feat: add deterministic message interaction stages

backend/tests/test_startup_actions.py

@@ -77,6 +77,39 @@ class StartupActionValidationTests(unittest.IsolatedAsyncioTestCase):
                 startup=startup_body().startup,
             )
 
+    def test_realtime_rejects_builtin_opening_message(self):
+        with self.assertRaisesRegex(ValueError, "Realtime"):
+            AssistantUpsert(
+                name="Realtime 开场消息",
+                type="prompt",
+                runtimeMode="realtime",
+                startup={
+                    "openingMessage": {
+                        "title": "重要提示",
+                        "message": "请确认已阅读。",
+                        "confirmLabel": "确认",
+                    }
+                },
+            )
+
+    async def test_builtin_opening_message_does_not_reference_a_tool(self):
+        body = AssistantUpsert(
+            name="内置开场消息",
+            type="prompt",
+            startup={
+                "openingMessage": {
+                    "title": "重要提示",
+                    "message": "请确认已阅读。",
+                    "confirmLabel": "确认",
+                }
+            },
+        )
+
+        await _validate_startup_actions(FakeSession(None), body)
+
+        self.assertEqual(body.startup.actions, [])
+        self.assertEqual(body.startup.opening_message.confirm_label, "确认")
+
     async def test_startup_tool_does_not_need_conversation_binding(self):
         tool = SimpleNamespace(
             id="tool_message",