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+# Independent Comprehension Agreement Gate
+
+**Status:** research-control document
+**Date:** 2026-06-04
+**Scope:** non-serving; defines the gate that must exist before any new field-backed or GSM8K-positive capability promotion.
+
+## 1. Problem
+
+The recent GSM8K post-mortem established the central failure mode: a committing reader can appear safe on a built-against slice while being unsound on held-out or sealed data. The repair was not another recognizer branch; it was the independent-gold discipline (INV-25) plus the universal-structure plan.
+
+PRs #554-#558 now give CORE the foundation:
+
+- independent-gold invariant and SHA-pinned deductive lane;
+- binding-graph interlingua neutrality (INV-26);
+- finite-entity grounding into propositional entailment;
+- dimensional reasoning with an independent dimensional oracle;
+- a 3-domain anti-overfit panel.
+
+The remaining unsolved problem is not solving after a structure is already extracted. It is **independent comprehension**: can two genuinely independent readers construct the same canonical problem structure from the same task, and only then solve or verify it?
+
+## 2. Doctrine
+
+```text
+A second solver over the same extracted structure is not a second derivation.
+A second derivation begins with an independently constructed structure.
+```
+
+Agreement must therefore be tested at the structure boundary, not only at the final answer boundary.
+
+Bad independence:
+
+```text
+shared parser -> symbolic solver
+shared parser -> field/geometric solver
+```
+
+Good independence:
+
+```text
+symbolic reader -> canonical structure
+field/geometric reader -> canonical structure
+structure-equivalence gate -> oracle/proof solver -> commitment eligibility
+```
+
+## 3. Gate definition
+
+A candidate capability may become promotion-eligible only if it passes all of the following gates.
+
+| Gate | Requirement | Failure result |
+|---|---|---|
+| Reader independence | The two readers do not share parser, candidate generator, gold, or structure-building code. | Refuse / research failure |
+| Canonical structure | Both readers emit a canonical, hashable structure with target, facts, relations, dimensions, and provenance. | Refuse |
+| Structure equivalence | Structures are equal under a domain-specific equivalence relation stricter than same-answer. | Refuse |
+| Independent gold | A proof checker, oracle, sealed set, or other non-SUT arbiter agrees. | Wrong/fail |
+| Replay | Structure hashes and verdict traces are deterministic across replay. | Fail |
+| Promotion wall | No serving path changes until held-out/sealed wrong=0 holds. | Block promotion |
+
+## 4. Canonical structure minimum
+
+Every participating structure must carry at least:
+
+```text
+structure_id
+source_case_id
+entities
+quantities
+units_or_types
+relations
+question_target
+provenance_spans_or_hashes
+unsupported_features
+trace_sha256
+```
+
+The target is load-bearing. Two readers that agree on facts but bind different targets have not agreed.
+
+## 5. Equivalence semantics
+
+The first equivalence primitive should be intentionally narrow.
+
+Equivalent:
+
+- same target;
+- same required entities;
+- same quantity values after canonical numeric normalization;
+- same dimensions/types;
+- same relation kind and operands;
+- same proof obligations;
+- same unused-evidence classification.
+
+Not equivalent:
+
+- same numeric answer but different relation;
+- same relation but different target;
+- one structure ignores a required source quantity;
+- one structure treats a distractor as relevant and the other exempts it;
+- units/dimensions differ;
+- either structure depends on an unsupported inferred fact.
+
+## 6. Disagreement taxonomy
+
+Closed disagreement reasons for the first implementation:
+
+```text
+missing_target
+relation_mismatch
+quantity_mismatch
+dimension_mismatch
+entity_binding_mismatch
+unused_evidence_mismatch
+unsupported_feature_mismatch
+same_answer_different_structure
+oracle_disagreement
+reader_not_independent
+```
+
+These reasons should feed future contemplation/practice reports directly. The learning signal should identify the failed primitive, not merely the domain class.
+
+## 7. Required proof of reader independence
+
+A reader pair must provide a `DecoderIndependenceProof`-style record:
+
+```text
+reader_a_module
+reader_b_module
+shared_import_allowlist
+forbidden_shared_modules
+oracle_module
+uses_same_parser: false
+uses_same_candidate_generator: false
+uses_same_gold: false
+```
+
+The test should include at least one AST/import scan like INV-25/INV-26, plus at least one behavioral non-vacuity test proving the guard can fail.
+
+## 8. First implementation target
+
+The first implementation should not be GSM8K and should not be broad natural language.
+
+Recommended target:
+
+```text
+structured quantitative-relational lane
+  -> symbolic structured compiler
+  -> field/geometric structured compiler
+  -> canonical structure equivalence
+  -> independent quantitative oracle
+```
+
+This gives the field side a domain where geometry/metric relations are native, while avoiding the prior GSM8K failure mode.
+
+## 9. Stop conditions
+
+Stop and document instead of patching around the result if:
+
+1. the field reader imports or calls the symbolic reader;
+2. the two readers only agree on final answers, not structures;
+3. equivalence admits same-answer/different-reason cases;
+4. the oracle shares code with either reader;
+5. a proposed gate passes only on built-against examples;
+6. any route to serving is proposed before held-out/sealed wrong=0.
+
+## 10. PR sequence
+
+1. **Structure-equivalence primitive** — `core/reasoning/structure_equivalence.py` plus tests.
+2. **Quantitative-relational structured lane** — independent oracle and structured cases.
+3. **Field quantitative decoder prototype** — no symbolic reader imports.
+4. **Controlled NL compiler** — only after structured symbolic/field agreement exists.
+5. **GSM8K structure diagnostic** — non-serving, coverage-only.
+
+## 11. Success definition
+
+The first milestone succeeds when a supported case can be read by two independent readers into equivalent canonical structures, solved against independent gold, replayed deterministically, and refused on disagreement without touching serving.