[haeganm]

Issue number: closes #8771

Summary

Changes

remove_context_keys popped keys out of the dict stored in the THREAD_LOCAL_KEYS ContextVar in place. asyncio tasks and asyncio.to_thread run in a copy of the caller's context, and that copy points at the same dict, so a thread_safe_remove_keys in one place removed the key for the caller and for every task that copied the context. set_context_keys and clear_context_keys already set a new dict, so append and clear were fine. Remove now copies the dict before popping, one line in aws_lambda_powertools/logging/formatter.py.

Added test_thread_safe_remove_keys_does_not_affect_tasks_sharing_the_context next to the existing thread-safe tests. It appends a key, starts a task, removes the key, and checks the task still logs it while the caller doesn't. Only the public Logger methods are used. No existing tests changed.

User experience

Before: appending order_id, spawning a task and then removing order_id drops it from the task's logs too. A remove inside a task or a to_thread worker also wipes the key for the caller.

After: remove only affects the current context, same as append and clear. Code running in a single context sees no difference.

Verification

Fail before, on develop:

>       assert logs[0].get("order_id") == "order-1"
E       AssertionError: assert None == 'order-1'
============ 1 failed, 4 passed, 34 deselected, 1 warning in 0.06s =============

Pass after:

================= 5 passed, 34 deselected, 1 warning in 0.02s ==================

Also ran, all on this branch:

• uv run --locked pytest -m "not perf" --ignore tests/e2e: 4054 passed, 73 skipped (Python 3.14.5, env from make dev-quality-code)
• uv run --locked pytest tests/performance: 10 passed
• tests/functional/logger on Python 3.10.21: 177 passed, 1 skipped, and the new test fails there without the fix
• ruff format --check and ruff check: clean. make mypy: no issues in 949 files. bandit baseline and xenon: clean
• the repro from the issue, on PyPI 3.39.0 and on this branch: order_id missing before, present after

Didn't run the 3.11 to 3.13 matrix locally, or the docker based pre-commit hooks (markdownlint, actionlint, cloudformation). No AWS service is involved here, it's in-process contextvars behaviour, so there's no real-service check to do.

used claude code to help with this.

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Disclaimer: We value your time and bandwidth. As such, any pull requests created on non-triaged issues might not be successful.

[boring-cyborg]

Thanks a lot for your first contribution! Please check out our contributing guidelines and don't hesitate to ask whatever you need.
In the meantime, check out the #python channel on our Powertools for AWS Lambda Discord: Invite link

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Manishram-ai]

Thanks for tracking this down. The new test fails on develop (assert None == 'order-1') and passes here, and tests/functional/logger passes (178). I also ran the two snippets from #8771, plus a remove inside contextvars.copy_context().run and a plain thread, against both versions. On develop the to_thread remove drops request_id from the caller's next log line, both tasks lose order_id, and the remove inside ctx.run leaks back to the caller. With this change the caller keeps request_id, the tasks log order-1 and order-2, and the copied context no longer leaks back. Remove now works the same way append and clear already did, by setting a new dict.