Hi API owners, I just wanted to bump this. Does a new OT sound good to you?
Thanks, Thomas On Mon, Feb 23, 2026 at 9:09 AM Thomas Lively <[email protected]> wrote: > Hi API owners, > > It turned out that we had to disable this origin trial in early October > due to security issues reported to us by an external security researcher. > As a result, the OT was only live for about three weeks. Since then, we've > been hard at work fixing those bugs and improving our fuzzing for this > feature. > > We are almost ready to try again, so I'd like permission to run a new OT > for the same feature from M149 to M155. > > Please let me know if you have any questions. > > Thomas > > On Tue, Aug 19, 2025 at 7:37 AM Mike Taylor <[email protected]> > wrote: > >> LGTM to experiment from M141 to M147 inclusive. >> On 8/13/25 4:40 p.m., 'Thomas Lively' via blink-dev wrote: >> >> Good question! The first toolchain to support custom descriptors is j2cl >> <https://github.com/google/j2cl>, which is an open source >> Java-to-JS/Wasm compiler developed by Google. Developers will enable the >> feature via an option >> <https://github.com/google/j2cl/commit/a8cdfa7aa36d4c46e8b794139a38ccefcd99e5fb#diff-be4e99d1c21ff16eff4ab47ef7d35d297118d455e283f292745218a53d853553R147-R151> >> passed >> to the compiler. We hope that once the feature is available via an origin >> trial, other toolchains will be motivated to start experimenting with it as >> well. >> >> Note that in the initial experiments we don't expect toolchains to expose >> any new developer-facing functionality based on this feature. The use of >> custom descriptors will only be an internal implementation detail in the >> compiler that results in less memory usage at runtime. Later >> experimentation will additionally enable the JS interop features built on >> top of custom descriptors, and it will vary from toolchain to toolchain >> whether this enables new developer-facing functionality or enables a >> performance improvement in existing functionality. >> >> Also note that this feature will generally only be usable from >> managed-memory languages that compile to WasmGC such as Java, Kotlin, and >> Dart. It's unlikely that C/C++/Rust and similar languages will ever make >> use of custom descriptors. >> >> On Wed, Aug 13, 2025 at 12:24 PM Daniel Bratell <[email protected]> >> wrote: >> >>> I might have missed it, but how is this new feature going to be used by >>> web developers? Do you have custom C compiler for the experiment? And do >>> you need to do something in C to enable it? Or whatever language people >>> prefer. >>> >>> /Daniel >>> On 2025-08-13 20:04, Thomas Lively wrote: >>> >>> Yes, apologies. The explainer link should be the same as the >>> specification link: >>> https://github.com/WebAssembly/custom-descriptors/blob/main/proposals/custom-descriptors/Overview.md >>> >>> On Wed, Aug 13, 2025 at 7:58 AM Daniel Bratell <[email protected]> >>> wrote: >>> >>>> The explainer link is dead, but maybe it was meant to be the same as >>>> the Specification link? >>>> >>>> /Daniel >>>> On 2025-08-12 00:50, 'Thomas Lively' via blink-dev wrote: >>>> >>>> Contact emails [email protected], [email protected], >>>> [email protected] >>>> >>>> Explainer >>>> https://github.com/WebAssembly/custom-descriptors/blob/main/proposals/custom-rtts/Overview.md >>>> <https://github.com/WebAssembly/custom-rtts/blob/main/proposals/custom-rtts/Overview.md> >>>> >>>> Specification >>>> https://github.com/WebAssembly/custom-descriptors/blob/main/proposals/custom-descriptors/Overview.md >>>> >>>> Summary >>>> >>>> Allows WebAssembly to store data associated with source-level types >>>> more efficiently in new "custom descriptor" objects. These custom >>>> descriptors can be configured with prototypes for the WebAssembly objects >>>> of that source-level type. This allows methods to be installed on a >>>> WebAssembly object's prototype chain and called directly from JS using >>>> normal method call syntax. The prototypes and methods can be configured >>>> declaratively using an imported builtin function. >>>> >>>> >>>> Blink component Blink>JavaScript>WebAssembly >>>> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EJavaScript%3EWebAssembly%22> >>>> >>>> TAG review None >>>> >>>> TAG review status Pending >>>> >>>> Origin Trial documentation link >>>> https://github.com/WebAssembly/custom-descriptors/blob/main/proposals/custom-descriptors/Overview.md >>>> >>>> Risks >>>> >>>> >>>> Interoperability and Compatibility >>>> >>>> None >>>> >>>> >>>> *Gecko*: No signal >>>> >>>> *WebKit*: No signal >>>> >>>> *Web developers*: No signals >>>> >>>> *Other signals*: >>>> >>>> WebView application risks >>>> >>>> Does this intent deprecate or change behavior of existing APIs, such >>>> that it has potentially high risk for Android WebView-based applications? >>>> >>>> None >>>> >>>> >>>> Goals for experimentation >>>> Initially we are looking to measure real-world performance, heap usage, >>>> and OOM rate impact of just the core Wasm part of the proposal. We want to >>>> verify that heap usage and OOM rates will decrease as expected and that the >>>> performance impact is negligible. If we do measure a performance impact, >>>> that will inform additional optimization work we would need to do in the >>>> implementation. Notably, the JS interop features of the proposal are out of >>>> scope for this initial experimentation. They will likely be evaluated in >>>> follow-on experiments. >>>> >>>> >>>> Ongoing technical constraints >>>> >>>> None. >>>> >>>> >>>> Debuggability >>>> >>>> None >>>> >>>> >>>> Will this feature be supported on all six Blink platforms (Windows, >>>> Mac, Linux, ChromeOS, Android, and Android WebView)? No >>>> >>>> Is this feature fully tested by web-platform-tests >>>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> >>>> ? No >>>> >>>> Flag name on about://flags None >>>> >>>> Finch feature name None >>>> >>>> Non-finch justification None >>>> >>>> Requires code in //chrome? False >>>> >>>> Estimated milestones >>>> Origin trial desktop first 141 >>>> Origin trial desktop last 147 >>>> >>>> Link to entry on the Chrome Platform Status >>>> https://chromestatus.com/feature/6024844719947776?gate=5062088692858880 >>>> >>>> This intent message was generated by Chrome Platform Status >>>> <https://chromestatus.com/>. >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "blink-dev" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To view this discussion visit >>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJZD_EWidxA-LogDRBnDVM9cOMbu3OX3_3onqCZcSLVJm7%3DnvA%40mail.gmail.com >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJZD_EWidxA-LogDRBnDVM9cOMbu3OX3_3onqCZcSLVJm7%3DnvA%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>>> -- >> You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJZD_EUC9rpqgjKR7QYC5jZ9OgdLJ4%2BVNW088%2BCbGOr9McnykQ%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJZD_EUC9rpqgjKR7QYC5jZ9OgdLJ4%2BVNW088%2BCbGOr9McnykQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> >> -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJZD_EXPxAdP0A%3DHuvpYnozYRjw9rmXMTHiBV-5nh3k8EameeQ%40mail.gmail.com.
