`extract_changed_files` parses `diff --git a/<old> b/<new>` headers. A host `diff.mnemonicprefix=true` or `diff.noprefix=true` rewrote them (`c/ w/`, or none), so every tracked change vanished from `changed_files` and the two evidence git-diff tests failed on such hosts. Both capture paths now pass `--src-prefix=a/ --dst-prefix=b/`, which override both config keys. Regression test sets each key in the temp repo. Claude-Session: https://claude.ai/code/session_01RUqV8HVGXcAETyYbZ2tPQ4