Make ERC7786OpenBridge tolerant to failing gateways

[Amxx]

Fixes https://audits.openzeppelin.com/openzeppelin-solidity/project/openzeppelin-community-contracts/e2bb51d8-df7a-4d26-934a-be65c637d4e5/issue/any-single-gateway-revert-blocks-sendmessage-for-all-gateways

Summary

Makes ERC7786OpenBridge resilient to individual gateway failures on the source side, so a single misbehaving gateway can no longer block a message that can still satisfy the N-of-M threshold.

Changes

• sendMessage: each gateway.sendMessage is now wrapped in try/catch. A reverting gateway no longer aborts the whole send; instead the loop continues with the others. After the loop, the call requires at least getThreshold() successful sends (ERC7786OpenBridgeInsufficientGateways otherwise).
• ERC7786OpenBridgeSendMessageFailed(address indexed gateway): new event emitted for each gateway whose sendMessage reverts, for observability.
• _addGateway: rejects non-contract addresses (ERC7786OpenBridgeGatewayNotAContract), covering both the constructor and addGateway.
• The gateway-posting locals are scoped in a block to avoid a stack-too-deep (the project compiles without viaIR).

Tests

• New gateway resilience test: two synchronous gateways, threshold 1, one gateway set to revert on send — asserts the message is still delivered through the healthy gateway and that ERC7786OpenBridgeSendMessageFailed is emitted for the failing one.
• Updated the bad return value / EOA recipient cases: under the synchronous mock, the destination revert is now caught on the send side, so they revert with ERC7786OpenBridgeInsufficientGateways.
• ERC7786GatewayMock gains a setRevertOnSent toggle to drive the resilience test.

All tests pass; prettier / eslint / solhint clean.

Summary by CodeRabbit

• New Features
  • Cross-chain messages can now succeed when some gateways fail, provided the configured delivery threshold is met.
  • Failed gateway attempts are reported through a dedicated event.
• Bug Fixes
  • Gateway registration now rejects addresses that are not deployed contracts.
  • A single unresponsive or reverting gateway no longer automatically prevents message delivery through other available gateways.

[coderabbitai]

Walkthrough

OpenBridge now tolerates individual gateway send failures, emits failure events, enforces successful gateway thresholds, rejects non-contract gateways, and adds mock controls and tests for resilient delivery.

Changes

Gateway resilience

Layer / File(s)	Summary
Resilient gateway submission and validation contracts/crosschain/ERC7786OpenBridge.sol	Gateway calls are wrapped in try/catch, failures emit an event, successful sends are counted against the threshold, and non-contract gateways are rejected.
Configurable failure mock and resilience coverage contracts/mocks/crosschain/ERC7786GatewayMock.sol, test/crosschain/ERC7786OpenBridge.test.js	The mock can force send failures, while tests cover threshold errors and successful delivery through a remaining gateway.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Sender
  participant OpenBridge
  participant FailingGateway
  participant WorkingGateway
  participant Destination
  Sender->>OpenBridge: sendMessage
  OpenBridge->>FailingGateway: sendMessage
  FailingGateway-->>OpenBridge: revert
  OpenBridge-->>Sender: failure event
  OpenBridge->>WorkingGateway: sendMessage
  WorkingGateway->>Destination: deliver message
  WorkingGateway-->>OpenBridge: message ID
  OpenBridge-->>Sender: successful delivery events

Loading

Poem

A bunny watched one gateway fail,
Yet another carried the message trail.
“Catch that error, count the cheer—
The bridge still hops its payload here!” 🐇

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: ERC7786OpenBridge now tolerates failing gateways.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch erc7786-bridge-gateway-resilience

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