RunOrigin

Where a child thread came from (design 4.41): the thread whose run started it (parent), the tool call of that run that started it (call, the call's IdempotencyKey), the agent it runs (agent), when it was first admitted (startedAt, by the runtime's clock: GraphRuntime.startChild stamps it, whatever the caller passed), and how deep it is: 1 for a child of a top-level thread, one more for each level below.

A thread is a child thread exactly when its latest checkpoint records an origin (Checkpoint.origin), never because of its id's shape. The origin is written with the child's first checkpoint and copied onto every later one, as the tenant is. A child thread is driven only through its parent's run: start, recover, resume, fork, updateState and deleteThread on it are refused with GraphError.ChildThread.