coqui-tts imports a transformers 4.x symbol that 5.x removed. Unlike parler and
the OCR engines it had never been isolated locally: _CoquiBackend did a plain
'from TTS.api import TTS' and gave up when it was missing. On a pod that meant
an image with a verified, working TTS venv answered 'pip install coqui-tts' —
the venv was there and nothing knew to use it.

xtts_worker finds the venv the way the others do (explicit env var, the baked
/opt/coderai/venvs/TTS, then per-user) and drives tools/xtts_service.py in it
over stdin/stdout. XttsSubprocess wears the TTS object's shape — speakers,
tts(**kwargs), synthesizer.output_sample_rate, and the TypeError the backend
relies on to retry without speed — so synthesize() runs unchanged whether the
library is in this process or next door.

Verified inside the pushed image: the venv is found and the service answers
from it. The fall-through is unit-tested with a fake worker, and the error when
no venv exists names the places it looked.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0182DhR1eFNPQyGmDrpHbedY