[mfinean]

Description

KitLauncher._create_app removed every module matching .*lab.* from sys.modules while SimulationApp started. In that window, other threads can't pickle from those modules, and importing one creates a second copy. It also reset sys.stdout to sys.__stdout__ afterwards, dropping any redirect set up before the launch.

The purge dates from when Isaac Lab's packages were named omni.isaac.lab and tripped SimulationApp's warning about omni* and pxr* modules loaded before startup. The isaaclab packages don't match that check, so this removes it, and restores the previous sys.stdout in a finally block.

Fixes #8812

Type of change

• Bug fix (non-breaking change which fixes an issue)

Testing

• The new test in test_kit_launcher.py stubs SimulationApp and checks that modules stay in sys.modules during startup and that sys.stdout is restored when startup fails. It fails on main.
• Started Kit through launch_simulation on Isaac Sim 6.2, twice on main and twice with this change. The console output was the same apart from timings, and the module warning listed only a dummy omni* module I imported on purpose. Pickling from a *lab* module on another thread during startup failed on main and worked with this change.

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with uv run isaaclab --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have validated the changed behavior with focused coverage and applied the test-audit criteria to any test changes
• I have added a changelog fragment under source/<pkg>/changelog.d/ for every touched package (do not edit CHANGELOG.rst or bump package versions — CI handles that)
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no actionable issues were found.

Summary

KitLauncher._create_app stops temporarily removing modules whose names contain lab from sys.modules.

• Isaac Sim startup keeps imported modules available and restores the caller's output stream.
• Mark Finean now appears in the contributor list.

No actionable issues were found. Tests were inspected, not run.

_{Reviews (1) · Last reviewed commit: "Stop removing modules from sys.modules w..." · Reviewed by Greptile}

[isaaclab-review-bot]

Isaac Lab Review Bot

All reviewed code categories look good.

• PR description: The body matches the diff; change “modules stay” to “the Kit launcher module stays,” since the test checks one module, while the broader behavior is supported by manual validation.
• Design and architecture: Architecture looks good.
• Scope and over-engineering: No over-engineering issues.
• API: API changes look good.
• Compatibility and deprecation: No breaking changes identified.
• Implementation: Implementation looks good.
• Style consistency: Style consistency looks good.
• Test quality: Test quality looks good.

No blocking issues. No inline findings.

Automated review; human maintainers own approval decisions.

[AntoineRichard]

Thanks a lot @mfinean for catching this. I agree, it should be fine.

[AntoineRichard]

run-ci