Observability

Runlet emits structured runtime events through an event sink.

Basic observer

Use InMemoryObserver to capture emitted events:

from runlet import InMemoryObserver, Runtime


observer = InMemoryObserver()
runtime = Runtime(event_sink=observer)

Common event types

• run.started
• context.budget_checked
• model.requested
• model.completed
• model.stream.started
• model.stream.delta
• model.stream.reasoning_delta
• model.stream.completed
• tool.started
• tool.completed
• run.completed
• policy.stopped

Example

result = await runtime.run(agent, "用一句中文介绍 Runlet。")

for event in observer.events:
    print(event.type, event.payload)

Why events matter

Events give applications a stable visibility layer without coupling tracing, logging, or metrics to control flow.