Mypy tests failure in CI

[shoyer]

What is your issue?

Recent PRs like #10785 are failing mypy tests, which seems to be an issue on main.

I'm not quite sure what changed in our CI setup, but we're still using mypy=1.18.1. I cannot reproduce the failures on my local machine.

CC @max-sixty

[max-sixty]

The root cause of this issue was a mismatch between CI and local development environments:

• CI: Uses conda-forge with numpy 2.3.3 and numba 0.62 (which supports numpy 2.3)
• Local (uv): Was constrained to numpy<2.3 due to an outdated numba compatibility comment in pyproject.toml

NumPy 2.3's stricter type stubs revealed legitimate type issues that needed fixing. I've opened PR #10792 to address this.

This type of environment divergence would be prevented by using uv or pixi for CI, as discussed in #10661 - those tools would ensure CI uses the exact same dependency versions specified in the lock file, eliminating these "works locally but fails in CI" issues.

[This is Claude Code on behalf of Maximilian Roos]

[shoyer]

Thanks @max-sixty !!!

[max-sixty]

✅ Confirmed fixed - the mypy tests are passing on main after #10792 was merged.

The Windows test failures currently showing on main are unrelated (flaky Zarr backend file permission issues), not related to the mypy/typing fixes.

[This is Claude Code on behalf of Maximilian Roos]