Engines

An engine is a Python package that the server installs into a virtualenv of its own, through the API, the web page or pnpm wizard install. One engine's dependencies cannot break another's, and a crash takes down that engine's worker rather than the server.

Which one

• Start with Kokoro. It runs on the CPU with no torch, its weights are about 200 MB, and it speaks faster than realtime on a laptop. It performs no cues, and makes new voices by blending its own rather than by cloning.
• With a GPU, Chatterbox. It clones a voice from a few seconds of audio. Its turbo and nano builds perform all eight cues; its original and multilingual builds take dials instead. Which you get depends on the build that is loaded, and the capability document says which.
• For audio that starts before the line is finished, Orpheus. It streams while it generates, and performs seven of the eight cues. On Linux it runs the full build through vLLM on an NVIDIA card; elsewhere the q8 and q4 builds run through llama.cpp.
• For two people talking, Dia. It speaks a two-speaker dialogue in one take, performs all eight cues, and clones from a clip and the words spoken in it. It wants a real GPU: on a Mac it runs at about a tenth of realtime.
• Tone makes a sine wave. It exists to prove the protocol in CI, and it is the fixture the conformance suite compares a real engine against.

Licences

Every engine carries two licences, one for its code and one for its weights, and the catalog shows both before anything is installed. An engine whose weights may not be used commercially installs only once that licence is accepted by name. The core is MIT; each engine is a separate package under its own licences, so an engine with restrictive weights can sit in the catalog without touching the core.

Adding one

An engine is one Python class. See adding an engine.