fix(cartesia): stop sending max_buffer_delay_ms on /tts/bytes

[brodie-avoca]

Description

toCartesiaOptions puts max_buffer_delay_ms: 0 in the shared payload, so it goes out on /tts/bytes as well as the websocket. Cartesia rejects every non-streaming request with:

400 Invalid request: Your request was invalid: max buffer delay is only supported for websocket requests

#1107 added the field for the websocket message ("Add max_buffer_delay_ms = 0 to ws msg"); the placement made it apply to both paths. The main caller of synthesize() in a voice pipeline is the TTS FallbackAdapter recovery probe, so once a session fails over from Cartesia it can never recover to it. We observed one failover followed by 99 consecutive rejected recovery probes on a production call.

Parity: the Python plugin only adds max_buffer_delay_ms in the websocket sentence stream (tts.py#L433-L434) and never sends it on /tts/bytes (tts.py#L366).

Changes Made

• Move max_buffer_delay_ms: 0 under the existing streaming guard in toCartesiaOptions, next to add_timestamps.
• Pick node:http or node:https from the base URL protocol in ChunkedStream (the port calculation already did), so the non-streaming path can be tested against a local plain-HTTP server the same way the websocket tests already are.
• Tests: the /tts/bytes payload has no max_buffer_delay_ms; websocket packets still carry it.

Pre-Review Checklist

• Build passes: All builds (lint, typecheck, tests) pass locally
• AI-generated code reviewed: Removed unnecessary comments and ensured code quality
• Changes explained: All changes are properly documented and justified above
• Scope appropriate: All changes relate to the PR title
• Video demo: n/a, request-payload change covered by tests

Testing

• Automated tests added/updated
• All tests pass
• restaurant_agent.ts / realtime_agent.ts: n/a, not a major change

pnpm build
pnpm vitest run plugins/cartesia/src/tts.test.ts   # 11 passed, 1 skipped (credential-gated)
pnpm exec eslint plugins/cartesia/src/tts.ts plugins/cartesia/src/tts.test.ts
pnpm exec prettier --check plugins/cartesia/src/tts.ts plugins/cartesia/src/tts.test.ts

Additional Notes

The same handler never checks the response status, which is why this 400 showed up as silent empty audio rather than an error. That is a separate fix in #2443, which is stacked on this branch and should be reviewed after this one.

[changeset-bot]

🦋 Changeset detected

Latest commit: a4a4f56

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

This PR includes changesets to release 38 packages

Name	Type
@livekit/agents-plugin-cartesia	Patch
@livekit/agents	Patch
@livekit/agents-plugin-anam	Patch
@livekit/agents-plugin-anthropic	Patch
@livekit/agents-plugin-assemblyai	Patch
@livekit/agents-plugin-azure	Patch
@livekit/agents-plugin-baseten	Patch
@livekit/agents-plugin-bey	Patch
@livekit/agents-plugin-cerebras	Patch
@livekit/agents-plugin-deepgram	Patch
@livekit/agents-plugin-did	Patch
@livekit/agents-plugin-elevenlabs	Patch
@livekit/agents-plugin-fishaudio	Patch
@livekit/agents-plugin-google	Patch
@livekit/agents-plugin-hume	Patch
@livekit/agents-plugin-inworld	Patch
@livekit/agents-plugin-krisp	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-protoface	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-plugins-test	Patch
@livekit/agents-plugin-trugen	Patch
@livekit/agents-plugin-xai	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.