Six of the eleven defects here were in the MEASUREMENT, not the product, and they
were wrong in both directions.
Harness, all of which silently produced wrong numbers:
- coverage.py preflight refused every sweep on a box holding exactly one backend:
stack.sh's supervisor is a `bash -c` quoting the whole uvicorn line, so it carries
both "-m uvicorn backend.main" AND the venv python path. Discriminate on POSITION.
- stack.sh status reported 2 backends over 1 and 0 webpack over a live dev server
(webpack retitles its process). A status check whose job is preventing a second
stack, failing in the direction that lets one land.
- c7_run.sh/c8_run.sh slice r6_be.log while stack.sh names logs by TAG: a stack under
any other tag hands every trial an empty slice and the sweep reports a confident
0/108. Now refuses loudly; it caught this exact mistake on first use.
- "Browser command timed out" was bucketed infra. It is ONE command blowing its own
budget, not a dead webview: all 4 such rows were BrowserFindComposer at exactly its
30s cap, every run completed after, zero card-gone markers in the whole log. Filed
as infra it read as 11.8% flake AND lifted holdout reach 70% -> 84%.
- api_retry / rate_limit_error now grade as infra. A provider 429 storm turned clean
15-21s exclusions into 188s product_no_composer rows.
- bench.py prints reach BOTH ways when a row is UNVERIFIED. An exclusion resting on
the agent's own word quietly flatters the score, and coverage.py's own instruction
to confirm it by hand goes unread (I quoted a 100% that excluded onlinegdb).
Timing was measuring 0.2% of the run: prestage completes BEFORE metrics_started_at,
so other_ms was 25ms of a 12700ms median while prestage (4146ms, ~61%) sat in no
bucket at all. prestage_ms/task_ms are now recorded; total_ms is deliberately NOT
redefined, which would invalidate every before/after already taken against it.
Product:
- find_composer rejected ACE/CodeMirror-5/Monaco composers. Their input is a ~1x1
offscreen textarea that paints into a sibling div, so it can never pass a size
gate. Accept it when a VISIBLE ancestor is composer-sized; honeypots stay out
because the input itself must not be display:none/visibility:hidden/opacity:0.
anon reach 80% -> 100%, holdout 89% -> 90%, p95 38.6s -> 9.7s.
- the composer poll slept a blind 0+1.2+1.4 = 2.6s whenever prestage staged nothing,
which is nearly every run, and it was the whole of other_ms's suspicious constancy
(2610-2613ms regardless of tools_ms). Stop when two reads are identical, the rule
the opener poll 40 lines below already applies. other_ms -53.7%, tools_ms flat.
- prestage no longer navigates to the page it is already on, nor sleeps 0.35s before
its first settle probe.
- is_replay_boundary reasoned from the NAME alone, so x.com's composer textbox named
"Post text" was ruled an irreversible send and truncated its replay to a bare
navigate. Excluded by ROLE; first_unsafe_step now passes role through at all.
Measured on this box: reach 100% (83% if onlinegdb's unverified exclusion is bogus),
0 false successes in ~155 runs, prestage tier-0/1 2702ms, other_ms -53.7%, infra
flake 0/158, holdout 18/20. Criteria 2/4/9 need live writes and are untouched.
Full evidence, including what did NOT work, in e2e/browser-v3/RESULTS_2026-08-06.md.
Also drops the tracked electron/node_modules symlink pointing at another machine's
Downloads folder; it is dangling on every other checkout and re-breaks the install on
any stash or checkout.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
