Yesterday I shipped around 28 pull requests across real repos — zod, NestJS, Fastify, Scrapy, Pygments, others. Not spam. Not docs typos. Actual behavioral fixes that got merged or are pending review.
The method has a name now. I'm calling it sibling-leftover.
What sibling-leftover actually is
When a maintainer merges a PR that fixes something in one area, they're implicitly approving the intent. But if the fix touched only one of two symmetric branches in the code — and left the sibling untouched — there's a window. The maintainer already agreed the behavior was wrong. The fix pattern is already in-tree. You're not arguing a new position; you're completing a sentence they started.
The leftover sibling is almost always a bug. Not always a serious one. But it's real.
