be pointer or nil interface: %v", result)
+	}
+	c.requests = append(c.requests, callContextRequest{ctx: ctx, method: method, args: args})
+	if c.nextErr != nil {
+		return c.nextErr
+	}
+	res, err := json.Marshal(c.nextResult)
+	if err != nil {
+		return fmt.Errorf("json marshal: %w", err)
+	}
+	err = json.Unmarshal(res, result)
+	if err != nil {
+		return fmt.Errorf("json unmarshal: %w", err)
+	}
+	return nil
 }
 
 func newFetcher(blockSource BlockSource, callContext CallContext) *FetchingL2Oracle {
+	rng := rand.New(rand.NewSource(int64(1)))
+	head := testutils.MakeBlockInfo(func(i *testutils.MockBlockInfo) {
+		i.InfoNum = headBlockNumber
+	})(rng)
+
 	return &FetchingL2Oracle{
+		ctx:         context.Background(),
 		logger:      log.New(),
+		head:        head,
 		blockSource: blockSource,
 		callContext: callContext,
 	}

op-program/host/l2/l2.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"os"
 
-	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
 	cll2 "github.com/ethereum-optimism/optimism/op-program/client/l2"
 	"github.com/ethereum-optimism/optimism/op-program/host/config"
 	"github.com/ethereum/go-ethereum/core"
@@ -14,15 +13,16 @@ import (
 	"github.com/ethereum/go-ethereum/params"
 )
 
-func NewFetchingEngine(ctx context.Context, logger log.Logger, cfg *config.Config) (derive.Engine, error) {
+func NewFetchingEngine(ctx context.Context, logger log.Logger, cfg *config.Config) (*cll2.OracleEngine, error) {
 	genesis, err := loadL2Genesis(cfg)
 	if err != nil {
 		return nil, err
 	}
-	oracle, err := NewFetchingL2Oracle(ctx, logger, cfg.L2URL)
+	fetcher, err := NewFetchingL2Oracle(ctx, logger, cfg.L2URL, cfg.L2Head)
 	if err != nil {
 		return nil, fmt.Errorf("connect l2 oracle: %w", err)
 	}
+	oracle := cll2.NewCachingOracle(fetcher)
 
 	engineBackend, err := cll2.NewOracleBackedL2Chain(logger, oracle, genesis, cfg.L2Head)
 	if err != nil {

op-program/preimage/hints.go

+package preimage
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+)
+
+// HintWriter writes hints to an io.Writer (e.g. a special file descriptor, or a debug log),
+// for a pre-image oracle service to prepare specific pre-images.
+type HintWriter struct {
+	w io.Writer
+}
+
+var _ Hinter = (*HintWriter)(nil)
+
+func NewHintWriter(w io.Writer) *HintWriter {
+	return &HintWriter{w: w}
+}
+
+func (hw *HintWriter) Hint(v Hint) {
+	hint := v.Hint()
+	var hintBytes []byte
+	hintBytes = binary.BigEndian.AppendUint32(hintBytes, uint32(len(hint)))
+	hintBytes = append(hintBytes, []byte(hint)...)
+	hintBytes = append(hintBytes, 0) // to block writing on
+	_, err := hw.w.Write(hintBytes)
+	if err != nil {
+		panic(fmt.Errorf("failed to write pre-image hint: %w", err))
+	}
+}
+
+// HintReader reads the hints of HintWriter and passes them to a router for preparation of the requested pre-images.
+// Onchain the written hints are no-op.
+type HintReader struct {
+	r io.Reader
+}
+
+func NewHintReader(r io.Reader) *HintReader {
+	return &HintReader{r: r}
+}
+
+func (hr *HintReader) NextHint(router func(hint string) error) error {
+	var length uint32
+	if err := binary.Read(hr.r, binary.BigEndian, &length); err != nil {
+		if err == io.EOF {
+			return io.EOF
+		}
+		return fmt.Errorf("failed to read hint length prefix: %w", err)
+	}
+	payload := make([]byte, length)
+	if length > 0 {
+		if _, err := io.ReadFull(hr.r, payload); err != nil {
+			return fmt.Errorf("failed to read hint payload (length %d): %w", length, err)
+		}
+	}
+	if err := router(string(payload)); err != nil {
+		return fmt.Errorf("failed to handle hint: %w", err)
+	}
+	if _, err := hr.r.Read([]byte{0}); err != nil {
+		return fmt.Errorf("failed to read trailing no-op byte to unblock hint writer: %w", err)
+	}
+	return nil
+}

op-program/preimage/hints_test.go

+package preimage
+
+import (
+	"bytes"
+	"crypto/rand"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+type rawHint string
+
+func (rh rawHint) Hint() string {
+	return string(rh)
+}
+
+func TestHints(t *testing.T) {
+	// Note: pretty much every string is valid communication:
+	// length, payload, 0. Worst case you run out of data, or allocate too much.
+	testHint := func(hints ...string) {
+		var buf bytes.Buffer
+		hw := NewHintWriter(&buf)
+		for _, h := range hints {
+			hw.Hint(rawHint(h))
+		}
+		hr := NewHintReader(&buf)
+		var got []string
+		for i := 0; i < 100; i++ { // sanity limit
+			err := hr.NextHint(func(hint string) error {
+				got = append(got, hint)
+				return nil
+			})
+			if err == io.EOF {
+				break
+			}
+			require.NoError(t, err)
+		}
+		require.Equal(t, len(hints), len(got), "got all hints")
+		for i, h := range hints {
+			require.Equal(t, h, got[i], "hints match")
+		}
+	}
+
+	t.Run("empty hint", func(t *testing.T) {
+		testHint("")
+	})
+	t.Run("hello world", func(t *testing.T) {
+		testHint("hello world")
+	})
+	t.Run("zero byte", func(t *testing.T) {
+		testHint(string([]byte{0}))
+	})
+	t.Run("many zeroes", func(t *testing.T) {
+		testHint(string(make([]byte, 1000)))
+	})
+	t.Run("random data", func(t *testing.T) {
+		dat := make([]byte, 1000)
+		_, _ = rand.Read(dat[:])
+		testHint(string(dat))
+	})
+	t.Run("multiple hints", func(t *testing.T) {
+		testHint("give me header a", "also header b", "foo bar")
+	})
+	t.Run("unexpected EOF", func(t *testing.T) {
+		var buf bytes.Buffer
+		hw := NewHintWriter(&buf)
+		hw.Hint(rawHint("hello"))
+		_, _ = buf.Read(make([]byte, 1)) // read one byte so it falls short, see if it's detected
+		hr := NewHintReader(&buf)
+		err := hr.NextHint(func(hint string) error { return nil })
+		require.ErrorIs(t, err, io.ErrUnexpectedEOF)
+	})
+}

op-program/preimage/iface.go

+package preimage
+
+import (
+	"encoding/binary"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+type Key interface {
+	// PreimageKey changes the Key commitment into a
+	// 32-byte type-prefixed preimage key.
+	PreimageKey() common.Hash
+}
+
+type Oracle interface {
+	// Get the full pre-image of a given pre-image key.
+	// This returns no error: the client state-transition
+	// is invalid if there is any missing pre-image data.
+	Get(key Key) []byte
+}
+
+type OracleFn func(key Key) []byte
+
+func (fn OracleFn) Get(key Key) []byte {
+	return fn(key)
+}
+
+// KeyType is the key-type of a pre-image, used to prefix the pre-image key with.
+type KeyType byte
+
+const (
+	// The zero key type is illegal to use, ensuring all keys are non-zero.
+	_ KeyType = 0
+	// LocalKeyType is for input-type pre-images, specific to the local program instance.
+	LocalKeyType KeyType = 1
+	// Keccak25Key6Type is for keccak256 pre-images, for any global shared pre-images.
+	Keccak25Key6Type KeyType = 2
+)
+
+// LocalIndexKey is a key local to the program, indexing a special program input.
+type LocalIndexKey uint64
+
+func (k LocalIndexKey) PreimageKey() (out common.Hash) {
+	out[0] = byte(LocalKeyType)
+	binary.BigEndian.PutUint64(out[24:], uint64(k))
+	return
+}
+
+// Keccak256Key wraps a keccak256 hash to use it as a typed pre-image key.
+type Keccak256Key common.Hash
+
+func (k Keccak256Key) PreimageKey() (out common.Hash) {
+	out = common.Hash(k)            // copy the keccak hash
+	out[0] = byte(Keccak25Key6Type) // apply prefix
+	return
+}
+
+// Hint is an interface to enable any program type to function as a hint,
+// when passed to the Hinter interface, returning a string representation
+// of what data the host should prepare pre-images for.
+type Hint interface {
+	Hint() string
+}
+
+// Hinter is an interface to write hints to the host.
+// This may be implemented as a no-op or logging hinter
+// if the program is executing in a read-only environment
+// where the host is expected to have all pre-images ready.
+type Hinter interface {
+	Hint(v Hint)
+}
+
+type HinterFn func(v Hint)
+
+func (fn HinterFn) Hint(v Hint) {
+	fn(v)
+}

op-program/preimage/oracle.go

+package preimage
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// OracleClient implements the Oracle by writing the pre-image key to the given stream,
+// and reading back a length-prefixed value.
+type OracleClient struct {
+	rw io.ReadWriter
+}
+
+func NewOracleClient(rw io.ReadWriter) *OracleClient {
+	return &OracleClient{rw: rw}
+}
+
+var _ Oracle = (*OracleClient)(nil)
+
+func (o *OracleClient) Get(key Key) []byte {
+	h := key.PreimageKey()
+	if _, err := o.rw.Write(h[:]); err != nil {
+		panic(fmt.Errorf("failed to write key %s (%T) to pre-image oracle: %w", key, key, err))
+	}
+
+	var length uint64
+	if err := binary.Read(o.rw, binary.BigEndian, &length); err != nil {
+		panic(fmt.Errorf("failed to read pre-image length of key %s (%T) from pre-image oracle: %w", key, key, err))
+	}
+	payload := make([]byte, length)
+	if _, err := io.ReadFull(o.rw, payload); err != nil {
+		panic(fmt.Errorf("failed to read pre-image payload (length %d) of key %s (%T) from pre-image oracle: %w", length, key, key, err))
+	}
+
+	return payload
+}
+
+// OracleServer serves the pre-image requests of the OracleClient, implementing the same protocol as the onchain VM.
+type OracleServer struct {
+	rw io.ReadWriter
+}
+
+func NewOracleServer(rw io.ReadWriter) *OracleServer {
+	return &OracleServer{rw: rw}
+}
+
+func (o *OracleServer) NextPreimageRequest(getPreimage func(key common.Hash) ([]byte, error)) error {
+	var key common.Hash
+	if _, err := io.ReadFull(o.rw, key[:]); err != nil {
+		if err == io.EOF {
+			return io.EOF
+		}
+		return fmt.Errorf("failed to read requested pre-image key: %w", err)
+	}
+	value, err := getPreimage(key)
+	if err != nil {
+		return fmt.Errorf("failed to serve pre-image %s request: %w", key, err)
+	}
+
+	if err := binary.Write(o.rw, binary.BigEndian, uint64(len(value))); err != nil {
+		return fmt.Errorf("failed to write length-prefix %d: %w", len(value), err)
+	}
+	if len(value) == 0 {
+		return nil
+	}
+	if _, err := o.rw.Write(value); err != nil {
+		return fmt.Errorf("failed to write pre-image value (%d long): %w", len(value), err)
+	}
+	return nil
+}

op-program/preimage/oracle_test.go

+package preimage
+
+import (
+	"bytes"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"sync"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/stretchr/testify/require"
+)
+
+type readWritePair struct {
+	io.Reader
+	io.Writer
+}
+
+func bidirectionalPipe() (a, b io.ReadWriter) {
+	ar, bw := io.Pipe()
+	br, aw := io.Pipe()
+	return readWritePair{Reader: ar, Writer: aw}, readWritePair{Reader: br, Writer: bw}
+}
+
+func TestOracle(t *testing.T) {
+	testPreimage := func(preimages ...[]byte) {
+		a, b := bidirectionalPipe()
+		cl := NewOracleClient(a)
+		srv := NewOracleServer(b)
+
+		preimageByHash := make(map[common.Hash][]byte)
+		for _, p := range preimages {
+			k := Keccak256Key(crypto.Keccak256Hash(p))
+			preimageByHash[k.PreimageKey()] = p
+		}
+		for _, p := range preimages {
+			k := Keccak256Key(crypto.Keccak256Hash(p))
+
+			var wg sync.WaitGroup
+			wg.Add(2)
+
+			go func(k Key, p []byte) {
+				result := cl.Get(k)
+				wg.Done()
+				expected := preimageByHash[k.PreimageKey()]
+				require.True(t, bytes.Equal(expected, result), "need correct preimage %x, got %x", expected, result)
+			}(k, p)
+
+			go func() {
+				err := srv.NextPreimageRequest(func(key common.Hash) ([]byte, error) {
+					dat, ok := preimageByHash[key]
+					if !ok {
+						return nil, fmt.Errorf("cannot find %s", key)
+					}
+					return dat, nil
+				})
+				wg.Done()
+				require.NoError(t, err)
+			}()
+			wg.Wait()
+		}
+	}
+	t.Run("empty preimage", func(t *testing.T) {
+		testPreimage([]byte{})
+	})
+	t.Run("nil preimage", func(t *testing.T) {
+		testPreimage(nil)
+	})
+	t.Run("zero", func(t *testing.T) {
+		testPreimage([]byte{0})
+	})
+	t.Run("multiple", func(t *testing.T) {
+		testPreimage([]byte("tx from alice"), []byte{0x13, 0x37}, []byte("tx from bob"))
+	})
+	t.Run("zeroes", func(t *testing.T) {
+		testPreimage(make([]byte, 1000))
+	})
+	t.Run("random", func(t *testing.T) {
+		dat := make([]byte, 1000)
+		_, _ = rand.Read(dat[:])
+		testPreimage(dat)
+	})
+}

op-proposer/cmd/doc/cmd.go

+package doc
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/ethereum-optimism/optimism/op-proposer/metrics"
+	"github.com/olekukonko/tablewriter"
+	"github.com/urfave/cli"
+)
+
+var Subcommands = cli.Commands{
+	{
+		Name:  "metrics",
+		Usage: "Dumps a list of supported metrics to stdout",
+		Flags: []cli.Flag{
+			cli.StringFlag{
+				Name:  "format",
+				Value: "markdown",
+				Usage: "Output format (json|markdown)",
+			},
+		},
+		Action: func(ctx *cli.Context) error {
+			m := metrics.NewMetrics("default")
+			supportedMetrics := m.Document()
+			format := ctx.String("format")
+
+			if format != "markdown" && format != "json" {
+				return fmt.Errorf("invalid format: %s", format)
+			}
+
+			if format == "json" {
+				enc := json.NewEncoder(os.Stdout)
+				return enc.Encode(supportedMetrics)
+			}
+
+			table := tablewriter.NewWriter(os.Stdout)
+			table.SetBorders(tablewriter.Border{Left: true, Top: false, Right: true, Bottom: false})
+			table.SetCenterSeparator("|")
+			table.SetAutoWrapText(false)
+			table.SetHeader([]string{"Metric", "Description", "Labels", "Type"})
+			var data [][]string
+			for _, metric := range supportedMetrics {
+				labels := strings.Join(metric.Labels, ",")
+				data = append(data, []string{metric.Name, metric.Help, labels, metric.Type})
+			}
+			table.AppendBulk(data)
+			table.Render()
+			return nil
+		},
+	},
+}

op-proposer/cmd/main.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/urfave/cli"
 
+	"github.com/ethereum-optimism/optimism/op-proposer/cmd/doc"
 	"github.com/ethereum-optimism/optimism/op-proposer/flags"
 	"github.com/ethereum-optimism/optimism/op-proposer/proposer"
 	oplog "github.com/ethereum-optimism/optimism/op-service/log"
@@ -27,8 +28,14 @@ func main() {
 	app.Name = "op-proposer"
 	app.Usage = "L2Output Submitter"
 	app.Description = "Service for generating and submitting L2 Output checkpoints to the L2OutputOracle contract"
-
 	app.Action = curryMain(Version)
+	app.Commands = []cli.Command{
+		{
+			Name:        "doc",
+			Subcommands: doc.Subcommands,
+		},
+	}
+
 	err := app.Run(os.Args)
 	if err != nil {
 		log.Crit("Application failed", "message", err)

op-proposer/flags/flags.go

 package flags
 
 import (
+	"fmt"
+
 	"github.com/urfave/cli"
 
 	opservice "github.com/ethereum-optimism/optimism/op-service"
@@ -18,26 +20,22 @@ var (
 	L1EthRpcFlag = cli.StringFlag{
 		Name:   "l1-eth-rpc",
 		Usage:  "HTTP provider URL for L1",
-		Required: true,
 		EnvVar: opservice.PrefixEnvVar(envVarPrefix, "L1_ETH_RPC"),
 	}
 	RollupRpcFlag = cli.StringFlag{
 		Name:   "rollup-rpc",
 		Usage:  "HTTP provider URL for the rollup node",
-		Required: true,
 		EnvVar: opservice.PrefixEnvVar(envVarPrefix, "ROLLUP_RPC"),
 	}
 	L2OOAddressFlag = cli.StringFlag{
 		Name:   "l2oo-address",
 		Usage:  "Address of the L2OutputOracle contract",
-		Required: true,
 		EnvVar: opservice.PrefixEnvVar(envVarPrefix, "L2OO_ADDRESS"),
 	}
 	PollIntervalFlag = cli.DurationFlag{
 		Name: "poll-interval",
 		Usage: "Delay between querying L2 for more transactions and " +
 			"creating a new batch",
-		Required: true,
 		EnvVar: opservice.PrefixEnvVar(envVarPrefix, "POLL_INTERVAL"),
 	}
 	// Optional flags
@@ -74,3 +72,12 @@ func init() {
 
 // Flags contains the list of configuration options available to the binary.
 var Flags []cli.Flag
+
+func CheckRequired(ctx *cli.Context) error {
+	for _, f := range requiredFlags {
+		if !ctx.GlobalIsSet(f.GetName()) {
+			return fmt.Errorf("flag %s is required", f.GetName())
+		}
+	}
+	return nil
+}

op-proposer/metrics/metrics.go

@@ -104,3 +104,7 @@ const (
 func (m *Metrics) RecordL2BlocksProposed(l2ref eth.L2BlockRef) {
 	m.RecordL2Ref(BlockProposed, l2ref)
 }
+
+func (m *Metrics) Document() []opmetrics.DocumentedMetric {
+	return m.factory.Document()
+}

op-proposer/proposer/l2_output_submitter.go

@@ -15,6 +15,7 @@ import (
 	"github.com/ethereum/go-ethereum/accounts/abi"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/urfave/cli"
 
@@ -334,7 +335,11 @@ func (l *L2OutputSubmitter) sendTransaction(ctx context.Context, output *eth.Out
 	if err != nil {
 		return err
 	}
+	if receipt.Status == types.ReceiptStatusFailed {
+		l.log.Error("proposer tx successfully published but reverted", "tx_hash", receipt.TxHash)
+	} else {
 		l.log.Info("proposer tx successfully published", "tx_hash", receipt.TxHash)
+	}
 	return nil
 }
 

op-service/metrics/event.go

@@ -16,17 +16,19 @@ func (e *Event) Record() {
 	e.LastTime.SetToCurrentTime()
 }
 
-func NewEvent(factory Factory, ns string, name string, displayName string) Event {
+func NewEvent(factory Factory, ns string, subsystem string, name string, displayName string) Event {
 	return Event{
 		Total: factory.NewCounter(prometheus.CounterOpts{
 			Namespace: ns,
 			Name:      fmt.Sprintf("%s_total", name),
 			Help:      fmt.Sprintf("Count of %s events", displayName),
+			Subsystem: subsystem,
 		}),
 		LastTime: factory.NewGauge(prometheus.GaugeOpts{
 			Namespace: ns,
 			Name:      fmt.Sprintf("last_%s_unix", name),
 			Help:      fmt.Sprintf("Timestamp of last %s event", displayName),
+			Subsystem: subsystem,
 		}),
 	}
 }
@@ -41,17 +43,19 @@ func (e *EventVec) Record(lvs ...string) {
 	e.LastTime.WithLabelValues(lvs...).SetToCurrentTime()
 }
 
-func NewEventVec(factory Factory, ns string, name string, displayName string, labelNames []string) EventVec {
+func NewEventVec(factory Factory, ns string, subsystem string, name string, displayName string, labelNames []string) EventVec {
 	return EventVec{
 		Total: *factory.NewCounterVec(prometheus.CounterOpts{
 			Namespace: ns,
 			Name:      fmt.Sprintf("%s_total", name),
 			Help:      fmt.Sprintf("Count of %s events", displayName),
+			Subsystem: subsystem,
 		}, labelNames),
 		LastTime: *factory.NewGaugeVec(prometheus.GaugeOpts{
 			Namespace: ns,
 			Name:      fmt.Sprintf("last_%s_unix", name),
 			Help:      fmt.Sprintf("Timestamp of last %s event", displayName),
+			Subsystem: subsystem,
 		}, labelNames),
 	}
 }

op-service/txmgr/metrics/tx_metrics.go

@@ -85,15 +85,15 @@ func MakeTxMetrics(ns string, factory metrics.Factory) TxMetrics {
 		txPublishError: factory.NewCounterVec(prometheus.CounterOpts{
 			Namespace: ns,
 			Name:      "tx_publish_error_count",
-			Help:      "Count of publish errors. Labells are sanitized error strings",
+			Help:      "Count of publish errors. Labels are sanitized error strings",
 			Subsystem: "txmgr",
 		}, []string{"error"}),
-		confirmEvent: metrics.NewEventVec(factory, ns, "confirm", "tx confirm", []string{"status"}),
-		publishEvent: metrics.NewEvent(factory, ns, "publish", "tx publish"),
+		confirmEvent: metrics.NewEventVec(factory, ns, "txmgr", "confirm", "tx confirm", []string{"status"}),
+		publishEvent: metrics.NewEvent(factory, ns, "txmgr", "publish", "tx publish"),
 		rpcError: factory.NewCounter(prometheus.CounterOpts{
 			Namespace: ns,
 			Name:      "rpc_error_count",
-			Help:      "Temporrary: Count of RPC errors (like timeouts) that have occurrred",
+			Help:      "Temporary: Count of RPC errors (like timeouts) that have occurred",
 			Subsystem: "txmgr",
 		}),
 	}

op-service/txmgr/txmgr.go

@@ -67,10 +67,10 @@ type ETHBackend interface {
 	// NonceAt returns the account nonce of the given account.
 	// The block number can be nil, in which case the nonce is taken from the latest known block.
 	NonceAt(ctx context.Context, account common.Address, blockNumber *big.Int) (uint64, error)
-	// PendingNonce returns the pending nonce.
+	// PendingNonceAt returns the pending nonce.
 	PendingNonceAt(ctx context.Context, account common.Address) (uint64, error)
-	/// EstimateGas returns an estimate of the amount of gas needed to execute the given
-	/// transaction against the current pending block.
+	// EstimateGas returns an estimate of the amount of gas needed to execute the given
+	// transaction against the current pending block.
 	EstimateGas(ctx context.Context, msg ethereum.CallMsg) (uint64, error)
 }
 

packages/contracts-bedrock/contracts/L1/SystemConfig.sol

@@ -80,7 +80,7 @@ contract SystemConfig is OwnableUpgradeable, Semver {
     event ConfigUpdate(uint256 indexed version, UpdateType indexed updateType, bytes data);
 
     /**
-     * @custom:semver 1.2.0
+     * @custom:semver 1.3.0
      *
      * @param _owner             Initial owner of the contract.
      * @param _overhead          Initial overhead value.
@@ -98,7 +98,7 @@ contract SystemConfig is OwnableUpgradeable, Semver {
         uint64 _gasLimit,
         address _unsafeBlockSigner,
         ResourceMetering.ResourceConfig memory _config
-    ) Semver(1, 2, 0) {
+    ) Semver(1, 3, 0) {
         initialize({
             _owner: _owner,
             _overhead: _overhead,
@@ -269,8 +269,11 @@ contract SystemConfig is OwnableUpgradeable, Semver {
             _config.minimumBaseFee <= _config.maximumBaseFee,
             "SystemConfig: min base fee must be less than max base"
         );
-        // Base fee change denominator must be greater than 0.
-        require(_config.baseFeeMaxChangeDenominator > 0, "SystemConfig: denominator cannot be 0");
+        // Base fee change denominator must be greater than 1.
+        require(
+            _config.baseFeeMaxChangeDenominator > 1,
+            "SystemConfig: denominator must be larger than 1"
+        );
         // Max resource limit plus system tx gas must be less than or equal to the L2 gas limit.
         // The gas limit must be increased before these values can be increased.
         require(

packages/contracts-bedrock/contracts/test/SystemConfig.t.sol

@@ -110,7 +110,7 @@ contract SystemConfig_Setters_TestFail is SystemConfig_Init {
             maximumBaseFee: 2 gwei
         });
         vm.prank(sysConf.owner());
-        vm.expectRevert("SystemConfig: denominator cannot be 0");
+        vm.expectRevert("SystemConfig: denominator must be larger than 1");
         sysConf.setResourceConfig(config);
     }
 

specs/proposals.md

@@ -207,7 +207,7 @@ function deleteL2Outputs(uint256 _l2OutputIndex) external
 /**
  * @notice Computes the block number of the next L2 block that needs to be checkpointed.
  */
-function getNextBlockNumber() public view returns (uint256)
+function nextBlockNumber() public view returns (uint256)
 ```
 
 ### Configuration