Stellar Development Foundation hosted an open protocol meeting to discuss CAP 21, a draft proposal for generalized transaction preconditions. The CAP aims to enable payment channels, relative time locks, and time-delayed key recovery by extending account entries and replacing the time bounds field with more flexible preconditions.
The Stellar Development Foundation held a technical meeting to review CAP 21 (Generalized Transaction Preconditions), a proposal first drafted in May 2019 that has been revised with new possibilities from claimable balances introduced in protocol 15. CAP 21 generalizes transaction preconditions to support relative time locks, sequence number range checking, and other conditions to advance network scalability through off-chain payment channels. Key discussion points included the approach's soundness, technical implementation details, data structure design choices, and potential foot guns. The team reached consensus on using signed 64-bit integers for time and duration types, maintaining a single preconditions structure rather than a complex language, and deferring union extension debates. Implementation challenges focus on forwarding logic and data structure efficiency. The proposal enables use cases like payment channels, pre-signed transactions, and time-delayed account recovery.