sutra-bindings-speech

Local Indic speech bindings: whisper.cpp-class STT and local TTS behind SpeechInterface.

Indic TTS voice coverage

Authoritative model card: fixtures/tts/tts-voices.model-card.json
Loaded voices (runtime): fixtures/tts/voices.json

loadLocalTts() / loadTtsVoiceModelCard() declare supportedLanguages only from this coverage — never aspirational. Hindi + English + ≥1 additional Indic (Tamil).

| Language (BCP-47) | Voice id | Role | Script | |-------------------|----------|------|--------| | hi-IN | indic-hi-f1 | primary-indic | Devanagari | | en-IN | indic-en-f1 | fallback-english | Latin | | ta-IN | indic-ta-f1 | additional-indic | Tamil |

Programmatic table: languageVoiceCoverageTable() (must stay in lockstep with the model card and README).

TTS language fallback (CK-05.2)

Declared fallbackLanguage: en-IN.

| Request | Behavior | |---------|----------| | Language in supportedLanguages | Synthesize with that voice; telemetry outcome: "ok" | | Unsupported BCP-47 | Route to declared fallbackLanguage (en-IN); telemetry outcome: "fallback" + usedFallback: true — never throw, never silent English substitution without that signal | | Empty / whitespace text | Typed LocalTtsError (validation) before synthesis starts | | Mixed-script (Devanagari + Latin) | Synthesizes without crash; language selection still follows requested BCP-47 + fallback (no mid-utterance auto-switch) |

Locality: on-device. Telemetry event bindings_speech.tts carries subjectId / deviceId / outcome — never raw synthesis text.

Quick commands

pnpm --filter sutra-bindings-speech test
pnpm --filter sutra-bindings-speech run certify:speech
pnpm --filter sutra-bindings-speech run prove:speech-cert

Speech CI certification (CK-05 STT+TTS + Indic fixtures): see certification/README.md.