chore(fast-inbox): delete legacy L1 inbox path (A-1386)

Deletes the legacy L1 Inbox path now that `propose` enforces streaming-inbox consumption (AZIP-22 Fast Inbox, FI-16). Stacked on `spl/a-1385-streaming-e2e`; part of the Fast Inbox stack (#24784..#24790 below this one).

## What is deleted

- **Frontier trees**: the `trees` mapping, `forest`, `HEIGHT`/`SIZE`/`EMPTY_ROOT`, the per-message tree insert, `getRoot()`, and the whole `consume()` flow.
- **LAG / inboxLag**: the `LAG` immutable and `_lag`/`_height` constructor args (the Inbox constructor is now `(rollup, feeAsset, version, bucketRingSize)`), `RollupConfigInput.inboxLag` and its `RollupCore` pass-through, and `Constants.L1_TO_L2_MSG_SUBTREE_HEIGHT` from the Inbox construction.
- **Dead event field**: the `MessageSent.checkpointNumber` (former `inProgress`) argument, which became meaningless once `consume()` stopped advancing it.
- **Orphaned errors**: `Inbox__Unauthorized`, `Inbox__MustBuildBeforeConsume`, `Rollup__InvalidInHash`.

## What is re-homed / kept

- The compact message index now reads the current bucket's running total (`totalMsgCount`) instead of a parallel counter; `InboxState.inProgress` and `getInProgress()` are gone.
- The 128-bit `rollingHash`, `InboxState.{rollingHash, totalMessagesInserted}`, `getState()`, and `getTotalMessagesInserted()` are **kept**: the node still consumes them for message sync and L1-reorg detection. Their removal is the node cleanup's job (FI-18).
- `FrontierLib` is **kept** — it still backs the base-parity (`test/Parity.t.sol`) and merkle (`test/merkle/Frontier.t.sol`) tests, which are unrelated to the Inbox (parity-circuit territory, FI-17). The plan's "delete the file" assumption is contradicted by grep.

## TS follow-through

- `ethereum` InboxContract: drop `getLag()`, drop the `MessageSent.checkpointNumber` decode, stop reading `inProgress`; `InboxContractState.treeInProgress` is now optional (no longer tracked on-chain).
- Stop threading `inboxLag` through `queries.getL1ContractsConfig` and the L1 deploy env. The broader `AZTEC_INBOX_LAG` config sweep (`ethereum/src/config.ts`, `foundation`, `stdlib`, ~30 e2e configs) is deferred to FI-18, which explicitly owns it.
- Archiver decode derives the message's checkpoint number from the compact index (the event no longer carries it), keeping the legacy per-checkpoint store shape untouched for FI-18.
- Removed the obsolete `advanceInboxInProgress` cheat code + its inbox-drift tests, and the orphaned archiver `inHash`-mismatch sync test (the cross-check was removed at the flip).

## Gas

Deleting the frontier insert is a large `sendL2Message` win. Whole-test gas (`forge test` on `InboxBuckets.t.sol`), before → after:

| Case | Before | After |
| --- | --- | --- |
| First-ever message | 175,251 | 116,835 |
| First message of a new L1 block | 329,460 | 195,555 |
| Absorb into an existing bucket | 286,673 | 149,968 |
| Rollover mid-block (256 messages) | 18,923,988 | 3,068,480 |

Per-call `sendL2Message` gas after cleanup: first-ever 99,526; first-of-new-block 53,763; existing-bucket absorb 9,273; rollover 53,801.

## Testing

- `forge build` + `forge test` green: 887 passed, 0 failed. This fixes 4 pre-existing baseline failures the flip stranded (`fee_portal`/`TokenPortal` deposit tests using tree-relative indices + the old event shape).
- `@aztec/ethereum` builds clean; `config`/`queries` unit tests green.
- `@aztec/archiver` has no self-owned type errors; `message_store` (36), `archiver-sync` (59), and the decode/struct suites (58) all pass. (Pre-existing `noir-protocol-circuits-types` stale-artifact errors are unaffected.)
- e2e not run locally. The stability gate ("a few days of green e2e/networks before deleting the fallback") applies at merge time for this stacked line, not at PR creation.


## Review follow-up (phase-2 final review)

Deleting the inbox-drift bot test left `bot.test.ts`'s `cheatCodes` variable unused (lint error); a follow-up commit removes it.

## Leftover sweep (post-review)

- Corrected the `PublicInputArgs` natspec in `IRollup.sol`: it still described `previousInboxRollingHash` / `endInboxRollingHash` as deliberately unvalidated "until the Fast Inbox flip", but the flip (#24789, below this branch) added exactly that validation — `EpochProofLib` anchors the start boundary against the propose-time record, and the end boundary is covered transitively by the stored checkpoint header hashes. The comment now describes the implemented behavior.
- The 128-bit rolling hash this PR deliberately kept (see "What is re-homed / kept") is now removed at the node-cleanup PR #24793, where its last TS readers disappear.



Replaces #24791.

Author: spalladino

docs/docs-developers/docs/foundational-topics/ethereum-aztec-messaging/inbox.md

@@ -35,34 +35,10 @@ These functions allow you to query the current state of the Inbox.
 
 | Function                   | Returns           | Description                                      |
 | -------------------------- | ----------------- | ------------------------------------------------ |
-| `getRoot(uint256)`         | `bytes32`         | Returns the root of a message tree for a given checkpoint number. |
-| `getState()`               | `InboxState`      | Returns the current inbox state (rolling hash, total messages inserted, in-progress checkpoint). |
+| `getState()`               | `InboxState`      | Returns the current inbox state (rolling hash, total messages inserted). |
 | `getTotalMessagesInserted()` | `uint64`        | Returns the total number of messages inserted into the inbox. |
-| `getInProgress()`          | `uint64`          | Returns the checkpoint number currently being filled. |
 | `getFeeAssetPortal()`      | `address`         | Returns the address of the Fee Juice portal. |
 
-## Internal functions
-
-:::note
-The following functions are only callable by the Rollup contract and are documented here for completeness.
-:::
-
-### `consume()`
-
-Consumes a message tree for a given checkpoint number.
-
-#include_code consume l1-contracts/src/core/interfaces/messagebridge/IInbox.sol solidity
-
-| Name        | Type      | Description                              |
-| ----------- | --------- | ---------------------------------------- |
-| _toConsume  | `uint256` | The checkpoint number to consume.        |
-| ReturnValue | `bytes32` | The root of the consumed message tree.   |
-
-#### Edge cases
-
-- Will revert with `Inbox__Unauthorized()` if `msg.sender != ROLLUP`.
-- Will revert with `Inbox__MustBuildBeforeConsume()` if trying to consume a checkpoint that hasn't been built yet.
-
 ## Related pages
 
 - [Outbox](./outbox.md) - L2 to L1 message passing

docs/examples/ts/aave_bridge/index.ts

@@ -347,7 +347,6 @@ const INBOX_ABI = [
     type: "event",
     name: "MessageSent",
     inputs: [
-      { name: "checkpointNumber", type: "uint256", indexed: true },
       { name: "index", type: "uint256", indexed: false },
       { name: "hash", type: "bytes32", indexed: true },
       { name: "rollingHash", type: "bytes16", indexed: false },

docs/examples/ts/example_swap/index.ts

@@ -259,7 +259,6 @@ const INBOX_ABI = [
     type: "event",
     name: "MessageSent",
     inputs: [
-      { name: "checkpointNumber", type: "uint256", indexed: true },
       { name: "index", type: "uint256", indexed: false },
       { name: "hash", type: "bytes32", indexed: true },
       { name: "rollingHash", type: "bytes16", indexed: false },

docs/examples/ts/token_bridge/index.ts

@@ -165,7 +165,6 @@ const INBOX_ABI = [
     type: "event",
     name: "MessageSent",
     inputs: [
-      { name: "checkpointNumber", type: "uint256", indexed: true },
       { name: "index", type: "uint256", indexed: false },
       { name: "hash", type: "bytes32", indexed: true },
       { name: "rollingHash", type: "bytes16", indexed: false },

l1-contracts/script/deploy/RollupConfiguration.sol

@@ -110,7 +110,6 @@ contract RollupConfiguration is IRollupConfiguration, Test {
     config.targetCommitteeSize = vm.envUint("AZTEC_TARGET_COMMITTEE_SIZE");
     config.lagInEpochsForValidatorSet = vm.envUint("AZTEC_LAG_IN_EPOCHS_FOR_VALIDATOR_SET");
     config.lagInEpochsForRandao = vm.envUint("AZTEC_LAG_IN_EPOCHS_FOR_RANDAO");
-    config.inboxLag = vm.envUint("AZTEC_INBOX_LAG");
     config.aztecProofSubmissionEpochs = vm.envUint("AZTEC_PROOF_SUBMISSION_EPOCHS");
     config.localEjectionThreshold = vm.envUint("AZTEC_LOCAL_EJECTION_THRESHOLD");
     config.slashingQuorum = vm.envOr("AZTEC_SLASHING_QUORUM", slashingRoundSize / 2 + 1);

l1-contracts/src/core/RollupCore.sol

@@ -15,7 +15,6 @@ import {IStakingCore} from "@aztec/core/interfaces/IStaking.sol";
 import {IValidatorSelectionCore} from "@aztec/core/interfaces/IValidatorSelection.sol";
 import {IInbox} from "@aztec/core/interfaces/messagebridge/IInbox.sol";
 import {IOutbox} from "@aztec/core/interfaces/messagebridge/IOutbox.sol";
-import {Constants} from "@aztec/core/libraries/ConstantsGen.sol";
 import {CommitteeAttestations} from "@aztec/core/libraries/rollup/AttestationLib.sol";
 import {Errors} from "@aztec/core/libraries/Errors.sol";
 import {EpochProofExtLib} from "@aztec/core/libraries/rollup/EpochProofExtLib.sol";
@@ -620,18 +619,7 @@ contract RollupCore is EIP712("Aztec Rollup", "1"), Ownable, IStakingCore, IVali
     rollupStore.config.epochProofVerifier = _epochProofVerifier;
     rollupStore.config.version = _config.version;
 
-    IInbox inbox = IInbox(
-      address(
-        new Inbox(
-          address(this),
-          _feeAsset,
-          _config.version,
-          Constants.L1_TO_L2_MSG_SUBTREE_HEIGHT,
-          _config.inboxLag,
-          INBOX_BUCKET_RING_SIZE
-        )
-      )
-    );
+    IInbox inbox = IInbox(address(new Inbox(address(this), _feeAsset, _config.version, INBOX_BUCKET_RING_SIZE)));
 
     rollupStore.config.inbox = inbox;
     rollupStore.config.outbox = IOutbox(address(new Outbox(address(this), _config.version)));

l1-contracts/src/core/interfaces/IRollup.sol

@@ -27,9 +27,8 @@ struct PublicInputArgs {
   bytes32 previousArchive;
   bytes32 endArchive;
   bytes32 outHash;
-  // Inbox rolling-hash chain segment consumed across the proven epoch (AZIP-22 Fast Inbox). Deliberately UNVALIDATED
-  // until the Fast Inbox flip, when they get checked against per-checkpoint records written at propose; for now they
-  // are only passed through to the proof's public inputs.
+  // Inbox rolling-hash chain segment consumed across the proven epoch (AZIP-22 Fast Inbox). Both boundaries are
+  // anchored at proof submission against the rolling hashes recorded at propose for checkpoints start - 1 and end.
   bytes32 previousInboxRollingHash;
   bytes32 endInboxRollingHash;
   address proverId;
@@ -84,7 +83,6 @@ struct RollupConfigInput {
   RewardBoostConfig rewardBoostConfig;
   StakingQueueConfig stakingQueueConfig;
   uint256 localEjectionThreshold;
-  uint256 inboxLag;
 }
 
 struct RollupConfig {

l1-contracts/src/core/interfaces/messagebridge/IInbox.sol

@@ -5,8 +5,8 @@ pragma solidity >=0.8.27;
 import {DataStructures} from "../../libraries/DataStructures.sol";
 
 // Maximum number of messages a single bucket can hold before further messages in the same L1 block spill over
-// into the next bucket. Matches the number of L1 to L2 messages a single L2 block can insert once the streaming
-// inbox is live, so any one bucket is always consumable by one block.
+// into the next bucket. Matches the number of L1 to L2 messages a single L2 block can insert, so any one bucket
+// is always consumable by one block.
 uint256 constant MAX_MSGS_PER_BUCKET = 256;
 
 /**
@@ -16,16 +16,14 @@ uint256 constant MAX_MSGS_PER_BUCKET = 256;
  */
 interface IInbox {
   struct InboxState {
-    // Rolling hash of all messages inserted into the inbox.
-    // Used by clients to check for consistency.
-    // TODO: remove once the streaming inbox (AZIP-22 Fast Inbox) flips on and clients rely on the
-    // consensus rolling hash tracked in the buckets instead.
+    // Legacy 128-bit keccak rolling hash of all messages inserted into the inbox. Consumed only by the
+    // node for message sync and L1-reorg detection.
+    // TODO: remove once the node relies on the full-width consensus rolling hash tracked in the buckets
+    // instead (AZIP-22 Fast Inbox).
     bytes16 rollingHash;
-    // This value is not used much by the contract, but it is useful for synching the node faster
-    // as it can more easily figure out if it can just skip looking for events for a time period.
+    // Cumulative number of messages inserted into the inbox. Useful for synching the node faster as it can
+    // more easily figure out if it can just skip looking for events for a time period.
     uint64 totalMessagesInserted;
-    // Number of a tree which is currently being filled
-    uint64 inProgress;
   }
 
   /**
@@ -50,20 +48,14 @@ interface IInbox {
 
   /**
    * @notice Emitted when a message is sent
-   * @param checkpointNumber - The checkpoint number in which the message is included
-   * @param index - The index of the message in the L1 to L2 messages tree
+   * @param index - The compact cumulative index of the message in the Inbox insertion order
    * @param hash - The hash of the message
-   * @param rollingHash - The rolling hash of all messages inserted into the inbox
+   * @param rollingHash - The legacy 128-bit rolling hash of all messages inserted into the inbox
    * @param inboxRollingHash - The consensus rolling hash (truncated sha256 chain) after this message
    * @param bucketSeq - The sequence number of the bucket this message was absorbed into
    */
   event MessageSent(
-    uint256 indexed checkpointNumber,
-    uint256 index,
-    bytes32 indexed hash,
-    bytes16 rollingHash,
-    bytes32 inboxRollingHash,
-    uint256 bucketSeq
+    uint256 index, bytes32 indexed hash, bytes16 rollingHash, bytes32 inboxRollingHash, uint256 bucketSeq
   );
 
   // docs:start:send_l1_to_l2_message
@@ -74,37 +66,19 @@ interface IInbox {
    * @param _content - The content of the message (application specific)
    * @param _secretHash - The secret hash of the message (make it possible to hide when a specific message is consumed
    * on L2)
-   * @return The key of the message in the set and its leaf index in the tree
+   * @return The key of the message in the set and its compact cumulative index
    */
   function sendL2Message(DataStructures.L2Actor memory _recipient, bytes32 _content, bytes32 _secretHash)
     external
     returns (bytes32, uint256);
   // docs:end:send_l1_to_l2_message
 
-  // docs:start:consume
-  /**
-   * @notice Consumes the current tree, and starts a new one if needed
-   * @dev Only callable by the rollup contract
-   * @dev In the first iteration we return empty tree root because first checkpoint's messages tree is always
-   * empty because there has to be a 1 checkpoint lag to prevent sequencer DOS attacks
-   *
-   * @param _toConsume - The checkpoint number to consume
-   *
-   * @return The root of the consumed tree
-   */
-  function consume(uint256 _toConsume) external returns (bytes32);
-  // docs:end:consume
-
   function getFeeAssetPortal() external view returns (address);
 
-  function getRoot(uint256 _checkpointNumber) external view returns (bytes32);
-
   function getState() external view returns (InboxState memory);
 
   function getTotalMessagesInserted() external view returns (uint64);
 
-  function getInProgress() external view returns (uint64);
-
   /**
    * @notice Returns the sequence number of the bucket currently accumulating messages
    * @return The current bucket sequence number

l1-contracts/src/core/libraries/Errors.sol

@@ -22,12 +22,10 @@ library Errors {
   error DevNet__InvalidProposer(address expected, address actual); // 0x11e6e6f7
 
   // Inbox
-  error Inbox__Unauthorized(); // 0xe5336a6b
   error Inbox__ActorTooLarge(bytes32 actor); // 0xa776a06e
   error Inbox__VersionMismatch(uint256 expected, uint256 actual); // 0x47452014
   error Inbox__ContentTooLarge(bytes32 content); // 0x47452014
   error Inbox__SecretHashTooLarge(bytes32 secretHash); // 0xecde7e2c
-  error Inbox__MustBuildBeforeConsume(); // 0xc4901999
   error Inbox__BucketOutOfWindow(uint256 seq, uint256 current); // 0xfee255b7
 
   // Outbox
@@ -58,7 +56,6 @@ library Errors {
   error Rollup__InvalidCheckpointHeader(bytes32 expected, bytes32 actual);
   error Rollup__InvalidCheckpointHeaderCount(uint256 expected, uint256 actual);
   error Rollup__InvalidCheckpointNumber(uint256 expected, uint256 actual); // 0xd1ba9bfa
-  error Rollup__InvalidInHash(bytes32 expected, bytes32 actual); // 0xcd6f4233
   error Rollup__InvalidInboxRollingHash(bytes32 expected, bytes32 actual); // 0xed1f7bb5
   error Rollup__InvalidPreviousInboxRollingHash(bytes32 expected, bytes32 actual); // 0x2fe7cae5
   error Rollup__InvalidEndInboxRollingHash(bytes32 expected, bytes32 actual); // 0x4a9cdb72

l1-contracts/src/core/libraries/rollup/ProposeLib.sol

@@ -142,7 +142,7 @@ library ProposeLib {
    *          - Checkpoint header validations (see validateHeader function for details)
    *          - Proposer signature is valid for designated slot proposer:
    *            Errors.ValidatorSelection__MissingProposerSignature
-   *          - Inbox hash matches expected value: Errors.Rollup__InvalidInHash
+   *          - Streaming Inbox consumption is valid: Errors.Rollup__InvalidInboxRollingHash
    *          - Archive root is within the scalar field: Errors.Rollup__FieldElementOutOfRange
    *
    *          Validations NOT performed:
@@ -154,7 +154,7 @@ library ProposeLib {
    *          - Store archive root for the new checkpoint number
    *          - Store checkpoint metadata in circular storage (TempCheckpointLog)
    *          - Update L1 gas fee oracle
-   *          - Consume inbox messages
+   *          - Validate streaming Inbox consumption against the parent checkpoint
    *          - Setup epoch for validator selection (first block of the epoch)
    *
    * @param _args - The arguments to propose the checkpoint
@@ -401,8 +401,8 @@ library ProposeLib {
 
   /**
    * @notice Validates a checkpoint's Inbox consumption against the streaming inbox buckets and returns how
-   *         far consumption has reached. Not yet called from propose(): the legacy `consume()`/`inHash` flow
-   *         remains the enforced path until the streaming inbox (AZIP-22 Fast Inbox) flips on.
+   *         far consumption has reached. Called from propose() as the enforced consumption path (AZIP-22 Fast
+   *         Inbox).
    *
    * @dev Read-only; performs no Inbox write. Checks, in order:
    *      1. The checkpoint header's `inboxRollingHash` must equal the rolling hash snapshotted in the Inbox