What probably matters to youSection of the release
Assistant message/result frames (complete, partial-first-frame, and stream-event variants) and the result schema gain a new user_message_uuids array listing every user message uuid consumed by or merged into a turn, in order, capped at 64 entries, including uuids for prompts that were queued but not yet started during the turn. This lets SDK consumers bind a reply to any of the sends it answers, not just the first.
A new helper (Jc) tracks the up-to-64 recently-seen user message UUIDs and attaches them as user_message_uuid/user_message_uuids to result and error telemetry via sendEcho, errorVariantFields(), and related call sites, fully wired into the query loop's telemetry emission.
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed sinceAnthropic's documentation has since written up user_message_uuids, on Agent SDK reference - TypeScript.Claude Code sets `user_message_uuid` and `user_message_uuids` on the turn's first assistant message, under the conditions in [`user_message_uuid`](#user_message_uuid). When Claude Code re-runs a turn that a restart interrupted, the re-run'…agent-sdk/typescriptsee the edit
How sure we are
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agreesAnthropic's documentation has since written up user_message_uuids, on Agent SDK reference - TypeScript.
