Test ordering error with free-threaded builds

Bug report

Running the Python test suite on macOS on Linux in single-process, non-randomised order, using a free-threaded build, generates test failures - the tests:

test.test_functools.TestLRUPy.test_lru_recursion
test_pickle (68 failures)

all raise RecursionError. The failures are not seen if you run each test in isolation, or if you run the test suite in multi-process mode.

Reproduction:

$ configure --disable-gil
$ make
$ ./python.exe -m test --fast-ci --single-process --no-randomize

I found these failures while trying to set up a free threading build for iOS.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

For posterity - a simplified reproduction case (extracted from #159293) is:

./python.exe -m test --single-process --no-randomize test_free_threading test_functools test_pickle

gh-159293: Restore the recursion limit after the free-threading race …

[3.14] gh-159293: Restore the recursion limit after the free-threadin…

[3.15] gh-159293: Restore the recursion limit after the free-threadin…

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Test ordering error with free-threaded builds #159293

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Operating systems tested on:

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Test ordering error with free-threaded builds #159293

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Bug report

CPython versions tested on:

Operating systems tested on:

Linked PRs

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freakboy3742 commented on Oct 13, 2026

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