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

@@ -68,3 +68,46 @@ Each fix is developed against tune only, to `wrong=0` on tune; the measure split
 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.
+
+## Shared-layer reality — the whole-tune refusal histogram (pinned baseline)
+
+Across ALL 261 tune cases (not just compare-marked), the reader's refusal-reason histogram — pinned
+**before** any shared-layer edit, asserted **stable-or-explained** after:
+
+| Refusal reason | Cases |
+| :--- | ---: |
+| **no injection** | **196** |
+| no admissible candidate for statement | 48 |
+| expected exactly one question | 9 |
+| no admissible candidate for question | 4 |
+| **PARSED** (all compare) | **3** |
+| no branch produced a solvable | 1 |
+
+**"no injection" is 196/261 (75%) — a *shared* bottleneck across every family, not a compare defect.**
+The reader recognizes statements but can't inject candidates for three-quarters of real GSM8K. A
+guard-lift that silently changed *why* other cases refuse would corrupt the practice-lane curriculum
+even with zero parse breakage, so the histogram is pinned; the only sanctioned post-edit delta is
+compare cases moving from "no injection" → PARSED (or to a downstream layer), disclosed explicitly.
+
+## Funnel-conditioned escalation rule (PRE-COMMITTED, before the number exists)
+
+X = 15 was ratified assuming *family capability* was the wall. The baseline shows the wall may be the
+**shared pipeline** (injection / enumeration / admissibility / round-trip) that every family crosses.
+So a miss on X is read through the funnel:
+
+- **Mass dying in compare-specific logic** → the family's design well is dry → **practice-lane ruling**
+  (as designed).
+- **Mass dying in a shared layer** → the next increment is a **shared-layer design increment**, *not*
+  a practice escalation. X is re-applied after the shared layer is fixed.
+
+Load-bearing reason: **the practice lane cannot learn past a deterministic wall.** A practice loop
+generates better parse *candidates*, but they cross the same enumeration/admissibility/round-trip
+pipeline; if a hard-coded shared layer refuses everything, practice fails identically — escalating into
+a mechanism that can't help. Shared-layer bottlenecks are design work regardless of what X says.
+
+## Reframe (recorded)
+
+Compare is the **first slice of a much larger reader project**: the reader parses ~1% of real GSM8K
+(3/261 tune), and "no injection" (75%) is a shared wall in front of every family. This is not scope
+creep — it is the arc seeing its true size. The increments stay small and measured *precisely because*
+the project is large.