An API compatible V2 of Hyperlane is currently under development. This page outlines some of the changes users can expect in V2 so they can prepare accordingly. More extensive documentation will be available prior to testnet launch.
A high level overview of some of the changes in V2.
Hyperlane V2 will have one Mailbox contract per chain, as opposed to one Outbox and several Inboxes. This allows applications to specify a single address from which they send and receive messages. ConnectionManager contracts can still be used but are less useful as there are no longer many Inbox contracts to aggregate.
Interchain security modules
Hyperlane V2 adopts Interchain security modules, as outlined in the sovereign consensus HIP. More work is needed in order for the relayer to automatically recognize anything other than the default InterchainSecurityModule. Until then, V2 will look similar to V1 from a security perspective.
Changing domain IDs
User feedback has indicated that the difference between Hyperlane domain IDs, and EIP-155 chain IDs. In V2, Hyperlane domain IDs will be changed to match EIP-155 chain IDs.
Migration guide for apps using V1
If you're building on Hyperlane V1 using an AbacusConnectionManager, you will be able to migrate from V1 to V2 by:
1. Calling abacusConnectionManager.setOutbox(v2MailboxAddress)
2. Calling abacusConnectionManager.enrollInbox(v2DomainId, v2MailboxAddress)
3. Eventually, calling abacusConnectionManager.unenrollInbox(v1InboxAddress) for each V1 Inbox\
Using V2 API on V1
You can use the V2CompatibilityRouter(0x1d3aAC239538e6F1831C8708803e61A9EA299Eec) on all chains that v1 is on to be able to use the V2 interface (i.e. function signatures and chain IDs instead of domain IDs) and when v2 launches, you can easily change the mailboxes to the actual v2 maiboxes.