livekit-plugins-fishaudio: drop startup prebuffer

[rosetta-livekit-bot]

Summary

Port livekit/agents#6423 for Fish Audio streaming startup latency.

• emit Fish Audio websocket audio frames as soon as they are decoded instead of holding one back at startup
• keep terminal flush frames marked final when present
• add a patch changeset for @livekit/agents-plugin-fishaudio

Verification

• pnpm --filter @livekit/agents-plugin-fishaudio... build
• pnpm test -- plugins/fishaudio (credentialed integration test skipped because Fish/OpenAI keys are not configured)
• pnpm --filter @livekit/agents-plugin-fishaudio lint

Source diff coverage

Source file	Classification	Target coverage
livekit-plugins/livekit-plugins-fishaudio/livekit/plugins/fishaudio/tts.py	Adapted	Ported to plugins/fishaudio/src/tts.ts. The Python source removed _PREBUFFER_CHUNKS, the push_audio startup chunk accumulator, and flush_prebuffer, then pushed Fish audio events directly. The JS target did not have the same two-chunk Fish message prebuffer, but it did hold back one decoded AudioFrame to tag final; this PR removes that startup emission delay by queueing decoded audio frames immediately and only marking frames from the terminal flush as final when present.

No source tests were added or modified in livekit/agents#6423, so no target tests were ported.

---

Ported from livekit/agents#6423

Original PR description

follow-up to #6368. removes the startup prebuffer, keeping the pooled/pre-warmed
websocket reuse.

the prebuffer was a stopgap for fish's cold-start chunk pacing: the old stream sent a
small first chunk (~460ms) then a big second chunk (~930ms) ~200ms later, leaving
webrtc playout only ~200ms of buffer headroom, which jitter turned into a first-word
crackle. so we held the first two chunks before starting playout.

fish has since shipped a server-side change: the second chunk is now ~464ms and
arrives ~60ms after the first. measured chunk-2 headroom (playout starting on the
first chunk):

• origin (api.fish.audio, n=150): median 402ms, min 223ms, 0 underruns
• livekit inference gateway (n=25): median 398ms, min 387ms, 0 underruns

so starting on the first chunk now has ~400ms of headroom, comfortably above webrtc
jitter, with no underruns. the prebuffer is no longer needed — this removes it so
audio starts on the first chunk for optimal latency. verified on a live demo (real
webrtc): no crackles.

net diff: 35 lines removed, connection pooling/prewarm untouched.

Cue voice E2E

• Credentialed voice-mode session: sid_398f2c3dd1e0 at head a6d6279a, using the live Fish Audio streaming path.
• Persisted boundary events prove the first complete SDK frame was emitted 2.465 ms after Fish audio event 1 and 47.427 ms before Fish audio event 2, directly distinguishing the new behavior from the removed retained-frame path.
• The session resolved successfully and persisted events plus full-session and per-command WAV recordings under ~/.cue-cli/sessions/sid_398f2c3dd1e0/.

[changeset-bot]

🦋 Changeset detected

Latest commit: a6d6279

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 36 packages

Name	Type
@livekit/agents-plugin-fishaudio	Patch
@livekit/agents	Patch
@livekit/agents-plugin-anam	Patch
@livekit/agents-plugin-anthropic	Patch
@livekit/agents-plugin-assemblyai	Patch
@livekit/agents-plugin-baseten	Patch
@livekit/agents-plugin-bey	Patch
@livekit/agents-plugin-cartesia	Patch
@livekit/agents-plugin-cerebras	Patch
@livekit/agents-plugin-deepgram	Patch
@livekit/agents-plugin-did	Patch
@livekit/agents-plugin-elevenlabs	Patch
@livekit/agents-plugin-google	Patch
@livekit/agents-plugin-hedra	Patch
@livekit/agents-plugin-hume	Patch
@livekit/agents-plugin-inworld	Patch
@livekit/agents-plugin-lemonslice	Patch
@livekit/agents-plugin-liveavatar	Patch
@livekit/agents-plugin-livekit	Patch
@livekit/agents-plugin-minimax	Patch
@livekit/agents-plugin-mistral	Patch
@livekit/agents-plugin-mistralai	Patch
@livekit/agents-plugin-neuphonic	Patch
@livekit/agents-plugin-openai	Patch
@livekit/agents-plugin-perplexity	Patch
@livekit/agents-plugin-phonic	Patch
@livekit/agents-plugin-resemble	Patch
@livekit/agents-plugin-rime	Patch
@livekit/agents-plugin-runway	Patch
@livekit/agents-plugin-sarvam	Patch
@livekit/agents-plugin-silero	Patch
@livekit/agents-plugin-soniox	Patch
@livekit/agents-plugin-tavus	Patch
@livekit/agents-plugin-trugen	Patch
@livekit/agents-plugin-xai	Patch
@livekit/agents-plugins-test	Patch

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.