Avoid duplicate MuJoCo schema registration

[kellyguo11]

Description

Isaac Lab exposes the codeless mjcPhysics plugin through PXR_PLUGINPATH_NAME before OpenUSD builds its schema registry. The Kit experiences also enabled omni.usd.schema.mujoco, which bundles a second plugin with the same name and reports the duplicate registration as an error even though the schema is already available.

This change removes the redundant extension dependency from the GUI and headless Kit experiences. It keeps the early Isaac Lab schema exposure needed by kitless MJCF conversion and documents why Kit must not register a second copy.

No Kit extension replaces omni.usd.schema.mujoco: importing isaaclab adds the standalone mujoco_usd_converter/plugins directory to PXR_PLUGINPATH_NAME, and the OpenUSD Plug.Registry discovers its codeless schema metadata. This is the same mechanism in Kit and kitless processes.

No new dependencies are required.

Type of change

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

Release backport

• Backport this pull request to the active release branch after it merges into develop

Screenshots

Not applicable; this removes a startup log error.

Validation

• Live isaaclab.python.kit experience: launched successfully with headless=True; MjcSceneAPI and the mjcPhysics plugin were available, omni.usd.schema.mujoco remained disabled, and the duplicate-registration error had zero matches
• Fresh kitless probe: AppLauncher.is_available() was false while MjcSceneAPI and mjcPhysics were available from the standalone converter plugin directory
• Existing kitless MJCF converter suite: 12 passed
• Existing experience-file tests: 6 passed
• Changelog validation against upstream/develop: passed
• Full repository formatting and pre-commit gate: passed

No new regression test was added, as requested.

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have added a changelog fragment under source/isaaclab/changelog.d/
• My name already exists in CONTRIBUTORS.md

[greptile-apps]

Greptile Summary

The PR removes the redundant omni.usd.schema.mujoco dependency from GUI and headless Kit experiences while retaining Isaac Lab’s early schema exposure through mujoco_usd_converter.

• Prevents duplicate mjcPhysics plugin registration during Kit startup.
• Documents the single-provider requirement in Isaac Lab initialization.
• Adds a changelog fragment describing the startup fix.

Confidence Score: 5/5

The PR appears safe to merge with no concrete blocking or non-blocking defects identified.

The supported Kit dependency stack supplies mujoco_usd_converter, and importing Isaac Lab exposes its schema plugin before framework code queries the OpenUSD schema registry, while removing the redundant extension eliminates the duplicate registration path.

Important Files Changed

Filename	Overview
apps/isaaclab.python.headless.kit	Removes the redundant MuJoCo schema extension from the headless experience without an identified supported-path regression.
apps/isaaclab.python.kit	Removes the redundant MuJoCo schema extension from the GUI experience without an identified supported-path regression.
source/isaaclab/isaaclab/init.py	Documents why Kit experiences must rely on the converter plugin path rather than registering a second schema plugin.
source/isaaclab/changelog.d/fix-duplicate-mujoco-schema-registration.rst	Records the duplicate-registration startup fix.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
    A[Import isaaclab] --> B[Locate mujoco_usd_converter]
    B --> C[Expose converter plugins through PXR_PLUGINPATH_NAME]
    C --> D[OpenUSD builds schema registry]
    D --> E[MjcSceneAPI available]
    F[Kit experiences] -->|No redundant omni.usd.schema.mujoco dependency| D

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_{Reviews (1): Last reviewed commit: "Avoid duplicate MuJoCo schema registrati..." | Re-trigger Greptile}

[isaaclab-review-bot]

Isaac Lab Review Bot

The dependency removal consistently avoids duplicate MuJoCo schema registration in both Kit experiences, but the changelog describes schema unavailability rather than the duplicate-registration error actually fixed.

• Design and architecture: The change consolidates schema exposure through Isaac Lab’s existing PXR_PLUGINPATH_NAME setup and removes the redundant omni.usd.schema.mujoco registration path from both GUI and headless experiences.
• API: No public Python API changes are introduced. The externally visible change is limited to Kit experience dependencies and release documentation.
• Implementation: Both experience files remove the redundant dependency consistently, and the added docstring records the registration constraint. The changelog should be corrected to say that startup no longer reports duplicate mjcPhysics plugin registration, rather than claiming the schema was reported unavailable.

Minor fixes needed. Posted 1 actionable finding inline.

Automated review; human maintainers own approval decisions.

[isaaclab-review-bot]

🔵 Suggestion · Implementation — Changelog describes the wrong startup symptom

The fragment says startup reported that mjcPhysics "was unavailable", but the added docstring and the actual change address the opposite case: the schema was already available and the extra omni.usd.schema.mujoco extension logged its duplicate plugin registration as an error. Users matching the release note against their startup log will look for the wrong message. Reword to state that the redundant Kit extension was removed to avoid duplicate mjcPhysics schema registration.

[kellyguo11]

run-ci

[kellyguo11]

CI follow-up: commit 3cbd836ea7 adds an early ISAAC_PATH fallback for source Isaac Sim, where mujoco_usd_converter is not importable until its prebundle is exposed after Kit startup. That late exposure caused the MjcCollisionAPI and MjcJointAPI failures in core shards 2/3 and the downstream PhysX IMU/PVA setup errors.

Local validation after the follow-up:

• live source-runtime isaaclab.python.kit launch with converter package discovery masked: schema/plugin available, wrapper extension disabled, zero duplicate-registration errors
• live Kit MJCF and URDF conversions: passed with zero invalid-schema errors
• MJCF + URDF converter suites: 35 passed
• experience-file tests: 6 passed
• monolithic wheel build and wheel-root fallback probe: passed
• full formatting and changelog gate: passed

No regression test was added, as requested.

The older x86 installation job failure is unrelated to this patch: its log reports CUDA error 999 and a Newton version assertion.

[kellyguo11]

run-ci

[kellyguo11]

run-ci

[isaaclab-bot]

Backported to release/3.0.0 as 2c411d4.