Files
booth/persistent-memory.d/2026-09-22-u2-bug-hunt-panel.md
Vuong Hoang d37b81ab9f memory: snapshot — U5 released at v0.3.0, and the index goes two-tier
The two dated log sections had never been split, so every one of their 29
entries sat inline and the startup index had grown to 372 lines — which is
the cost the two-tier scheme exists to remove, paid on every session that
reads the file. 27 entries were over threshold. All 29 now have a detail
file under persistent-memory.d/ and a one-line index entry that routes
rather than restates. Index: 372 -> 93 lines.

No archival. The soft cap fired, but every entry in this repo is dated
2026-09-21 or later, so the under-14-days guard held all of them back — and
the split alone took the index well under the target without moving
anything out of the active file.

The in-flight section is rewritten for the post-release state: nothing is
in flight, no gate is outstanding, and the next unit is explicitly recorded
as the operator's undecided call rather than as a plan. The session's
recommendation (U4, on three grounds) is written down so it does not have
to be re-derived, alongside the two alternatives and why they are
alternatives.

Two dated predictions are carried forward with their dates and their
instruments: the U5 adoption re-measure on 2026-09-29, which already reads
3 of 24 announced and 2 with a why from peers told nothing, and the
.forever re-count a fortnight AFTER U4 lands, which is U4's own success
criterion and is destroyed by running it early.
2026-09-22 08:20:51 -07:00

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Markdown

# 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`.