Fjord: Implement max sequencer drift change to a constant (#10465)

* op-node/rollup: Add MaxSequencerDrift to ChainSpec

* op-node/rollup,op-e2e: Use spec max seq drift instead of config

* op-node/rollup: Showcase feature/fork separation pattern with seq drift change

* op-node/driver: add origin selector Fjord test

* op-node/rollup: refactor batch validation test

prepare to allow for general modification of rollup config

* op-node/rollup: add batch validation test

* Update op-node/rollup/types.go
Co-authored-by: Joshua Gutow <jgutow@oplabs.co>

* op-node/rollup/derive: add Fjord span batch validation test

---------
Co-authored-by: Joshua Gutow <jgutow@oplabs.co>

op-e2e/actions/l2_sequencer_test.go

@@ -111,7 +111,7 @@ func TestL2Sequencer_SequencerDrift(gt *testing.T) {
 	sequencer.ActL1HeadSignal(t)
 
 	// Make blocks up till the sequencer drift is about to surpass, but keep the old L1 origin
-	for sequencer.SyncStatus().UnsafeL2.Time+sd.RollupCfg.BlockTime <= origin.Time+sd.RollupCfg.MaxSequencerDrift {
+	for sequencer.SyncStatus().UnsafeL2.Time+sd.RollupCfg.BlockTime <= origin.Time+sd.ChainSpec.MaxSequencerDrift(origin.Time) {
 		sequencer.ActL2KeepL1Origin(t)
 		makeL2BlockWithAliceTx()
 		require.Equal(t, uint64(1), sequencer.SyncStatus().UnsafeL2.L1Origin.Number, "expected to keep old L1 origin")

op-e2e/e2eutils/setup.go

@@ -80,6 +80,7 @@ type SetupData struct {
 	L1Cfg         *core.Genesis
 	L2Cfg         *core.Genesis
 	RollupCfg     *rollup.Config
+	ChainSpec     *rollup.ChainSpec
 	DeploymentsL1 *genesis.L1Deployments
 }
 
@@ -187,6 +188,7 @@ func Setup(t require.TestingT, deployParams *DeployParams, alloc *AllocParams) *
 		L1Cfg:         l1Genesis,
 		L2Cfg:         l2Genesis,
 		RollupCfg:     rollupCfg,
+		ChainSpec:     rollup.NewChainSpec(rollupCfg),
 		DeploymentsL1: l1Deployments,
 	}
 }

op-node/rollup/chain_spec.go

@@ -20,6 +20,12 @@ const (
 // TODO(#10428) Remove this parameter
 const SafeMaxRLPBytesPerChannel = maxRLPBytesPerChannelBedrock
 
+// Fjord changes the max sequencer drift to a protocol constant. It was previously configurable via
+// the rollup config.
+// From Fjord, the max sequencer drift for a given block timestamp should be learned via the
+// ChainSpec instead of reading the rollup configuration field directly.
+const maxSequencerDriftFjord = 1800
+
 type ChainSpec struct {
 	config *Config
 }
@@ -55,3 +61,19 @@ func (s *ChainSpec) MaxRLPBytesPerChannel(t uint64) uint64 {
 	}
 	return maxRLPBytesPerChannelBedrock
 }
+
+// IsFeatMaxSequencerDriftConstant specifies in which fork the max sequencer drift change to a
+// constant will be performed.
+func (s *ChainSpec) IsFeatMaxSequencerDriftConstant(t uint64) bool {
+	return s.config.IsFjord(t)
+}
+
+// MaxSequencerDrift returns the maximum sequencer drift for the given block timestamp. Until Fjord,
+// this was a rollup configuration parameter. Since Fjord, it is a constant, so its effective value
+// should always be queried via the ChainSpec.
+func (s *ChainSpec) MaxSequencerDrift(t uint64) uint64 {
+	if s.IsFeatMaxSequencerDriftConstant(t) {
+		return maxSequencerDriftFjord
+	}
+	return s.config.MaxSequencerDrift
+}

op-node/rollup/chain_spec_test.go

@@ -50,7 +50,7 @@ var testConfig = Config{
 	UsePlasma:               false,
 }
 
-func TestCanyonForkActivation(t *testing.T) {
+func TestChainSpec_CanyonForkActivation(t *testing.T) {
 	c := NewChainSpec(&testConfig)
 	tests := []struct {
 		name     string
@@ -74,7 +74,7 @@ func TestCanyonForkActivation(t *testing.T) {
 	}
 }
 
-func TestMaxChannelBankSize(t *testing.T) {
+func TestChainSpec_MaxChannelBankSize(t *testing.T) {
 	c := NewChainSpec(&testConfig)
 	tests := []struct {
 		name        string
@@ -97,7 +97,7 @@ func TestMaxChannelBankSize(t *testing.T) {
 	}
 }
 
-func TestMaxRLPBytesPerChannel(t *testing.T) {
+func TestChainSpec_MaxRLPBytesPerChannel(t *testing.T) {
 	c := NewChainSpec(&testConfig)
 	tests := []struct {
 		name        string
@@ -119,3 +119,26 @@ func TestMaxRLPBytesPerChannel(t *testing.T) {
 		})
 	}
 }
+
+func TestChainSpec_MaxSequencerDrift(t *testing.T) {
+	c := NewChainSpec(&testConfig)
+	tests := []struct {
+		name        string
+		blockNum    uint64
+		expected    uint64
+		description string
+	}{
+		{"Genesis", 0, testConfig.MaxSequencerDrift, "Before Fjord activation, should use rollup config value"},
+		{"FjordTimeMinusOne", 49, testConfig.MaxSequencerDrift, "Just before Fjord, should still use rollup config value"},
+		{"FjordTime", 50, maxSequencerDriftFjord, "At Fjord activation, should switch to Fjord constant"},
+		{"FjordTimePlusOne", 51, maxSequencerDriftFjord, "After Fjord activation, should use Fjord constant"},
+		{"NextForkTime", 60, maxSequencerDriftFjord, "Well after Fjord, should continue to use Fjord constant"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := c.MaxSequencerDrift(tt.blockNum)
+			require.Equal(t, tt.expected, result, tt.description)
+		})
+	}
+}

op-node/rollup/derive/batches.go

@@ -32,7 +32,8 @@ const (
 // The first entry of the l1Blocks should match the origin of the l2SafeHead. One or more consecutive l1Blocks should be provided.
 // In case of only a single L1 block, the decision whether a batch is valid may have to stay undecided.
 func CheckBatch(ctx context.Context, cfg *rollup.Config, log log.Logger, l1Blocks []eth.L1BlockRef,
-	l2SafeHead eth.L2BlockRef, batch *BatchWithL1InclusionBlock, l2Fetcher SafeBlockFetcher) BatchValidity {
+	l2SafeHead eth.L2BlockRef, batch *BatchWithL1InclusionBlock, l2Fetcher SafeBlockFetcher,
+) BatchValidity {
 	switch batch.Batch.GetBatchType() {
 	case SingularBatchType:
 		singularBatch, ok := batch.Batch.(*SingularBatch)
@@ -122,8 +123,9 @@ func checkSingularBatch(cfg *rollup.Config, log log.Logger, l1Blocks []eth.L1Blo
 		return BatchDrop
 	}
 
+	spec := rollup.NewChainSpec(cfg)
 	// Check if we ran out of sequencer time drift
-	if max := batchOrigin.Time + cfg.MaxSequencerDrift; batch.Timestamp > max {
+	if max := batchOrigin.Time + spec.MaxSequencerDrift(batchOrigin.Time); batch.Timestamp > max {
 		if len(batch.Transactions) == 0 {
 			// If the sequencer is co-operating by producing an empty batch,
 			// then allow the batch if it was the right thing to do to maintain the L2 time >= L1 time invariant.
@@ -166,7 +168,8 @@ func checkSingularBatch(cfg *rollup.Config, log log.Logger, l1Blocks []eth.L1Blo
 
 // checkSpanBatch implements SpanBatch validation rule.
 func checkSpanBatch(ctx context.Context, cfg *rollup.Config, log log.Logger, l1Blocks []eth.L1BlockRef, l2SafeHead eth.L2BlockRef,
-	batch *SpanBatch, l1InclusionBlock eth.L1BlockRef, l2Fetcher SafeBlockFetcher) BatchValidity {
+	batch *SpanBatch, l1InclusionBlock eth.L1BlockRef, l2Fetcher SafeBlockFetcher,
+) BatchValidity {
 	// add details to the log
 	log = batch.LogContext(log)
 
@@ -266,10 +269,7 @@ func checkSpanBatch(ctx context.Context, cfg *rollup.Config, log log.Logger, l1B
 	}
 
 	originIdx := 0
-	originAdvanced := false
-	if startEpochNum == parentBlock.L1Origin.Number+1 {
-		originAdvanced = true
-	}
+	originAdvanced := startEpochNum == parentBlock.L1Origin.Number+1
 
 	for i := 0; i < batch.GetBlockCount(); i++ {
 		if batch.GetBlockTimestamp(i) <= l2SafeHead.Time {
@@ -282,7 +282,6 @@ func checkSpanBatch(ctx context.Context, cfg *rollup.Config, log log.Logger, l1B
 				originIdx = j
 				break
 			}
-
 		}
 		if i > 0 {
 			originAdvanced = false
@@ -296,8 +295,9 @@ func checkSpanBatch(ctx context.Context, cfg *rollup.Config, log log.Logger, l1B
 			return BatchDrop
 		}
 
+		spec := rollup.NewChainSpec(cfg)
 		// Check if we ran out of sequencer time drift
-		if max := l1Origin.Time + cfg.MaxSequencerDrift; blockTimestamp > max {
+		if max := l1Origin.Time + spec.MaxSequencerDrift(l1Origin.Time); blockTimestamp > max {
 			if len(batch.GetBlockTransactions(i)) == 0 {
 				// If the sequencer is co-operating by producing an empty batch,
 				// then allow the batch if it was the right thing to do to maintain the L2 time >= L1 time invariant.

op-node/rollup/derive/batches_test.go

@@ -26,24 +26,51 @@ type ValidBatchTestCase struct {
 	Expected       BatchValidity
 	ExpectedLog    string               // log message that must be included
 	NotExpectedLog string               // log message that must not be included
-	DeltaTime      *uint64
+	ConfigMod      func(*rollup.Config) // optional rollup config mod
 }
 
+var zero64 = uint64(0)
+
+func deltaAtGenesis(c *rollup.Config) {
+	c.DeltaTime = &zero64
+}
+
+func deltaAt(t *uint64) func(*rollup.Config) {
+	return func(c *rollup.Config) {
+		c.DeltaTime = t
+	}
+}
+
+func fjordAt(t *uint64) func(*rollup.Config) {
+	return func(c *rollup.Config) {
+		c.FjordTime = t
+	}
+}
+
+func multiMod[T any](mods ...func(T)) func(T) {
+	return func(x T) {
+		for _, mod := range mods {
+			mod(x)
+		}
+	}
+}
+
+const defaultBlockTime = 2
+
 func TestValidBatch(t *testing.T) {
-	defaultConf := rollup.Config{
+	defaultConf := func() *rollup.Config {
+		return &rollup.Config{
 			Genesis: rollup.Genesis{
 				L2Time: 31, // a genesis time that itself does not align to make it more interesting
 			},
-		BlockTime:         2,
+			BlockTime:         defaultBlockTime,
 			SeqWindowSize:     4,
 			MaxSequencerDrift: 6,
-		// other config fields are ignored and can be left empty.
-		DeltaTime: nil,
+		}
 	}
 
 	rng := rand.New(rand.NewSource(1234))
 
-	minTs := uint64(0)
 	chainId := new(big.Int).SetUint64(rng.Uint64())
 	signer := types.NewLondonSigner(chainId)
 	randTx := testutils.RandomTx(rng, new(big.Int).SetUint64(rng.Uint64()), signer)
@@ -94,7 +121,7 @@ func TestValidBatch(t *testing.T) {
 		Hash:           testutils.RandomHash(rng),
 		Number:         l2A0.Number + 1,
 		ParentHash:     l2A0.Hash,
-		Time:           l2A0.Time + defaultConf.BlockTime,
+		Time:           l2A0.Time + defaultBlockTime,
 		L1Origin:       l1A.ID(),
 		SequenceNumber: 1,
 	}
@@ -103,7 +130,7 @@ func TestValidBatch(t *testing.T) {
 		Hash:           testutils.RandomHash(rng),
 		Number:         l2A1.Number + 1,
 		ParentHash:     l2A1.Hash,
-		Time:           l2A1.Time + defaultConf.BlockTime,
+		Time:           l2A1.Time + defaultBlockTime,
 		L1Origin:       l1A.ID(),
 		SequenceNumber: 2,
 	}
@@ -112,7 +139,7 @@ func TestValidBatch(t *testing.T) {
 		Hash:           testutils.RandomHash(rng),
 		Number:         l2A2.Number + 1,
 		ParentHash:     l2A2.Hash,
-		Time:           l2A2.Time + defaultConf.BlockTime,
+		Time:           l2A2.Time + defaultBlockTime,
 		L1Origin:       l1A.ID(),
 		SequenceNumber: 3,
 	}
@@ -121,7 +148,7 @@ func TestValidBatch(t *testing.T) {
 		Hash:           testutils.RandomHash(rng),
 		Number:         l2A3.Number + 1,
 		ParentHash:     l2A3.Hash,
-		Time:           l2A3.Time + defaultConf.BlockTime, // 8 seconds larger than l1A0, 1 larger than origin
+		Time:           l2A3.Time + defaultBlockTime, // 8 seconds larger than l1A0, 1 larger than origin
 		L1Origin:       l1B.ID(),
 		SequenceNumber: 0,
 	}
@@ -130,7 +157,7 @@ func TestValidBatch(t *testing.T) {
 		Hash:           testutils.RandomHash(rng),
 		Number:         l2B0.Number + 1,
 		ParentHash:     l2B0.Hash,
-		Time:           l2B0.Time + defaultConf.BlockTime,
+		Time:           l2B0.Time + defaultBlockTime,
 		L1Origin:       l1B.ID(),
 		SequenceNumber: 1,
 	}
@@ -139,7 +166,7 @@ func TestValidBatch(t *testing.T) {
 		Hash:           testutils.RandomHash(rng),
 		Number:         l2B1.Number + 1,
 		ParentHash:     l2B1.Hash,
-		Time:           l2B1.Time + defaultConf.BlockTime,
+		Time:           l2B1.Time + defaultBlockTime,
 		L1Origin:       l1B.ID(),
 		SequenceNumber: 2,
 	}
@@ -174,7 +201,7 @@ func TestValidBatch(t *testing.T) {
 		Hash:           testutils.RandomHash(rng),
 		Number:         l2X0.Number + 1,
 		ParentHash:     l2X0.Hash,
-		Time:           l2X0.Time + defaultConf.BlockTime, // exceeds sequencer time drift, forced to be empty block
+		Time:           l2X0.Time + defaultBlockTime, // exceeds sequencer time drift, forced to be empty block
 		L1Origin:       l1Y.ID(),
 		SequenceNumber: 0,
 	}
@@ -182,7 +209,7 @@ func TestValidBatch(t *testing.T) {
 		Hash:           testutils.RandomHash(rng),
 		Number:         l2Y0.Number + 1,
 		ParentHash:     l2Y0.Hash,
-		Time:           l2Y0.Time + defaultConf.BlockTime, // exceeds sequencer time drift, forced to be empty block
+		Time:           l2Y0.Time + defaultBlockTime, // exceeds sequencer time drift, forced to be empty block
 		L1Origin:       l1Z.ID(),
 		SequenceNumber: 0,
 	}
@@ -191,7 +218,7 @@ func TestValidBatch(t *testing.T) {
 		Hash:           testutils.RandomHash(rng),
 		Number:         l2A3.Number + 1,
 		ParentHash:     l2A3.Hash,
-		Time:           l2A3.Time + defaultConf.BlockTime, // 4*2 = 8, higher than seq time drift
+		Time:           l2A3.Time + defaultBlockTime, // 4*2 = 8, higher than seq time drift
 		L1Origin:       l1A.ID(),
 		SequenceNumber: 4,
 	}
@@ -310,7 +337,7 @@ func TestValidBatch(t *testing.T) {
 					ParentHash:   l2B0.Hash,                          // build on top of safe head to continue
 					EpochNum:     rollup.Epoch(l2A3.L1Origin.Number), // epoch A is no longer valid
 					EpochHash:    l2A3.L1Origin.Hash,
-					Timestamp:    l2B0.Time + defaultConf.BlockTime, // pass the timestamp check to get too epoch check
+					Timestamp:    l2B0.Time + defaultBlockTime, // pass the timestamp check to get too epoch check
 					Transactions: nil,
 				},
 			},
@@ -380,6 +407,23 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected: BatchDrop,
 		},
+		{ // this is the same test case as above, but with Fjord activated at the L1 origin, so accepted batch
+			Name:       "no sequencer time drift on same epoch with non-empty txs and Fjord",
+			L1Blocks:   []eth.L1BlockRef{l1A, l1B},
+			L2SafeHead: l2A3,
+			Batch: BatchWithL1InclusionBlock{
+				L1InclusionBlock: l1B,
+				Batch: &SingularBatch{ // we build l2A4, which has a timestamp of 2*4 = 8 higher than l2A0
+					ParentHash:   l2A4.ParentHash,
+					EpochNum:     rollup.Epoch(l2A4.L1Origin.Number),
+					EpochHash:    l2A4.L1Origin.Hash,
+					Timestamp:    l2A4.Time,
+					Transactions: []hexutil.Bytes{[]byte("sequencer should include this tx")},
+				},
+			},
+			ConfigMod: fjordAt(&l1A.Time),
+			Expected:  BatchAccept,
+		},
 		{
 			Name:       "sequencer time drift on changing epoch with non-empty txs",
 			L1Blocks:   []eth.L1BlockRef{l1X, l1Y, l1Z},
@@ -544,7 +588,7 @@ func TestValidBatch(t *testing.T) {
 					ParentHash:   l2A2.Hash,
 					EpochNum:     rollup.Epoch(l2B0.L1Origin.Number),
 					EpochHash:    l2B0.L1Origin.Hash,
-					Timestamp:    l2A2.Time + defaultConf.BlockTime,
+					Timestamp:    l2A2.Time + defaultBlockTime,
 					Transactions: nil,
 				},
 			},
@@ -570,7 +614,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchUndecided,
 			ExpectedLog: "missing L1 block input, cannot proceed with batch checking",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "future timestamp",
@@ -590,7 +634,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchFuture,
 			ExpectedLog: "received out-of-order batch for future processing after next batch",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "misaligned timestamp",
@@ -610,7 +654,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "span batch has no new blocks after safe head",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "invalid parent block hash",
@@ -630,7 +674,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "ignoring batch with mismatching parent hash",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "sequence window expired",
@@ -650,7 +694,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "batch was included too late, sequence window expired",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "epoch too old, but good parent hash and timestamp", // repeat of now outdated l2A3 data
@@ -663,20 +707,20 @@ func TestValidBatch(t *testing.T) {
 						ParentHash:   l2B0.Hash,                          // build on top of safe head to continue
 						EpochNum:     rollup.Epoch(l2A3.L1Origin.Number), // epoch A is no longer valid
 						EpochHash:    l2A3.L1Origin.Hash,
-						Timestamp:    l2B0.Time + defaultConf.BlockTime, // pass the timestamp check to get too epoch check
+						Timestamp:    l2B0.Time + defaultBlockTime, // pass the timestamp check to get too epoch check
 						Transactions: nil,
 					},
 					{
 						EpochNum:     rollup.Epoch(l1B.Number),
 						EpochHash:    l1B.Hash, // pass the l1 origin check
-						Timestamp:    l2B0.Time + defaultConf.BlockTime*2,
+						Timestamp:    l2B0.Time + defaultBlockTime*2,
 						Transactions: nil,
 					},
 				}, uint64(0), big.NewInt(0)),
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "dropped batch, epoch is too old",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "insufficient L1 info for eager derivation",
@@ -696,7 +740,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchUndecided,
 			ExpectedLog: "eager batch wants to advance epoch, but could not without more L1 blocks",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "insufficient L1 info for eager derivation - long span",
@@ -723,7 +767,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchUndecided,
 			ExpectedLog: "need more l1 blocks to check entire origins of span batch",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "epoch too new",
@@ -743,7 +787,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "batch is for future epoch too far ahead, while it has the next timestamp, so it must be invalid",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "epoch hash wrong",
@@ -763,7 +807,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "batch is for different L1 chain, epoch hash does not match",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "epoch hash wrong - long span",
@@ -790,7 +834,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "batch is for different L1 chain, epoch hash does not match",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "sequencer time drift on same epoch with non-empty txs",
@@ -810,7 +854,26 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "batch exceeded sequencer time drift, sequencer must adopt new L1 origin to include transactions again",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
+		},
+		{
+			Name:       "no sequencer time drift on same epoch with non-empty txs and Fjord",
+			L1Blocks:   []eth.L1BlockRef{l1A, l1B},
+			L2SafeHead: l2A3,
+			Batch: BatchWithL1InclusionBlock{
+				L1InclusionBlock: l1B,
+				Batch: initializedSpanBatch([]*SingularBatch{
+					{ // we build l2A4, which has a timestamp of 2*4 = 8 higher than l2A0
+						ParentHash:   l2A4.ParentHash,
+						EpochNum:     rollup.Epoch(l2A4.L1Origin.Number),
+						EpochHash:    l2A4.L1Origin.Hash,
+						Timestamp:    l2A4.Time,
+						Transactions: []hexutil.Bytes{randTxData},
+					},
+				}, uint64(0), big.NewInt(0)),
+			},
+			Expected:  BatchAccept,
+			ConfigMod: multiMod(deltaAtGenesis, fjordAt(&l1A.Time)),
 		},
 		{
 			Name:       "sequencer time drift on same epoch with non-empty txs - long span",
@@ -837,7 +900,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "batch exceeded sequencer time drift, sequencer must adopt new L1 origin to include transactions again",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "sequencer time drift on changing epoch with non-empty txs",
@@ -857,7 +920,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "batch exceeded sequencer time drift, sequencer must adopt new L1 origin to include transactions again",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "sequencer time drift on same epoch with empty txs and late next epoch",
@@ -876,7 +939,7 @@ func TestValidBatch(t *testing.T) {
 				}, uint64(0), big.NewInt(0)),
 			},
 			Expected:  BatchAccept, // accepted because empty & preserving L2 time invariant
-			DeltaTime: &minTs,
+			ConfigMod: deltaAtGenesis,
 		},
 		{
 			Name:       "sequencer time drift on changing epoch with empty txs",
@@ -902,7 +965,7 @@ func TestValidBatch(t *testing.T) {
 				}, uint64(0), big.NewInt(0)),
 			},
 			Expected:       BatchAccept, // accepted because empty & still advancing epoch
-			DeltaTime:      &minTs,
+			ConfigMod:      deltaAtGenesis,
 			NotExpectedLog: "continuing with empty batch before late L1 block to preserve L2 time invariant",
 		},
 		{
@@ -923,7 +986,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchUndecided, // we have to wait till the next epoch is in sight to check the time
 			ExpectedLog: "without the next L1 origin we cannot determine yet if this empty batch that exceeds the time drift is still valid",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "sequencer time drift on same epoch with empty txs and no next epoch in sight yet - long span",
@@ -950,7 +1013,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchUndecided, // we have to wait till the next epoch is in sight to check the time
 			ExpectedLog: "without the next L1 origin we cannot determine yet if this empty batch that exceeds the time drift is still valid",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "sequencer time drift on same epoch with empty txs and but in-sight epoch that invalidates it",
@@ -970,7 +1033,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop, // dropped because it could have advanced the epoch to B
 			ExpectedLog: "batch exceeded sequencer time drift without adopting next origin, and next L1 origin would have been valid",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "sequencer time drift on same epoch with empty txs and but in-sight epoch that invalidates it - long span",
@@ -997,7 +1060,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop, // dropped because it could have advanced the epoch to B
 			ExpectedLog: "batch exceeded sequencer time drift without adopting next origin, and next L1 origin would have been valid",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "empty tx included",
@@ -1019,7 +1082,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "transaction data must not be empty, but found empty tx",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "deposit tx included",
@@ -1041,7 +1104,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "sequencers may not embed any deposits into batch data, but found tx that has one",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "valid batch same epoch",
@@ -1060,7 +1123,7 @@ func TestValidBatch(t *testing.T) {
 				}, uint64(0), big.NewInt(0)),
 			},
 			Expected:  BatchAccept,
-			DeltaTime: &minTs,
+			ConfigMod: deltaAtGenesis,
 		},
 		{
 			Name:       "valid batch changing epoch",
@@ -1079,7 +1142,7 @@ func TestValidBatch(t *testing.T) {
 				}, uint64(0), big.NewInt(0)),
 			},
 			Expected:  BatchAccept,
-			DeltaTime: &minTs,
+			ConfigMod: deltaAtGenesis,
 		},
 		{
 			Name:       "batch with L2 time before L1 time",
@@ -1092,14 +1155,14 @@ func TestValidBatch(t *testing.T) {
 						ParentHash:   l2A2.Hash,
 						EpochNum:     rollup.Epoch(l2B0.L1Origin.Number),
 						EpochHash:    l2B0.L1Origin.Hash,
-						Timestamp:    l2A2.Time + defaultConf.BlockTime,
+						Timestamp:    l2A2.Time + defaultBlockTime,
 						Transactions: nil,
 					},
 				}, uint64(0), big.NewInt(0)),
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "block timestamp is less than L1 origin timestamp",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "batch with L2 time before L1 time - long span",
@@ -1119,14 +1182,14 @@ func TestValidBatch(t *testing.T) {
 						ParentHash:   l2A2.Hash,
 						EpochNum:     rollup.Epoch(l2B0.L1Origin.Number),
 						EpochHash:    l2B0.L1Origin.Hash,
-						Timestamp:    l2A2.Time + defaultConf.BlockTime,
+						Timestamp:    l2A2.Time + defaultBlockTime,
 						Transactions: nil,
 					},
 				}, uint64(0), big.NewInt(0)),
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "block timestamp is less than L1 origin timestamp",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "valid overlapping batch",
@@ -1152,7 +1215,7 @@ func TestValidBatch(t *testing.T) {
 				}, uint64(0), big.NewInt(0)),
 			},
 			Expected:  BatchAccept,
-			DeltaTime: &minTs,
+			ConfigMod: deltaAtGenesis,
 		},
 		{
 			Name:       "longer overlapping batch",
@@ -1185,7 +1248,7 @@ func TestValidBatch(t *testing.T) {
 				}, uint64(0), big.NewInt(0)),
 			},
 			Expected:  BatchAccept,
-			DeltaTime: &minTs,
+			ConfigMod: deltaAtGenesis,
 		},
 		{
 			Name:       "fully overlapping batch",
@@ -1212,7 +1275,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "span batch has no new blocks after safe head",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "overlapping batch with invalid parent hash",
@@ -1239,7 +1302,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "ignoring batch with mismatching parent hash",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "overlapping batch with invalid origin number",
@@ -1266,7 +1329,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "overlapped block's L1 origin number does not match",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "overlapping batch with invalid tx",
@@ -1293,7 +1356,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "overlapped block's tx count does not match",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "overlapping batch l2 fetcher error",
@@ -1327,7 +1390,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchUndecided,
 			ExpectedLog: "failed to fetch L2 block",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "short block time",
@@ -1354,7 +1417,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "batch has misaligned timestamp, block time is too short",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "misaligned batch",
@@ -1381,7 +1444,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchDrop,
 			ExpectedLog: "batch has misaligned timestamp, not overlapped exactly",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "failed to fetch overlapping block payload",
@@ -1408,7 +1471,7 @@ func TestValidBatch(t *testing.T) {
 			},
 			Expected:    BatchUndecided,
 			ExpectedLog: "failed to fetch L2 block payload",
-			DeltaTime:   &minTs,
+			ConfigMod:   deltaAtGenesis,
 		},
 		{
 			Name:       "singular batch before hard fork",
@@ -1424,7 +1487,7 @@ func TestValidBatch(t *testing.T) {
 					Transactions: []hexutil.Bytes{randTxData},
 				},
 			},
-			DeltaTime: &l1B.Time,
+			ConfigMod: deltaAt(&l1B.Time),
 			Expected:  BatchAccept,
 		},
 		{
@@ -1443,7 +1506,7 @@ func TestValidBatch(t *testing.T) {
 					},
 				}, uint64(0), big.NewInt(0)),
 			},
-			DeltaTime:   &l1B.Time,
+			ConfigMod:   deltaAt(&l1B.Time),
 			Expected:    BatchDrop,
 			ExpectedLog: "received SpanBatch with L1 origin before Delta hard fork",
 		},
@@ -1461,7 +1524,7 @@ func TestValidBatch(t *testing.T) {
 					Transactions: []hexutil.Bytes{randTxData},
 				},
 			},
-			DeltaTime: &l1A.Time,
+			ConfigMod: deltaAt(&l1A.Time),
 			Expected:  BatchAccept,
 		},
 		{
@@ -1480,7 +1543,7 @@ func TestValidBatch(t *testing.T) {
 					},
 				}, uint64(0), big.NewInt(0)),
 			},
-			DeltaTime: &l1A.Time,
+			ConfigMod: deltaAt(&l1A.Time),
 			Expected:  BatchAccept,
 		},
 	}
@@ -1515,11 +1578,11 @@ func TestValidBatch(t *testing.T) {
 
 	runTestCase := func(t *testing.T, testCase ValidBatchTestCase) {
 		ctx := context.Background()
-		rcfg := defaultConf
-		if testCase.DeltaTime != nil {
-			rcfg.DeltaTime = testCase.DeltaTime
+		rcfg := defaultConf()
+		if mod := testCase.ConfigMod; mod != nil {
+			mod(rcfg)
 		}
-		validity := CheckBatch(ctx, &rcfg, logger, testCase.L1Blocks, testCase.L2SafeHead, &testCase.Batch, &l2Client)
+		validity := CheckBatch(ctx, rcfg, logger, testCase.L1Blocks, testCase.L2SafeHead, &testCase.Batch, &l2Client)
 		require.Equal(t, testCase.Expected, validity, "batch check must return expected validity level")
 		if expLog := testCase.ExpectedLog; expLog != "" {
 			// Check if ExpectedLog is contained in the log buffer
@@ -1595,7 +1658,7 @@ func TestValidBatch(t *testing.T) {
 		},
 		Expected:    BatchDrop,
 		ExpectedLog: "overlapped block's transaction does not match",
-		DeltaTime:   &minTs,
+		ConfigMod:   deltaAtGenesis,
 	}
 
 	t.Run(differentTxtestCase.Name, func(t *testing.T) {
@@ -1640,7 +1703,7 @@ func TestValidBatch(t *testing.T) {
 		},
 		Expected:    BatchDrop,
 		ExpectedLog: "failed to extract L2BlockRef from execution payload",
-		DeltaTime:   &minTs,
+		ConfigMod:   deltaAtGenesis,
 	}
 
 	t.Run(invalidTxTestCase.Name, func(t *testing.T) {

op-node/rollup/driver/origin_selector.go

@@ -21,6 +21,7 @@ type L1Blocks interface {
 type L1OriginSelector struct {
 	log  log.Logger
 	cfg  *rollup.Config
+	spec *rollup.ChainSpec
 
 	l1 L1Blocks
 }
@@ -29,6 +30,7 @@ func NewL1OriginSelector(log log.Logger, cfg *rollup.Config, l1 L1Blocks) *L1Ori
 	return &L1OriginSelector{
 		log:  log,
 		cfg:  cfg,
+		spec: rollup.NewChainSpec(cfg),
 		l1:   l1,
 	}
 }
@@ -42,12 +44,13 @@ func (los *L1OriginSelector) FindL1Origin(ctx context.Context, l2Head eth.L2Bloc
 	if err != nil {
 		return eth.L1BlockRef{}, err
 	}
+	msd := los.spec.MaxSequencerDrift(currentOrigin.Time)
 	log := los.log.New("current", currentOrigin, "current_time", currentOrigin.Time,
-		"l2_head", l2Head, "l2_head_time", l2Head.Time)
+		"l2_head", l2Head, "l2_head_time", l2Head.Time, "max_seq_drift", msd)
 
 	// If we are past the sequencer depth, we may want to advance the origin, but need to still
 	// check the time of the next origin.
-	pastSeqDrift := l2Head.Time+los.cfg.BlockTime > currentOrigin.Time+los.cfg.MaxSequencerDrift
+	pastSeqDrift := l2Head.Time+los.cfg.BlockTime > currentOrigin.Time+msd
 	if pastSeqDrift {
 		log.Warn("Next L2 block time is past the sequencer drift + current origin time")
 	}

op-node/rollup/driver/origin_selector_test.go

@@ -8,6 +8,7 @@ import (
 	"github.com/ethereum-optimism/optimism/op-service/eth"
 	"github.com/ethereum-optimism/optimism/op-service/testlog"
 	"github.com/ethereum-optimism/optimism/op-service/testutils"
+	"github.com/ethereum/go-ethereum"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/stretchr/testify/require"
@@ -176,6 +177,42 @@ func TestOriginSelectorStrictConfDepth(t *testing.T) {
 	require.ErrorContains(t, err, "sequencer time drift")
 }
 
+func u64ptr(n uint64) *uint64 {
+	return &n
+}
+
+// TestOriginSelector_FjordSeqDrift has a similar setup to the previous test
+// TestOriginSelectorStrictConfDepth but with Fjord activated at the l1 origin.
+// This time the same L1 origin is returned if no new L1 head is seen, instead of an error,
+// because the Fjord max sequencer drift is higher.
+func TestOriginSelector_FjordSeqDrift(t *testing.T) {
+	log := testlog.Logger(t, log.LevelCrit)
+	cfg := &rollup.Config{
+		MaxSequencerDrift: 8,
+		BlockTime:         2,
+		FjordTime:         u64ptr(20), // a's timestamp
+	}
+	l1 := &testutils.MockL1Source{}
+	defer l1.AssertExpectations(t)
+	a := eth.L1BlockRef{
+		Hash:   common.Hash{'a'},
+		Number: 10,
+		Time:   20,
+	}
+	l2Head := eth.L2BlockRef{
+		L1Origin: a.ID(),
+		Time:     27, // next L2 block time would be past pre-Fjord seq drift
+	}
+
+	l1.ExpectL1BlockRefByHash(a.Hash, a, nil)
+	l1.ExpectL1BlockRefByNumber(a.Number+1, eth.L1BlockRef{}, ethereum.NotFound)
+	s := NewL1OriginSelector(log, cfg, l1)
+
+	l1O, err := s.FindL1Origin(context.Background(), l2Head)
+	require.NoError(t, err, "with Fjord activated, have increased max seq drift")
+	require.Equal(t, a, l1O)
+}
+
 // TestOriginSelectorSeqDriftRespectsNextOriginTime
 //
 // There are 2 L1 blocks at time 20 & 100. The L2 Head is at time 27.

op-node/rollup/driver/sequencer.go

@@ -35,6 +35,7 @@ type SequencerMetrics interface {
 type Sequencer struct {
 	log       log.Logger
 	rollupCfg *rollup.Config
+	spec      *rollup.ChainSpec
 
 	engine derive.EngineControl
 
@@ -53,6 +54,7 @@ func NewSequencer(log log.Logger, rollupCfg *rollup.Config, engine derive.Engine
 	return &Sequencer{
 		log:              log,
 		rollupCfg:        rollupCfg,
+		spec:             rollup.NewChainSpec(rollupCfg),
 		engine:           engine,
 		timeNow:          time.Now,
 		attrBuilder:      attributesBuilder,
@@ -91,7 +93,7 @@ func (d *Sequencer) StartBuildingBlock(ctx context.Context) error {
 	// empty blocks (other than the L1 info deposit and any user deposits). We handle this by
 	// setting NoTxPool to true, which will cause the Sequencer to not include any transactions
 	// from the transaction pool.
-	attrs.NoTxPool = uint64(attrs.Timestamp) > l1Origin.Time+d.rollupCfg.MaxSequencerDrift
+	attrs.NoTxPool = uint64(attrs.Timestamp) > l1Origin.Time+d.spec.MaxSequencerDrift(l1Origin.Time)
 
 	// For the Ecotone activation block we shouldn't include any sequencer transactions.
 	if d.rollupCfg.IsEcotoneActivationBlock(uint64(attrs.Timestamp)) {

op-node/rollup/types.go

@@ -60,7 +60,12 @@ type Config struct {
 	//
 	// Note: When L1 has many 1 second consecutive blocks, and L2 grows at fixed 2 seconds,
 	// the L2 time may still grow beyond this difference.
-	MaxSequencerDrift uint64 `json:"max_sequencer_drift"`
+	//
+	// With Fjord, the MaxSequencerDrift becomes a constant. Use the ChainSpec
+	// instead of reading this rollup configuration field directly to determine
+	// the max sequencer drift for a given block based on the block's L1 origin.
+	// Chains that activate Fjord at genesis may leave this field empty.
+	MaxSequencerDrift uint64 `json:"max_sequencer_drift,omitempty"`
 	// Number of epochs (L1 blocks) per sequencing window, including the epoch L1 origin block itself
 	SeqWindowSize uint64 `json:"seq_window_size"`
 	// Number of L1 blocks between when a channel can be opened and when it must be closed by.