AztecProtocol · spalladino · Jul 18, 2026 · Jul 18, 2026 · Jul 18, 2026 · Jul 18, 2026
diff --git a/docs/docs-developers/docs/tutorials/testing_governance_rollup_upgrade.md b/docs/docs-developers/docs/tutorials/testing_governance_rollup_upgrade.md
@@ -89,7 +89,6 @@ export AZTEC_EPOCH_DURATION=16
 export AZTEC_TARGET_COMMITTEE_SIZE=48
 export AZTEC_LAG_IN_EPOCHS_FOR_VALIDATOR_SET=2
 export AZTEC_LAG_IN_EPOCHS_FOR_RANDAO=2
-export AZTEC_INBOX_LAG=2
 export AZTEC_PROOF_SUBMISSION_EPOCHS=2
 export AZTEC_LOCAL_EJECTION_THRESHOLD=0
 export AZTEC_SLASHING_ROUND_SIZE_IN_EPOCHS=1

diff --git a/docs/docs-operate/operators/reference/node-api-reference.md b/docs/docs-operate/operators/reference/node-api-reference.md
@@ -635,22 +635,24 @@ curl -X POST http://localhost:8080 \
   -d '{"jsonrpc":"2.0","method":"aztec_getL1ToL2MessageMembershipWitness","params":["latest","0x1234..."],"id":1}'
 ```
 
-### aztec_getL1ToL2MessageCheckpoint
+### aztec_getL1ToL2MessageIndex
 
-Returns the L2 checkpoint number in which this L1 to L2 message becomes available, or undefined if not found.
+Returns the compact leaf index assigned to this L1 to L2 message as soon as the node has ingested it from L1,
+before any L2 block consumes it. Returns undefined if the node has not yet seen the message. The message becomes
+consumable once a block's L1-to-L2 message tree grows past this index.
 
 **Parameters**:
 
 1. `l1ToL2Message` - `Fr`
 
-**Returns**: `number | undefined`
+**Returns**: `bigint | undefined`
 
 **Example**:
 
 ```bash
 curl -X POST http://localhost:8080 \
   -H 'Content-Type: application/json' \
-  -d '{"jsonrpc":"2.0","method":"aztec_getL1ToL2MessageCheckpoint","params":["0x1234..."],"id":1}'
+  -d '{"jsonrpc":"2.0","method":"aztec_getL1ToL2MessageIndex","params":["0x1234..."],"id":1}'
 ```
 
 ### aztec_getL2ToL1MembershipWitness

@@ -349,7 +349,6 @@ const INBOX_ABI = [
     inputs: [
       { name: "index", type: "uint256", indexed: false },
       { name: "hash", type: "bytes32", indexed: true },
-      { name: "rollingHash", type: "bytes16", indexed: false },
       { name: "inboxRollingHash", type: "bytes32", indexed: false },
       { name: "bucketSeq", type: "uint256", indexed: false },
     ],

@@ -261,7 +261,6 @@ const INBOX_ABI = [
     inputs: [
       { name: "index", type: "uint256", indexed: false },
       { name: "hash", type: "bytes32", indexed: true },
-      { name: "rollingHash", type: "bytes16", indexed: false },
       { name: "inboxRollingHash", type: "bytes32", indexed: false },
       { name: "bucketSeq", type: "uint256", indexed: false },
     ],

@@ -167,7 +167,6 @@ const INBOX_ABI = [
     inputs: [
       { name: "index", type: "uint256", indexed: false },
       { name: "hash", type: "bytes32", indexed: true },
-      { name: "rollingHash", type: "bytes16", indexed: false },
       { name: "inboxRollingHash", type: "bytes32", indexed: false },
       { name: "bucketSeq", type: "uint256", indexed: false },
     ],

diff --git a/docs/scripts/node_api_reference_generation/generate_node_api_reference.ts b/docs/scripts/node_api_reference_generation/generate_node_api_reference.ts
@@ -559,7 +559,7 @@ const METHOD_GROUPS: { heading: string; namespace: string; methods: string[] }[]
     namespace: 'aztec',
     methods: [
       'getL1ToL2MessageMembershipWitness',
-      'getL1ToL2MessageCheckpoint',
+      'getL1ToL2MessageIndex',
       'getL2ToL1MembershipWitness',
       'getL2ToL1Messages',
     ],

diff --git a/l1-contracts/scripts/network-defaults.json b/l1-contracts/scripts/network-defaults.json
@@ -14,7 +14,6 @@
   "AZTEC_ENTRY_QUEUE_FLUSH_SIZE_MIN": 48,
   "AZTEC_ENTRY_QUEUE_FLUSH_SIZE_QUOTIENT": 2,
   "AZTEC_ENTRY_QUEUE_MAX_FLUSH_SIZE": 48,
-  "AZTEC_INBOX_LAG": 1,
   "AZTEC_PROOF_SUBMISSION_EPOCHS": 1,
   "AZTEC_MANA_TARGET": 100000000,
   "AZTEC_PROVING_COST_PER_MANA": 100,

@@ -27,7 +27,7 @@ struct PublicInputArgs {
   bytes32 previousArchive;
   bytes32 endArchive;
   bytes32 outHash;
-  // Inbox rolling-hash chain segment consumed across the proven epoch (AZIP-22 Fast Inbox). Both boundaries are
+  // Inbox rolling-hash chain segment consumed across the proven epoch. Both boundaries are
   // anchored at proof submission against the rolling hashes recorded at propose for checkpoints start - 1 and end.
   bytes32 previousInboxRollingHash;
   bytes32 endInboxRollingHash;

@@ -16,11 +16,6 @@ uint256 constant MAX_MSGS_PER_BUCKET = 256;
  */
 interface IInbox {
   struct InboxState {
-    // 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;
     // 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;
@@ -50,13 +45,10 @@ interface IInbox {
    * @notice Emitted when a message is sent
    * @param index - The compact cumulative index of the message in the Inbox insertion order
    * @param hash - The hash of the message
-   * @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 index, bytes32 indexed hash, bytes16 rollingHash, bytes32 inboxRollingHash, uint256 bucketSeq
-  );
+  event MessageSent(uint256 index, bytes32 indexed hash, bytes32 inboxRollingHash, uint256 bucketSeq);
 
   // docs:start:send_l1_to_l2_message
   /**

@@ -401,8 +401,7 @@ library ProposeLib {
 
   /**
    * @notice Validates a checkpoint's Inbox consumption against the streaming inbox buckets and returns how
-   *         far consumption has reached. Called from propose() as the enforced consumption path (AZIP-22 Fast
-   *         Inbox).
+   *         far consumption has reached. Called from propose() as the enforced consumption path.
    *
    * @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

@@ -37,13 +37,8 @@ contract Inbox is IInbox {
 
   uint256 public immutable BUCKET_RING_SIZE;
 
-  // Legacy 128-bit keccak rolling hash over every inserted message leaf. Consumed only by the node's
-  // message sync and L1-reorg detection; retained until those switch to the full-width consensus rolling
-  // hash tracked in the buckets (AZIP-22 Fast Inbox).
-  bytes16 internal messagesRollingHash;
-
   // Ring of rolling-hash buckets, keyed by `bucketSeq % BUCKET_RING_SIZE`. Consumed by the streaming inbox
-  // checks at `propose` (AZIP-22 Fast Inbox).
+  // checks at `propose`.
   mapping(uint256 ringIndex => InboxBucket bucket) internal buckets;
 
   uint64 internal currentBucketSeq;
@@ -106,11 +101,9 @@ contract Inbox is IInbox {
 
     bytes32 leaf = message.sha256ToField();
 
-    messagesRollingHash = bytes16(keccak256(abi.encodePacked(messagesRollingHash, leaf)));
-
     (uint64 bucketSeq, bytes32 inboxRollingHash) = _absorbIntoBucket(leaf);
 
-    emit MessageSent(index, leaf, messagesRollingHash, inboxRollingHash, bucketSeq);
+    emit MessageSent(index, leaf, inboxRollingHash, bucketSeq);
 
     return (leaf, index);
   }
@@ -120,7 +113,7 @@ contract Inbox is IInbox {
   }
 
   function getState() external view override(IInbox) returns (InboxState memory) {
-    return InboxState({rollingHash: messagesRollingHash, totalMessagesInserted: _totalMessagesInserted()});
+    return InboxState({totalMessagesInserted: _totalMessagesInserted()});
   }
 
   function getTotalMessagesInserted() external view override(IInbox) returns (uint64) {

diff --git a/l1-contracts/test/Inbox.t.sol b/l1-contracts/test/Inbox.t.sol
@@ -66,11 +66,10 @@ contract InboxTest is Test {
     DataStructures.L1ToL2Msg memory message = _boundMessage(_message, globalLeafIndex);
 
     bytes32 leaf = message.sha256ToField();
-    bytes16 expectedRollingHash = bytes16(keccak256(abi.encodePacked(stateBefore.rollingHash, leaf)));
     bytes32 expectedInboxRollingHash = Hash.accumulateInboxRollingHash(bytes32(0), leaf);
     vm.expectEmit(true, true, true, true);
     // event we expect
-    emit IInbox.MessageSent(globalLeafIndex, leaf, expectedRollingHash, expectedInboxRollingHash, 1);
+    emit IInbox.MessageSent(globalLeafIndex, leaf, expectedInboxRollingHash, 1);
     // event we will get
     (bytes32 insertedLeaf, uint256 insertedIndex) =
       inbox.sendL2Message(message.recipient, message.content, message.secretHash);
@@ -80,7 +79,6 @@ contract InboxTest is Test {
 
     Inbox.InboxState memory stateAfter = inbox.getState();
     assertEq(stateBefore.totalMessagesInserted + 1, stateAfter.totalMessagesInserted);
-    assertEq(expectedRollingHash, stateAfter.rollingHash);
   }
 
   function testSendDuplicateL2Messages() public {

diff --git a/l1-contracts/test/InboxBuckets.t.sol b/l1-contracts/test/InboxBuckets.t.sol
@@ -132,11 +132,10 @@ contract InboxBucketsTest is Test {
       index: inbox.getState().totalMessagesInserted
     });
     bytes32 leaf = Hash.sha256ToField(message);
-    bytes16 legacyHash = bytes16(keccak256(abi.encodePacked(inbox.getState().rollingHash, leaf)));
     bytes32 inboxRollingHash = Hash.accumulateInboxRollingHash(bytes32(0), leaf);
 
     vm.expectEmit(true, true, true, true, address(inbox));
-    emit IInbox.MessageSent(message.index, leaf, legacyHash, inboxRollingHash, 1);
+    emit IInbox.MessageSent(message.index, leaf, inboxRollingHash, 1);
     inbox.sendL2Message(recipient, content, secretHash);
   }
 

diff --git a/l1-contracts/test/fee_portal/depositToAztecPublic.t.sol b/l1-contracts/test/fee_portal/depositToAztecPublic.t.sol
@@ -63,7 +63,7 @@ contract DepositToAztecPublic is Test {
     uint256 amount = 100 ether;
 
     Inbox inbox = Inbox(address(Rollup(address(registry.getCanonicalRollup())).getInbox()));
-    // Compact cumulative index (AZIP-22 Fast Inbox): the first message against a fresh Inbox has index 0.
+    // Compact cumulative index: the first message against a fresh Inbox has index 0.
     uint256 expectedIndex = 0;
 
     // The purpose of including the function selector is to make the message unique to that specific call. Note that
@@ -86,10 +86,9 @@ contract DepositToAztecPublic is Test {
 
     assertEq(inbox.getTotalMessagesInserted(), 0);
 
-    bytes16 expectedHash = bytes16(keccak256(abi.encodePacked(inbox.getState().rollingHash, expectedKey)));
     bytes32 expectedInboxRollingHash = Hash.accumulateInboxRollingHash(bytes32(0), expectedKey);
     vm.expectEmit(true, true, true, true, address(inbox));
-    emit IInbox.MessageSent(expectedIndex, expectedKey, expectedHash, expectedInboxRollingHash, 1);
+    emit IInbox.MessageSent(expectedIndex, expectedKey, expectedInboxRollingHash, 1);
     vm.expectEmit(true, true, true, true, address(feeJuicePortal));
     emit IFeeJuicePortal.DepositToAztecPublic(to, amount, secretHash, expectedKey, expectedIndex);
 

diff --git a/l1-contracts/test/portals/TokenPortal.t.sol b/l1-contracts/test/portals/TokenPortal.t.sol
@@ -120,12 +120,11 @@ contract TokenPortalTest is Test {
     DataStructures.L1ToL2Msg memory expectedMessage = _createExpectedMintPrivateL1ToL2Message(expectedIndex);
 
     bytes32 expectedLeaf = expectedMessage.sha256ToField();
-    bytes16 expectedHash = bytes16(keccak256(abi.encodePacked(inbox.getState().rollingHash, expectedLeaf)));
     bytes32 expectedInboxRollingHash = Hash.accumulateInboxRollingHash(bytes32(0), expectedLeaf);
     // Check the event was emitted
     vm.expectEmit(true, true, true, true);
     // event we expect
-    emit IInbox.MessageSent(expectedIndex, expectedLeaf, expectedHash, expectedInboxRollingHash, 1);
+    emit IInbox.MessageSent(expectedIndex, expectedLeaf, expectedInboxRollingHash, 1);
     // event we will get
 
     // Perform op
@@ -148,13 +147,12 @@ contract TokenPortalTest is Test {
     uint256 expectedIndex = 0;
     DataStructures.L1ToL2Msg memory expectedMessage = _createExpectedMintPublicL1ToL2Message(expectedIndex);
     bytes32 expectedLeaf = expectedMessage.sha256ToField();
-    bytes16 expectedHash = bytes16(keccak256(abi.encodePacked(inbox.getState().rollingHash, expectedLeaf)));
     bytes32 expectedInboxRollingHash = Hash.accumulateInboxRollingHash(bytes32(0), expectedLeaf);
 
     // Check the event was emitted
     vm.expectEmit(true, true, true, true);
     // event we expect
-    emit IInbox.MessageSent(expectedIndex, expectedLeaf, expectedHash, expectedInboxRollingHash, 1);
+    emit IInbox.MessageSent(expectedIndex, expectedLeaf, expectedInboxRollingHash, 1);
 
     // Perform op
     (bytes32 leaf, uint256 index) = tokenPortal.depositToAztecPublic(to, amount, secretHashForL2MessageConsumption);

diff --git a/l1-contracts/test/script/DeployAztecL1Contracts.t.sol b/l1-contracts/test/script/DeployAztecL1Contracts.t.sol
@@ -30,7 +30,6 @@ contract DeployAztecL1ContractsTest is Test {
     // Timing config
     vm.setEnv("AZTEC_SLOT_DURATION", vm.toString(json.readUint(".AZTEC_SLOT_DURATION")));
     vm.setEnv("AZTEC_EPOCH_DURATION", vm.toString(json.readUint(".AZTEC_EPOCH_DURATION")));
-    vm.setEnv("AZTEC_INBOX_LAG", vm.toString(json.readUint(".AZTEC_INBOX_LAG")));
     vm.setEnv("AZTEC_PROOF_SUBMISSION_EPOCHS", vm.toString(json.readUint(".AZTEC_PROOF_SUBMISSION_EPOCHS")));
 
     // Validator config

diff --git a/l1-contracts/test/script/DeployRollupForUpgrade.t.sol b/l1-contracts/test/script/DeployRollupForUpgrade.t.sol
@@ -41,7 +41,6 @@ contract DeployRollupForUpgradeTest is Test {
     // Timing config
     vm.setEnv("AZTEC_SLOT_DURATION", vm.toString(json.readUint(".AZTEC_SLOT_DURATION")));
     vm.setEnv("AZTEC_EPOCH_DURATION", vm.toString(json.readUint(".AZTEC_EPOCH_DURATION")));
-    vm.setEnv("AZTEC_INBOX_LAG", vm.toString(json.readUint(".AZTEC_INBOX_LAG")));
     vm.setEnv("AZTEC_PROOF_SUBMISSION_EPOCHS", vm.toString(json.readUint(".AZTEC_PROOF_SUBMISSION_EPOCHS")));
 
     // Validator config

@@ -145,7 +145,7 @@ impl<let NumBlobs: u32> CheckpointRollupPublicInputsComposer<NumBlobs> {
             last_archive_root: merged_rollup.previous_archive.root,
             block_headers_hash: merged_rollup.block_headers_hash,
             blobs_hash: self.blobs_hash,
-            // Sourced from the inbox parity proof: the checkpoint's only inbox commitment (AZIP-22 Fast Inbox).
+            // Sourced from the inbox parity proof: the checkpoint's only inbox commitment.
             inbox_rolling_hash: self.parity.end_rolling_hash,
             epoch_out_hash,
             slot_number: constants.slot_number,

@@ -14,8 +14,8 @@ pub struct CheckpointHeader {
     pub last_archive_root: Field,
     pub block_headers_hash: Field,
     pub blobs_hash: Field,
-    // Inbox rolling-hash chain value after consuming all L1-to-L2 messages bundled into this checkpoint (AZIP-22 Fast
-    // Inbox): the truncated-to-field sha256 chain the L1 Inbox accumulates. This is the checkpoint's only inbox
+    // Inbox rolling-hash chain value after consuming all L1-to-L2 messages bundled into this checkpoint:
+    // the truncated-to-field sha256 chain the L1 Inbox accumulates. This is the checkpoint's only inbox
     // commitment.
     pub inbox_rolling_hash: Field,
     // The root of the epoch out hash balanced tree. The out hash of the first checkpoint in the epoch is inserted at

diff --git a/spartan/environments/bench-10tps.env b/spartan/environments/bench-10tps.env
@@ -18,7 +18,6 @@ AZTEC_SLOT_DURATION=72
 AZTEC_PROOF_SUBMISSION_EPOCHS=2
 AZTEC_LAG_IN_EPOCHS_FOR_VALIDATOR_SET=1
 AZTEC_LAG_IN_EPOCHS_FOR_RANDAO=1
-AZTEC_INBOX_LAG=2
 
 # 2B mana target - good for about ~800 txs at 2.5M mana each
 AZTEC_MANA_TARGET=2000000000

diff --git a/spartan/environments/bench-inclusion-sweep.env b/spartan/environments/bench-inclusion-sweep.env
@@ -19,7 +19,6 @@ AZTEC_SLOT_DURATION=72
 AZTEC_PROOF_SUBMISSION_EPOCHS=100
 AZTEC_LAG_IN_EPOCHS_FOR_VALIDATOR_SET=1
 AZTEC_LAG_IN_EPOCHS_FOR_RANDAO=1
-AZTEC_INBOX_LAG=2
 
 AZTEC_MANA_TARGET=2000000000
 

diff --git a/spartan/environments/network-defaults.yml b/spartan/environments/network-defaults.yml
@@ -59,8 +59,6 @@ l1-contracts: &l1-contracts-defaults
   #---------------------------------------------------------------------------
   # Proof & Block Configuration
   #---------------------------------------------------------------------------
-  # Checkpoints to lag in inbox (prevents sequencer DOS attacks).
-  AZTEC_INBOX_LAG: 2
   # Epochs after end that proofs are still accepted.
   AZTEC_PROOF_SUBMISSION_EPOCHS: 1
   # Target mana consumption per block.

diff --git a/spartan/environments/next-net.env b/spartan/environments/next-net.env
@@ -39,7 +39,6 @@ SEQ_MAX_TX_PER_CHECKPOINT=12
 SEQ_BUILD_CHECKPOINT_IF_EMPTY=true
 SEQ_BLOCK_DURATION_MS=5500
 
-AZTEC_INBOX_LAG=2
 
 VALIDATOR_REPLICAS=2
 VALIDATORS_PER_NODE=24

diff --git a/spartan/environments/next-scenario.env b/spartan/environments/next-scenario.env
@@ -7,7 +7,6 @@ DESTROY_ETH_DEVNET=true
 CREATE_ETH_DEVNET=true
 AZTEC_EPOCH_DURATION=32
 AZTEC_SLOT_DURATION=36
-AZTEC_INBOX_LAG=2
 ETHEREUM_CHAIN_ID=1337
 LABS_INFRA_MNEMONIC="test test test test test test test test test test test junk"
 FUNDING_PRIVATE_KEY="0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80"

diff --git a/spartan/environments/staging-internal.env b/spartan/environments/staging-internal.env
@@ -36,7 +36,6 @@ SPONSORED_FPC=false
 # Rollup
 AZTEC_LAG_IN_EPOCHS_FOR_VALIDATOR_SET=2
 AZTEC_LAG_IN_EPOCHS_FOR_RANDAO=2
-AZTEC_INBOX_LAG=2
 AZTEC_MANA_TARGET=75000000
 AZTEC_PROVING_COST_PER_MANA=12500000
 

diff --git a/spartan/environments/staging-public.env b/spartan/environments/staging-public.env
@@ -36,7 +36,6 @@ SPONSORED_FPC=false
 # Rollup
 AZTEC_LAG_IN_EPOCHS_FOR_VALIDATOR_SET=2
 AZTEC_LAG_IN_EPOCHS_FOR_RANDAO=2
-AZTEC_INBOX_LAG=2
 AZTEC_MANA_TARGET=75000000
 AZTEC_PROVING_COST_PER_MANA=12500000
 

diff --git a/spartan/scripts/deploy_network.sh b/spartan/scripts/deploy_network.sh
@@ -460,7 +460,6 @@ AZTEC_LAG_IN_EPOCHS_FOR_RANDAO = ${AZTEC_LAG_IN_EPOCHS_FOR_RANDAO:-null}
 AZTEC_SLOT_DURATION = ${AZTEC_SLOT_DURATION:-null}
 AZTEC_EPOCH_DURATION = ${AZTEC_EPOCH_DURATION:-null}
 AZTEC_TARGET_COMMITTEE_SIZE = ${AZTEC_TARGET_COMMITTEE_SIZE:-null}
-AZTEC_INBOX_LAG = ${AZTEC_INBOX_LAG:-null}
 AZTEC_PROOF_SUBMISSION_EPOCHS = ${AZTEC_PROOF_SUBMISSION_EPOCHS:-null}
 AZTEC_ACTIVATION_THRESHOLD = ${AZTEC_ACTIVATION_THRESHOLD:-null}
 AZTEC_EJECTION_THRESHOLD = ${AZTEC_EJECTION_THRESHOLD:-null}

diff --git a/spartan/terraform/deploy-rollup-contracts/main.tf b/spartan/terraform/deploy-rollup-contracts/main.tf
@@ -43,7 +43,6 @@ locals {
     AZTEC_SLOT_DURATION                      = var.AZTEC_SLOT_DURATION
     AZTEC_EPOCH_DURATION                     = var.AZTEC_EPOCH_DURATION
     AZTEC_TARGET_COMMITTEE_SIZE              = var.AZTEC_TARGET_COMMITTEE_SIZE
-    AZTEC_INBOX_LAG                          = var.AZTEC_INBOX_LAG
     AZTEC_PROOF_SUBMISSION_EPOCHS            = var.AZTEC_PROOF_SUBMISSION_EPOCHS
     AZTEC_ACTIVATION_THRESHOLD               = var.AZTEC_ACTIVATION_THRESHOLD
     AZTEC_EJECTION_THRESHOLD                 = var.AZTEC_EJECTION_THRESHOLD

diff --git a/spartan/terraform/deploy-rollup-contracts/variables.tf b/spartan/terraform/deploy-rollup-contracts/variables.tf
@@ -86,12 +86,6 @@ variable "AZTEC_PROOF_SUBMISSION_EPOCHS" {
   nullable    = true
 }
 
-variable "AZTEC_INBOX_LAG" {
-  description = "Checkpoints to lag in inbox (prevents sequencer DOS attacks)"
-  type        = string
-  nullable    = true
-}
-
 variable "AZTEC_ACTIVATION_THRESHOLD" {
   description = "Aztec activation threshold"
   type        = string