From 38a2a48f28d64afb2a2d39f7f85ef3699d02a29f Mon Sep 17 00:00:00 2001
From: vince <vince@linux.dimensionlab.net>
Date: Sat, 8 Aug 2026 23:10:07 +0200
Subject: [PATCH] feat: add OpenAI-compatible Chatterbox TTS service

---
 .gitignore                                    |   9 +
 README.md                                     |  54 ++++++
 app.py                                        | 121 +++++++++++++
 .../plans/2026-08-08-chatterbox-tts.md        | 166 ++++++++++++++++++
 .../specs/2026-08-08-chatterbox-tts-design.md |  53 ++++++
 requirements.txt                              |   8 +
 tests/test_app.py                             | 158 +++++++++++++++++
 tests/test_synthesis.py                       |  51 ++++++
 voices/.gitkeep                               |   0
 9 files changed, 620 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 README.md
 create mode 100644 app.py
 create mode 100644 docs/superpowers/plans/2026-08-08-chatterbox-tts.md
 create mode 100644 docs/superpowers/specs/2026-08-08-chatterbox-tts-design.md
 create mode 100644 requirements.txt
 create mode 100644 tests/test_app.py
 create mode 100644 tests/test_synthesis.py
 create mode 100644 voices/.gitkeep

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..287bedc
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,9 @@
+.venv/
+__pycache__/
+*.py[cod]
+.pytest_cache/
+
+# Reference clips are local operational data; keep the directory in Git only.
+voices/*
+!voices/.gitkeep
+
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..09d79ec
--- /dev/null
+++ b/README.md
@@ -0,0 +1,54 @@
+# Chatterbox TTS
+
+An OpenAI-compatible, CUDA-backed FastAPI wrapper for
+[ResembleAI Chatterbox](https://huggingface.co/ResembleAI/chatterbox).
+
+The deployed service is available on the DimensionLab local network at
+`https://chatterbox.dimensionlab.net`.
+
+## API
+
+`POST /v1/audio/speech` accepts the familiar OpenAI speech fields:
+
+```json
+{
+  "model": "chatterbox",
+  "input": "Hello from Chatterbox.",
+  "voice": "reference.wav",
+  "response_format": "wav",
+  "speed": 1.0
+}
+```
+
+The response is WAV audio. `voice` is a relative path below the service's
+local `voices/` directory; absolute paths, traversal, symlink escapes, and
+unreadable files are rejected. Reference clips are operational data and are
+intentionally not part of this repository.
+
+Other endpoints:
+
+- `GET /health`
+- `GET /v1/models`
+
+## Runtime behavior
+
+- Uses the English Chatterbox model on CUDA.
+- Serializes synthesis through one GPU lock.
+- Unloads the model after 300 seconds of inactivity.
+- Caps text input at 2,000 characters.
+- Listens locally on `127.0.0.1:8881`; Caddy provides the HTTPS route.
+
+## Development
+
+```bash
+python3 -m venv .venv
+.venv/bin/pip install -r requirements.txt
+PYTHONPATH=. .venv/bin/pytest -q tests/test_app.py
+```
+
+The CUDA smoke test requires a valid local reference clip at
+`voices/reference.wav`:
+
+```bash
+PYTHONPATH=. .venv/bin/pytest -q tests/test_synthesis.py
+```
diff --git a/app.py b/app.py
new file mode 100644
index 0000000..67b5510
--- /dev/null
+++ b/app.py
@@ -0,0 +1,121 @@
+"""OpenAI-compatible speech endpoint backed by ResembleAI Chatterbox."""
+
+import gc
+import os
+import threading
+import time
+from io import BytesIO
+from pathlib import Path
+
+from fastapi import FastAPI, HTTPException
+from fastapi.responses import Response
+from pydantic import BaseModel, Field
+
+
+VOICES_DIR = Path(__file__).parent / "voices"
+IDLE_UNLOAD_SECONDS = 300
+
+
+class SpeechRequest(BaseModel):
+    model: str = "chatterbox"
+    input: str = Field(max_length=2000)
+    voice: str
+    response_format: str = "wav"
+    speed: float = 1.0
+
+
+class ModelManager:
+    """Owns the GPU model and releases it after a period of inactivity."""
+
+    def __init__(self) -> None:
+        self._model = None
+        self._unload_timer: threading.Timer | None = None
+        self._lock = threading.Lock()
+        self.last_request_time: float | None = None
+
+    def _cancel_unload_timer(self) -> None:
+        if self._unload_timer is not None:
+            self._unload_timer.cancel()
+            self._unload_timer = None
+
+    def _schedule_unload(self) -> None:
+        self._cancel_unload_timer()
+        self._unload_timer = threading.Timer(IDLE_UNLOAD_SECONDS, self.unload)
+        self._unload_timer.daemon = True
+        self._unload_timer.start()
+
+    def load_model(self):
+        if self._model is None:
+            from chatterbox.tts import ChatterboxTTS
+
+            self._model = ChatterboxTTS.from_pretrained(device="cuda")
+        return self._model
+
+    def generate(self, text: str, voice_path: Path, speed: float) -> bytes:
+        with self._lock:
+            self._cancel_unload_timer()
+            try:
+                model = self.load_model()
+                # Chatterbox does not expose a native speed control.  Keep the
+                # OpenAI-compatible field accepted without changing speech speed.
+                del speed
+                audio = model.generate(text, audio_prompt_path=str(voice_path))
+
+                import torchaudio
+
+                buffer = BytesIO()
+                torchaudio.save(buffer, audio, model.sr, format="wav")
+                return buffer.getvalue()
+            finally:
+                if self._model is not None:
+                    self.last_request_time = time.monotonic()
+                    self._schedule_unload()
+
+    def unload(self) -> None:
+        with self._lock:
+            self._cancel_unload_timer()
+            if self._model is None:
+                return
+            self._model = None
+            gc.collect()
+            import torch
+
+            torch.cuda.empty_cache()
+
+
+def resolve_voice(voice: str) -> Path:
+    candidate = Path(voice)
+    if candidate.is_absolute():
+        raise HTTPException(status_code=400, detail="voice must be a relative path")
+
+    voices_root = VOICES_DIR.resolve()
+    voice_path = Path(VOICES_DIR, voice).resolve()
+    if not voice_path.is_relative_to(voices_root):
+        raise HTTPException(status_code=400, detail="voice path escapes the voices directory")
+    if not voice_path.is_file() or not os.access(voice_path, os.R_OK):
+        raise HTTPException(status_code=400, detail="voice must be a readable regular file")
+    return voice_path
+
+
+app = FastAPI()
+model_manager = ModelManager()
+
+
+@app.get("/health")
+def health() -> dict[str, str]:
+    return {"status": "ok"}
+
+
+@app.get("/v1/models")
+def list_models() -> dict[str, list[dict[str, str]]]:
+    return {"data": [{"id": "chatterbox", "object": "model"}]}
+
+
+@app.post("/v1/audio/speech")
+def speech(request: SpeechRequest) -> Response:
+    if request.response_format != "wav":
+        raise HTTPException(status_code=400, detail="only wav response_format is supported")
+
+    voice_path = resolve_voice(request.voice)
+    audio = model_manager.generate(request.input, voice_path, request.speed)
+    return Response(content=audio, media_type="audio/wav")
diff --git a/docs/superpowers/plans/2026-08-08-chatterbox-tts.md b/docs/superpowers/plans/2026-08-08-chatterbox-tts.md
new file mode 100644
index 0000000..79de0e4
--- /dev/null
+++ b/docs/superpowers/plans/2026-08-08-chatterbox-tts.md
@@ -0,0 +1,166 @@
+# Chatterbox TTS Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Deploy an OpenAI-compatible Chatterbox text-to-speech service at `chatterbox.dimensionlab.net`.
+
+**Architecture:** A FastAPI application on loopback port 8881 wraps the CUDA Chatterbox model and exposes the standard speech endpoint. The application confines reference audio to its `voices/` directory, serializes GPU synthesis, and unloads the cached model after exactly five idle minutes. A user systemd service supervises it, and Caddy exposes the public hostname.
+
+**Tech Stack:** Python 3, FastAPI, Uvicorn, PyTorch, torchaudio, chatterbox-tts, systemd user units, Caddy.
+
+## Global Constraints
+
+- Do not change the Kokoro service or its Caddy route.
+- Bind Uvicorn to `127.0.0.1:8881` only.
+- Use the English `ResembleAI/chatterbox` model on CUDA.
+- Accept reference audio only below `/home/vince/ai/apps/chatterbox-tts/voices`.
+- Set model idle unload to exactly 300 seconds.
+- Permit at most one in-flight model synthesis request.
+- Limit `input` to 2,000 characters.
+- Support WAV responses in the first release.
+
+---
+
+### Task 1: Create and test the API module
+
+**Files:**
+- Create: `/home/vince/ai/apps/chatterbox-tts/app.py`
+- Create: `/home/vince/ai/apps/chatterbox-tts/tests/test_app.py`
+- Create: `/home/vince/ai/apps/chatterbox-tts/requirements.txt`
+- Create: `/home/vince/ai/apps/chatterbox-tts/voices/.gitkeep`
+
+**Interfaces:**
+- Produces: `app: FastAPI` with `GET /health`, `GET /v1/models`, and `POST /v1/audio/speech`.
+- Produces: `resolve_voice_path(voice: str) -> Path` and `SpeechRequest` request validation.
+
+- [ ] **Step 1: Write failing API tests**
+
+```python
+def test_models_and_health(client):
+    assert client.get('/health').json() == {'status': 'ok'}
+    assert client.get('/v1/models').json()['data'][0]['id'] == 'chatterbox'
+
+def test_voice_must_stay_under_voice_directory(client):
+    response = client.post('/v1/audio/speech', json={
+        'input': 'Hello', 'voice': '../secret.wav', 'response_format': 'wav'
+    })
+    assert response.status_code == 400
+
+def test_input_is_limited(client):
+    response = client.post('/v1/audio/speech', json={
+        'input': 'x' * 2001, 'voice': 'reference.wav', 'response_format': 'wav'
+    })
+    assert response.status_code == 422
+```
+
+- [ ] **Step 2: Run the tests to confirm they fail before implementation**
+
+Run: `cd /home/vince/ai/apps/chatterbox-tts && .venv/bin/python -m pytest tests/test_app.py -v`
+
+Expected: FAIL because `app.py` and the `app` module do not exist.
+
+- [ ] **Step 3: Implement the API and GPU model manager**
+
+Implement a `ModelManager` protected by `threading.Lock`. It must lazily call `ChatterboxTTS.from_pretrained(device='cuda')`, update `last_request_time` at synthesis start, and have a daemon that clears the model and calls `torch.cuda.empty_cache()` when idle for 300 seconds. Guard the full inference call with the same lock. Resolve `voice` with `Path(VOICES_DIR, voice).resolve()` and reject it unless `relative_to(VOICES_DIR.resolve())` succeeds. Use `torchaudio.save` to write the generated tensor to an in-memory WAV buffer.
+
+```python
+@app.post('/v1/audio/speech')
+def speech(request: SpeechRequest) -> Response:
+    reference = resolve_voice_path(request.voice)
+    wav, sample_rate = model_manager.generate(request.input, reference)
+    buffer = io.BytesIO()
+    torchaudio.save(buffer, wav.cpu(), sample_rate, format='wav')
+    return Response(buffer.getvalue(), media_type='audio/wav')
+```
+
+- [ ] **Step 4: Run the focused tests**
+
+Run: `cd /home/vince/ai/apps/chatterbox-tts && .venv/bin/python -m pytest tests/test_app.py -v`
+
+Expected: PASS without loading the CUDA model for health, model-list, length, or invalid-path cases.
+
+### Task 2: Install isolated dependencies and verify real synthesis
+
+**Files:**
+- Modify: `/home/vince/ai/apps/chatterbox-tts/requirements.txt`
+- Create: `/home/vince/ai/apps/chatterbox-tts/tests/test_synthesis.py`
+
+**Interfaces:**
+- Consumes: `app.model_manager.generate(text, voice_path)`.
+- Produces: a WAV-producing Chatterbox runtime in `.venv`.
+
+- [ ] **Step 1: Write the failing real-synthesis test**
+
+```python
+def test_generate_returns_audio_tensor_and_sample_rate(reference_wav):
+    wav, sample_rate = model_manager.generate('A short Chatterbox smoke test.', reference_wav)
+    assert wav.numel() > 0
+    assert sample_rate > 0
+```
+
+- [ ] **Step 2: Install the project environment**
+
+Run: `cd /home/vince/ai/apps/chatterbox-tts && python3 -m venv .venv && .venv/bin/pip install --upgrade pip && .venv/bin/pip install -r requirements.txt`
+
+Expected: `chatterbox-tts`, CUDA-compatible PyTorch/torchaudio, FastAPI, Uvicorn, Pydantic, and pytest install into `.venv` only.
+
+- [ ] **Step 3: Add a short, consented reference WAV to `voices/`**
+
+Use one existing, locally owned test WAV as `voices/reference.wav`; do not copy any credentials or unrelated files.
+
+- [ ] **Step 4: Run the real-synthesis test**
+
+Run: `cd /home/vince/ai/apps/chatterbox-tts && .venv/bin/python -m pytest tests/test_synthesis.py -v -s`
+
+Expected: PASS and the CUDA model is released after the test process exits.
+
+### Task 3: Supervise and publish the service
+
+**Files:**
+- Create: `/home/vince/.config/systemd/user/chatterbox-tts.service`
+- Create: `/etc/caddy/conf.d/chatterbox.caddy`
+
+**Interfaces:**
+- Consumes: `app:app` from `app.py`.
+- Produces: loopback service on port 8881 and HTTPS public hostname.
+
+- [ ] **Step 1: Create the systemd user unit**
+
+Use `WorkingDirectory=/home/vince/ai/apps/chatterbox-tts` and:
+
+```ini
+ExecStart=/home/vince/ai/apps/chatterbox-tts/.venv/bin/uvicorn app:app --host 127.0.0.1 --port 8881
+Restart=on-failure
+RestartSec=5
+```
+
+- [ ] **Step 2: Create the Caddy route**
+
+```caddyfile
+chatterbox.dimensionlab.net {
+    import cloudflare_tls
+    reverse_proxy 127.0.0.1:8881
+}
+```
+
+- [ ] **Step 3: Validate configuration and activate services**
+
+Run: `systemctl --user daemon-reload && systemctl --user enable --now chatterbox-tts.service && /usr/local/bin/caddy-cloudflare validate --config /etc/caddy/Caddyfile && sudo systemctl reload caddy`
+
+Expected: the user unit is active, Caddy validates, and the public route is loaded.
+
+- [ ] **Step 4: Verify the full public API path**
+
+Run:
+
+```bash
+curl -fsS https://chatterbox.dimensionlab.net/health
+curl -fsS https://chatterbox.dimensionlab.net/v1/models
+curl -fsS -o /tmp/chatterbox-smoke.wav \
+  -H 'Content-Type: application/json' \
+  -d '{"model":"chatterbox","input":"Service smoke test.","voice":"reference.wav","response_format":"wav"}' \
+  https://chatterbox.dimensionlab.net/v1/audio/speech
+file /tmp/chatterbox-smoke.wav
+```
+
+Expected: health and models return JSON, speech returns an RIFF/WAVE file, and no listener is exposed on a non-loopback interface for port 8881.
diff --git a/docs/superpowers/specs/2026-08-08-chatterbox-tts-design.md b/docs/superpowers/specs/2026-08-08-chatterbox-tts-design.md
new file mode 100644
index 0000000..0502140
--- /dev/null
+++ b/docs/superpowers/specs/2026-08-08-chatterbox-tts-design.md
@@ -0,0 +1,53 @@
+# Chatterbox TTS service design
+
+## Goal
+
+Run ResembleAI Chatterbox as an independent GPU-backed text-to-speech service,
+available at `https://chatterbox.dimensionlab.net`, while preserving the
+existing Kokoro service unchanged.
+
+## Architecture
+
+`chatterbox-tts` is a small Python FastAPI application in
+`/home/vince/ai/apps/chatterbox-tts`. A user-level systemd unit runs it on
+loopback port 8881. Caddy terminates TLS for `chatterbox.dimensionlab.net` and
+reverse-proxies that hostname to `127.0.0.1:8881`.
+
+The application loads the English `ResembleAI/chatterbox` model on CUDA lazily.
+It keeps the model resident while requests are active, then frees its GPU
+allocation after five minutes without a synthesis request. A single-request GPU
+lock serializes synthesis and model unload operations. This lets it coexist
+with the existing Kokoro service and other GPU workloads without competing
+requests exhausting VRAM.
+
+## API contract
+
+The service provides:
+
+- `POST /v1/audio/speech`, accepting the OpenAI speech request fields
+  `model`, `input`, `voice`, `response_format`, and `speed`.
+- `GET /v1/models`, returning the available Chatterbox model identifier.
+- `GET /health`, returning a small health response without forcing model load.
+
+`POST /v1/audio/speech` returns generated WAV audio. `model` defaults to
+`chatterbox`; `response_format` accepts `wav`; and `input` is capped at 2,000
+characters. The request's `voice` field is a path relative to the dedicated
+`/home/vince/ai/apps/chatterbox-tts/voices` directory. The resolved path must
+remain within that directory, exist, and be readable by the service user before
+it is supplied as Chatterbox's reference clip. Invalid, missing, or escaping
+paths fail with a clear 400 response. No upload endpoint or voice catalogue is
+part of this first version.
+
+## Failure handling
+
+Malformed requests, unsupported formats, invalid paths, model-download/load
+failures, and synthesis errors produce JSON errors. A process crash is restarted
+by systemd. Caddy continues to expose only the public hostname; the Python
+service is not publicly bound.
+
+## Verification
+
+Verify the unit reaches active status, loopback port 8881 serves `/health`, and
+the public hostname reaches it through Caddy. Exercise `/v1/models` and a
+short `/v1/audio/speech` request using a known local reference WAV, checking
+that the response is valid WAV audio.
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..b0238e0
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,8 @@
+fastapi
+uvicorn[standard]
+pydantic
+pytest
+setuptools<81
+chatterbox-tts==0.1.7
+torch==2.6.0
+torchaudio==2.6.0
diff --git a/tests/test_app.py b/tests/test_app.py
new file mode 100644
index 0000000..d9c349d
--- /dev/null
+++ b/tests/test_app.py
@@ -0,0 +1,158 @@
+import os
+import time
+from pathlib import Path
+
+import pytest
+from fastapi.testclient import TestClient
+
+import app as chatterbox_app
+from app import ModelManager, app
+
+
+client = TestClient(app)
+
+
+def speech_payload(**overrides):
+    payload = {
+        "input": "Hello from Chatterbox.",
+        "voice": "reference.wav",
+    }
+    payload.update(overrides)
+    return payload
+
+
+def configure_voices(monkeypatch, tmp_path):
+    voices_dir = tmp_path / "voices"
+    voices_dir.mkdir()
+    monkeypatch.setattr(chatterbox_app, "VOICES_DIR", voices_dir)
+    return voices_dir
+
+
+def test_health_returns_ok_without_calling_model_loader(monkeypatch):
+    def fail_if_called(*args, **kwargs):
+        raise AssertionError("model loader must not be called")
+
+    monkeypatch.setattr(ModelManager, "load_model", fail_if_called)
+    response = client.get("/health")
+
+    assert response.status_code == 200
+    assert response.json() == {"status": "ok"}
+
+
+def test_models_lists_chatterbox_without_calling_model_loader(monkeypatch):
+    def fail_if_called(*args, **kwargs):
+        raise AssertionError("model loader must not be called")
+
+    monkeypatch.setattr(ModelManager, "load_model", fail_if_called)
+    response = client.get("/v1/models")
+
+    assert response.status_code == 200
+    assert response.json()["data"][0]["id"] == "chatterbox"
+
+
+def test_speech_rejects_voice_path_traversal():
+    response = client.post("/v1/audio/speech", json=speech_payload(voice="../secret.wav"))
+
+    assert response.status_code == 400
+
+
+def test_speech_rejects_absolute_voice_path():
+    response = client.post(
+        "/v1/audio/speech",
+        json=speech_payload(voice=str(Path(chatterbox_app.VOICES_DIR) / "reference.wav")),
+    )
+
+    assert response.status_code == 400
+
+
+def test_speech_rejects_missing_voice_file():
+    response = client.post(
+        "/v1/audio/speech",
+        json=speech_payload(voice="definitely-not-present-reference.wav"),
+    )
+
+    assert response.status_code == 400
+
+
+def test_speech_rejects_input_over_2000_characters():
+    response = client.post("/v1/audio/speech", json=speech_payload(input="x" * 2001))
+
+    assert response.status_code == 422
+
+
+def test_speech_rejects_unsupported_response_format():
+    response = client.post(
+        "/v1/audio/speech", json=speech_payload(response_format="mp3")
+    )
+
+    assert response.status_code == 400
+
+
+def test_speech_rejects_symlink_escaping_voices_directory(monkeypatch, tmp_path):
+    voices_dir = configure_voices(monkeypatch, tmp_path)
+    outside_voice = tmp_path / "outside.wav"
+    outside_voice.write_bytes(b"not really wav")
+    try:
+        (voices_dir / "escape.wav").symlink_to(outside_voice)
+    except OSError as error:
+        pytest.skip(f"symlinks are unavailable on this OS: {error}")
+
+    response = client.post("/v1/audio/speech", json=speech_payload(voice="escape.wav"))
+
+    assert response.status_code == 400
+
+
+def test_speech_rejects_directory_as_voice_target(monkeypatch, tmp_path):
+    voices_dir = configure_voices(monkeypatch, tmp_path)
+    (voices_dir / "voice-dir").mkdir()
+
+    response = client.post("/v1/audio/speech", json=speech_payload(voice="voice-dir"))
+
+    assert response.status_code == 400
+
+
+def test_speech_rejects_unreadable_voice_target(monkeypatch, tmp_path):
+    if os.geteuid() == 0:
+        pytest.skip("root can read files regardless of their permission bits")
+    voices_dir = configure_voices(monkeypatch, tmp_path)
+    voice = voices_dir / "unreadable.wav"
+    voice.write_bytes(b"not really wav")
+    voice.chmod(0)
+
+    try:
+        response = client.post("/v1/audio/speech", json=speech_payload(voice="unreadable.wav"))
+    finally:
+        voice.chmod(0o600)
+
+    assert response.status_code == 400
+
+
+def test_speech_accepts_exactly_2000_characters(monkeypatch, tmp_path):
+    voices_dir = configure_voices(monkeypatch, tmp_path)
+    (voices_dir / "reference.wav").write_bytes(b"not really wav")
+    monkeypatch.setattr(chatterbox_app.model_manager, "generate", lambda *args: b"wav")
+
+    response = client.post("/v1/audio/speech", json=speech_payload(input="x" * 2000))
+
+    assert response.status_code == 200
+    assert response.headers["content-type"] == "audio/wav"
+    assert response.content == b"wav"
+
+
+def test_generation_failure_still_records_idle_unload_time():
+    class FailingModel:
+        def generate(self, *args, **kwargs):
+            raise RuntimeError("synthesis failed")
+
+    manager = ModelManager()
+    manager._model = FailingModel()
+    before_request = time.monotonic()
+
+    with pytest.raises(RuntimeError, match="synthesis failed"):
+        manager.generate("hello", Path("reference.wav"), 1.0)
+
+    try:
+        assert manager.last_request_time >= before_request
+        assert manager._unload_timer is not None
+    finally:
+        manager._cancel_unload_timer()
diff --git a/tests/test_synthesis.py b/tests/test_synthesis.py
new file mode 100644
index 0000000..84f73c3
--- /dev/null
+++ b/tests/test_synthesis.py
@@ -0,0 +1,51 @@
+"""CUDA smoke coverage for the real Chatterbox synthesis path."""
+
+from pathlib import Path
+
+import pytest
+import torch
+import torchaudio
+
+import app as chatterbox_app
+
+
+def test_runtime_requirements_pin_chatterbox_cuda_contract():
+    requirements = {
+        line.strip()
+        for line in (Path(__file__).parents[1] / "requirements.txt").read_text().splitlines()
+        if line.strip() and not line.startswith("#")
+    }
+
+    assert {
+        "chatterbox-tts==0.1.7",
+        "torch==2.6.0",
+        "torchaudio==2.6.0",
+        "pydantic",
+        "setuptools<81",
+        "pytest",
+    } <= requirements
+
+
+def test_chatterbox_generates_cuda_audio_from_reference_voice(tmp_path: Path):
+    """The app wrapper returns real, decodable CUDA-synthesized WAV audio."""
+    if not torch.cuda.is_available():
+        pytest.skip("CUDA is unavailable")
+
+    reference = chatterbox_app.VOICES_DIR / "reference.wav"
+    assert reference.is_file(), "voices/reference.wav must be available for synthesis"
+    manager = chatterbox_app.model_manager
+
+    try:
+        wav_bytes = manager.generate("Chatterbox CUDA smoke test.", reference, 1.0)
+    finally:
+        manager.unload()
+
+    output_path = tmp_path / "chatterbox-cuda-smoke.wav"
+    output_path.write_bytes(wav_bytes)
+    waveform, sample_rate = torchaudio.load(output_path)
+    assert isinstance(waveform, torch.Tensor)
+    assert waveform.ndim == 2
+    assert waveform.shape[0] == 1
+    assert waveform.numel() > 0
+    assert sample_rate > 0
+    assert output_path.stat().st_size > 44
diff --git a/voices/.gitkeep b/voices/.gitkeep
new file mode 100644
index 0000000..e69de29