motrix-rl-builtin owns MotrixLab's built-in reinforcement-learning integrations, currently FastSAC. Its Python namespace
is motrix_rl_builtin; FastSAC configuration and implementation live under motrix_rl_builtin.fastsac.
The plugin owns FastSAC models, replay buffers, environment wrappers, synchronous/asynchronous trainers and policy-export
implementation. The method remains motrix.fastsac, with the Torch training backend; algo.asynchronous selects the
execution topology rather than a separate method.
It depends only on motrix-rl for control-plane services and provider/trainer contracts, plus its
Torch runtime dependencies. It registers via the motrix_rl.frameworks entry-point group:
builtin = "motrix_rl_builtin.plugin:register". Consumers query motrix_rl.frameworks rather than importing plugin
internals to trigger registration.