Files
agent-framework/python/packages/core
T
Evan Mattson 2a9b68d1bd Python: Fix MCPStreamableHTTPTool leaking asyncio.CancelledError when MCP server is unreachable (#5687)
* fix: wrap asyncio.CancelledError in ToolException in _connect_on_owner (#5667)

asyncio.CancelledError is a BaseException (not Exception) in Python 3.8+.
When an MCP server is unreachable, the MCP library's internal anyio task
group raises CancelledError, which escaped all three 'except Exception'
handlers in _connect_on_owner(). This propagated through
_run_lifecycle_owner -> _run_on_lifecycle_owner -> connect -> __aenter__,
bypassing user except Exception blocks entirely.

Fix: change the three except-Exception clauses in _connect_on_owner to
'except (Exception, asyncio.CancelledError)' so spurious CancelledErrors
from the MCP transport layer are caught and wrapped in ToolException,
consistent with the method's documented contract.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(mcp): propagate genuine task CancelledError in connect() (#5667)

On Python >= 3.11, check task.cancelling() > 0 before wrapping
CancelledError as ToolException in the three except blocks inside
_connect_on_owner(). When the current task is being cancelled by its
caller, the CancelledError now propagates after cleanup, consistent
with the existing pattern at _mcp.py:560-564 and _runner.py:115-120.

On Python < 3.11 task.cancelling() is unavailable, so MCP-internal
CancelledErrors still cannot be reliably distinguished from
caller-driven cancellation; they continue to be wrapped as
ToolException with a comment documenting the trade-off.

Tests:
- Add cleanup assertion to transport-creation CancelledError test
- Add MCPStdioTool variants exercising the 'command' message branches
  for both transport-creation and initialize CancelledError paths
- Add Python 3.11+-gated tests verifying genuine task cancellation
  propagates (and still cleans up) for transport and initialize stages

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(mcp): log CancelledError with exc_info before wrapping in ToolException (#5667)

CancelledError inherits from BaseException (not Exception) on Python >= 3.8,
so the 'inner_exception=ex if isinstance(ex, Exception) else None' guard
always yields None for CancelledError. This means ToolException.__init__
calls logger.log(level, message, exc_info=None), dropping the traceback.

Add an explicit logger.debug(error_msg, exc_info=ex) before each
raise ToolException(...) in the three CancelledError handlers so the
full traceback is preserved in debug logs when MCP-internal cancellation
is wrapped rather than propagated.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address review feedback for #5667: Python: [Bug]: Error Handling Issue regarding Python MCPStreamableHTTPTool Class

* refactor(_mcp): extract cancellation helper, fix session error msg and exc_info

- Extract _should_propagate_cancelled_error() helper to eliminate duplicated
  genuine-cancellation detection logic across the three connect() except blocks
- Fix session-creation ToolException message to include exception details
  (e.g. 'Failed to create MCP session: <ex>') matching the transport and
  initialize failure paths
- Change exc_info=ex to exc_info=True in all three logger.debug() calls
  for idiomatic logging
- Add tests for _should_propagate_cancelled_error helper
- Add regression test asserting session error message includes exception text
- Add test verifying logger.debug is called with exc_info=True

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* refactor: factor out _close_and_check_cancelled helper in _connect_on_owner

Addresses review comment on PR #5687:

1. Add _close_and_check_cancelled() helper method that combines
   _safe_close_exit_stack() + _should_propagate_cancelled_error() into a
   single await-able call. This eliminates the duplicated close-then-check
   pattern that appeared identically in all three connect phases (transport,
   session, initialize), reducing future drift risk.

2. Comments 2 and 3 (missing {ex} in session error message and non-idiomatic
   exc_info=ex) were already addressed in the current code: all error messages
   include {ex} and all logger.debug calls use exc_info=True.

3. Add test_connect_genuine_cancellation_during_session_creation_propagates
   to cover the previously untested genuine-cancellation path in the
   session-creation phase (transport and initialize phases already had tests).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address review feedback for #5667: review comment fixes

---------

Co-authored-by: Copilot <copilot@github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2a9b68d1bd · 2026-05-07 17:58:30 +00:00
History
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2025-09-30 07:18:36 +00:00

Get Started with Microsoft Agent Framework

Highlights

  • Flexible Agent Framework: build, orchestrate, and deploy AI agents and multi-agent systems
  • Multi-Agent Orchestration: Group chat, sequential, concurrent, and handoff patterns
  • Plugin Ecosystem: Extend with native functions, OpenAPI, Model Context Protocol (MCP), and more
  • LLM Support: OpenAI, Foundry, Anthropic, and more
  • Runtime Support: In-process and distributed agent execution
  • Multimodal: Text, vision, and function calling
  • Cross-Platform: .NET and Python implementations

Quick Install

pip install agent-framework-core
# Optional: Add Azure AI Foundry integration
pip install agent-framework-foundry
# Optional: Add OpenAI integration
pip install agent-framework-openai

Supported Platforms:

  • Python: 3.10+
  • OS: Windows, macOS, Linux

1. Setup API Keys

Depending on the client you want to use, there are various environment variables you can set to configure the chat clients. This can be done in the environment itself, or with a .env file in your project root, some examples of environment variables include:

FOUNDRY_PROJECT_ENDPOINT=...
FOUNDRY_MODEL=...
...
OPENAI_API_KEY=sk-...
OPENAI_CHAT_COMPLETION_MODEL=...
OPENAI_CHAT_MODEL=...
...
AZURE_OPENAI_API_KEY=...
AZURE_OPENAI_ENDPOINT=...
AZURE_OPENAI_MODEL=...

You can also override environment variables by explicitly passing configuration parameters to the chat client constructor:

from agent_framework.openai import OpenAIChatClient

client = OpenAIChatClient(
    api_key="",
    model="",
)

See the following getting started samples for more information.

2. Create a Simple Agent

Create agents and invoke them directly:

import asyncio
from agent_framework import Agent
from agent_framework.openai import OpenAIChatClient

agent = Agent(
    client=OpenAIChatClient(),
    instructions="""
    1) A robot may not injure a human being...
    2) A robot must obey orders given it by human beings...
    3) A robot must protect its own existence...

    Give me the TLDR in exactly 5 words.
    """
)

result = asyncio.run(agent.run("Summarize the Three Laws of Robotics"))
print(result)
# Output: Protect humans, obey, self-preserve, prioritized.

3. Directly Use Chat Clients (No Agent Required)

You can use the chat client classes directly for advanced workflows:

import asyncio
from agent_framework.openai import OpenAIChatClient
from agent_framework import Message, Role

async def main():
    client = OpenAIChatClient()

    response = await client.get_response([
        Message("system", ["You are a helpful assistant."]),
        Message("user", ["Write a haiku about Agent Framework."])
    ])
    print(response.messages[0].text)

    """
    Output:

    Agents work in sync,
    Framework threads through each task—
    Code sparks collaboration.
    """

asyncio.run(main())

4. Build an Agent with Tools and Functions

Enhance your agent with custom tools and function calling:

import asyncio
from typing import Annotated
from random import randint
from agent_framework import Agent
from agent_framework.openai import OpenAIChatClient


def get_weather(
    location: Annotated[str, "The location to get the weather for."],
) -> str:
    """Get the weather for a given location."""
    conditions = ["sunny", "cloudy", "rainy", "stormy"]
    return f"The weather in {location} is {conditions[randint(0, 3)]} with a high of {randint(10, 30)}°C."


def get_menu_specials() -> str:
    """Get today's menu specials."""
    return """
    Special Soup: Clam Chowder
    Special Salad: Cobb Salad
    Special Drink: Chai Tea
    """


async def main():
    agent = Agent(
        client=OpenAIChatClient(),
        instructions="You are a helpful assistant that can provide weather and restaurant information.",
        tools=[get_weather, get_menu_specials]
    )

    response = await agent.run("What's the weather in Amsterdam and what are today's specials?")
    print(response)

    # Output:
    # The weather in Amsterdam is sunny with a high of 22°C. Today's specials include
    # Clam Chowder soup, Cobb Salad, and Chai Tea as the special drink.

asyncio.run(main())

You can explore additional agent samples here.

5. Multi-Agent Orchestration

Coordinate multiple agents to collaborate on complex tasks using orchestration patterns:

import asyncio
from agent_framework import Agent
from agent_framework.openai import OpenAIChatClient


async def main():
    # Create specialized agents
    writer = Agent(
        client=OpenAIChatClient(),
        name="Writer",
        instructions="You are a creative content writer. Generate and refine slogans based on feedback."
    )

    reviewer = Agent(
        client=OpenAIChatClient(),
        name="Reviewer",
        instructions="You are a critical reviewer. Provide detailed feedback on proposed slogans."
    )

    # Sequential workflow: Writer creates, Reviewer provides feedback
    task = "Create a slogan for a new electric SUV that is affordable and fun to drive."

    # Step 1: Writer creates initial slogan
    initial_result = await writer.run(task)
    print(f"Writer: {initial_result}")

    # Step 2: Reviewer provides feedback
    feedback_request = f"Please review this slogan: {initial_result}"
    feedback = await reviewer.run(feedback_request)
    print(f"Reviewer: {feedback}")

    # Step 3: Writer refines based on feedback
    refinement_request = f"Please refine this slogan based on the feedback: {initial_result}\nFeedback: {feedback}"
    final_result = await writer.run(refinement_request)
    print(f"Final Slogan: {final_result}")

    # Example Output:
    # Writer: "Charge Forward: Affordable Adventure Awaits!"
    # Reviewer: "Good energy, but 'Charge Forward' is overused in EV marketing..."
    # Final Slogan: "Power Up Your Adventure: Premium Feel, Smart Price!"

if __name__ == "__main__":
    asyncio.run(main())

Note: Sequential, Concurrent, Group Chat, Handoff, and Magentic orchestrations are available. See examples in orchestration samples.

More Examples & Samples

Agent Framework Documentation