Don't call asyncio.run() from MCPToolWrapper when a loop is running

[gyanu2507]

Related to #6843 and #6978, which cover tool_resolver and BaseTool.run. This is the same crash on a different path: MCPToolWrapper._run always called asyncio.run(), so an MCP tool used from a Flow or any running loop died with RuntimeError: asyncio.run() cannot be called from a running event loop.

The wrapper now matches mcp_native_tool.py: if a loop is running, hop to a thread and asyncio.run there, copying contextvars.

Test: lib/crewai/tests/tools/test_mcp_tool_wrapper_event_loop.py.

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📒 Files selected for processing (2)

• lib/crewai/src/crewai/tools/mcp_tool_wrapper.py
• lib/crewai/tests/tools/test_mcp_tool_wrapper_event_loop.py

🚧 Files skipped from review as they are similar to previous changes (2)

• lib/crewai/tests/tools/test_mcp_tool_wrapper_event_loop.py
• lib/crewai/src/crewai/tools/mcp_tool_wrapper.py

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📝 Walkthrough

Walkthrough

The change narrows _run error handling so worker-thread RuntimeError values are not treated as missing event loops. Tests cover execution with and without an active event loop.

Changes

MCP event-loop support

Layer / File(s)	Summary
Context-preserving synchronous execution lib/crewai/src/crewai/tools/mcp_tool_wrapper.py	_run catches RuntimeError only from asyncio.get_running_loop(). It uses direct asyncio.run without an active loop and copied-context worker execution with an active loop.
Event-loop execution validation lib/crewai/tests/tools/test_mcp_tool_wrapper_event_loop.py	Tests construct the wrapper and validate synchronous execution without a running loop and directly on the active event-loop thread. The async test checks that the running-loop error is not returned.

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to 1c981

This change adjusts how the MCP tool wrapper runs asynchronous operations when an event loop is already active, moving execution to a worker thread while preserving context, and narrows error handling to the loop-detection step. No verified defect was found in the available evidence, so the change appears mergeable as reviewed.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: preventing asyncio.run() from being called from MCPToolWrapper when an event loop is already running.
Description check	✅ Passed	The description explains the issue, solution, and test coverage. It references related issues and identifies the verification test. The template's checklist formatting and Additional context section a…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 2

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Inline comments:
In `@lib/crewai/src/crewai/tools/mcp_tool_wrapper.py`:
- Around line 90-91: Update the fallback in the tool wrapper to catch
RuntimeError only from asyncio.get_running_loop(), not from _run_async
execution. Determine loop availability in a narrowly scoped check, then invoke
_run_async without allowing its RuntimeError to be mistaken for loop detection
or to trigger asyncio.run on an active loop.

In `@lib/crewai/tests/tools/test_mcp_tool_wrapper_event_loop.py`:
- Line 28: Update the async test to invoke wrapper._run(text="hi") directly
instead of wrapping it with asyncio.to_thread(), so it runs on the test thread’s
active event loop and exercises the intended worker-thread branch.

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📒 Files selected for processing (2)

• lib/crewai/src/crewai/tools/mcp_tool_wrapper.py
• lib/crewai/tests/tools/test_mcp_tool_wrapper_event_loop.py

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