Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #1177

Kludex · 2025-07-21T08:43:12Z

The current name is not very intuitive considering the class name and the module.

ihrpr

The deprecated wrapper is missing the httpx_client_factory and auth parameters. This could break existing code using those parameters.

(it's probably a good time to replace httpx_client_factory with an object)

Kludex · 2025-07-21T10:08:12Z

I blame copilot. 😄

Kludex · 2025-07-21T10:18:53Z

(it's probably a good time to replace httpx_client_factory with an object)

I think the timeouts, the auth and the httpx_client_factory CAN be replaced. The timeouts I think can be subjective, but the auth and the httpx_client_factory I think need to be replaced.

ihrpr · 2025-07-21T12:18:46Z

(it's probably a good time to replace httpx_client_factory with an object)

I think the timeouts, the auth and the httpx_client_factory CAN be replaced. The timeouts I think can be subjective, but the auth and the httpx_client_factory I think need to be replaced.

should we just replace it now, since we are deprecating one method, would be good to have a nice alternative and not to deprecate it twice?

Kludex · 2025-07-21T12:25:11Z

(it's probably a good time to replace httpx_client_factory with an object)

I think the timeouts, the auth and the httpx_client_factory CAN be replaced. The timeouts I think can be subjective, but the auth and the httpx_client_factory I think need to be replaced.

should we just replace it now, since we are deprecating one method, would be good to have a nice alternative and not to deprecate it twice?

I didn't get what you said. I agree that it's a good moment to change the parameters of the new streamable_http_client.

dsp-ant · 2025-09-02T12:40:10Z

Should we do this and deprecate the old module?

felixweinberger · 2025-09-22T21:04:18Z

FYI for viewers: on my todo list to update this

Modernize streamable_http_client API by accepting httpx.AsyncClient instances directly instead of factory functions, following industry standards. - New API: httpx_client: httpx.AsyncClient | None parameter - Default client created with recommended timeouts if None - Deprecated wrapper provides backward compatibility - Updated examples to show custom client usage - Add MCP_DEFAULT_TIMEOUT constants to _httpx_utils

outdated - pushed updated version making httpx_client a param instead of factory

This commit fixes all test failures introduced by the API change from httpx_client_factory to direct httpx_client parameter: 1. Updated deprecated imports: Changed streamablehttp_client to streamable_http_client in test files 2. Fixed 307 redirect errors: Replaced httpx.AsyncClient with create_mcp_http_client which includes follow_redirects=True by default 3. Fixed test assertion: Updated test_session_group.py to mock create_mcp_http_client and verify the new API signature where streamable_http_client receives httpx_client parameter instead of individual headers/timeout parameters 4. Removed unused httpx import from main.py after inlining client creation All tests now pass with the new API.

felixweinberger · 2025-10-01T18:37:13Z

src/mcp/client/streamable_http.py

        self.session_id = None
        self.protocol_version = None
        self.request_headers = {
+            **self.headers,


⚠️ Important change 1/2 ⚠️

Previously we would have streamablehttp_client create the httpx.AsyncClient via a factory after initializing the transport. That means we could use these transport.request_headers when creating the httpx.AsyncClient to ensure the client and the transport have the same headers.

If we now accept httpx_client as an argument to streamable_http_client, that client might have custom headers! In fact by default httpx.AsyncClient creates headers here that need to be overriden (hence moving the ACCEPT and CONTENT_TYPE after)

Therefore the transport needs to override these headers now if they're present to be configured correctly.

Added missing type annotation imports that were causing NameError and preventing test collection: - RequestResponder from mcp.shared.session - SessionMessage from mcp.shared.message - GetSessionIdCallback from mcp.client.streamable_http - RequestContext from mcp.shared.context This fixes 4 NameError collection failures and 10 F821 ruff errors, allowing all 20 tests in the file to be properly collected and executed.

Restore type annotations on test function parameters in test_streamable_http.py that were accidentally removed during the function renaming from streamablehttp_client to streamable_http_client. Added type annotations to: - Fixture parameters: basic_server, basic_server_url, json_response_server, json_server_url, event_server, monkeypatch - Test function parameters: initialized_client_session This fixes all 61 pyright errors and ensures type safety matches the main branch standards.

Remove complex mocking of create_mcp_http_client in the streamablehttp test case. Instead, let the real create_mcp_http_client execute and only verify that streamable_http_client receives the correct parameters including a real httpx.AsyncClient instance. This simplifies the test by: - Removing 13 lines of mock setup code - Removing 14 lines of mock verification code - Removing 3 lines of mock cleanup code - Trusting that create_mcp_http_client works (it has its own tests) The test now focuses on verifying the integration between session_group and streamable_http_client rather than re-testing create_mcp_http_client.

felixweinberger · 2025-10-01T19:04:42Z

src/mcp/client/streamable_http.py

+    # Sync client headers with transport's merged headers (includes MCP protocol requirements)
+    client.headers.update(transport.request_headers)


⚠️ Important change 2/2 ⚠️

We need to sync the headers on the client back so that they match with the transport after the transport has overriden them. If the user passes in a httpx_client they created, that could have arbitrary headers that no longer match the headers on the transport.

Overall I find this quite horrible - but I'm not sure how else to make this work via an object instead of a factory. Open for suggestions...

felixweinberger · 2025-10-01T19:05:47Z

@Kludex @ihrpr @dsp-ant gave this a shot, trying to replace the factory with a client object.

Results in some ugly header mangling that I don't see how to avoid given the existing structure. Keen for thoughts.

felixweinberger · 2025-10-01T19:15:43Z

src/mcp/shared/_httpx_utils.py

    # Handle timeout
    if timeout is None:
-        kwargs["timeout"] = httpx.Timeout(30.0)
+        kwargs["timeout"] = httpx.Timeout(MCP_DEFAULT_TIMEOUT, read=MCP_DEFAULT_SSE_READ_TIMEOUT)


Previously we'd rely on the transport setting this to 60 * 5 when creating our client, but we can't rely on that anymore as the client may now be created before the transport.

Kludex · 2025-10-02T10:32:23Z

examples/snippets/clients/oauth_client.py

 from mcp.client.auth import OAuthClientProvider, TokenStorage
-from mcp.client.streamable_http import streamablehttp_client
+from mcp.client.streamable_http import streamable_http_client
+from mcp.shared._httpx_utils import create_mcp_http_client


I don't think we should have private methods being exposed in examples. 🤔

Kludex · 2025-10-02T12:42:46Z

src/mcp/client/streamable_http.py

-    timeout: float | timedelta = 30,
-    sse_read_timeout: float | timedelta = 60 * 5,
+    *,
+    httpx_client: httpx.AsyncClient | None = None,


Suggested change

httpx_client: httpx.AsyncClient | None = None,

http_client: httpx.AsyncClient | None = None,

Kludex requested review from a team, ochafik and ihrpr July 21, 2025 08:43

ihrpr previously requested changes Jul 21, 2025

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felixweinberger self-assigned this Sep 22, 2025

felixweinberger added the needs maintainer action Potentially serious issue - needs proactive fix and maintainer attention label Sep 22, 2025

felixweinberger mentioned this pull request Sep 23, 2025

Replace httpx_client_factory with direct httpx_client parameter for better flexibility #1280

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felixweinberger added the needs more work Not ready to be merged yet, needs additional changes. label Sep 23, 2025

felixweinberger removed the needs more work Not ready to be merged yet, needs additional changes. label Oct 1, 2025

Kludex and others added 4 commits October 1, 2025 16:04

Rename streamablehttp_client to streamable_http_client

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Apply pre-commit

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Add missing paramters

f5c7a5e

felixweinberger force-pushed the rename-streamable-http branch from 222b13f to 74fa629 Compare October 1, 2025 18:18

felixweinberger requested review from ihrpr and removed request for ochafik and ihrpr October 1, 2025 18:24

felixweinberger reviewed Oct 1, 2025

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felixweinberger added 3 commits October 1, 2025 19:45

felixweinberger reviewed Oct 1, 2025

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felixweinberger requested a review from ihrpr October 1, 2025 19:05

felixweinberger added needs more eyes Needs alignment among maintainers whether this is something we want to add and removed needs maintainer action Potentially serious issue - needs proactive fix and maintainer attention labels Oct 1, 2025

felixweinberger changed the title ~~Rename streamablehttp_client to streamable_http_client~~ Add streamable_http_client which accepts httpx.AsyncClient instead of httpx_client_factory Oct 1, 2025

felixweinberger force-pushed the rename-streamable-http branch from 7a6c89d to 43dec02 Compare October 1, 2025 19:14

felixweinberger reviewed Oct 1, 2025

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ruhz3 mentioned this pull request Oct 1, 2025

httpx.ConnectError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain (_ssl.c:1002) #1370

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Kludex commented Oct 2, 2025

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felixweinberger linked an issue Oct 7, 2025 that may be closed by this pull request

httpx.ConnectError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain (_ssl.c:1002) #1370

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This was referenced Oct 7, 2025

Add SSL Certificate Verification Options to FastMCP Client #870

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Need to add verify=False to steamablehttp_client #826

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Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #1177

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		# Sync client headers with transport's merged headers (includes MCP protocol requirements)
		client.headers.update(transport.request_headers)

	httpx_client: httpx.AsyncClient \| None = None,
	http_client: httpx.AsyncClient \| None = None,

Add streamable_http_client which accepts httpx.AsyncClient instead of httpx_client_factory #1177

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Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #1177

Add `streamable_http_client` which accepts `httpx.AsyncClient` instead of `httpx_client_factory` #1177

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