# The U2 bug-hunt panel was not ceremony

_2026-09-22 · booth_

**The U2 bug-hunt panel landed and it was not ceremony —
`v0.2.2`.** Nine adopted findings across four arms; eight were real against
live code and one was already fixed. The headline was **4/4 convergent from
four different angles**: `_Locked.__exit__` unlinked `.marks.lock` on the no-op
path, and `flock` binds to an INODE — so a writer blocked on the old inode
proceeds while the next writer creates a fresh lock file and takes it at once.
Two processes then run the read-modify-write concurrently and the later
`os.replace` drops a mark, with both of them obeying the protocol. **The
cleanup existed to protect the booth's TTL and it was failing at that too**:
creating and removing a directory entry bumps the DIRECTORY's mtime, which is
what `_newest_mtime` actually seeds from, so a no-op reset the clock it was
written to leave alone. Same code region, two defects, one fix — never unlink
the lock, exempt `.<name>.lock` dotfiles from `_newest_mtime`, and put the
directory's mtime back after creating one. Full triage in
`persistent-memory.d/2026-09-22-bug-hunt-panel.md`.