Terrifying.

The lead developer didn't like to bother with formatting code, so I wrote a tool called makenice to format his nasty spaghetti gibberish into something with good indents and layout to make it easier for us normal people to parse.

He was furious, literally spun in circles about it right in the office in front of everyone, so I wrote makenasty to format code into the way he appeared to like.

I only shared makenasty/nice with a couple of the team, who loved it, as it allowed easy conversion between something readable and something the team lead like.

He never knew about makenasty.

Why bother formatting 25m lines of slop, and why is AI wasting tokens on making code look human-readable anyway?

I had to introduce a formatter in a few sizeable codebases in the past (few 100k to few million LOC), and I always did it incrementally via a script that reformatted all files that are not touched in any open PR. The initial run reformatted 95% of all files. Then I ran the script every day for ~two weeks and got up to 99.5% of all files and then manually each time one of the remaining ~dozen PRs that were WIP for longer were merged.