Function drive_loop 

pub async fn drive_loop(
    ctx: &mut RunCtx,
    agent: &Agent,
    input: &Value,
) -> Result<LoopOutcome, RuntimeError>

Runs the built-in agent loop over an already-begun run, returning the final output (a LoopOutcome::Completed) or a park, but not recording the terminal RunCompleted.

The second half of [drive], made public so an external driver can run an agent loop inside a run it opened itself. The graph engine uses exactly this: it opens the log with GraphRunStarted, records NodeEntered, calls drive_loop (whose model and tool events land in the same log), records NodeExited, and moves to the next node, recording the single terminal RunCompleted only after its last node. Leaving the terminal to the caller is the whole reason the completion moved out of the loop and into [drive].

input is the already-begun run’s input (what [begin] returned).

Errors

Whatever the RunCtx operations surface: RuntimeError::Replay on divergence, RuntimeError::Model on a live provider failure, RuntimeError::Store on a persistence failure.