onFinishRequiresThreadState

Returns true when onFinish declares at least one parameter and therefore needs the server-fetched thread head. A zero-arity onFinish is treated as side-effect-only and does not trigger a post-stream getHistory when branching history is not enabled.

Note: functions with only default parameters report .length === 0 in JavaScript; if you need the thread state, declare at least one non-default parameter (e.g. (state) or (_state, run)).