[Bug] HttpxRequestAdapter: The silent deprecation of base_url is actually a breaking change #501

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1. github-project-automation

   added this to Kiotaon Nov 17, 2025
2. github-project-automation

   moved this to Needs Triage 🔍 in Kiotaon Nov 17, 2025
3. HardMax71 commented on Oct 3, 2026

   

   Max Azatian (HardMax71)

   on Oct 3, 2026

   Contributor

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   Reproduced on kiota-http 1.14.1 and on main (ce04532). It started in 1.9.4 with #481, which drops the argument on purpose and adds a test asserting it's ignored (test_httpx_request_adapter.py#L629-L631). 1.9.3 still honors it.

   The error is only half of it. With a plain adapter the empty base URL turns into a relative request URL, so httpx fails with "Request URL is missing an 'http://' or 'https://' protocol." With the Azure auth provider it fails earlier with "Valid url scheme and host required", presumably the misleading error you saw (#470 had the same message).

   With a generated client there's no error at all. Every kiota-generated Python client fills an empty adapter base_url with its default server (msgraph's sets https://graph.microsoft.com/v1.0). So the URL passed to the constructor gets replaced and requests quietly go to a different host.

   The repro runs two local servers. "custom" is what gets passed as base_url, "default" stands in for a generated client's default server. Install with pip install microsoft-kiota-http==1.14.1 microsoft-kiota-authentication-azure==1.14.1.

   import asyncio
   import threading
   import time
   from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
   
   from azure.core.credentials import AccessToken
   from kiota_abstractions.authentication import AnonymousAuthenticationProvider
   from kiota_abstractions.method import Method
   from kiota_abstractions.request_information import RequestInformation
   from kiota_authentication_azure.azure_identity_authentication_provider import AzureIdentityAuthenticationProvider
   from kiota_http.httpx_request_adapter import HttpxRequestAdapter
   
   hits = []
   
   
   def serve(name):
       class Handler(BaseHTTPRequestHandler):
           def do_GET(self):
               hits.append(name + self.path)
               self.send_response(204)
               self.end_headers()
   
           def log_message(self, *args):
               pass
   
       server = ThreadingHTTPServer(("127.0.0.1", 0), Handler)
       threading.Thread(target=server.serve_forever, daemon=True).start()
       return f"http://127.0.0.1:{server.server_address[1]}"
   
   
   class FakeCredential:
       def get_token(self, *scopes, **kwargs):
           return AccessToken("fake", int(time.time()) + 3600)
   
   
   CUSTOM, DEFAULT = serve("custom"), serve("default")
   
   
   async def send(adapter):
       hits.clear()
       try:
           await adapter.send_no_response_content_async(RequestInformation(Method.GET, "{+baseurl}/ping", {}), None)
           return f"reached {hits}"
       except Exception as exc:
           return f"{type(exc).__name__}: {exc}"
   
   
   async def main():
       for auth in (AnonymousAuthenticationProvider(), AzureIdentityAuthenticationProvider(FakeCredential())):
           adapter = HttpxRequestAdapter(auth, base_url=CUSTOM)
           print(f"{type(auth).__name__}, adapter.base_url={adapter.base_url!r}")
           print(f"  plain adapter:    {await send(adapter)}")
           adapter = HttpxRequestAdapter(auth, base_url=CUSTOM)
           if not adapter.base_url:  # what every generated client constructor does
               adapter.base_url = DEFAULT
           print(f"  generated client: {await send(adapter)}")
           adapter = HttpxRequestAdapter(auth)
           adapter.base_url = CUSTOM
           print(f"  setter:           {await send(adapter)}")
   
   
   asyncio.run(main())

   Output on 1.14.1, and main gives the same:

   AnonymousAuthenticationProvider, adapter.base_url=''
     plain adapter:    UnsupportedProtocol: Request URL is missing an 'http://' or 'https://' protocol.
     generated client: reached ['default/ping']
     setter:           reached ['custom/ping']
   AzureIdentityAuthenticationProvider, adapter.base_url=''
     plain adapter:    HTTPError: Valid url scheme and host required
     generated client: reached ['default/ping']
     setter:           reached ['custom/ping']
   

   On 1.9.3 adapter.base_url is the custom URL and all six requests reach custom.

   #490 asks to remove the parameter, and the reply there asks whether it should be used instead. I'd go back to the pre-1.9.4 rule: an explicit base_url wins, otherwise take the client's. msgraph-core's BaseGraphRequestAdapter doesn't pass base_url, so that shouldn't bring back microsoftgraph/msgraph-beta-sdk-python#743, the bug #481 was fixing. I haven't run the beta SDK against it though. If removal is the plan, a DeprecationWarning when the argument is passed would at least end the silent part. Either way one PR can close this and #490, and I can send it once there's a call on the direction.
4. Vincent Biret (baywet)

   closed this as completedin #761on Oct 5, 2026