feat: support session_id in current chat search

tests/test_gateway.py

@@ -1181,6 +1181,63 @@ async def test_search_rejects_invalid_upstream_options(
     assert backend.search_calls == []
 
 
+@pytest.mark.asyncio
+async def test_search_current_chat_accepts_session_id(
+    config: GatewayConfig,
+) -> None:
+    backend = FakeBackendClient()
+    async with app_client(config, backend) as client:
+        user_key = await create_user(client)
+        response = await client.post(
+            "/memories/search",
+            json={
+                "user_id": "u_123",
+                "user_key": user_key,
+                "session_id": "chat:c_1",
+                "query": "hello",
+                "scope": ["current_chat"],
+            },
+        )
+
+    assert response.status_code == 200, response.text
+    assert backend.search_calls == [
+        {
+            "user_id": "u_123",
+            "query": "hello",
+            "method": "hybrid",
+            "top_k": 8,
+            "include_profile": True,
+            "enable_llm_rerank": True,
+            "app_id": "default",
+            "project_id": "default",
+            "filters": {"session_id": "chat:c_1"},
+        }
+    ]
+
+
+@pytest.mark.asyncio
+async def test_search_rejects_conflicting_session_and_conversation_ids(
+    config: GatewayConfig,
+) -> None:
+    backend = FakeBackendClient()
+    async with app_client(config, backend) as client:
+        user_key = await create_user(client)
+        response = await client.post(
+            "/memories/search",
+            json={
+                "user_id": "u_123",
+                "user_key": user_key,
+                "session_id": "chat:c_1",
+                "conversation_id": "c_2",
+                "query": "hello",
+                "scope": ["current_chat"],
+            },
+        )
+
+    assert response.status_code == 422, response.text
+    assert backend.search_calls == []
+
+
 @pytest.mark.asyncio
 async def test_search_combines_custom_and_scope_filters(
     config: GatewayConfig,