ActorTask dispatch

Routing for actor lifecycle and user-facing work inside rivetkit-core. Captures the current ActorTask + DispatchCommand wiring — expect this to evolve as the ActorTask migration completes.

Migration status

• RegistryDispatcher stores per-actor ActorTaskHandles, but startup still runs through ActorLifecycle::startup before LifecycleCommand::Start. Later migration stories own moving startup fully inside ActorTask.
• ActorContext::restart_run_handler() enqueues LifecycleEvent::RestartRunHandler once ActorTask is configured. Only pre-task startup uses the legacy fallback.

Dispatch commands

• DispatchCommand::Action — spawns a UserTaskKind::Action child in ActorTask.children. Reply flows from that child task. Action children must remain concurrent; do not reintroduce a per-actor action lock because unblock/finish actions need to run while long-running actions await.
• DispatchCommand::Http — spawns a UserTaskKind::Http child in ActorTask.children. Reply flows from that child task.
• DispatchCommand::OpenWebSocket — spawns a UserTaskKind::WebSocketLifetime child. Message/close callbacks stay inline under the WebSocket callback guard.

Run task

• run is spawned in a detached panic-catching task during startup.
• Tracked via the ActorTask run handle; sleep shutdown waits for it before finalize.

Side tasks

• Actor-scoped side tasks from ActorContext run through WorkRegistry.shutdown_tasks so sleep/destroy teardown can drain or abort them. Store explicit JoinHandles only for timers/tasks with their own cancellation slot.

Engine process supervision

• Engine subprocess supervision lives in rivetkit-core/src/engine_process.rs. registry.rs calls EngineProcessManager only from serve / startup / shutdown plumbing.

Metrics

• Actor runtime Prometheus metrics flow through the shared ActorContext ActorMetrics. Use UserTaskKind / StateMutationReason metric labels instead of string literals at call sites.

Test hooks

• Process-global ActorTask test hooks (install_shutdown_cleanup_hook, lifecycle-event / reply hooks) must be actor-scoped and serialized in tests or parallel cargo test runs will cross-wire unrelated actors.