feat(stt): real Korean STT via persistent faster-whisper worker

Step 3 (귀): add WhisperSTT + whisper_worker, a warm out-of-venv worker
mirroring the MeloTTS shape (whisper312 venv, small/int8 on CPU). transcribe()
closes the voice round trip (MeloTTS wav -> whisper text); utterances() turns an
injected audio_source into Utterances (Discord voice feed pending). Wired into
factory as WSAI_STT=whisper.

Also address the arbiter's TTS follow-ups:
- melo worker error handling: capture stderr (drained in a bounded background
  task so the pipe can't fill), surface the real failure cause, and defend
  against an empty/invalid ready line instead of dying on JSONDecodeError.
- pipeline pre-warm: load slow backends (warmup()) at startup so the first
  utterance is answered warm; a warmup failure is logged, not fatal.

Verified: real TTS->STT round trip recovers the sentence near-perfectly;
warm transcribe ~1.2s (CPU). 12 tests pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -171,8 +171,9 @@ ffmpeg 디코드 → 프레임. DAVE는 `@snazzah/davey`(Rust NAPI), 수신은 `
       · 검증: `python -m wsai --voice`가 화면 없이 발화마다 응답을 낸다(테스트 포함).
 - [ ] **V1 · 진짜 TTS(입).** MeloTTS로 두뇌 응답을 실제 음성으로 합성.
       · 검증: 응답 텍스트가 .wav로 합성돼 들린다.
-- [ ] **V2 · 진짜 STT(귀).** faster-whisper로 오디오를 텍스트로 전사.
+- [x] **V2 · 진짜 STT(귀) — 엔진 완성.** faster-whisper(상주 워커, `WSAI_STT=whisper`)로 wav를 한국어 텍스트로 전사.
-      · 검증: 오디오 파일 입력이 텍스트로 나온다(이후 디스코드 보이스 수신 오디오로 연결).
+      · 검증: 실제 왕복(MeloTTS wav → whisper)에서 문장이 거의 그대로 복원됨. warm 전사 ~1.2s(CPU, small/int8).
+      · 남은 것: 디스코드 보이스 수신 오디오(`audio_source`)를 붙여 실시간 발화 스트림으로 연결(V4).
 - [ ] **V3 · 진짜 두뇌.** Claude OAuth(Haiku)로 대화 응답 생성.
       · 검증: 실제 발화에 자연스러운 답이 나온다.
 - [ ] **V4 · 음성 왕복 + barge-in.** 디스코드 보이스 수신→STT→Brain→TTS 스트리밍, 말 끊기, 지연 측정.

requirements.txt

@@ -8,10 +8,13 @@
 # --- cloud eyes + brain (WSAI_VISION=claude / WSAI_BRAIN=claude) ---
 # anthropic
 
-# --- planned voice backends (not yet implemented) ---
+# --- voice backends (run in their OWN venvs; loaded as persistent workers) ---
-# faster-whisper      # STT (input = Discord voice reception, not a local mic)
+# STT: faster-whisper  (WSAI_STT=whisper) — installed in a dedicated venv, e.g.
-# (Opus decode for Discord voice audio, e.g. via the selfbot/ffmpeg path)
+#   uv venv --python 3.12 /home/claude/jarvis-stt/whisper312
-# (a Korean TTS engine, e.g. MeloTTS)
+#   uv pip install --python /home/claude/jarvis-stt/whisper312/bin/python faster-whisper
+#   (override interpreter/model via WSAI_WHISPER_PYTHON / WSAI_WHISPER_MODEL)
+# TTS: MeloTTS         (WSAI_TTS=melo)     — in /home/claude/jarvis-tts/melo311
+# (Opus decode for Discord voice audio, e.g. via the selfbot/ffmpeg path — pending)
 
 # --- dev ---
 # pytest

tests/test_pipeline.py

@@ -108,3 +108,29 @@ def test_history_is_bounded():
         pipe._remember(f"u{i}", f"a{i}")
     assert len(pipe._history) == 3
     assert pipe._history[-1] == ("u9", "a9")
+
+
+def test_prewarm_warms_backends_and_survives_failure():
+    """Backends exposing warmup() are preloaded at startup; a warmup that
+    raises is logged but must not abort the run (first-utterance latency is an
+    optimization, not a hard requirement)."""
+    warmed: list[str] = []
+
+    class WarmTTS(MockTTS):
+        async def warmup(self):
+            warmed.append("tts")
+
+    class BoomWarmSTT(MockSTT):
+        async def warmup(self):
+            warmed.append("stt")
+            raise RuntimeError("model unavailable")
+
+    pipe = Pipeline(
+        brain=MockBrain(),
+        stt=BoomWarmSTT(script=["안녕"], interval=0.01),
+        tts=WarmTTS(),
+    )
+
+    asyncio.run(asyncio.wait_for(pipe.run(), timeout=5))
+
+    assert "tts" in warmed and "stt" in warmed, "warmup() not called on backends"

tests/test_whisper_stt.py

@@ -0,0 +1,60 @@
+"""Unit tests for the WhisperSTT source plumbing.
+
+These do NOT load a model or spawn the worker (that needs the whisper312 venv and
+is exercised by the manual TTS->STT round trip). They pin the SpeechToText
+contract: how `utterances()` turns an audio source into Utterances, and how it
+behaves with no source wired yet.
+"""
+
+import asyncio
+from typing import AsyncIterator
+
+from wsai.backends.whisper import WhisperSTT
+from wsai.interfaces import SpeechToText, Utterance
+
+
+def _collect(stt: WhisperSTT) -> list[Utterance]:
+    async def run():
+        return [u async for u in stt.utterances()]
+
+    return asyncio.run(asyncio.wait_for(run(), timeout=5))
+
+
+async def _paths(items) -> AsyncIterator[str]:
+    for it in items:
+        yield it
+
+
+def test_is_speech_to_text():
+    assert isinstance(WhisperSTT(), SpeechToText)
+
+
+def test_no_audio_source_yields_nothing():
+    # Discord voice receiver not wired yet -> the loop idles and returns.
+    assert _collect(WhisperSTT(audio_source=None)) == []
+
+
+def test_utterances_transcribes_each_chunk(monkeypatch):
+    stt = WhisperSTT(audio_source=_paths(["a.wav", "b.wav"]))
+
+    async def fake_transcribe(wav_path, *, language=None):
+        return f"text::{wav_path}"
+
+    monkeypatch.setattr(stt, "transcribe", fake_transcribe)
+
+    utts = _collect(stt)
+    assert [u.text for u in utts] == ["text::a.wav", "text::b.wav"]
+    assert all(u.source == "voice" for u in utts)
+
+
+def test_empty_transcript_is_skipped(monkeypatch):
+    # Silence / VAD-filtered audio transcribes to "" and must not become a turn.
+    stt = WhisperSTT(audio_source=_paths(["silent.wav", "real.wav"]))
+
+    async def fake_transcribe(wav_path, *, language=None):
+        return "" if wav_path == "silent.wav" else "안녕"
+
+    monkeypatch.setattr(stt, "transcribe", fake_transcribe)
+
+    utts = _collect(stt)
+    assert [u.text for u in utts] == ["안녕"]

wsai/backends/melo.py

@@ -17,6 +17,7 @@ Env:
 from __future__ import annotations
 
 import asyncio
+import collections
 import json
 import logging
 import os
@@ -59,6 +60,37 @@ class MeloTTS:
         self._lock = asyncio.Lock()
         self._n = 0
         self.load_ms: int | None = None
+        # Keep the worker's most recent stderr lines so a crash reports its real
+        # cause instead of a bare JSONDecodeError. Bounded so it can't grow.
+        self._stderr_tail: collections.deque[str] = collections.deque(maxlen=40)
+        self._stderr_task: asyncio.Task | None = None
+
+    async def _drain_stderr(self, stream: asyncio.StreamReader) -> None:
+        # The worker redirects fd1 -> fd2, so ALL library chatter lands on
+        # stderr. If we PIPE stderr but never read it, the OS pipe buffer fills
+        # and the worker blocks forever. So we continuously drain it and keep
+        # only the last few lines for diagnostics.
+        try:
+            while True:
+                line = await stream.readline()
+                if not line:
+                    return
+                self._stderr_tail.append(line.decode(errors="replace").rstrip())
+        except asyncio.CancelledError:
+            raise
+        except Exception:  # draining must never crash the caller
+            return
+
+    def _stderr_hint(self) -> str:
+        tail = "\n".join(self._stderr_tail)
+        return f" worker stderr tail:\n{tail}" if tail else " (worker produced no stderr)"
+
+    async def warmup(self) -> None:
+        """Start and load the worker now so the first real utterance is warm.
+
+        Called at pipeline startup so users don't wait ~7s (CPU model load) for
+        the very first spoken reply."""
+        await self._ensure()
 
     async def _ensure(self) -> None:
         if self._proc is not None and self._proc.returncode is None:
@@ -72,12 +104,29 @@ class MeloTTS:
             cwd=repo_root, env=env,
             stdin=asyncio.subprocess.PIPE,
             stdout=asyncio.subprocess.PIPE,
-            stderr=asyncio.subprocess.DEVNULL,
+            stderr=asyncio.subprocess.PIPE,
         )
+        self._stderr_tail.clear()
+        assert self._proc.stderr is not None
+        self._stderr_task = asyncio.create_task(self._drain_stderr(self._proc.stderr))
         ready = await self._proc.stdout.readline()
+        if not ready:  # worker died before signalling ready
+            await self._proc.wait()
+            raise RuntimeError(
+                f"melo worker exited before ready (code {self._proc.returncode})."
+                f"{self._stderr_hint()}"
+            )
+        try:
             info = json.loads(ready.decode())
+        except json.JSONDecodeError as exc:
+            raise RuntimeError(
+                f"melo worker sent invalid ready line {ready!r}: {exc}."
+                f"{self._stderr_hint()}"
+            ) from exc
         if not info.get("ready"):
-            raise RuntimeError(f"melo worker failed to start: {info}")
+            raise RuntimeError(
+                f"melo worker failed to start: {info}.{self._stderr_hint()}"
+            )
         self.load_ms = info.get("ms")
         log.info("melo worker ready in %s ms on %s", self.load_ms, info.get("device"))
 
@@ -93,7 +142,7 @@ class MeloTTS:
             await self._proc.stdin.drain()
             resp = await self._proc.stdout.readline()
         if not resp:
-            raise RuntimeError("melo worker closed unexpectedly")
+            raise RuntimeError(f"melo worker closed unexpectedly.{self._stderr_hint()}")
         res = json.loads(resp.decode())
         if not res.get("ok"):
             raise RuntimeError(f"melo synth failed: {res.get('error')}")
@@ -107,4 +156,11 @@ class MeloTTS:
                 await asyncio.wait_for(self._proc.wait(), timeout=5)
             except (ProcessLookupError, asyncio.TimeoutError):
                 pass
+        if self._stderr_task is not None:
+            self._stderr_task.cancel()
+            try:
+                await self._stderr_task
+            except (asyncio.CancelledError, Exception):
+                pass
+            self._stderr_task = None
         self._proc = None

wsai/backends/whisper.py

@@ -0,0 +1,187 @@
+"""Real STT via faster-whisper, run as a persistent out-of-venv worker.
+
+faster-whisper needs its own interpreter (whisper312) and loading the model
+costs several seconds, so we keep one worker process alive and stream
+transcription requests to it (see whisper_worker.py for the protocol) — the
+same warm-worker shape as MeloTTS on the TTS side.
+
+`transcribe(wav)` is the core engine: hand it a wav path, get the recognised
+text back. It is what closes the voice round trip (TTS wav -> STT text) and what
+the Discord voice path will call once per detected utterance.
+
+`utterances()` turns this into a SpeechToText source: it pulls finished-utterance
+wav paths from an injected `audio_source` and yields a transcribed Utterance for
+each. Until the Discord voice receiver is wired, `audio_source` is None and the
+loop simply idles (like the eyes-free perception loop), while `transcribe()`
+stays usable directly.
+
+Env:
+    WSAI_WHISPER_PYTHON    interpreter with faster-whisper installed
+                           (default: /home/claude/jarvis-stt/whisper312/bin/python)
+    WSAI_WHISPER_MODEL     model size/name (default: small)
+    WSAI_WHISPER_DEVICE    cpu | cuda   (default cpu; cuda needs GPU approval)
+    WSAI_WHISPER_LANGUAGE  forced language, e.g. ko (default ko; "" = autodetect)
+"""
+
+from __future__ import annotations
+
+import asyncio
+import collections
+import json
+import logging
+import os
+import time
+from pathlib import Path
+from typing import AsyncIterator
+
+from ..interfaces import Utterance
+
+log = logging.getLogger("wsai.stt.whisper")
+
+_DEFAULT_PYTHON = "/home/claude/jarvis-stt/whisper312/bin/python"
+
+
+class WhisperSTT:
+    def __init__(
+        self,
+        *,
+        python: str | None = None,
+        model: str | None = None,
+        device: str | None = None,
+        language: str | None = None,
+        audio_source: AsyncIterator[str] | None = None,
+    ) -> None:
+        self.python = python or os.environ.get("WSAI_WHISPER_PYTHON", _DEFAULT_PYTHON)
+        self.model = model or os.environ.get("WSAI_WHISPER_MODEL", "small")
+        self.device = device or os.environ.get("WSAI_WHISPER_DEVICE", "cpu")
+        # "" means autodetect; a real code like "ko" forces the language.
+        env_lang = os.environ.get("WSAI_WHISPER_LANGUAGE", "ko")
+        self.language = language if language is not None else (env_lang or None)
+        self.audio_source = audio_source
+        self._proc: asyncio.subprocess.Process | None = None
+        self._lock = asyncio.Lock()
+        self.load_ms: int | None = None
+        # Keep the worker's most recent stderr so a crash reports its real cause
+        # instead of a bare JSONDecodeError. Bounded so it can't grow unbounded.
+        self._stderr_tail: collections.deque[str] = collections.deque(maxlen=40)
+        self._stderr_task: asyncio.Task | None = None
+
+    async def _drain_stderr(self, stream: asyncio.StreamReader) -> None:
+        # The worker redirects fd1 -> fd2, so model/library chatter lands on
+        # stderr. If we PIPE but never read it, the pipe buffer fills and the
+        # worker blocks. So we drain continuously, keeping only the last lines.
+        try:
+            while True:
+                line = await stream.readline()
+                if not line:
+                    return
+                self._stderr_tail.append(line.decode(errors="replace").rstrip())
+        except asyncio.CancelledError:
+            raise
+        except Exception:  # draining must never crash the caller
+            return
+
+    def _stderr_hint(self) -> str:
+        tail = "\n".join(self._stderr_tail)
+        return f" worker stderr tail:\n{tail}" if tail else " (worker produced no stderr)"
+
+    async def warmup(self) -> None:
+        """Load the model now so the first real utterance is transcribed warm."""
+        await self._ensure()
+
+    async def _ensure(self) -> None:
+        if self._proc is not None and self._proc.returncode is None:
+            return
+        env = {
+            **os.environ,
+            "WSAI_WHISPER_MODEL": self.model,
+            "WSAI_WHISPER_DEVICE": self.device,
+        }
+        if self.language:
+            env["WSAI_WHISPER_LANGUAGE"] = self.language
+        repo_root = str(Path(__file__).resolve().parents[2])
+        self._proc = await asyncio.create_subprocess_exec(
+            self.python, "-m", "wsai.backends.whisper_worker",
+            cwd=repo_root, env=env,
+            stdin=asyncio.subprocess.PIPE,
+            stdout=asyncio.subprocess.PIPE,
+            stderr=asyncio.subprocess.PIPE,
+        )
+        self._stderr_tail.clear()
+        assert self._proc.stderr is not None
+        self._stderr_task = asyncio.create_task(self._drain_stderr(self._proc.stderr))
+        ready = await self._proc.stdout.readline()
+        if not ready:  # worker died before signalling ready
+            await self._proc.wait()
+            raise RuntimeError(
+                f"whisper worker exited before ready (code {self._proc.returncode})."
+                f"{self._stderr_hint()}"
+            )
+        try:
+            info = json.loads(ready.decode())
+        except json.JSONDecodeError as exc:
+            raise RuntimeError(
+                f"whisper worker sent invalid ready line {ready!r}: {exc}."
+                f"{self._stderr_hint()}"
+            ) from exc
+        if not info.get("ready"):
+            raise RuntimeError(
+                f"whisper worker failed to start: {info}.{self._stderr_hint()}"
+            )
+        self.load_ms = info.get("ms")
+        log.info(
+            "whisper worker ready in %s ms on %s (model %s)",
+            self.load_ms, info.get("device"), info.get("model"),
+        )
+
+    async def transcribe(self, wav_path: str, *, language: str | None = None) -> str:
+        """Transcribe one wav file to text using the warm worker."""
+        await self._ensure()
+        req: dict[str, object] = {"wav": wav_path}
+        lang = language if language is not None else self.language
+        if lang:
+            req["language"] = lang
+        s = time.monotonic()
+        async with self._lock:
+            assert self._proc and self._proc.stdin and self._proc.stdout
+            self._proc.stdin.write((json.dumps(req) + "\n").encode())
+            await self._proc.stdin.drain()
+            resp = await self._proc.stdout.readline()
+        if not resp:
+            raise RuntimeError(f"whisper worker closed unexpectedly.{self._stderr_hint()}")
+        res = json.loads(resp.decode())
+        if not res.get("ok"):
+            raise RuntimeError(f"whisper transcribe failed: {res.get('error')}")
+        log.debug(
+            "transcribe %d ms (worker %s ms): %s",
+            int((time.monotonic() - s) * 1000), res.get("ms"), res.get("text", "")[:60],
+        )
+        return res.get("text", "")
+
+    async def utterances(self) -> AsyncIterator[Utterance]:
+        """Yield an Utterance per finished-utterance wav from `audio_source`.
+
+        With no audio source wired yet (Discord voice receiver pending) this
+        idles and returns, leaving the voice loop dormant but valid."""
+        if self.audio_source is None:
+            return
+        async for wav_path in self.audio_source:
+            text = await self.transcribe(wav_path)
+            if text:
+                yield Utterance(text=text, ts=time.monotonic(), source="voice")
+
+    async def aclose(self) -> None:
+        if self._proc is not None and self._proc.returncode is None:
+            try:
+                self._proc.terminate()
+                await asyncio.wait_for(self._proc.wait(), timeout=5)
+            except (ProcessLookupError, asyncio.TimeoutError):
+                pass
+        if self._stderr_task is not None:
+            self._stderr_task.cancel()
+            try:
+                await self._stderr_task
+            except (asyncio.CancelledError, Exception):
+                pass
+            self._stderr_task = None
+        self._proc = None

wsai/backends/whisper_worker.py

@@ -0,0 +1,81 @@
+"""Persistent faster-whisper STT worker.
+
+faster-whisper (ctranslate2) lives in its own Python (whisper312); loading the
+model takes seconds, so we load it ONCE here and then serve transcription
+requests over stdin/stdout. This process is launched with the whisper312
+interpreter by wsai.backends.whisper.WhisperSTT.
+
+Like the MeloTTS worker, model/backend chatter could corrupt the JSON protocol,
+so on startup we split the streams: a private duplicate of the original stdout
+carries the protocol, and fd 1 is redirected to fd 2 so any library print lands
+on stderr instead (where the parent drains it for diagnostics).
+
+Protocol (one JSON object per line, on the protocol channel):
+    <- {"wav": "/abs/path.wav", "language": "ko"}
+    -> {"ok": true, "text": "...", "language": "ko", "ms": 123}
+    -> {"ok": false, "error": "..."}
+On startup, once the model is ready, it emits exactly one line:
+    -> {"ready": true, "ms": <load-ms>, "device": "cpu", "model": "small"}
+"""
+
+import json
+import os
+import sys
+import time
+
+# Split protocol from library noise BEFORE importing anything heavy.
+_proto = os.fdopen(os.dup(1), "w", buffering=1)  # private copy of real stdout
+os.dup2(2, 1)  # fd1 -> stderr, so stray library prints don't hit the protocol
+
+
+def _emit(obj: dict) -> None:
+    _proto.write(json.dumps(obj, ensure_ascii=False) + "\n")
+    _proto.flush()
+
+
+def _log(*a):
+    print(*a, file=sys.stderr, flush=True)
+
+
+def main() -> None:
+    model_name = os.environ.get("WSAI_WHISPER_MODEL", "small")
+    device = os.environ.get("WSAI_WHISPER_DEVICE", "cpu")  # "cpu" | "cuda"
+    # int8 on CPU keeps a small model fast; float16 is the usual CUDA choice.
+    compute = os.environ.get(
+        "WSAI_WHISPER_COMPUTE", "int8" if device == "cpu" else "float16"
+    )
+    default_lang = os.environ.get("WSAI_WHISPER_LANGUAGE", "ko") or None
+
+    t0 = time.monotonic()
+    from faster_whisper import WhisperModel  # heavy import; only in whisper venv
+
+    model = WhisperModel(model_name, device=device, compute_type=compute)
+    load_ms = int((time.monotonic() - t0) * 1000)
+    _emit({"ready": True, "ms": load_ms, "device": device, "model": model_name})
+    _log(f"[whisper_worker] {model_name} ready in {load_ms} ms on {device}/{compute}")
+
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            req = json.loads(line)
+            wav = req["wav"]
+            language = req.get("language", default_lang)
+            s = time.monotonic()
+            segments, info = model.transcribe(
+                wav,
+                language=language,
+                beam_size=int(req.get("beam_size", 5)),
+                vad_filter=bool(req.get("vad_filter", True)),
+            )
+            text = "".join(seg.text for seg in segments).strip()
+            ms = int((time.monotonic() - s) * 1000)
+            _emit({"ok": True, "text": text, "language": info.language, "ms": ms})
+        except Exception as exc:  # keep the worker alive across bad requests
+            _emit({"ok": False, "error": f"{type(exc).__name__}: {exc}"})
+            _log(f"[whisper_worker] error: {exc}")
+
+
+if __name__ == "__main__":
+    main()

wsai/config.py

@@ -18,7 +18,7 @@ from dataclasses import dataclass
 class Settings:
     source: str | None = "mock"  # mock | mss | None (eyes-free)
     vision: str | None = "mock"  # mock | claude | None (eyes-free)
-    stt: str | None = "mock"     # mock | (whisper) | None
+    stt: str | None = "mock"     # mock | whisper   | None
     tts: str | None = "mock"     # mock | melo      | None
     brain: str = "mock"          # mock | claude
     text: str | None = None      # None | (discord)

wsai/factory.py

@@ -69,6 +69,10 @@ def _brain(s: Settings):
 def _stt(s: Settings):
     if s.stt in (None, "none"):
         return None
+    if s.stt == "whisper":
+        from .backends.whisper import WhisperSTT
+
+        return WhisperSTT()
     from .backends.mock import MockSTT
 
     return MockSTT()

wsai/pipeline.py

@@ -136,6 +136,28 @@ class Pipeline:
             await self._handle(utt)
 
     # -- lifecycle --------------------------------------------------------- #
+    async def _prewarm(self) -> None:
+        """Load slow-to-start backends before the loops accept input.
+
+        Real STT/TTS backends (faster-whisper, MeloTTS) load a model into a
+        persistent worker on first use — several seconds on CPU. Warming them
+        here means the first real utterance is answered warm (~1s) instead of
+        paying the cold model load mid-conversation."""
+        warmers = []
+        for comp, name in ((self.tts, "tts"), (self.stt, "stt")):
+            warmup = getattr(comp, "warmup", None)
+            if callable(warmup):
+                warmers.append((name, warmup))
+        if not warmers:
+            return
+        for name, warmup in warmers:
+            try:
+                await warmup()
+            except Exception as exc:  # a warm failure must not abort startup
+                log.warning("prewarm %s failed: %s", name, exc)
+                if self.monitor is not None:
+                    self.monitor.log("error", f"{name} 예열 실패: {exc}")
+
     async def run(self) -> None:
         # A TaskGroup (not bare gather) so that if ONE loop raises, the others
         # are cancelled and awaited before teardown. With plain gather the
@@ -145,6 +167,7 @@ class Pipeline:
         if self.monitor is not None:
             self.monitor.set_status(running=True)
             self.monitor.log("info", "파이프라인 시작")
+        await self._prewarm()
         try:
             async with asyncio.TaskGroup() as tg:
                 tg.create_task(self._perceive())