One slow browser request becomes a runner command, three model calls, two tools, and a later replay. Without relationships, the trace looks like unrelated latency.
Create: this request begins new work
Kestrel trace context can start new work, continue an incoming relationship, replay recorded work, or fork a related attempt. The directive makes that choice explicit instead of guessing from whichever header happened to be present.
Request, correlation, Session, Run, Turn, tool, provider, and effect identities can become span attributes or links. They should not be collapsed into one trace ID: each answers a different operational question.
Continue: the runner belongs to the request
Continuing carries the incoming relationship across the Agent boundary. Child spans can cover runner transport, model invocations, tools, and adapters without inventing a new unrelated root.
Replay: inspect old evidence in a new attempt
Replay links to the original evidence while remaining a distinct attempt. It does not overwrite the old timeline or pretend the same Run happened twice.
Fork: related work takes another path
A fork preserves relationship without claiming direct continuation. That distinction is useful when a recovery or investigation shares origin but owns a different execution lifecycle.
Export the relationships
The observability package supplies trace context parsing and resolution plus tracers, spans, processors, and exporters. An application can wrap Agent calls, attach the resolved context, and export through console, in-memory inspection, or an OpenTelemetry bridge according to deployment needs.
Spans remain telemetry. They may be sampled, delayed, dropped, or stored under a different retention policy. They help explain performance and relationships, but they do not replace persisted terminal results, effect receipts, approvals, task updates, or provider reasoning records.
Likewise, a successful span means the instrumented operation returned according to its span contract. It does not independently prove that a real-world effect committed or project work was accepted.
Package contracts live in Observability reference; Add observability carries them into an application.