A user on mlx-audio with the language picker on "Auto" got:
400: mlx-audio's Kokoro model doesn't support language='Persian'.
… Pick one of those, leave language as 'Auto', or switch to a
multilingual engine …
They had left it on Auto. The UI omits `language` entirely while its
picker reads "Auto" (useProfiles.js only appends a non-Auto value), and
#533 fills that gap from the selected voice profile. So Auto is exactly
how 'Persian' got there: the remedy the message leads with is the state
the user was already in, and nothing points at the profile that actually
supplied the language. Three generate attempts in their action log, a
detour through Settings, then the report.
Provenance was the missing fact, and only the request scope has it — the
engine adapters are handed a language with no idea who chose it. So
_resolve_profile_conditioning now reports whether it filled the language,
and /generate uses that to answer a refused profile language by naming
the profile and the remedies that exist: change the profile's language,
pick a supported one explicitly, or switch engine.
An explicitly requested language is untouched — the user really did pick
it, so blaming the profile would be a lie — and #533 still drives
generation whenever the engine can speak the profile's language.
Recognising the refusal needed one more thing: Kokoro's wording
("doesn't support language=…") matched none of #1257's signatures, so
the engine that issue was written for was the one engine its rewrite
never fired for. That wording is now recognised, but kept out of #1257's
rewrite path — it already names its engine and its languages, and
re-wrapping it only nests "Engine's own message:" twice.
No per-model language map: #1257 weighed that and chose engine-naming
over "a brittle map that goes stale on each engine update". This follows
the same principle — say where the language came from, don't enumerate.
docs/engines/mlx-audio.md repeated the same "leave language on Auto"
advice and is corrected here.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
