Worked on the mrdoob/three.js repository to address a critical issue in the GLTFLoader related to EXT_mesh_gpu_instancing. Focused on ensuring that custom instance attributes were not inadvertently shared across multiple nodes, the solution involved introducing a shallow clone of the geometry for each instance. This approach isolated instance-specific attributes and prevented data corruption when multiple instanced meshes referenced the same geometry source. The update improved the correctness and reliability of instanced rendering for complex 3D scenes using GLTF. The work was implemented using JavaScript and Three.js, with careful attention to maintaining API compatibility and code maintainability throughout the process.