fix(proxy): preserve ProxyException.code in rerank and image_generation

Both handlers only special-cased HTTPException in their except block, so a
bare ProxyException (e.g. the ProxyMissingRequiredParamError raised by the
previous commit's guard) fell into the generic else branch. That branch reads
getattr(e, "status_code", 500), but ProxyException carries the status on
.code, not .status_code, so it always defaulted to 500. Re-raise ProxyException
instances unchanged, matching the pattern already used in
common_request_processing.py's _handle_llm_api_exception.

litellm/proxy/image_endpoints/endpoints.py

@@ -207,6 +207,8 @@ async def image_generation(
             user_api_key_dict=user_api_key_dict, original_exception=e, request_data=data
         )
         log_llm_api_exception(e, litellm_call_id)
+        if isinstance(e, ProxyException):
+            raise
         if isinstance(e, HTTPException):
             raise ProxyException(
                 message=getattr(e, "message", str(e)),

litellm/proxy/rerank_endpoints/endpoints.py

@@ -117,6 +117,8 @@ async def rerank(
             user_api_key_dict=user_api_key_dict, original_exception=e, request_data=data
         )
         log_llm_api_exception(e, litellm_call_id)
+        if isinstance(e, ProxyException):
+            raise
         if isinstance(e, HTTPException):
             raise ProxyException(
                 message=getattr(e, "message", str(e)),

tests/test_litellm/proxy/image_endpoints/test_endpoints.py

@@ -16,6 +16,7 @@ from litellm._logging import verbose_proxy_logger
 from litellm.proxy._types import ProxyException, UserAPIKeyAuth
 from litellm.proxy.auth.user_api_key_auth import user_api_key_auth
 from litellm.proxy.image_endpoints import endpoints
+from litellm.proxy.route_llm_request import ProxyMissingRequiredParamError
 
 
 @pytest.mark.asyncio
@@ -119,6 +120,69 @@ async def test_image_generation_prompt_rerouting(monkeypatch):
     assert response.headers.get("x-callback-test") == "value"
 
 
+@pytest.mark.asyncio
+async def test_image_generation__missing_required_param_is_400(monkeypatch):
+    """image_generation()'s except block only special-cased HTTPException, so a
+    ProxyMissingRequiredParamError (a ProxyException with code=400) fell into the
+    `else` branch's `getattr(e, "status_code", 500)` and surfaced as a 500."""
+
+    async def fake_add_litellm_data_to_request(**kwargs):
+        return kwargs["data"]
+
+    async def fake_pre_call_hook(*, user_api_key_dict, data, call_type):  # type: ignore[override]
+        return data
+
+    async def fake_post_call_failure_hook(**_: Any) -> None:
+        return None
+
+    async def fake_route_request(*, data, **kwargs):  # type: ignore[override]
+        raise ProxyMissingRequiredParamError(route="/image/generations", param="prompt")
+
+    fake_proxy_logger = SimpleNamespace(
+        pre_call_hook=fake_pre_call_hook,
+        post_call_failure_hook=fake_post_call_failure_hook,
+    )
+
+    scope = {
+        "type": "http",
+        "method": "POST",
+        "path": "/v1/images/generations",
+        "headers": [],
+    }
+    body = orjson.dumps({"model": "dall-e-3"})
+
+    async def receive():
+        return {"type": "http.request", "body": body, "more_body": False}
+
+    request = Request(scope, receive)
+    response = Response()
+    user_api_key = UserAPIKeyAuth()
+
+    monkeypatch.setattr(
+        "litellm.proxy.proxy_server.add_litellm_data_to_request",
+        fake_add_litellm_data_to_request,
+    )
+    monkeypatch.setattr("litellm.proxy.proxy_server.general_settings", {})
+    monkeypatch.setattr("litellm.proxy.proxy_server.llm_router", None)
+    monkeypatch.setattr("litellm.proxy.proxy_server.proxy_config", {})
+    monkeypatch.setattr("litellm.proxy.proxy_server.proxy_logging_obj", fake_proxy_logger)
+    monkeypatch.setattr("litellm.proxy.proxy_server.user_model", None)
+    monkeypatch.setattr("litellm.proxy.proxy_server.version", "test-version")
+    monkeypatch.setattr(
+        "litellm.proxy.image_endpoints.endpoints.route_request", fake_route_request
+    )
+
+    with pytest.raises(ProxyException) as exc_info:
+        await endpoints.image_generation(
+            request=request,
+            fastapi_response=response,
+            user_api_key_dict=user_api_key,
+        )
+
+    assert exc_info.value.code == "400"
+    assert exc_info.value.param == "prompt"
+
+
 def _image_edit_client(monkeypatch, captured: Dict[str, Any]) -> TestClient:
     class CaptureProcessing:
         def __init__(self, data: Dict[str, Any]) -> None:

tests/test_litellm/proxy/rerank_endpoints/test_endpoints.py

@@ -15,6 +15,7 @@ import litellm.proxy.proxy_server as proxy_server_mod
 from litellm._logging import verbose_proxy_logger
 from litellm.proxy._types import ProxyException, UserAPIKeyAuth
 from litellm.proxy.rerank_endpoints.endpoints import rerank
+from litellm.proxy.route_llm_request import ProxyMissingRequiredParamError
 from litellm.types.utils import RerankResponse
 
 HIDDEN_PARAMS = {
@@ -209,3 +210,37 @@ async def test_a_rejection_raised_before_routing_keeps_its_own_status(monkeypatc
     error = await _rerank_failure(rejection, raised_before_routing=True, monkeypatch=monkeypatch)
 
     assert (error.type, error.param, error.code) == ("bad_request_error", "session_id", "400")
+
+
+@pytest.mark.asyncio
+async def test_rerank__missing_required_param_is_400():
+    """/rerank's except block only special-cased HTTPException, so a
+    ProxyMissingRequiredParamError (a ProxyException with code=400) fell into the
+    `else` branch's `getattr(e, "status_code", 500)` and surfaced as a 500."""
+    fastapi_response = Response()
+    proxy_logging_obj = MagicMock()
+    proxy_logging_obj.pre_call_hook = AsyncMock(side_effect=lambda **kwargs: kwargs["data"])
+    proxy_logging_obj.post_call_failure_hook = AsyncMock()
+
+    async def fake_add_litellm_data_to_request(**kwargs):
+        return kwargs["data"]
+
+    async def fake_route_request(**kwargs):
+        raise ProxyMissingRequiredParamError(route="/rerank", param="query")
+
+    with (
+        patch.object(proxy_server_mod, "add_litellm_data_to_request", fake_add_litellm_data_to_request),  # test-quality-ok: the rerank route reads these proxy_server module globals; no injection seam on the FastAPI handler
+        patch.object(proxy_server_mod, "route_request", fake_route_request),  # test-quality-ok: the rerank route reads these proxy_server module globals; no injection seam on the FastAPI handler
+        patch.object(proxy_server_mod, "proxy_logging_obj", proxy_logging_obj),  # test-quality-ok: the rerank route reads these proxy_server module globals; no injection seam on the FastAPI handler
+        patch.object(proxy_server_mod, "llm_router", MagicMock()),  # test-quality-ok: the rerank route reads these proxy_server module globals; no injection seam on the FastAPI handler
+        patch.object(proxy_server_mod, "version", "1.2.3"),  # test-quality-ok: the rerank route reads these proxy_server module globals; no injection seam on the FastAPI handler
+    ):
+        with pytest.raises(ProxyException) as exc_info:
+            await rerank(
+                request=_build_request(),
+                fastapi_response=fastapi_response,
+                user_api_key_dict=UserAPIKeyAuth(api_key="sk-test"),
+            )
+
+    assert exc_info.value.code == "400"
+    assert exc_info.value.param == "query"