jc: corrective slice — ω sign erasure + R² scale dependence (both P1, reproduced); C2 audit

.claude/board/EPIPHANIES.md

@@ -1,10 +1,41 @@
+## 2026-08-04 — E-THE-CROSS-IDENTITY-SUITE-INHERITED-MY-BLIND-SPOT-1 — five independent cross-checks all passed while ω was inflated 3× and R² was unit-dependent
+
+**Status:** FINDING (both defects reproduced, fixed, regression-tested). **Confidence:** High — measured before and after. Found by external review of merged code, not by the suite that shipped with it.
+
+**What the suite could not see.** D-KIA-C1b's headline discipline was that every new estimator is cross-checked against an *independently computed* quantity — φ vs `pearson`, R² vs `pearson²`, η² vs R² on a dummy, η² vs `t²/(t²+df)`, ω vs α. All five held. Two P1 defects were live the whole time:
+
+- **ω erased loading signs.** The triad identity returns `λ_i²`, so the positive root was taken for every item; ω uses `(Σλ)²`, where a negatively-keyed item must *subtract*. On a signed fixture: **0.75 reported against a true 0.25**.
+- **R² was unit-dependent.** Normal equations on raw columns plus an *absolute* `1e-12` pivot cutoff — a statement about units, not rank. An exact linear fit at 1e-8 magnitude returned **`None`**; the identical relationship at unit scale returned **1.0**.
+
+**Why the cross-identities were blind, and this is the transferable part.** A cross-identity checks that two computations *agree*, and agreement is only informative over the region the fixtures span. **Every ω fixture I wrote had all-positive loadings; every R² fixture was O(1).** The identities were not weak — they were evaluated at a single point of a space with unexplored dimensions. `ω = α` under tau-equivalence is true whether or not signs are handled, because tau-equivalent items are all positively keyed. `R² = pearson²` is true at any scale the guard happens to admit.
+
+**So the rule is not "add more cross-checks."** It is: **name the parameter space of the estimator, then confirm each dimension is actually varied by some fixture.** For these two the dimensions were obvious in hindsight and absent in fact — *sign* of the loadings, *magnitude* of the predictors. A cross-identity suite inherits the blind spots of the fixtures it runs on, and inherits them silently, because every check reports green.
+
+**The concrete practice, cheap enough to be worth doing:** for any numeric estimator, before claiming coverage, list the transformations under which the result should be **invariant** (affine rescaling, global sign flip, permutation, unit change) and the ones under which it should **change**, and write one test for each. Those tests found both defects immediately once written, and one of them — `omega_is_invariant_to_a_global_sign_flip` — is now the thing that proves the *fix* introduced no new bias.
+
+**Second lesson, on the earlier self-congratulation.** #887's write-up said the doc examples caught two defects the unit tests missed, and drew the moral that readable examples sample the degenerate case. True — but incomplete, and I stopped there. The fuller statement is that **fixtures are a sample of the input space and every suite is only as good as that sample's coverage**; doc examples happened to cover *one* uncovered corner. Treating that as the lesson rather than as an instance is why the next two corners stayed uncovered until someone else looked.
+
+## 2026-08-04 — E-A-STATISTIC-THAT-RETURNS-ZERO-FOR-UNDEFINED-CANNOT-FAIL-VISIBLY-1 — consolidating a utility does nothing while 56 copies with a *weaker contract* survive
+
+**Status:** FINDING (measured workspace-wide at `a9f813c`). **Confidence:** High — a grep census, reproducible. Filed as `TD-STATS-DEGENERACY-CONTRACT-DIVERGENCE`; **not paid** in this pass.
+
+**The census.** Hand-rolled `pearson` / `spearman` / `cronbach_alpha` definitions outside `jc`: **47 returning bare `f64`, 9 returning bare `f32`, 3 returning `Option`** — and all three `Option`s are `jc::reliability`'s own. At least one copy (`perturbation-sim/src/stats.rs:11`) returns **`0.0`** for ragged input, for `n < 2`, *and* for zero variance.
+
+**Why `0.0` is the sharp end.** It is byte-identical to a real "perfectly uncorrelated" result. A caller cannot distinguish *"r = 0 because these variables are unrelated"* — a finding — from *"r = 0 because I handed you a constant vector"* — a bug in the caller. The undefined case is not merely unreported; it is **disguised as the most publishable value in the range**. Several copies also omit the non-finite guard, so a `NaN` input yields a finite-looking number rather than a rejection.
+
+**This is the falsifiability rule one level down.** That rule governs guards that cannot fire; this is a *measurement* that cannot fail. Both defects share the shape: **the artifact has no way to say "no".** A statistic returning `Option` can; a statistic returning `f64` has spent its entire output range on answers and kept none for "I don't know".
+
+**The second-order finding, which is the transferable one.** `reliability.rs`'s module header states that callers rolled their own "**until now**" — presenting consolidation as accomplished. Measurement says consolidation reached the *four new* callers and **zero of the 56 pre-existing definitions**. The doc was written from the intent of the change rather than from the state of the tree, and nothing forced a re-read. **Generalisation: a "we consolidated X" claim is an inventory claim, and an inventory claim decays silently** — it is true on the day it is written and drifts every day after, because new duplicates cost nothing to add. Such claims need either a census in the same breath or the word *aspiration*. Cf. `CLAUDE.md` § falsifiability, "a doc-comment claim is not a behaviour".
+
+**Consequence, deliberately narrow:** the debt is recorded with a risk-ordered paydown (silent-`0.0` copies first, missing-non-finite-guard second, plain `f64` third, `f32` hot paths last or never) and explicitly **not** auto-fixable — each migration is a decision about what that call site should do when the estimate is undefined, which is exactly the information the current code discards.
+
 ## 2026-08-04 — E-EXACT-FIT-IS-WHERE-ABSOLUTE-ZERO-GUARDS-BREAK-1 — a misfit guard written as `x < 0.0` rejects the PERFECT case, and the doc example is what caught it
 
 **Status:** FINDING (two measured defects, both fixed in the same commit). **Confidence:** High — reproduced, fixed, and each now carries a regression test. Code: `crates/jc/src/stats.rs` (D-KIA-C1b).
 
 **The defect.** `omega_total` guards against a **Heywood case** — estimated common variance exceeding an item's total variance, `ψ_i = σ_ii − λ_i² < 0`, which means the single-factor model does not fit. Written as `if psi < 0.0 { return None }`, that guard **rejects the best-fitting input there is**: items that are exact multiples of one factor have `ψ = 0` in real arithmetic and land a few ulps *either side* of zero in f64. The perfect model was reported as misfit. Fix: a tolerance **relative to the item's own variance** (`1e-9 · max(|σ_ii|, 1)`), then clamp — only a violation larger than rounding is a real one.
 
-**The generalisation, which is the reusable part.** A guard testing a quantity that is **exactly zero at the ideal** must never use an absolute `< 0` (or `== 0`) comparison. The failure is invisible on ordinary noisy inputs — where `ψ` is comfortably positive — and appears **only on the cleanest possible data**, which is exactly the case a doc example or a smoke test reaches for. Sibling instances to check for: any `variance < 0`, `residual < 0`, `determinant == 0`, or `SS_within <= 0` test in a fitting path.
+**The generalisation, which is the reusable part** *(narrowed 2026-08-04 after external review — the first statement was too broad).* The rule is about **theoretically non-negative FITTED quantities**: a residual variance, an estimated error term, a sum of squared residuals. Such a quantity must distinguish **rounding-scale negativity** (accept, clamp) from a **material model violation** (reject) using a SCALE-AWARE tolerance — never a bare `< 0`. It is **not** a licence to stop testing zero: a zero determinant may genuinely mean singularity, zero within-group variance genuinely leaves `F` undefined, and zero variance genuinely leaves `t` undefined. Those are real degeneracies to reject, not rounding to absorb. The earlier phrasing — *"a quantity exactly zero at the ideal must never use an absolute comparison"*, with determinants and `SS_within` listed as siblings — invited exactly that misreading. The failure is invisible on ordinary noisy inputs — where `ψ` is comfortably positive — and appears **only on the cleanest possible data**, which is exactly the case a doc example or a smoke test reaches for. Sibling instances to check for: any `variance < 0`, `residual < 0`, `determinant == 0`, or `SS_within <= 0` test in a fitting path.
 
 **The second defect, same commit, different lesson.** The `multiple_r_squared` doc example used predictors `a` and `a + 1` and asserted `R² = 1`. It returned `None` — **correctly**: the design carries an intercept, so `[1, a, a+1]` is rank-deficient. Here the *example* was wrong and the code was right. A duplicated column is the collinearity everyone remembers; **collinearity with the intercept is the one that gets written by accident**, because the two predictor columns are visibly different.
 

.claude/board/STATUS_BOARD.md

@@ -6,12 +6,14 @@ Plan: `.claude/plans/kanban-64k-inverted-awareness-v1.md` (operator anchors a/b;
 |---|---|---|---|---|
 | D-KIA-0 | jc capability map + dichotomous-statistics decision note (phi/KR-20/kappa naming; Spearman dropped at view 2) | lance-graph | Queued | plan W0 |
 | D-KIA-A1 | ⊘ RESCOPED 2026-08-04 (E-ACTOR-IS-NOT-THE-PHASE-PATH-1): #879 is the complete phase-progression path; KanbanActor has no assigned architectural responsibility (legacy compatibility code). SHIPPED: held-owner reschedule/wake. OPEN: run_cycle drained-writer retry guard; missing-owner counter in cognitive_pass | lance-graph | Queued | plan W1 |
-| D-KIA-C1b | jc additive-only extension: kappa + McDonald's omega + r-family effect size (R/R-squared, eta-squared = explained variance) + t-test (t/df/p) + a named phi wrapper. Cohen's d explicitly OUT — calculated separately if ever wanted. HARD CONSTRAINT: additive only — pearson/spearman/cronbach_alpha/icc keep their arithmetic, signature and semantics; any diff changing an existing jc statistic is an automatic reject. ONE sanctioned edit: widening reliability.rs private helpers (mean/all_finite/average_ranks/pop_var) to pub(crate) for reuse, visibility only, no body change. C1 audit found phi = pearson-on-binaries (already present in substance) and KR-20 = alpha-on-dichotomous (naming only); kappa absent = the real gap. SHIPPED as crates/jc/src/stats.rs: cohen_kappa, omega_total, phi, multiple_r/multiple_r_squared, eta_squared, t_test_one_sample/paired/welch/student, anova_one_way; 31 new tests (107 lib + 11 doctests green), clippy-clean. Existing-file diff is visibility-only (mean/all_finite -> pub(crate); average_ranks/pop_var NOT widened, unused). Unblocks D3's fusion falsifier | lance-graph | In PR | plan W0/C1b |
+| D-KIA-C1b | jc additive-only extension: kappa + McDonald's omega + r-family effect size (R/R-squared, eta-squared = explained variance) + t-test (t/df/p) + a named phi wrapper. Cohen's d explicitly OUT — calculated separately if ever wanted. HARD CONSTRAINT: additive only — pearson/spearman/cronbach_alpha/icc keep their arithmetic, signature and semantics; any diff changing an existing jc statistic is an automatic reject. ONE sanctioned edit: widening reliability.rs private helpers (mean/all_finite/average_ranks/pop_var) to pub(crate) for reuse, visibility only, no body change. C1 audit found phi = pearson-on-binaries (already present in substance) and KR-20 = alpha-on-dichotomous (naming only); kappa absent = the real gap. SHIPPED as crates/jc/src/stats.rs: cohen_kappa, omega_total, phi, multiple_r/multiple_r_squared, eta_squared, t_test_one_sample/paired/welch/student, anova_one_way; 31 new tests (107 lib + 11 doctests green), clippy-clean. Existing-file diff is visibility-only (mean/all_finite -> pub(crate); average_ranks/pop_var NOT widened, unused). Unblocks D3a (overlap MEASUREMENT) — NOT a fusion claim: kappa is chance-corrected agreement under the observed marginals and says nothing about incremental value, so fusion still needs D3b's external criterion per the plan's own C3. Corrective slice (external review): omega sign-erasure + R-squared scale-dependence fixed; BinaryAssociation/kr20 added | lance-graph | Shipped (#887) + corrective slice | plan W0/C1b |
 | D-KIA-A2 | parallelism falsifier (protocol pre-registered: median-of-5, >=2x at >=4k owners, +/-10% stay-silent; kill = regrade claim (a)) | lance-graph | Queued | plan W2 |
 | D-KIA-B1 | catalog binary-range criterion contract type + generalized catalog-mirror drift guard | lance-graph | Queued | plan W3 |
 | D-KIA-C5 | cohort-statistic witness type under the ELEVATED carve-out + held-out anti-circularity gate | lance-graph | Queued | plan W4 |
 | D-KIA-D1 | observer/observed as two Locus categories over one arena (cheapest-first) | lance-graph | Queued | plan W5 |
-| D-KIA-D3 | Horizontverschmelzung fusion falsifier, middle band pre-registered; corpus-side Synthesis producer (un-blocks session task #65 gate 1 — session-local task list, not a GitHub number) | lance-graph | Queued | plan W6 |
+| D-KIA-C2 | Name the dichotomous statistics correctly (Pearson->phi, alpha->KR-20, kappa NOT a renamed ICC, Spearman dropped on binaries). AUDIT RESULT 2026-08-04: the jc reliability battery has exactly 4 consumers (style_table_agreement, rung_divergence_reliability, partof_isa_vs_palette256, l9_loci_real_text) and NONE is dichotomous — style columns, rung levels 1-10, palette/taxonomy distances, i4 loci offsets are all continuous/ordinal, so Pearson/alpha/ICC are correctly named at every existing call site and there is ZERO rename work today. The discipline binds PROSPECTIVELY at the first binary-criteria witness (D3). Surfaced instead: TD-STATS-DEGENERACY-CONTRACT-DIVERGENCE | lance-graph | Audited (no rename work; binds at D3) | plan W0/C2 |
+| D-KIA-D3a | DESCRIPTIVE binary overlap: contingency counts + BOTH marginals + observed/expected agreement + kappa + phi, via jc::stats::binary_association. Claim ceiling is overlap / disagreement / marginal asymmetry / redundancy-or-complementarity CANDIDATE. No fusion or validity claim | lance-graph | Queued (unblocked) | plan W6 |
+| D-KIA-D3b | HELD-OUT fusion falsifier — BLOCKED until an external criterion and a criterion-appropriate scoring rule are chosen. Continuous criterion: pre-registered delta-R-squared = R2(A+B) - max(R2(A),R2(B)). Binary criterion: a proper held-out score, NOT R-squared forced onto it. Reliability is not validity (plan C3) | lance-graph | Blocked (needs external criterion) | plan W6 |
 
 ## PROBE-BABEL-STANCES — two Rosetta stones + four-channel phase split (IN PR — slice 2, 2026-07-28)
 

.claude/board/TECH_DEBT.md

@@ -1,5 +1,50 @@
 # Technical Debt Log — Open + Paid (double-entry, append-only)
 
+## TD-STATS-DEGENERACY-CONTRACT-DIVERGENCE (2026-08-04)
+
+**Measured, not estimated** (at `a9f813c`, workspace-wide grep over `crates/`):
+
+| return type of hand-rolled `pearson` / `spearman` / `cronbach_alpha` | definitions |
+|---|---|
+| bare `f64` | 47 |
+| bare `f32` | 9 |
+| **`Option<f64>` (the degeneracy contract)** | **3 — all of them jc's own** |
+
+**The debt is a CONTRACT divergence, not duplication.** `jc::reliability`'s
+whole documented design point is that degenerate input (constant series,
+ragged lengths, `n < 2`, non-finite values, overflowed denominators) returns
+`None`, so a caller can never mistake an undefined estimate for a measured
+one. The 56 hand-rolled copies drop that guarantee, and at least one
+**collapses every degeneracy to `0.0`** — `perturbation-sim/src/stats.rs:11`
+returns `0.0` for ragged input, for `n < 2`, and for zero variance, which is
+byte-identical to a genuine "perfectly uncorrelated" result. A caller cannot
+distinguish *"r = 0 because the variables are unrelated"* from *"r = 0 because
+I handed you a constant vector"*. Several also omit the non-finite guard
+entirely, so a `NaN` in the input propagates to a finite-looking or `NaN`
+result rather than being rejected.
+
+**This is the falsifiability rule's defect class one level down:** a statistic
+that reports `0.0` for "undefined" **cannot fail visibly**, exactly like a
+guard that never fires. It is worse than a wrong number because it is a wrong
+number wearing the costume of a right one.
+
+**Also a correction to a shipped doc claim.** `reliability.rs`'s module header
+says callers rolled their own "until now", implying consolidation happened.
+The measurement says otherwise: consolidation happened for *new* callers only
+(4 jc examples), while 56 pre-existing definitions remain. The header
+overstates; treat it as *aspiration*, not inventory, until this is paid.
+
+**Not paid here, deliberately.** Migrating 56 definitions across ~26 files is
+its own wave, each call site owned by its author per the workspace's
+clippy-tier convention, and several are `f32` in hot paths where the `Option`
+wrapper is a real (if small) signature change. **Suggested paydown order by
+risk:** (1) any duplicate returning `0.0` for degeneracy — the silent-wrong
+class; (2) duplicates without a non-finite guard; (3) plain `f64` duplicates
+that already reject degeneracy some other way; (4) `f32` hot-path copies last,
+if at all. **Do not auto-fix** — each migration is a decision about what the
+call site should do when the estimate is undefined, which is precisely the
+information the current code throws away.
+
 ## TD-WORKSPACE-FMT-DRIFT (2026-07-30)
 
 **Measured, not estimated.** `cargo fmt --all -- --check` at