diff --git a/docs/tech-specs/ontorag.md b/docs/tech-specs/ontorag.md
index 86a3cd19..460e72ba 100644
--- a/docs/tech-specs/ontorag.md
+++ b/docs/tech-specs/ontorag.md
@@ -278,7 +278,7 @@ The system uses **FAISS (Facebook AI Similarity Search)** with IndexFlatIP for e
 3. **Similarity Search**:
    - For each text segment embedding, search the vector store
    - Retrieve top-k (e.g., 10) most similar ontology elements
-   - Apply similarity threshold (e.g., 0.7) to filter weak matches
+   - Apply similarity threshold (e.g., 0.3) to filter weak matches
    - Aggregate results across all segments, tracking match frequencies
 
 4. **Dependency Resolution**:
diff --git a/tests/unit/test_extract/test_ontology/test_triple_converter_validation.py b/tests/unit/test_extract/test_ontology/test_triple_converter_validation.py
new file mode 100644
index 00000000..195e8adf
--- /dev/null
+++ b/tests/unit/test_extract/test_ontology/test_triple_converter_validation.py
@@ -0,0 +1,389 @@
+"""
+Tests for TripleConverter domain/range enforcement and
+OntologySelector bypass for small ontologies.
+
+Covers fixes for #908 (bypass_selector_below) and #920 (domain/range validation).
+"""
+
+import pytest
+from unittest.mock import Mock, AsyncMock
+
+from trustgraph.extract.kg.ontology.triple_converter import TripleConverter
+from trustgraph.extract.kg.ontology.ontology_selector import (
+    OntologySelector,
+    OntologySubset,
+)
+from trustgraph.extract.kg.ontology.ontology_loader import (
+    Ontology,
+    OntologyClass,
+    OntologyProperty,
+)
+from trustgraph.extract.kg.ontology.simplified_parser import (
+    Relationship,
+    Attribute,
+)
+from trustgraph.extract.kg.ontology.text_processor import TextSegment
+
+
+# ---------------------------------------------------------------------------
+# Fixtures
+# ---------------------------------------------------------------------------
+
+@pytest.fixture
+def ontology_subset():
+    """Ontology subset with classes, hierarchy, and constrained properties."""
+    return OntologySubset(
+        ontology_id="test",
+        classes={
+            "Person": {
+                "uri": "http://example.org/Person",
+                "type": "owl:Class",
+                "labels": [{"value": "Person"}],
+                "subclass_of": None,
+            },
+            "Employee": {
+                "uri": "http://example.org/Employee",
+                "type": "owl:Class",
+                "labels": [{"value": "Employee"}],
+                "subclass_of": "Person",
+            },
+            "Manager": {
+                "uri": "http://example.org/Manager",
+                "type": "owl:Class",
+                "labels": [{"value": "Manager"}],
+                "subclass_of": "Employee",
+            },
+            "Company": {
+                "uri": "http://example.org/Company",
+                "type": "owl:Class",
+                "labels": [{"value": "Company"}],
+                "subclass_of": None,
+            },
+            "Product": {
+                "uri": "http://example.org/Product",
+                "type": "owl:Class",
+                "labels": [{"value": "Product"}],
+                "subclass_of": None,
+            },
+        },
+        object_properties={
+            "worksFor": {
+                "uri": "http://example.org/worksFor",
+                "type": "owl:ObjectProperty",
+                "labels": [{"value": "works for"}],
+                "domain": "Person",
+                "range": "Company",
+            },
+            "manages": {
+                "uri": "http://example.org/manages",
+                "type": "owl:ObjectProperty",
+                "labels": [{"value": "manages"}],
+                "domain": "Manager",
+                "range": "Employee",
+            },
+            "relatedTo": {
+                "uri": "http://example.org/relatedTo",
+                "type": "owl:ObjectProperty",
+                "labels": [{"value": "related to"}],
+                "domain": None,
+                "range": None,
+            },
+        },
+        datatype_properties={
+            "employeeId": {
+                "uri": "http://example.org/employeeId",
+                "type": "owl:DatatypeProperty",
+                "labels": [{"value": "employee ID"}],
+                "domain": "Employee",
+            },
+            "description": {
+                "uri": "http://example.org/description",
+                "type": "owl:DatatypeProperty",
+                "labels": [{"value": "description"}],
+                "domain": None,
+            },
+        },
+        metadata={"name": "Test Ontology"},
+    )
+
+
+@pytest.fixture
+def converter(ontology_subset):
+    return TripleConverter(ontology_subset=ontology_subset, ontology_id="test")
+
+
+# ---------------------------------------------------------------------------
+# Domain/range enforcement — relationships
+# ---------------------------------------------------------------------------
+
+class TestRelationshipDomainRange:
+
+    def test_valid_domain_and_range(self, converter):
+        rel = Relationship(
+            subject="Alice", subject_type="Person",
+            relation="worksFor",
+            object="Acme Corp", object_type="Company",
+        )
+        triple = converter.convert_relationship(rel)
+        assert triple is not None
+
+    def test_domain_violation_rejected(self, converter):
+        rel = Relationship(
+            subject="Widget", subject_type="Product",
+            relation="worksFor",
+            object="Acme Corp", object_type="Company",
+        )
+        assert converter.convert_relationship(rel) is None
+
+    def test_range_violation_rejected(self, converter):
+        rel = Relationship(
+            subject="Alice", subject_type="Person",
+            relation="worksFor",
+            object="Widget", object_type="Product",
+        )
+        assert converter.convert_relationship(rel) is None
+
+    def test_both_domain_and_range_violated(self, converter):
+        rel = Relationship(
+            subject="Widget", subject_type="Product",
+            relation="worksFor",
+            object="Gadget", object_type="Product",
+        )
+        assert converter.convert_relationship(rel) is None
+
+
+# ---------------------------------------------------------------------------
+# Subclass acceptance
+# ---------------------------------------------------------------------------
+
+class TestSubclassAcceptance:
+
+    def test_direct_subclass_matches_domain(self, converter):
+        """Employee is subclass of Person; worksFor domain is Person."""
+        rel = Relationship(
+            subject="Bob", subject_type="Employee",
+            relation="worksFor",
+            object="Acme Corp", object_type="Company",
+        )
+        assert converter.convert_relationship(rel) is not None
+
+    def test_transitive_subclass_matches_domain(self, converter):
+        """Manager → Employee → Person; worksFor domain is Person."""
+        rel = Relationship(
+            subject="Carol", subject_type="Manager",
+            relation="worksFor",
+            object="Acme Corp", object_type="Company",
+        )
+        assert converter.convert_relationship(rel) is not None
+
+    def test_subclass_matches_range(self, converter):
+        """manages range is Employee; Manager is subclass of Employee."""
+        rel = Relationship(
+            subject="Carol", subject_type="Manager",
+            relation="manages",
+            object="Dave", object_type="Manager",
+        )
+        assert converter.convert_relationship(rel) is not None
+
+    def test_superclass_does_not_match_subclass_constraint(self, converter):
+        """manages domain is Manager; Person is NOT a subclass of Manager."""
+        rel = Relationship(
+            subject="Alice", subject_type="Person",
+            relation="manages",
+            object="Bob", object_type="Employee",
+        )
+        assert converter.convert_relationship(rel) is None
+
+
+# ---------------------------------------------------------------------------
+# Polymorphic properties (no domain/range)
+# ---------------------------------------------------------------------------
+
+class TestPolymorphicProperties:
+
+    def test_no_domain_no_range_allows_anything(self, converter):
+        rel = Relationship(
+            subject="Alice", subject_type="Person",
+            relation="relatedTo",
+            object="Acme Corp", object_type="Company",
+        )
+        assert converter.convert_relationship(rel) is not None
+
+    def test_polymorphic_with_unrelated_types(self, converter):
+        rel = Relationship(
+            subject="Widget", subject_type="Product",
+            relation="relatedTo",
+            object="Bob", object_type="Employee",
+        )
+        assert converter.convert_relationship(rel) is not None
+
+
+# ---------------------------------------------------------------------------
+# Datatype property domain enforcement
+# ---------------------------------------------------------------------------
+
+class TestAttributeDomainValidation:
+
+    def test_valid_domain(self, converter):
+        attr = Attribute(
+            entity="Bob", entity_type="Employee",
+            attribute="employeeId", value="E-1234",
+        )
+        assert converter.convert_attribute(attr) is not None
+
+    def test_subclass_matches_domain(self, converter):
+        """Manager is subclass of Employee; employeeId domain is Employee."""
+        attr = Attribute(
+            entity="Carol", entity_type="Manager",
+            attribute="employeeId", value="M-5678",
+        )
+        assert converter.convert_attribute(attr) is not None
+
+    def test_domain_violation_rejected(self, converter):
+        attr = Attribute(
+            entity="Acme Corp", entity_type="Company",
+            attribute="employeeId", value="E-0000",
+        )
+        assert converter.convert_attribute(attr) is None
+
+    def test_no_domain_allows_anything(self, converter):
+        attr = Attribute(
+            entity="Widget", entity_type="Product",
+            attribute="description", value="A useful widget",
+        )
+        assert converter.convert_attribute(attr) is not None
+
+
+# ---------------------------------------------------------------------------
+# OntologySelector bypass for small ontologies (#908)
+# ---------------------------------------------------------------------------
+
+def _make_ontology(n_classes, n_obj_props=0, n_dt_props=0):
+    classes = {
+        f"C{i}": OntologyClass(uri=f"http://example.org/C{i}")
+        for i in range(n_classes)
+    }
+    obj_props = {
+        f"op{i}": OntologyProperty(
+            uri=f"http://example.org/op{i}", type="owl:ObjectProperty"
+        )
+        for i in range(n_obj_props)
+    }
+    dt_props = {
+        f"dp{i}": OntologyProperty(
+            uri=f"http://example.org/dp{i}", type="owl:DatatypeProperty"
+        )
+        for i in range(n_dt_props)
+    }
+    return Ontology(
+        id="tiny",
+        metadata={"name": "Tiny"},
+        classes=classes,
+        object_properties=obj_props,
+        datatype_properties=dt_props,
+    )
+
+
+def _make_loader(ontology):
+    loader = Mock()
+    loader.get_ontology.return_value = ontology
+    loader.get_all_ontologies.return_value = {"tiny": ontology}
+    return loader
+
+
+class TestBypassSelectorBelow:
+
+    async def test_bypass_returns_full_ontology(self):
+        """With 3 elements and bypass_selector_below=5, selector is bypassed."""
+        ont = _make_ontology(2, 1, 0)
+        loader = _make_loader(ont)
+        embedder = Mock()
+
+        selector = OntologySelector(
+            ontology_embedder=embedder,
+            ontology_loader=loader,
+            bypass_selector_below=5,
+        )
+
+        segments = [TextSegment(text="some text", type="sentence", position=0)]
+        subsets = await selector.select_ontology_subset(segments)
+
+        assert len(subsets) == 1
+        assert subsets[0].ontology_id == "tiny"
+        assert len(subsets[0].classes) == 2
+        assert len(subsets[0].object_properties) == 1
+        assert subsets[0].relevance_score == 1.0
+        # Embedder should never be called
+        embedder.embed_text.assert_not_called()
+
+    async def test_no_bypass_when_above_threshold(self):
+        """With 10 elements and bypass_selector_below=5, selector runs normally."""
+        ont = _make_ontology(6, 3, 1)
+        loader = _make_loader(ont)
+
+        embedder = Mock()
+        embedder.embed_text = AsyncMock(return_value=[0.1, 0.2])
+        vector_store = Mock()
+        vector_store.size.return_value = 10
+        vector_store.search.return_value = []
+        embedder.get_vector_store.return_value = vector_store
+
+        selector = OntologySelector(
+            ontology_embedder=embedder,
+            ontology_loader=loader,
+            bypass_selector_below=5,
+        )
+
+        segments = [TextSegment(text="some text", type="sentence", position=0)]
+        subsets = await selector.select_ontology_subset(segments)
+
+        # Vector store was consulted (selector ran normally)
+        vector_store.size.assert_called_once()
+
+    async def test_bypass_at_exact_threshold_not_triggered(self):
+        """With exactly 5 elements and bypass_selector_below=5, selector runs (< not <=)."""
+        ont = _make_ontology(3, 1, 1)  # total = 5
+        loader = _make_loader(ont)
+
+        embedder = Mock()
+        embedder.embed_text = AsyncMock(return_value=[0.1, 0.2])
+        vector_store = Mock()
+        vector_store.size.return_value = 5
+        vector_store.search.return_value = []
+        embedder.get_vector_store.return_value = vector_store
+
+        selector = OntologySelector(
+            ontology_embedder=embedder,
+            ontology_loader=loader,
+            bypass_selector_below=5,
+        )
+
+        segments = [TextSegment(text="some text", type="sentence", position=0)]
+        subsets = await selector.select_ontology_subset(segments)
+
+        # Should NOT bypass — 5 is not < 5
+        vector_store.size.assert_called_once()
+
+    async def test_bypass_zero_disables(self):
+        """bypass_selector_below=0 means bypass never triggers."""
+        ont = _make_ontology(0, 0, 0)  # empty ontology
+        loader = _make_loader(ont)
+
+        embedder = Mock()
+        embedder.embed_text = AsyncMock(return_value=[0.1])
+        vector_store = Mock()
+        vector_store.size.return_value = 0
+        vector_store.search.return_value = []
+        embedder.get_vector_store.return_value = vector_store
+
+        selector = OntologySelector(
+            ontology_embedder=embedder,
+            ontology_loader=loader,
+            bypass_selector_below=0,
+        )
+
+        segments = [TextSegment(text="some text", type="sentence", position=0)]
+        subsets = await selector.select_ontology_subset(segments)
+
+        # 0 is not < 0, so bypass doesn't trigger
+        vector_store.size.assert_called_once()
diff --git a/trustgraph-flow/trustgraph/extract/kg/ontology/extract.py b/trustgraph-flow/trustgraph/extract/kg/ontology/extract.py
index 1d45d3f9..6a43e547 100644
--- a/trustgraph-flow/trustgraph/extract/kg/ontology/extract.py
+++ b/trustgraph-flow/trustgraph/extract/kg/ontology/extract.py
@@ -121,6 +121,7 @@ class Processor(FlowProcessor):
         # Configuration
         self.top_k = params.get("top_k", 10)
         self.similarity_threshold = params.get("similarity_threshold", 0.3)
+        self.bypass_selector_below = params.get("bypass_selector_below", 5)
 
         # Per-workspace ontology version tracking
         self.current_ontology_versions = {}  # workspace -> version
@@ -187,7 +188,8 @@ class Processor(FlowProcessor):
                 ontology_embedder=ontology_embedder,
                 ontology_loader=loader,
                 top_k=self.top_k,
-                similarity_threshold=self.similarity_threshold
+                similarity_threshold=self.similarity_threshold,
+                bypass_selector_below=self.bypass_selector_below,
             )
 
             # Store flow-specific components
@@ -981,6 +983,13 @@ class Processor(FlowProcessor):
             default=0.3,
             help='Similarity threshold for ontology matching (default: 0.3, range: 0.0-1.0)'
         )
+        parser.add_argument(
+            '--bypass-selector-below',
+            type=int,
+            default=5,
+            help='Bypass ontology selector when total ontology elements '
+                 '(classes + properties) is below this value (default: 5)'
+        )
         parser.add_argument(
             '--triples-batch-size',
             type=int,
diff --git a/trustgraph-flow/trustgraph/extract/kg/ontology/ontology_selector.py b/trustgraph-flow/trustgraph/extract/kg/ontology/ontology_selector.py
index 5111529a..5fd60a0f 100644
--- a/trustgraph-flow/trustgraph/extract/kg/ontology/ontology_selector.py
+++ b/trustgraph-flow/trustgraph/extract/kg/ontology/ontology_selector.py
@@ -33,19 +33,44 @@ class OntologySelector:
     def __init__(self, ontology_embedder: OntologyEmbedder,
                  ontology_loader: OntologyLoader,
                  top_k: int = 10,
-                 similarity_threshold: float = 0.7):
-        """Initialize the ontology selector.
-
-        Args:
-            ontology_embedder: Embedder with vector store
-            ontology_loader: Loader with ontology definitions
-            top_k: Number of top results to retrieve per segment
-            similarity_threshold: Minimum similarity score
-        """
+                 similarity_threshold: float = 0.3,
+                 bypass_selector_below: int = 5):
         self.embedder = ontology_embedder
         self.loader = ontology_loader
         self.top_k = top_k
         self.similarity_threshold = similarity_threshold
+        self.bypass_selector_below = bypass_selector_below
+
+    def _total_ontology_elements(self) -> int:
+        total = 0
+        for ontology in self.loader.get_all_ontologies().values():
+            total += len(ontology.classes)
+            total += len(ontology.object_properties)
+            total += len(ontology.datatype_properties)
+        return total
+
+    def _build_full_subsets(self) -> List[OntologySubset]:
+        subsets = []
+        for ont_id, ontology in self.loader.get_all_ontologies().items():
+            subset = OntologySubset(
+                ontology_id=ont_id,
+                classes={
+                    cid: cls.__dict__
+                    for cid, cls in ontology.classes.items()
+                },
+                object_properties={
+                    pid: prop.__dict__
+                    for pid, prop in ontology.object_properties.items()
+                },
+                datatype_properties={
+                    pid: prop.__dict__
+                    for pid, prop in ontology.datatype_properties.items()
+                },
+                metadata=ontology.metadata,
+                relevance_score=1.0,
+            )
+            subsets.append(subset)
+        return subsets
 
     async def select_ontology_subset(self, segments: List[TextSegment]) -> List[OntologySubset]:
         """Select relevant ontology subsets for text segments.
@@ -56,6 +81,15 @@ class OntologySelector:
         Returns:
             List of ontology subsets with relevant elements
         """
+        total = self._total_ontology_elements()
+        if total < self.bypass_selector_below:
+            logger.info(
+                f"Ontology has {total} elements (below "
+                f"bypass_selector_below={self.bypass_selector_below}), "
+                f"using full ontology"
+            )
+            return self._build_full_subsets()
+
         # Collect all relevant elements
         relevant_elements = await self._find_relevant_elements(segments)
 
diff --git a/trustgraph-flow/trustgraph/extract/kg/ontology/triple_converter.py b/trustgraph-flow/trustgraph/extract/kg/ontology/triple_converter.py
index 06fff4f4..d9e6c837 100644
--- a/trustgraph-flow/trustgraph/extract/kg/ontology/triple_converter.py
+++ b/trustgraph-flow/trustgraph/extract/kg/ontology/triple_converter.py
@@ -6,7 +6,7 @@ with full URIs and correct is_uri flags.
 """
 
 import logging
-from typing import List, Optional
+from typing import List, Optional, Set
 
 from .... schema import Triple, Term, IRI, LITERAL
 from .... rdf import RDF_TYPE, RDF_LABEL
@@ -32,6 +32,25 @@ class TripleConverter:
         self.ontology_id = ontology_id
         self.entity_registry = EntityRegistry(ontology_id)
 
+    def _get_ancestor_classes(self, class_id: str) -> Set[str]:
+        ancestors = set()
+        current = class_id
+        while current:
+            cls_def = self.ontology_subset.classes.get(current)
+            if not cls_def:
+                break
+            parent = cls_def.get("subclass_of") if isinstance(cls_def, dict) else getattr(cls_def, "subclass_of", None)
+            if not parent or parent in ancestors:
+                break
+            ancestors.add(parent)
+            current = parent
+        return ancestors
+
+    def _matches_class_constraint(self, actual_type: str, expected_type: str) -> bool:
+        if actual_type == expected_type:
+            return True
+        return expected_type in self._get_ancestor_classes(actual_type)
+
     def convert_all(self, extraction: ExtractionResult) -> List[Triple]:
         """Convert complete extraction result to RDF triples.
 
@@ -129,6 +148,29 @@ class TripleConverter:
             logger.warning(f"Unknown relationship '{relationship.relation}', skipping")
             return None
 
+        # Enforce domain/range constraints when declared
+        prop_def = self.ontology_subset.object_properties.get(
+            relationship.relation, {}
+        )
+        domain = prop_def.get("domain") if isinstance(prop_def, dict) else getattr(prop_def, "domain", None)
+        range_ = prop_def.get("range") if isinstance(prop_def, dict) else getattr(prop_def, "range", None)
+
+        if domain and not self._matches_class_constraint(relationship.subject_type, domain):
+            logger.warning(
+                f"Domain violation: '{relationship.relation}' expects "
+                f"domain '{domain}', got subject type "
+                f"'{relationship.subject_type}', skipping"
+            )
+            return None
+
+        if range_ and not self._matches_class_constraint(relationship.object_type, range_):
+            logger.warning(
+                f"Range violation: '{relationship.relation}' expects "
+                f"range '{range_}', got object type "
+                f"'{relationship.object_type}', skipping"
+            )
+            return None
+
         # Generate triple: subject property object
         return Triple(
             s=Term(type=IRI, iri=subject_uri),
@@ -157,11 +199,25 @@ class TripleConverter:
             logger.warning(f"Unknown attribute '{attribute.attribute}', skipping")
             return None
 
+        # Enforce domain constraint when declared
+        prop_def = self.ontology_subset.datatype_properties.get(
+            attribute.attribute, {}
+        )
+        domain = prop_def.get("domain") if isinstance(prop_def, dict) else getattr(prop_def, "domain", None)
+
+        if domain and not self._matches_class_constraint(attribute.entity_type, domain):
+            logger.warning(
+                f"Domain violation: attribute '{attribute.attribute}' "
+                f"expects domain '{domain}', got entity type "
+                f"'{attribute.entity_type}', skipping"
+            )
+            return None
+
         # Generate triple: entity property "literal value"
         return Triple(
             s=Term(type=IRI, iri=entity_uri),
             p=Term(type=IRI, iri=property_uri),
-            o=Term(type=LITERAL, value=attribute.value)  # Literal!
+            o=Term(type=LITERAL, value=attribute.value)
         )
 
     def _get_class_uri(self, class_id: str) -> Optional[str]: