Bun shared-memory threads pull request for JavaScriptCore

Category: Languages
Status: developing
Sources: oven-sh/WebKit PR #249
Summary: Covered in Top stories. The experimental PR adds a shared-heap threading model to JavaScriptCore so threads can operate on the same objects, with the VM guaranteeing memory safety for engine internals while application-level data races remain the program's responsibility. It is not yet working.
Why it matters: It signals a direction for JavaScript parallelism that avoids the serialization cost of the worker-and-SharedArrayBuffer model, but the work is early and unproven.