shinshin86/aituber-onair/wrap-tts-as-openai-compatible

Wrap TTS As OpenAI-Compatible

Overview

Build or fix a thin compatibility server that exposes an existing TTS runtime as OpenAI-compatible speech at POST /v1/audio/speech.

Prefer a minimal adapter. Do not redesign the upstream TTS runtime unless the request explicitly asks for it.

Optimize for practical local TTS runtimes that can reasonably fit the OpenAI speech shape: text input, optional voice selection, optional speed, and WAV output.

Scope

Good fit:

• local or self-hosted TTS with a stable Python API, CLI, or save helper
• engines that can generate a single complete WAV response for one text input
• engines that can be driven in Colab or a normal Python environment without

large custom serving infrastructure

Out of scope by default:

• research-first repos with fragile notebooks as the main inference path
• systems whose primary value is streaming, duplex audio, or realtime turn

management rather than one-shot speech generation

• engines that require nonstandard request inputs such as reference audio,

long-lived sessions, or multi-step orchestration to be useful

For out-of-scope engines, do not force them into this skill. Say that the engine does not fit the minimal OpenAI-compatible wrapper path cleanly, and either narrow the scope or use a separate workflow.

Inputs

Collect missing inputs before editing:

• source_repo: upstream TTS repository or runtime source
• runtime_env: one of colab, local-python, or server
• model_id: default model id to expose
• response_format: default wav
• cors_origins: browser origins to allow, if browser use is expected
• supports_voice_optional: whether voice should be optional; default true
• api_path: default /v1/audio/speech

Procedure

1. Inspect the upstream TTS runtime before writing wrapper code.

Classify it into one primary integration pattern:

• Pattern A: direct Python API
• Example shape: model.generate(...) returns audio or

generate_to_file(...) exists.

• Prefer this when the upstream project exposes a stable Python entrypoint.
• Pattern B: CLI or batch inference with file output
• Example shape: ./bin/piper --text ... -f output.wav.
• Prefer this when the upstream project already writes WAV reliably from a

command line interface.

• Pattern C: internal runtime plus project save helper
• Example shape: runtime.synthesize(...) plus a repo helper such as

save_wav(...).

• Prefer this when direct serialization is fragile and the upstream repo

already has a proven save path.

1. For the chosen pattern, find both:

• the canonical inference entrypoint
• the canonical audio-save path used by the repo itself

Do not assume result.audio can be serialized directly. If the repo only demonstrates inference through notebooks or research scripts, stop and reassess whether this skill is the right tool.

1. Preserve OpenAI-compatible request semantics:

• Accept application/json.
• Support model, input, optional voice, optional speed, and

optional response_format.

• If the upstream runtime has no voice concept, accept voice but treat

it as optional metadata.

1. Preserve OpenAI-compatible response semantics:

• Return raw audio bytes with media_type="audio/wav" unless another format

is explicitly requested and supported.

• Set Content-Length when practical.
• If the upstream engine only supports WAV, reject unsupported

response_format values with a clear 400.

• Do not add content-range unless implementing Range support.

1. For browser-driven examples, configure CORS explicitly:

• Prefer framework middleware over hand-written OPTIONS routes.
• Allow POST and OPTIONS.
• Allow Content-Type and Authorization.
• If browser clients need to read custom headers, expose them explicitly.

1. For Colab, isolate dependencies:

• Prefer project-local .venv or equivalent over global pip install.
• Avoid mutating the Colab base environment when possible.
• Log server output to a file such as uvicorn.log.

1. Pick the simplest wrapper that matches the upstream:

• Pattern A: call the Python API directly; prefer generate_to_file(...)

over reimplementing serialization.

• Pattern B: shell out to the CLI, write to a temporary WAV, then return the

file bytes.

• Pattern C: call the runtime directly and reuse the repo's own save helper.

Do not add nonstandard OpenAI extensions unless the user explicitly asks for them.

1. Add minimal observability:

• Persist server logs to a file.
• Return structured 500 JSON during debugging if needed.
• Keep the wrapper simple once the issue is resolved.

1. Verify in this order:

• Local root endpoint (GET /)
• Model listing (GET /v1/models) if implemented
• curl JSON request to /v1/audio/speech
• Browser request from the intended frontend
• @aituber-onair/voice integration if the wrapper is meant to be consumed

by this repo

Validation Scope

If the wrapper is intended for @aituber-onair/voice, validate both layers:

• Wrapper-only validation
• local request works
• tunnel or public URL works
• browser CORS works
• Consumer validation
• openaiCompatible in @aituber-onair/voice can fetch audio from the

wrapper

• the React example can play audio with the intended model, optional

voice, and optional API key flow

Common Failure Modes

• 422 with body.input missing:
• The server is still expecting Form(...) instead of JSON.
• Browser shows CORS but server actually failed:
• A 500 response without CORS headers often looks like a CORS failure in

the browser. Check server logs first.

• Repeatedly seeing old behavior:
• An old server process is still bound to the port. Kill it before restart.
• ModuleNotFoundError in Colab:
• The required dependency was installed into the wrong environment.
• WAV serialization failure:
• The wrapper is bypassing the upstream repo's canonical save path.
• Wrapper works with curl but not from @aituber-onair/voice:
• Check whether the consumer sends voice, speed, API key headers, and

browser-origin CORS exactly as expected.

• Reached the wrong abstraction level:
• If the upstream already exposes a reliable file-output CLI or save helper,

stop trying to invent a lower-level serialization path.

• The upstream is too research-oriented:
• If clean one-shot WAV generation is not already demonstrated, this skill is

probably the wrong abstraction.

References

• Read the compatibility checklist and debugging notes in:

skills/wrap-tts-as-openai-compatible/references/openai-compatible-tts-checklist.md

• For choosing the adapter shape, read:

skills/wrap-tts-as-openai-compatible/references/integration-patterns.md

• For @aituber-onair/voice integration and browser checks, read:

skills/wrap-tts-as-openai-compatible/references/voice-e2e-validation.md

Verification Commands

Run from the wrapper project root or notebook environment:

curl -i http://127.0.0.1:8000/
curl -i http://127.0.0.1:8000/v1/models
curl -X POST http://127.0.0.1:8000/v1/audio/speech \
  -H 'Content-Type: application/json' \
  -d '{"model":"<model_id>","input":"hello","speed":1}' \
  --output out.wav

For Colab or uvicorn-backed wrappers, also check:

tail -n 200 uvicorn.log

Acceptance Criteria

• The upstream TTS has been classified into a concrete wrapper pattern before

implementation.

• The wrapper accepts JSON requests at /v1/audio/speech.
• voice is optional when the upstream runtime does not need it.
• The response returns playable audio bytes with audio/wav.
• Browser access works when CORS is expected.
• Colab or local setup avoids unnecessary global dependency conflicts.
• The implementation uses the upstream repo's proven WAV-save path when

available.

• If the wrapper is intended for this repo, @aituber-onair/voice can use it

through the openaiCompatible path.

• The chosen upstream TTS is a practical fit for one-shot OpenAI-compatible

speech, not a forced adaptation of a research-only or streaming-first system.