fix(core): surface final lk.transcription_final for user transcriptions

[rchengLK]

Summary

useTranscriptions reports a stale lk.transcription_final for user STT segments —
it stays "false" even after the segment is finalized. Agent (TTS) segments are
unaffected and correctly report "true".

Root cause

Transcription updates for a segment arrive as separate text streams sharing the same
lk.segment_id. setupTextStream dedupes by that id, but when it finds an existing
entry it updates only text and keeps the streamInfo captured from the first
stream it saw for the segment:

textStreams[index] = {
  ...textStreams[index],
  text: accumulatedText,
  // streamInfo never refreshed
};

Because streamInfo.attributes is frozen at the first interim update, any attribute that
changes over the life of a segment is lost. For user STT the first stream is an interim
result with lk.transcription_final="false"; the finalizing stream ("true") replaces
only .text, so consumers never observe the final flag. Agent segments happen to work
because the first stream they see already carries lk.transcription_final="true".

Fix

Carry the latest streamInfo forward on update:

textStreams[index] = {
  ...textStreams[index],
  text: accumulatedText,
  streamInfo: reader.info,
};

reader.info for a later stream is a refresh of the same segment's info — lk.segment_id
is still present (dedup is unaffected), and lk.transcription_final / lk.transcribed_track_id
etc. are brought up to date.

Reproduction

Frontend renders useTranscriptions()[i].streamInfo.attributes['lk.transcription_final']
and talks to a livekit-agents agent with STT enabled. The agent's user_input_transcribed
event reports is_final=True, but the UI shows "false" for every user segment.

Testing

• pnpm --filter @livekit/components-core build — passes
• pnpm --filter @livekit/components-core test — 98/98 passing
• Verified end-to-end against a live agent: user segments now flip to final="true" on finalization.

Changeset

@livekit/components-core — patch: Fix useTranscriptions reporting a stale
lk.transcription_final (and other mutable stream attributes) for user STT segments;
setupTextStream now carries the latest streamInfo forward on segment updates.

Notes

• Orthogonal to Add proof of concept of transcription ordering fix #1346 (transcription ordering) — both touch the same object literal but
  different fields, so they don't conflict.
• Producer side is correct; this is purely a consumer-side fix in @livekit/components-core.

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Project	Deployment	Actions	Updated (UTC)
components-js-storybook-5kld	Ready	Preview, Comment	Jun 24, 2026 4:47pm

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size-limit report 📦

Path	Size
LiveKitRoom only	6.01 KB (0%)
LiveKitRoom with VideoConference	32.25 KB (0%)
All exports	43.69 KB (+0.02% 🔺)