From 039e4191ddc0bf0f6a063aa36e95ea014fb7d2f4 Mon Sep 17 00:00:00 2001 From: tegwick Date: Sat, 1 Aug 2026 13:40:58 +0200 Subject: [PATCH] =?UTF-8?q?CB-WP-0006=20T09:=20retrospective=20=E2=80=94?= =?UTF-8?q?=20a=20real=20instrument,=20hardened=20three=20times?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The question was whether M-D1-MUT is a real instrument or a name-counter with extra steps, given that writing a weak mutation is as easy as writing a strong one. It is real, but only because it was hardened three times in one pass. Five controls now stand between a mutation and a red verdict — the mutation must apply, the baseline must be green, the tree must be restored and verified, the failure must match a stated reason, and that stated reason must be absent from passing output — and every one of them exists because its failure actually occurred. The last is the sharpest: the FA guard needed a guard, because my first AM-2 expect was "AM-2", which the passing report contains. Generalizable: an instrument that measures whether other instruments work needs more controls than the instruments it measures. M-D1-MUT carries five; dep-weight and rule-coverage carry one each. That asymmetry is the cost of a meta-instrument, and a project adding one should budget for it. A worse failure mode than CB-WP-0005 predicted: a mutation can become weak without anyone touching it. AM-6's went SURVIVED when T04 moved its gate from debug to release — nothing about the row, the mutation or the code changed, only the headroom. Mutation strength is coupled to measurement conditions, so a mutation is not a write-once artifact. CB-WP-0005 T08's stronger remedy — mutations written by someone other than the author — was NOT tested and should not be assumed unnecessary: EXPECT-VACUOUS covers the cheap failure, not the expensive one AM-6 demonstrated. The "removes the manual path" test is settled as a predictor of cost, not of worth. mutation-check fails it outright and produced six defects nothing else would have found. Prediction error collapsed: 4-5x, then 2.5x, now small — because this pass predicted per task, as a mechanism, with the alternative named. Both branches are outcomes someone must defend, so the prediction cannot be dodged. AM-3 and AM-4c took the second branch and are better resolved for it than if a number had been forced. No InnerLoop change. v1.4's mutation requirement is one pass old and changing it before a second use would be the invention-in-isolation INTENT warns about — the same argument used to amend K14 four hours earlier. Named next candidate: specs/SessionShape.md. SS-01..SS-05 have been stated since CB-WP-0003 and none has ever been enforced. This pass ran at 2.5x the context ceiling its own spec sets and nothing said a word. CB-WP-0006 status -> done, 9/9. Co-Authored-By: Claude Opus 5 --- ...0801-instrument-the-table-retrospective.md | 141 ++++++++++++++++++ workplans/CB-WP-0006-instrument-the-table.md | 45 +++++- 2 files changed, 183 insertions(+), 3 deletions(-) create mode 100644 history/260801-instrument-the-table-retrospective.md diff --git a/history/260801-instrument-the-table-retrospective.md b/history/260801-instrument-the-table-retrospective.md new file mode 100644 index 0000000..8717da1 --- /dev/null +++ b/history/260801-instrument-the-table-retrospective.md @@ -0,0 +1,141 @@ +# 2026-08-01 — retrospective: is a weak mutation the new grep? + +CB-WP-0006 T09. The pass instrumented AM-2, AM-6, AM-9 and AM-11, +implemented K10, K11 and K18, amended K14, withdrew AM-4c, and measured +itself in [CB-EV-0005](../evidence/CB-EV-0005-instrument-the-table.md). + +## The question this task inherited + +> **M-D1-MUT does not remove a manual path — writing a weak mutation is +> exactly as easy as writing a strong one, and the harness cannot tell the +> difference. Is it a real instrument, or a name-counter with extra +> steps?** + +**It is a real instrument — but only because it was hardened three times +in one pass, and it would have been a name-counter without that.** + +## What it took to make one mutation trustworthy + +The naive idea — *invert the property, require red* — is not enough. Five +controls now stand between a mutation and a `red` verdict, and **every one +of them exists because its failure actually occurred**: + +| control | verdict | the failure that motivated it | +|---|---|---| +| the mutation must apply | `HARNESS-BROKEN` | a stale find-string would score the baseline as the mutant | +| the baseline must be green first | `inconclusive` | "mutant red" proves nothing if it was already red | +| the tree must be restored, and verified | — | every later row runs against a corrupted tree | +| the failure must match a **stated reason** | `WRONG-REASON` | a mutation that merely fails to compile would credit the row | +| the stated reason must be **absent from passing output** | `EXPECT-VACUOUS` | my first AM-2 `expect` was `"AM-2"`, which the passing report contains | + +That last one is the sharpest. It means the FA guard needed a guard, and +the failure it prevents is one I committed on the guard's second use. + +> **The generalizable finding: an instrument that measures whether other +> instruments work needs more controls than the instruments it measures.** +> M-D1-MUT carries five; `dep-weight` and `rule-coverage` carry one each. +> That asymmetry is not overhead, it is the cost of a meta-instrument, and +> a project that adds one should budget for it. + +## The failure mode that is still open + +CB-WP-0005 predicted a weak mutation would be *written* weak. This pass +found a worse case: **a mutation can become weak without anyone touching +it.** + +AM-6's 4,000 `black_box` iterations were calibrated against debug's 3.4× +headroom. When T04 moved the gate to release — correctly, because the +debug measurement was invalid — the same mutation became invisible against +20× headroom and the row went `SURVIVED`. Nothing about the row, the +mutation, or the code changed. + +The harness caught it, so the loop is not blind here. But it means +**mutation strength is coupled to measurement conditions**, and a mutation +is not a write-once artifact. That is a standing maintenance cost, and it +is the honest answer to "is this cheaper than it looks": no. + +**CB-WP-0005 T08's stronger remedy — mutations written by someone other +than the author of the assertion — was not tested.** The adversarial +reviewer wrote none of these. `EXPECT-VACUOUS` covers the cheap failure +(a guard that matches everything); it does **not** cover the expensive one +(a mutation too weak to trip a real threshold), which is exactly what +AM-6 demonstrated. That remedy remains untested and should not be assumed +unnecessary. + +## Did the "removes the manual path" test predict which gates work? + +No, and this pass is the counter-example that settles it. + +`mutation-check` fails that test outright — `grep` is still one keystroke +away, and a weak mutation is as easy to write as a strong one. It also +produced **six defects nothing else would have found**: AM-6 measuring +contention, AM-5's 61% measurement error, RSS over-reported 3×, K10's +first round trip not reproducing, the bench workload existing twice, and +two spec copies going stale. + +CB-WP-0004 T06 said tooling recovers capacity only where it removes the +manual path. **That is a predictor of whether a gate saves money, not of +whether it is worth having** — a correction first stated in CB-WP-0005 T08 +and now supported by a full pass. `mutation-check` costs money and earns +its place on findings. + +## The cost result refutes the pass + +**Mechanical share rose to 50%** — the highest recorded, above the 38% +baseline that motivated CB-WP-0004. Mean context **493,486** against a +200,000 target, up from 315,170. + +This is not a tooling regression, and the distinction matters: environment +setup and task closes are still at **zero**, two passes on. It is the +*other* half of T06's mechanism arriving in force. Text patching (45 +turns, $13.79) and orientation (19 turns, $10.97) never had their manual +path removed, and a code-heavy pass is precisely where that spends. + +So the mechanism holds in both directions, which is the strongest evidence +it is real: what was removed stayed removed; what was merely improved +stayed expensive, and got worse under load. + +## Prediction discipline, third outing + +| pass | prediction | measured | error | +|---|---|---|---| +| CB-WP-0004 | 25–30 points recovered | 6 | 4–5× | +| CB-WP-0005 | ≥10 of 14 rows | 4 | 2.5× | +| **CB-WP-0006** | **9 per-task outcomes** | **7 met, 2 restated with an argument** | **small** | + +The first two were aggregate predictions with a confidence label. This +pass predicted **per task, as a mechanism, with the alternative named** — +"instrument it, *or* restate it with an argument" — and the error +collapsed. + +That is CB-WP-0004 T06's recommendation working. It also shows why: +a per-task prediction with a named alternative cannot be dodged, because +*both* branches are outcomes someone has to defend. AM-3 and AM-4c both +took the second branch, and both are better resolved than if a number had +been forced. + +## What the loop should change + +**Nothing in InnerLoop this pass.** v1.4's mutation requirement was added +by CB-WP-0005 and this pass is its first full exercise; changing it again +before a second use would be the invention-in-isolation INTENT warns +about, and the same argument used to amend K14 four hours ago. + +**The named next candidate is `specs/SessionShape.md`.** SS-01…SS-05 have +been stated since CB-WP-0003 and **none has ever been enforced** — they +are the only acceptance-adjacent numbers in this project with no gate at +all. Measured this pass: mean context 493,486 (target 200,000), p90 +594,888 (target 300,000), batching well under target. A pass whose entire +subject was ungated numbers ran at 2.5× the context ceiling its own spec +sets, and nothing said a word. + +## Open, not closed + +- **AM-3 blocked** on an artifact that has never been built — a minimal + synthetic game on our kernel. Needs a deliverable, not a metric tweak. +- **AM-7 and AM-8 remain PARTIAL**: no code computes AM-7's throughput + ratio, and nothing enforces AM-8's N=10. +- **`CommitWindow` is provisional with a delete-by date of 2026-12-31.** +- **The kernel gate binds 2026-08-31** — 18/18 today, so it binds green. +- **SessionShape is ungated**, and is now the largest measured gap. +- **The chaos roll is at declaration 3 of 12** (T04 rolled d4=2). diff --git a/workplans/CB-WP-0006-instrument-the-table.md b/workplans/CB-WP-0006-instrument-the-table.md index 0de81d9..ac1bd0e 100644 --- a/workplans/CB-WP-0006-instrument-the-table.md +++ b/workplans/CB-WP-0006-instrument-the-table.md @@ -1,7 +1,7 @@ --- id: CB-WP-0006 title: "Instrument the acceptance table, then implement what it exposes" -status: in_progress +status: done state_hub_workstream_id: "8a6327cc-fd5c-4e2c-a29b-b437c27d1e71" --- @@ -222,14 +222,23 @@ right for K18. ```task id: CB-WP-0006-T08 -status: todo +status: done priority: high state_hub_task_id: "1d4455c3-c642-47d8-916b-ab35bc512207" ``` -Commit `evidence/CB-EV-0004`. The baseline is **4 of 14**, committed and +Commit `evidence/CB-EV-0005` — **numbering corrected**, CB-EV-0004 was +already CB-WP-0005's. The baseline is **4 of 14**, committed and reproducible via `make mutation-check`. +**Measured — [CB-EV-0005](../evidence/CB-EV-0005-instrument-the-table.md). +4 of 14 → 8 of 14** (8 of 10 enforceable; the 14 stays the headline and +AM-4c stays in it on purpose). Kernel link 15/18 → **18/18**, names only. +One row regressed to `SURVIVED` and was caught. **0 vacuous expects** +across 14 rows — test 3 is now mechanical, via a new `EXPECT-VACUOUS` +verdict. **The cost result refutes the pass:** mechanical share rose to +**50%**, the highest recorded. + Three tests, all reported: 1. **Did the enforced count rise, per row?** Against the per-task @@ -268,3 +277,33 @@ the latter, say so and propose what would actually bind — the candidate being that the mutation must be written by someone other than the author of the assertion, which is the adversarial-review principle applied one level down. + +**Answered — [260801-instrument-the-table-retrospective.md](../history/260801-instrument-the-table-retrospective.md).** + +**A real instrument — but only because it was hardened three times in one +pass.** Five controls now stand between a mutation and a `red` verdict, +and every one exists because its failure actually occurred. The +generalizable finding: **an instrument that measures whether other +instruments work needs more controls than the instruments it measures** — +M-D1-MUT carries five, `dep-weight` and `rule-coverage` carry one each. + +**A worse failure mode than predicted:** a mutation can become weak +**without anyone touching it**. AM-6's went `SURVIVED` when T04 moved its +gate from debug to release. Mutation strength is coupled to measurement +conditions, so a mutation is not a write-once artifact. CB-WP-0005 T08's +stronger remedy — mutations written by someone other than the author — +was **not tested** and should not be assumed unnecessary: `EXPECT-VACUOUS` +covers the cheap failure, not the expensive one AM-6 demonstrated. + +**Prediction error collapsed** — 4–5×, then 2.5×, now small — because this +pass predicted **per task, as a mechanism, with the alternative named**. +Both branches are outcomes someone must defend, so the prediction cannot +be dodged; AM-3 and AM-4c took the second branch and are better resolved +for it. + +**No InnerLoop change.** v1.4's mutation requirement is one pass old and +changing it before a second use would be the invention-in-isolation INTENT +warns about — the same argument used to amend K14. **The named next +candidate is `specs/SessionShape.md`**: SS-01…SS-05 have never been +enforced, and this pass ran at **2.5× the context ceiling its own spec +sets** without anything saying a word.