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github-actions[bot] edited this page Sep 15, 2026 · 1 revision

Text-to-speech (TTS)

AgentBridge speaks with a local neural TTS engine. Kokoro is the engine: it works on every machine, immediately, with nothing to install. The engine catalog is designed to grow — a future engine registers in TtsEngineSupport (AIOrchestrator) and is then selectable through the same /ttsengine command and appsettings preference.

Engines at a glance

Engine Works out of the box Model Speed When to use
Kokoro (default) Yes — everywhere (Windows, Linux, macOS; any CPU; no drivers, no accounts) ~325 MB, included in the archive realtime on a normal CPU The default — the voice for the chat, the phone and the podcast tool

The engine is selected through the same preference every time:

  • /ttsengine in the terminal UI (menu Settings → TTS Engine) — shows the known engines and sets the engine.
  • appsettings.json → "Tts": { "Engine": "kokoro" } (the /ttsengine command persists here). A value outside the catalog falls back to Kokoro and logs why, so a stale setting never breaks the TTS.

The catalog (TtsEngineSupport in Graphene.AIOrchestrator) currently registers Kokoro only. Future engines add their name + availability gate there and inherit the selection path (host config, /ttsengine, PODCAST_TTS_ENGINE for the plugins) without host changes.

Kokoro — nothing to install

  • The voices and the model (kokoro.onnx) are shipped inside every archive — no download, no drivers, no accounts.
  • Phonemization is fully managed (no espeak binaries), so it behaves identically on Windows, Linux and macOS, x64 and ARM64.
  • The terminal, the SIP phone bridge and the podcast tool all use this engine in-process.
  • GPU acceleration (optional): when the CUDA Toolkit 12.x + cuDNN 9.x are installed, the engine uses the CUDA execution provider automatically (the archive ships the provider DLL). Without CUDA it runs on the CPU — realtime anyway on a normal machine. No manual setup; the engine probes the standard install directories and sets the runtime PATH itself.

Platform prerequisites

Requirement Needed for How to install (official)
nothing Kokoro (CPU) —
NVIDIA driver Kokoro GPU (CUDA, optional) https://www.nvidia.com/drivers
CUDA Toolkit 12.x + cuDNN 9.x Kokoro GPU (CUDA, optional) https://developer.nvidia.com/cuda-downloads · https://developer.nvidia.com/cudnn

Kokoro needs no espeak, no native phonemizer, no audio stack: it ships everything in managed code and works on Windows, Linux and macOS out of the box. The install.ps1 one-liner detects a CUDA-capable GPU and asks whether to install the CUDA Toolkit + cuDNN silently; answering no keeps everything working on the CPU, and the GPU is picked up automatically at runtime if the toolkit is installed later.

Troubleshooting

  • "kokoro.onnx not found" — the model file is missing next to the executable; reinstall from the latest release archive (it is included).
  • A podcast records with a wrong voice — the tool resolves the voice from the episode language; check the configured language (a missing voice falls back to the first loaded one).

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