Stellar Open Protocol meeting discussing CAP 21 and CAP 40, which lay groundwork for payment channels. CAP 21 generalizes transaction preconditions to support relative time locks and other conditions; CAP 40 enables participants to exchange signatures for multiple transactions in one step.
The Stellar Development Foundation held a protocol discussion meeting focused on two core advancement proposals (CAPs) essential for payment channel implementation. CAP 21 proposes generalizing the time bounds field to support additional preconditions including relative time locks and extra signers for stateless HTLCs. Key changes include new failure modes for multiple preconditions, clarifications on account entry extensions, and a decision to use nested extension structures. CAP 40 allows payment channel participants to safely exchange signatures for up to three transactions simultaneously, enabling cross-chain interoperability and eliminating round trips. The team identified technical issues around sequence number validation and bump sequence operations that require further refinement before implementation.