You ask an agent to prepare a release. It reaches an approval wait, you close the application, and another operator returns an hour later. The first resume attempt fails because the runner restarted. A recovery action creates a new attempt, which completes.
How much work was that?
The Session continued
The Session is the durable line of conversation and runtime continuity. Messages, waits, resumes, task-backed state, and successive attempts stay attached to its sessionId. Closing a client does not end it.
In Kestrel One, a Thread is the product's shared conversation object. It can be linked to runtime sessions, but it is not another spelling of Session: Thread ownership, membership, project context, and sharing belong to the product boundary.
The Turn advanced the conversation
A Turn begins with new user intent or a response to a pending interaction and advances the conversation toward an outcome. The original request to prepare the release is a Turn. The exact approval response continues that conversational work rather than pretending the prior request never happened.
A Turn can involve several model and tool steps inside the agent loop. It is not one model invocation.
The Run made one attempt
A Run is one execution attempt with its own lifecycle, events, cancellation target, and terminal result. The attempt that reached the wait is one Run. A retry or registered recovery may create another Run while preserving the Session and its causal history.
This distinction keeps diagnostics honest. “The Session succeeded” can hide a failed first attempt. “The Run failed” does not mean the continuing conversation was deleted.
The stream only observed
An event stream is a live view of a Run. Disconnecting it can cancel the Run when the request contract says so, or merely detach from durable work. Reattaching does not create a new Run. A subscription can observe activity across a wider filtered scope and is not itself a Run either.
These identities let Kestrel answer precise questions: Which attempt spent the budget? Which wait is pending? Which terminal result is authoritative? Which conversation should the next message continue?
See Session state and versioned memory for continuing state and Streaming, progress, and reasoning for the live view of an attempt.