fix(passthrough): keep target URL query when client sends no query params

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/proxy/pass_through_endpoints/pass_through_endpoints.py

@@ -986,7 +986,10 @@ async def pass_through_request(
             forward_headers=forward_headers,
         )
 
-        requested_query_params: dict | None = query_params or dict(request.query_params)
+        requested_query_params: dict | None = {
+            **dict(url.params),
+            **(query_params or dict(request.query_params)),
+        } or None
 
         endpoint_type: Final[EndpointType] = HttpPassThroughEndpointHelpers.get_endpoint_type(str(url))
 
@@ -1188,7 +1191,7 @@ async def pass_through_request(
                 query=urlencode(
                     HttpPassThroughEndpointHelpers.get_merged_query_parameters(
                         existing_url=url,
-                        request_query_params=requested_query_params,
+                        request_query_params=requested_query_params or {},
                         default_query_params=default_query_params,
                     )
                 ).encode("ascii")

tests/test_litellm/proxy/pass_through_endpoints/test_pass_through_endpoints.py

@@ -6,7 +6,6 @@ from collections.abc import Callable
 from contextlib import ExitStack, contextmanager
 from io import BytesIO
 from types import SimpleNamespace
-from typing import Optional
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import httpx
@@ -15,33 +14,31 @@ from fastapi import Request, Response, UploadFile
 from starlette.datastructures import FormData, Headers, QueryParams
 from starlette.datastructures import UploadFile as StarletteUploadFile
 
-
+import litellm
+from litellm.integrations.custom_logger import CustomLogger
+from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLoggingObj
+from litellm.proxy._types import ProxyException, UserAPIKeyAuth
 from litellm.proxy.pass_through_endpoints.pass_through_endpoints import (
     DEFAULT_PASS_THROUGH_REQUEST_TIMEOUT_SECONDS,
+    LITELLM_PASS_THROUGH_CUSTOM_BODY_STATE_KEY,
     HttpPassThroughEndpointHelpers,
     InitPassThroughEndpointHelpers,
-    LITELLM_PASS_THROUGH_CUSTOM_BODY_STATE_KEY,
     _registered_pass_through_routes,
     chat_completion_pass_through_endpoint,
     create_pass_through_route,
     initialize_pass_through_endpoints,
     pass_through_request,
-    resolve_pass_through_request_timeout,
     resolve_llm_passthrough_timeout,
+    resolve_pass_through_request_timeout,
     websocket_passthrough_request,
 )
-from litellm.integrations.custom_logger import CustomLogger
-from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLoggingObj
-from litellm.proxy._types import ProxyException, UserAPIKeyAuth
-from litellm.types.passthrough_endpoints.pass_through_endpoints import (
-    LITELLM_PASS_THROUGH_DEPLOYMENT_MODEL_INFO_STATE_KEY,
-    LITELLM_PASS_THROUGH_RAW_BODY_STATE_KEY,
-)
 from litellm.proxy.pass_through_endpoints.success_handler import (
     PassThroughEndpointLogging,
 )
-
-import litellm
+from litellm.types.passthrough_endpoints.pass_through_endpoints import (
+    LITELLM_PASS_THROUGH_DEPLOYMENT_MODEL_INFO_STATE_KEY,
+    LITELLM_PASS_THROUGH_RAW_BODY_STATE_KEY,
+)
 
 MESSAGE_START_SSE_FRAME = b'event: message_start\ndata: {"type": "message_start"}\n\n'
 
@@ -2425,10 +2422,10 @@ async def _run_pass_through_and_capture_wire_url(
     target: str,
     incoming_query: str,
     merge_query_params: bool = False,
-    default_query_params: Optional[dict] = None,
-    custom_llm_provider: Optional[str] = None,
-    managed_files_hook: Optional[_FakeManagedFilesHook] = None,
-    user_api_key_dict: Optional[UserAPIKeyAuth] = None,
+    default_query_params: dict | None = None,
+    custom_llm_provider: str | None = None,
+    managed_files_hook: _FakeManagedFilesHook | None = None,
+    user_api_key_dict: UserAPIKeyAuth | None = None,
 ) -> httpx.URL:
     import litellm
     from litellm.llms.custom_httpx.http_handler import get_async_httpx_client
@@ -2532,12 +2529,30 @@ async def test_pass_through_request_default_query_params_reach_the_wire():
 
 
 @pytest.mark.asyncio
-async def test_pass_through_request_without_merge_replaces_target_query():
+async def test_pass_through_request_without_merge_preserves_target_query():
     wire_url = await _run_pass_through_and_capture_wire_url(
         target="https://www.bing.com/search?setLang=en-US",
         incoming_query="q=litellm",
     )
-    assert dict(wire_url.params) == {"q": "litellm"}
+    assert dict(wire_url.params) == {"setLang": "en-US", "q": "litellm"}
+
+
+@pytest.mark.asyncio
+async def test_pass_through_request_preserves_target_query_without_client_query():
+    wire_url = await _run_pass_through_and_capture_wire_url(
+        target="https://example.com/v1/models/gemini:streamGenerateContent?alt=sse",
+        incoming_query="",
+    )
+    assert dict(wire_url.params) == {"alt": "sse"}
+
+
+@pytest.mark.asyncio
+async def test_pass_through_request_preserves_target_query_with_client_query():
+    wire_url = await _run_pass_through_and_capture_wire_url(
+        target="https://example.com/v1/models/gemini:streamGenerateContent?alt=sse",
+        incoming_query="key=abc",
+    )
+    assert dict(wire_url.params) == {"alt": "sse", "key": "abc"}
 
 
 @pytest.mark.asyncio
@@ -5239,7 +5254,7 @@ async def test_websocket_passthrough_does_not_close_twice_when_success_logging_f
 
 def _passthrough_kwargs_for_reservation(
     user_api_key_dict: UserAPIKeyAuth,
-    parsed_body: Optional[dict] = None,
+    parsed_body: dict | None = None,
     user_defined_route: bool = False,
 ) -> dict:
     mock_request = MagicMock(spec=Request)