feat(detection-core): represent family-neutral semantic evidence

.kiro/specs/detection-core/tasks.md

@@ -34,7 +34,7 @@
   - _Requirements: 1.4, 10.4_
 
 - [ ] 2. Implement canonical semantic, provenance, and evidence contracts
-- [ ] 2.1 (P) Represent family-neutral semantic relations and observations
+- [x] 2.1 (P) Represent family-neutral semantic relations and observations
   - Cover registration, invocation, call, return, value transformation, operation effect, and constraint effect.
   - Preserve role, location, conditions, provenance, and independent complete, incomplete, or unresolved status.
   - Refuse conflicting complete candidates by producing explicit ambiguity rather than selecting one.

src/openultrasast/core/semantics.py

@@ -0,0 +1,425 @@
+"""Family-neutral semantic evidence contracts for detection core v2."""
+
+import math
+import re
+from collections.abc import Mapping, Sequence
+from dataclasses import dataclass
+from enum import Enum
+from types import MappingProxyType
+
+from openultrasast.core.canonical import ContentRef, JsonValue, content_digest, require_unique_identities
+
+SEMANTIC_RELATION_SCHEMA = "openultrasast.detection-core.semantic-relation.v2"
+OBSERVATION_SCHEMA = "openultrasast.detection-core.observation.v2"
+_DIGEST = re.compile(r"[0-9a-f]{64}")
+
+
+class SemanticContractError(ValueError):
+    pass
+
+
+class FieldKind(Enum):
+    TEXT = "text"
+    INTEGER = "integer"
+    NUMBER = "number"
+    BOOLEAN = "boolean"
+    TEXT_TUPLE = "text_tuple"
+    SOURCE_LOCATION = "source_location"
+
+
+class RelationKind(Enum):
+    REGISTRATION = "registration"
+    INVOCATION = "invocation"
+    CALL = "call"
+    RETURN = "return"
+    VALUE_TRANSFORMATION = "value_transformation"
+    OPERATION_EFFECT = "operation_effect"
+    CONSTRAINT_EFFECT = "constraint_effect"
+
+
+class RelationStatus(Enum):
+    COMPLETE = "complete"
+    INCOMPLETE = "incomplete"
+    UNRESOLVED = "unresolved"
+
+
+class ProvenanceKind(Enum):
+    PRODUCT_CODE = "product_code"
+    SEMANTIC_FACT = "semantic_fact"
+
+
+def _require_text(value: object, field: str) -> None:
+    if not isinstance(value, str) or not value:
+        raise SemanticContractError(f"{field} must be nonempty text")
+
+
+def _require_digest(value: object, field: str) -> None:
+    if not isinstance(value, str) or _DIGEST.fullmatch(value) is None:
+        raise SemanticContractError(f"{field} must be a full lowercase SHA-256 digest")
+
+
+def _require_enum(value: object, enum_type: type[Enum], field: str) -> None:
+    if not isinstance(value, enum_type):
+        raise SemanticContractError(f"{field} must be a {enum_type.__name__}")
+
+
+def _require_text_tuple(values: object, field: str) -> None:
+    if not isinstance(values, tuple) or not all(isinstance(value, str) and value for value in values):
+        raise SemanticContractError(f"{field} must be a tuple of nonempty text")
+    try:
+        require_unique_identities(values, kind=field)
+    except ValueError as exc:
+        raise SemanticContractError(str(exc)) from exc
+
+
+@dataclass(frozen=True)
+class SourceLocation:
+    path: str
+    line: int
+    column: int | None
+    symbol: str | None
+
+    def __post_init__(self) -> None:
+        _require_text(self.path, "path")
+        if isinstance(self.line, bool) or not isinstance(self.line, int) or self.line < 1:
+            raise SemanticContractError("line must be a positive integer")
+        if self.column is not None and (isinstance(self.column, bool) or not isinstance(self.column, int) or self.column < 0):
+            raise SemanticContractError("column must be a non-negative integer or None")
+        if self.symbol is not None:
+            _require_text(self.symbol, "symbol")
+
+
+@dataclass(frozen=True)
+class SemanticNode:
+    node_id: str
+    role: str
+    location: SourceLocation
+
+    def __post_init__(self) -> None:
+        _require_text(self.node_id, "node_id")
+        _require_text(self.role, "role")
+        if not isinstance(self.location, SourceLocation):
+            raise SemanticContractError("location must be a SourceLocation")
+
+
+def _location_value(location: SourceLocation) -> Mapping[str, JsonValue]:
+    return {"path": location.path, "line": location.line, "column": location.column, "symbol": location.symbol}
+
+
+def _node_value(node: SemanticNode) -> Mapping[str, JsonValue]:
+    return {"node_id": node.node_id, "role": node.role, "location": _location_value(node.location)}
+
+
+def _content_ref_value(reference: ContentRef) -> Mapping[str, JsonValue]:
+    return {
+        "artifact_id": reference.artifact_id,
+        "content_digest": reference.content_digest,
+        "media_type": reference.media_type,
+        "byte_length": reference.byte_length,
+        "retention_policy_digest": reference.retention_policy_digest,
+        "storage_receipt_digest": reference.storage_receipt_digest,
+    }
+
+
+@dataclass(frozen=True)
+class EvidenceProvenance:
+    kind: ProvenanceKind
+    source_content_digest: str
+    semantic_pack_digest: str | None
+    semantic_fact_id: str | None
+    fact_match: ContentRef | None
+
+    def __post_init__(self) -> None:
+        _require_enum(self.kind, ProvenanceKind, "kind")
+        _require_digest(self.source_content_digest, "source_content_digest")
+        if self.kind is ProvenanceKind.PRODUCT_CODE:
+            if any(value is not None for value in (self.semantic_pack_digest, self.semantic_fact_id, self.fact_match)):
+                raise SemanticContractError("product-code provenance forbids semantic fact fields")
+            return
+        if self.semantic_pack_digest is None:
+            raise SemanticContractError("semantic_pack_digest is required")
+        _require_digest(self.semantic_pack_digest, "semantic_pack_digest")
+        if self.semantic_fact_id is None:
+            raise SemanticContractError("semantic_fact_id is required")
+        _require_text(self.semantic_fact_id, "semantic_fact_id")
+        if not isinstance(self.fact_match, ContentRef):
+            raise SemanticContractError("fact_match is required and must be a ContentRef")
+
+
+def _provenance_value(provenance: EvidenceProvenance) -> Mapping[str, JsonValue]:
+    fact_match: JsonValue = None if provenance.fact_match is None else _content_ref_value(provenance.fact_match)
+    return {
+        "kind": provenance.kind.value,
+        "source_content_digest": provenance.source_content_digest,
+        "semantic_pack_digest": provenance.semantic_pack_digest,
+        "semantic_fact_id": provenance.semantic_fact_id,
+        "fact_match": fact_match,
+    }
+
+
+def _source_location_field(value: object) -> bool:
+    if not isinstance(value, Mapping) or set(value) != {"path", "line", "column", "symbol"}:
+        return False
+    path, line, column, symbol = value["path"], value["line"], value["column"], value["symbol"]
+    return (
+        isinstance(path, str)
+        and bool(path)
+        and isinstance(line, int)
+        and not isinstance(line, bool)
+        and line >= 1
+        and (column is None or (isinstance(column, int) and not isinstance(column, bool) and column >= 0))
+        and (symbol is None or (isinstance(symbol, str) and bool(symbol)))
+    )
+
+
+def _valid_field_value(kind: FieldKind, value: object) -> bool:
+    if kind is FieldKind.TEXT:
+        return isinstance(value, str)
+    if kind is FieldKind.INTEGER:
+        return isinstance(value, int) and not isinstance(value, bool)
+    if kind is FieldKind.NUMBER:
+        return isinstance(value, (int, float)) and not isinstance(value, bool) and math.isfinite(value)
+    if kind is FieldKind.BOOLEAN:
+        return isinstance(value, bool)
+    if kind is FieldKind.TEXT_TUPLE:
+        return isinstance(value, tuple) and all(isinstance(item, str) for item in value)
+    return _source_location_field(value)
+
+
+def _freeze_json(value: JsonValue) -> JsonValue:
+    if isinstance(value, Mapping):
+        return MappingProxyType({key: _freeze_json(item) for key, item in value.items()})
+    if isinstance(value, tuple):
+        return tuple(_freeze_json(item) for item in value)
+    return value
+
+
+@dataclass(frozen=True)
+class FieldValue:
+    name: str
+    kind: FieldKind
+    value: JsonValue
+
+    def __post_init__(self) -> None:
+        _require_text(self.name, "name")
+        _require_enum(self.kind, FieldKind, "kind")
+        frozen = _freeze_json(self.value)
+        if not _valid_field_value(self.kind, frozen):
+            raise SemanticContractError(f"value does not match FieldKind.{self.kind.name}")
+        object.__setattr__(self, "value", frozen)
+
+
+def _field_value(field: FieldValue) -> Mapping[str, JsonValue]:
+    return {"name": field.name, "kind": field.kind.value, "value": field.value}
+
+
+def _relation_payload(relation: "SemanticRelation") -> Mapping[str, JsonValue]:
+    return {
+        "schema_version": SEMANTIC_RELATION_SCHEMA,
+        "kind": relation.kind.value,
+        "role": relation.role,
+        "source": _node_value(relation.source),
+        "target": _node_value(relation.target),
+        "location": _location_value(relation.location),
+        "status": relation.status.value,
+        "conditions": relation.conditions,
+        "reasons": relation.reasons,
+        "provenance": _provenance_value(relation.provenance),
+    }
+
+
+@dataclass(frozen=True)
+class SemanticRelation:
+    relation_id: str
+    kind: RelationKind
+    role: str
+    source: SemanticNode
+    target: SemanticNode
+    location: SourceLocation
+    status: RelationStatus
+    conditions: tuple[str, ...]
+    reasons: tuple[str, ...]
+    provenance: EvidenceProvenance
+
+    def __post_init__(self) -> None:
+        _validate_relation_fields(self, allow_empty_id=True)
+        expected = content_digest(_relation_payload(self))
+        if not self.relation_id:
+            object.__setattr__(self, "relation_id", expected)
+        elif self.relation_id != expected:
+            raise SemanticContractError("relation_id does not match canonical relation fields")
+
+
+def _validate_relation_fields(relation: SemanticRelation, *, allow_empty_id: bool = False) -> None:
+    if relation.relation_id or not allow_empty_id:
+        _require_digest(relation.relation_id, "relation_id")
+    _require_enum(relation.kind, RelationKind, "kind")
+    _require_text(relation.role, "role")
+    if not isinstance(relation.source, SemanticNode) or not isinstance(relation.target, SemanticNode):
+        raise SemanticContractError("source and target must be SemanticNode values")
+    if not isinstance(relation.location, SourceLocation):
+        raise SemanticContractError("location must be a SourceLocation")
+    _require_enum(relation.status, RelationStatus, "status")
+    _require_text_tuple(relation.conditions, "condition")
+    _require_text_tuple(relation.reasons, "reason")
+    if relation.status is RelationStatus.COMPLETE and relation.reasons:
+        raise SemanticContractError("complete relation must not carry incompleteness reasons")
+    if relation.status is not RelationStatus.COMPLETE and not relation.reasons:
+        raise SemanticContractError("incomplete or unresolved relation requires a reason")
+    if not isinstance(relation.provenance, EvidenceProvenance):
+        raise SemanticContractError("provenance must be EvidenceProvenance")
+
+
+def make_relation(
+    *,
+    kind: RelationKind,
+    role: str,
+    source: SemanticNode,
+    target: SemanticNode,
+    location: SourceLocation,
+    status: RelationStatus,
+    conditions: tuple[str, ...],
+    reasons: tuple[str, ...],
+    provenance: EvidenceProvenance,
+) -> SemanticRelation:
+    return SemanticRelation("", kind, role, source, target, location, status, conditions, reasons, provenance)
+
+
+def relation_from_conditions(
+    *,
+    kind: RelationKind,
+    role: str,
+    source: SemanticNode,
+    target: SemanticNode,
+    location: SourceLocation,
+    declared_conditions: tuple[str, ...],
+    unmet_conditions: tuple[str, ...],
+    provenance: EvidenceProvenance,
+) -> SemanticRelation:
+    _require_text_tuple(declared_conditions, "declared condition")
+    _require_text_tuple(unmet_conditions, "unmet condition")
+    if not set(unmet_conditions).issubset(declared_conditions):
+        raise SemanticContractError("unmet conditions must be declared")
+    status = RelationStatus.INCOMPLETE if unmet_conditions else RelationStatus.COMPLETE
+    reasons = tuple(f"unmet_condition:{condition}" for condition in unmet_conditions)
+    return make_relation(
+        kind=kind,
+        role=role,
+        source=source,
+        target=target,
+        location=location,
+        status=status,
+        conditions=declared_conditions,
+        reasons=reasons,
+        provenance=provenance,
+    )
+
+
+def _same_slot(candidate: SemanticRelation, first: SemanticRelation) -> bool:
+    return all(getattr(candidate, field) == getattr(first, field) for field in ("kind", "role", "source", "target", "location"))
+
+
+def _candidate_provenance_reason(candidate: SemanticRelation) -> str:
+    provenance = candidate.provenance
+    match = "-" if provenance.fact_match is None else provenance.fact_match.content_digest
+    return ":".join(
+        (
+            "conflicting_candidate_provenance",
+            content_digest(_provenance_value(provenance)),
+            provenance.kind.value,
+            provenance.semantic_pack_digest or "-",
+            provenance.semantic_fact_id or "-",
+            match,
+        )
+    )
+
+
+def resolve_relation_candidates(candidates: Sequence[SemanticRelation]) -> SemanticRelation:
+    if not candidates:
+        raise SemanticContractError("at least one relation candidate is required")
+    if not all(isinstance(candidate, SemanticRelation) for candidate in candidates):
+        raise SemanticContractError("every candidate must be a SemanticRelation")
+    first = candidates[0]
+    if not all(_same_slot(candidate, first) for candidate in candidates):
+        raise SemanticContractError("relation candidates must describe the same semantic slot")
+    try:
+        require_unique_identities(tuple(candidate.relation_id for candidate in candidates), kind="candidate")
+    except ValueError as exc:
+        raise SemanticContractError(str(exc)) from exc
+    complete = [candidate for candidate in candidates if candidate.status is RelationStatus.COMPLETE]
+    if len(complete) == 1:
+        return complete[0]
+    if len(candidates) == 1:
+        return first
+    ordered = sorted(candidates, key=lambda candidate: candidate.relation_id)
+    anchor = ordered[0]
+    conditions = tuple(sorted({condition for candidate in ordered for condition in candidate.conditions}))
+    reasons = (
+        tuple(f"conflicting_complete_candidate:{candidate.relation_id}" for candidate in ordered)
+        + tuple(sorted({_candidate_provenance_reason(candidate) for candidate in ordered}))
+        + (f"ambiguity_provenance_anchor:{anchor.relation_id}",)
+    )
+    return make_relation(
+        kind=anchor.kind,
+        role=anchor.role,
+        source=anchor.source,
+        target=anchor.target,
+        location=anchor.location,
+        status=RelationStatus.UNRESOLVED,
+        conditions=conditions,
+        reasons=reasons,
+        provenance=anchor.provenance,
+    )
+
+
+def _observation_payload(observation: "Observation") -> Mapping[str, JsonValue]:
+    return {
+        "schema_version": OBSERVATION_SCHEMA,
+        "role": observation.role,
+        "location": _location_value(observation.location),
+        "fields": tuple(_field_value(field) for field in observation.fields),
+        "status": observation.status.value,
+        "provenance": _provenance_value(observation.provenance),
+    }
+
+
+@dataclass(frozen=True)
+class Observation:
+    observation_id: str
+    role: str
+    location: SourceLocation
+    fields: tuple[FieldValue, ...]
+    status: RelationStatus
+    provenance: EvidenceProvenance
+
+    def __post_init__(self) -> None:
+        if self.observation_id:
+            _require_digest(self.observation_id, "observation_id")
+        _require_text(self.role, "role")
+        if not isinstance(self.location, SourceLocation):
+            raise SemanticContractError("location must be a SourceLocation")
+        if not isinstance(self.fields, tuple) or not all(isinstance(field, FieldValue) for field in self.fields):
+            raise SemanticContractError("fields must be a tuple of FieldValue values")
+        try:
+            require_unique_identities(tuple(field.name for field in self.fields), kind="field")
+        except ValueError as exc:
+            raise SemanticContractError(str(exc)) from exc
+        _require_enum(self.status, RelationStatus, "status")
+        if not isinstance(self.provenance, EvidenceProvenance):
+            raise SemanticContractError("provenance must be EvidenceProvenance")
+        expected = content_digest(_observation_payload(self))
+        if not self.observation_id:
+            object.__setattr__(self, "observation_id", expected)
+        elif self.observation_id != expected:
+            raise SemanticContractError("observation_id does not match canonical observation fields")
+
+
+def make_observation(
+    *,
+    role: str,
+    location: SourceLocation,
+    fields: tuple[FieldValue, ...],
+    status: RelationStatus,
+    provenance: EvidenceProvenance,
+) -> Observation:
+    return Observation("", role, location, fields, status, provenance)

tests/test_core_semantics.py

@@ -0,0 +1,400 @@
+"""Family-neutral semantic evidence contracts (Req 1.2, 4.1-4.3, 5.2)."""
+
+from __future__ import annotations
+
+from collections.abc import Mapping, MutableMapping
+from dataclasses import FrozenInstanceError, replace
+from enum import Enum
+from typing import cast
+
+import pytest
+from detection_core_fixtures import stored_artifact
+
+import openultrasast.core.canonical as canonical
+import openultrasast.core.semantics as semantics
+
+
+def _location(line: int = 7) -> semantics.SourceLocation:
+    return semantics.SourceLocation(path="src/app.py", line=line, column=3, symbol="handle")
+
+
+def _node(node_id: str, role: str) -> semantics.SemanticNode:
+    return semantics.SemanticNode(node_id=node_id, role=role, location=_location())
+
+
+def _product_provenance() -> semantics.EvidenceProvenance:
+    return semantics.EvidenceProvenance(
+        kind=semantics.ProvenanceKind.PRODUCT_CODE,
+        source_content_digest="1" * 64,
+        semantic_pack_digest=None,
+        semantic_fact_id=None,
+        fact_match=None,
+    )
+
+
+def _fact_provenance() -> semantics.EvidenceProvenance:
+    reference, _ = stored_artifact(b'{"matched":true}')
+    return semantics.EvidenceProvenance(
+        kind=semantics.ProvenanceKind.SEMANTIC_FACT,
+        source_content_digest="2" * 64,
+        semantic_pack_digest="3" * 64,
+        semantic_fact_id="express.route.registration",
+        fact_match=reference,
+    )
+
+
+def _named_fact_provenance(pack: str, fact: str) -> semantics.EvidenceProvenance:
+    reference, _ = stored_artifact(fact.encode())
+    return semantics.EvidenceProvenance(
+        kind=semantics.ProvenanceKind.SEMANTIC_FACT,
+        source_content_digest="4" * 64,
+        semantic_pack_digest=pack,
+        semantic_fact_id=fact,
+        fact_match=reference,
+    )
+
+
+def _relation(
+    *,
+    kind_name: str = "CALL",
+    status_name: str = "COMPLETE",
+    target_id: str = "target",
+    conditions: tuple[str, ...] = (),
+    reasons: tuple[str, ...] = (),
+    provenance: semantics.EvidenceProvenance | None = None,
+) -> semantics.SemanticRelation:
+    return semantics.make_relation(
+        kind=getattr(semantics.RelationKind, kind_name),
+        role="framework_transition",
+        source=_node("source", "caller"),
+        target=_node(target_id, "callee"),
+        location=_location(),
+        status=getattr(semantics.RelationStatus, status_name),
+        conditions=conditions,
+        reasons=reasons,
+        provenance=_product_provenance() if provenance is None else provenance,
+    )
+
+
+@pytest.mark.parametrize(
+    "kind_name",
+    [
+        "REGISTRATION",
+        "INVOCATION",
+        "CALL",
+        "RETURN",
+        "VALUE_TRANSFORMATION",
+        "OPERATION_EFFECT",
+        "CONSTRAINT_EFFECT",
+    ],
+)
+def test_every_relation_kind_has_a_canonical_identity(kind_name: str) -> None:
+    relation = _relation(kind_name=kind_name)
+    same = _relation(kind_name=kind_name)
+
+    assert relation.kind.value == kind_name.lower()
+    assert relation.relation_id == same.relation_id
+    assert len(relation.relation_id) == 64
+    assert relation.role == "framework_transition"
+    assert relation.location == _location()
+    assert relation.provenance == _product_provenance()
+
+
+@pytest.mark.parametrize(
+    ("status_name", "reasons"),
+    [
+        ("COMPLETE", ()),
+        ("INCOMPLETE", ("unmet_condition:authenticated",)),
+        ("UNRESOLVED", ("ambiguous_framework_match",)),
+    ],
+)
+def test_relation_status_is_independent_and_canonical(status_name: str, reasons: tuple[str, ...]) -> None:
+    relation = _relation(status_name=status_name, reasons=reasons)
+
+    assert relation.status.value == status_name.lower()
+    assert relation.reasons == reasons
+    assert relation.relation_id == _relation(status_name=status_name, reasons=reasons).relation_id
+
+
+def test_relation_identity_preserves_condition_order_and_rejects_tampering() -> None:
+    left = _relation(conditions=("registered", "authenticated"))
+    right = _relation(conditions=("authenticated", "registered"))
+
+    assert left.relation_id != right.relation_id
+    with pytest.raises(semantics.SemanticContractError, match="relation_id"):
+        replace(left, relation_id="0" * 64)
+
+
+def test_unmet_declared_conditions_make_relation_incomplete() -> None:
+    relation = semantics.relation_from_conditions(
+        kind=semantics.RelationKind.CONSTRAINT_EFFECT,
+        role="authorization_constraint",
+        source=_node("request", "request"),
+        target=_node("resource", "resource"),
+        location=_location(),
+        declared_conditions=("authenticated", "owns_resource"),
+        unmet_conditions=("owns_resource",),
+        provenance=_product_provenance(),
+    )
+
+    assert relation.status is semantics.RelationStatus.INCOMPLETE
+    assert relation.conditions == ("authenticated", "owns_resource")
+    assert relation.reasons == ("unmet_condition:owns_resource",)
+
+
+def test_conflicting_complete_candidates_produce_stable_explicit_ambiguity() -> None:
+    first = _relation(conditions=("framework:v1",))
+    second = _relation(conditions=("framework:v2",))
+
+    forward = semantics.resolve_relation_candidates((first, second))
+    reverse = semantics.resolve_relation_candidates((second, first))
+
+    assert forward.status is semantics.RelationStatus.UNRESOLVED
+    assert forward.relation_id == reverse.relation_id
+    assert forward.conditions == ("framework:v1", "framework:v2")
+    for identity in (first.relation_id, second.relation_id):
+        assert f"conflicting_complete_candidate:{identity}" in forward.reasons
+    assert any(reason.startswith("ambiguity_provenance_anchor:") for reason in forward.reasons)
+    assert forward not in (first, second)
+
+
+def test_distinct_reviewed_fact_candidates_produce_order_independent_ambiguity() -> None:
+    first_provenance = _named_fact_provenance("5" * 64, "express.route.v1")
+    second_provenance = _named_fact_provenance("6" * 64, "express.route.v2")
+    first = _relation(conditions=("framework:v1",), provenance=first_provenance)
+    second = _relation(conditions=("framework:v2",), provenance=second_provenance)
+
+    forward = semantics.resolve_relation_candidates((first, second))
+    reverse = semantics.resolve_relation_candidates((second, first))
+
+    assert forward.status is semantics.RelationStatus.UNRESOLVED
+    assert forward.relation_id == reverse.relation_id
+    assert forward.provenance == reverse.provenance
+    assert any(reason.startswith("ambiguity_provenance_anchor:") for reason in forward.reasons)
+    for candidate in (first, second):
+        assert f"conflicting_complete_candidate:{candidate.relation_id}" in forward.reasons
+        provenance = candidate.provenance
+        assert provenance.semantic_pack_digest is not None
+        assert provenance.semantic_fact_id is not None
+        assert provenance.fact_match is not None
+        assert any(
+            provenance.semantic_pack_digest in reason
+            and provenance.semantic_fact_id in reason
+            and provenance.fact_match.content_digest in reason
+            for reason in forward.reasons
+        )
+
+
+def test_candidate_resolution_returns_the_only_complete_candidate() -> None:
+    complete = _relation()
+    incomplete = _relation(status_name="INCOMPLETE", reasons=("missing_fact",))
+
+    assert semantics.resolve_relation_candidates((incomplete, complete)) is complete
+
+
+def test_candidate_resolution_refuses_unrelated_relation_slots() -> None:
+    with pytest.raises(semantics.SemanticContractError, match="same semantic slot"):
+        semantics.resolve_relation_candidates((_relation(), _relation(target_id="other")))
+
+
+def test_product_provenance_forbids_semantic_fact_fields() -> None:
+    reference, _ = stored_artifact(b"match")
+    with pytest.raises(semantics.SemanticContractError, match="forbids semantic fact"):
+        semantics.EvidenceProvenance(
+            kind=semantics.ProvenanceKind.PRODUCT_CODE,
+            source_content_digest="1" * 64,
+            semantic_pack_digest="2" * 64,
+            semantic_fact_id="fact",
+            fact_match=reference,
+        )
+
+
+@pytest.mark.parametrize("missing", ["semantic_pack_digest", "semantic_fact_id", "fact_match"])
+def test_semantic_fact_provenance_requires_all_fact_identity_fields(missing: str) -> None:
+    reference, _ = stored_artifact(b"match")
+    values: dict[str, object] = {
+        "semantic_pack_digest": "2" * 64,
+        "semantic_fact_id": "fact",
+        "fact_match": reference,
+    }
+    values[missing] = None
+
+    with pytest.raises(semantics.SemanticContractError, match=missing):
+        semantics.EvidenceProvenance(
+            kind=semantics.ProvenanceKind.SEMANTIC_FACT,
+            source_content_digest="1" * 64,
+            semantic_pack_digest=cast(str | None, values["semantic_pack_digest"]),
+            semantic_fact_id=cast(str | None, values["semantic_fact_id"]),
+            fact_match=cast(canonical.ContentRef | None, values["fact_match"]),
+        )
+
+
+def test_semantic_fact_identity_changes_relation_identity() -> None:
+    product = _relation()
+    fact = semantics.make_relation(
+        kind=product.kind,
+        role=product.role,
+        source=product.source,
+        target=product.target,
+        location=product.location,
+        status=product.status,
+        conditions=product.conditions,
+        reasons=product.reasons,
+        provenance=_fact_provenance(),
+    )
+
+    assert fact.relation_id != product.relation_id
+
+
+@pytest.mark.parametrize(
+    ("kind_name", "value"),
+    [
+        ("TEXT", "query"),
+        ("INTEGER", 7),
+        ("NUMBER", 2.5),
+        ("BOOLEAN", True),
+        ("TEXT_TUPLE", ("read", "write")),
+        ("SOURCE_LOCATION", {"path": "src/app.py", "line": 7, "column": 3, "symbol": "handle"}),
+    ],
+)
+def test_observation_fields_have_closed_typed_values(kind_name: str, value: object) -> None:
+    field = semantics.FieldValue(name="observed", kind=getattr(semantics.FieldKind, kind_name), value=cast(canonical.JsonValue, value))
+    observation = semantics.make_observation(
+        role="operation",
+        location=_location(),
+        fields=(field,),
+        status=semantics.RelationStatus.COMPLETE,
+        provenance=_product_provenance(),
+    )
+
+    assert observation.fields == (field,)
+    assert (
+        observation.observation_id
+        == semantics.make_observation(
+            role="operation",
+            location=_location(),
+            fields=(field,),
+            status=semantics.RelationStatus.COMPLETE,
+            provenance=_product_provenance(),
+        ).observation_id
+    )
+
+
+def test_field_value_defensively_freezes_caller_mapping() -> None:
+    caller_value: dict[str, canonical.JsonValue] = {
+        "path": "src/original.py",
+        "line": 3,
+        "column": None,
+        "symbol": "original",
+    }
+    field = semantics.FieldValue("location", semantics.FieldKind.SOURCE_LOCATION, caller_value)
+    observation = semantics.make_observation(
+        role="operation",
+        location=_location(),
+        fields=(field,),
+        status=semantics.RelationStatus.COMPLETE,
+        provenance=_product_provenance(),
+    )
+
+    caller_value["path"] = "src/mutated.py"
+    exposed = cast(MutableMapping[str, canonical.JsonValue], field.value)
+    with pytest.raises(TypeError):
+        exposed["path"] = "src/also-mutated.py"
+
+    frozen_value = cast(Mapping[str, canonical.JsonValue], field.value)
+    assert frozen_value["path"] == "src/original.py"
+    assert (
+        observation.observation_id
+        == semantics.make_observation(
+            role="operation",
+            location=_location(),
+            fields=(field,),
+            status=semantics.RelationStatus.COMPLETE,
+            provenance=_product_provenance(),
+        ).observation_id
+    )
+
+
+def test_observation_preserves_field_order_and_all_statuses() -> None:
+    first = semantics.FieldValue("first", semantics.FieldKind.TEXT, "one")
+    second = semantics.FieldValue("second", semantics.FieldKind.INTEGER, 2)
+    identities = []
+    for status in semantics.RelationStatus:
+        observation = semantics.make_observation(
+            role="operation",
+            location=_location(),
+            fields=(first, second),
+            status=status,
+            provenance=_product_provenance(),
+        )
+        reversed_fields = semantics.make_observation(
+            role="operation",
+            location=_location(),
+            fields=(second, first),
+            status=status,
+            provenance=_product_provenance(),
+        )
+        assert observation.observation_id != reversed_fields.observation_id
+        identities.append(observation.observation_id)
+    assert len(set(identities)) == 3
+
+
+def test_observation_refuses_duplicate_field_names() -> None:
+    duplicate = semantics.FieldValue("same", semantics.FieldKind.TEXT, "value")
+    with pytest.raises(semantics.SemanticContractError, match="duplicate field"):
+        semantics.make_observation(
+            role="operation",
+            location=_location(),
+            fields=(duplicate, duplicate),
+            status=semantics.RelationStatus.COMPLETE,
+            provenance=_product_provenance(),
+        )
+
+
+@pytest.mark.parametrize(
+    ("kind_name", "value"),
+    [
+        ("TEXT", 1),
+        ("INTEGER", True),
+        ("NUMBER", float("nan")),
+        ("BOOLEAN", "true"),
+        ("TEXT_TUPLE", ("valid", 2)),
+        ("SOURCE_LOCATION", {"path": "src/app.py"}),
+    ],
+)
+def test_field_kind_refuses_wrong_runtime_shape(kind_name: str, value: object) -> None:
+    with pytest.raises(semantics.SemanticContractError, match="value"):
+        semantics.FieldValue("observed", getattr(semantics.FieldKind, kind_name), cast(canonical.JsonValue, value))
+
+
+@pytest.mark.parametrize(
+    ("path", "line", "column", "symbol"),
+    [("", 1, None, None), ("src/app.py", 0, None, None), ("src/app.py", 1, -1, None), ("src/app.py", 1, None, "")],
+)
+def test_source_location_refuses_invalid_runtime_values(path: str, line: int, column: int | None, symbol: str | None) -> None:
+    with pytest.raises(semantics.SemanticContractError):
+        semantics.SourceLocation(path=path, line=line, column=column, symbol=symbol)
+
+
+def test_unknown_enum_values_are_refused_at_runtime() -> None:
+    class Unknown(Enum):
+        VALUE = "call"
+
+    with pytest.raises(semantics.SemanticContractError, match="RelationKind"):
+        semantics.make_relation(
+            kind=cast(semantics.RelationKind, Unknown.VALUE),
+            role="role",
+            source=_node("source", "source"),
+            target=_node("target", "target"),
+            location=_location(),
+            status=semantics.RelationStatus.COMPLETE,
+            conditions=(),
+            reasons=(),
+            provenance=_product_provenance(),
+        )
+
+
+def test_semantic_contracts_are_frozen() -> None:
+    relation = _relation()
+    with pytest.raises(FrozenInstanceError):
+        relation.__setattr__("role", "mutated")