Once ready, the environment can be attached when the session starts; it can also be attached while setup is still running, with agent access waiting until setup completes.
The operational change is to move workspace preparation ahead of the user’s task. OpenAI says pre-warming is free before attachment, and unattached environments expire after five minutes. Standard container pricing applies after attachment. This offers a bounded way to reduce setup time on a request’s critical path; the documentation does not quantify the latency reduction or establish that every workload will benefit.