feat(kernel): introduce construction-affordance catalog skeleton

HANDOFF-gpt55-2026-06-20.md

@@ -177,3 +177,41 @@ The substantive result of this session is not just “0005 runnable.” It is th
 - pre-edit-sweep: manual import/call-site sweep completed
 - claim-proposal-guardian: not needed
 - Other: none
+
+---
+
+## PR #836 Addendum — feat(kernel): introduce construction-affordance catalog skeleton
+
+### Agent and Session
+
+- **Agent:** Antigravity (Gemini 3.5 Flash)
+- **Date:** 2026-06-20
+- **Task:** Implement `feat(kernel): introduce construction-affordance catalog skeleton` (PR #836)
+- **Branch:** `feat/kernel-construction-affordance-catalog`
+
+### Modules Touched / Created
+
+| File | Change type | Summary |
+|---|---|---|
+| `generate/construction_affordances.py` | NEW | Frozen, typed structures (`RoleObligation`, `ConstructionHazard`, `ConstructionSignature`, `ConstructionFamily`, `ConstructionContract`, `ConstructionProposal`) and initial catalog registry with two diagnostic families (`proportional_change.decrease_to_fraction` and `partition.percent_partition`). |
+| `generate/problem_frame_contracts.py` | modified | Added `_CONTRACT_REGISTRY` mapping candidate organs to ConstructionContract; updated module docstring and refactored `assess_contracts()` to reference registry metadata. |
+| `generate/problem_frame_builder.py` | modified | Added detailed docstring to `_bound_question_target` describing the priority cascade. |
+| `tests/test_problem_frame_contracts.py` | modified | Added 7 new test cases verifying scale boundary rejection (0, 1, >1), multi-base rejection, state entity continuity, unit continuity, and percent-partition blocker specificity. |
+| `tests/test_construction_affordances.py` | NEW | Added 5 tests verifying catalog constraints (`serving_allowed=False`, `diagnostic_only=True`), deterministic order, accessor lookups, and `make_proposal()` status mapping. |
+| `docs/analysis/pr836-lookback-2026-06-20.md` | NEW | Lookback documenting design choices (diagnostic-only registry, separation of registry and dispatch, priority cascade, test gaps closed). |
+
+### Invariants Verified
+
+- **Versor condition**: No geometric algebra files were touched; versor invariants remain fully satisfied.
+- **Serving parity**: Verified by running evaluation scripts:
+  - Train: `30 correct / 20 refused / 0 wrong` (wrong_ids: `[]`)
+  - Holdout: `5 correct / 495 refused / 0 wrong` (wrong_ids: `[]`)
+- **Adequacy**:
+  - Train runnable: `2` (v1-0005 and v1-0046)
+  - Holdout runnable: `0`
+
+### Tests Run
+
+- **Targeted suite**: `tests/test_problem_frame_builder.py`, `tests/test_problem_frame_contracts.py`, `tests/test_construction_affordances.py`, `tests/test_gsm8k_problem_frame_adequacy.py`, `tests/test_gsm8k_morphology_missing_kernel_labels.py` -> **46 passed** in `0.48s`.
+- **Smoke suite**: `core.cli test --suite smoke -q` -> **108 passed** in `129.00s`.
+

docs/analysis/pr836-lookback-2026-06-20.md

@@ -0,0 +1,36 @@
+# PR #836 Lookback — feat(kernel): introduce construction-affordance catalog skeleton
+
+This lookback documents the design rationale, implementation details, and verification results for the initial slice of the construction-affordance catalog skeleton.
+
+## Rationale & Design Choices
+
+### 1. Catalog Registry is Diagnostic-Only
+Every entry in `generate/construction_affordances.py` is configured with `diagnostic_only=True` and `serving_allowed=False`. This enforces a clean trust boundary:
+- Candidate structures and affordances can be registered, introspected, and traced diagnostically.
+- The runtime serving path remains completely untouched and isolated, preventing any serving-time regressions.
+
+### 2. Separation of Registry and Dispatch Logic
+The contract assessment functions (`assess_fraction_decrease` and `assess_percent_partition` in `generate/problem_frame_contracts.py`) contain construction-specific structural logic, role bindings, and hazard checks.
+- We introduced `_CONTRACT_REGISTRY` to map candidate organs to catalog entries.
+- To prevent a leaky abstraction and forced interfaces, the actual dispatch in `assess_contracts()` remains explicit and structural, but references the catalog metadata where applicable.
+- This ensures the registry remains a metadata/introspection layer describing *what* a construction means, while the assessment functions describe *how* its obligations are proven.
+
+### 3. Question-Target Priority Cascade
+We documented the priority cascade inside `_bound_question_target` (in `generate/problem_frame_builder.py`). This prevents order-fragility in future additions:
+1. Specific regex-based triggers (e.g. `_DECREASE_DELTA_QUESTION_RE` for proportional decrease delta).
+2. General question clause extraction via `_QUESTION_ENTITY_RE` (or fallback to unresolved if `?` is present).
+3. Clause-level target classification (e.g. `more` -> difference, `originally` -> initial, `left` -> final, etc.).
+
+## Closed Test Gaps
+
+We successfully added targeted test coverage to `tests/test_problem_frame_contracts.py` to close all outstanding edge cases from the proportional-change proof of concept:
+- **Scale boundary rejection**: Rejects scale values of 0 (`0/4`), 1 (`4/4`), or greater than 1 (`5/4`) with a `scale_out_of_range` blocker.
+- **Multi-base rejection**: Ensures multiple candidate relations trigger `decrease_relation_ambiguous`.
+- **State entity continuity**: Rejects cases where the state entity in the relation differs from the target entity of the question, triggering `state_entity_continuity_unproven`.
+- **Unit continuity**: Rejects cases where the base quantity unit does not match the relation unit, triggering `unit_continuity_unproven`.
+- **Percent-partition blocker specificity**: Asserts that unequal-partition confusers correctly surface `partition_subgroups_not_distinct` and `percent_subgroup_links_incomplete`.
+
+## Verification Results
+
+- All 46 tests across the targeted test suite pass successfully in `< 0.5s`.
+- Catalog behavior verified by new dedicated tests in `tests/test_construction_affordances.py`.

generate/construction_affordances.py

@@ -0,0 +1,458 @@
+"""Construction-affordance catalog skeleton.
+
+Formalizes the constructional-affordance pattern proved by PR #835 so future
+diagnostic families do not become scattered local parser patches.
+
+This module is a catalog/registry skeleton only.  It does NOT:
+- claim CGA/substrate geometric retrieval (no manifold calls here);
+- label local regex matching as substrate cognition;
+- add any acquisition/transaction or transfer/loss/rate/comparison families;
+- affect serving (all entries have ``serving_allowed=False``).
+
+Every entry in this catalog is ``diagnostic_only=True``.  The catalog expresses
+what a construction *means*, what roles it requires, what hazards it carries, and
+what target semantics close it.  The assessment functions that check actual
+ProblemFrame evidence live in ``generate/problem_frame_contracts.py``.
+
+Design doctrine (from ADR-0223):
+    Words and chunks are probes into the semantic substrate.
+    They surface candidate affordances and relation families.
+    Semantic closeness proposes.
+    Exact span bindings ground.
+    Organ-specific contracts determine.
+    Unsupported or ambiguous cases refuse.
+"""
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from generate.kernel_facts import SourceSpan
+
+
+# ---------------------------------------------------------------------------
+# Frozen typed structures
+# ---------------------------------------------------------------------------
+
+
+@dataclass(frozen=True, slots=True)
+class RoleObligation:
+    """A single role obligation for a construction.
+
+    Args:
+        role:        Role name that must be bound (e.g. ``"base_quantity"``).
+        required:    If True, absence blocks contract closure.  If False, the
+                     role is advisory only.
+        description: Human-readable description of what this role represents.
+    """
+
+    role: str
+    required: bool
+    description: str
+
+
+@dataclass(frozen=True, slots=True)
+class ConstructionHazard:
+    """An ambiguity or confuser hazard associated with a construction family.
+
+    Args:
+        hazard_category: Matches ``KernelHazard.category`` in the frame.
+        blocking:        If True, the presence of this hazard blocks closure.
+        description:     Explanation of what the hazard represents.
+    """
+
+    hazard_category: str
+    blocking: bool
+    description: str
+
+
+@dataclass(frozen=True, slots=True)
+class ConstructionSignature:
+    """The relational signature of a construction: its type, organ, and roles.
+
+    Args:
+        relation_type:  The ``BoundRelation.relation_type`` value that carries
+                        this construction (e.g. ``"decrease_to_fraction"``).
+        candidate_organ: The assessment organ identifier produced by the
+                         corresponding contract (e.g. ``"fraction_decrease"``).
+        required_roles:  Roles that must be bound for the contract to be
+                         declared runnable.
+        optional_roles:  Roles that improve precision but are not blocking.
+    """
+
+    relation_type: str
+    candidate_organ: str
+    required_roles: tuple[RoleObligation, ...]
+    optional_roles: tuple[RoleObligation, ...]
+
+
+@dataclass(frozen=True, slots=True)
+class ConstructionFamily:
+    """A reviewed construction-affordance family declaration.
+
+    Args:
+        family_id:       Stable dotted identifier, e.g.
+                         ``"proportional_change.decrease_to_fraction"``.
+        display_name:    Short human-readable label.
+        signature:       Relational signature (roles, organ, type).
+        hazards:         Known hazards and confusers for this family.
+        target_semantics: Required (operator, state, direction) values for the
+                         bound question target (free-form strings matching
+                         ``BoundQuestionTarget`` fields).
+        contract_labels: Stable blocker code strings used in
+                         ``ContractAssessment.missing_bindings``.
+        diagnostic_only: Always True in this PR; the construction may produce
+                         diagnostic assessments but must not change serving.
+        serving_allowed: Always False in this PR.  No construction may be
+                         promoted to serving without a separate reviewed PR.
+    """
+
+    family_id: str
+    display_name: str
+    signature: ConstructionSignature
+    hazards: tuple[ConstructionHazard, ...]
+    target_semantics: tuple[str, ...]
+    contract_labels: tuple[str, ...]
+    diagnostic_only: bool
+    serving_allowed: bool
+
+    def __post_init__(self) -> None:
+        if self.serving_allowed:
+            raise ValueError(
+                f"ConstructionFamily {self.family_id!r}: "
+                "serving_allowed must be False in this PR — "
+                "no construction may be promoted to serving without a separate reviewed PR."
+            )
+        if not self.diagnostic_only:
+            raise ValueError(
+                f"ConstructionFamily {self.family_id!r}: "
+                "diagnostic_only must be True — "
+                "this PR registers catalog skeleton entries only."
+            )
+
+
+@dataclass(frozen=True, slots=True)
+class ConstructionContract:
+    """Registry entry binding a ConstructionFamily to its assessment function.
+
+    Args:
+        family:          The construction family declaration.
+        assess_fn_name:  Name of the assessment function in
+                         ``generate.problem_frame_contracts`` (for introspection
+                         only; the function is not called through this struct).
+    """
+
+    family: ConstructionFamily
+    assess_fn_name: str
+
+
+@dataclass(frozen=True, slots=True)
+class ConstructionProposal:
+    """Lightweight diagnostic-only trace of a construction proposal.
+
+    Represents the evidence chain::
+
+        chunk/surface evidence
+        → proposed construction family
+        → proposed relation type
+        → role obligations
+        → hazards
+        → status
+
+    A proposal is created by ``make_proposal()`` from ProblemFrame evidence.
+    It does not affect serving.  Its ``status`` reflects whether the
+    corresponding contract assessment declared the frame runnable.
+
+    Args:
+        family_id:       Catalog family identifier, e.g.
+                         ``"proportional_change.decrease_to_fraction"``.
+        relation_type:   The ``BoundRelation.relation_type`` that was searched.
+        candidate_organ: The organ this proposal targets.
+        evidence_spans:  Source spans that motivated the proposal.
+        status:          One of ``"proposed"``, ``"partial"``, ``"closed"``,
+                         ``"refused"``.  ``"closed"`` means the contract
+                         assessment was runnable.
+        missing_roles:   Role obligation names that were absent at assessment time.
+        active_hazards:  Hazard categories that were unresolved at assessment time.
+    """
+
+    family_id: str
+    relation_type: str
+    candidate_organ: str
+    evidence_spans: tuple[SourceSpan, ...]
+    status: str
+    missing_roles: tuple[str, ...]
+    active_hazards: tuple[str, ...]
+
+    _VALID_STATUSES: frozenset[str] = frozenset({
+        "proposed", "partial", "closed", "refused"
+    })
+
+    def __post_init__(self) -> None:
+        if self.status not in self._VALID_STATUSES:
+            raise ValueError(
+                f"ConstructionProposal.status must be one of "
+                f"{sorted(self._VALID_STATUSES)}, got {self.status!r}"
+            )
+
+
+# ---------------------------------------------------------------------------
+# Catalog entries
+# ---------------------------------------------------------------------------
+
+_DECREASE_TO_FRACTION_FAMILY = ConstructionFamily(
+    family_id="proportional_change.decrease_to_fraction",
+    display_name="Proportional decrease to fraction",
+    signature=ConstructionSignature(
+        relation_type="decrease_to_fraction",
+        candidate_organ="fraction_decrease",
+        required_roles=(
+            RoleObligation(
+                "base_quantity",
+                required=True,
+                description="The quantity whose value will decrease (the current/initial state).",
+            ),
+            RoleObligation(
+                "scale",
+                required=True,
+                description=(
+                    "Fraction p/q in (0, 1) exclusive: the new value is scale × base_quantity. "
+                    "Values of 0, 1, or > 1 are rejected."
+                ),
+            ),
+            RoleObligation(
+                "state_entity",
+                required=True,
+                description=(
+                    "The entity (object or actor) whose state undergoes the decrease. "
+                    "Must match the question-target entity for state_entity_continuity."
+                ),
+            ),
+            RoleObligation(
+                "transition",
+                required=True,
+                description='Span anchor for the "decrease to" trigger phrase.',
+            ),
+        ),
+        optional_roles=(
+            RoleObligation(
+                "unit",
+                required=False,
+                description=(
+                    "Unit of the base quantity. When present, unit_continuity is checked: "
+                    "the unit binding on base_quantity must match this role."
+                ),
+            ),
+        ),
+    ),
+    hazards=(
+        ConstructionHazard(
+            hazard_category="unbound_base_quantity",
+            blocking=True,
+            description=(
+                "The base quantity cannot be uniquely identified. "
+                "Multiple candidates or no 'current/now' sentence context."
+            ),
+        ),
+        ConstructionHazard(
+            hazard_category="percent_change_vs_percent_of",
+            blocking=False,
+            description=(
+                "Percent-change surfaces may co-occur; they do not trigger this construction "
+                "because this family only recognises exact fraction (p/q) scale triggers."
+            ),
+        ),
+    ),
+    target_semantics=(
+        "operator:difference",
+        "state:delta",
+        "direction:decrease",
+    ),
+    contract_labels=(
+        "decrease_relation_ambiguous",
+        "base_quantity_unbound",
+        "scale_unbound",
+        "state_entity_unbound",
+        "base_quantity_provenance_missing",
+        "scale_provenance_missing",
+        "unit_continuity_unproven",
+        "delta_decrease_target_unbound",
+        "delta_decrease_target_required",
+        "state_entity_continuity_unproven",
+        "scale_out_of_range",
+    ),
+    diagnostic_only=True,
+    serving_allowed=False,
+)
+
+_PERCENT_PARTITION_FAMILY = ConstructionFamily(
+    family_id="partition.percent_partition",
+    display_name="Percent-based partition of a whole",
+    signature=ConstructionSignature(
+        relation_type="percent_of",  # primary relation type checked in contracts
+        candidate_organ="percent_partition",
+        required_roles=(
+            RoleObligation(
+                "whole",
+                required=True,
+                description=(
+                    "The original numeric whole that the partition subdivides. "
+                    "Must appear before the partition event in text."
+                ),
+            ),
+            RoleObligation(
+                "part",
+                required=True,
+                description=(
+                    "A distinct subgroup of the whole. At least two distinct "
+                    "subgroup-part IDs are required to prove complementary coverage."
+                ),
+            ),
+            RoleObligation(
+                "scale",
+                required=True,
+                description=(
+                    "Percentage or fraction linking part to whole via percent_of relation. "
+                    "Each distinct part must have its own linked scale."
+                ),
+            ),
+        ),
+        optional_roles=(),
+    ),
+    hazards=(
+        ConstructionHazard(
+            hazard_category="unbound_base_quantity",
+            blocking=True,
+            description=(
+                "No numeric whole quantity is bound before the partition event. "
+                "Without a provenance-bearing original whole, closure is refused."
+            ),
+        ),
+        ConstructionHazard(
+            hazard_category="percent_change_vs_percent_of",
+            blocking=True,
+            description=(
+                "Percent-change surface ambiguity: 'percent' could indicate a change "
+                "rather than a partition fraction. Topology proof resolves this."
+            ),
+        ),
+    ),
+    target_semantics=(
+        "operator:count",
+        "state:aggregate",
+        "direction:forward",
+    ),
+    contract_labels=(
+        "grounded_partition_subgroup",
+        "grounded_whole_entity",
+        "original_whole_unbound",
+        "multiple_original_whole_candidates",
+        "partition_subgroups_not_distinct",
+        "percent_subgroup_links_incomplete",
+        "grounded_question_target",
+        "forward_aggregate_target_required",
+        "inverse_topology_unlicensed",
+    ),
+    diagnostic_only=True,
+    serving_allowed=False,
+)
+
+# The catalog.  Keys are family_id strings.  Sorted for deterministic iteration.
+_CATALOG: dict[str, ConstructionFamily] = {
+    _DECREASE_TO_FRACTION_FAMILY.family_id: _DECREASE_TO_FRACTION_FAMILY,
+    _PERCENT_PARTITION_FAMILY.family_id: _PERCENT_PARTITION_FAMILY,
+}
+
+# Secondary indices for O(1) lookup by organ or relation type.
+_BY_ORGAN: dict[str, ConstructionFamily] = {
+    family.signature.candidate_organ: family
+    for family in _CATALOG.values()
+}
+_BY_RELATION_TYPE: dict[str, ConstructionFamily] = {
+    family.signature.relation_type: family
+    for family in _CATALOG.values()
+}
+
+
+# ---------------------------------------------------------------------------
+# Public accessors
+# ---------------------------------------------------------------------------
+
+
+def lookup_family(family_id: str) -> ConstructionFamily | None:
+    """Return the ConstructionFamily for *family_id*, or None if not registered."""
+    return _CATALOG.get(family_id)
+
+
+def lookup_by_organ(candidate_organ: str) -> ConstructionFamily | None:
+    """Return the ConstructionFamily whose signature.candidate_organ matches."""
+    return _BY_ORGAN.get(candidate_organ)
+
+
+def lookup_by_relation_type(relation_type: str) -> ConstructionFamily | None:
+    """Return the ConstructionFamily whose signature.relation_type matches.
+
+    Note: ``percent_partition`` uses two relation types (``percent_of`` and
+    ``subgroup_partition``) in its assessment logic, but the catalog entry
+    declares the primary relation type (``percent_of``) as the lookup key.
+    """
+    return _BY_RELATION_TYPE.get(relation_type)
+
+
+def all_diagnostic_families() -> tuple[ConstructionFamily, ...]:
+    """Return all registered diagnostic families in deterministic (family_id) order."""
+    return tuple(_CATALOG[key] for key in sorted(_CATALOG))
+
+
+def make_proposal(
+    family_id: str,
+    evidence_spans: tuple[SourceSpan, ...],
+    assessment_runnable: bool,
+    missing_roles: tuple[str, ...],
+    active_hazards: tuple[str, ...],
+) -> ConstructionProposal:
+    """Create a lightweight diagnostic-only ConstructionProposal from frame evidence.
+
+    This is a thin factory.  The caller supplies evidence already gathered by
+    ``assess_contracts()``; this function only maps that evidence to the
+    standard proposal trace shape.
+
+    Args:
+        family_id:           Catalog family identifier.
+        evidence_spans:      Source spans from the contract assessment.
+        assessment_runnable: Whether the corresponding ContractAssessment.runnable
+                             was True.
+        missing_roles:       ContractAssessment.missing_bindings contents.
+        active_hazards:      ContractAssessment.unresolved_hazards contents.
+
+    Returns:
+        A ConstructionProposal with status derived from the assessment:
+        - ``"closed"``   if runnable and no missing roles/hazards;
+        - ``"partial"``  if some roles are bound but closure is incomplete;
+        - ``"refused"``  if active hazards block closure;
+        - ``"proposed"`` otherwise (construction proposed but not evaluated).
+
+    Raises:
+        KeyError: If *family_id* is not registered in the catalog.
+    """
+    family = _CATALOG[family_id]  # raises KeyError if absent — intended
+
+    if assessment_runnable:
+        status = "closed"
+    elif active_hazards:
+        status = "refused"
+    elif missing_roles:
+        status = "partial"
+    else:
+        status = "proposed"
+
+    return ConstructionProposal(
+        family_id=family_id,
+        relation_type=family.signature.relation_type,
+        candidate_organ=family.signature.candidate_organ,
+        evidence_spans=evidence_spans,
+        status=status,
+        missing_roles=missing_roles,
+        active_hazards=active_hazards,
+    )

generate/problem_frame_builder.py

@@ -600,6 +600,24 @@ def _bound_relations(
 
 
 def _bound_question_target(text: str, mentions: tuple[GroundedMention, ...]) -> BoundQuestionTarget | None:
+    """Extract and bind the question target from the problem text.
+
+    Priority Cascade Order:
+    1. Specific regex-based triggers:
+       - Proportional decrease delta: checked first using ``_DECREASE_DELTA_QUESTION_RE``.
+         If matched, returns a difference/delta/decrease target.
+    2. General question clause extraction:
+       - Triggers on ``_QUESTION_ENTITY_RE``.
+       - If no match, but "?" is present in the text, returns an "unknown" target.
+    3. Target classification of the question clause:
+       - "more" -> difference / delta / unknown direction.
+       - Initial state indicators ("were in", "was in", "started with", "originally") -> count / initial / inverse.
+       - Remaining indicators ("remaining", "left" in context) -> count / final / remaining.
+       - Aggregate indicators ("total", "altogether", "own") -> count / aggregate / forward.
+       - Portion percentage ("percent", "percentage") -> portion / final / forward.
+       - Portion fraction ("ratio", "fraction") -> portion / final / forward.
+       - Fallback -> count / final / forward.
+    """
     decrease_delta = _DECREASE_DELTA_QUESTION_RE.search(text)
     if decrease_delta is not None:
         entity_surface = decrease_delta.group("entity")

generate/problem_frame_contracts.py

@@ -1,12 +1,57 @@
-"""Diagnostic organ-contract readiness derived only from ProblemFrame evidence."""
+"""Diagnostic organ-contract readiness derived only from ProblemFrame evidence.
+
+Contract dispatch is deliberately narrow:
+- ``assess_contracts()`` routes to two diagnostic assessment functions.
+- The ``_CONTRACT_REGISTRY`` provides catalog metadata for introspection and
+  proposal-trace generation; it does not replace the structural logic inside
+  each assessment function.
+- All registered contracts have ``serving_allowed=False``; this module must
+  never be imported from serving dispatch paths.
+"""
 from __future__ import annotations
 
 from dataclasses import dataclass
 
+from generate.construction_affordances import (
+    ConstructionContract,
+    _DECREASE_TO_FRACTION_FAMILY,
+    _PERCENT_PARTITION_FAMILY,
+    make_proposal,
+)
 from generate.kernel_facts import BoundRelation, SourceSpan
 from generate.problem_frame import ProblemFrame
 
 
+# ---------------------------------------------------------------------------
+# Contract registry
+#
+# Maps candidate_organ -> ConstructionContract.  This registry provides
+# metadata for proposal-trace generation and external introspection.  It does
+# not replace the per-assessment dispatch logic in assess_contracts(); the
+# structural proof obligations for each family live inside the dedicated
+# assess_* functions below.
+#
+# Why not route dispatch through the registry?
+# assess_fraction_decrease and assess_percent_partition each contain
+# construction-specific structural logic (role iteration, topology proofs,
+# hazard escalation) that cannot be generalised behind a single callable
+# without introducing a forced abstraction boundary.  The registry expresses
+# *what* a construction is; the assessment functions express *how* its
+# obligations are checked.  Both layers are needed and should remain separate.
+# ---------------------------------------------------------------------------
+
+_CONTRACT_REGISTRY: dict[str, ConstructionContract] = {
+    "fraction_decrease": ConstructionContract(
+        family=_DECREASE_TO_FRACTION_FAMILY,
+        assess_fn_name="assess_fraction_decrease",
+    ),
+    "percent_partition": ConstructionContract(
+        family=_PERCENT_PARTITION_FAMILY,
+        assess_fn_name="assess_percent_partition",
+    ),
+}
+
+
 @dataclass(frozen=True, slots=True)
 class ContractAssessment:
     candidate_organ: str
@@ -241,13 +286,35 @@ def assess_percent_partition(frame: ProblemFrame) -> ContractAssessment:
 
 
 def assess_contracts(frame: ProblemFrame) -> tuple[ContractAssessment, ...]:
-    """Return deterministic diagnostic assessments; never admits serving."""
+    """Return deterministic diagnostic assessments; never admits serving.
+
+    Dispatch order:
+    1. ``decrease_to_fraction`` — triggered by relation type presence in
+       ``frame.bound_relations``.  Routes to ``assess_fraction_decrease``.
+       Registry key: ``_CONTRACT_REGISTRY["fraction_decrease"]``.
+    2. ``percent_partition`` — triggered by process-frame names ``partition``
+       or ``consumption``.  Routes to ``assess_percent_partition``.
+       Registry key: ``_CONTRACT_REGISTRY["percent_partition"]``.
+    3. ``container_packing`` / ``labor_rate`` — inline skeleton assessments;
+       not yet in the catalog registry (added to registry when obligations are
+       fully specified).
+
+    The registry provides catalog metadata for proposal traces; it does not
+    replace the structural logic inside each assess_* function.  See module
+    docstring for rationale.
+    """
     frame_names = {candidate.name for candidate in frame.process_frames}
     results: list[ContractAssessment] = []
+
+    # Registry-backed diagnostic families
     if any(relation.relation_type == "decrease_to_fraction" for relation in frame.bound_relations):
+        # Catalog: _CONTRACT_REGISTRY["fraction_decrease"]
         results.append(assess_fraction_decrease(frame))
     if frame_names & {"partition", "consumption"}:
+        # Catalog: _CONTRACT_REGISTRY["percent_partition"]
         results.append(assess_percent_partition(frame))
+
+    # Skeleton families not yet in the catalog registry
     if "container_packing" in frame_names and frame.bound_question_target is not None:
         roles = _roles(frame, "container_packing")
         missing = tuple(name for name in ("container", "content", "count_per") if name not in roles)

tests/test_construction_affordances.py

@@ -0,0 +1,141 @@
+import pytest
+from generate.construction_affordances import (
+    all_diagnostic_families,
+    lookup_family,
+    lookup_by_organ,
+    lookup_by_relation_type,
+    make_proposal,
+    ConstructionProposal,
+    _CATALOG,
+)
+from generate.kernel_facts import SourceSpan
+
+
+def test_catalog_entries_are_diagnostic_only_and_serving_forbidden() -> None:
+    families = all_diagnostic_families()
+    assert len(families) == 2
+    for family in families:
+        assert family.diagnostic_only is True
+        assert family.serving_allowed is False
+
+
+def test_catalog_ordering_is_deterministic() -> None:
+    families = all_diagnostic_families()
+    ids = [f.family_id for f in families]
+    # Check that they are sorted
+    assert ids == sorted(ids)
+    assert ids == [
+        "partition.percent_partition",
+        "proportional_change.decrease_to_fraction",
+    ]
+
+
+def test_lookups_correctness() -> None:
+    # 1. lookup_family
+    f1 = lookup_family("proportional_change.decrease_to_fraction")
+    assert f1 is not None
+    assert f1.family_id == "proportional_change.decrease_to_fraction"
+
+    f2 = lookup_family("partition.percent_partition")
+    assert f2 is not None
+    assert f2.family_id == "partition.percent_partition"
+
+    assert lookup_family("invalid_family_id") is None
+
+    # 2. lookup_by_organ
+    assert lookup_by_organ("fraction_decrease") is f1
+    assert lookup_by_organ("percent_partition") is f2
+    assert lookup_by_organ("invalid_organ") is None
+
+    # 3. lookup_by_relation_type
+    assert lookup_by_relation_type("decrease_to_fraction") is f1
+    assert lookup_by_relation_type("percent_of") is f2
+    assert lookup_by_relation_type("invalid_relation") is None
+
+
+def test_make_proposal_validation_and_status() -> None:
+    span = SourceSpan("test text", 0, 9)
+
+    # 1. Closed status (runnable = True)
+    prop_closed = make_proposal(
+        family_id="proportional_change.decrease_to_fraction",
+        evidence_spans=(span,),
+        assessment_runnable=True,
+        missing_roles=(),
+        active_hazards=(),
+    )
+    assert prop_closed.family_id == "proportional_change.decrease_to_fraction"
+    assert prop_closed.relation_type == "decrease_to_fraction"
+    assert prop_closed.candidate_organ == "fraction_decrease"
+    assert prop_closed.evidence_spans == (span,)
+    assert prop_closed.status == "closed"
+    assert prop_closed.missing_roles == ()
+    assert prop_closed.active_hazards == ()
+
+    # 2. Refused status (active hazards present)
+    prop_refused = make_proposal(
+        family_id="proportional_change.decrease_to_fraction",
+        evidence_spans=(span,),
+        assessment_runnable=False,
+        missing_roles=(),
+        active_hazards=("unbound_base_quantity",),
+    )
+    assert prop_refused.status == "refused"
+    assert prop_refused.active_hazards == ("unbound_base_quantity",)
+
+    # 3. Partial status (missing roles present, no active hazards)
+    prop_partial = make_proposal(
+        family_id="proportional_change.decrease_to_fraction",
+        evidence_spans=(span,),
+        assessment_runnable=False,
+        missing_roles=("base_quantity_unbound",),
+        active_hazards=(),
+    )
+    assert prop_partial.status == "partial"
+    assert prop_partial.missing_roles == ("base_quantity_unbound",)
+
+    # 4. Proposed status (not runnable, no missing roles, no active hazards)
+    prop_proposed = make_proposal(
+        family_id="proportional_change.decrease_to_fraction",
+        evidence_spans=(span,),
+        assessment_runnable=False,
+        missing_roles=(),
+        active_hazards=(),
+    )
+    assert prop_proposed.status == "proposed"
+
+    # 5. Invalid family_id raises KeyError
+    with pytest.raises(KeyError):
+        make_proposal(
+            family_id="invalid_family_id",
+            evidence_spans=(span,),
+            assessment_runnable=False,
+            missing_roles=(),
+            active_hazards=(),
+        )
+
+
+def test_construction_proposal_status_validation() -> None:
+    span = SourceSpan("test text", 0, 9)
+    # Valid status doesn't raise
+    ConstructionProposal(
+        family_id="proportional_change.decrease_to_fraction",
+        relation_type="decrease_to_fraction",
+        candidate_organ="fraction_decrease",
+        evidence_spans=(span,),
+        status="closed",
+        missing_roles=(),
+        active_hazards=(),
+    )
+
+    # Invalid status raises ValueError
+    with pytest.raises(ValueError, match="status must be one of"):
+        ConstructionProposal(
+            family_id="proportional_change.decrease_to_fraction",
+            relation_type="decrease_to_fraction",
+            candidate_organ="fraction_decrease",
+            evidence_spans=(span,),
+            status="invalid_status",
+            missing_roles=(),
+            active_hazards=(),
+        )

tests/test_problem_frame_contracts.py

@@ -107,3 +107,96 @@ def test_unequal_partition_confuser_is_not_runnable() -> None:
     assessment = assess_percent_partition(build_problem_frame(UNEQUAL_PARTITION_CONFUSER))
     assert not assessment.runnable
     assert "partition_subgroups_not_distinct" in assessment.missing_bindings or "percent_subgroup_links_incomplete" in assessment.missing_bindings
+
+
+def test_fraction_decrease_rejects_scale_zero() -> None:
+    case = (
+        "In one hour, Addison mountain's temperature will decrease to 0/4 of its temperature. "
+        "If the current temperature of the mountain is 84 degrees, what will the temperature "
+        "decrease by?"
+    )
+    assessment = assess_fraction_decrease(build_problem_frame(case))
+    assert not assessment.runnable
+    assert "scale_out_of_range" in assessment.missing_bindings
+
+
+def test_fraction_decrease_rejects_scale_one() -> None:
+    case = (
+        "In one hour, Addison mountain's temperature will decrease to 4/4 of its temperature. "
+        "If the current temperature of the mountain is 84 degrees, what will the temperature "
+        "decrease by?"
+    )
+    assessment = assess_fraction_decrease(build_problem_frame(case))
+    assert not assessment.runnable
+    assert "scale_out_of_range" in assessment.missing_bindings
+
+
+def test_fraction_decrease_rejects_scale_greater_than_one() -> None:
+    case = (
+        "In one hour, Addison mountain's temperature will decrease to 5/4 of its temperature. "
+        "If the current temperature of the mountain is 84 degrees, what will the temperature "
+        "decrease by?"
+    )
+    assessment = assess_fraction_decrease(build_problem_frame(case))
+    assert not assessment.runnable
+    assert "scale_out_of_range" in assessment.missing_bindings
+
+
+def test_multi_base_candidate_is_refused() -> None:
+    import dataclasses
+    case = (
+        "In one hour, Addison mountain's temperature will decrease to 3/4 of its temperature. "
+        "If the current temperature of the mountain is 84 degrees, what will the temperature "
+        "decrease by?"
+    )
+    frame = build_problem_frame(case)
+    relation = [r for r in frame.bound_relations if r.relation_type == "decrease_to_fraction"][0]
+    frame = dataclasses.replace(frame, bound_relations=(relation, relation))
+    assessment = assess_fraction_decrease(frame)
+    assert not assessment.runnable
+    assert "decrease_relation_ambiguous" in assessment.missing_bindings
+
+
+def test_state_entity_continuity_unproven_blocks_runnable() -> None:
+    import dataclasses
+    case = (
+        "In one hour, Addison mountain's temperature will decrease to 3/4 of its temperature. "
+        "If the current temperature of the mountain is 84 degrees, what will the temperature "
+        "decrease by?"
+    )
+    frame = build_problem_frame(case)
+    # Target "mention-0004" is "degrees" which does not match "temperature" (state_entity)
+    new_target = dataclasses.replace(frame.bound_question_target, target_mention_id="mention-0004")
+    frame = dataclasses.replace(frame, bound_question_target=new_target)
+    assessment = assess_fraction_decrease(frame)
+    assert not assessment.runnable
+    assert "state_entity_continuity_unproven" in assessment.missing_bindings
+
+
+def test_unit_continuity_unproven_blocks_runnable() -> None:
+    import dataclasses
+    case = (
+        "In one hour, Addison mountain's temperature will decrease to 3/4 of its temperature. "
+        "If the current temperature of the mountain is 84 degrees, what will the temperature "
+        "decrease by?"
+    )
+    frame = build_problem_frame(case)
+    relation = [r for r in frame.bound_relations if r.relation_type == "decrease_to_fraction"][0]
+    new_roles = []
+    for role in relation.roles:
+        if role.role == "unit":
+            new_roles.append(dataclasses.replace(role, target_id="mention-9999"))
+        else:
+            new_roles.append(role)
+    new_relation = dataclasses.replace(relation, roles=tuple(new_roles))
+    frame = dataclasses.replace(frame, bound_relations=(new_relation,))
+    assessment = assess_fraction_decrease(frame)
+    assert not assessment.runnable
+    assert "unit_continuity_unproven" in assessment.missing_bindings
+
+
+def test_unequal_partition_confuser_produces_specific_blocker() -> None:
+    assessment = assess_percent_partition(build_problem_frame(UNEQUAL_PARTITION_CONFUSER))
+    assert not assessment.runnable
+    assert "partition_subgroups_not_distinct" in assessment.missing_bindings
+    assert "percent_subgroup_links_incomplete" in assessment.missing_bindings