I could believe a ~66% success rate on asking an agent to run a linter and make PRs addressing issues found, that sounds about right: very tightly bounded problem, a sensible solution is often offered by the tool, and verification of success is binary.

Structural changes, in which attention to the small details of a task is directly at odds with the need to consider less overt factors like cohesion and coherence, are where an agent will turn your code base into a dog's breakfast.

The vibe coded software I have for my own use only is like that. Giant hundred-line functions, poor separation of concerns, easy for a change to have unintended behaviour somewhere else. It's probably a step up from the spreadsheet I was using before it, but not by enough to justify current RAM prices.