Turn
One user message and everything the agent does before returning control to the user.
Illustrative conversation
- Why did one reply trigger four model requests?
- They were separate requests inside the same turn while the agent inspected files and verified its answer.
Definition
A turn is the user-visible unit of work that begins with new input and ends when the agent returns control, pauses, fails, or transfers the workflow. Inside one turn, a runner may make several model requests, execute tools, process their results, and even hand off to another agent. This is a user-facing definition. Some runtimes use “turn” for each model invocation: OpenAI Agents SDK max_turns uses that narrower meaning. Check the runtime before interpreting a turn limit.
Reviewed