diff --git a/features/resource_registry_service_coverage.feature b/features/resource_registry_service_coverage.feature
index de3e68179..9e53d8dd3 100644
--- a/features/resource_registry_service_coverage.feature
+++ b/features/resource_registry_service_coverage.feature
@@ -57,3 +57,15 @@ Feature: Resource registry service coverage gaps
     And I show the registered type with auto_discovery and equivalence
     Then the shown type should have the correct auto_discovery
     And the shown type should have the correct equivalence
+
+  # ── _db_to_spec built_in field via namespace column ───────────────
+
+  Scenario: _db_to_spec sets built_in True when namespace column is "builtin"
+    Given a resource type DB row with namespace "builtin" and name "git-checkout"
+    When I convert that row to a spec via _db_to_spec
+    Then the resulting spec built_in should be True
+
+  Scenario: _db_to_spec sets built_in False when namespace column is not "builtin"
+    Given a resource type DB row with namespace "local" and name "local/mytype"
+    When I convert that row to a spec via _db_to_spec
+    Then the resulting spec built_in should be False
diff --git a/features/steps/resource_registry_service_coverage_steps.py b/features/steps/resource_registry_service_coverage_steps.py
index 0b53e57cf..da3eb757f 100644
--- a/features/steps/resource_registry_service_coverage_steps.py
+++ b/features/steps/resource_registry_service_coverage_steps.py
@@ -456,3 +456,63 @@ def step_verify_rt_eq(context: Any) -> None:
     assert eq is not None, "equivalence should be preserved"
     assert eq["criteria"] == ["content_hash"]
     assert eq["description"] == "Hash-based equivalence"
+
+
+# ---------------------------------------------------------------------------
+# Scenarios: _db_to_spec derives built_in from namespace column
+# ---------------------------------------------------------------------------
+
+
+@given('a resource type DB row with namespace "{namespace}" and name "{name}"')
+def step_db_row_with_namespace_and_name(context: Any, namespace: str, name: str) -> None:
+    """Create an in-memory DB row with the given namespace and name."""
+    engine, factory = _in_memory_session_factory()
+    context.ns_builtin_engine = engine
+    context.ns_builtin_factory = factory
+
+    session = factory()
+    from datetime import UTC, datetime
+
+    now = datetime.now(tz=UTC).isoformat()
+    row = ResourceTypeModel(
+        name=name,
+        namespace=namespace,
+        description="Test row for namespace-based built_in detection",
+        resource_kind="physical",
+        sandbox_strategy="none",
+        user_addable=False,
+        handler_ref=None,
+        args_schema_json=None,
+        allowed_parent_types_json=None,
+        allowed_child_types_json=None,
+        auto_discover_json=None,
+        capabilities_json=None,
+        equivalence_json=None,
+        source="test",
+        created_at=now,
+        updated_at=now,
+    )
+    session.add(row)
+    session.commit()
+    context.ns_builtin_row = (
+        session.query(ResourceTypeModel).filter_by(name=name).first()
+    )
+
+
+@when("I convert that row to a spec via _db_to_spec")
+def step_convert_ns_row_to_spec(context: Any) -> None:
+    context.ns_builtin_spec = _db_to_spec(context.ns_builtin_row)
+
+
+@then("the resulting spec built_in should be True")
+def step_verify_builtin_true(context: Any) -> None:
+    assert context.ns_builtin_spec.built_in is True, (
+        f"Expected built_in=True but got {context.ns_builtin_spec.built_in!r}"
+    )
+
+
+@then("the resulting spec built_in should be False")
+def step_verify_builtin_false(context: Any) -> None:
+    assert context.ns_builtin_spec.built_in is False, (
+        f"Expected built_in=False but got {context.ns_builtin_spec.built_in!r}"
+    )
diff --git a/src/cleveragents/application/services/_resource_registry_data.py b/src/cleveragents/application/services/_resource_registry_data.py
index e5ca010ec..8f63c2a43 100644
--- a/src/cleveragents/application/services/_resource_registry_data.py
+++ b/src/cleveragents/application/services/_resource_registry_data.py
@@ -401,7 +401,11 @@ def db_to_spec(row: ResourceTypeModel) -> ResourceTypeSpec:
         equivalence = json.loads(str(raw_equiv))
 
     name_str = str(row.name)
-    is_builtin = "/" not in name_str
+    # Derive built_in from the namespace column: built-in types have
+    # namespace="builtin".  Fall back to the name heuristic only when the
+    # column is unavailable (e.g. legacy rows without a namespace column).
+    raw_ns = getattr(row, "namespace", None)
+    is_builtin = str(raw_ns) == "builtin" if raw_ns is not None else "/" not in name_str
 
     raw_desc = getattr(row, "description", None)
     desc_str = str(raw_desc) if raw_desc is not None else ""