Session events are a single unified stream carrying control-plane signals (user events, agent actions, session state) and telemetry (span data) on the same channel, rather than telemetry being a separate observability sidecar.
If the runtime event protocol is also the observability protocol, then tracing, debugging, and replay come from the same durable artifact the application already consumes to drive state — removing the need to instrument a parallel tracing pipeline and making agent execution auditable by default.
Agent runtimes should treat the event log as the primary append-only source of truth for both application state transitions and telemetry, rather than bolting observability onto a runtime after the fact.
Events form an ongoing stream of user events, agent actions, session states, and span telemetry.