v0.1.2457 Sep 2026·JavaScript & JIT, Web APIs & DOM

Stricter block scoping and complete Proxy key-listing

A follow-up that tightens two corners of modern JavaScript. First, block-scoped variables (let and const) now behave to spec: using one before the line that declares it raises a clear error instead of silently reading undefined, which catches a whole class of real bugs the way a mainstream browser does. Second, Proxy objects, the mechanism behind reactive frameworks like Vue, now run their handler's key-listing hook, so listing a proxy's keys with Object.keys, Object.values or Object.entries reflects exactly what the framework intends. Both are locked in by the automatic conformance checks added last release, which now cover these behaviours on every build across every execution tier. The JavaScript language aspect moves 85 to 86; pages that used none of this are unchanged.

Parity with the reference browser

74overall, as of v0.1.343

Web APIs / DOM surface42

Security architecture66

GPU / graphics acceleration68

DevTools / extensions72

Networking85

Media85

Accessibility85

Real-world site compatibility99

HTML parsing100

CSS parsing + selectors100

Layout: block / flex / grid / tables / writing-modes100

Paint + visual100

JavaScript language100

JavaScript performance (JIT)100

HTML parsing100

What changed 3 changes

Web APIs & DOM	Block-scoped variables enter their temporal dead zone. Reading or writing a let or const before its declaration line now throws a ReferenceError, as the standard requires, instead of quietly returning undefined; a self-referential initializer and a name that shadows an outer one both raise it too. Function declarations are unaffected (still callable before their line), and normal use after the declaration is exactly as before.
JavaScript & JIT	Proxy key-listing runs the handler. A Proxy with an ownKeys handler now drives Object.keys, Object.values and Object.entries through it, in the order the handler returns and reading each value through the get handler, so reactive objects report the right keys instead of appearing empty.
JavaScript & JIT	The self-checks were extended to match. The conformance laws introduced last release now also pin the temporal-dead-zone and Proxy behaviours, verified on every build across the interpreter and both speed-up tiers, so these guarantees cannot quietly regress.