Protocol-compatible GitHub Actions runner replacement, written from scratch in Rust.

Chimera is a single, fast binary that manages multiple runners concurrently. Run it as a systemd service, in a Docker container, or just in a terminal. It speaks the same registration and job execution protocol as the official runner, so it works with any existing workflow without modification.

curl -fsSL https://raw.githubusercontent.com/quinck-io/chimera/main/install.sh | sh

Or install a specific version:

curl -fsSL https://raw.githubusercontent.com/quinck-io/chimera/main/install.sh | sh -s -- v0.1.0

Prebuilt binaries are available for Linux and macOS (x86_64 and aarch64) on the releases page.

git clone https://github.com/quinck-io/chimera.git
cd chimera
cargo build --release
# binary is at target/release/chimera

Official GitHub Actions runners are slow, resource-heavy, leak memory and difficult to manage.

Chimera is designed to be a better experience for self-hosted runners, with a focus on performance, reliability and multirunner management, which are especially important for larger organizations. It also serves as a reference implementation of the GitHub Actions runner protocol, which is currently only documented through reverse engineering.

See docs/gh-protocol.md for the full spec, API and auth flows of the GitHub Actions runner protocol.

Register runners the same way you would with the official runner, then start the daemon. Runners poll for jobs concurrently — each job gets a clean workspace and can use Docker containers as needed.

chimera register --url https://github.com/org/repo --token AABBC... --name runner-0
chimera register --url https://github.com/org/repo --token DDEEF... --name runner-1
chimera start

Jobs with container: run inside Docker. Jobs without it run on the host. Services always run as containers on a shared bridge network. Logs stream live to the GitHub UI.

All state and data is stored in ~/.chimera by default.

chimera register --url <url> --token <token> --name <name> [--labels a,b] [--root ~/.chimera]
chimera unregister --name <name> [--root ~/.chimera]
chimera start [--root ~/.chimera]
chimera status [--root ~/.chimera]

register — Register a runner with GitHub. Token comes from Settings > Actions > Runners.

unregister — Remove a runner from GitHub and delete its local credentials.

start — Start all registered runners concurrently.

status — Show daemon uptime, per-runner phase (Idle/Running/Stopped), and current job info.

~/.chimera/config.toml (managed by register):

runners = ["runner-0", "runner-1"]

[daemon]
log_format = "text"           # "text" or "json" (json works well with journald)
shutdown_timeout_secs = 300

• Host and container step execution (run:, container:, services:)
• All action types: Node.js, Docker, composite
• Full ${{ }} expressions — success(), failure(), hashFiles(), contains(), format(), all contexts
• All workflow commands (set-output, set-env, add-mask, save-state, etc.)
• Step conditions, timeouts, continue-on-error, cancellation
• Per-job Docker network, port mapping, volumes, --privileged/--cap-add
• Live log streaming, job outputs, heartbeats
• Support for actions/cache/v4

Chimera-only features:

• Multi-runner concurrency with independent error isolation
• Local actions/cache server for faster caching and no external dependencies
• Automatic cleanup of old workspaces, containers and orphaned processes
• Configurable LRU cache (default 10GB)

Create the unit file:

sudo tee /etc/systemd/system/chimera.service > /dev/null <<'EOF'
[Unit]
Description=Chimera GitHub Actions Runner
After=network-online.target docker.service
Wants=network-online.target
Requires=docker.service

[Service]
Type=simple
User=chimera
ExecStart=/usr/local/bin/chimera start
Restart=on-failure
RestartSec=5
Environment=RUST_LOG=info

[Install]
WantedBy=multi-user.target
EOF

Then enable and start it:

sudo systemctl daemon-reload
sudo systemctl enable chimera
sudo systemctl start chimera

Check status and logs:

sudo systemctl status chimera
journalctl -u chimera -f

Set log_format = "json" in config.toml for structured journald output.

• GHES (GitHub Enterprise Server)
• Windows — not in scope but may work (untested)

See CONTRIBUTING.md.

MIT