Hooks

A hook is a callback that runs at a specific point as a request flows through the router. BitRouter processes every request as an ordered pipeline of stages; hooks attach to those stages, and depending on the stage a hook can allow, deny, mutate, or observe the request. Plugins bundle hooks and install them.

The language-model pipeline

The main language_model pipeline runs five kinds of hook, in order:

1. PreRequest — auth, policy, rate-limit, balance, and guardrail checks. Each returns allow or deny; the first deny stops the pipeline and maps to an HTTP status.
2. Route — resolve or rewrite the ordered chain of routing targets for the request.
3. Execution — observe each attempt and control fallback on success or failure.
4. Stream — intercept streamed response parts to rewrite, drop, or abort them.
5. Observe — read-only observation at every stage boundary; it never influences the request, and a failure here can't break it.

Settlement — metering, charging, and receipts — runs against an immutable context once the request is done.

For the trait signatures and a worked example, see Build a plugin.