pmacs/docs/ci-red-signatures.md

CI red signatures — the triage registry

This file is the single authority for judging a red CI run. It is an occurrence ledger, not a flake list: a row records what was seen, what is known about why, and what would retire it. A row is not a claim that the failure is harmless.

Deliberately not named "flakes". One of its rows is a possible product defect, and a filename that called it a flake would confer immunity the evidence does not support.

Read this before attributing any red run to the environment. Landed framing documents keep their own historical evidence and reasoning — that is not duplication, and it is not superseded by this file. What lives here is live triage policy.

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How a row matches

A test-name match is never sufficient. A red run matches a row only when all three hold:

1. the exact test selector matches;
2. the job / flavor matches;
3. every required fragment is present in the failure output.

Where a fragment lists alternatives (ESRCH / No such process), any one satisfies that requirement — those are the same condition rendered differently by platform or libc.

Fragments are normalized, never pasted verbatim. PIDs, elapsed times, thread ids and rendered OS-error suffixes vary between runs; a verbatim key would match nothing. The evidence link preserves the exact occurrence.

A failure in a listed test that does not carry that row's fragments is a NEW incident, judged on its own. The process test below is why this rule exists: it produced two signatures with different mechanisms and different causal status, and only one of them is a test bug.

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The rerun rule

This replaces "rerun before concluding", which conflated three different outcomes.

• A green rerun after a red establishes INTERMITTENCE ONLY. It does not establish environmental cause, harmlessness, or retirement.
• The same signature on the rerun is a SECOND OCCURRENCE. It remains blocking pending investigation or a merge-base control.
• A different signature is a NEW INCIDENT, judged independently.

A merge-base control — running the same command on the merge base — is what distinguishes "this branch caused it" from "this tree has it". It is cheaper than argument and is the correct response to a second occurrence.

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What retires a row

Retirement is causal, never a count of green runs. A row is retired by removing or explaining its mechanism:

causal status	retirement condition
test race	hardening that removes the named mechanism, plus a discriminating witness for the stronger predicate
measurement design	the owning lane replaces or justifies the measurement and pins the resulting claim
unresolved	diagnosis and an explicit disposition

Audit notes (A-numbers) have no retirement condition, because they have nothing to retire — see that section. A linked occurrence promotes one into an R row; absence retires nothing, because nothing was ever measured.

Main-branch greens are occurrence evidence and accumulate toward a rate. They retire nothing by themselves. Retired rows stay in this file with their disposition, so a recurrence is recognisable.

A red matching a RETIRED row AND POSTDATING ITS RETIREMENT is a recurrence, and it puts the retirement in question — it is not a known flake. The claim a retirement makes is that the mechanism is gone from the retirement forward; the same signature afterwards falsifies that claim, which is a stronger finding than a live row, not a weaker one. Reopen the row rather than rerunning.

A matching red that PREDATES the retirement corroborates the row instead. It is an additional occurrence of the mechanism the fix removed, so it strengthens the evidence and challenges nothing. Add it to the row's evidence; do not reopen. This is not a technicality — an occurrence scan reaches backwards by construction, so most matches it finds will be of this kind, and treating them as recurrences would reopen every retired row the first time anyone looked.

Both halves need the date, which means a row is unmatchable without one. R2's second occurrence (main run 30710662474, 2026-08-01, four days before its 2026-08-05 retirement) is the worked example, and it also shows the flavor field is not part of matching: R2's first evidence is macOS / lua54 and that one is macOS / luajit.

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Live rows

Four of the seven evidenced rows are live. R2 and R4 were retired on 2026-08-05 and R8 on 2026-08-08; all three are below, under "Retired rows", with their dispositions. R5 and R6 were added on 2026-08-06 from an occurrence scan and a live red; neither is diagnosed.

Rate, as of 2026-08-06. Of the last 25 main runs, 23 green and 2 red — the two reds being R2's second occurrence (30710662474) and R5 (30555667095). R6 has no occurrence in that window; it was first seen on a PR branch. This is the first rate this file has carried, and it is a floor rather than a measurement: it counts only main, only 25 runs, and only reds that were still readable.

R1 — supersede cancellation budget

Occurrence on PR #245, 2026-08-30, with a merge-base control run the same hour. Recorded together because the control is what the occurrence owed.

field	value
occurrence	Test (macos-latest / lua54), run 33303043179, job 99234587352, head d9cc0fa. 1984 passed; 1 failed, panic at src/async_runtime.rs:2444 with the row's required fragment supersede did not cancel within 50ms
merge-base control	the SAME job at the branch's exact merge base 2e9f62b — run 33277675008, attempt 2, job 99239538960 — GREEN, 1985 passed; 0 failed, the selector reading ... ok in its log
both logs preserved	before the rerun, so neither is reconstructed from a conclusion

THIS IS R1, and the new Lua flavor does not change that. The row records macOS / luajit; this occurrence is macOS / lua54. Flavor is not part of signature matching — the selector and the required fragment are, and both match exactly.

What the GREEN control establishes, and what it does not:

• It does NOT establish environmental cause, and it does NOT retire R1. A green control shows only that the merge base can pass the same job in the same hour.
• A RED control would have established something specific — that the branch did not introduce the occurrence. This control was green, so that inference is unavailable and is not claimed.
• R1 remains LIVE either way, under its existing measurement-design disposition. Its retirement condition is unchanged: the async-runtime lane replaces or justifies the measurement (Q#MCI3).

The assertion still omits its measurement. started.elapsed() is in hand at the panic and the message reports none of it, so this occurrence's margin is as unrecoverable as every prior one's. Recording that is not the same as proposing to fix it here. Adding the elapsed value would improve the NEXT failure's evidence and would repair nothing about the measurement design this row is actually about — the premise that a thread::sleep(15ms) means the worker picked the job up. That belongs to the async-runtime lane, with the rest of Q#MCI3.

field	value
selector	--lib async_runtime::tests::supersede_cancels_in_flight_job_within_50ms
job / flavor	macOS / luajit
required fragments	supersede did not cancel within 50ms
causal status	measurement design
evidence	#213 run 30826884642
retirement	the async-runtime lane replaces or justifies the measurement (Q#MCI3)

The test's premise is thread::sleep(15ms), asserted by comment to mean "the worker picked the job up"; under load it may not have, in which case the test measures the queued path while claiming the running one. And its 50ms clock starts before the second dispatch and is consumed by the test's own tick() + sleep(1ms) pump, so the interval is dominated by when the test was scheduled. Widening the budget would make it pass and measure nothing more.

R3 — live-leader EPERM with an unobservable group

field	value
selector	--lib process::tests::a_successful_signal_disposition_depends_on_whether_it_is_fatal
job / flavor	macOS / lua54
required fragments	EPERM and measured_group=unobservable( and (ESRCH / No such process) and leader=live
causal status	UNRESOLVED — possible product defect
evidence	#214 run 30932558752 attempt 1
retirement	diagnosis and disposition by the process-signal / reap-ledger lanes. Never a green rerun.

Same test as R2, different mechanism, different status. This is the group-target behaviour #176 and #200 circled and the reap-ledger lane parked every disposition change pending: a group-directed kill returned EPERM while the leader was observed live, and measured_group — the one field able to disagree — could not be read at all.

Do not treat a red matching this row as environmental. A green rerun changes nothing about it.

R2's retirement does not touch this row, and must not be read as touching it. The 2026-08-05 hardening changed that test's fixture — a readiness gate and an exec — and changed no product code at all; the same group-directed kill runs against the same supervisor. What the fixture change does do is alter the shape of the group being signalled (one process now, where a forked sleep could make two), so a change in how often this row appears would be evidence about frequency, not about cause. A red carrying these fragments after that date is this same unresolved row, and its retirement is still a diagnosis by the process-signal / reap-ledger lanes.

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R5 — async pump deadline exceeded in the supersede close path

field	value
selector	--lib editor::tests::stream_supersede_delivers_cancelled_to_on_close
job / flavor	macOS / lua54
required fragments	async pump deadline exceeded
causal status	UNRESOLVED — no diagnosis
evidence	main run 30555667095, 2026-07-30
retirement	diagnosis by the async-runtime lane, alongside R1's measurement question (Q#MCI3). Never a green rerun.

Not R1, though it is the nearest thing to it. R1 is async_runtime::tests::supersede_cancels_in_flight_job_within_50ms failing supersede did not cancel within 50ms; this is a different test in a different module failing a different assertion. They share a subject — supersede, under a deadline, on macOS — and sharing a subject is not sharing a signature. Filed separately so that a fix for one is not read as a disposition for the other.

What the row does not claim: that the pump is slow, that the deadline is wrong, or that this is the same measurement-design problem R1 has. Nothing here has been diagnosed. It is recorded because it happened and had a signature, which is the entire bar for a row.

R6 — readiness file never published in the panel terminal fixture

field	value
selector	--test bottom_panel_stage1_acceptance acc28_child_input_and_the_c_c_escape_work_unchanged_in_a_panel
job / flavor	macOS / lua54
required fragments	timed out waiting for and /ready
causal status	UNRESOLVED — no diagnosis. SECOND OCCURRENCE 2026-08-31, 26 days after the first
evidence	#217 run 31023651701, 2026-08-05. Second: PR #246 job 99431791766, head e87d227
retirement	the readiness helpers are audited and reconciled, with a witness. Never a green rerun — the next push was green and that retires nothing.

Second occurrence — the CRDT identity-undo lane, 2026-08-31, Test (macos-latest / lua54) on PR #246. A full three-condition match, which this file requires and which is worth spelling out because the last occurrence of this selector could not be matched at all:

1. selector — acc28_child_input_and_the_c_c_escape_work_unchanged_in_a_panel;
2. job / flavor — macOS / lua54, the same leg;
3. both required fragments — timed out waiting for /var/folders/df/djsxfhc17x95674wsm_g8s980000gn/T/.tmpyBcHeZ/ready.

Panic at tests/bottom_panel_stage1_acceptance.rs:2454, 46 passed; 1 failed.

The log was read BEFORE anything was rerun. U3 named that lesson, U8 recorded its fourth violation, and this is the first occurrence in this file's history where the rule was followed on a macOS job at the moment it mattered. The fragments above exist because of it.

Not attributed to the observing lane, and a merge-base control was dispatched rather than argued. The branch's whole diff is src/buffer.rs, src/rope.rs, src/overlay.rs, src/view.rs (tests and doc comments) plus three docs — no file under tests/, and nothing in the panel, process or terminal paths. But "my diff looks unrelated" is not evidence, so run 33375945966 was dispatched at aae5b35, the branch's exact merge base, via the workflow_dispatch key #245 landed for precisely this. This is that key's first real use, and U11 — the row that motivated it — is why it exists.

THE CONTROL LANDED GREEN on the macOS legs, and the meaning was pre-registered above before the result was seen: Test (macos-latest / lua54) succeeded at aae5b35. So the inference this control could have supplied — that the branch did not introduce the failure — is unavailable. What is established is only that the merge base can pass the same job in the same hour. That is exactly what R1's row had to record about its own green control, and it is recorded the same way here: a null result, not an exculpation.

The control run was not otherwise clean, and that is its own finding. Test (crdt) failed on main at aae5b35 — see U17. A red on the merge base is not something a PR run can show you; it took a dispatch on main to see it at all.

Circumstantial alignment with U8, deliberately NOT a merge. U8 has the same selector, panicking at the same line :2454 with the same 46 passed; 1 failed, on macOS luajit at base 0190102. That is suggestive. It is also unconfirmable: U8's fragments were destroyed, and a row with no fragments cannot be matched — which is exactly what U8's own entry says it is for. The alignment is recorded here so a future reader sees it; U8 stays a separate row, and the inference stays unavailable.

A THIRD copy of the readiness helper. R4's disposition already recorded that the empty-file predicate lived in a second helper (wait_for_published_file) and warned that leaving it would let the mechanism recur under a different selector as a new incident. tests/bottom_panel_stage1_acceptance.rs:2446 is a third, independently written wait_for_file carrying only half the hardening: it rejects a zero-byte file (!bytes.is_empty()) but never waits for the expected content.

So the honest statement is narrow. This red is a timeout, not R4's left: [] / right: [49], and a timeout is what a correct predicate does when the content never arrives — it is not evidence of the R4 bug. What is established is only that a third copy exists and diverges from the other two. Whether this occurrence is a slow runner, a child that never published, or something in the panel path is not known, and the suite passed 5/5 locally on Linux, which reproduces nothing about a macOS runner and is not evidence about this occurrence.

The scope this row implies is the audit, not the test: how many readiness helpers exist, whether they can be one, and what each promises. Patching this call site alone would leave the same question open under a fourth selector.

Retired rows

These stay here on purpose. A retirement is a claim that a mechanism is gone; keeping the signature is what makes a recurrence recognisable as a falsification of that claim rather than as a fresh mystery. Both were retired causally — the mechanism removed, plus a discriminating witness that fails without the fix — never by a count of green runs. R8 joined them on 2026-08-08, and unlike the other two it was never intermittent — it was deterministic, and the "flake" reading was never available to it.

R8 — LSP listview row rendered relative to a stray ancestor marker — RETIRED 2026-08-08

field	value
selector	--test m4_acceptance flat_listview_consumers_render_byte_identically_after_the_tree_extension
job / flavor	local (Linux), any invocation — isolated single-test runs included. Not load-sensitive
required fragments	the flat references row renders verbatim and a left value that is the right value with a leading directory removed
causal status	DIAGNOSED and FIXED — test hermeticity
evidence	reproduced deterministically on one Linux workstation; merge-base control confirmed it on main
disposition	tests/m4_acceptance.rs::open_against_fake now sets pmacs.project.set_search_boundary to the fixture directory. docs/r8-fixture-boundary-framing.md

Mechanism, established rather than guessed:

1. builtin/runtime/lsp.lua:2397 display_path shortens a location against the detected project root before rendering it.
2. pmacs.project.detect walks upward for a marker. From /tmp/.tmpXXXXXX/r.rs it reached /tmp.
3. That machine had a stray /tmp/.git — an empty directory, not a repository. The .git marker is directory-only, so an empty directory still matched.
4. Root resolved to /tmp, the prefix was stripped, and the row rendered as observed.

Control at diagnosis time: the same test with TMPDIR outside /tmp passed.

The product behaviour was never wrong and was not changed. Shortening a location against its project root is the feature. The defect was that the fixture did not bound its own project detection, so its assertion depended on what the developer's /tmp contained. src/project.rs:208 had documented this exact hazard — "a developer's /tmp/.git", in those words — and provided detect_project_within; open_against_fake was one helper that missed the pattern the same file already used five times.

Retired causally, and the witness is portable. A new test, a_planted_ancestor_marker_does_not_reach_the_rendered_row, plants an empty .git in a temporary ancestor and asserts the rendered row stays absolute. Removing the boundary fails it deterministically on every machine — including CI, where no /tmp/.git exists — because the planted marker is nearer than any real one. The original machine's stray directory was corroboration, never the proof, and it was deliberately left in place: deleting it would have hidden the hermeticity defect.

Provenance of that /tmp/.git remains unresolved and is not needed. Observations of its timestamps disagreed, and /tmp is a tmpfs whose entries are touched by inspection, so no timestamp is authoritative here. It may have been created by the session that found the row. The fix does not depend on the answer.

What this retirement does NOT claim: that the rest of the suite is hermetic. EditorState::new_with_roots is called 113 times in m4_acceptance alone, an unknown number of them equally unbounded — harmless only while their assertions do not render a path. That census is a named follow-on in docs/agent-handoff.md §6, not a completed audit.

R2 — USR1 delivered before the trap is installed — RETIRED 2026-08-05

field	value
selector	--lib process::tests::a_successful_signal_disposition_depends_on_whether_it_is_fatal
job / flavor	macOS / lua54
required fragments	leader=exited(signal SIGUSR1) — one exact fragment, not two loose ones. Split into leader=exited( and SIGUSR1 it would match a child that exited by some other disposition while SIGUSR1 appeared elsewhere in the output
causal status	test race
evidence	#213 run 30927084982 attempt 1; and main run 30710662474, 2026-08-01, macOS / luajit — same exact fragment on the other flavor, found by an occurrence scan on 2026-08-06
retirement condition	the fixture proves the trap is installed, with a witness that fails without it
disposition	met. The child publishes a readiness marker after trap '' USR1, the test waits for that marker's content, and process::tests::usr1_readiness_waits_for_the_trap_not_for_the_spawn is the witness

Readiness was ProcessEventKind::Started, emitted at spawn — not when /bin/sh has parsed trap '' USR1. SIGUSR1's default disposition is terminate, so a signal inside that window kills the child. The fixture's own comment stated the requirement it did not enforce.

Three things the fix and the witness settled that the row did not say:

• Which call failed. The fragment is rendered only on a failed kill, and the USR1 that killed the child cannot itself have failed — it is what did the killing. The failing call is therefore the SIGTERM that follows, whose diagnostic reports the leader's earlier death. Why a group-directed TERM found no group is not established here, and the fix does not depend on the answer. This says nothing about R3, whose leader was observed live.

• The witness proves the predicate, not the platform. The old fixture passes on Linux; the window is real everywhere but only macOS ever reported it. So the witness widens the pre-trap window deliberately (the fixture sleeps before trap) instead of hoping a loaded runner supplies one, and it proves survival by the child's exit disposition — a child that took the USR1 reports Signaled { signal: "SIGUSR1" } — rather than by an absence observed within a window.

• The second occurrence is pre-retirement, and that is the whole question. main run 30710662474 predates the 2026-08-05 retirement by four days, so it corroborates the row rather than falsifying its disposition — a red matching a retired row is a recurrence only if it postdates the retirement, and the rule above is about the claim a retirement makes going forward. It does add something: this row's evidence was macOS / lua54 and this one is macOS / luajit, so the mechanism was never flavor-specific, which is what the fix already assumed when it widened the window deliberately rather than hoping a loaded runner supplied one.

  It was also very nearly filed as R3. Same test, same EPERM, same measured_group=unobservable(ESRCH…) — and R3 explicitly requires leader=live, where this reads leader=exited(signal SIGUSR1). Matching on the shared fragments and the shared test name would have attached a live, unresolved possible-product-defect row to an occurrence of a retired test race. This is why the rows key on exact fragments and why R2's says "one exact fragment, not two loose ones."

• The fixture had a second, unnamed dependency. These signals are group-directed, so a forked sleep would be an untrapped member of the same group. That it survived at all depended on the shell suppressing the fork for the last command of a -c script — a bash and dash optimization, not a guarantee. The fixture now says exec, and an ignored disposition survives exec by POSIX.

R4 — readiness predicate satisfied by an empty file — RETIRED 2026-08-05

field	value
selector	--test vterm_stage2_acceptance terminal_escape_gates_local_bindings_and_double_escape_sends_interrupt
job / flavor	macOS / luajit
required fragments	left: [] and right: [49]
causal status	test race
evidence	#214 run 30932558752 attempt 1
retirement condition	wait_for_file requires the expected content, with a witness that fails against a zero-byte file
disposition	met. The helper takes the expected bytes and waits while the file holds a strict prefix of them; wait_for_file_does_not_return_a_zero_byte_readiness_file is the witness, and with the old predicate restored it fails with left: [], right: [49] — this row's two fragments, verbatim

wait_for_file returned as soon as fs::read succeeded — which succeeds on a zero-byte file. The probe writes readiness with open(path,'wb').write(b'1'), and open() creates the file before write() fills it. The predicate was "readable"; the assertion is "contains 1" (49 is ASCII '1').

Two notes for anyone who reads a future red here:

• The same mechanism lived in a second helper. wait_for_published_file, one function away in the same suite, gated the real-TUI smoke's assert_eq!(…, b"1") on the identical "readable" predicate. It was fixed with the same predicate; leaving it would have let this row recur under a different selector, which the registry would have had to judge a new incident.
• The helper returns divergent content instead of waiting for a match, so a child that publishes the wrong thing is reported as a diff by the caller that owns the expectation, rather than as a timeout in a helper that does not. That behaviour has its own witness.

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Audit notes — historical claims with no linked occurrence

These are NOT registry rows. They carry A-numbers, not R-numbers, because nothing here can be matched against a red run and nothing here confers any status.

They were named in the handoff's hazards list without evidence. The audit found the tests real and the claims recorded in good faith — but an assertion string existing is not a mechanism, and "timing-based" is not an observation. No occurrence of either was ever linked, so nothing is known about how either fails, or whether either has failed.

Deleting them would discard a real recorded belief. Listing them beside the evidenced rows would grant the reputation this file exists to deny. So they are stated as what they are: claims awaiting a first occurrence. A red in either test is a first recorded occurrence, to be investigated and then promoted to an R row — not matched against anything here.

A1 — GPU terminal cell background did not paint

field	value
selector	-p pmacs-gpu a33_headless_terminal_frame_paints_cells_without_document_layers
job / flavor	GPU Render (headless), under parallel load
required fragments	the terminal cell background did not paint + blue pixels
status	historical claim, no linked occurrence
what IS established	the test exists and the assertion string is real (pmacs-gpu/src/main.rs:17973). That is all
what is NOT	any mechanism, and any occurrence. No run was ever cited
promotion	a linked occurrence makes this an R row with a signature. Absence retires nothing, because nothing was measured

A2 — supervisor reap across cycles

field	value
selector	--test m6_8_multi_repl_acceptance m6_8_supervisor_reaps_all_children_across_cycles
job / flavor	not recorded
required fragments	not recorded — no signature was ever captured
status	historical claim, no linked occurrence
what IS established	the test exists and runs 10 cycles; the handoff called it "timing-based"
what is NOT	any mechanism, any signature, any occurrence
promotion	a linked occurrence with a captured signature makes this an R row

A2 cannot be matched, and neither can A1 — that is what makes them notes rather than rows. A red in either test is a new incident by default. That is the correct outcome for an entry that never carried evidence, and it means this file is stricter than the list it replaces: nothing is pre-excused.

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Occurrence log

date	run	row	outcome
2026-08-04	30826884642	R1	rerun green — intermittence only
2026-08-04	30927084982 att.1	R2	rerun green — intermittence only
2026-08-04	30932558752 att.1	R3, R4	rerun green — intermittence only; R3 remains unresolved

Four incidents, three tests, four signatures. Count signatures: the process test contributed two, and only one of them is a test bug.

date	row	event
2026-08-05	R2, R4	retired — mechanism removed, discriminating witness added; see "Retired rows"

U1 — an unclassifiable local red (long-lines lane, 2026-08-07)

Recorded because the alternative is to not record it. It is not a row, cannot be matched, and excuses nothing.

field	value
selector	PMACS_REQUIRE_GPU=1 cargo test -p pmacs-gpu — test name not captured
job / flavor	local (Linux), immediately after a 60s m4_acceptance run
required fragments	none captured
status	unclassifiable — evidence destroyed at capture time
what IS established	test result: FAILED. 227 passed; 1 failed was emitted once
what is NOT	which test, why, and whether the lane caused it
cause of the gap	the command piped through tail -3, which kept the summary line and discarded the failure block above it

Not matched against A1 despite A1 also being GPU-headless-under-load. Matching needs an exact selector and every required fragment; this has neither, and treating a shapeless red as "probably the known one" is precisely the reputation-by-adjacency this file exists to deny.

Follow-up: 36 subsequent full runs clean, 6 of them under deliberate concurrent load (m4_acceptance in parallel). Per the rerun rule that establishes intermittence only — and here not even that, since without a name there is nothing to call intermittent.

The lesson is mechanical, not analytical: never pipe a gate through tail/head on the run whose result you intend to report. Filter with grep -E "FAILED|panicked|test result", which keeps failure context, or capture the full log to a file and summarize from it.

R7 — managed-retry attach hits a broken pipe under full-sweep load

The first incident this session with a complete signature, so it is a matchable row rather than a U note. Recorded during long-lines Stage 4; the lane touches no pmacs-gpu code at all.

field	value
selector	-p pmacs-gpu attach::tests::managed_retry_survives_transients_and_uses_the_successful_stream
job / flavor	local (Linux), cargo test --workspace --features crdt --no-fail-fast, i.e. under full-sweep load
required fragments	transient sequence must attach + Handshake(Io( + BrokenPipe (or code: 32)
status	EIGHTH OCCURRENCE 2026-08-30 — causal status still UNRESOLVED. The eighth carries the strongest tree exclusion this row has had, and it supersedes the fifth's: two consecutive gate runs on ONE worktree whose heads differ by a single markdown file, the first all-green and the second red
what IS established	three occurrences at pmacs-gpu/src/attach.rs:1680, the second and third with all three fragments verified rather than inferred; the test drives a scripted transient-then-success sequence over a real socket pair. The added GPU test is not the mechanism — see the third-occurrence control below
what is NOT	whether the broken pipe is the fixture's writer closing early or a real retry-path defect. This row is not a claim that it is harmless
rerun evidence	occurrence 1: 6 isolated runs green, plus a full --workspace --features crdt sweep green (113 targets). Occurrence 2: 30 green on the observing branch (15 isolated selector, 15 full -p pmacs-gpu) plus a 15-run merge-base control, also green. Occurrence 3: 5 isolated selector runs green, 10 full -p pmacs-gpu runs green with the added test, and 1 failure in 10 with the added test #[ignore]d — the first rerun in this row's history that reproduced anything. Per the rerun rule the green runs establish intermittence only; the red control run is what carries the exclusion
retirement	hardening that removes the named mechanism plus a discriminating witness — or a diagnosis showing the fixture, not the code, closes the pipe

Eighth occurrence — the CRDT identity-undo lane, 2026-08-30, local (Linux), gpu step. All three required fragments present in the durable log (pmacs-fdccc423/gate-logs/20260830T155621Z-3005460/06-gpu.log):

transient sequence must attach: Attach(Handshake(Io(Os { code: 32,
kind: BrokenPipe, message: "Broken pipe" })))

at pmacs-gpu/src/attach.rs:1889, 283 passed; 1 failed.

This occurrence discriminates tree from runner more sharply than any before it, and the reason is the pair, not the diff. Two consecutive scripts/gate runs, same worktree, minutes apart:

run	head	delta from the previous run	result
20260830T154827Z-2907414	db24ae3	—	all 8 stages green
20260830T155621Z-3005460	96bf2c3	one commit, touching one file: docs/active-work.md	gpu and sweep FAILED

The fifth occurrence excluded the observing tree relative to main by having a documentation-only diff. This pair excludes it relative to the immediately preceding green run of the same gate on the same worktree, where the entire delta is a markdown file that no Rust target reads. Whatever varies between those two runs, it is not the source tree.

sweep failed with the SAME single test, so this run is one failure surfacing in two stages, not two failures. Both stage logs name attach::tests::managed_retry_survives_transients_and_uses_the_successful_stream and nothing else: 283 passed; 1 failed in each.

• Rerun: isolated selector green five times (1 passed, 0.00s each). Per this file's rerun rule that establishes intermittence only — and per the seventh occurrence's correction, running the selector outside the gate excludes nothing at all, because nothing outside the gate has ever reproduced this failure.
• No ratio is claimed from this occurrence. It is one in-gate failure following one in-gate pass, on a lane whose gate runs exist to verify a head rather than to observe this row. Folding them into the 2026-08-29 window would be exactly the drift that window was bounded to prevent.
• The observing lane touches no pmacs-gpu file: its whole diff is src/buffer.rs, src/rope.rs, src/overlay.rs, src/view.rs — tests and doc comments — plus three docs.
• The NEXT in-gate run was green, all eight stages (20260830T160242Z-3095339), one commit later. Recorded because omitting it would be selective, not because it resolves anything: per the rerun rule a green run establishes intermittence only, and the seventh occurrence already falsified "in-gate always fails".

What this changes about the method, stated at the strength it carries. The seventh occurrence's narrowing said the remaining candidates must be varied INSIDE the gate, one per run. This pair sharpens one exclusion and nothing else: the Rust source tree is not the variable.

It does not narrow the cause to three things. The gate's per-run state — its ambient root, its fresh TMPDIR, and process state carried across stage boundaries — remains the set of candidates this project can actually vary one at a time, which is why they are the ones to try. But they are not an exhaustive causal set, and an earlier version of this paragraph said they were. Everything unrelated to the repository also differed between the two runs: scheduler load and CPU contention, kernel and socket timing, page cache and memory pressure, and whatever else the machine was doing at 15:48 versus 15:56. A socket handshake racing a BrokenPipe is exactly the kind of failure those can drive, and holding the tree fixed says nothing about any of them.

Sixth occurrence — the parse-budget diagnosability lane, 2026-08-29, local (Linux), gpu step. All three required fragments present in the durable log (pmacs-parse-budget-9c27ecfe/gate-logs/20260829T144541Z-350549/06-gpu.log):

transient sequence must attach: Attach(Handshake(Io(Os { code: 32,
kind: BrokenPipe, message: "Broken pipe" })))

at pmacs-gpu/src/attach.rs:1889, 283 passed; 1 failed.

• The tree exclusion is as strong as the fifth's. The observing lane's entire diff is src/async_runtime.rs, tests/m4_acceptance.rs and three docs — no pmacs-gpu file, and no file pmacs-gpu links against beyond the workspace it always did. The change is two assert! message strings.
• Rerun: isolated selector green three times (1 passed, 0.01 s each), which is this row's established control shape.
• THE SAME RUN'S sweep STAGE WAS TRUNCATED, and is not evidence. The gate was running in a background task that was killed at 314s; 07-sweep.log ends in Terminated. That stage's absence says nothing, and the run as a whole is not a gate result. Only the gpu stage's failure is, because it completed and reported. A SEVENTH OCCURRENCE FOLLOWED IMMEDIATELY, on the next gate run of the same worktree at head 45d438c (20260829T150011Z-429115/06-gpu.log), same selector, same three fragments, 283 passed; 1 failed. That run's other seven stages were green, sweep included and complete — 121 result lines, none with a failure — so this pair is not confounded by a truncation the way the sixth was.

Two consecutive in-gate failures is new for this row, whose prior five were spread across lanes and months. It prompted a narrowing, and the narrowing is the useful part.

A THIRD IN-GATE RUN WAS GREEN (head 68a16f9, log 20260829T152024Z-563254, all eight stages, zero failures anywhere). So "in-gate always fails" is false, and the paragraph below was written before that run and is corrected rather than deleted.

Seventeen green runs outside the gate, in four configurations, all at head 45d438c on the failing worktree:

condition reproduced outside the gate	runs	result
isolated selector	3	green
full -p pmacs-gpu binary	6	green
full binary under a gate-shaped 61-character TMPDIR (tested because this project already knows socket-path length matters)	6	green
m4 then gpu back to back, as the gate orders them	2 pairs	green

THESE ARE NOT EXCLUSIONS, and an earlier version of this entry called them that. The reasoning was wrong: nothing outside the gate has ever reproduced this failure, in 17 runs across four configurations — so matching one gate condition at a time outside the gate cannot isolate an in-gate cause. All these runs establish is that none of the four conditions by itself reproduces the failure. They do not show that any of them is uninvolved when the gate supplies the rest.

THE OBSERVATION WINDOW IS BOUNDED, deliberately. It is the first four in-gate runs of 2026-08-29 — 20260829T144541Z, T150011Z, T152024Z, T152824Z — plus the 17 out-of-gate runs taken between them. Later head-exact verification gates on this lane are NOT part of it and do not move these numbers. Without that boundary the tally re-counts itself every time a review round adds a docs commit and the gate is re-run, which is a ratio that drifts with review activity rather than with the phenomenon.

What the window supports, at the strength it carries: in-gate 2 failures in 4; out-of-gate 0 failures in 17. That asymmetry is suggestive and it is not a clean split, because the third in-gate run passed.

The method for the next occurrence follows from that. Varying conditions outside the gate cannot answer this question. It has to be varied INSIDE — the gate's ambient root, its exported environment, and process state carried across stage boundaries are the uneliminated candidates, and each would need a gate run with that one thing changed.

Causal status: still UNRESOLVED. What these occurrences add is a sharper question and a method, not a cause: previous entries compared lanes and trees, and these locate the asymmetry in the runner while showing that the obvious way to probe it — reproducing gate conditions outside the gate — cannot work.

Fifth occurrence — panel cell-mapping generation (§5b) framing, 2026-08-15, local (Linux). The scripts/gate gpu step again, the same flavor as occurrence 2, inside a --protocol run (log 20260815T072601Z-2230169).

• All three fragments verified from the durable log, not a filtered stream: transient sequence must attach: Attach(Handshake(Io(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" }))).
• The line moved and that is not a fragment. It is pmacs-gpu/src/attach.rs:1728 here against :1680 in the earlier occurrences — attach.rs has changed since, and this row's convention already treats a :LINE suffix as occurrence-specific.
• The tree exclusion is the strongest available in this row's history: the branch's entire diff is DOCUMENTATION. No Rust, no wire surface, no pmacs-gpu file. Occurrences 1 and 4 argued "unrelated lane"; this one cannot be related at all.
• Rerun: isolated selector green (1 passed, 0.01 s). Per this file's rerun rule that establishes intermittence only and does not exonerate the tree — though here there is no tree change to exonerate.

What five occurrences now support, stated carefully: the failure is not lane-correlated. It has appeared under three flavors across five unrelated lanes, once on a diff that touches no code whatsoever. That is evidence about where the cause is not, and still says nothing about what it is. The retirement condition is unchanged.

Not attributed to the observing lane, and in neither case is the reasoning merely "my diff looks unrelated": long-lines Stage 4 added no wire surface, no protocol version change, and touched no file in pmacs-gpu.

Second occurrence — worker identity Stage 1, 2026-08-09, local (Linux). Recorded at the scripts/gate gpu step (PMACS_REQUIRE_GPU=1 cargo test -p pmacs-gpu), which is a third flavor: not the --features crdt sweep of occurrence 1, and not U3's default-features workspace sweep. Two things make it a match rather than a U note:

• The fragments were captured this time. transient sequence must attach: Attach(Handshake(Io(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" }))) — all three of the row's required fragments, verified against the durable gate log rather than a filtered live stream. That is what U2 and U3 both lost, and it is why U3 could not be judged a recurrence. Reading the gate's own NN-gpu.log is the mechanical fix U3 prescribed, and it worked.
• The merge-base control R7 asked for was run — 15 runs at 4bc55e8, green. It is non-discriminating, not exculpatory: the observing branch was equally green over 30 runs, so neither side reproduced and the control separates nothing. Recorded as a null result rather than as evidence.

One causal path is NOT excluded and is named here rather than dismissed. The observing lane added a test to pmacs-gpu's test module (main.rs) — a GPU-heavy render_offscreen case. It touches no attach.rs, no protocol, and no wire, but it does add a concurrent test to the same binary, and the failing test is a socket handshake with a one-second deadline. Contention is a plausible mechanism for a BrokenPipe, and 30 green runs do not rule it out. If a third occurrence lands, run the control with the added test removed rather than at the merge base — that is the discriminating comparison this one was not.

Fourth occurrence — the scripts/gate TMPDIR isolation lane, 2026-08-13, local (Linux). Same selector, same gpu-step flavor (PMACS_REQUIRE_GPU=1 cargo test -p pmacs-gpu), all three fragments verified against the durable gate log (20260813T143421Z-708100/07-gpu.log): transient sequence must attach: Attach(Handshake(Io(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" }))).

One thing this occurrence ESTABLISHES. The observing lane touches no pmacs-gpu file at all (git diff ca92796..HEAD -- pmacs-gpu/ is empty) and adds no test to that binary. Occurrence 3 excluded "the added GPU test is the mechanism" by a control; this occurrence reproduces the signature with nothing added to the binary, which is independent corroboration rather than a repeat of the same argument.

The observing lane is environmentally non-neutral, and that is recorded as a CHANGE rather than as a mechanism. It moves the gate's TMPDIR off /tmp, which on this machine puts every tempfile::tempdir() in the run on btrfs instead of tmpfs. Noted so a later occurrence can compare like with like.

A causal claim built on that was advanced here and is WITHDRAWN. The draft argued the test's one-second deadline plus a slower filesystem was a plausible new mechanism. It does not hold on inspection: the deadline bounds the connection RETRY loop, not the socketpair handshake that returned BrokenPipe, and the filesystem work happens before that deadline is armed. The tempdir is created and never bound — the failing I/O is on a UnixStream::pair. Recording a mechanism that the code does not support is worse than recording none, because the next occurrence gets measured against a story instead of against the evidence.

So the causal status is unchanged by this occurrence: UNRESOLVED, with no new mechanism. What it adds is the corroboration above. Three isolated re-runs on the current tree were green, which by this file's own rule establishes intermittence only.

The discriminating comparison for a fifth occurrence remains the one the third occurrence prescribed. One occurrence, with no supported mechanism, is not grounds to reverse a fix that closes two observed hazards.

Third occurrence — worker identity Stage 1 review round 2, 2026-08-09, local (Linux). Same selector, same gpu-step flavor, all three fragments verified against the durable gate log (20260809T172606Z-1387979/11-gpu.log): transient sequence must attach: Attach(Handshake(Io(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" }))). A match on this file's own rule, not a U note.

The control the second-occurrence note prescribed was run, and this time it discriminated — against the hypothesis. Ten full PMACS_REQUIRE_GPU=1 cargo test -p pmacs-gpu runs with the added render_offscreen test present: 10/10 green. Ten more with that test #[ignore]d, changing nothing else: 1 failure in 10, carrying all three required fragments (without/run-6.log, pmacs-gpu/src/attach.rs:1680).

So the concurrent-GPU-test path named above is excluded: removing the suspect made the failure more frequent, not less, which no contention story from that test survives. What the run does establish is that the failure reproduces on demand at roughly 1-in-10 under ordinary -p pmacs-gpu load — the first time any rerun in this row's history has reproduced it at all. That is a materially better starting point than three isolated sightings, and it is the fact a diagnosis should be built on: the rate makes a bisect of attach.rs's handshake path affordable, where before it was not.

It is still not attributed to the observing lane, and now for a measured reason rather than an argument from diff shape: the arm without the lane's only pmacs-gpu addition is the arm that went red.

What would retire it is unchanged — the mechanism, not the rate. The next agent to touch this row should reproduce at 1-in-10 and instrument which side closes the pipe, rather than re-running for green.

Fourth occurrence — D3 file-watch scheduler (PR #235), 2026-08-11, local (Linux), at the gate's SWEEP step (cargo test --workspace --no-fail-fast, default features — U3's flavor, this time with the fragments captured). All three required fragments verified against the durable gate log (pmacs-fdccc423/gate-logs/20260811T150651Z-1481359/08-sweep.log): transient sequence must attach: Attach(Handshake(Io(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" }))), attach.rs:1680. 242/243 in the target; the same sweep had passed twice earlier the same day on materially the same tree (the diff between runs was a test file and docs — no pmacs-gpu code, no wire, no protocol, the strongest non-attribution shape this row has had). Ambient context, recorded not asserted: load average ~5.2 and four leaked pmacs --daemon processes resident. Consistent with the established ~1-in-10-under-load rate; adds no new mechanism evidence. The retirement bar is unchanged.

U2 — m6_1_pty_raw_mode_disables_kernel_echo, THIRD known occurrence

Corrected 2026-08-09 after review. A previous edit of this row called the 2026-08-09 failure the second occurrence and claimed it captured the fragment for the first time. Both were wrong, and the evidence was already in this repository: docs/active-work.md records a 2026-08-06 loaded --features crdt run failing this selector and m6_1_pty_canonical_mode_keeps_kernel_echo with the same stty -a output was: "", and it already proposed a mechanism family — read-before-write on the child's output, the shape of R4 (readiness predicate satisfied by an empty file) and R6 (readiness file never published).

So the fragment was captured before, under another feature flavor, and this row's earlier "no mechanism has been proposed" was false of the tree it was written in.

field	value
selector	--lib process::tests::m6_1_pty_raw_mode_disables_kernel_echo
job / flavor	local (Linux), during cargo test --tests --no-fail-fast — the lib target alongside a full PTY-heavy corpus
required fragments	panicked at src/process.rs:3953 · raw mode should disable echo; stty -a output was: ""
status	at least three occurrences, load-correlated; the diff is EXCLUDED on the 2026-08-09 one
what IS established	Three occurrences. (1) the original: failed once (1916 passed; 1 failed) under a full-corpus --tests --no-fail-fast run, fragments not captured. (2) 2026-08-06, loaded --features crdt: this selector and m6_1_pty_canonical_mode_keeps_kernel_echo both failed with the same stty -a output was: "" — the first capture, and the occurrence that proposed the read-before-write family. (3) 2026-08-09, worker-identity tip: 1919 passed; 1 failed in scripts/gate step 03-lib at load ~21, and the tree contained ZERO code change since a 13/13 green run on the same lane — the only delta was three lines of docs/active-work.md. A markdown edit cannot break a PTY test, so the change under test is ruled out as a cause rather than merely doubted. Passes isolated (1 passed, 0.01s). Occurrence 2 is the one that matters most: it shows the failure is not confined to one feature flavor and can take both selectors at once
what the fragment ACTUALLY shows	The supervisor collected empty stdout — drain_until then collect_stdout(&evs) (src/process.rs:3948-3951); the assertion inspects that string. It does NOT establish that stty emitted nothing: the bytes could have been lost in PTY delivery or in event collection. An earlier edit of this row said "stty produced no output at all", which asserts a mechanism the test cannot see. What is true is narrower and still useful: this is not a termios failure — nothing shows echo being configured wrongly — but which of {child never wrote, PTY dropped it, collection missed it} is open. The assertion's message invites the wrong reading, since it prints an empty string as though it were stty's answer
what is NOT	No mechanism is ESTABLISHED — one is proposed: read-before-write on the child's output, the R4/R6 readiness family (occurrence 2). Proposed is not confirmed, and nothing here discriminates it from PTY delivery or event-collection loss. Not reproduced in a later full sweep (108 targets, exit 0), nor in 3 isolated --lib runs (1917/0 each), nor in the isolated rerun after occurrence 3. Three occurrences establish intermittence and a load correlation; none establishes cause
discriminating control for the next occurrence	capture the full process event stream and the child's exit disposition, not only the collected string — that is what separates "child never wrote" from "delivery or collection lost it", and the collected string cannot distinguish them however many times it is sampled. Cross-check against R4/R6's readiness family, which docs/active-work.md's 2026-08-06 entry already implicates
cross-reference	docs/active-work.md — 2026-08-06 occurrence, --features crdt, both the raw and canonical selectors, same fragment, read-before-write hypothesis
rival explanation not excluded	leaked pmacs --daemon processes, which the handoff names as a standing confound for any load-sensitive local red

U3 — the R7 selector again, fragments lost the same way U2's were

attach::tests::managed_retry_survives_transients_and_uses_the_successful_stream failed once during long-lines Stage 5's default-features sweep and passed on the recaptured rerun.

This is not recorded as an R7 match, and the distinction is the point. R7's job/flavor is --features crdt; this was default-features. More importantly its three required fragments (transient sequence must attach, Handshake(Io(, BrokenPipe / code: 32) are unverified, because the run's output was filtered to the failing test names before it was read. By this file's own matching rule that makes it a new incident, not a recurrence.

field	value
selector	-p pmacs-gpu attach::tests::managed_retry_survives_transients_and_uses_the_successful_stream
job / flavor	local (Linux), cargo test --workspace --no-fail-fast — default features, unlike R7
required fragments	none captured
status	new incident, not reproduced
what IS established	one failure; a recaptured rerun of the same command was green for this test, and the --features crdt sweep was green for it too. Per the rerun rule: intermittence only
what is NOT	whether it is R7's mechanism. It may well be. Nothing in hand shows it

The recurring mistake is mine, and it is now twice. U2 records the identical loss — "output was filtered to the FAILED line" — and I did it again here by piping a sweep through grep. The fix is mechanical: redirect a full sweep to a file and grep the file, never the live stream. A signature that is cheap to capture and impossible to reconstruct should never be traded for terminal brevity.

(Renumbered from U4/U5 to U6/U7 on the rebase onto 0857bf4: gate-protocol-build landed its own U4/U5 in #229, and git merged both files without a conflict, producing duplicate ids across four sites. The pre-rebase warning is retired here because it has been carried out.)

U6 — two wall-clock budget tests fail together in one lib-crdt step

Recorded during worker identity Stage 1 review round 2, 2026-08-09, in the same gate run that produced R7's third occurrence. Fragments were captured, so unlike U1–U3 this one is matchable — it is a U row because it has one occurrence and no mechanism, not because the evidence was lost.

field	value
selector	--lib --features crdt optimistic::tests::criterion_1_end_of_line_typing_completes_sub_frame_per_keystroke and editor::tests::composition_overhead_under_ten_percent, failing in the same run
job / flavor	local (Linux), scripts/gate step 04-lib-crdt, with sibling worktrees building concurrently
required fragments	criterion 1: per-keystroke orchestrator time + exceeds 1ms; and composition machinery added more than 10% overhead
status	FIVE OCCURRENCES — one on 2026-08-09 and FOUR on 2026-08-30, the first time this row has ever reproduced. Two of the four out of gate, two in gate (20260830T171941Z, T175657Z). Still no mechanism; see the block below
what IS established	both are wall-clock budget assertions — 1.264ms against a 1ms budget, and 1.297× against a 1.10× budget — so both are load-sensitive by construction. Both green in an isolated rerun of exactly those two selectors, and both green in the next full gate run of the same command (2105 passed)
what is NOT	whether the machine's concurrent load caused it. The confound is real (this machine runs one shared CARGO_TARGET_DIR and several worktrees) but was not measured, so it is a rival explanation, not a finding
rival explanation not excluded	a genuine regression in either path. Nothing in the observing diff touches the optimistic-echo orchestrator or the composition pipeline, but "my diff looks unrelated" is not evidence, and this row does not treat it as such

Second occurrence — the CRDT identity-undo lane, 2026-08-30, local (Linux). Both required fragments captured, both selectors, one run:

criterion 1: per-keystroke orchestrator time 1.343883ms exceeds 1ms
composition machinery added more than 10% overhead: 1.182

It reproduced on the immediately following run, which is new for this row — the first occurrence explicitly recorded "not reproduced".

Margins are recorded because U11 taught this registry what their absence costs. Here: 1.343883ms against a 1ms budget (1.34×) and 1.182× against a 1.10× budget; at the first occurrence, 1.264ms and 1.297×. So the composition margin grew and the keystroke margin grew, but neither by an order that separates load from regression. Both selectors were green in isolated single-selector reruns.

Fourth and fifth occurrences — both IN gate, both 04-lib-crdt, both the exact pair. 20260830T171941Z-3509751 (1.689259ms against 1ms; 1.592× against 1.10×) and 20260830T175657Z-3881334 (2.269247ms; 1.527×). Those two runs also redded other selectors in other steps; those clusters are U14 and U15 respectively, and only the 04-lib-crdt pair belongs to this row.

A DIRECTION CLAIM WAS MADE HERE AND IS WITHDRAWN, within the hour. This block first said the asymmetry "runs the OPPOSITE way to R7": both failures were out of gate, while 04-lib-crdt was green in all four of this lane's gate runs to that point (20260830T154827Z, T155621Z, T160242Z, T160824Z). The very next gate run redded 04-lib-crdt with this exact pair. So U6 fails both in and out of gate, the four green stages were a run of four and not a property, and the only honest reading is the one the first occurrence already gave: these are wall-clock budget assertions.

No mechanism is claimed. The load confound was unmeasured at the second and third occurrences and at the fourth; U15 records a single /proc/loadavg reading of 34.04 taken after the fifth, which makes severe unrelated load a measured presence rather than a measured cause — see that row for why the difference matters. What is worth having here is that this row is now reproducible under some condition, which the first occurrence could not say.

Two budget tests failing in one run and neither in the next is the signature worth matching, more than either name alone: a real regression in two unrelated subsystems at once is far less likely than one loaded machine. If a future run reds one of these without the other, that is a different incident and should be judged as one.

U7 — a different wall-clock render-budget test reds each sweep

Recorded during worker identity Stage 1 review round 3, 2026-08-09. Two consecutive scripts/gate runs of the same command, on the same tree, red on step 12-sweep with a different test each time — which is the signature, and it is a stronger one than any single selector.

field	value
selector	run 1: --test m8_2_acceptance dired_open_renders_10k_entries_under_200ms and --test m8_9_acceptance outline_5_level_100_entry_renders_within_100ms; run 2: --test dired_acceptance dired_renders_10k_entries_within_200ms
job / flavor	local (Linux), scripts/gate step 12-sweep (cargo test --workspace --no-fail-fast), load average 12.9 / 23.9 with sibling worktrees building concurrently
required fragments	must render within 200ms; took / open() (parse + render) took + spec budget is 100ms
status	new incident, three selectors, none reproduced
what IS established	all three are wall-clock render-budget assertions (224ms and 258ms against a 200ms budget; 114ms against a 100ms budget), so all three are load-sensitive by construction. Each was green in an isolated rerun of its own selector, no selector reds twice, and the third run of the same command on the same tree was green on all 13 steps (log 20260809T200907Z-2672209). The observing diff is two string literals, their doc comments and one test — it touches no render path at all, and cannot
what is NOT	that load caused it. The one-shared-CARGO_TARGET_DIR confound is real and again unmeasured, so it stays a rival explanation rather than a finding
relation to U6	same shape, different step and different tests: U6 is two budget tests in 04-lib-crdt failing together; this is three render-budget tests in 12-sweep failing one per run. Kept separate rather than merged, because merging would assert a shared mechanism nothing here shows

The rotating selector is the thing to match. A regression that moved between three unrelated render paths on an unchanged tree is far less likely than one loaded machine; a future run that reds the same one of these twice is a different incident and should be judged as one.

The retirements are not occurrences and do not close the log. R1 and R3 stay live, and each retired row keeps its signature so a later red matching one reopens it.

All four evidenced rows (R1–R4) are macOS. That is a property of these occurrences, not of the file: A1's job is GPU Render (headless), which runs on Ubuntu, and A2's job was never recorded. Nothing here is macOS-only by construction, and a future row from any job belongs in the same table.

The #214 occurrence is the strongest available evidence that these are not caused by the PRs they appeared on — that PR is docs-only and its tree is byte-identical to a green main. It is not evidence that any of them is harmless.

U4 — a_pty_resize_blanks_the_host_before_repainting, macOS both flavours, three occurrences

Surfaced on PR #229's CI; twice more on PR #231's.

The lua54 in this row's original title was wrong as a signature component, and matching on it would have missed two occurrences. The row was filed from #229's single lua54 red and recorded the flavour in the matching key. #231 then reddened the identical selector with the identical three fragments twice on luajit — so flavour is not part of this signature, and the row's own caution that "a deterministic defect can be Lua-flavour-specific" is now settled in the other direction: this one is not. Occurrence-keyed by suffix length, the three are 25 362 (#229, lua54), 25 222 (#231 attempt 1, luajit) and 25 054 (#231 attempt 2, luajit).

A fourth sighting of these fragments was NOT an occurrence and must not be counted as one. It came from a deliberate bite during this test's own development — the defect reintroduced on purpose (consumer ignores full_grid), 34 831 bytes, failing in 20.09 s. It earns its place here for what it proves instead: the genuine defect and these CI reds are signature-indistinguishable, same message class and same full-timeout duration, so the fragments alone can never tell a real resync failure from whatever this is.

field	value
selector	--test full_grid_resync_acceptance a_pty_resize_blanks_the_host_before_repainting
job / flavor	GitHub Actions, Test (macos-latest / lua54) and Test (macos-latest / luajit), macos-26-arm64. Flavour is not a matching key for this row
required fragments	FG-INV: the post-resize resync must blank the host · no CSI 2 J appeared in the · bytes emitted after the first painted frame
NOT fragments	the byte count and the :LINE suffix are occurrence-specific and must not be matched on — the count is the collected suffix length, which varies per run, and the line moves with the file
status	three occurrences on two branches; INTERMITTENT on #229 (passed on rerun), NOT observed to pass on #231 (0/2)
the #231 control experiment, and what it does and does not license	Five valid observations at #231's exact base 0190102 — run_attempt 1, 2, 3, 4 and 6 — all green on both macOS flavours, against #231's 0/2. Under an equal-rate model the chance both failures land on the two branch runs is 1/C(7,2) = 4.8%. Two things bound that number. First, attempt 5 was discarded because it reddened a different selector (U8) — so the base leg is 5/5 green for this signature and 5/6 overall, and "the base never fails" is not what was observed. Second, three unrelated macOS selectors reddening in one session is a background platform failure rate, and the equal-rate model the 4.8% assumes is exactly what such a rate violates. The branch side was never resampled: 5-vs-2 is an asymmetric experiment, and rerunning #231's failing job three more times at 4654b94 was the outstanding discriminator when it merged
why #231's diff is excluded	grepping its entire src/ diff for full_grid|resize|resync|Geometry|reconcile_panel_layout matches one import line and nothing else; all 721 changed lines are placement, dedication and commit-contract logic. From the other side, full_grid_resync_acceptance (191 lines) contains no panel, side-window, dedication, display or directory surface — grep for those matches only a comment about CSI 2 J. #231 merged on this reading over the statistical signal above, which is a judgement recorded here so that a fourth occurrence can revisit it rather than re-derive it
why #229's diff is excluded	#229 changes only scripts/gate, tests/gate_script_acceptance.rs and documentation — no src/, and the workflow never invokes scripts/gate. Decisively, full_grid_resync_acceptance runs before the changed gate suite, so even a cross-suite leaked-state path is not available. The luajit leg passing on the same commit is corroboration only — a deterministic defect can be Lua-flavour-specific, so that observation must not be used as a structural exclusion
what IS established	no blank was OBSERVED after the mark within the test's fixed 20-second deadline. The collected suffix was the entire post-mark output (suffix.len(), 25 362 bytes on this occurrence — not a capped window; only the displayed head is truncated to 400 bytes), and that head shows ordinary repaint traffic (ZQXMARKERQZ rows with SGR + CUP), so the host was painting
what is NOT	any mechanism. Whether the blank was never emitted, emitted after the deadline, or lost in transport is open — and "it never emitted the blank" is a claim this evidence does not support. The failing run's ~20 s duration is the fixed Duration::from_secs(20) timeout, so the spread against a fast passing run is mechanically determined and is not independent timing evidence
discriminating control — ASYMMETRIC, and only one direction concludes	the suffix is already complete, so "capture more bytes" is not the gap — arrival time is. Extending the deadline and recording whether CLEAR_ALL arrives, and at what offset: if it arrives, "emitted late" is established. If it does not, that establishes only "not observed by the longer deadline" — not "never emitted", because transport loss produces the same absence. Separating non-emission from transport loss needs producer-side emission evidence (did pmacs write the clear?) cross-checked against the collected stream; no deadline, however long, can do it alone

U5 — ctrl_c_during_reconnect_sleep_yields_clean_exit, macOS lua54, one occurrence

Surfaced on the rerun of PR #229's failed job — a different selector from U4, so by this file's matching rule it is a new incident, not U4 occurring twice.

field	value
selector	--test m5_8_acceptance ctrl_c_during_reconnect_sleep_yields_clean_exit
job / flavor	GitHub Actions, Test (macos-latest / lua54), rerun attempt 2
required fragments	Ctrl-C during reconnect sleep should produce a clean exit · ExitStatus { code: 1, signal: Some("Interrupt: 2") }
NOT a fragment	the :LINE suffix — occurrence-specific, moves with the file
status	one occurrence, unresolved
what IS established	Ctrl-C reached the process as SIGINT rather than as the raw-mode key event the test drives. That is all the exit status shows
what is NOT	whether injection preceded raw mode, raw mode was lost, or something else. Three mechanisms remain open and this fragment separates none of them
exclusion strength — WEAKER than U4's, deliberately	the changed gate_script_acceptance ran earlier in the same job, and it creates worktrees and directories. No leaked child or persistent signal-state mutation was observed, but "the diff touches no src/" is not the argument here that it is for U4, because cross-suite leaked state is a path reachability reasoning does not close
control 1 — CROSS-SUITE ATTRIBUTION, and asymmetric	run m5_8_acceptance alone on macOS lua54, without the gate suite ahead of it. A matching isolated RED proves the gate suite is not necessary for the failure. An isolated GREEN proves nothing beyond that run — the failure is intermittent, so absence under one run is not evidence of dependence. It also does not discriminate among the three mechanisms in either direction
control 2 — mechanism	observe readiness and raw-mode state at the moment of injection. Another isolated pass, however many times repeated, cannot separate "injected before raw mode" from "raw mode lost" from a third cause

U8 — acc28_child_input_and_the_c_c_escape_work_unchanged_in_a_panel, macOS luajit, one occurrence, fragments destroyed

Numbered U8 deliberately: U6 and U7 are reserved for the two wall-clock rows on worker-identity-stage1 (PR #232), which renumbered into that range when #229 took U4/U5. Taking U6 here would recreate the duplicate-id collision that rebase already produced once.

This row exists mostly as an admission. It surfaced on attempt 5 of a merge-base control at 0190102, and I reran the job before reading its log, which discarded it. GitHub keeps only the latest attempt's logs for a rerun job. So this is U2's original condition exactly — a selector with no fragments, unmatchable — and it was produced by the very mistake U3 is named for.

field	value
selector	--test bottom_panel_stage1_acceptance acc28_child_input_and_the_c_c_escape_work_unchanged_in_a_panel
job / flavor	GitHub Actions, Test (macos-latest / luajit), at base 0190102, control attempt 5
required fragments	NONE CAPTURED — destroyed by rerunning the job before reading its log. Recovery attempted via the jobs API and the attempt-scoped jobs endpoint; the log is gone
what IS established	it failed once (46 passed; 1 failed), panicking at tests/bottom_panel_stage1_acceptance.rs:2454, on the exact merge base — so it is not attributable to any open branch
what is NOT	everything else. Without the assertion text this cannot be matched against a future occurrence, which is the whole purpose of a row here
why it matters anyway	it is the third distinct macOS selector to red in one session, after U4 (full_grid_resync) and U5 (ctrl_c_during_reconnect). Three unrelated selectors failing on the macOS legs suggests a background failure rate on that platform rather than three independent test bugs — and that materially affects any equal-rate reasoning about which branch a failure "landed on"
next occurrence	read the log BEFORE rerunning anything. That is U3's stated lesson and this row is its fourth violation

U9 — a PTY test and a budget test red together in one 11-sweep, with an in-run control

Recorded on the destination-capture merge tree, 2026-08-10, in the gate run that was meant to clear PR #231.

This row's value is its control, not its selectors. U6 and U7 could only compare a red run against a different run. Here both selectors ran green inside the same gate invocation, minutes earlier, on the same tree and machine — 03-lib (1928 passed, 0 failed) and 04-lib-crdt (2113 passed, 0 failed) — and then failed in 11-sweep. So this is not deterministic on this tree; causation and any rate effect are unresolved.

The original wording here was "whatever this is, it is not the tree", which this file's own rerun rule forbids: a same-tree green establishes intermittence only, and a tree can raise an intermittent failure rate without making it deterministic. Same-tree greens cannot exonerate the tree. Corrected rather than deleted, because the wrong claim is the one a later reader would otherwise reach for.

field	value
selector	--lib process::tests::m6_1_pty_canonical_mode_keeps_kernel_echo and editor::tests::composition_overhead_under_ten_percent, failing in the same 11-sweep step
job / flavor	local (Linux), scripts/gate step 11-sweep (cargo test --workspace --no-fail-fast -- --skip basedpyright), fresh per-lane target dir, no sibling worktrees building
required fragments	canonical mode should leave echo enabled (no `-echo` flag); stty -a output was: "" and composition machinery added more than 10% overhead
NOT fragments	the measured numbers (1.613, single=191935 ns, dispatch=309602 ns) and every :LINE suffix — occurrence-specific
status	one occurrence; INTERMITTENT — the identical sweep command on the same tree was green (118 targets, 1928 passed, exit 0)
what IS established	intermittence, with the strongest available exclusion of the tree: green in two earlier steps of the same run, green isolated afterwards (2 passed, 1.70 s), green on a full sweep rerun. Both assertions are timing-sensitive by construction — one reads collected child output within a deadline, the other measures wall-clock composition overhead (observed 1.613× against a 1.10× budget; 61.3% dispatch and 124.6% realistic overhead)
what is NOT	cause, and the load confound is partially measured but NOT controlled. The failing sweep ran inside a full gate; the green rerun started at load average 1.98 with the 5-minute figure still at 8.03 from that gate. Different conditions is not a measurement of the mechanism, and this row does not treat it as one
the structural difference worth testing next	cargo test --workspace runs many test binaries concurrently; --lib runs one. That is a difference in kind between the passing steps and the failing one, not merely a difference in load average — and it is the first candidate this family has had that is checkable rather than atmospheric. Discriminating control: rerun the sweep with test-binary concurrency pinned to 1, and separately run the --lib binary alone under synthetic load. A red under synthetic load at low sweep concurrency implicates load; a red at high concurrency and low load implicates the concurrency itself
relation to U2 — a NEAR MISS, do not match it there	the PTY fragment is U2's exact family (stty -a output was: ""), but U2's selector field names only m6_1_pty_raw_mode_disables_kernel_echo. U2's occurrence 2 saw raw and canonical fail together; here canonical redded alone and raw passed, which U2's evidence has never shown. It is recorded here rather than folded into U2 so that the "canonical alone" case stays visible
relation to U6 — its own instruction, honoured	composition_overhead_under_ten_percent is one of U6's two selectors, and U6 says plainly: "If a future run reds one of these without the other, that is a different incident and should be judged as one." It redded without criterion_1_end_of_line_typing…, in a different step, at a far larger margin (1.613× here against U6's 1.297×). Judged as a different incident, as instructed
what this row does NOT assert	that the two selectors share a mechanism. They failed together once; they belong to different subsystems; and U7 already refused this exact merge for U6. The co-failure inside one step with an in-run green control is the signature — not either name, and not a shared cause

U10 — the budget red ROTATES between two consecutive runs of one commit

Recorded during §5b review round 4, 2026-08-20. Two consecutive scripts/gate runs at the same commit with a clean worktree verified at both ends of each run — 70b334d, git status --porcelain empty before and after, both times. Each run was 15/16 green. Each red is a wall-clock budget assertion in a different step, and each is green in the other run.

field	value
run A	log 20260820T155616Z-359755, step 13-sweep red: dired_open_renders_10k_entries_under_200ms, 263.961465ms against 200ms (32% over). Step 15-sweep-crdt green
run B	log 20260820T160806Z-578046, step 15-sweep-crdt red: optimistic::tests::criterion_1_end_of_line_typing_completes_sub_frame_per_keystroke, 1.044609ms against 1ms (4.5% over), 2148 passed. Step 13-sweep green
required fragments	M8.2 spec: 10K entries must render within 200ms; took / criterion 1: per-keystroke orchestrator time + exceeds 1ms
status	two occurrences, neither reproduced; every selector green on rerun
isolated controls	both green in an isolated rerun of their own selector at load average 9.34, through the gate's target directory — the same control shape U6 and U7 each used
what IS established	the tree is excluded, as strongly as this repository can exclude it. Not "the diff touches no render path" — the same commit produced a pass and a fail of each row, with the worktree verified clean at both ends of both runs. Neither failing path is touched by the branch under test (src/optimistic.rs, tests/m8_2_acceptance.rs and the dired paths are all absent from git diff --name-only githubsucks/main...HEAD)
what is NOT	that load caused it. Load was not sampled during either failing step. A 76.63 reading exists for run A but was taken later in the same run, while step 15 was compiling; run B began at 23.46. Neither figure measures the failing moment, and this row does not pretend otherwise
rival CLOSED since U7	the shared CARGO_TARGET_DIR confound U7 left "real and again unmeasured". Each worktree now gets its own gate target directory (pmacs-mapping-gen-8cb089c8); no sibling shared it. Excluded for these occurrences only — it says nothing about U7's
machine context, NOT a cause	150 leaked pmacs daemons were live throughout, 1.9 GB resident, oldest ~6.3 days — the standing "Leaked daemons — NEEDS A LANE" item. Their instantaneous CPU sampled at ~0%. Recorded because it is true of the machine, not because anything here shows it mattered
relation to U7 — its escalation rule, honoured and CUT BOTH WAYS	U7 says "a future run that reds the same one of these twice is a different incident and should be judged as one." Run A redded dired_open_renders_10k_entries_under_200ms, which was U7's run-1 selector, so that selector has now redded twice, 11 days apart — filed here rather than appended to U7, as instructed. But within this pair the selector ROTATED, which is U7's own core signature, and run B's selector is U6's. The repeat and the rotation are both true, and this row asserts neither as the finding
relation to U6	run B's selector is one of U6's two, redding without composition_overhead_under_ten_percent. U6 instructs that one-without-the-other is a different incident; honoured here
what this row does NOT assert	a shared mechanism between the two rows, or any mechanism at all. The signature is the rotation across an identical commit — not either name

Why this family keeps recurring, stated plainly. Every row in it is a wall-clock budget asserted inside a workspace-wide parallel test run. cargo test --workspace starts many test binaries at once, so each budget competes with the rest of the sweep in every run, including the ones that pass. A 4.5% overshoot on a 1ms budget is not a signal about the code. U9 already named the discriminating control — pin test-binary concurrency to 1 and separately load a lone --lib binary — and it remains unrun. Until it runs, this family should not consume another review round.

Widening a budget is not the fix, and R1 already rejected it.

U11 — dispatch_parse_round_trips_a_rust_source_file, macOS lua54, one occurrence, green on rerun

Recorded from PR #242, 2026-08-20, on head 61f0faf — the head that merged as 47b5463. Deferred to post-merge absorption by decision, so that no docs commit would invalidate that PR's head-exact gate evidence; the fragments lived in PR #242's comment in the interim, because the raw job log is machine-local and not portable evidence.

field	value
selector	--lib async_runtime::tests::dispatch_parse_round_trips_a_rust_source_file
job / flavor	Test (macos-latest / lua54), run 32393462318
required fragment	trivial parse should be fast, panicking at src/async_runtime.rs:3328
counts	1960 passed; 1 failed; 3 ignored, finished in 64.49s
attempt 1	job 96504773333 — failure
attempt 2, rerun	job 96511228345 — success
status	one occurrence, not reproduced
THE MARGIN IS UNRECOVERABLE	the assertion is assert!(duration_ms < 100, "trivial parse should be fast") — a 100ms wall-clock budget on a 30-byte source, with duration_ms omitted from the message. The red cannot say whether it missed by 1ms or by 900ms, and no future occurrence can be compared against this one. This is a property of the assertion, not of the observation
what IS established	non-determinism across these observations, and nothing more. Four passes of the same selector on the exact head in local gate 20260820T163107Z-879828 — one each in 03-lib, 04-lib-crdt, 13-sweep, 15-sweep-crdt. Two Test (macos-latest / luajit) greens on the same commit and OS, jobs 96504773331 and 96511275402. src/async_runtime.rs byte-identical to main, blob 9310ce3fca8c5fd8ebd39a68c29ad6985e256049 on both sides — not merely an empty diff
what is NOT	environmental cause, or harmlessness. The luajit greens narrow the red below "macOS at this commit"; they do not explain it. A green rerun establishes intermittence only
relation to U10	not U10. Different selector, different fragment, different subsystem, and remote rather than local. Filed separately for the same reason U10 was filed apart from U6 and U7

A recurrence is not another instance of this row. Because the margin was never captured, a second red cannot be compared with the first, so it owes a merge-base control before any claim is made about the tree.

The one-line fix that would make this family diagnosable — include the measured duration_ms in the assertion message — is owed its own small lane. It was deliberately kept out of #242, whose diff does not touch src/async_runtime.rs.

U12 — U9's shape in 04-lib-crdt: a budget test and a PTY test, together

Recorded during the panel-replay lane's gate, 2026-08-21, on head 6142acc. Filed rather than folded into U6 or U9, because both of those tell it to be: U6 says one of its selectors redding without the other is a different incident, and this is composition_overhead_under_ten_percent alone again; U9 is that same shape but in 11-sweep with a different PTY selector.

field	value
selectors	--lib --features crdt editor::tests::composition_overhead_under_ten_percent and process::tests::setsid_escapee_is_not_reaped_and_teardown_reclaims_readers, failing in the same step
job / step	local (Linux), scripts/gate step 04-lib-crdt, log 20260821T122852Z-2922631
required fragments	composition machinery added more than 10% overhead / live runtime probe
observed	1.247× against the 1.10× budget (single 192493 ns, dispatch 240130 ns); the PTY row failed at src/process.rs:5155, where active_reader_probe found no live reader within the 2s Started window
status	one occurrence, both selectors green on isolated rerun
the rest of the run	15 of 16 stages green, including sweep, m4, gpu, diff-check and all eight touched acceptance suites
what IS established	both are timing-dependent by construction — one a wall-clock ratio, the other a 2-second liveness window — and each passed alone immediately afterwards. src/process.rs is NOT touched by the observing branch at all; src/editor.rs is, but only in the panel-replay paths, not in composition
what is NOT	that load caused it. Load was 11.04 at the gate's start and 27.79 (5-minute) at its end, with two foreign python processes at ~2 cores throughout and an apt/dpkg install shortly before. Those are conditions, not a measurement of the mechanism, and the run was knowingly taken on a machine that was quieter but not quiet
relation to U6	its selector, alone again, in U6's own step. U6's instruction to judge that separately is honoured for the second time — see U9, which did the same
relation to U9	the same budget-plus-PTY co-failure, in 04-lib-crdt rather than 11-sweep, with setsid_escapee… where U9 had m6_1_pty_raw_mode…

This family has now produced U6, U9, U10 and U12, and the discriminating control U9 named is STILL UNRUN: pin test-binary concurrency to 1, and separately load a lone --lib binary. Four incidents is enough evidence that the family will keep costing review rounds until someone runs it.

U14 — FOUR selectors red in ONE gate run, across three stages

Recorded on the CRDT identity-undo lane, 2026-08-30, local (Linux), scripts/gate log 20260830T171941Z-3509751. The co-occurrence is the signature, as it is for U6, U9 and U12: four selectors in four unrelated subsystems — the async runtime, the optimistic-echo orchestrator, editor composition, and the LSP dispatch seam — failing in one run is less likely than one loaded machine, and no single selector reds twice within the run. U6's own row treats its two selectors as unrelated subsystems, so the 04-lib-crdt pair is two of the four here, not one.

field	value
selectors	four. 03-lib: async_runtime::tests::grep_supersede_cancels_predecessor_within_50ms. 04-lib-crdt: optimistic::tests::criterion_1_end_of_line_typing_completes_sub_frame_per_keystroke and editor::tests::composition_overhead_under_ten_percent (U6's pair — see below). 07-sweep: lsp_dispatch_seams_acceptance::acc34_purge_reaches_a_server_that_is_in_no_attachment
job / flavor	local (Linux), one scripts/gate run, three different steps
required fragments	grep supersede did not cancel within 50ms + an elapsed: value; criterion 1: per-keystroke orchestrator time + exceeds 1ms; composition machinery added more than 10% overhead; is not ready for requests (state: initializing)
status	new incident, ONE occurrence
what IS established	all four fragments captured from the durable stage logs. Margins: 52.44341ms against 50ms (4.9% over); 1.689259ms against 1ms; 1.592× against 1.10×. The 07-sweep failure is not a budget — an LSP server was asked for a request while still initializing
what is NOT	any shared mechanism, and any load measurement: no /proc/loadavg reading was taken during or after this run. Three stages, four subsystems, and one of the four selectors is a readiness race rather than a clock
the observing tree	the lane's revision-5 commits: an enumeration in a #[cfg(test)] predicate and documentation. It touches async_runtime, optimistic, editor and the LSP dispatch seam not at all

An earlier version of this row claimed a SECOND occurrence, and that was a matching-rule violation. The run 40 minutes later (20260830T175657Z-3881334) redded a different selector set — full_buffer_summary_flatten_scales_on_large_grammar_file and dired_renders_10k_entries_within_200ms in place of grep_supersede… and acc34_purge…. Under "How a row matches" above, the exact selectors must match; a rotated set is a new incident. It is now U15, and the 04-lib-crdt pair the two runs do share is recorded where it belongs, as U6's own occurrence.

Relation to R1, and it is NOT a match. The 03-lib failure carries R1's required fragment supersede did not cancel within 50ms, but R1's selector is supersede_cancels_in_flight_job_within_50ms and this is grep_supersede_cancels_predecessor_within_50ms — a different test. This registry matches on selector and fragments, and U6's own instruction ("one without the other is a different incident") points the same way. Recorded as a sibling, not an occurrence.

One thing the sibling shows for free, and R1 should have it. R1's row records that its assertion "still omits its measurement — started.elapsed() is in hand at the panic and the message reports none of it, so this occurrence's margin is as unrecoverable as every prior one's." The sibling test already reports it: (elapsed: 52.44341ms), which is how the 4.9% margin above is known at all. The measurement-design question R1 defers to the async-runtime lane is untouched by this — but the cheap half of it is demonstrably already written, next door in the same module.

Reruns: all four selectors green in isolation — grep_supersede… 1 passed, U6's two 1 passed each, and the whole lsp_dispatch_seams_acceptance binary 15 passed. Per this file's rerun rule that establishes intermittence only; it exonerates nothing, and in particular it does not show the tree is innocent, only that the failures do not reproduce alone.

U15 — a rotated multi-red cluster, with a contemporaneous load reading

Recorded on the CRDT identity-undo lane, 2026-08-30, local (Linux), scripts/gate log 20260830T175657Z-3881334 — 40 minutes after U14's run, on the same tree. A new incident rather than a U14 occurrence, because the selectors rotated and this file matches on the exact set.

field	value
selectors	03-lib (default features): editor::tests::composition_overhead_under_ten_percent and semantic_render::tests::full_buffer_summary_flatten_scales_on_large_grammar_file. 07-sweep: dired_acceptance::dired_renders_10k_entries_within_200ms
job / flavor	local (Linux), one scripts/gate run, steps 03-lib and 07-sweep
required fragments	composition machinery added more than 10% overhead; full-buffer flatten took + the event sweep must stay ~linear; 10K entries must render within 200ms; took
status	new incident, one occurrence
what IS established	margins 1.450× against 1.10×, 1.274901136s against a ~linear expectation, and 221.459827ms against 200ms (10.7% over). /proc/loadavg read immediately after the run: 34.04 38.45 26.29, with the CPU saturated by unrelated lean processes — nothing this session started, and no cargo, rustc or scripts/gate process of mine left running
what is NOT	that the load caused any of it. See below

Two selectors here belong to other rows and are deliberately NOT claimed as their occurrences. composition_overhead_under_ten_percent is one of U6's two, and it redded in 03-lib without its partner and under default features, not U6's 04-lib-crdt/crdt flavor — U6's own instruction is that one-without-the-other is a different incident. dired_renders_10k_entries_within_200ms is one of U7's three, and this is the second time that same selector has redded — U7's own instruction is that a repeat of one selector is a different incident. Both instructions are honoured rather than quoted and ignored.

(The same run's 04-lib-crdt step redded U6's pair together, in U6's flavor and step. That IS a U6 occurrence and is recorded there.)

What the load number establishes, stated at its real strength — and it is NOT this registry's first. U7 has carried a load average since 2026-08-09 (12.9 / 23.9, in its job/flavor field); what U7 records as unmeasured is something narrower, whether the shared CARGO_TARGET_DIR and its sibling worktree builds produced that load. An earlier version of this block said U6 and U7 had both wanted a number since 2026-08-09. Half of that was wrong.

What 34.04 is: the first contemporaneous load reading for a U6 occurrence — U6's row has said since 2026-08-09 that its confound "was not measured" — and a new reading alongside a recurring U7 selector, not U7's first. That makes load a measured confound present contemporaneously with a multi-red run. It does not make it the cause, and three specific things stop it short:

• the reading is a single point, taken after the fact. No /proc/loadavg was captured during U14's run or the two out-of-gate runs, so there is no series to correlate margins against;
• the margins are not monotonic. composition_overhead_under_ten_percent went 1.182× → 1.592× → 1.527× across the three runs, and in this run alone it reports 1.450× in 03-lib and 1.527× in 04-lib-crdt. Only criterion_1's three points rise monotonically (1.343883ms, 1.689259ms, 2.269247ms), and three points with one load reading is not a dose-response;
• an earlier version of this write-up said "a load average of 34 explains it without any help." That overstates it. Severe unrelated load was present; whether it produced these particular margins is unmeasured.

What it does change: for U6, "one loaded machine" stops being a hypothesis offered in good faith and becomes a quantity on the record — a second data point for the correlation U7's reading started. It retires nothing: U15 itself, U6, U7, U14 and R1 all keep their dispositions, and the budgets remain wall-clock assertions whose measurement design nobody has defended.

Reruns: green in isolation — composition_overhead… 1 passed, and the dired_acceptance selector had already been shown green in isolation by U7. Intermittence only, per the rerun rule.

U16 — a git invocation finds its working directory deleted

Recorded on the CRDT identity-undo lane, 2026-08-31, local (Linux), scripts/gate log 20260831T083021Z-272257, step 07-sweep. Not a budget row — nothing here is a clock. It is the only row in this file that arrives with a named candidate mechanism inside the test suite, which is why it is worth more than its one occurrence.

field	value
selector	--lib packages::fetcher::tests::cache_survives_across_fetcher_instances
job / flavor	local (Linux), scripts/gate step 07-sweep (cargo test --workspace --no-fail-fast)
required fragments	Unable to read current working directory: No such file or directory + remote did not send all necessary objects
status	new incident, one occurrence, not reproduced
what IS established	the fragments, captured from the durable stage log at src/packages/fetcher.rs:929. 1989 passed; 1 failed. The test spawns git against a file:// remote in a temp dir
what is NOT	that the mechanism below is what happened. It is a candidate with a citation, not a demonstrated chain
the observing tree	the lane's docs-only commit. It touches src/packages/ not at all

The candidate mechanism, and it is specific. src/file_io.rs:434 — bare_filename_saves_in_cwd — calls std::env::set_current_dir(dir.path()), which mutates process-global state, points it at a TempDir, and lets that TempDir drop at end of test. The libtest harness runs tests in parallel threads within one process, so during that window every other test in the binary shares the mutated cwd, and after the drop that cwd is a deleted directory. fatal: Unable to read current working directory is exactly what a process with a deleted cwd gets from git.

The test restores the cwd before its assertions, deliberately and with a comment saying so — the hazard is not the restore, it is that the window exists at all, and no amount of care inside one test closes a window that is process-wide.

What would settle it, and neither has been run:

• run the two selectors concurrently in a tight loop until the failure reproduces, which converts the candidate into a demonstration;
• or make the hazard structural rather than probabilistic — a serial guard around every set_current_dir test, or removing the process-global mutation from bare_filename_saves_in_cwd entirely (save_atomic could take the directory rather than inheriting it).

Reruns: green in three isolated runs of the selector, and in EIGHT full parallel cargo test --lib runs (1990 passed each). Per this file's rerun rule that establishes intermittence only — and here it also says the window is narrow, not that it is absent.

Not folded into U14 or U15. Different selector, different fragments, different step, and a different kind of failure: those are wall-clock budgets under load, this is a race over process-global state. U14's acc34_purge readiness failure is the nearest relative in kind, and even that is a different mechanism.

U17 — a supersede race lost the OTHER way, on main, single-threaded

Surfaced 2026-08-31 by the merge-base control dispatched for R6's second occurrence — so it is a red on main at aae5b35, on no branch at all. No PR run can show this; it took a workflow_dispatch on main to see it.

field	value
selector	--test m8_1_acceptance read_dir_supersede_cancels_in_flight_predecessor
job / flavor	GitHub Actions, Test (crdt): cargo test --all-targets --no-default-features --features luajit,crdt -- --test-threads=1
required fragments	first read_dir must be superseded; got ok
status	new incident, one occurrence, ON main
what IS established	9 passed; 1 failed, panic at tests/m8_1_acceptance.rs:278, run 33375945966 job 99437344558, head aae5b35
what is NOT	any mechanism. The candidate below is a reading of the assertion, not a diagnosis
attribution	none available, and none needed — aae5b35 is main. There is no observing branch to suspect

It fails the OPPOSITE way to R1 and R5, and that is the interesting part. Both of those are deadline failures — a cancellation that did not arrive in time (supersede did not cancel within 50ms, async pump deadline exceeded). This one reports got ok: the first read_dir completed successfully instead of being cancelled. The supersede did not arrive late; it arrived after there was nothing left to supersede.

Candidate mechanism, stated as one. The job runs --test-threads=1. A test that dispatches a job and then supersedes it "in flight" depends on the predecessor still being in flight; with no other test competing for the runtime, the predecessor is at its fastest, and the window in which it can be superseded is at its narrowest. That is a reading of the assertion and the flag together — it is not a diagnosis, and nothing here rules out a real supersede defect.

Worth noting for U9. U9's still-unrun discriminating control is "pin test-binary concurrency to 1". This job already does that, in CI, on every run. That does not run U9's control — different binary, different selectors — but it does mean the single-threaded condition is not hypothetical in this project, and a row now exists where it may be load-bearing in the opposite direction from every budget row here.

Not R1 and not R5, on this file's own matching rule: different selector, different module, different assertion. R5's row draws exactly this distinction against R1 and the same reasoning applies again — sharing a subject is not sharing a signature.

No rerun was performed. U3's lesson and R6's "never a green rerun" disposition both apply, and there is no branch here whose merge this would gate.

U13 — gate prune-reporting row receives empty child stdout in sweep

Recorded during PR #244 review, 2026-08-29, on signed head 756c2b8. The first six gate stages were green; 07-sweep produced this one red; 08-diff-check remained green.

field	value
selector	--test gate_script_acceptance skipped_directories_are_reported_with_a_reason
job / step	local (Linux), scripts/gate step 07-sweep, log 20260829T171606Z-1087848
required fragments	skipped_directories_are_reported_with_a_reason + the unmarked directory must be named with its reason; output was: followed by empty output
status	one occurrence; exact selector and the full 36-test binary both green on immediate rerun
what IS established	the test observed empty stdout from its scripts/gate --prune child even though its fixture had created an unmarked lookalike which a successful prune must name. The row discards the child's stderr and success status (let (out, _, _)), so the durable failure cannot distinguish wrong successful output from a refused or failed child invocation
what is NOT	any mechanism. Another row in the same test binary mutates shared git-worktree metadata, but concurrent execution is only a candidate; this occurrence did not capture the child status or stderr needed to support it
why this branch is excluded	the lane changes two assertion-message strings and three docs. scripts/gate and tests/gate_script_acceptance.rs are byte-identical to the base; the async_runtime edit is inside its unit-test module, and the other Rust edit belongs to a different integration-test binary
next occurrence	preserve the child success status and stderr in the assertion before rerunning. A green rerun establishes intermittence only; it cannot reconstruct why stdout was empty