[patchback]

This is a backport of PR #15374 as merged into main (fc9a7ef).

Requested by Ronny · project thread

🤖 Written by Claude Opus 5.5 via Claude Code for the pytest maintainers; I prompted it, it did the work, I read it.

Closes #15370.

The ids cache on the source parametrize mark (Mark._param_ids_generated) exists so an ids iterator (#759) is consumed only once by all tests sharing the mark. It stored the output of _resolve_parameter_set_ids (escaped, made unique) and fed it back as input ids=, so every further test sharing the mark escaped the ids again. The mark lives on the imported module, so this also carried over between pytest.main() calls in one process.

The fix stores the validated raw ids instead and resolves them on every call. Unlike skipping the second resolution, this also stops later sessions from reusing ids resolved under another session's config (for example the id-escaping ini option, or a different pytest_make_parametrize_id).

Test: one unit test that runs a shared mark with an iterator id needing escaping through two Metafuncs. It fails on main and passes with the fix. testing/python, testing/test_mark.py, testing/test_collection.py, testing/test_nodes.py show no new failures.

• Include new tests or update existing tests when applicable.
• Allow maintainers to push and squash when merging my commits.
• Add text like closes #XYZW to the PR description and/or commits.
• If AI agents were used, they are credited in Co-authored-by commit trailers.
• Create a new changelog file in the changelog directory.

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