Make homepage cards and live sessions produce sound when the server is
configured for StepFun TTS, instead of silently failing (the prebaked
Xiaomi voice was useless on a StepFun server, and wasted ~220KB/beat in
Fast Origin Transfer).
Three coordinated changes:
1. CharacterDesigner now picks a StepFun preset voice id directly from the
32-entry catalog in the SAME LLM call that designs the character — zero
extra latency, LLM-grade match quality. The Xiaomi prompt path is
byte-identical to history (verified programmatically) so cache hit rate
and voice quality are preserved. pickStepfunVoiceId (keyword scorer)
remains the fallback for orphan speakers / invalid LLM picks.
2. The 32-preset catalog moves to lib/tts-client/stepfun-voices.json as the
single source of truth, shared by the scorer, the CharacterDesigner
prompt, /api/tts-provider, and the offline enrich script.
3. A new GET /api/tts-provider endpoint lets the client probe the server's
TTS provider at /play mount. fetchBeatAudio then shapes its request body:
on a StepFun server it sends the lightweight stepfunVoiceId /
voiceDescription and omits the ~220KB Xiaomi reference audio (FOT saving
~13MB per protagonist per session on prebaked cards). requestBeatAudio
re-provisions on a provider mismatch before synth, so audio never goes
silent on a cross-provider replay or mid-session provider flip.
New type fields are all optional and backward-compatible: Character.stepfunVoiceId,
BeatAudioRequest.voiceDescription/characterName/stepfunVoiceId, voice made
optional. AGENTS.md updated for the new route, type fields, dependency map,
and StepFun voice-selection flow.
yuanzonghao