clay-borg/workplans/CB-WP-0015-the-inert-clauses.md

id	kind	title	status
CB-WP-0015	product	The two inert clauses: AM-7 scaling and AM-8 N=10	todo

Purpose

structural tier  S   (acceptance rows measure the product, not how we
                      work — `bench-test` is in gates.toml's
                      not_control_gates list, so the M trigger about the
                      loop's own constraints does not fire)
chaos            d4 = 2  → no override
declared tier    S

Declaration 10 of 12. Tier S: one provenance paragraph in the commit message, no survey and no ADR. Steps 4–5 are not skipped.

The two clauses nobody has touched in seven passes

tools/mutation-check.py has carried these two verdicts since CB-WP-0005, in its own words:

AM-7 scaling >= 0.9x — "no code computes the ratio of throughput @100k to @5k or compares it to 0.9; Criterion reports both and nothing relates them."

AM-8 N=10 same-seed replays — "the runner executes each scenario TWICE (K8), not ten times; the spec says N=10. The double-run is live and the count is not."

Both have been reported honestly every run and neither has been worked. AM-7 moved 1/3 → 2/3 in CB-WP-0006; AM-8 has been 1/2 since it was instrumented. They are the last two PARTIAL rows in the acceptance table.

And the test is named for the property it does not check. replay_100k_events_is_linear_and_fast folds a log at 10,000 and at 100,000 events, prints a throughput for each, and asserts each is under five seconds independently. The two numbers are computed, printed, and never compared. At 10,000 the five-second assertion is close to vacuous on its own.

This is the same family as the last four passes' central findings, one step further along: not a claim nobody checked, but a number measured and then not used. The name asserts linearity; the body does not.

The risk this pass has to face rather than route around

AM-7's clause was written against a measured boardgame.io defect — throughput halving as history doubled. Our aggregate may not be able to exhibit that defect at all: if GROUND state is bounded and fold does not scan history, replay is O(n) by construction and the ratio is ~1.0 no matter what.

If so, the honest result is not a green row. It is that AM-7's scaling clause measures something our design makes structurally impossible to violate, and a clause that cannot fail is the unmutatable verdict this project already counts against itself (ADR-0005 §1). Making it green by asserting a tautology would be the worse outcome of the two.

So this task may end in an amendment rather than an assertion. Decide it on what the mutation says, not on which outcome closes more rows.

Task: make AM-7's scaling clause live, or show it cannot be

id: CB-WP-0015-T01
status: todo
priority: high

Compute the ratio the spec names — throughput folding a growing log at 100k events against the same at 5k — and assert it against 0.9.

The measurement has a known trap, and it is documented in this repo already. AM-6's assertion first ran inside make all and read 38,753 ev/s against 341,280 in isolation, a 9× error, because cargo test runs binaries and threads concurrently: "a throughput assertion inside a parallel harness measures contention, not throughput." A ratio of two timings taken under varying contention is worse than a single reading, not better — the noise does not cancel, it multiplies. Whatever this lands in must run where AM-6 runs (release, --test-threads=1, its own target) or not be gated at all.

Required, and the pass fails without them:

• The mutation must go red for the stated reason. Slowing fold in proportion to log length — not by a constant, which AM-6 already catches — must break the ratio and nothing else.
• A positive control on the ratio itself. A harness that measured the same size twice would report 1.0 and look excellent. Prove the two legs are different sizes and that the denominator is the small one.
• State the variance. One reading of a ratio is not a measurement. Report the spread across samples, and if the spread crosses 0.9 then the threshold is not gateable at this sample count — say that instead of taking the best reading.

If the ratio is ~1.0 because nothing in the design can make it otherwise, write that up and amend the row, following the precedent AM-4c set in specs/GameKernel.md §5a — the argument goes in the spec, at tier S, with the row retained in the denominator.

Task: settle AM-8's N, at 10 or at 2, with the argument

id: CB-WP-0015-T02
status: todo
priority: high

The spec says ten same-seed replays; the runner does two. Close the gap in whichever direction survives the argument — and the argument is the deliverable here, not the number.

Ten is doing real work only if the failure it hunts is probabilistic. A deterministic divergence — a seeded RNG threaded wrong, a fold that depends on insertion order — fails on run two exactly as reliably as on run ten. A divergence from ambient nondeterminism — hash iteration order, pointer-dependent hashing, thread scheduling — appears with some probability per run, and there ten runs are eight more chances than two.

So: which does AM-8 exist to catch, and what does the repo already do about the other? clippy.toml denies HashMap/HashSet and make check runs -D warnings, which is AM-8's other clause and already live. If the lint removes the probabilistic class structurally, ten runs are buying repetitions of a check that cannot fail — and that costs time on every make all.

Whichever way it goes, the mutation must still go red: the existing seed-perturbation mutation is the control, and if raising or lowering N does not change what that mutation catches, that is itself the finding.

Do not amend the spec silently. If N becomes 2, GameKernel §5 says so and says why, in the same shape as §5a.

Task: evidence, and what the acceptance table now claims

id: CB-WP-0015-T03
status: todo
priority: high

evidence/CB-EV-0013-*.md.

Report the mutation table before and after, and be exact about the denominator — CB-EV-0005 established that a score improved by deleting the question is not an improvement, and this pass can improve its score two ways, one of which is deleting a question.

Also due here:

• Quote CB-WP-0014's final cost, not this pass's. The rule adopted in CB-EV-0012. CB-WP-0014 closed at $7.47 / 34 responses = 0.220.
• CB-EV-0009's standing prediction is now testable for the first time. It predicted a pass opening above the SH-1 hard line would cost more than 0.123 per response. CB-WP-0014 opened above the line and cost 0.220. Report it as one data point, and say plainly that one point past a threshold is not a confirmation — the prediction has a direction and no control.
• Whether the acceptance table still has a PARTIAL row, and if the answer is no, whether that is because both clauses became live or because one became a spec amendment.