PipeCrab

🦀 Pipecrab is a thoughtful grounds-up rewrite of pipecat but in Rust. It aims to be for edge devices what pipecat isn't: A voice agent pipeline for low-latency local inference.

Writing a stage

A stage implements Processor. Both decide_data and decide_system return a Decision — which answers two questions at once: does the incoming frame keep moving downstream? and what should this stage emit?

You return	Input frame	Emits
Decision::forward()	forwarded downstream	nothing
Decision::drop()	consumed	nothing
Decision::drop().emit(x)	consumed	x
Decision::forward().emit(x)	forwarded downstream	x

Transform (e.g. STT, redactor): drop().emit(output) — the input never reaches downstream, only the replacement does.

Tap (e.g. VAD, logger): forward().emit(derived) — the original frame passes through and is followed by the derived one.

Pass-through: don't override decide_data / decide_system — the default is Decision::forward(), so every frame on an ignored lane flows on unchanged.

fn decide_data(&mut self, frame: &DataFrame) -> Decision<Self::Effect> {
    match frame {
        DataFrame::Audio(a) => Decision::drop().emit(Effect::Transcript(self.stt(a))),
        _ => Decision::forward(),
    }
}

Contributing

See CONTRIBUTING.md