Status: IN
Both chat and email derive identifiers deterministically from existing data (sorted user-pair for DM conversations, first message ID for threads) rather than generating separate IDs, eliminating coordination overhead and guaranteeing idempotent ID creation.
deriving IDs from content eliminates the need for a coordination service or sequence generator
Depends on (SL): chat-dm-conversation-dedup, email-service-thread-id-is-first-msg