Function hook_rewrites_and_request_patch 

pub async fn hook_rewrites_and_request_patch<M, F>(
    model: M,
    configure: F,
) -> Result<ScenarioReport, ScenarioError>
where
    M: CompletionModel + 'static,
    F: FnOnce(AgentBuilder<M, NoToolConfig>) -> AgentBuilder<M, NoToolConfig>,

Available on crate feature test-utils only.

Exercises chained argument/result rewrites and a first-turn-only request patch. Completion proves tool_choice=Required did not leak to turn two.