diff --git a/samsung_appliance/registry/__init__.py b/samsung_appliance/registry/__init__.py
index e69de29..f1045d1 100644
--- a/samsung_appliance/registry/__init__.py
+++ b/samsung_appliance/registry/__init__.py
@@ -0,0 +1,6 @@
+from .adapter import RuntimeDescriptor, build_runtime_descriptor
+from .discovery import BoundEntity, discover
+from .registry import CAPABILITIES
+
+__all__ = ['CAPABILITIES', 'discover', 'BoundEntity',
+           'RuntimeDescriptor', 'build_runtime_descriptor']
diff --git a/samsung_appliance/registry/registry.py b/samsung_appliance/registry/registry.py
index af5a5b1..5310c54 100644
--- a/samsung_appliance/registry/registry.py
+++ b/samsung_appliance/registry/registry.py
@@ -3,11 +3,20 @@
 Built from the full list of Capability objects in the capabilities package.
 Consumed by discover() at connection time to bind device resources to entities.
 
-Note: each href must appear in at most one Capability across all modules.
-If two capabilities share an href, the later one in the scan order wins —
-this is a bug, not a feature. Add all entities for a given href to the same
-Capability object instead.
+Raises ValueError at import if any href appears in multiple capabilities.
 """
 from .capabilities import ALL
+from .capability import Capability
 
-CAPABILITIES: dict = {cap.href: cap for cap in ALL}
+
+def _build() -> dict[str, Capability]:
+    """Build the registry, raising ValueError if any href is duplicated."""
+    out: dict[str, Capability] = {}
+    for cap in ALL:
+        if cap.href in out:
+            raise ValueError(f"duplicate capability href: {cap.href}")
+        out[cap.href] = cap
+    return out
+
+
+CAPABILITIES: dict[str, Capability] = _build()
diff --git a/tests/test_registry.py b/tests/test_registry.py
new file mode 100644
index 0000000..5b88cb1
--- /dev/null
+++ b/tests/test_registry.py
@@ -0,0 +1,18 @@
+"""Tests for the CAPABILITIES registry."""
+from samsung_appliance.registry.registry import CAPABILITIES
+
+
+def test_registry_is_keyed_by_href():
+    """Registry keys should match capability hrefs."""
+    for href, cap in CAPABILITIES.items():
+        assert cap.href == href
+
+
+def test_registry_has_no_duplicate_href():
+    """Building succeeded => no duplicates raised at import."""
+    assert len(CAPABILITIES) >= 7
+
+
+def test_operational_state_present():
+    """At least one capability should have 'state' in its href."""
+    assert any('state' in href for href in CAPABILITIES)