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NAPI bridge

Rules for rivetkit-typescript/packages/rivetkit-napi/. The bridge is pure plumbing — all load-bearing logic belongs in rivetkit-core. These notes capture current conventions and known foot-guns; they are not design principles. For the layer-boundary rule itself, see the root CLAUDE.md.

Package boundaries

  • The N-API addon lives at @rivetkit/rivetkit-napi in rivetkit-typescript/packages/rivetkit-napi. Keep Docker build targets, publish metadata, examples, and workspace package references in sync when renaming or moving it.
  • TypeScript actor vars are JS-runtime-only in registry/native.ts. Do not reintroduce ActorVars in rivetkit-core or add ActorContext.vars / setVars to NAPI.

Callback registry layout

  • Keep the receive-loop adapter callback registry centralized in rivetkit-typescript/packages/rivetkit-napi/src/actor_factory.rs. Extend its TSF slots, payload builders, and bridge error helpers there instead of scattering ad hoc JS conversion logic across new dispatch code.
  • Keep rivetkit-typescript/packages/rivetkit-napi/src/napi_actor_events.rs as the receive-loop execution boundary. actor_factory.rs stays focused on TSF binding setup and bridge helpers, not event-loop control flow.

Actor context wrapping

  • N-API actor-runtime wrappers expose ActorContext sub-objects as first-class classes, keep raw payloads as Buffer, and wrap queue messages as classes so completable receives can call complete() back into Rust.

ThreadsafeFunction conventions

  • NAPI callback bridges pass a single request object through ThreadsafeFunction. Promise results that cross back into Rust deserialize into #[napi(object)] structs instead of JsObject so the callback future stays Send.
  • N-API ThreadsafeFunction callbacks using ErrorStrategy::CalleeHandled follow Node's error-first JS signature. Internal wrappers must accept (err, payload) and rethrow non-null errors explicitly.
  • NAPI websocket async handlers hold one WebSocketCallbackRegion token per promise-returning handler so concurrent handlers cannot release each other's sleep guard.

Payload + error conventions

  • #[napi(object)] bridge payloads stay plain-data only. If TypeScript needs to cancel native work, use primitives or JS-side polling instead of trying to pass a #[napi] class instance through an object field.
  • N-API structured errors cross the JS<->Rust boundary by prefix-encoding { group, code, message, metadata } into napi::Error.reason, then normalizing that prefix back into a RivetError on the other side.
  • N-API bridge debug logs use stable kind plus compact payload summaries, never raw buffers or full request bodies.

Receive-loop state lifecycle

  • ActorContextShared instances are cached by actor_id. Every fresh run_adapter_loop must call reset_runtime_shared_state() before reattaching abort/run/task hooks or sleep→wake cycles inherit stale end_reason / lifecycle flags and drop post-wake events.
  • Receive-loop SerializeState handling stays inline in napi_actor_events.rs, reuses the shared state_deltas_from_payload(...) converter from actor_context.rs, and only cancels the adapter abort token on Destroy or final adapter teardown, not on Sleep.
  • Receive-loop NAPI optional callbacks preserve the TypeScript runtime defaults: missing onBeforeSubscribe allows the subscription, missing workflow callbacks reply None, and missing connection lifecycle hooks still accept the connection while leaving the existing empty conn state untouched.

Runtime-state reference cleanup

  • ActorContextShared::runtime_state stores a N-API Ref<()> for the JS-only actor runtime state bag. Ref::unref(env) and reference deletion require an Env, but reset_runtime_state() runs from receive-loop worker paths and Drop for ActorContextShared may run without an active JS callback frame.
  • The current mem::forget fallback in actor_context.rs keeps debug and release behavior aligned when no Env is available, but it leaks one JS object reference per actor wake cycle that created runtime state.
  • The intended fix is to create an actor-shared cleanup ThreadsafeFunction the first time runtime_state(env) has an Env. Stale Ref<()> values should be wrapped in a payload whose Drop forgets the reference only if it was never successfully unreffed, then queued to that TSF from reset_runtime_state() and Drop.
  • The TSF callback must run on the JS thread, call ref.unref(ctx.env), and avoid invoking user callbacks. The TSF itself should be unreffed from the event loop so it does not keep Node alive.
  • Shutdown is the hard edge: if the TSF is closing or Node supplies a null Env during addon teardown, the payload must fall back to the existing bounded process-lifetime leak instead of dropping a live Ref<()> and tripping napi-rs debug assertions.
  • Before replacing the fallback, add a NAPI integration test that creates runtime state across many actor wake/destroy cycles, waits for the cleanup TSF to drain, and verifies native reference counts return to zero.

Cancellation bridging

  • For non-idempotent native waits like queue.enqueueAndWait(), bridge JS AbortSignal through a standalone native CancellationToken. Timeout-slicing is only safe for receive-style polling calls like waitForNames().
  • Native queue receive waits observe the actor abort token. enqueue_and_wait completion waits ignore actor abort and rely on the tracked user task for shutdown cancellation.
  • Core queue receive waits need the ActorContext-owned abort CancellationToken, cancelled from mark_destroy_requested(). External JS cancel tokens alone will not make c.queue.next() abort during destroy.

TypeScript-side bridge behavior

  • In rivetkit-typescript/packages/rivetkit/src/registry/native.ts, late registerTask(...) calls during sleep/finalize teardown can legitimately hit actor task registration is closed / not configured. Swallow only that specific bridge error so workflow cleanup does not crash the runtime.
  • Bare-workflow no_envoys failures should be investigated as possible runtime crashes before being chased as engine scheduling misses. Check actor stderr for late registerTask(...) / adapter panics first.
  • Native actor runner settings in rivetkit-typescript/packages/rivetkit/src/registry/native.ts come from definition.config.options, not top-level actor config fields.