feat: Multiple blocks per checkpoint (#18825)

## Summary

This PR refactors the sequencer to propose checkpoints instead of
individual blocks, enabling multi-block checkpoint proposals. The
sequencer now builds multiple blocks within a slot and packages them
into a single checkpoint for L1 publication.

_Yes, this text was written by Claude_

## Environment Variables

### New
- **`SEQ_BLOCK_DURATION_MS`**: Duration per block in milliseconds when
building multiple blocks per slot. If undefined (default), builds a
single block per slot using the full slot duration.
- **`SEQ_BUILD_CHECKPOINT_IF_EMPTY`**: Whether to build and publish an
empty checkpoint when there are no txs (defaults to `true`).

### Changed
- **`SEQ_MAX_L1_TX_INCLUSION_TIME_INTO_SLOT`** changed to
**`SEQ_L1_PUBLISHING_TIME_ALLOWANCE_IN_SLOT`**: Aka "the dead zone".
Renamed to better reflect its purpose of how much time (in seconds) we
allow in the slot for publishing the L1 tx (defaults to 1 L1 slot).
- **`SEQ_TX_POLLING_INTERVAL_MS`** changed to
**`SEQ_POLLING_INTERVAL_MS`**: This is the polling for the sequencer
loop, unrelated to polling for txs.

## Architecture Changes

### Main `Sequencer`
Sequencer now focuses on orchestration and state management by
delegating checkpoint proposal logic to a job-like class. It now manages
lifecycle of checkpoint proposal jobs and handles checkpoint
invalidation.

### `CheckpointProposalJob` (new)
Extracted checkpoint proposal logic into a dedicated, self-contained job
that manages the full lifecycle of building and proposing a checkpoint.
Handles block building loop, attestation collection, L1 publishing, and
P2P broadcasting.

### `CheckpointVoter` (new)
Handles voting for slashing and governance proposals, called from both
the main sequencer and the proposal job.

### `SequencerPublisher`
Updated the publisher to work with Checkpoints as opposed to Blocks.

### `CheckpointsBuilder` (new)
Emulates the old `BlockBuilder` but for checkpoints, managing
checkpoint-level state, and orchestrating building multiple blocks
within a checkpoint. Builds on top of the
`LightweightCheckpointBuilder`.

## Miscellaneous Changes

### Disposable Interface
`MerkleTreeWriteOperations`, `GuardedMerkleTree`, and `HintingDbSource`
now implement a `Disposable` interface for proper resource cleanup.

### Global Variables
Introduced a `CheckpointGlobalVariables` for checkpoint-level constants,
separating block-level and checkpoint-level variables.

### Sequencer Config
All sequencer config defaults are now in a single
`DefaultSequencerConfig` object, and the `Sequencer` works with a config
type with most entries defined.

## Placeholders

### Validator Client
Block proposals currently create dummy checkpoint proposals, and
checkpoint proposal creation needs to be distinguished from block
proposals.

### Archiver & World State Sync
Provisional blocks are not yet sent to archiver and world state, actual
sync mechanism to be wired once available.

### P2P Broadcasting
Checkpoint proposals and provisional blocks use placeholder P2P API,
needs wiring to new P2P protocol once available.

## Pending Work

1. **Timetable fixes**: Review timing for new states and fix timing
calculations.
2. **Checkpoint invalidation**: Implement proper checkpoint invalidation
(currently invalidates blocks)
3. **Checkpoint number computation**: Derive proper checkpoint numbers
(currently assumes checkpoint number is the same as block number)
4. **Block builder cleanup**: Remove old block builder in favor of
CheckpointsBuilder
5. **Metrics review**: Audit all metrics for checkpoint-level tracking
6. **Re-enable disabled tests**: Fix and restore checkpoint proposal
failure tests and multi-block checkpoint tests

Author: spalladino

yarn-project/archiver/tsconfig.json

@@ -7,10 +7,10 @@
   },
   "references": [
     {
-      "path": "../blob-lib"
+      "path": "../blob-client"
     },
     {
-      "path": "../blob-client"
+      "path": "../blob-lib"
     },
     {
       "path": "../constants"

yarn-project/aztec-node/src/aztec-node/server.ts

@@ -43,6 +43,7 @@ import {
   type SequencerPublisher,
   createValidatorForAcceptingTxs,
 } from '@aztec/sequencer-client';
+import { CheckpointsBuilder } from '@aztec/sequencer-client';
 import { PublicProcessorFactory } from '@aztec/simulator/server';
 import {
   AttestationsBlockWatcher,
@@ -427,7 +428,7 @@ export class AztecNodeService implements AztecNode, AztecNodeAdmin, Traceable {
     // Validator enabled, create/start relevant service
     let sequencer: SequencerClient | undefined;
     let slasherClient: SlasherClientInterface | undefined;
-    if (!config.disableValidator) {
+    if (!config.disableValidator && validatorClient) {
       // We create a slasher only if we have a sequencer, since all slashing actions go through the sequencer publisher
       // as they are executed when the node is selected as proposer.
       const validatorAddresses = keyStoreManager
@@ -462,6 +463,13 @@ export class AztecNodeService implements AztecNode, AztecNodeAdmin, Traceable {
           );
 
       // Create and start the sequencer client
+      const checkpointsBuilder = new CheckpointsBuilder(
+        { ...config, l1GenesisTime, slotDuration: Number(slotDuration) },
+        archiver,
+        dateProvider,
+        telemetry,
+      );
+
       sequencer = await SequencerClient.new(config, {
         ...deps,
         epochCache,
@@ -470,7 +478,7 @@ export class AztecNodeService implements AztecNode, AztecNodeAdmin, Traceable {
         p2pClient,
         worldStateSynchronizer,
         slasherClient,
-        blockBuilder,
+        checkpointsBuilder,
         l2BlockSource: archiver,
         l1ToL2MessageSource: archiver,
         telemetry,
@@ -487,6 +495,13 @@ export class AztecNodeService implements AztecNode, AztecNodeAdmin, Traceable {
       log.warn(`Sequencer created but not started`);
     }
 
+    const globalVariableBuilder = new GlobalVariableBuilder({
+      ...config,
+      rollupVersion: BigInt(config.rollupVersion),
+      l1GenesisTime,
+      slotDuration: Number(slotDuration),
+    });
+
     return new AztecNodeService(
       config,
       p2pClient,
@@ -501,7 +516,7 @@ export class AztecNodeService implements AztecNode, AztecNodeAdmin, Traceable {
       epochPruneWatcher,
       ethereumChain.chainInfo.id,
       config.rollupVersion,
-      new GlobalVariableBuilder(config),
+      globalVariableBuilder,
       epochCache,
       packageVersion,
       proofVerifier,

yarn-project/aztec/src/cli/aztec_start_options.ts

@@ -202,6 +202,7 @@ export const aztecStartOptions: { [key: string]: AztecStartOption[] } = {
       'sequencer',
       omitConfigMappings(sequencerClientConfigMappings, [
         'fakeProcessingDelayPerTxMs',
+        'fakeThrowAfterProcessingTxCount',
         'skipCollectingAttestations',
         'skipInvalidateBlockAsProposer',
         'blobSinkMapSizeKb',

yarn-project/cli/src/config/chain_l2_config.test.ts

@@ -26,6 +26,8 @@ describe('enrichEnvironmentWithChainConfig', () => {
       publicMetricsCollectFrom: ['bar'],
       skipArchiverInitialSync: true,
       blobAllowEmptySources: true,
+      blockDurationMs: 12000,
+      buildCheckpointIfEmpty: true,
     };
 
     // Enrich env with those

yarn-project/cli/src/config/chain_l2_config.ts

@@ -19,7 +19,7 @@ const tbMapSizeKb = 1_024 * 1_024 * 1_024; // 1 TB
 export type L2ChainConfig = Omit<L1ContractsConfig, keyof L1TxUtilsConfig> &
   Omit<SlasherConfig, 'slashValidatorsNever' | 'slashValidatorsAlways' | 'slashOverridePayload' | 'slashSelfAllowed'> &
   Pick<P2PConfig, 'bootstrapNodes' | 'p2pEnabled' | 'txPoolDeleteTxsAfterReorg'> &
-  Pick<SequencerConfig, 'minTxsPerBlock' | 'maxTxsPerBlock'> & {
+  Pick<SequencerConfig, 'buildCheckpointIfEmpty' | 'minTxsPerBlock' | 'maxTxsPerBlock' | 'blockDurationMs'> & {
     l1ChainId: number;
     testAccounts: boolean;
     sponsoredFPC: boolean;
@@ -104,6 +104,7 @@ export const stagingIgnitionL2ChainConfig: L2ChainConfig = {
   bootstrapNodes: [],
   minTxsPerBlock: 0,
   maxTxsPerBlock: 0,
+  buildCheckpointIfEmpty: true,
   realProofs: true,
   snapshotsUrls: [`${SNAPSHOTS_URL}/staging-ignition/`],
   autoUpdate: 'config-and-version',
@@ -189,6 +190,7 @@ export const stagingPublicL2ChainConfig: L2ChainConfig = {
   bootstrapNodes: [],
   minTxsPerBlock: 0,
   maxTxsPerBlock: 20,
+  buildCheckpointIfEmpty: true,
   realProofs: true,
   snapshotsUrls: [`${SNAPSHOTS_URL}/staging-public/`],
   autoUpdate: 'config-and-version',
@@ -246,6 +248,7 @@ export const nextNetL2ChainConfig: L2ChainConfig = {
   bootstrapNodes: [],
   minTxsPerBlock: 0,
   maxTxsPerBlock: 8,
+  buildCheckpointIfEmpty: true,
   realProofs: true,
   snapshotsUrls: [],
   autoUpdate: 'config-and-version',
@@ -303,6 +306,7 @@ export const testnetL2ChainConfig: L2ChainConfig = {
   bootstrapNodes: [],
   minTxsPerBlock: 0,
   maxTxsPerBlock: 20,
+  buildCheckpointIfEmpty: true,
   realProofs: true,
   snapshotsUrls: [`${SNAPSHOTS_URL}/testnet/`],
   autoUpdate: 'config-and-version',
@@ -396,6 +400,7 @@ export const mainnetL2ChainConfig: L2ChainConfig = {
   bootstrapNodes: [],
   minTxsPerBlock: 0,
   maxTxsPerBlock: 0,
+  buildCheckpointIfEmpty: true,
   realProofs: true,
   snapshotsUrls: [`${SNAPSHOTS_URL}/mainnet/`],
   autoUpdate: 'notify',
@@ -484,6 +489,7 @@ export const devnetL2ChainConfig: L2ChainConfig = {
   bootstrapNodes: [],
   minTxsPerBlock: 0,
   maxTxsPerBlock: 8,
+  buildCheckpointIfEmpty: true,
   realProofs: false,
   snapshotsUrls: [],
   autoUpdate: 'config-and-version',
@@ -577,6 +583,12 @@ export function enrichEnvironmentWithChainConfig(config: L2ChainConfig) {
   enrichVar('L1_CHAIN_ID', config.l1ChainId.toString());
   enrichVar('SEQ_MIN_TX_PER_BLOCK', config.minTxsPerBlock.toString());
   enrichVar('SEQ_MAX_TX_PER_BLOCK', config.maxTxsPerBlock.toString());
+  if (config.blockDurationMs !== undefined) {
+    enrichVar('SEQ_BLOCK_DURATION_MS', config.blockDurationMs.toString());
+  }
+  if (config.buildCheckpointIfEmpty !== undefined) {
+    enrichVar('SEQ_BUILD_CHECKPOINT_IF_EMPTY', config.buildCheckpointIfEmpty.toString());
+  }
   enrichVar('PROVER_REAL_PROOFS', config.realProofs.toString());
   enrichVar('PXE_PROVER_ENABLED', config.realProofs.toString());
   enrichVar('SYNC_SNAPSHOTS_URLS', config.snapshotsUrls.join(','));

yarn-project/cli/src/config/network_config.ts

@@ -141,4 +141,7 @@ export async function enrichEnvironmentWithNetworkConfig(networkName: NetworkNam
   if (networkConfig.blobFileStoreUrls?.length) {
     enrichVar('BLOB_FILE_STORE_URLS', networkConfig.blobFileStoreUrls.join(','));
   }
+  if (networkConfig.blockDurationMs !== undefined) {
+    enrichVar('SEQ_BLOCK_DURATION_MS', String(networkConfig.blockDurationMs));
+  }
 }

yarn-project/end-to-end/scripts/docker-compose.yml

@@ -23,7 +23,7 @@ services:
       FORCE_COLOR: ${FORCE_COLOR:-1}
       ARCHIVER_POLLING_INTERVAL_MS: 500
       P2P_BLOCK_CHECK_INTERVAL_MS: 500
-      SEQ_TX_POLLING_INTERVAL_MS: 500
+      SEQ_POLLING_INTERVAL_MS: 500
       WS_BLOCK_CHECK_INTERVAL_MS: 500
       ARCHIVER_VIEM_POLLING_INTERVAL_MS: 500
       HARDWARE_CONCURRENCY: ${HARDWARE_CONCURRENCY:-}

yarn-project/end-to-end/src/composed/web3signer/e2e_multi_validator_node_key_store.test.ts

@@ -290,7 +290,7 @@ describe('e2e_multi_validator_node', () => {
       minTxsPerBlock: 1,
       maxTxsPerBlock: 1,
       archiverPollingIntervalMS: 200,
-      transactionPollingIntervalMS: 200,
+      sequencerPollingIntervalMS: 200,
       worldStateBlockCheckIntervalMS: 200,
       blockCheckIntervalMS: 200,
       startProverNode: true,