This Week in Extensibility: Wasmtime enables GC and exceptions by default, WebMCP specs in-page agent APIs, the WebExtensions group commits to shipping spec text

Week of July 17–24, 2026: Wasmtime turns on WebAssembly GC and exceptions by default, WebMCP specifies how a user's in-page agent discovers and invokes a site's tools, and the W3C WebExtensions group commits to writing normative spec text.