clay-borg/workplans/CB-WP-0006-instrument-the-table.md

id	kind	title	status	state_hub_workstream_id
CB-WP-0006	mixed	Instrument the acceptance table, then implement what it exposes	done	8a6327cc-fd5c-4e2c-a29b-b437c27d1e71

Purpose

CB-WP-0005 T02 measured M-D1-MUT for the first time:

  M-D1-MUT: 4/14 rows enforced
    PARTIAL       2      (AM-7, AM-8 — some clauses live, some inert)
    unmutatable   8      (no property to invert)

4 of 14, against a predicted 10 of 14. The prediction was wrong by 2.5×, and wrong about what as well as how much: CB-RES-0004 diagnosed three absent kernel rules, and the measurement found that more than half the acceptance table has no instrument behind it at all.

CB-WP-0005 Phase C was deferred before starting on that basis (T02's stop condition, maintainer decision 2026-07-31). It was scoped to five rules — K9, K10, K11, K14, K18 — which does not address the eight.

This workplan is scoped to what was measured rather than what was predicted. Phase A instruments the unmeasured rows; Phase B implements the kernel work inherited from CB-WP-0005 T04–T06. That order is the whole point: the previous pass built a fix before its instrument existed, and the instrument then contradicted the fix's premise.

Per InnerLoop §Step 4, no target moves in the commit that measures it.

Phase A — instrument the rows that measure nothing

Task: AM-6 — assert the throughput target

id: CB-WP-0006-T01
status: done
priority: high
state_hub_task_id: "a4513794-2f5f-480c-be30-56658711796f"

The sharpest single finding of CB-WP-0005. Nothing in the workspace compares any number to 100,000 events/s — the project's headline throughput claim, reported as met, 16.5×. The Criterion bench emits throughput; the only asserts in synthetic.rs are the stress-gate shape and the events-per-round pin.

Deliver a standing assertion — a test, not a bench — that measures applied events/s on the synthetic workload and fails below the AM-6 target.

The trap, stated up front: a timing assertion in CI is flaky by nature, and the usual response is to loosen it until it never fires, which would reproduce exactly the defect being fixed. So the threshold is pinned well below the measured 1.65M/s (AM-6 asks for 100k), the assertion states its own headroom in the failure message, and a loosening requires an ADR. A gate tuned until it cannot fire is a gate that counts names.

Verified by: make mutation-check --row AM-6 goes from unmutatable to red.

Delivered — see the delivery log.

Task: AM-2, AM-3 — instrument the size metrics

id: CB-WP-0006-T02
status: done
priority: medium
state_hub_task_id: "d1572a4f-46e5-49dd-b1ec-7c371a780bb7"

AM-2 (≤40 spec lines per rule) and AM-3 (≤50 LOC for the synthetic workload) are both unmutatable for the same reason: make loc prints line counts and nothing divides, compares, or gates.

AM-2 is the anti-gaming pair for AM-1 — 100% rule coverage means nothing if the rules are trivially small — so an uninstrumented AM-2 leaves AM-1 gameable, which is the specific risk MetricsAndScenarios §1 names when it introduces M-D1-SPL.

AM-3 depends on K18 (benches driven from scenario files); if K18 resolves toward amending the spec rather than implementing it, AM-3 must be restated or withdrawn with an argument rather than left unmeasured.

Delivered — see the delivery log.

Task: AM-5, AM-9 — measure or withdraw, but stop leaving them blank

id: CB-WP-0006-T03
status: done
priority: medium
state_hub_task_id: "6c84a220-cab3-40f1-b35f-b8df79106f6e"

AM-5 (clean build ≤60 s) is recorded not gated — and not recorded either. AM-9 (peak RSS ≤64 MB) is declared "very unlikely to bind", which CB-EV-0001 itself calls out as an unmeasured judgment call.

Both are cheap to measure: one time around a clean build, one /usr/bin/time -v around the 100k-event run. Or withdraw them with an argument, which is a legitimate outcome and possibly the right one for AM-5 on a machine-dependent number. What is not legitimate is a third pass leaving them blank while the scoreboard reports elsewhere.

Delivered — see the delivery log.

Task: AM-4c — target it or drop it

id: CB-WP-0006-T04
status: done
priority: low
state_hub_task_id: "a2571314-4c02-41cf-9473-96d3ae2d7b2b"

reported, not targeted, so there is no property to invert and it counts against M-D1-MUT by ADR-0005 §1.

Two honest options, and the task must pick one with an argument: give it a threshold (making it enforceable), or remove it from the acceptance table and keep it as a reported diagnostic. A row in an acceptance table that cannot fail is decoration, and this pass has learned to say so.

Note the incentive: ADR-0005 already predicts own-source growth from the kernel work in Phase B, so AM-4c will move against us. Setting its threshold after seeing that movement would be the retarget InnerLoop §Step 4 forbids — so it is set here, before Phase B, or not at all.

Delivered — see the delivery log.

Phase B — the kernel work inherited from CB-WP-0005

These three were written in CB-WP-0005 Phase C and cancelled unstarted. Their analysis lives here, next to the work — CB-WP-0005 keeps only a forward pointer, so there is one copy. The normative controls are in ADR-0005 §6.

Task: K9 and K11 — durable log, LogStore port, real conformance suite

id: CB-WP-0006-T05
status: done
priority: high
state_hub_task_id: "2a357dbf-3861-499d-a12e-f7682b7332f6"

K9 — the acceptance property is snapshot at seq N + events N+1..M ≡ genesis fold, hash-compared, on GroundState. What exists instead is one test round-tripping a BTreeMap<String, u8> with EventSeq(17) as a literal: no game aggregate, no events applied, no from-genesis comparison. Mutation-proven — making Snapshot::take discard its EventSeq leaves the test green, so the half of K9 that says "+ the EventId it includes" is unverified. Snapshot has no callers outside its own test.

K11 — append-only, length-prefixed, versioned framing, with a truncated tail detected; the operative clause is detection, so truncate-by-one- byte and corrupt-length-prefix rejection are required, not optional. Reimplemented rather than assimilated (ADR-0005 §2): ~100 lines against a format Kafka and EventStore converged on independently, adding no dependency, charged to AM-4a (shipped runtime, 1.5% headroom). The LogStore port with a shared fn conformance<S: LogStore>(…), retro-fitted to KernelRng, is what finally earns AM-11 — currently downgraded to unmet because the pair exists and the suite does not.

Verified by: make mutation-check --row AM-11 goes from unmutatable to red.

Task: K10 — the replay bundle and --replay

id: CB-WP-0006-T06
status: done
priority: high
state_hub_task_id: "d459444d-41be-40c5-9101-7a8420b42fb6"

INTENT design decision 8 of 10, unimplemented. cb-sim has no flag parsing at all, so --replay has nowhere to go yet.

This is not "a directory of four files" — the D2 correction the adversarial review forced. scenario.rs creates an EventLog, appends to it and never reads it: the one production instantiation of the K11 log is a write-only sink. Pass carries the end state, not an initial snapshot, and failures are a formatted String, not structured expected-vs-actual. Plumb the log out of execute, capture an initial snapshot, restructure RunOutcome::Failed. The writer is dev-only behind the scenarios feature and is charged to AM-4b (9.4% headroom), not AM-4a.

All four controls from ADR-0005 §6 are required verbatim, including the two the reviewer supplied: truncate-by-one-byte rejection, and a mutated-seed control so the round-trip is capable of failing.

Fixing this is also what lets AM-7's withdrawn hash-identical clause be re-earned, since a real replay is what the clause was always about.

Task: K14 and K18 — implement, or amend the spec and say why

id: CB-WP-0006-T07
status: done
priority: medium
state_hub_task_id: "d76ad893-520b-44bd-9b77-07dbfb651ce3"

Inherited from CB-WP-0005 T06. CommitWindow has zero non-test users; the bench never touches ScenarioFile. Either wire them up or amend the rules with a recorded argument. Deleting a rule to make a gate green is forbidden; deleting one with an argument is legitimate and probably right for K18.

Phase C — measure, and answer the question this pass inherited

Task: control loop — M-D1-MUT before and after

id: CB-WP-0006-T08
status: done
priority: high
state_hub_task_id: "1d4455c3-c642-47d8-916b-ab35bc512207"

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. 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 predictions above, unmet reported as unmet.
2. Did any row regress from red to SURVIVED? The four currently enforced rows are the ones with something to lose.
3. Were the new mutations strong? CB-WP-0005 T02 wrote two no-op mutations on its first attempt, either of which would have published a false accusation against working code. Every mutation added by this pass must be shown to fail for the stated reason — record how that was checked.

Task: retrospective — is a weak mutation the new grep?

id: CB-WP-0006-T09
status: done
priority: medium
state_hub_task_id: "4f291d5a-90f0-4f1f-bcaf-7ec28856bfcf"

The question CB-WP-0005 T08 raised and this pass is positioned to answer.

CB-WP-0004 concluded that tooling recovers capacity only where it removes the manual path. 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. CB-WP-0005 produced two no-op mutations on its first attempt, so the failure mode is demonstrated, not hypothetical.

And it fails in the more dangerous direction: a weak mutation does not merely miss a defect, it indicts working code. A false SURVIVED sends the next pass to fix something that is not broken.

So: is M-D1-MUT a real instrument, or a name-counter with extra steps? If 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.

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.