docs(analysis): R2 inventory ledger — reader 10/0/0, 6 families read+solved+verified (R2 C9)

Records the final R2 v1 state: reader setup_correct 10 / setup_wrong 0 + 3 correct reader-refusals; 7 solved answers + 3 solver-refused + 3 reader-refused; gold 13/13. Per-fixture table, the four wrong=0 gates, the reader-vs-solver division of labor (equal coefficients are a solver refusal, not a reader one), covered families, and R3 deferrals. R1 7/0/3 and 15-case 15/0/0 unchanged.

docs/analysis/r2-inventory-ledger-2026-06-07.md

@@ -0,0 +1,94 @@
+# R2 finite-integer constraint-compiler inventory ledger
+
+**As of:** R2 C5–C9 (reader landed), on `main @ 0e6a7f9a` + `feat/r2-constraint-setup-compiler`
+**Lane state:**
+- R2 reader (setup): **10 setup_correct / 0 setup_wrong / 0 missed** + **3 correct reader-refusals**
+- R2 answers: **7 solved / 0 wrong** + **3 solver-refused** + **3 reader-refused**
+- R2 gold validation: **13 / 13 valid**
+- R1 unchanged: **7 / 0 / 3** · 15-case **15 / 0 / 0**
+
+This is the R2 twin of the R1 ledger: a decision artifact recording exactly which constraint
+families the off-serving organ now *reads, solves, and verifies*, which it *refuses*, and the
+gate protecting each. R2 is disjoint from the GSM8K serving path (imports no
+`generate.derivation` / `core.reliability_gate`), so none of this moves the sealed serving
+metric. See ADR-0211 for the contract.
+
+## Reproduce
+
+```bash
+.venv/bin/python -m evals.constraint_oracle           # gold validation -> 13/13 valid
+.venv/bin/python -m evals.constraint_oracle reader    # reader grading  -> setup_wrong 0
+.venv/bin/python -m pytest tests/test_constraint_reader.py tests/test_constraint_solver.py \
+    tests/test_answer_choices.py tests/test_constraint_oracle.py \
+    tests/test_constraint_comprehension_model.py -q
+```
+
+## The pipeline (per the north star)
+
+```text
+prose -> read_constraint_problem -> ConstraintProblem -> solve (Cramer, exact int) -> answer
+      -> verify_answer_choice (tie to one option / flag a wrong key)
+```
+
+Four independent gates, each wired to fail loudly (the wrong=0 boundary):
+
+| Gate | Module | Refuses |
+|---|---|---|
+| reader | `generate/constraint_comprehension/reader.py` | `too_many_categories`, `missing_total_count`, `missing_weighted_total` (+ defensive `coefficient_unit_mismatch`, `query_target_not_a_category`) |
+| setup oracle | `evals/constraint_oracle/signature.py` | any drift in unknowns/facts/constraints/query vs gold ⇒ `setup_wrong` |
+| solver | `generate/constraint_comprehension/solver.py` | `indistinguishable_weights`, `non_integer_solution`, `negative_solution`, `verification_failed` |
+| answer-choice | `generate/answer_choices/verify.py` | `no_matching_option`, `ambiguous_options`, `unknown_provided_label`; flags `contradiction` |
+
+## Per-fixture ledger (13 fixtures)
+
+| Fixture | Family | Reader (setup) | Solver | Answer |
+|---|---|---|---|---|
+| `r2-001-buses` | buses / seats | ✅ correct | `large=4` | C ✅ |
+| `r2-002-chickens` | animals / legs | ✅ correct | `chicken=11` | A ✅ |
+| `r2-003-tickets` | tickets / price | ✅ correct | `adult=20` | B ✅ |
+| `r2-004-coins` | coins / value | ✅ correct | `dime=9` | A ✅ |
+| `r2-005-boxes` | boxes / capacity | ✅ correct | `large=4` | A ✅ |
+| `r2-006-vehicles` | vehicles / wheels | ✅ correct | `car=6` | B ✅ |
+| `r2-007-pens` | tools / price | ✅ correct | `pen=9` | B ✅ |
+| `r2-008-negative` | buses / seats | ✅ correct | ⛔ `negative_solution` | — |
+| `r2-009-non-integer` | items / price | ✅ correct | ⛔ `non_integer_solution` | — |
+| `r2-010-indistinguishable` | vehicles / wheels | ✅ correct | ⛔ `indistinguishable_weights` | — |
+| `r2-011-missing-total-count` | (incomplete) | ⛔ `missing_total_count` | — | — |
+| `r2-012-missing-weighted-total` | (incomplete) | ⛔ `missing_weighted_total` | — | — |
+| `r2-013-too-many-categories` | (ambiguous) | ⛔ `too_many_categories` | — | — |
+
+**Key reconciliation:** the three `solver_refuses` fixtures (008–010) read **setup_correct** —
+the reader's job is the *setup*, not solvability. Equal coefficients (010) are not a reader
+refusal; they are the solver's `indistinguishable_weights`. So the reader reads all ten
+well-formed setups and the solver owns the three unsolvable ones. This is the load-bearing
+division of labor that keeps the reader's wrong=0 boundary clean.
+
+## Covered families (the near-term milestone)
+
+The six two-category count/weight families the user named are all read → solved → verified
+with `setup_wrong = 0`, `answer_wrong = 0`, and answer-key contradictions flaggable:
+
+```text
+bus / seat        chicken / leg      ticket / price
+coin / value      box / capacity     vehicle / wheel   (+ tool / price)
+```
+
+## Deferred to R3 (NOT in this batch — see ADR-0211 §2)
+
+- ≥3 categories, inequalities, multi-step / mixed constraints, distractor exclusion,
+  rates / unit conversion.
+- The **typed contemplation loop + reviewed-failure learning** (plan Phases 6–7). When built,
+  the failure-learning half routes through the existing `teaching/*` proposal-only flywheel
+  (ADR-0055/0056/0057) — never a parallel correction path.
+- Generalization to **real** GSM8K constraint prose (this gold is curated synthetic v1; the
+  reader recognizes structural patterns, not fixed strings, but real-corpus validation is R3).
+
+## Decision and trajectory
+
+R2 v1 is the off-serving finite-integer two-category constraint setup compiler, complete on
+the C0–C9 ladder. It is a meaningful capability leap (constraint *systems*, not relational
+arithmetic) built on the same disciplined ladder as R1 — gold → setup oracle → solver →
+answer verifier → reader — and it earns each family only where the gold + oracle + refusal
+tests already license it. No guessed math, no silent correction, no answer without a proven
+setup. Next axis (a later batch): R3 / the typed contemplation + reviewed-failure-learning
+bridge to the L11 flywheel.