Small caution from using agents here: the useful chart is the one generated from code, tests, or traces, not the one the model draws from its own explanation.

I've had models produce very reasonable Mermaid diagrams that matched the intended design but not the actual program. It felt helpful until I realized I was reviewing the plan twice and the implementation zero times.

For PRs I'd rather render the diagram from the executable state machine itself — at least then drift in the chart means drift in behavior, and you can't review one without the other.