Event Bus Guide

core/event is a subject-routed publish/subscribe bus. The in-process implementation is MemoryBus; remote implementations may implement the same Bus interface.

Core types

Type	Role
event.Bus	Publish, Subscribe, Close
event.Envelope	id, subject, time, headers, payload, trace IDs
event.Subject	dot-delimited routing key
event.Pattern	* matches one segment; > matches one or more trailing

Subscribe and publish

bus := event.NewMemoryBus()

sub, err := bus.Subscribe(ctx, "graph.run.*.start")
if err != nil {
    return err
}
defer sub.Close()

env, _ := event.NewEnvelope(ctx, "graph.run.r1.start", payload)
if err := bus.Publish(ctx, env); err != nil {
    return err
}

MemoryBus has a subject-route cache and supports DropNewest, DropOldest, Block, and Sample backpressure. Buffer size is capped.

Deployment resource

resources:
  events:
    kind: event.Bus
    impl: memory
    settings:
      route_cache_size: 1024  # optional: positive caps the subject route cache, zero disables it

The runtime host exposes the bus through agent.EventBusProvider. Runtime-level consumers can also subscribe through Runtime.Attach without resolving the resource themselves; the prompt lifecycle events are documented in prompt.md. Runtime agent lifecycle events (runtime.agent.<id>.registered / .removed, subscribe with PatternAgentLifecycle()) live in a separate namespace and are published on successful dynamic registration/removal, and generation reloads publish runtime.rebuild.started / .completed / .failed (PatternRuntimeRebuild()) — see runtime.md.