I don't use mypy so I can't comment on it but at least from what I have seen pyright is deterministic in it's output and get output json.

Regarding the ~80k errors. Yeah, nothing to do here besides slowly grinding away and adding type annotations and fixes until it's resolved.

For the code example pyright gives some hint towards variance but yes it can be confusing.

https://pyright-play.net/?pyrightVersion=1.1.403&code=GYJw9g...