Murmuration extensions
Every extension is additive: real Slack ignores them, our SDKs use them, nothing breaks either way.
chat.postMessage#client_msg_id
Section titled “chat.postMessage#client_msg_id”Idempotency key: identical (channel,user,client_msg_id) retries return the original ts. Slack accepts but ignores this param — safe to always send.
*#murmuration.hint
Section titled “*#murmuration.hint”Additive human hint on error envelopes. Never sent by real Slack; SDKs surface it when present and stay silent otherwise (ADR-0011).