fix(mcp-tool): add httpx_client_factory support to SseConnectionParams by ushelp · Pull Request #4842 · google/adk-python

ushelp · 2026-03-15T16:05:00Z

Link to Issue or Description of Change

1. Link to an existing issue

2. Changes
This change aligns SSE transport behavior with Streamable HTTP transport for MCP tools, enabling users to customize the httpx.AsyncClient for SSE-based MCP connections (e.g., proxy, auth, TLS config).

Update SseConnectionParams model to include httpx_client_factory parameter (matching StreamableHTTPConnectionParams pattern)
Pass httpx_client_factory from SseConnectionParams to underlying sse_client() call
Add model_config to SseConnectionParams to allow arbitrary types for the factory function
Update docstrings to document the new httpx_client_factory attribute
Add unit test for new senarios

Testing Plan

Unit Tests:

I have added or updated unit tests for my change.
- tests/unittests/tools/mcp_tool/test_mcp_session_manager.py
All unit tests pass locally.
- All test cases have passed the test.

Manual End-to-End (E2E) Tests:

Set custom httpx_client_factory parameter for SseConnectionParams

from typing import Any

import httpx
from google.adk.agents.llm_agent import Agent
from google.adk.models import LiteLlm
from google.adk.tools.mcp_tool import SseConnectionParams, McpToolset


# Cutom httpx client factory for MCP SSE transport
def custom_httpx_client_factory(
    headers: dict[str, str] | None = None,
    timeout: httpx.Timeout | None = None,
    auth: httpx.Auth | None = None,
) -> httpx.AsyncClient:
    # Print message for debugging
    print(' === Custom httpx_client_factory running! ===')
    kwargs: dict[str, Any] = {
        "follow_redirects": True,
    }
    if timeout is None:
        kwargs["timeout"] = httpx.Timeout(30, read=300)
    else:
        kwargs["timeout"] = timeout
    if headers is not None:
        kwargs["headers"] = headers
    if auth is not None:
        kwargs["auth"] = auth
    return httpx.AsyncClient(**kwargs)

connection_params = SseConnectionParams(
    url='http://127.0.0.1:9000/sse',
    httpx_client_factory=custom_httpx_client_factory, # Custom httpx client factory
)

tool = McpToolset(connection_params=connection_params)

root_agent = Agent(
    model=LiteLlm(model="ollama_chat/qwen3.5:35b-a3b-q4_K_M"),
    name='root_agent',
    description='A helpful assistant for user questions.',
    instruction='Answer user questions to the best of your knowledge',
    tools=[tool],
)

Run the Agent, and display the debug log in console

2026-03-15 23:54:14,304 - INFO - agent_loader.py:130 - Found root_agent in my_agent.agent
INFO:     127.0.0.1:55642 - "POST /run_sse HTTP/1.1" 200 OK
 === Custom httpx_client_factory running! ===
2026-03-15 23:54:14,345 - INFO - _client.py:1740 - HTTP Request: GET http://127.0.0.1:9000/sse "HTTP/1.1 200 OK"
2026-03-15 23:54:14,349 - INFO - _client.py:1740 - HTTP Request: POST http://127.0.0.1:9000/messages/?session_id=b5750c6e214048c28110dff11c412ecb "HTTP/1.1 202 Accepted"

Checklist

I have read the CONTRIBUTING.md document.
I have performed a self-review of my own code.
I have commented my code, particularly in hard-to-understand areas.
I have added tests that prove my fix is effective or that my feature works.
New and existing unit tests pass locally with my changes.
I have manually tested my changes end-to-end.
Any dependent changes have been merged and published in downstream modules.

Additional context

- Update SseConnectionParams model to include httpx_client_factory parameter (matching StreamableHTTPConnectionParams pattern) - Pass httpx_client_factory from SseConnectionParams to underlying sse_client() call - Add model_config to SseConnectionParams to allow arbitrary types for the factory function - Update docstrings to document the new httpx_client_factory attribute This change aligns SSE transport behavior with Streamable HTTP transport for MCP tools, enabling users to customize the httpx.AsyncClient for SSE-based MCP connections (e.g., proxy, auth, TLS config). Closes google#4841

gemini-code-assist · 2026-03-15T16:05:17Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces the capability to customize the httpx.AsyncClient used for Server-Sent Events (SSE) connections within the MCP tool. By adding an httpx_client_factory parameter to SseConnectionParams, users can now configure advanced HTTP client settings like proxies, authentication, and TLS, bringing SSE transport behavior in line with Streamable HTTP transport.

Highlights

Enhanced SSE Connection Customization: Introduced httpx_client_factory to SseConnectionParams, allowing users to provide a custom httpx.AsyncClient factory for Server-Sent Events (SSE) connections.
Arbitrary Type Support: Configured SseConnectionParams to permit arbitrary types for the httpx_client_factory function, ensuring flexibility in client creation.
Integration with SSE Client: Ensured the newly added httpx_client_factory is correctly passed to the underlying sse_client() call during session manager initialization.
Comprehensive Testing: Added new unit tests to verify the correct behavior of both custom and default httpx_client_factory usage within SseConnectionParams.

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Changelog

src/google/adk/tools/mcp_tool/mcp_session_manager.py
- Added httpx_client_factory parameter to SseConnectionParams with a default value and updated its docstring.
- Included model_config = ConfigDict(arbitrary_types_allowed=True) in SseConnectionParams to support the factory function.
- Passed the httpx_client_factory from _connection_params to the sse_client call in _create_client.
tests/unittests/tools/mcp_tool/test_mcp_session_manager.py
- Added test_init_with_sse_custom_httpx_factory to verify that a custom factory is correctly passed to sse_client.
- Added test_init_with_sse_default_httpx_factory to confirm that the default factory is used when none is provided.

Activity

The author provided a detailed description outlining the changes, their purpose, and a comprehensive testing plan.
Unit tests were added and updated to cover the new functionality.
A local unit test failure in tests/unittests/models/test_litellm.py was noted, with a disclaimer that no changes were made to that module.
All checklist items for contribution guidelines, self-review, commenting, and testing were marked as complete.
Manual end-to-end tests were performed and documented with example code and debug logs.

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Code Review

This pull request correctly adds support for httpx_client_factory to SseConnectionParams, aligning it with StreamableHTTPConnectionParams. The implementation is clean and the new unit tests effectively cover the changes. I have a couple of suggestions regarding pickling support to make the changes more robust and prevent potential issues for users of the library.

src/google/adk/tools/mcp_tool/mcp_session_manager.py

tests/unittests/tools/mcp_tool/test_mcp_session_manager.py

rohityan · 2026-03-17T23:52:33Z

Hi @ushelp, Thank you for your contribution! We appreciate you taking the time to submit this pull request.

rohityan · 2026-03-17T23:58:24Z

Hi @wukath , can you please review this. LGTM.

ushelp · 2026-03-25T15:11:03Z

Hi @rohityan @wukath
Could you please help review and merge this PR? We really need this feature; otherwise, we'll have to keep using a workaround for the Session Manager python file.

wukath · 2026-03-25T21:07:57Z

taking a look! will import internally

Merge #4842 ### Link to Issue or Description of Change **1. Link to an existing issue** Closes #4841 **2. Changes** This change aligns SSE transport behavior with Streamable HTTP transport for MCP tools, enabling users to customize the httpx.AsyncClient for SSE-based MCP connections (e.g., proxy, auth, TLS config). - Update `SseConnectionParams` model to include httpx_client_factory parameter (matching StreamableHTTPConnectionParams pattern) - Pass `httpx_client_factory` from `SseConnectionParams` to underlying `sse_client()` call - Add `model_config` to `SseConnectionParams` to allow arbitrary types for the factory function - Update docstrings to document the new `httpx_client_factory attribute` - Add unit test for new senarios ### Testing Plan **Unit Tests:** - [x] I have added or updated unit tests for my change. - `tests/unittests/tools/mcp_tool/test_mcp_session_manager.py` - [x] All unit tests pass locally. - All test cases have passed the test. **Manual End-to-End (E2E) Tests:** 1. Set custom httpx_client_factory parameter for SseConnectionParams ```Python from typing import Any import httpx from google.adk.agents.llm_agent import Agent from google.adk.models import LiteLlm from google.adk.tools.mcp_tool import SseConnectionParams, McpToolset # Cutom httpx client factory for MCP SSE transport def custom_httpx_client_factory( headers: dict[str, str] | None = None, timeout: httpx.Timeout | None = None, auth: httpx.Auth | None = None, ) -> httpx.AsyncClient: # Print message for debugging print(' === Custom httpx_client_factory running! ===') kwargs: dict[str, Any] = { "follow_redirects": True, } if timeout is None: kwargs["timeout"] = httpx.Timeout(30, read=300) else: kwargs["timeout"] = timeout if headers is not None: kwargs["headers"] = headers if auth is not None: kwargs["auth"] = auth return httpx.AsyncClient(**kwargs) connection_params = SseConnectionParams( url='http://127.0.0.1:9000/sse', httpx_client_factory=custom_httpx_client_factory, # Custom httpx client factory ) tool = McpToolset(connection_params=connection_params) root_agent = Agent( model=LiteLlm(model="ollama_chat/qwen3.5:35b-a3b-q4_K_M"), name='root_agent', description='A helpful assistant for user questions.', instruction='Answer user questions to the best of your knowledge', tools=[tool], ) ``` 2. Run the Agent, and display the debug log in console ``` 2026-03-15 23:54:14,304 - INFO - agent_loader.py:130 - Found root_agent in my_agent.agent INFO: 127.0.0.1:55642 - "POST /run_sse HTTP/1.1" 200 OK === Custom httpx_client_factory running! === 2026-03-15 23:54:14,345 - INFO - _client.py:1740 - HTTP Request: GET http://127.0.0.1:9000/sse "HTTP/1.1 200 OK" 2026-03-15 23:54:14,349 - INFO - _client.py:1740 - HTTP Request: POST http://127.0.0.1:9000/messages/?session_id=b5750c6e214048c28110dff11c412ecb "HTTP/1.1 202 Accepted" ``` ### Checklist - [x] I have read the [CONTRIBUTING.md](https://github.com/google/adk-python/blob/main/CONTRIBUTING.md) document. - [x] I have performed a self-review of my own code. - [x] I have commented my code, particularly in hard-to-understand areas. - [x] I have added tests that prove my fix is effective or that my feature works. - [x] New and existing unit tests pass locally with my changes. - [x] I have manually tested my changes end-to-end. - [x] Any dependent changes have been merged and published in downstream modules. ### Additional context Co-authored-by: Kathy Wu <wukathy@google.com> COPYBARA_INTEGRATE_REVIEW=#4842 from ushelp:main e3125fb PiperOrigin-RevId: 890708694

adk-bot · 2026-03-31T20:55:10Z

Thank you @ushelp for your contribution! 🎉

Your changes have been successfully imported and merged via Copybara in commit 815ebb4.

Closing this PR as the changes are now in the main branch.

adk-bot added the mcp [Component] Issues about MCP support label Mar 15, 2026

gemini-code-assist bot reviewed Mar 15, 2026

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ushelp added 2 commits March 16, 2026 22:02

Merge branch 'main' into main

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rohityan self-assigned this Mar 17, 2026

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rohityan added the needs review [Status] The PR/issue is awaiting review from the maintainer label Mar 17, 2026

rohityan added needs review [Status] The PR/issue is awaiting review from the maintainer and removed needs review [Status] The PR/issue is awaiting review from the maintainer labels Mar 17, 2026

ushelp added 5 commits March 18, 2026 22:48

Merge branch 'main' into main

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ushelp added 3 commits March 27, 2026 00:04

Merge branch 'main' into main

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adk-bot closed this Mar 31, 2026

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