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Lehar is provider-pluggable. You pick the LLM, STT (speech-to-text), and TTS (text-to-speech) by name — on the agent’s config, or overridden per session. Cloud, local, and self-hosted providers are interchangeable.

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Capabilities

Set them in config:

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Realtime (audio-to-audio) models

Some Gemini models (Live / native-audio) do integrated voice input and output — there is no separate STT or TTS stage. When a realtime model is selected, STT/TTS settings are ignored, and Lehar skips estimated STT/TTS billing for that session.

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Voices

  • Sarvam — pick a Bulbul model version with sarvam_tts_model (bulbul:v3, the default, or bulbul:v2), then a speaker. Speakers are specific to the model version and the two sets are disjoint — a v2 speaker on v3 is rejected at save time. Speaking pace is configurable (0.3–3.0), and tts_language (the spoken output language) is separate from the STT input language.
  • Murf — voice is a Murf {locale}-{name} id (e.g. en-IN-anisha), with an optional murf_tts_style (Conversational, Promo, Narration) and signed murf_tts_speed / murf_tts_pitch in −50…50. Real-time streaming only; there is no model selector.
  • ElevenLabs — voice is an ElevenLabs voice id and elevenlabs_tts_model selects the model: eleven_flash_v2_5 (default, lowest latency), eleven_turbo_v2_5, eleven_multilingual_v2, or eleven_v3. Flash and Turbo bill at half the per-character rate of the other two. Optional elevenlabs_tts_language plus voice settings elevenlabs_tts_stability, elevenlabs_tts_similarity_boost and elevenlabs_tts_style in 0…1, elevenlabs_tts_speed in 0.8…1.2, and elevenlabs_tts_use_speaker_boost. Leave a setting unset to use the voice’s own.
  • Edge — voices use Edge TTS voice names (e.g. en-IN-NeerjaNeural).
  • Kokoro (local) — English and Hindi voices; the pipeline language is derived from the voice name, so use only the voices the catalog lists.
  • Qwen3 (self-hosted) — a model size (0.6b fast / 1.7b quality) plus a voice, selected with the voice field. Lehar hosts its own fine-tuned voices manish and shail (Hinglish), plus reference-clip clones ojas, shruti, happy and sad. The language selector has no Hindi entry — use a Hinglish voice instead.
  • LiveKit — voices use LiveKit TTS voice IDs.

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Pronunciation

Attach a pronunciation dictionary to an agent (via pronunciation_dictionary_id) to control how it says specific words — brand names, places, acronyms. The rules are applied as a text substitution just before speech, so they behave identically across every TTS provider. GET /catalog/models advertises this with pronunciation_dictionary_supported, and names the providers that additionally accept IPA entries in pronunciation_dictionary_ipa_providers.

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Sarvam LLM reasoning

Sarvam LLMs reason by default, which costs voice latency and bills reasoning tokens as completion tokens. Set sarvam_llm_reasoning_effort to low (recommended for voice), medium, high, or off to disable chain-of-thought entirely. Leave it unset to inherit the deployment’s default.

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Discover what’s available

GET /catalog/models (scope sessions:read) returns the live catalog that powers the dashboard’s agent editor: LLM/STT/TTS providers, their models and defaults, Gemini voices, Edge voices, and Sarvam speakers. Read it at runtime rather than hard-coding lists.
Provider selection is one direction only: it flows to the agent worker as session metadata at dispatch time. If your deployment restricts which providers are configured, unavailable ones simply won’t appear in the catalog.

Agents

Set defaults on the agent.

Sessions

Override per call.