clay-borg/history/260801-cb-wp-0006-log.md

CB-WP-0006 — delivery log

Per-task delivery notes, moved out of the workplan when it crossed the ~400-line loadability limit for the third time in this project. The workplan holds the plan; this holds what happened. T08 draws on both.

CB-WP-0006-T01

Delivered. am6_throughput_clears_the_spec_target in games/ground/src/lib.rs — a test, not a bench. Best of 3 samples of 50,000 applied events each.

Measured on bnt-lap001 2026-07-31: 341,280 ev/s in debug (3.4× the target), ~2.4–3.1M in release (~24–30×). The spec target holds even in an unoptimized build, so the gate needed no cfg split and runs in the ordinary make test.

The trap was avoided by construction, not by intention. The threshold is the spec value 100_000, untouched; the constant carries a comment saying lowering it requires an ADR; and the failure message repeats that, states the measured headroom, and names the reference figures — so a future agent hitting a red AM-6 is told not to tune it, in the place they will actually be reading. Robustness comes from best-of-N, not from a lower bar: a throughput floor asks "is this machine capable", so transient load should not fail the build.

Two positive controls in the test itself: a run that applied fewer than 50,000 events, or measured zero elapsed time, fails rather than scoring as infinite throughput.

Verified: make mutation-check --row AM-6 → red, via a property mutation (4,000 black_box iterations injected into GroundState::fold, the hot path) rather than a threshold tweak — raising the target would only prove the comparison runs.

And the FA class is now gated. mutation-check rows gained an expect field: the mutant's output must contain the row's stated failure string, or the verdict is WRONG-REASON, not red. Without it, a mutation that merely failed to compile would credit its row with an assertion it does not have. Verified by pointing expect at a string the verifier never prints and confirming the verdict flips. This is remedy (2) from the CB-WP-0005 retrospective, built one task earlier than T08 planned because the class it guards is the newest and the most dangerous.

M-D1-MUT: 4 → 5 of 14.

CB-WP-0006-T02

Delivered — but the two rows resolved differently, and the difference is the point.

AM-2 is instrumented and enforced. tools/size-metrics.py + make size-metrics, in make all:

AM-2: 27.2 LOC/rule  [ok  target <= 40]  (1.47x headroom)
      1,575 code lines before the first #[cfg(test)] / 58 numbered rules

Tests are excluded because AM-2 asks what a rule costs, not how much it is exercised — lib.rs is ~18% test code and including it would have flattered the number. Verified red by a property mutation: ~800 lines of filler injected into the impl, pushing the ratio past 40. expect is the precise failure signature FAIL target <= 40, not the row name, which would have matched passing output too.

AM-3 is BLOCKED, not uninstrumented — and this is a finding, not a deferral. The row measures "LOC to express the CB-RES-0001 synthetic game on our kernel" against a boardgame.io baseline of ~36 LOC for a declarative 3p commit/reveal game object. That artifact has never been built: games/ contains only ground, and benches/synthetic.rs drives GROUND rather than defining a synthetic game.

Measuring GROUND's 1,575 impl lines against a 36-line synthetic game object would compare two different games and call the difference a D1 result. So the tool ships the measurement mechanism — a marker-delimited // AM-3:BEGIN / // AM-3:END region, self-tested — and reports the row blocked, naming the missing artifact. A number here would have been worse than a blank.

It therefore stays unmutatable and still counts against M-D1-MUT, per ADR-0005 §1: a row that cannot fail asserts nothing, however good the reason. Resolving it needs an artifact, not a metric tweak — carried forward, not silently dropped.

M-D1-MUT: 5 → 6 of 14.

CB-WP-0006-T03

Delivered — tools/runtime-metrics.py. One passes, one breaches.

AM-9: met, and comfortably. 13.4 MB peak RSS against a ≤64 MB target, 4.8× headroom. Gated and in make all (--fast, ~1 s). The row that CB-EV-0001 called "very unlikely to bind" was right — but it is now measured rather than assumed, and verified red by a property mutation (a 300 MB allocation in the workload).

AM-5: BREACHED MET — the first reading was wrong.

Corrected 2026-08-01 (during T04). T03 reported 87.0 s / 61.3 s and called AM-5 a 45% breach. It is not. Re-measured on a quiet machine with the fixed instrument:

load before measuring: 0.14 per CPU over 8 CPUs — quiet
dev toolchain (default features)         37.3 s  [ok  target <= 60 s]
  best of 3: 37.3, 42.9, 46.2  (spread 1.24x)
shipped runtime (--no-default-features)  41.2 s  [ok  target <= 60 s]
  best of 3: 41.2, 50.8, 54.2  (spread 1.32x)

1.6× headroom, comfortably met. The 87.0 s was measured while the machine was busy running mutation-check and cargo builds — a timing measurement under contention measures the contention. That is the same error class as AM-6's, committed two tasks later in the same session, by the same author, in the row immediately after the one where it was diagnosed.

The instrument now (a) reads /proc load average and refuses to measure above 0.5 per CPU, and (b) takes the best of 3 — best, not worst, because a build-time ceiling asks "can this machine do it in 60 s", the mirror of AM-6's best-of-N for a throughput floor. It also warns when the spread exceeds 1.25×, which fired on the shipped-runtime samples: consecutive clean builds degrade (37.3 → 46.2), so even a quiet machine is not a uniform one.

The original, now-withdrawn finding follows for the record:

dev toolchain (default features)             87.0 s  [FAIL target <= 60 s]
shipped runtime (--no-default-features)      61.3 s  [FAIL target <= 60 s]

The tool reports and exits 0, because the spec says the row is not gated (and on the corrected number there is nothing to escalate anyway). Gating it is a spec change and needs an ADR; a tool that promotes itself is how a target starts binding without anyone deciding it should. So AM-5 stays unmutatable — it cannot fail while the spec declares it ungated, which is the accurate reason. The escalation is withdrawn: there is no breach to decide about.

A build profile was investigated anyway while the breach was believed real, and the findings stand on their own: 51 compile units, 174 s of CPU work compressed into ~54 s wall, parallelism only 3.2× on 8 cores because proc-macro2 → syn → serde_derive → serde_core is a ~22 s serial chain. lto = "thin" costs ~6 s (55.8 → 49.4 s mean) and is the only real lever; pinning ppv-lite86 down to drop zerocopy (the largest single unit, 21.8 s) makes it worse — 23 → 25 crates, because the older version pulls zerocopy-derive. Recorded here rather than acted on: with 1.6× headroom there is nothing to buy.

The measurement had a real bug, found by cross-validation. getrusage(RUSAGE_CHILDREN) is a high-water mark across every reaped child, so it attributed cargo's memory to the workload and reported 38.2 MB for a run that used 12.3 MB — a 3× over-report. Fixed with os.wait4, which returns that specific child's rusage. The self-test now cross-checks against /usr/bin/time -v (13.4 vs 12.4 MB), which is the only reason the bug was visible at all: the wrong number was plausible, passed its target, and would have been published.

That is FA in the measurement layer rather than the mutation layer — an instrument confidently reporting a number it had not earned.

M-D1-MUT: 6 → 7 of 14.

CB-WP-0006-T04

Delivered: withdrawn from the acceptance table, retained as a diagnostic. specs/GameKernel.md §5a carries the argument.

The ratio has no monotone better direction. INTENT's rule is own the semantics; assimilate the implementation. Rising can mean owning semantics properly, or reimplementing what should have been assimilated. Falling can mean good leverage, or dependency bloat. A target requires knowing which way is better, and this metric does not.

It is also redundant: AM-4a/AM-4b bound the denominator and AM-2 bounds own-source density per rule. AM-4c is a ratio of two already-targeted quantities.

Measured at withdrawal: 1,426 own lines per 100k third-party (shipped), 1,107 (dev). make dep-weight now prints both, labelled diagnostic, not targeted — it was never actually reported before.

M-D1-MUT keeps AM-4c in its denominator, deliberately, and says so in the output. Dropping it would move the score 7/14 → 7/13 without enforcing anything: a score improved by deleting the question.

A T01 correction found here

The AM-6 gate failed inside make all at 38,753 ev/s against 341,280 measured in isolation — a 9× drop. cargo test runs test binaries and threads concurrently, so a throughput assertion inside a parallel harness measures contention, not throughput. T01's measurement was valid and its gate placement was not.

Fixed by running the measurement only where it is valid — #[ignore], plus make am6 in release with --test-threads=1, now 2.0M ev/s, 20.2× headroom — and not by lowering the target, which T01 explicitly forbade and which would have reproduced the defect being fixed. My first attempt did drift that way (a debug "sanity floor" of 50,000) and was backed out: a second threshold is still a second chance to tune.

And the mutation went SURVIVED on the first run after the move — 4,000 black_box iterations were calibrated against debug's 3.4× headroom and are invisible against release's 20×. Raised to 100,000; back to red. A weak mutation is not a fixed property of a row: it can become weak when the row's measurement conditions change.

M-D1-MUT: 7 of 14 (unchanged — AM-4c was always going to stay uncounted; what changed is that the reason is now correct and recorded).