Under the hoodTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
SDKArea: what it touches
ImprovementsKind: in v2.1.260,
ImprovementsSection of the release
Live thinking_tokens progress frames (stream-json / Agent SDK) are now stamped with user_message_uuid, the client uuid of the user message (submitMessageoptions.uuid) that triggered the turn, letting a consumer attribute thinking progress to a send before any reply frame arrives. It's absent on synthetic/scheduled turns, turns without a client uuid, and on Remote Control (interactive terminal) sessions. The synthesized result SDK event (built by the new own function) likewise now includes user_message_uuid when available and the outcome isn't a terminal-reason exit.
The turn-streaming generator also now calls an optional trackFirstFrameUpload callback on the first non-thinking stream_event of a turn.
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_uuid, on Agent SDK reference - TypeScript.Claude Code sets the list together with `user_message_uuid` on each reply frame that carries that field and on the result. For the full set of turn frames that echo the answered message's `uuid`, and the version each requires, see [`user_m…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_uuid, on Agent SDK reference - TypeScript.
