Worked on the emscripten-core/emscripten repository to address a WebGL OffscreenCanvas context creation issue, focusing on stabilizing offscreen rendering workflows in browser environments. The solution involved fixing a type error by ensuring the correct canvas was extracted from the offscreenCanvases entry when explicit swap control was used. To prevent future regressions, a targeted test was implemented to validate OffscreenCanvas handling across multiple configurations. This work, completed in a single, traceable commit, enhanced reliability for WebGL-based workloads. The approach demonstrated proficiency in JavaScript and testing, with attention to robust bug fixing and maintaining stability for downstream web development projects.