docs/research/compare-increment-funnel-2026-07-18.md

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+# compare_multiplicative Increment — Per-Layer Attrition Funnel (diagnostic artifact)
+
+**Status**: DIAGNOSTIC — instrument-first, decides the fix order (PR #76 ruling)
+**Date**: 2026-07-18
+**Scope**: the 61 compare-multiplicative-marked cases in the **tune** split of official `holdout_dev/v1`
+(measure split untouched). Signals are the reader's own: `branches_enumerated`, `refusal_reason`,
+`selected_graph`, then the corridor compiler.
+
+---
+
+## The funnel
+
+Reader pipeline stages: recognizer-match → **injection** → enumeration → admissibility → graph → solve.
+
+| Layer | Cases (of 61) |
+| :--- | ---: |
+| Died **pre-enumeration** | **57** |
+| Enumerated | 4 |
+| …enumerated but no graph | 1 |
+| …graph has a compare op | 3 |
+| **Solved today** | **3** |
+
+Pre-enumeration refusal reasons (the 57):
+
+| Reason | Cases |
+| :--- | ---: |
+| **"recognizer matched but produced no injection"** | **45** |
+| "no admissible candidate for statement" | 8 |
+| "expected exactly one question sentence" | 3 |
+| "no admissible candidate for question" | 1 |
+
+## The finding
+
+**The leverage is the injection layer: 45 / 61.** The recognizer already *matches* these compare
+statements (e.g. 0000: "Aria has twice as many … as Emily, who has twice the number … as Spencer");
+the **injection** step then produces no candidate — the multi-clause / compare shapes don't inject.
+This is where the mass is — not the candidate regexes (they fire on clean clauses but the real
+sentences never reach them), and not segmentation writ large.
+
+## Consequence for the fix (emitter-fix, not gate-loosening)
+
+Injection is an **emitter** (it produces candidates), not a validator — so making it inject
+compare candidates for statements the recognizer already matches is the sanctioned kind of change
+(fix emitters; never loosen the round-trip gate). The remaining piles are secondary and sequenced
+after: "no admissible candidate for statement" (8), the one-question-sentence constraint (3).
+
+Fix order, by measured mass: **injection (45) → statement-admissibility (8) → question-sentence (3)**.
+Each fix is developed against tune only, to `wrong=0` on tune; the measure split gets its single run
+at the end. Refusal-by-reason on the measure split (frequency / nested / anaphora / temporal /
+inverse-undeterminable) is reported with the delta as the fail-closed evidence + the practice-lane
+curriculum.