Support media in session chat API

gateway/platforms/api_server.py

@@ -319,6 +319,20 @@ def _multimodal_validation_error(exc: ValueError, *, param: str) -> "web.Respons
     )
 
 
+def _session_chat_user_message(body: Dict[str, Any], *, param: str = "message") -> tuple[Any, Optional["web.Response"]]:
+    """Parse and normalize session chat ``message`` / ``input`` like chat completions."""
+    user_message = body.get("message") or body.get("input")
+    if not _content_has_visible_payload(user_message):
+        return None, web.json_response(
+            _openai_error("Missing 'message' field", code="missing_message"),
+            status=400,
+        )
+    try:
+        return _normalize_multimodal_content(user_message), None
+    except ValueError as exc:
+        return None, _multimodal_validation_error(exc, param=param)
+
+
 def check_api_server_requirements() -> bool:
     """Check if API server dependencies are available."""
     return AIOHTTP_AVAILABLE
@@ -1483,9 +1497,9 @@ class APIServerAdapter(BasePlatformAdapter):
         body, err = await self._read_json_body(request)
         if err:
             return err
-        user_message = body.get("message") or body.get("input")
-        if not _content_has_visible_payload(user_message):
-            return web.json_response(_openai_error("Missing 'message' field", code="missing_message"), status=400)
+        user_message, err = _session_chat_user_message(body)
+        if err is not None:
+            return err
         system_prompt = body.get("system_message") or body.get("instructions")
         if system_prompt is not None and not isinstance(system_prompt, str):
             return web.json_response(_openai_error("system_message must be a string", code="invalid_system_message"), status=400)
@@ -1527,9 +1541,9 @@ class APIServerAdapter(BasePlatformAdapter):
         body, err = await self._read_json_body(request)
         if err:
             return err
-        user_message = body.get("message") or body.get("input")
-        if not _content_has_visible_payload(user_message):
-            return web.json_response(_openai_error("Missing 'message' field", code="missing_message"), status=400)
+        user_message, err = _session_chat_user_message(body)
+        if err is not None:
+            return err
         system_prompt = body.get("system_message") or body.get("instructions")
         if system_prompt is not None and not isinstance(system_prompt, str):
             return web.json_response(_openai_error("system_message must be a string", code="invalid_system_message"), status=400)

tests/gateway/test_session_api.py

@@ -180,6 +180,66 @@ async def test_session_chat_loads_history_and_preserves_session_headers(auth_ada
     ]
 
 
+@pytest.mark.asyncio
+async def test_session_chat_accepts_multimodal_message(auth_adapter, session_db):
+    session_id = session_db.create_session("image-session", "api_server")
+    image_payload = [
+        {"type": "input_text", "text": "What's in this image?"},
+        {"type": "input_image", "image_url": "data:image/png;base64,AAAA"},
+    ]
+    expected_user_message = [
+        {"type": "text", "text": "What's in this image?"},
+        {"type": "image_url", "image_url": {"url": "data:image/png;base64,AAAA"}},
+    ]
+
+    mock_run = AsyncMock(return_value=({"final_response": "A cat.", "session_id": session_id}, {"total_tokens": 4}))
+    app = _create_session_app(auth_adapter)
+    with patch.object(auth_adapter, "_run_agent", mock_run):
+        async with TestClient(TestServer(app)) as cli:
+            resp = await cli.post(
+                f"/api/sessions/{session_id}/chat",
+                json={"message": image_payload},
+                headers={"Authorization": "Bearer sk-test"},
+            )
+            assert resp.status == 200, await resp.text()
+
+    _, kwargs = mock_run.call_args
+    assert kwargs["user_message"] == expected_user_message
+
+
+@pytest.mark.asyncio
+async def test_session_chat_stream_accepts_multimodal_message(adapter, session_db):
+    session_id = session_db.create_session("image-stream-session", "api_server")
+    image_payload = [
+        {"type": "input_text", "text": "What's in this image?"},
+        {"type": "input_image", "image_url": "data:image/png;base64,AAAA"},
+    ]
+    expected_user_message = [
+        {"type": "text", "text": "What's in this image?"},
+        {"type": "image_url", "image_url": {"url": "data:image/png;base64,AAAA"}},
+    ]
+    captured_kwargs = {}
+
+    async def fake_run(**kwargs):
+        captured_kwargs.update(kwargs)
+        kwargs["stream_delta_callback"]("A cat.")
+        return {"final_response": "A cat.", "session_id": session_id}, {"total_tokens": 4}
+
+    app = _create_session_app(adapter)
+    with patch.object(adapter, "_run_agent", side_effect=fake_run):
+        async with TestClient(TestServer(app)) as cli:
+            resp = await cli.post(
+                f"/api/sessions/{session_id}/chat/stream",
+                json={"message": image_payload},
+            )
+            assert resp.status == 200, await resp.text()
+            assert resp.headers["Content-Type"].startswith("text/event-stream")
+            body = await resp.text()
+
+    assert "event: assistant.completed" in body
+    assert captured_kwargs["user_message"] == expected_user_message
+
+
 @pytest.mark.asyncio
 async def test_session_chat_stream_emits_lifecycle_events_and_keepalive_safe_shape(adapter, session_db):
     session_id = session_db.create_session("stream-session", "api_server")