Upgrade Across to support Non-EVM and Prefills

Author(s): Risk Labs Status: Proposed

Summary:

This proposal seeks approval from the ACX community to implement an upgrade to the Across Protocol. The upgrade introduces the capability for Across to support non-EVM chains and enable "prefill" use cases, where the fill comes at the same time or before the deposit. These changes are designed to expand Across' reach, improve user experience, and strengthen its position as a leading cross-chain bridge.

Motivation:

Supporting non-EVM chains opens new opportunities for growth, tapping into new users, use cases and ecosystems that can greatly benefit from the bridging experience Across can deliver.

An active area of research in improving cross-chain UX is via "prefill" flows, where users are filled at the same time or before their deposit. This will open opportunities for new integrations and partnerships while positioning Across as a leader in cross-chain UX.

Specification & Implementation:

This proposal will include making the following changes to the protocol:

• All Fill and Deposit related SpokePool events have been renamed and have had changes in their args. This includes speed ups.
• depositIds are no longer guaranteed to increment.
• The protocol can no longer assume that fills happen after deposits.
• The protocol must handle a new set of invalidity cases related to bytes32 addresses being specified for EVM chains.
• The following methods have had their signature changed (with no backwards compatible option):
  • requestV3SlowFill
  • executeSlowFillLeaf
  • fillRelayWithUpdatedDeposit
• The following events have had their names/signatures changed:
  • ExecutedRelayerRefundRoot
  • EmergencyDeleteRootBundle
  • TokensBridged
  • V3FundsDeposited -> FundsDeposited
  • RequestedSpeedUpV3Deposit -> RequestedSpeedUpDeposit
  • FilledV3Relay -> FilledRelay
  • RequestedV3SlowFill -> RequestedSlowFill

Upon successful vote, Risk Labs will implement these contract changes.

More details about the updates and migration process can be found here.

Downtime:

The above migration will not require downtime.

Key Takeaways By implementing this upgrade, Across can expand to non-EVM chains and power use cases innovating on cross-chain UX.

Downside (Cons):

This migration presents the following risks:

Downtime We do not expect downtime, but if we encounter issues during migration, downtime could occur.

Migrations required by integrators This upgrade introduces breaking changes and requires integrators of Across to modify their implementation, as described in the migration guide. If integrators do not make the required updates prior, we risk breaking their integration with Across. We are working diligently with all integrators to ensure readiness to mitigate this risk.

Voting:

A "FOR" vote would result in Risk Labs implementing the contract changes described herein.

An "AGAINST" vote would result in no changes to the protocol at this time.