A stacked pull request is matched to its commits by a Change-Id trailer, and prek owns the commit-msg hook, so nothing here wrote one. Every stack has needed `--add-change-ids`, which rewrites the range — and a pull opened without one cannot be rewritten afterwards at all: the record names a sha, the rewrite moves it, and reconciling would delete the record. That cost a decision renumber on two open stacks today. Written by `atgc repo configure --hook-config`. The script does nothing to a commit that already carries an id. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Change-Id: I3b699a0c7b01f61fc2235ec4cf7c6e155a0eeb4f