Remove receive Id tracking from ERC7786Recipient

contracts/crosschain/ERC7786Recipient.sol

@@ -4,7 +4,6 @@
 pragma solidity ^0.8.20;
 
 import {IERC7786Recipient} from "../interfaces/draft-IERC7786.sol";
-import {BitMaps} from "../utils/structs/BitMaps.sol";
 
 /**
  * @dev Base implementation of an ERC-7786 compliant cross-chain message receiver.
@@ -18,16 +17,14 @@ import {BitMaps} from "../utils/structs/BitMaps.sol";
  *
  * * {_processMessage}, the internal function that will be called with any message that has been validated.
  *
- * This contract implements replay protection, meaning that if two messages are received from the same gateway with the
- * same `receiveId`, then the second one will NOT be executed, regardless of the result of {_isAuthorizedGateway}.
+ * ERC-7786 requires the gateway to ensure messages are not delivered more than once. Therefore, we don't need to keep
+ * track of the processed receiveId.
+ *
+ * @custom:stateless
  */
 abstract contract ERC7786Recipient is IERC7786Recipient {
-    using BitMaps for BitMaps.BitMap;
-
-    mapping(address gateway => BitMaps.BitMap) private _received;
-
+    /// @dev Error thrown if the gateway is not authorized to send messages to this contract on behalf of the sender.
     error ERC7786RecipientUnauthorizedGateway(address gateway, bytes sender);
-    error ERC7786RecipientMessageAlreadyProcessed(address gateway, bytes32 receiveId);
 
     /// @inheritdoc IERC7786Recipient
     function receiveMessage(
@@ -40,12 +37,6 @@ abstract contract ERC7786Recipient is IERC7786Recipient {
             revert ERC7786RecipientUnauthorizedGateway(msg.sender, sender);
         }
 
-        // Prevent duplicate execution
-        if (_received[msg.sender].get(uint256(receiveId))) {
-            revert ERC7786RecipientMessageAlreadyProcessed(msg.sender, receiveId);
-        }
-        _received[msg.sender].set(uint256(receiveId));
-
         _processMessage(msg.sender, receiveId, sender, payload);
 
         return IERC7786Recipient.receiveMessage.selector;

test/crosschain/BridgeERC20.behavior.js

@@ -104,25 +104,6 @@ function shouldBehaveLikeBridgeERC20({ chainAIsCustodial = false, chainBIsCustod
         .to.be.revertedWithCustomError(this.bridgeA, 'ERC7786RecipientUnauthorizedGateway')
         .withArgs(this.gateway, this.chain.toErc7930(invalid));
     });
-
-    it('cannot replay message', async function () {
-      const [from, to] = this.accounts;
-
-      const id = ethers.ZeroHash;
-      const payload = this.encodePayload(from, to, amount);
-
-      // first time works
-      await expect(
-        this.bridgeA.connect(this.gatewayAsEOA).receiveMessage(id, this.chain.toErc7930(this.bridgeB), payload),
-      ).to.emit(this.bridgeA, 'CrosschainFungibleTransferReceived');
-
-      // second time fails
-      await expect(
-        this.bridgeA.connect(this.gatewayAsEOA).receiveMessage(id, this.chain.toErc7930(this.bridgeB), payload),
-      )
-        .to.be.revertedWithCustomError(this.bridgeA, 'ERC7786RecipientMessageAlreadyProcessed')
-        .withArgs(this.gateway, id);
-    });
   });
 
   describe('reconfiguration', function () {

test/crosschain/ERC7786Recipient.test.js

@@ -3,7 +3,6 @@ const { expect } = require('chai');
 const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 
 const { getLocalChain } = require('../helpers/chains');
-const { impersonate } = require('../helpers/account');
 const { generators } = require('../helpers/random');
 
 const value = 42n;
@@ -36,7 +35,7 @@ describe('ERC7786Recipient', function () {
       .withArgs(this.gateway, ethers.toBeHex(1n, 32n), this.toErc7930(this.sender), payload, value);
   });
 
-  it('receive multiple similar messages (with different receiveIds)', async function () {
+  it('receive multiple similar messages', async function () {
     for (let i = 1n; i < 5n; ++i) {
       await expect(
         this.gateway.connect(this.sender).sendMessage(this.toErc7930(this.receiver), payload, attributes, { value }),
@@ -46,23 +45,6 @@ describe('ERC7786Recipient', function () {
     }
   });
 
-  it('multiple use of the same receiveId', async function () {
-    const gatewayAsEOA = await impersonate(this.gateway.target);
-    const receiveId = ethers.toBeHex(1n, 32n);
-
-    await expect(
-      this.receiver.connect(gatewayAsEOA).receiveMessage(receiveId, this.toErc7930(this.sender), payload, { value }),
-    )
-      .to.emit(this.receiver, 'MessageReceived')
-      .withArgs(this.gateway, receiveId, this.toErc7930(this.sender), payload, value);
-
-    await expect(
-      this.receiver.connect(gatewayAsEOA).receiveMessage(receiveId, this.toErc7930(this.sender), payload, { value }),
-    )
-      .to.be.revertedWithCustomError(this.receiver, 'ERC7786RecipientMessageAlreadyProcessed')
-      .withArgs(this.gateway, receiveId);
-  });
-
   it('unauthorized call', async function () {
     await expect(
       this.receiver.connect(this.notAGateway).receiveMessage(ethers.ZeroHash, this.toErc7930(this.sender), payload),