diff --git a/tests/tools/test_mcp_dynamic_discovery.py b/tests/tools/test_mcp_dynamic_discovery.py
index 948560d8ea..76fcb907a4 100644
--- a/tests/tools/test_mcp_dynamic_discovery.py
+++ b/tests/tools/test_mcp_dynamic_discovery.py
@@ -36,6 +36,34 @@ class TestRegisterServerTools:
             assert validate_toolset("my_srv") is True
             assert "mcp__my_srv__my_tool" in resolve_toolset("my_srv")
 
+    def test_colliding_static_toolset_name_merges_both_tool_sets(self, mock_registry):
+        """An MCP server named after a built-in toolset must not be shadowed.
+
+        Regression: an MCP server registered as `homeassistant` (colliding
+        with the static `homeassistant` toolset) had its tools silently
+        dropped because get_toolset() returned the static definition without
+        consulting the alias registered by _register_server_tools().
+        """
+        from toolsets import TOOLSETS, get_toolset, resolve_toolset
+
+        assert "homeassistant" in TOOLSETS  # collision premise
+        static_tools = set(TOOLSETS["homeassistant"]["tools"])
+
+        server = MCPServerTask("homeassistant")
+        server._tools = [_make_mcp_tool("get_entities", "List HA entities")]
+        server.session = MagicMock()
+
+        with patch("tools.registry.registry", mock_registry):
+            registered = _register_server_tools("homeassistant", server, {})
+            assert "mcp__homeassistant__get_entities" in registered
+
+            ts = get_toolset("homeassistant")
+            # Static built-ins are still present...
+            assert static_tools <= set(ts["tools"])
+            # ...and the MCP server's tools are no longer shadowed.
+            assert "mcp__homeassistant__get_entities" in ts["tools"]
+            assert "mcp__homeassistant__get_entities" in resolve_toolset("homeassistant")
+
 
 class TestRefreshTools:
     """Tests for MCPServerTask._refresh_tools nuke-and-repave cycle."""