Conditional Light Clients

When bridging into L2s such as Scroll, the IBC light client on L1AL1A​ tracking a L2L2 on L1BL1B​ needs to take the Settlement Condition into account. This is known as a conditional client. Union is the first team to ship conditional IBC clients.

Above you can see the IBC L2 Light Client architecture. The L2 Light Client on L1AL1A​ is tracking both the consensus of L2L2, and the settlements of L2L2 on L1BL1B​ through the light client of L1BL1B​ on L1AL1A​.

The L1AL1A​ light client on L2L2 is able to track the consensus of L1AL1A​ directly, because L1AL1A​ does not need to settle.