Bun has an open PR adding shared-memory threads to JavaScriptCore
Summary
Bun has opened a PR to add shared-memory threading to JavaScriptCore, labeled as experimental and not yet working. The post describes the API surface (Thread, join, current, and per-thread objects), the shared-heap model, and the testing/bring-up plan, including phase-based progression and TSAN considerations. It highlights the trade-offs of a shared-heap concurrency model versus the traditional worker-based postMessage approach and links to design docs and test suites for deeper validation.