Those diffs are rare corner cases where the input is invalid Javascript. Prettier's parser is permissive and emits beautifully indented nonsense (which is arguably a bug in prettier). For example, in the original program there is a "private public" but the prettier output in red only says "private". Biome decided that in these cases it should not touch the indentation at all. The output is indented exactly the same as the input. The concern is that if you reindent something that you don't understand, it might break it. https://github.com/biomejs/biome/issues/739