op-node/rollup/derive: Implement pipeline stage multiplexing (#12506)

* op-node/rollup/derive: Implement pipeline stage multiplexing

* fix BatchStage empty batch generation

* fix fork configuration in LargeL1Gaps test

op-chain-ops/genesis/config.go

@@ -369,6 +369,81 @@ func offsetToUpgradeTime(offset *hexutil.Uint64, genesisTime uint64) *uint64 {
 	return &v
 }
 
+func (d *UpgradeScheduleDeployConfig) ForkTimeOffset(fork rollup.ForkName) *uint64 {
+	switch fork {
+	case rollup.Regolith:
+		return (*uint64)(d.L2GenesisRegolithTimeOffset)
+	case rollup.Canyon:
+		return (*uint64)(d.L2GenesisCanyonTimeOffset)
+	case rollup.Delta:
+		return (*uint64)(d.L2GenesisDeltaTimeOffset)
+	case rollup.Ecotone:
+		return (*uint64)(d.L2GenesisEcotoneTimeOffset)
+	case rollup.Fjord:
+		return (*uint64)(d.L2GenesisFjordTimeOffset)
+	case rollup.Granite:
+		return (*uint64)(d.L2GenesisGraniteTimeOffset)
+	case rollup.Holocene:
+		return (*uint64)(d.L2GenesisHoloceneTimeOffset)
+	case rollup.Interop:
+		return (*uint64)(d.L2GenesisInteropTimeOffset)
+	default:
+		panic(fmt.Sprintf("unknown fork: %s", fork))
+	}
+}
+
+func (d *UpgradeScheduleDeployConfig) SetForkTimeOffset(fork rollup.ForkName, offset *uint64) {
+	switch fork {
+	case rollup.Regolith:
+		d.L2GenesisRegolithTimeOffset = (*hexutil.Uint64)(offset)
+	case rollup.Canyon:
+		d.L2GenesisCanyonTimeOffset = (*hexutil.Uint64)(offset)
+	case rollup.Delta:
+		d.L2GenesisDeltaTimeOffset = (*hexutil.Uint64)(offset)
+	case rollup.Ecotone:
+		d.L2GenesisEcotoneTimeOffset = (*hexutil.Uint64)(offset)
+	case rollup.Fjord:
+		d.L2GenesisFjordTimeOffset = (*hexutil.Uint64)(offset)
+	case rollup.Granite:
+		d.L2GenesisGraniteTimeOffset = (*hexutil.Uint64)(offset)
+	case rollup.Holocene:
+		d.L2GenesisHoloceneTimeOffset = (*hexutil.Uint64)(offset)
+	case rollup.Interop:
+		d.L2GenesisInteropTimeOffset = (*hexutil.Uint64)(offset)
+	default:
+		panic(fmt.Sprintf("unknown fork: %s", fork))
+	}
+}
+
+var scheduleableForks = rollup.ForksFrom(rollup.Regolith)
+
+// ActivateForkAtOffset activates the given fork at the given offset. Previous forks are activated
+// at genesis and later forks are deactivated.
+// If multiple forks should be activated at a later time than genesis, first call
+// ActivateForkAtOffset with the earliest fork and then SetForkTimeOffset to individually set later
+// forks.
+func (d *UpgradeScheduleDeployConfig) ActivateForkAtOffset(fork rollup.ForkName, offset uint64) {
+	if !rollup.IsValidFork(fork) || fork == rollup.Bedrock {
+		panic(fmt.Sprintf("invalid fork: %s", fork))
+	}
+	ts := new(uint64)
+	for i, f := range scheduleableForks {
+		if f == fork {
+			d.SetForkTimeOffset(fork, &offset)
+			ts = nil
+		} else {
+			d.SetForkTimeOffset(scheduleableForks[i], ts)
+		}
+	}
+}
+
+// ActivateForkAtGenesis activates the given fork, and all previous forks, at genesis.
+// Later forks are deactivated.
+// See also [ActivateForkAtOffset].
+func (d *UpgradeScheduleDeployConfig) ActivateForkAtGenesis(fork rollup.ForkName) {
+	d.ActivateForkAtOffset(fork, 0)
+}
+
 func (d *UpgradeScheduleDeployConfig) RegolithTime(genesisTime uint64) *uint64 {
 	return offsetToUpgradeTime(d.L2GenesisRegolithTimeOffset, genesisTime)
 }
@@ -402,7 +477,6 @@ func (d *UpgradeScheduleDeployConfig) InteropTime(genesisTime uint64) *uint64 {
 }
 
 func (d *UpgradeScheduleDeployConfig) AllocMode(genesisTime uint64) L2AllocsMode {
-
 	forks := d.forks()
 	for i := len(forks) - 1; i >= 0; i-- {
 		if forkTime := offsetToUpgradeTime(forks[i].L2GenesisTimeOffset, genesisTime); forkTime != nil && *forkTime == 0 {

op-chain-ops/genesis/config_test.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/stretchr/testify/require"
 
+	"github.com/ethereum-optimism/optimism/op-node/rollup"
 	"github.com/ethereum-optimism/optimism/op-service/testlog"
 )
 
@@ -45,7 +46,10 @@ func TestRegolithTimeZero(t *testing.T) {
 	config := &DeployConfig{
 		L2InitializationConfig: L2InitializationConfig{
 			UpgradeScheduleDeployConfig: UpgradeScheduleDeployConfig{
-				L2GenesisRegolithTimeOffset: &regolithOffset}}}
+				L2GenesisRegolithTimeOffset: &regolithOffset,
+			},
+		},
+	}
 	require.Equal(t, uint64(0), *config.RegolithTime(1234))
 }
 
@@ -54,7 +58,10 @@ func TestRegolithTimeAsOffset(t *testing.T) {
 	config := &DeployConfig{
 		L2InitializationConfig: L2InitializationConfig{
 			UpgradeScheduleDeployConfig: UpgradeScheduleDeployConfig{
-				L2GenesisRegolithTimeOffset: &regolithOffset}}}
+				L2GenesisRegolithTimeOffset: &regolithOffset,
+			},
+		},
+	}
 	require.Equal(t, uint64(1500+5000), *config.RegolithTime(5000))
 }
 
@@ -63,7 +70,10 @@ func TestCanyonTimeZero(t *testing.T) {
 	config := &DeployConfig{
 		L2InitializationConfig: L2InitializationConfig{
 			UpgradeScheduleDeployConfig: UpgradeScheduleDeployConfig{
-				L2GenesisCanyonTimeOffset: &canyonOffset}}}
+				L2GenesisCanyonTimeOffset: &canyonOffset,
+			},
+		},
+	}
 	require.Equal(t, uint64(0), *config.CanyonTime(1234))
 }
 
@@ -72,7 +82,10 @@ func TestCanyonTimeOffset(t *testing.T) {
 	config := &DeployConfig{
 		L2InitializationConfig: L2InitializationConfig{
 			UpgradeScheduleDeployConfig: UpgradeScheduleDeployConfig{
-				L2GenesisCanyonTimeOffset: &canyonOffset}}}
+				L2GenesisCanyonTimeOffset: &canyonOffset,
+			},
+		},
+	}
 	require.Equal(t, uint64(1234+1500), *config.CanyonTime(1234))
 }
 
@@ -124,3 +137,41 @@ func TestL1Deployments(t *testing.T) {
 	// One that doesn't exist returns empty string
 	require.Equal(t, "", deployments.GetName(common.Address{19: 0xff}))
 }
+
+// This test guarantees that getters and setters for all forks are present.
+func TestUpgradeScheduleDeployConfig_ForkGettersAndSetters(t *testing.T) {
+	var d UpgradeScheduleDeployConfig
+	for i, fork := range rollup.ForksFrom(rollup.Regolith) {
+		require.Nil(t, d.ForkTimeOffset(fork))
+		offset := uint64(i * 42)
+		d.SetForkTimeOffset(fork, &offset)
+		require.Equal(t, offset, *d.ForkTimeOffset(fork))
+	}
+}
+
+func TestUpgradeScheduleDeployConfig_ActivateForkAtOffset(t *testing.T) {
+	var d UpgradeScheduleDeployConfig
+	ts := uint64(42)
+	t.Run("invalid", func(t *testing.T) {
+		require.Panics(t, func() { d.ActivateForkAtOffset(rollup.Bedrock, ts) })
+	})
+
+	t.Run("regolith", func(t *testing.T) {
+		d.ActivateForkAtOffset(rollup.Regolith, ts)
+		require.EqualValues(t, &ts, d.L2GenesisRegolithTimeOffset)
+		for _, fork := range scheduleableForks[1:] {
+			require.Nil(t, d.ForkTimeOffset(fork))
+		}
+	})
+
+	t.Run("ecotone", func(t *testing.T) {
+		d.ActivateForkAtOffset(rollup.Ecotone, ts)
+		require.EqualValues(t, &ts, d.L2GenesisEcotoneTimeOffset)
+		for _, fork := range scheduleableForks[:3] {
+			require.Zero(t, *d.ForkTimeOffset(fork))
+		}
+		for _, fork := range scheduleableForks[4:] {
+			require.Nil(t, d.ForkTimeOffset(fork))
+		}
+	})
+}

op-e2e/actions/derivation/blocktime_test.go

@@ -7,6 +7,7 @@ import (
 	actionsHelpers "github.com/ethereum-optimism/optimism/op-e2e/actions/helpers"
 	upgradesHelpers "github.com/ethereum-optimism/optimism/op-e2e/actions/upgrades/helpers"
 	"github.com/ethereum-optimism/optimism/op-e2e/e2eutils"
+	"github.com/ethereum-optimism/optimism/op-node/rollup"
 	"github.com/ethereum-optimism/optimism/op-service/testlog"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -163,11 +164,13 @@ func LargeL1Gaps(gt *testing.T, deltaTimeOffset *hexutil.Uint64) {
 	dp.DeployConfig.L2BlockTime = 2
 	dp.DeployConfig.SequencerWindowSize = 4
 	dp.DeployConfig.MaxSequencerDrift = 32
-	dp.DeployConfig.L2GenesisEcotoneTimeOffset = nil
-	dp.DeployConfig.L2GenesisFjordTimeOffset = nil
+	if deltaTimeOffset != nil {
+		dp.DeployConfig.ActivateForkAtOffset(rollup.Delta, uint64(*deltaTimeOffset))
+	} else {
+		dp.DeployConfig.ActivateForkAtGenesis(rollup.Canyon)
+	}
 	// TODO(client-pod#831): The Ecotone (and Fjord) activation blocks don't include user txs,
 	// so disabling these forks for now.
-	upgradesHelpers.ApplyDeltaTimeOffset(dp, deltaTimeOffset)
 	sd := e2eutils.Setup(t, dp, actionsHelpers.DefaultAlloc)
 	log := testlog.Logger(t, log.LevelDebug)
 

op-e2e/actions/helpers/env.go

+package helpers
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+
+	"github.com/ethereum-optimism/optimism/op-chain-ops/genesis"
+	"github.com/ethereum-optimism/optimism/op-e2e/e2eutils"
+	"github.com/ethereum-optimism/optimism/op-node/rollup"
+	"github.com/ethereum-optimism/optimism/op-node/rollup/sync"
+	"github.com/ethereum-optimism/optimism/op-service/testlog"
+)
+
+type Env struct {
+	Log  log.Logger
+	Logs *testlog.CapturingHandler
+
+	SetupData *e2eutils.SetupData
+
+	Miner       *L1Miner
+	Seq         *L2Sequencer
+	SeqEngine   *L2Engine
+	Verifier    *L2Verifier
+	VerifEngine *L2Engine
+	Batcher     *L2Batcher
+}
+
+type EnvOpt struct {
+	DeployConfigMod func(*genesis.DeployConfig)
+}
+
+func WithActiveFork(fork rollup.ForkName, offset uint64) EnvOpt {
+	return EnvOpt{
+		DeployConfigMod: func(d *genesis.DeployConfig) {
+			d.ActivateForkAtOffset(fork, offset)
+		},
+	}
+}
+
+func WithActiveGenesisFork(fork rollup.ForkName) EnvOpt {
+	return WithActiveFork(fork, 0)
+}
+
+// DefaultFork specifies the default fork to use when setting up the action test environment.
+// Currently manually set to Holocene.
+// Replace with `var DefaultFork = func() rollup.ForkName { return rollup.AllForks[len(rollup.AllForks)-1] }()` after Interop launch.
+const DefaultFork = rollup.Holocene
+
+// SetupEnv sets up a default action test environment. If no fork is specified, the default fork as
+// specified by the package variable [defaultFork] is used.
+func SetupEnv(t StatefulTesting, opts ...EnvOpt) (env Env) {
+	dp := e2eutils.MakeDeployParams(t, DefaultRollupTestParams())
+
+	log, logs := testlog.CaptureLogger(t, log.LevelDebug)
+	env.Log, env.Logs = log, logs
+
+	dp.DeployConfig.ActivateForkAtGenesis(DefaultFork)
+	for _, opt := range opts {
+		if dcMod := opt.DeployConfigMod; dcMod != nil {
+			dcMod(dp.DeployConfig)
+		}
+	}
+
+	sd := e2eutils.Setup(t, dp, DefaultAlloc)
+	env.SetupData = sd
+	env.Miner, env.SeqEngine, env.Seq = SetupSequencerTest(t, sd, log)
+	env.Miner.ActL1SetFeeRecipient(common.Address{'A'})
+	env.VerifEngine, env.Verifier = SetupVerifier(t, sd, log, env.Miner.L1Client(t, sd.RollupCfg), env.Miner.BlobStore(), &sync.Config{})
+	rollupSeqCl := env.Seq.RollupClient()
+	env.Batcher = NewL2Batcher(log, sd.RollupCfg, DefaultBatcherCfg(dp),
+		rollupSeqCl, env.Miner.EthClient(), env.SeqEngine.EthClient(), env.SeqEngine.EngineClient(t, sd.RollupCfg))
+
+	return
+}
+
+func (env Env) ActBatchSubmitAllAndMine(t Testing) (l1InclusionBlock *types.Block) {
+	env.Batcher.ActSubmitAll(t)
+	batchTx := env.Batcher.LastSubmitted
+	env.Miner.ActL1StartBlock(12)(t)
+	env.Miner.ActL1IncludeTxByHash(batchTx.Hash())(t)
+	return env.Miner.ActL1EndBlock(t)
+}

op-e2e/actions/helpers/l1_miner.go

@@ -203,10 +203,10 @@ func (s *L1Miner) ActL1SetFeeRecipient(coinbase common.Address) {
 }
 
 // ActL1EndBlock finishes the new L1 block, and applies it to the chain as unsafe block
-func (s *L1Miner) ActL1EndBlock(t Testing) {
+func (s *L1Miner) ActL1EndBlock(t Testing) *types.Block {
 	if !s.l1Building {
 		t.InvalidAction("cannot end L1 block when not building block")
-		return
+		return nil
 	}
 
 	s.l1Building = false
@@ -253,11 +253,12 @@ func (s *L1Miner) ActL1EndBlock(t Testing) {
 	if err != nil {
 		t.Fatalf("failed to insert block into l1 chain")
 	}
+	return block
 }
 
-func (s *L1Miner) ActEmptyBlock(t Testing) {
+func (s *L1Miner) ActEmptyBlock(t Testing) *types.Block {
 	s.ActL1StartBlock(12)(t)
-	s.ActL1EndBlock(t)
+	return s.ActL1EndBlock(t)
 }
 
 func (s *L1Miner) Close() error {

op-e2e/actions/helpers/l2_sequencer.go

@@ -52,7 +52,8 @@ type L2Sequencer struct {
 
 func NewL2Sequencer(t Testing, log log.Logger, l1 derive.L1Fetcher, blobSrc derive.L1BlobsFetcher,
 	altDASrc driver.AltDAIface, eng L2API, cfg *rollup.Config, seqConfDepth uint64,
-	interopBackend interop.InteropBackend) *L2Sequencer {
+	interopBackend interop.InteropBackend,
+) *L2Sequencer {
 	ver := NewL2Verifier(t, log, l1, blobSrc, altDASrc, eng, cfg, &sync.Config{}, safedb.Disabled, interopBackend)
 	attrBuilder := derive.NewFetchingAttributesBuilder(cfg, l1, eng)
 	seqConfDepthL1 := confdepth.NewConfDepth(seqConfDepth, ver.syncStatus.L1Head, l1)
@@ -130,6 +131,11 @@ func (s *L2Sequencer) ActL2EndBlock(t Testing) {
 		"sync status must be accurate after block building")
 }
 
+func (s *L2Sequencer) ActL2EmptyBlock(t Testing) {
+	s.ActL2StartBlock(t)
+	s.ActL2EndBlock(t)
+}
+
 // ActL2KeepL1Origin makes the sequencer use the current L1 origin, even if the next origin is available.
 func (s *L2Sequencer) ActL2KeepL1Origin(t Testing) {
 	parent := s.engine.UnsafeL2Head()
@@ -143,8 +149,7 @@ func (s *L2Sequencer) ActL2KeepL1Origin(t Testing) {
 func (s *L2Sequencer) ActBuildToL1Head(t Testing) {
 	for s.engine.UnsafeL2Head().L1Origin.Number < s.syncStatus.L1Head().Number {
 		s.ActL2PipelineFull(t)
-		s.ActL2StartBlock(t)
-		s.ActL2EndBlock(t)
+		s.ActL2EmptyBlock(t)
 	}
 }
 
@@ -152,8 +157,7 @@ func (s *L2Sequencer) ActBuildToL1Head(t Testing) {
 func (s *L2Sequencer) ActBuildToL1HeadUnsafe(t Testing) {
 	for s.engine.UnsafeL2Head().L1Origin.Number < s.syncStatus.L1Head().Number {
 		// Note: the derivation pipeline does not run, we are just sequencing a block on top of the existing L2 chain.
-		s.ActL2StartBlock(t)
-		s.ActL2EndBlock(t)
+		s.ActL2EmptyBlock(t)
 	}
 }
 
@@ -166,8 +170,7 @@ func (s *L2Sequencer) ActBuildToL1HeadExcl(t Testing) {
 		if nextOrigin.Number >= s.syncStatus.L1Head().Number {
 			break
 		}
-		s.ActL2StartBlock(t)
-		s.ActL2EndBlock(t)
+		s.ActL2EmptyBlock(t)
 	}
 }
 
@@ -180,44 +183,40 @@ func (s *L2Sequencer) ActBuildToL1HeadExclUnsafe(t Testing) {
 		if nextOrigin.Number >= s.syncStatus.L1Head().Number {
 			break
 		}
-		s.ActL2StartBlock(t)
-		s.ActL2EndBlock(t)
+		s.ActL2EmptyBlock(t)
 	}
 }
 
 func (s *L2Sequencer) ActBuildL2ToTime(t Testing, target uint64) {
 	for s.L2Unsafe().Time < target {
-		s.ActL2StartBlock(t)
-		s.ActL2EndBlock(t)
+		s.ActL2EmptyBlock(t)
 	}
 }
 
 func (s *L2Sequencer) ActBuildL2ToEcotone(t Testing) {
 	require.NotNil(t, s.RollupCfg.EcotoneTime, "cannot activate Ecotone when it is not scheduled")
 	for s.L2Unsafe().Time < *s.RollupCfg.EcotoneTime {
-		s.ActL2StartBlock(t)
-		s.ActL2EndBlock(t)
+		s.ActL2EmptyBlock(t)
 	}
 }
+
 func (s *L2Sequencer) ActBuildL2ToFjord(t Testing) {
 	require.NotNil(t, s.RollupCfg.FjordTime, "cannot activate FjordTime when it is not scheduled")
 	for s.L2Unsafe().Time < *s.RollupCfg.FjordTime {
-		s.ActL2StartBlock(t)
-		s.ActL2EndBlock(t)
+		s.ActL2EmptyBlock(t)
 	}
 }
+
 func (s *L2Sequencer) ActBuildL2ToGranite(t Testing) {
 	require.NotNil(t, s.RollupCfg.GraniteTime, "cannot activate GraniteTime when it is not scheduled")
 	for s.L2Unsafe().Time < *s.RollupCfg.GraniteTime {
-		s.ActL2StartBlock(t)
-		s.ActL2EndBlock(t)
+		s.ActL2EmptyBlock(t)
 	}
 }
 
 func (s *L2Sequencer) ActBuildL2ToHolocene(t Testing) {
 	require.NotNil(t, s.RollupCfg.HoloceneTime, "cannot activate HoloceneTime when it is not scheduled")
 	for s.L2Unsafe().Time < *s.RollupCfg.HoloceneTime {
-		s.ActL2StartBlock(t)
-		s.ActL2EndBlock(t)
+		s.ActL2EmptyBlock(t)
 	}
 }

op-e2e/actions/proofs/helpers/matrix.go

@@ -89,9 +89,12 @@ var (
 	Granite  = &Hardfork{Name: "Granite", Precedence: 6}
 	Holocene = &Hardfork{Name: "Holocene", Precedence: 7}
 )
-var Hardforks = ForkMatrix{Regolith, Canyon, Delta, Ecotone, Fjord, Granite, Holocene}
 
-var LatestForkOnly = ForkMatrix{Hardforks[len(Hardforks)-1]}
+var (
+	Hardforks      = ForkMatrix{Regolith, Canyon, Delta, Ecotone, Fjord, Granite, Holocene}
+	LatestFork     = Hardforks[len(Hardforks)-1]
+	LatestForkOnly = ForkMatrix{LatestFork}
+)
 
 func NewForkMatrix(forks ...*Hardfork) ForkMatrix {
 	return append(ForkMatrix{}, forks...)

op-e2e/actions/proofs/sequence_window_expiry_test.go

@@ -132,17 +132,18 @@ func Test_ProgramAction_SequenceWindowExpired(gt *testing.T) {
 	matrix := helpers.NewMatrix[any]()
 	defer matrix.Run(gt)
 
+	forks := helpers.ForkMatrix{helpers.Granite, helpers.LatestFork}
 	matrix.AddTestCase(
 		"HonestClaim",
 		nil,
-		helpers.LatestForkOnly,
+		forks,
 		runSequenceWindowExpireTest,
 		helpers.ExpectNoError(),
 	)
 	matrix.AddTestCase(
 		"JunkClaim",
 		nil,
-		helpers.LatestForkOnly,
+		forks,
 		runSequenceWindowExpireTest,
 		helpers.ExpectError(claim.ErrClaimNotValid),
 		helpers.WithL2Claim(common.HexToHash("0xdeadbeef")),
@@ -150,14 +151,14 @@ func Test_ProgramAction_SequenceWindowExpired(gt *testing.T) {
 	matrix.AddTestCase(
 		"ChannelCloseAfterWindowExpiry-HonestClaim",
 		nil,
-		helpers.LatestForkOnly,
+		forks,
 		runSequenceWindowExpire_ChannelCloseAfterWindowExpiry_Test,
 		helpers.ExpectNoError(),
 	)
 	matrix.AddTestCase(
 		"ChannelCloseAfterWindowExpiry-JunkClaim",
 		nil,
-		helpers.LatestForkOnly,
+		forks,
 		runSequenceWindowExpire_ChannelCloseAfterWindowExpiry_Test,
 		helpers.ExpectError(claim.ErrClaimNotValid),
 		helpers.WithL2Claim(common.HexToHash("0xdeadbeef")),

op-e2e/actions/upgrades/helpers/config.go

@@ -8,7 +8,6 @@ import (
 // ApplyDeltaTimeOffset adjusts fork configuration to not conflict with the delta overrides
 func ApplyDeltaTimeOffset(dp *e2eutils.DeployParams, deltaTimeOffset *hexutil.Uint64) {
 	dp.DeployConfig.L2GenesisDeltaTimeOffset = deltaTimeOffset
-	dp.DeployConfig.L2GenesisGraniteTimeOffset = nil
 	// configure Ecotone to not be before Delta accidentally
 	if dp.DeployConfig.L2GenesisEcotoneTimeOffset != nil {
 		if deltaTimeOffset == nil {
@@ -17,6 +16,7 @@ func ApplyDeltaTimeOffset(dp *e2eutils.DeployParams, deltaTimeOffset *hexutil.Ui
 			dp.DeployConfig.L2GenesisEcotoneTimeOffset = deltaTimeOffset
 		}
 	}
+
 	// configure Fjord to not be before Delta accidentally
 	if dp.DeployConfig.L2GenesisFjordTimeOffset != nil {
 		if deltaTimeOffset == nil {
@@ -25,4 +25,22 @@ func ApplyDeltaTimeOffset(dp *e2eutils.DeployParams, deltaTimeOffset *hexutil.Ui
 			dp.DeployConfig.L2GenesisFjordTimeOffset = deltaTimeOffset
 		}
 	}
+
+	// configure Granite to not be before Delta accidentally
+	if dp.DeployConfig.L2GenesisGraniteTimeOffset != nil {
+		if deltaTimeOffset == nil {
+			dp.DeployConfig.L2GenesisGraniteTimeOffset = nil
+		} else if *dp.DeployConfig.L2GenesisGraniteTimeOffset < *deltaTimeOffset {
+			dp.DeployConfig.L2GenesisGraniteTimeOffset = deltaTimeOffset
+		}
+	}
+
+	// configure Holocene to not be before Delta accidentally
+	if dp.DeployConfig.L2GenesisHoloceneTimeOffset != nil {
+		if deltaTimeOffset == nil {
+			dp.DeployConfig.L2GenesisHoloceneTimeOffset = nil
+		} else if *dp.DeployConfig.L2GenesisHoloceneTimeOffset < *deltaTimeOffset {
+			dp.DeployConfig.L2GenesisHoloceneTimeOffset = deltaTimeOffset
+		}
+	}
 }

op-e2e/actions/upgrades/holocene_fork_test.go

+package upgrades
+
+import (
+	"testing"
+
+	"github.com/ethereum-optimism/optimism/op-e2e/actions/helpers"
+	"github.com/ethereum-optimism/optimism/op-e2e/system/e2esys"
+	"github.com/ethereum-optimism/optimism/op-node/rollup"
+	"github.com/ethereum-optimism/optimism/op-service/testlog"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHoloceneActivationAtGenesis(gt *testing.T) {
+	t := helpers.NewDefaultTesting(gt)
+	env := helpers.SetupEnv(t, helpers.WithActiveGenesisFork(rollup.Holocene))
+
+	// Start op-nodes
+	env.Seq.ActL2PipelineFull(t)
+	env.Verifier.ActL2PipelineFull(t)
+
+	// Verify Holocene is active at genesis
+	l2Head := env.Seq.L2Unsafe()
+	require.NotZero(t, l2Head.Hash)
+	require.True(t, env.SetupData.RollupCfg.IsHolocene(l2Head.Time), "Holocene should be active at genesis")
+
+	// build empty L1 block
+	env.Miner.ActEmptyBlock(t)
+
+	// Build L2 chain and advance safe head
+	env.Seq.ActL1HeadSignal(t)
+	env.Seq.ActBuildToL1Head(t)
+
+	// verify in logs that correct stage got activated
+	recs := env.Logs.FindLogs(testlog.NewMessageContainsFilter("activating Holocene stage during reset"), testlog.NewAttributesFilter("role", e2esys.RoleSeq))
+	require.Len(t, recs, 2)
+	recs = env.Logs.FindLogs(testlog.NewMessageContainsFilter("activating Holocene stage during reset"), testlog.NewAttributesFilter("role", e2esys.RoleVerif))
+	require.Len(t, recs, 2)
+
+	env.ActBatchSubmitAllAndMine(t)
+
+	// verifier picks up the L2 chain that was submitted
+	env.Verifier.ActL1HeadSignal(t)
+	env.Verifier.ActL2PipelineFull(t)
+	require.Equal(t, env.Verifier.L2Safe(), env.Seq.L2Unsafe(), "verifier syncs from sequencer via L1")
+	require.NotEqual(t, env.Seq.L2Safe(), env.Seq.L2Unsafe(), "sequencer has not processed L1 yet")
+}
+
+func TestHoloceneLateActivationAndReset(gt *testing.T) {
+	t := helpers.NewDefaultTesting(gt)
+	holoceneOffset := uint64(24)
+	env := helpers.SetupEnv(t, helpers.WithActiveFork(rollup.Holocene, holoceneOffset))
+
+	requireHoloceneTransformationLogs := func(role string, expNumLogs int) {
+		recs := env.Logs.FindLogs(testlog.NewMessageContainsFilter("transforming to Holocene"), testlog.NewAttributesFilter("role", role))
+		require.Len(t, recs, expNumLogs)
+		if expNumLogs > 0 {
+			fqRecs := env.Logs.FindLogs(testlog.NewMessageFilter("FrameQueue: resetting with Holocene activation"), testlog.NewAttributesFilter("role", role))
+			require.Len(t, fqRecs, 1)
+		}
+	}
+
+	requirePreHoloceneActivationLogs := func(role string, expNumLogs int) {
+		recs := env.Logs.FindLogs(testlog.NewMessageContainsFilter("activating pre-Holocene stage during reset"), testlog.NewAttributesFilter("role", role))
+		require.Len(t, recs, expNumLogs)
+	}
+
+	// Start op-nodes
+	env.Seq.ActL2PipelineFull(t)
+	env.Verifier.ActL2PipelineFull(t)
+
+	// Verify Holocene is not active at genesis yet
+	l2Head := env.Seq.L2Unsafe()
+	require.NotZero(t, l2Head.Hash)
+	require.True(t, env.SetupData.RollupCfg.IsGranite(l2Head.Time), "Granite should be active at genesis")
+	require.False(t, env.SetupData.RollupCfg.IsHolocene(l2Head.Time), "Holocene should not be active at genesis")
+
+	requirePreHoloceneActivationLogs(e2esys.RoleSeq, 2)
+	requirePreHoloceneActivationLogs(e2esys.RoleVerif, 2)
+	// Verify no stage transformations took place yet
+	requireHoloceneTransformationLogs(e2esys.RoleSeq, 0)
+	requireHoloceneTransformationLogs(e2esys.RoleVerif, 0)
+
+	env.Seq.ActL2EmptyBlock(t)
+	l1PreHolocene := env.ActBatchSubmitAllAndMine(t)
+	require.False(t, env.SetupData.RollupCfg.IsHolocene(l1PreHolocene.Time()),
+		"Holocene should not be active at the first L1 inclusion block")
+
+	// Build a few L2 blocks. We only need the L1 inclusion to advance past Holocene and Holocene
+	// shouldn't activate with L2 time.
+	env.Seq.ActBuildL2ToHolocene(t)
+
+	// verify in logs that stage transformations hasn't happened yet, activates by L1 inclusion block
+	requireHoloceneTransformationLogs(e2esys.RoleSeq, 0)
+	requireHoloceneTransformationLogs(e2esys.RoleVerif, 0)
+
+	// Submit L2
+	l1Head := env.ActBatchSubmitAllAndMine(t)
+	require.True(t, env.SetupData.RollupCfg.IsHolocene(l1Head.Time()))
+
+	// verifier picks up the L2 chain that was submitted
+	env.Verifier.ActL1HeadSignal(t)
+	env.Verifier.ActL2PipelineFull(t)
+	l2Safe := env.Verifier.L2Safe()
+	require.Equal(t, l2Safe, env.Seq.L2Unsafe(), "verifier syncs from sequencer via L1")
+	require.NotEqual(t, env.Seq.L2Safe(), env.Seq.L2Unsafe(), "sequencer has not processed L1 yet")
+	require.True(t, env.SetupData.RollupCfg.IsHolocene(l2Safe.Time), "Holocene should now be active")
+	requireHoloceneTransformationLogs(e2esys.RoleSeq, 0)
+	requireHoloceneTransformationLogs(e2esys.RoleVerif, 2)
+
+	// sequencer also picks up L2 safe chain
+	env.Seq.ActL1HeadSignal(t)
+	env.Seq.ActL2PipelineFull(t)
+	requireHoloceneTransformationLogs(e2esys.RoleSeq, 2)
+	require.Equal(t, env.Seq.L2Safe(), env.Seq.L2Unsafe(), "sequencer has processed L1")
+
+	// reorg L1 without batch submission
+	env.Miner.ActL1RewindToParent(t)
+	env.Miner.ActEmptyBlock(t)
+	env.Miner.ActEmptyBlock(t)
+
+	env.Seq.ActL1HeadSignal(t)
+	env.Verifier.ActL1HeadSignal(t)
+	env.Seq.ActL2PipelineFull(t)
+	env.Verifier.ActL2PipelineFull(t)
+
+	// duplicate activation logs
+	requirePreHoloceneActivationLogs(e2esys.RoleSeq, 4)
+	requirePreHoloceneActivationLogs(e2esys.RoleVerif, 4)
+}

op-node/rollup/chain_spec.go

 package rollup
 
 import (
+	"fmt"
 	"math/big"
 
 	"github.com/ethereum-optimism/optimism/op-node/params"
@@ -41,19 +42,47 @@ const (
 	Granite  ForkName = "granite"
 	Holocene ForkName = "holocene"
 	Interop  ForkName = "interop"
+	// ADD NEW FORKS TO AllForks BELOW!
 	None ForkName = "none"
 )
 
-var nextFork = map[ForkName]ForkName{
-	Bedrock:  Regolith,
-	Regolith: Canyon,
-	Canyon:   Delta,
-	Delta:    Ecotone,
-	Ecotone:  Fjord,
-	Fjord:    Granite,
-	Granite:  Holocene,
-	Holocene: Interop,
-	Interop:  None,
+var AllForks = []ForkName{
+	Bedrock,
+	Regolith,
+	Canyon,
+	Delta,
+	Ecotone,
+	Fjord,
+	Granite,
+	Holocene,
+	Interop,
+	// ADD NEW FORKS HERE!
+}
+
+func ForksFrom(fork ForkName) []ForkName {
+	for i, f := range AllForks {
+		if f == fork {
+			return AllForks[i:]
+		}
+	}
+	panic(fmt.Sprintf("invalid fork: %s", fork))
+}
+
+var nextFork = func() map[ForkName]ForkName {
+	m := make(map[ForkName]ForkName, len(AllForks))
+	for i, f := range AllForks {
+		if i == len(AllForks)-1 {
+			m[f] = None
+			break
+		}
+		m[f] = AllForks[i+1]
+	}
+	return m
+}()
+
+func IsValidFork(fork ForkName) bool {
+	_, ok := nextFork[fork]
+	return ok
 }
 
 type ChainSpec struct {
@@ -80,6 +109,11 @@ func (s *ChainSpec) IsCanyon(t uint64) bool {
 	return s.config.IsCanyon(t)
 }
 
+// IsHolocene returns true if t >= holocene_time
+func (s *ChainSpec) IsHolocene(t uint64) bool {
+	return s.config.IsHolocene(t)
+}
+
 // MaxChannelBankSize returns the maximum number of bytes the can allocated inside the channel bank
 // before pruning occurs at the given timestamp.
 func (s *ChainSpec) MaxChannelBankSize(t uint64) uint64 {

op-node/rollup/derive/attributes_queue.go

@@ -39,12 +39,18 @@ type AttributesQueue struct {
 	log          log.Logger
 	config       *rollup.Config
 	builder      AttributesBuilder
-	prev         *BatchQueue
+	prev         SingularBatchProvider
 	batch        *SingularBatch
 	isLastInSpan bool
 }
 
-func NewAttributesQueue(log log.Logger, cfg *rollup.Config, builder AttributesBuilder, prev *BatchQueue) *AttributesQueue {
+type SingularBatchProvider interface {
+	ResettableStage
+	Origin() eth.L1BlockRef
+	NextBatch(context.Context, eth.L2BlockRef) (*SingularBatch, bool, error)
+}
+
+func NewAttributesQueue(log log.Logger, cfg *rollup.Config, builder AttributesBuilder, prev SingularBatchProvider) *AttributesQueue {
 	return &AttributesQueue{
 		log:     log,
 		config:  cfg,

op-node/rollup/derive/batch_mux.go

+package derive
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/ethereum-optimism/optimism/op-node/rollup"
+	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum/go-ethereum/log"
+	"golang.org/x/exp/slices"
+)
+
+// BatchMux multiplexes between different batch stages.
+// Stages are swapped on demand during Reset calls, or explicitly with Transform.
+// It currently chooses the BatchQueue pre-Holocene and the BatchStage post-Holocene.
+type BatchMux struct {
+	log  log.Logger
+	cfg  *rollup.Config
+	prev NextBatchProvider
+	l2   SafeBlockFetcher
+
+	// embedded active stage
+	SingularBatchProvider
+}
+
+var _ SingularBatchProvider = (*BatchMux)(nil)
+
+// NewBatchMux returns an uninitialized BatchMux. Reset has to be called before
+// calling other methods, to activate the right stage for a given L1 origin.
+func NewBatchMux(lgr log.Logger, cfg *rollup.Config, prev NextBatchProvider, l2 SafeBlockFetcher) *BatchMux {
+	return &BatchMux{log: lgr, cfg: cfg, prev: prev, l2: l2}
+}
+
+func (b *BatchMux) Reset(ctx context.Context, base eth.L1BlockRef, sysCfg eth.SystemConfig) error {
+	// TODO(12490): change to a switch over b.cfg.ActiveFork(base.Time)
+	switch {
+	default:
+		if _, ok := b.SingularBatchProvider.(*BatchQueue); !ok {
+			b.log.Info("BatchMux: activating pre-Holocene stage during reset", "origin", base)
+			b.SingularBatchProvider = NewBatchQueue(b.log, b.cfg, b.prev, b.l2)
+		}
+	case b.cfg.IsHolocene(base.Time):
+		if _, ok := b.SingularBatchProvider.(*BatchStage); !ok {
+			b.log.Info("BatchMux: activating Holocene stage during reset", "origin", base)
+			b.SingularBatchProvider = NewBatchStage(b.log, b.cfg, b.prev, b.l2)
+		}
+	}
+	return b.SingularBatchProvider.Reset(ctx, base, sysCfg)
+}
+
+func (b *BatchMux) Transform(f rollup.ForkName) {
+	switch f {
+	case rollup.Holocene:
+		b.TransformHolocene()
+	}
+}
+
+func (b *BatchMux) TransformHolocene() {
+	switch bp := b.SingularBatchProvider.(type) {
+	case *BatchQueue:
+		b.log.Info("BatchMux: transforming to Holocene stage")
+		bs := NewBatchStage(b.log, b.cfg, b.prev, b.l2)
+		// Even though any ongoing span batch or queued batches are dropped at Holocene activation, the
+		// post-Holocene batch stage still needs access to the collected l1Blocks pre-Holocene because
+		// the first Holocene channel will contain pre-Holocene batches.
+		bs.l1Blocks = slices.Clone(bp.l1Blocks)
+		bs.origin = bp.origin
+		b.SingularBatchProvider = bs
+	case *BatchStage:
+		// Even if the pipeline is Reset to the activation block, the previous origin will be the
+		// same, so transfromStages isn't called.
+		panic(fmt.Sprintf("Holocene BatchStage already active, old origin: %v", bp.Origin()))
+	default:
+		panic(fmt.Sprintf("unknown batch stage type: %T", bp))
+	}
+}

op-node/rollup/derive/batch_mux_test.go

+package derive
+
+import (
+	"context"
+	"io"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum-optimism/optimism/op-node/rollup"
+	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum-optimism/optimism/op-service/testlog"
+)
+
+func TestBatchMux_LaterHolocene(t *testing.T) {
+	log := testlog.Logger(t, log.LevelTrace)
+	ctx := context.Background()
+	l1A := eth.L1BlockRef{Time: 0, Hash: common.Hash{0xaa}}
+	l1B := eth.L1BlockRef{Time: 12, Hash: common.Hash{0xbb}}
+	cfg := &rollup.Config{
+		HoloceneTime: &l1B.Time,
+	}
+	b := NewBatchMux(log, cfg, nil, nil)
+
+	require.Nil(t, b.SingularBatchProvider)
+
+	err := b.Reset(ctx, l1A, eth.SystemConfig{})
+	require.Equal(t, io.EOF, err)
+	require.IsType(t, new(BatchQueue), b.SingularBatchProvider)
+	require.Equal(t, l1A, b.SingularBatchProvider.(*BatchQueue).origin)
+
+	b.Transform(rollup.Holocene)
+	require.IsType(t, new(BatchStage), b.SingularBatchProvider)
+	require.Equal(t, l1A, b.SingularBatchProvider.(*BatchStage).origin)
+
+	err = b.Reset(ctx, l1B, eth.SystemConfig{})
+	require.Equal(t, io.EOF, err)
+	require.IsType(t, new(BatchStage), b.SingularBatchProvider)
+	require.Equal(t, l1B, b.SingularBatchProvider.(*BatchStage).origin)
+
+	err = b.Reset(ctx, l1A, eth.SystemConfig{})
+	require.Equal(t, io.EOF, err)
+	require.IsType(t, new(BatchQueue), b.SingularBatchProvider)
+	require.Equal(t, l1A, b.SingularBatchProvider.(*BatchQueue).origin)
+}
+
+func TestBatchMux_ActiveHolocene(t *testing.T) {
+	log := testlog.Logger(t, log.LevelTrace)
+	ctx := context.Background()
+	l1A := eth.L1BlockRef{Time: 42, Hash: common.Hash{0xaa}}
+	cfg := &rollup.Config{
+		HoloceneTime: &l1A.Time,
+	}
+	// without the fake input, the panic check later would panic because of the Origin() call
+	prev := &fakeBatchQueueInput{origin: l1A}
+	b := NewBatchMux(log, cfg, prev, nil)
+
+	require.Nil(t, b.SingularBatchProvider)
+
+	err := b.Reset(ctx, l1A, eth.SystemConfig{})
+	require.Equal(t, io.EOF, err)
+	require.IsType(t, new(BatchStage), b.SingularBatchProvider)
+	require.Equal(t, l1A, b.SingularBatchProvider.(*BatchStage).origin)
+
+	require.Panics(t, func() { b.Transform(rollup.Holocene) })
+}

op-node/rollup/derive/batch_queue.go

@@ -49,6 +49,8 @@ type baseBatchStage struct {
 	log    log.Logger
 	config *rollup.Config
 	prev   NextBatchProvider
+	l2     SafeBlockFetcher
+
 	origin eth.L1BlockRef
 
 	// l1Blocks contains consecutive eth.L1BlockRef sorted by time.
@@ -61,8 +63,6 @@ type baseBatchStage struct {
 
 	// nextSpan is cached SingularBatches derived from SpanBatch
 	nextSpan []*SingularBatch
-
-	l2 SafeBlockFetcher
 }
 
 func newBaseBatchStage(log log.Logger, cfg *rollup.Config, prev NextBatchProvider, l2 SafeBlockFetcher) baseBatchStage {
@@ -86,11 +86,6 @@ func (bs *baseBatchStage) Log() log.Logger {
 	}
 }
 
-type SingularBatchProvider interface {
-	ResettableStage
-	NextBatch(context.Context, eth.L2BlockRef) (*SingularBatch, bool, error)
-}
-
 // BatchQueue contains a set of batches for every L1 block.
 // L1 blocks are contiguous and this does not support reorgs.
 type BatchQueue struct {
@@ -262,10 +257,10 @@ func (bs *baseBatchStage) reset(base eth.L1BlockRef) {
 	// Copy over the Origin from the next stage
 	// It is set in the engine queue (two stages away) such that the L2 Safe Head origin is the progress
 	bs.origin = base
+	bs.l1Blocks = bs.l1Blocks[:0]
 	// Include the new origin as an origin to build on
 	// Note: This is only for the initialization case. During normal resets we will later
 	// throw out this block.
-	bs.l1Blocks = bs.l1Blocks[:0]
 	bs.l1Blocks = append(bs.l1Blocks, base)
 	bs.nextSpan = bs.nextSpan[:0]
 }

op-node/rollup/derive/batch_stage.go

@@ -15,6 +15,8 @@ type BatchStage struct {
 	baseBatchStage
 }
 
+var _ SingularBatchProvider = (*BatchStage)(nil)
+
 func NewBatchStage(log log.Logger, cfg *rollup.Config, prev NextBatchProvider, l2 SafeBlockFetcher) *BatchStage {
 	return &BatchStage{baseBatchStage: newBaseBatchStage(log, cfg, prev, l2)}
 }
@@ -68,7 +70,8 @@ func (bs *BatchStage) NextBatch(ctx context.Context, parent eth.L2BlockRef) (*Si
 		// We only consider empty batch generation after we've drained all batches from the local
 		// span batch queue and the previous stage.
 		empty, err := bs.deriveNextEmptyBatch(ctx, true, parent)
-		return empty, false, err
+		// An empty batch always advances the safe head.
+		return empty, true, err
 	} else if err != nil {
 		return nil, false, err
 	}

op-node/rollup/derive/channel_assembler.go

@@ -20,16 +20,16 @@ type ChannelAssembler struct {
 	prev NextFrameProvider
 }
 
-var _ ResettableStage = (*ChannelAssembler)(nil)
+var _ RawChannelProvider = (*ChannelAssembler)(nil)
 
 type ChannelStageSpec interface {
 	ChannelTimeout(t uint64) uint64
 	MaxRLPBytesPerChannel(t uint64) uint64
 }
 
-// NewChannelStage creates a Holocene ChannelStage.
-// It must only be used for derivation from Holocene activation.
-func NewChannelStage(log log.Logger, spec ChannelStageSpec, prev NextFrameProvider, m Metrics) *ChannelAssembler {
+// NewChannelAssembler creates the Holocene channel stage.
+// It must only be used for derivation from Holocene origins.
+func NewChannelAssembler(log log.Logger, spec ChannelStageSpec, prev NextFrameProvider, m Metrics) *ChannelAssembler {
 	return &ChannelAssembler{
 		log:     log,
 		spec:    spec,
@@ -60,7 +60,7 @@ func (ca *ChannelAssembler) channelTimedOut() bool {
 	return ca.channel.OpenBlockNumber()+ca.spec.ChannelTimeout(ca.Origin().Time) < ca.Origin().Number
 }
 
-func (ca *ChannelAssembler) NextData(ctx context.Context) ([]byte, error) {
+func (ca *ChannelAssembler) NextRawChannel(ctx context.Context) ([]byte, error) {
 	if ca.channel != nil && ca.channelTimedOut() {
 		ca.metrics.RecordChannelTimedOut()
 		ca.resetChannel()

op-node/rollup/derive/channel_assembler_test.go

@@ -110,11 +110,11 @@ func TestChannelStage_NextData(t *testing.T) {
 
 				MaxRLPBytesPerChannelOverride: tc.rlpOverride,
 			}
-			cs := NewChannelStage(lgr, spec, fq, metrics.NoopMetrics)
+			cs := NewChannelAssembler(lgr, spec, fq, metrics.NoopMetrics)
 
 			for i, fs := range tc.frames {
 				fq.AddFrames(fs...)
-				data, err := cs.NextData(context.Background())
+				data, err := cs.NextRawChannel(context.Background())
 				require.Equal(t, tc.expData[i], string(data))
 				require.ErrorIs(t, tc.expErr[i], err)
 				// invariant: never holds a ready channel
@@ -129,7 +129,7 @@ func TestChannelStage_NextData(t *testing.T) {
 			}
 
 			// final call should always be io.EOF after exhausting frame queue
-			data, err := cs.NextData(context.Background())
+			data, err := cs.NextRawChannel(context.Background())
 			require.Nil(t, data)
 			require.Equal(t, io.EOF, err)
 		})
@@ -141,10 +141,10 @@ func TestChannelStage_NextData_Timeout(t *testing.T) {
 	fq := &fakeChannelBankInput{}
 	lgr := testlog.Logger(t, slog.LevelWarn)
 	spec := rollup.NewChainSpec(&rollup.Config{GraniteTime: ptr(uint64(0))}) // const channel timeout
-	cs := NewChannelStage(lgr, spec, fq, metrics.NoopMetrics)
+	cs := NewChannelAssembler(lgr, spec, fq, metrics.NoopMetrics)
 
 	fq.AddFrames("a:0:foo")
-	data, err := cs.NextData(context.Background())
+	data, err := cs.NextRawChannel(context.Background())
 	require.Nil(data)
 	require.Equal(io.EOF, err)
 	require.NotNil(cs.channel)
@@ -153,7 +153,7 @@ func TestChannelStage_NextData_Timeout(t *testing.T) {
 	// move close to timeout
 	fq.origin.Number = spec.ChannelTimeout(0)
 	fq.AddFrames("a:1:bar")
-	data, err = cs.NextData(context.Background())
+	data, err = cs.NextRawChannel(context.Background())
 	require.Nil(data)
 	require.Equal(io.EOF, err)
 	require.NotNil(cs.channel)
@@ -162,7 +162,7 @@ func TestChannelStage_NextData_Timeout(t *testing.T) {
 	// timeout channel by moving origin past timeout
 	fq.origin.Number = spec.ChannelTimeout(0) + 1
 	fq.AddFrames("a:2:baz!")
-	data, err = cs.NextData(context.Background())
+	data, err = cs.NextRawChannel(context.Background())
 	require.Nil(data)
 	require.Equal(io.EOF, err)
 	require.Nil(cs.channel)

op-node/rollup/derive/channel_bank.go

@@ -40,13 +40,13 @@ type ChannelBank struct {
 	prev NextFrameProvider
 }
 
-var _ ResettableStage = (*ChannelBank)(nil)
+var _ RawChannelProvider = (*ChannelBank)(nil)
 
 // NewChannelBank creates a ChannelBank, which should be Reset(origin) before use.
-func NewChannelBank(log log.Logger, cfg *rollup.Config, prev NextFrameProvider, m Metrics) *ChannelBank {
+func NewChannelBank(log log.Logger, spec *rollup.ChainSpec, prev NextFrameProvider, m Metrics) *ChannelBank {
 	return &ChannelBank{
 		log:          log,
-		spec:         rollup.NewChainSpec(cfg),
+		spec:         spec,
 		metrics:      m,
 		channels:     make(map[ChannelID]*Channel),
 		channelQueue: make([]ChannelID, 0, 10),
@@ -170,12 +170,12 @@ func (cb *ChannelBank) tryReadChannelAtIndex(i int) (data []byte, err error) {
 	return data, nil
 }
 
-// NextData pulls the next piece of data from the channel bank.
+// NextRawChannel pulls the next piece of data from the channel bank.
 // Note that it attempts to pull data out of the channel bank prior to
 // loading data in (unlike most other stages). This is to ensure maintain
 // consistency around channel bank pruning which depends upon the order
 // of operations.
-func (cb *ChannelBank) NextData(ctx context.Context) ([]byte, error) {
+func (cb *ChannelBank) NextRawChannel(ctx context.Context) ([]byte, error) {
 	// Do the read from the channel bank first
 	data, err := cb.Read()
 	if err == io.EOF {

op-node/rollup/derive/channel_bank_test.go

@@ -106,32 +106,31 @@ func TestChannelBankSimple(t *testing.T) {
 	input.AddFrames("a:0:first", "a:2:third!")
 	input.AddFrames("a:1:second")
 
-	cfg := &rollup.Config{ChannelTimeoutBedrock: 10}
-
-	cb := NewChannelBank(testlog.Logger(t, log.LevelCrit), cfg, input, metrics.NoopMetrics)
+	spec := rollup.NewChainSpec(&rollup.Config{ChannelTimeoutBedrock: 10})
+	cb := NewChannelBank(testlog.Logger(t, log.LevelCrit), spec, input, metrics.NoopMetrics)
 
 	// Load the first frame
-	out, err := cb.NextData(context.Background())
+	out, err := cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load the third frame
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load the second frame
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Pull out the channel data
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, err)
 	require.Equal(t, "firstsecondthird", string(out))
 
 	// No more data
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, out)
 	require.Equal(t, io.EOF, err)
 }
@@ -149,52 +148,51 @@ func TestChannelBankInterleavedPreCanyon(t *testing.T) {
 	input.AddFrames("b:0:premiere")
 	input.AddFrames("a:1:second")
 
-	cfg := &rollup.Config{ChannelTimeoutBedrock: 10, CanyonTime: nil}
-
-	cb := NewChannelBank(testlog.Logger(t, log.LevelCrit), cfg, input, metrics.NoopMetrics)
+	spec := rollup.NewChainSpec(&rollup.Config{ChannelTimeoutBedrock: 10})
+	cb := NewChannelBank(testlog.Logger(t, log.LevelCrit), spec, input, metrics.NoopMetrics)
 
 	// Load a:0
-	out, err := cb.NextData(context.Background())
+	out, err := cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load b:2
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load b:1
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load a:2
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load b:0 & Channel b is complete, but channel a was opened first
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load a:1
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Pull out the channel a
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, err)
 	require.Equal(t, "firstsecondthird", string(out))
 
 	// Pull out the channel b
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, err)
 	require.Equal(t, "premieredeuxtrois", string(out))
 
 	// No more data
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, out)
 	require.Equal(t, io.EOF, err)
 }
@@ -213,52 +211,51 @@ func TestChannelBankInterleaved(t *testing.T) {
 	input.AddFrames("a:1:second")
 
 	ct := uint64(0)
-	cfg := &rollup.Config{ChannelTimeoutBedrock: 10, CanyonTime: &ct}
-
-	cb := NewChannelBank(testlog.Logger(t, log.LevelCrit), cfg, input, metrics.NoopMetrics)
+	spec := rollup.NewChainSpec(&rollup.Config{ChannelTimeoutBedrock: 10, CanyonTime: &ct})
+	cb := NewChannelBank(testlog.Logger(t, log.LevelCrit), spec, input, metrics.NoopMetrics)
 
 	// Load a:0
-	out, err := cb.NextData(context.Background())
+	out, err := cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load b:2
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load b:1
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load a:2
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load b:0 & Channel b is complete. Channel a was opened first but isn't ready
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Pull out the channel b because it's ready first.
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, err)
 	require.Equal(t, "premieredeuxtrois", string(out))
 
 	// Load a:1
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Pull out the channel a
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, err)
 	require.Equal(t, "firstsecondthird", string(out))
 
 	// No more data
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, out)
 	require.Equal(t, io.EOF, err)
 }
@@ -272,40 +269,39 @@ func TestChannelBankDuplicates(t *testing.T) {
 	input.AddFrames("a:0:altfirst", "a:2:altthird!")
 	input.AddFrames("a:1:second")
 
-	cfg := &rollup.Config{ChannelTimeoutBedrock: 10}
-
-	cb := NewChannelBank(testlog.Logger(t, log.LevelCrit), cfg, input, metrics.NoopMetrics)
+	spec := rollup.NewChainSpec(&rollup.Config{ChannelTimeoutBedrock: 10})
+	cb := NewChannelBank(testlog.Logger(t, log.LevelCrit), spec, input, metrics.NoopMetrics)
 
 	// Load the first frame
-	out, err := cb.NextData(context.Background())
+	out, err := cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load the third frame
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load the duplicate frames
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Load the second frame
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.ErrorIs(t, err, NotEnoughData)
 	require.Equal(t, []byte(nil), out)
 
 	// Pull out the channel data. Expect to see the original set & not the duplicates
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, err)
 	require.Equal(t, "firstsecondthird", string(out))
 
 	// No more data
-	out, err = cb.NextData(context.Background())
+	out, err = cb.NextRawChannel(context.Background())
 	require.Nil(t, out)
 	require.Equal(t, io.EOF, err)
 }

op-node/rollup/derive/channel_in_reader.go

@@ -21,7 +21,7 @@ type ChannelInReader struct {
 	spec        *rollup.ChainSpec
 	cfg         *rollup.Config
 	nextBatchFn func() (*BatchData, error)
-	prev        *ChannelBank
+	prev        RawChannelProvider
 	metrics     Metrics
 }
 
@@ -30,8 +30,14 @@ var (
 	_ ChannelFlusher  = (*ChannelInReader)(nil)
 )
 
+type RawChannelProvider interface {
+	ResettableStage
+	Origin() eth.L1BlockRef
+	NextRawChannel(ctx context.Context) ([]byte, error)
+}
+
 // NewChannelInReader creates a ChannelInReader, which should be Reset(origin) before use.
-func NewChannelInReader(cfg *rollup.Config, log log.Logger, prev *ChannelBank, metrics Metrics) *ChannelInReader {
+func NewChannelInReader(cfg *rollup.Config, log log.Logger, prev RawChannelProvider, metrics Metrics) *ChannelInReader {
 	return &ChannelInReader{
 		spec:    rollup.NewChainSpec(cfg),
 		cfg:     cfg,
@@ -68,7 +74,7 @@ func (cr *ChannelInReader) NextChannel() {
 // It will return a temporary error if it needs to be called again to advance some internal state.
 func (cr *ChannelInReader) NextBatch(ctx context.Context) (Batch, error) {
 	if cr.nextBatchFn == nil {
-		if data, err := cr.prev.NextData(ctx); err == io.EOF {
+		if data, err := cr.prev.NextRawChannel(ctx); err == io.EOF {
 			return nil, io.EOF
 		} else if err != nil {
 			return nil, err

op-node/rollup/derive/channel_mux.go

+package derive
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/ethereum-optimism/optimism/op-node/rollup"
+	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum/go-ethereum/log"
+)
+
+// ChannelMux multiplexes between different channel stages.
+// Stages are swapped on demand during Reset calls, or explicitly with Transform.
+// It currently chooses the ChannelBank pre-Holocene and the ChannelAssembler post-Holocene.
+type ChannelMux struct {
+	log  log.Logger
+	spec *rollup.ChainSpec
+	prev NextFrameProvider
+	m    Metrics
+
+	// embedded active stage
+	RawChannelProvider
+}
+
+var _ RawChannelProvider = (*ChannelMux)(nil)
+
+// NewChannelMux returns a ChannelMux with the ChannelBank as activated stage. Reset has to be called before
+// calling other methods, to activate the right stage for a given L1 origin.
+func NewChannelMux(log log.Logger, spec *rollup.ChainSpec, prev NextFrameProvider, m Metrics) *ChannelMux {
+	return &ChannelMux{
+		log:  log,
+		spec: spec,
+		prev: prev,
+		m:    m,
+	}
+}
+
+func (c *ChannelMux) Reset(ctx context.Context, base eth.L1BlockRef, sysCfg eth.SystemConfig) error {
+	// TODO(12490): change to a switch over c.cfg.ActiveFork(base.Time)
+	switch {
+	default:
+		if _, ok := c.RawChannelProvider.(*ChannelBank); !ok {
+			c.log.Info("ChannelMux: activating pre-Holocene stage during reset", "origin", base)
+			c.RawChannelProvider = NewChannelBank(c.log, c.spec, c.prev, c.m)
+		}
+	case c.spec.IsHolocene(base.Time):
+		if _, ok := c.RawChannelProvider.(*ChannelAssembler); !ok {
+			c.log.Info("ChannelMux: activating Holocene stage during reset", "origin", base)
+			c.RawChannelProvider = NewChannelAssembler(c.log, c.spec, c.prev, c.m)
+		}
+	}
+	return c.RawChannelProvider.Reset(ctx, base, sysCfg)
+}
+
+func (c *ChannelMux) Transform(f rollup.ForkName) {
+	switch f {
+	case rollup.Holocene:
+		c.TransformHolocene()
+	}
+}
+
+func (c *ChannelMux) TransformHolocene() {
+	switch cp := c.RawChannelProvider.(type) {
+	case *ChannelBank:
+		c.log.Info("ChannelMux: transforming to Holocene stage")
+		c.RawChannelProvider = NewChannelAssembler(c.log, c.spec, c.prev, c.m)
+	case *ChannelAssembler:
+		// Even if the pipeline is Reset to the activation block, the previous origin will be the
+		// same, so transfromStages isn't called.
+		panic(fmt.Sprintf("Holocene ChannelAssembler already active, old origin: %v", cp.Origin()))
+	default:
+		panic(fmt.Sprintf("unknown channel stage type: %T", cp))
+	}
+}

op-node/rollup/derive/channel_mux_test.go

+package derive
+
+import (
+	"context"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/log"
+
+	"github.com/ethereum-optimism/optimism/op-node/metrics"
+	"github.com/ethereum-optimism/optimism/op-node/rollup"
+	"github.com/ethereum-optimism/optimism/op-service/eth"
+	"github.com/ethereum-optimism/optimism/op-service/testlog"
+)
+
+func TestChannelMux_LaterHolocene(t *testing.T) {
+	log := testlog.Logger(t, log.LevelTrace)
+	ctx := context.Background()
+	l1A := eth.L1BlockRef{Time: 0, Hash: common.Hash{0xaa}}
+	l1B := eth.L1BlockRef{Time: 12, Hash: common.Hash{0xbb}}
+	cfg := &rollup.Config{
+		HoloceneTime: &l1B.Time,
+	}
+	spec := rollup.NewChainSpec(cfg)
+	m := metrics.NoopMetrics
+	c := NewChannelMux(log, spec, nil, m)
+
+	require.Nil(t, c.RawChannelProvider)
+
+	err := c.Reset(ctx, l1A, eth.SystemConfig{})
+	require.Equal(t, io.EOF, err)
+	require.IsType(t, new(ChannelBank), c.RawChannelProvider)
+
+	c.Transform(rollup.Holocene)
+	require.IsType(t, new(ChannelAssembler), c.RawChannelProvider)
+
+	err = c.Reset(ctx, l1B, eth.SystemConfig{})
+	require.Equal(t, io.EOF, err)
+	require.IsType(t, new(ChannelAssembler), c.RawChannelProvider)
+
+	err = c.Reset(ctx, l1A, eth.SystemConfig{})
+	require.Equal(t, io.EOF, err)
+	require.IsType(t, new(ChannelBank), c.RawChannelProvider)
+}
+
+func TestChannelMux_ActiveHolocene(t *testing.T) {
+	log := testlog.Logger(t, log.LevelTrace)
+	ctx := context.Background()
+	l1A := eth.L1BlockRef{Time: 42, Hash: common.Hash{0xaa}}
+	cfg := &rollup.Config{
+		HoloceneTime: &l1A.Time,
+	}
+	spec := rollup.NewChainSpec(cfg)
+	// without the fake input, the panic check later would panic because of the Origin() call
+	prev := &fakeChannelBankInput{}
+	m := metrics.NoopMetrics
+	c := NewChannelMux(log, spec, prev, m)
+
+	require.Nil(t, c.RawChannelProvider)
+
+	err := c.Reset(ctx, l1A, eth.SystemConfig{})
+	require.Equal(t, io.EOF, err)
+	require.IsType(t, new(ChannelAssembler), c.RawChannelProvider)
+
+	require.Panics(t, func() { c.Transform(rollup.Holocene) })
+}

op-node/rollup/derive/frame_queue.go

@@ -10,7 +10,10 @@ import (
 	"github.com/ethereum-optimism/optimism/op-service/eth"
 )
 
-var _ NextFrameProvider = &FrameQueue{}
+var (
+	_ NextFrameProvider = (*FrameQueue)(nil)
+	_ ForkTransformer   = (*FrameQueue)(nil)
+)
 
 //go:generate mockery --name NextDataProvider --case snake
 type NextDataProvider interface {
@@ -33,13 +36,20 @@ func NewFrameQueue(log log.Logger, cfg *rollup.Config, prev NextDataProvider) *F
 	}
 }
 
+func (fq *FrameQueue) Transform(f rollup.ForkName) {
+	switch f {
+	case rollup.Holocene:
+		fq.log.Info("FrameQueue: resetting with Holocene activation")
+		// With Holocene activation, the frame queue is simply reset
+		fq.reset()
+	}
+}
+
 func (fq *FrameQueue) Origin() eth.L1BlockRef {
 	return fq.prev.Origin()
 }
 
 func (fq *FrameQueue) NextFrame(ctx context.Context) (Frame, error) {
-	// TODO(12157): reset frame queue once at Holocene L1 origin block
-
 	// Only load more frames if necessary
 	if len(fq.frames) == 0 {
 		if err := fq.loadNextFrames(ctx); err != nil {
@@ -129,7 +139,11 @@ func pruneFrameQueue(frames []Frame) []Frame {
 	return frames
 }
 
-func (fq *FrameQueue) Reset(_ context.Context, _ eth.L1BlockRef, _ eth.SystemConfig) error {
-	fq.frames = fq.frames[:0]
+func (fq *FrameQueue) Reset(context.Context, eth.L1BlockRef, eth.SystemConfig) error {
+	fq.reset()
 	return io.EOF
 }
+
+func (fq *FrameQueue) reset() {
+	fq.frames = fq.frames[:0]
+}

op-node/rollup/derive/pipeline.go

@@ -38,6 +38,10 @@ type ResettableStage interface {
 	Reset(ctx context.Context, base eth.L1BlockRef, baseCfg eth.SystemConfig) error
 }
 
+type ForkTransformer interface {
+	Transform(rollup.ForkName)
+}
+
 type L2Source interface {
 	PayloadByHash(context.Context, common.Hash) (*eth.ExecutionPayloadEnvelope, error)
 	PayloadByNumber(context.Context, uint64) (*eth.ExecutionPayloadEnvelope, error)
@@ -79,14 +83,15 @@ type DerivationPipeline struct {
 func NewDerivationPipeline(log log.Logger, rollupCfg *rollup.Config, l1Fetcher L1Fetcher, l1Blobs L1BlobsFetcher,
 	altDA AltDAInputFetcher, l2Source L2Source, metrics Metrics,
 ) *DerivationPipeline {
+	spec := rollup.NewChainSpec(rollupCfg)
 	// Pull stages
 	l1Traversal := NewL1Traversal(log, rollupCfg, l1Fetcher)
 	dataSrc := NewDataSourceFactory(log, rollupCfg, l1Fetcher, l1Blobs, altDA) // auxiliary stage for L1Retrieval
 	l1Src := NewL1Retrieval(log, dataSrc, l1Traversal)
 	frameQueue := NewFrameQueue(log, rollupCfg, l1Src)
-	bank := NewChannelBank(log, rollupCfg, frameQueue, metrics)
+	bank := NewChannelMux(log, spec, frameQueue, metrics)
 	chInReader := NewChannelInReader(rollupCfg, log, bank, metrics)
-	batchQueue := NewBatchQueue(log, rollupCfg, chInReader, l2Source)
+	batchQueue := NewBatchMux(log, rollupCfg, chInReader, l2Source)
 	attrBuilder := NewFetchingAttributesBuilder(rollupCfg, l1Fetcher, l2Source)
 	attributesQueue := NewAttributesQueue(log, rollupCfg, attrBuilder, batchQueue)
 
@@ -177,6 +182,7 @@ func (dp *DerivationPipeline) Step(ctx context.Context, pendingSafeHead eth.L2Bl
 		if err := VerifyNewL1Origin(ctx, prevOrigin, dp.l1Fetcher, newOrigin); err != nil {
 			return nil, fmt.Errorf("failed to verify L1 origin transition: %w", err)
 		}
+		dp.transformStages(prevOrigin, newOrigin)
 		dp.origin = newOrigin
 	}
 
@@ -238,6 +244,20 @@ func (dp *DerivationPipeline) initialReset(ctx context.Context, resetL2Safe eth.
 	return nil
 }
 
+func (db *DerivationPipeline) transformStages(oldOrigin, newOrigin eth.L1BlockRef) {
+	fork := db.rollupCfg.IsActivationBlock(oldOrigin.Time, newOrigin.Time)
+	if fork == "" {
+		return
+	}
+
+	db.log.Info("Transforming stages", "fork", fork)
+	for _, stage := range db.stages {
+		if tf, ok := stage.(ForkTransformer); ok {
+			tf.Transform(fork)
+		}
+	}
+}
+
 func (dp *DerivationPipeline) ConfirmEngineReset() {
 	dp.engineIsReset = true
 }

op-node/rollup/types.go

@@ -465,6 +465,17 @@ func (c *Config) IsInteropActivationBlock(l2BlockTime uint64) bool {
 		!c.IsInterop(l2BlockTime-c.BlockTime)
 }
 
+// IsActivationBlock returns the fork which activates at the block with time newTime if the previous
+// block's time is oldTime. It return an empty ForkName if no fork activation takes place between
+// those timestamps. It can be used for both, L1 and L2 blocks.
+// TODO(12490): Currently only supports Holocene. Will be modularized in a follow-up.
+func (c *Config) IsActivationBlock(oldTime, newTime uint64) ForkName {
+	if c.IsHolocene(newTime) && !c.IsHolocene(oldTime) {
+		return Holocene
+	}
+	return ""
+}
+
 func (c *Config) ActivateAtGenesis(hardfork ForkName) {
 	// IMPORTANT! ordered from newest to oldest
 	switch hardfork {

op-node/rollup/types_test.go

@@ -701,3 +701,19 @@ func TestGetPayloadVersion(t *testing.T) {
 		})
 	}
 }
+
+func TestConfig_IsActivationBlock(t *testing.T) {
+	ts := uint64(42)
+	// TODO(12490): Currently only supports Holocene. Will be modularized in a follow-up.
+	for _, fork := range []ForkName{Holocene} {
+		cfg := &Config{
+			HoloceneTime: &ts,
+		}
+		require.Equal(t, fork, cfg.IsActivationBlock(0, ts))
+		require.Equal(t, fork, cfg.IsActivationBlock(0, ts+64))
+		require.Equal(t, fork, cfg.IsActivationBlock(ts-1, ts))
+		require.Equal(t, fork, cfg.IsActivationBlock(ts-1, ts+1))
+		require.Zero(t, cfg.IsActivationBlock(0, ts-1))
+		require.Zero(t, cfg.IsActivationBlock(ts, ts+1))
+	}
+}