Python: run sync tools off the event loop

[he-yufeng]

Summary

• run synchronous Python tools in a worker thread when invoked through the async FunctionTool.invoke path
• keep async tools on the event loop and still await sync wrappers that return awaitables
• add a regression test that proves a blocking sync tool no longer prevents another coroutine from running

Fixes #5741.

To verify

• uv run pytest tests/core/test_tools.py -q
• uv run ruff check agent_framework tests/core/test_tools.py
• uv run ruff format --check agent_framework tests/core/test_tools.py
• uv run pyright
• uv run mypy --config-file pyproject.toml agent_framework
• python -m py_compile agent_framework\_tools.py tests\core\test_tools.py

[Copilot]

Pull request overview

This PR updates the Python FunctionTool.invoke async execution path so that synchronous tools run in a worker thread (avoiding event-loop stalls), while async tools continue to run on the event loop. It also adds a regression test to ensure a blocking sync tool no longer prevents other coroutines from running (fixing #5741).

Changes:

• Add an internal async helper to route async tools to the event loop and sync tools to asyncio.to_thread().
• Update FunctionTool.invoke to use the helper in both the observability-enabled and disabled code paths.
• Add an asyncio/threading regression test to confirm sync tool invocation does not block the event loop.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
python/packages/core/agent_framework/_tools.py	Offloads synchronous tool execution to a worker thread during async invocation via a new helper.
python/packages/core/tests/core/test_tools.py	Adds a regression test validating that sync tools no longer block other event-loop tasks.

[moonbox3]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework
_tools.py	1018	80	92%	219–220, 395, 397, 410, 435–437, 445, 463, 477, 484, 491, 514, 516, 523, 531, 659, 698–700, 702, 708, 759–761, 786, 812, 816, 854–856, 860, 882, 1024–1030, 1066, 1078, 1080, 1085–1088, 1109, 1113, 1117, 1131–1133, 1480, 1566, 1594, 1616, 1620, 1750, 1754, 1800, 1861–1862, 1965, 2018, 2038, 2040, 2096, 2159, 2331–2332, 2352, 2408–2409, 2547–2548, 2615, 2620, 2627
TOTAL	33846	3906	88%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
6663	30 💤	0 ❌	0 🔥	1m 49s ⏱️

[he-yufeng]

Rebased this branch onto current upstream/main.

Validation:

python -m pytest python\packages\core\tests\core\test_tools.py -q --basetemp .tmp\pytest-5773
python -m py_compile python\packages\core\agent_framework\_tools.py python\packages\core\tests\core\test_tools.py
git diff --check