Reactor Runtime turns an inference pipeline into a real-time, interactive media and data stream. You write load() and run(); the runtime handles the session lifecycle, the WebRTC media transport, and the wire protocol that connects clients to your model. Viewers watch frames as they are generated and change what the model is doing mid-stream, with no restart and no re-queue.
Highlights
- 📡 Real-time streaming. Frames reach clients over WebRTC as your model produces them, not after a whole video is done.
emit()paces your loop to the rate clients play at, so a model needs no rate limiter of its own. - 🎮 Live interaction. Clients send commands mid-generation: change a prompt, move a camera, adjust a parameter. The next frame reflects it.
- 🔌 No transport code. You never import a WebRTC library, manage a WebSocket, or encode video. The runtime ships its own media engine as a wheel, so a plain Python container is all a model needs.
- ✅ Typed, validated commands. Declare the commands your model accepts with standard Python types and constraints. The runtime validates every payload before your handler runs and compiles the surface into an OpenAPI schema that drives typed client SDKs.
- 🔎 Traceable logs.
get_logger()writes structured records — readablekey=valuein a terminal, JSON for a log pipeline. Every record a session writes carries that session's id automatically, so one filter recovers everything a single run logged. - 📦 One container, anywhere. The
reactorCLI scaffolds a workspace, builds a small image, and runs it locally. The same image deploys to Reactor's GPU cloud unchanged.
How it works
A model is a ReactorModel subclass in model.py. Declare the media it sends, load your weights once, and write the loop that receives or produces frames, data, and more:
from pathlib import Path
from reactor_runtime import InputField, Output, ReactorModel, Video, event
class MyOutput(Output):
main_video: Video
class MyModel(ReactorModel):
fps = 24
def load(self, config_path: Path | None) -> None:
self.pipe = load_my_pipeline()
self.prompt = "a sunny meadow"
@event(name="set_prompt", description="Scene the model renders")
async def set_prompt(
self, prompt: str = InputField(default="a sunny meadow", moderate=True)
) -> None:
self.prompt = prompt
async def run(self) -> None:
while True:
await self.connected.wait()
while self.connected.is_set():
frame = self.pipe.forward(prompt=self.prompt)
await self.emit(MyOutput(main_video=frame))
That is a complete model. run() produces frames for as long as someone is watching, and any client can send set_prompt at any time to change what the next frame renders.
Scaffold, build, and run it with the CLI:
reactor init my-model
cd my-model
reactor run
reactor run builds a container with the runtime inside and serves WebRTC signaling on port 8080. Point a browser at it with the JS SDK, or connect from the Reactor Sandbox and watch frames stream immediately.
Log from the same import, passing context as keyword arguments:
from reactor_runtime import get_logger
logger = get_logger(__name__)
logger.info("scene changed", prompt=self.prompt)
Records render as key=value text by default, or as one JSON object per line under REACTOR_LOG_FORMAT=json. While a session is live, its id is stamped on every record, so tracing one run's logs never requires threading an id through your call sites. Every record also carries the lifecycle phase it was written in, at both granularities: state, the session state machine's word, and runtime_state, the coarse word the health endpoint serves — so the logs of one phase — loading weights, a live session, teardown — are filterable by whichever vocabulary you are reading off another surface. The stamp is applied where records are written rather than where they are made, so a plain logging.getLogger(__name__) and the libraries your model imports are covered too.
Install
Everything runs through the reactor CLI. There is nothing to install on your host but the CLI and Docker; the runtime ships inside the image the CLI builds for your workspace.
brew install reactor-team/tools/reactor-cli
Not on macOS, or pinning a release in CI? See Install the CLI.
Learn more
- Quickstart: from zero to a streaming model in 2 minutes
- Model anatomy: every piece of a Reactor model, line by line
- The run loop: emitting frames, batches, and frame rates
Development
This repository holds the runtime package itself: the authoring interface, the session runner, the media transport, and the wire protocol. To work on it, use mise, which pins the toolchain and forwards every task through a thin make shim:
mise run install # install deps, generate wire bindings, and git hooks
mise run lint # ruff check, ruff format --check, and mise.lock drift
mise run format # apply ruff formatting
mise run typecheck # ty (strict)
mise run test # unit tests on the floor Python
mise run test-matrix # unit tests on every supported Python
License
Licensed under the Apache License, Version 2.0.
1 maintainer
Release files for reactor-runtime 3.3.0
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