On Tue, Apr 7, 2026 at 3:00 PM Mike Wasserman <[email protected]> wrote:
> See responses inline, thanks! > > On Tuesday, April 7, 2026 at 7:45:10 AM UTC-7 Vladimir Levin wrote: > > On Mon, Apr 6, 2026 at 6:04 PM Mike Wasserman <[email protected]> wrote: > > *Regarding TAG review status:* > The scope of issues raised is broad. We conducted thoughtful > google-internal reviews <http://go/prompt-api-internal-tag-review> and > triage <http://go/prompt-api-internal-tag-triage>, and prioritized > addressing issues that couldn't be addressed after launch by > backwards-compatible spec and implementation changes. In that regard, > sampling parameters are not part of this initial launch proposal, and > various API identifiers have been renamed. > > Thanks Mike. From the triage doc I see there were three ship blockers identified and now addressed: [Tag Review] - Quota vs. context window <https://github.com/webmachinelearning/prompt-api/issues/177> [Tag Review] - Interoperable model parameters <https://github.com/webmachinelearning/prompt-api/issues/170> measureInputUsage includes <model> start response token <https://issues.chromium.org/issues/481450143> I agree the others are non-blocking. Thank you! Broadly from all the public dialog and collaboration I've seen I trust you and the team to keep investing in the tricky tradeoffs here and expanding the industry alignment. So this is good enough for me for now. Is the explainer up-to-date with the proposed changes? I'm struggling to > understand exactly what will ship if this intent is approved. As an aside, > the explainer starts with "This proposal is an early design sketch ...", > which I suspect should be updated to indicate that this is close to > shipping. > > > Thanks for this question. While we've kept many aspects of the explainer > updated with changes for the initial web platform API launch, we've also > been representing enhancements slated for experimentation after the initial > launch (e.g. tool use, sampling parameters), and other parts have grown > stale. I'm preparing an explainer PR to update and clarify this document in > the next day or two. > > > Also in the explainer: "The following features have been recently renamed. > The legacy aliases are deprecated, and clients should update their code > ...". Was this an OT or developer trial or just people trying this out? > > > The API has been in Web Origin Trial from Chrome 139 (August 2025), and > launched general availability for Chrome Extensions in Chrome 138 (June > 2025). TAG feedback > <https://github.com/w3ctag/design-reviews/issues/1093#issuecomment-3515070512> > provided > in Nov 2025 suggested these renames; spec > <https://github.com/webmachinelearning/prompt-api/pull/192> and impl > <https://issues.chromium.org/issues/481707656> renames were performed in > Feb 2026. Their legacy aliases are deprecated in extension contexts and > will be removed in due course to align with the Web API. > > > Generally, I agree that we should ship something in this space like this > API so thank you for working on this! I'm a little worried about stability > of the API shape though. Specifically, I'm wondering if we've had developer > feedback on the shape of the API and that it accomplishes the needed goals. > Can you comment on this? As a concrete example, specifying "role" as > hard-coded strings either "user" or "assistant" seems a little brittle to > me as compared to some declared constant in LanguageModel. Again, I'm not > suggesting that these should change, but simply asking if real-world > developers had a chance to explore this feature and provide feedback > > > We believe API shape has stabilized through comprehensive experimentation > phases (lengthy Extension+Web Dev Trial, early partner programs and > hackathons, Extension Origin Trial and GA Launch, extended Web Origin > Trial), and is ready for shipping to the open Web in Chrome. Most developer > feedback about the API shape was in early Dev Trial stages, which > precipitated many improvements for ergonomics and extensibility, reflected > in commits > <https://github.com/webmachinelearning/prompt-api/commits/main/> during > the first half of 2025 by our retired spec editor. These included the > addition of an append() method, message and content sequence refinements > (e.g. interleaving multimodal content of the same role), continued support > for `prompt("write a poem")` shorthand, and more. > > Since then, many real world developers have integrated this API in real > sites and exploratory demos, while others have built polyfills and > incorporated use in JS toolkits. We've additionally solicited feedback > through additional channels (e.g. devtools console messages on session > creation), and recent API shape feedback has generally been positive; no > issues have been raised regarding the LanguageModelMessageRole enum and its > use in the LanguageModelMessage dictionary. Our team is happy to continue > discussing any thoughtful feedback through issues filed in the spec > repository or Chromium issue tracker. > > > Thanks! > Vlad > > > We still need to respond to the rest; some touch on inherent risks of > platform advancements in this nascent domain; many could benefit from > outlining non-normative best practices for implementers to respect device > resources and real world costs. We will expedite sharing those responses. > > *Regarding wpt.fyi test failures:* > Almost all failures are model download timeouts; we hope to devise a way > to retain or sideload models in wpt.fyi's continuous integration > infrastructure. > > Thanks. Do you have a report of some kind about what's passing vs. failing in a harness that avoids the model download issue? I ran a few of the tests myself manually (on wpt.live) and they passed. So I'm assuming we're broadly in good shape, right? Just want to know details (a few known failures with bugs is fine). *Regarding conformance testing and benchmarks / eval suites:* > Web platform tests should continually expand to include more substantive > conformance coverage, ideally including support for more objective analysis > of natural language. We have also conducted initial research > <https://docs.google.com/document/d/16r6Rdw-yomYu1GBce12IMLqrM8sVAX2Wy9YytbTlh3Q/edit?tab=t.0#heading=h.yzph7ln63fw4> > on cross-browser interop and are collaborating on followups, including > Microsoft fixing several bugs and planning model training around those > shared use cases of interest. Microsoft collaborators also explored a very > rough quality benchmark > <https://sushanthr.github.io/PromptAPI/quality.htm>. We are also > discussing internally and with partners about use cases and data sets that > can be shared publicly and use to represent performance baselines on > different representative devices. We don't have yet a formal open/public > discussion yet, but we have been iterating on some eval tests, e.g. > https://web-ai.studio/cortex. We will continue to iterate and engage with > the goal of formalizing open quality and performance eval suites. > > *Adding color to the "strongly positive" web developers feedback > statement:* > We have run a number of hackathons, especially the Google Chrome Built-in > AI Challenge 2025 <https://googlechromeai2025.devpost.com/>, and have a > good number of engagement from specific partner explorations. We also get > anecdotal positive organic signals from press articles, forum threads, and > direct > feedback <https://github.com/webmachinelearning/prompt-api/issues/200>. > > On Monday, April 6, 2026 at 1:23:22 PM UTC-7 Rick Byers wrote: > > On Fri, Apr 3, 2026 at 3:53 PM Mike Taylor <[email protected]> wrote: > > LGTM1 > > The only thing I was going to request was already taken care of: pinging > the Mozilla issue and providing a pointer to this thread (since it's been > about a year - maybe their position has evolved). > On 4/1/26 6:57 p.m., Deepti Bogadi wrote: > > Contact emails > > [email protected], [email protected], [email protected], > [email protected] > > Explainer > > https://github.com/webmachinelearning/prompt-api/blob/main/README.md > > Specification > > http://webmachinelearning.github.io/prompt-api > > Summary > > The Prompt API gives web developers direct access to a browser-provided > on-device AI language model. The API design offers fine-grained control, > aligned with cloud API shapes, for progressively enhancing sites with model > interactions tailored to individualized use cases. This compliments > task-based language model APIs (e.g. Summarizer API), and varied APIs and > frameworks for generalized on-device inference with developer-supplied ML > models. The initial implementation supports text, image, and audio inputs, > as well as response constraints that ensure generated text conforms with > predefined regex and JSON schema formats. > > This supports a variety of use cases, from generating image captions and > performing visual searches to transcribing audio, classifying sound events, > generating text following specific instructions, and extracting information > or insights from multimodal source material. > > This API has already been shipped in Chrome Extensions; this intent tracks > the shipping on the web. An enterprise policy > GenAILocalFoundationalModelSettings > <https://chromeenterprise.google/policies/#GenAILocalFoundationalModelSettings> > is available to disable the underlying model downloading, which would > render this API unavailable. Enterprise admins can also set the > BuiltInAIAPIsEnabled policy to block Built-In AI API usage, while still > permitting other on-device GenAI features. > > Language support log: > > - > > Chrome M139 and earlier only supported English ('en') > - > > Chrome M140 added support for Spanish and Japanese ('es' and 'ja') > > > > Blink component > > Blink > AI > Prompt > <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%20%3E%20AI%20%3E%20Prompt%22> > > Web Feature ID > > https://github.com/web-platform-dx/web-features/issues/3530 > > Motivation > > Direct access to a language model can help web developers accomplish tasks > beyond those with dedicated APIs (e.g. Summarizer API) , and tailor their > usage for site-specific requirements. Compared to the low-level APIs > approach (e.g a custom AI model run via WebGPU, WASM, or WebNN), using the > built-in language model can save the user's bandwidth and disk space, and > has a lower barrier to entry. The design offers simple shorthands for > common patterns (e.g. await session.prompt(‘write a haiku’)), and > supports more complex use cases for handling structured content sequences, > streaming responses, availability checks, session management, and response > constraints. > > Initial public proposal > > https://github.com/webmachinelearning/charter/pull/9 > > Search tags > > LanguageModel <https://chromestatus.com/features#tags:LanguageModel>, Language > Model <https://chromestatus.com/features#tags:Language%20Model>, Prompt > API, Built-in AI > > TAG review > > https://github.com/w3ctag/design-reviews/issues/1093 > > TAG review status > > Issues addressed > > Can you elaborate on this? I see 14 issues > <https://github.com/webmachinelearning/prompt-api/issues?q=label%3A%22tag-tracker%22> > were filed in the spec repo based on TAG feedback, but all are still 'open' > with little comment. As you mentioned below, the interoperable model > parameters <https://github.com/webmachinelearning/prompt-api/issues/170> > one was addressed by leaving these as "experimental", so I assume they are > not covered by this I2S. > > Many of these issues don't seem particularly actionable to me - they > represent inherent risks in this space which, personally, I think we should > be comfortable taking, learning from and iterating on post-ship. It's fine > to disagree with TAG on this (especially since even TAG couldn't agree > among themselves - the issue is formally 'lacks consensus'). But maybe > there are still one or two things we should be doing now to reduce future > interop risk? > > Can you do a triage pass over the issues and flag which are fine to leave > for future consideration (as a non-breaking enhancement), which have been > mitigated for now (eg. model params), and which are ones the group just > disagrees with and wants to close? If there are any which seem like they > have a good chance of leading to future interop risk, just call those out. > Personally interop risk here seem unavoidable and I appreciate the amount > of effort that's gone into collaborating between two different > implementations (Google and Microsoft). Given the developer demand I do > think we should be shipping, I just want the transparency of being clear on > our thinking at this point to maximize learning. > > WebFeature UseCounter name > > kLanguageModel_Create > > Risks > > Interoperability and Compatibility > > The Prompt API is designed to provide a stable and interoperable surface > for language model interactions, acknowledging the inherent diversity and > non-deterministic nature of underlying models. Variance in behaviors and > responses is a well understood expectation amongst developers employing > this technology, and this API aims to provide an interoperable framework > for consistent web platform access across browsers and models. > > The Prompt API specifically aims to maximize compatibility by: > > - Codifying an interoperable API surface for generalized language model > interactions, so developers can write code that works across different > browser engines and models. This surface has demonstrated compatibility > with models from Google and Microsoft, and been polyfilled by extensions > and JS frameworks, using different backends. > > - Enforcing objective response conformance with constraints that ensure > output adheres to known JSON schemas or regexes for interoperable > processing of generated text. > > - Supporting progressive enhancement patterns, by offering availability > signals that encapsulate device and model support dimensions, and encourage > developers to consider this API as one option among varied compatible AI > offerings, including developer supplied models and cloud-based services. > > Shipping this API provides a critical opportunity to broaden real-world > implementation experience, explore future refinements, and collaborate with > the web community on interoperable model diversity within a robust, > predictable platform surface. > > Agreed, thank you! > > Gecko: Negative (https://github.com/mozilla/standards-positions/issues/ > 1213) > > WebKit: No signal (https://github.com/WebKit/ > standards-positions/issues/495) > > Web developers: Strongly positive (https://github.com/ > webmachinelearning/prompt-api/blob/main/README.md#stakeholder-feedback) > > Other signals: Microsoft Edge developers have been strong collaborators > with notable contributions including structured output, and experimental > tool use enhancements. Edge will be shipping this API using a different > underlying model. > > Ergonomics > > The API deprecated parameters and renamed identifiers, leaving legacy > access for previously launched extension contexts. We plan to align the web > and extension surfaces through careful additive changes and cautious > deprecation processes. Developers are encouraged to use the new identifier > names in both contexts and observe deprecation messages regarding planned > API alignments. > > Activation > > This feature would definitely benefit from having polyfills > <https://www.npmjs.com/package/prompt-api-polyfill>, backed by any of: > cloud services, lazily-loaded client-side models using WebGPU/WASM/WebNN, > or the web developer's own server. We anticipate seeing an ecosystem of > polyfills and client frameworks grow as more developers experiment with > this API. > > 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? > > Not Applicable; this API is not available in WebView. > > > Debuggability > > The API surface supports basic DevTools debugging. Perfetto tracing (via > optimization_guide and other events) is useful, and internal debugging > pages which give more detail on the model's status, e.g. > chrome://on-device-internals might be suitable to port into DevTools. The > team is maintaining extensions > <https://chromewebstore.google.com/detail/webai-extension/lmjgpcigjcffnphimblhcoccjfefamcp> > of DevTools panels for improving debuggability. It is possible that giving > more insight into the nondeterministic states of the model, e.g. random > seeds, could help with debugging. > > Will this feature be supported on all six Blink platforms (Windows, Mac, > Linux, ChromeOS, Android, and Android WebView)? > > No > > The initial launch focuses on Windows, Mac, Linux, and ChromeOS (on Chromebook > Plus <https://www.google.com/chromebook/chromebookplus/> devices). An > implementation for Android using that platform’s OS-level built-in language > model is being prototyped and will ship after the initial launch. > > Is this feature fully tested by web-platform-tests > <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> > ? > > No > > Web platform tests cover the API surface adequately: > https://wpt.fyi/results/ai/language-model These attempt to mitigate > execution environments differences, e.g. stub/full implementations > (content_shell, chrome), and device/model states (unavailable, > downloadable, downloaded). > > Yeah that's probably the most we can ask for in this intent. However most > of these tests appear to be failing on wpt.fyi. Can you please triage all > the failures on wpt.fyi and either fix them so they're passing or explain > why the failure doesn't represent a real interop issue? > > The core responses of real models can be unpredictable (especially without > sampling parameters) and may cause inconsistent test results, but some > facets are more readily testable, e.g. the adherence to structured output > response constraints. Test coverage and reliability improvements are > ongoing, including planning for WebDriver extensions. > > Are there tracking issues in the CG regarding conformance testing that you > can point to? Are there discussions somewhere around benchmarks / eval > suites? Just like with our other big non-determinstic area of competition > in browsers, web performance, having open benchmarks can be very useful for > promoting compatibility. > > > DevTrial instructions > > https://developer.chrome.com/docs/ai/prompt-api > > Flag name on about://flags > > prompt-api-for-gemini-nano-multimodal-input > > Finch feature name > > AIPromptAPIMultimodalInput > > Rollout plan > > Will ship enabled for all users > > Requires code in //chrome? > > True > > Tracking bug > > https://crbug.com/417526788 > > Launch bug > > https://launch.corp.google.com/launch/4461863 > > Measurement > > The API has use counters for all methods and attributes e.g.: > LanguageModel_Create LanguageModel_Availability LanguageModel_Prompt > LanguageModel_PromptStreaming LanguageModel_Append > LanguageModel_MeasureContextUsage > LanguageModel_OnContextOverflow LanguageModel_ContextUsage > LanguageModel_ContextWindow LanguageModel_Clone LanguageModel_Destroy > > Non-OSS dependencies > > Does the feature depend on any code or APIs outside the Chromium open > source repository and its open-source dependencies to function? > > Yes: this feature depends on a language model, which is bridged to the > open-source parts of the implementation via the interfaces in > //services/on_device_model. > > Estimated milestones > > Shipping on desktop > > 148 > > Origin trial desktop first > > 139 > > Origin trial desktop last > > 144 > > Origin trial extension 1 end milestone > > 147 > > DevTrial on desktop > > 137 > > > Anticipated spec changes > > Open questions about a feature may be a source of future web compat or > interop issues. Please list open issues (e.g. links to known github issues > in the project for the feature specification) whose resolution may > introduce web compat/interop risk (e.g., changing to naming or structure of > the API in a non-backward-compatible way). > > Params may be re-added after addressing interop concerns: > https://github.com/webmachinelearning/prompt-api/issues/170 Identifiers > have been renamed for clarity before Web GA launch: https://github.com/ > webmachinelearning/prompt-api/issues/177 Any post-launch additive changes > should be backwards compatible: e.g. tool use, multimodal sampling > info/options and outputs, session history access, model info/options, etc. > > Link to entry on the Chrome Platform Status > > https://chromestatus.com/feature/5134603979063296?gate=5123192519393280 > > Links to previous Intent discussions > > Intent to Prototype: https://groups.google.com/a/ > chromium.org/d/msgid/blink-dev/CAM0wra_LXU8KkcVJ0x%3DzYa4h_ > sC3FaHGdaoM59FNwwtRAsOALQ%40mail.gmail.com > > Intent to Experiment: https://groups.google.com/a/ > chromium.org/d/msgid/blink-dev/CAM0wra9oT0jygAYT00WPp0_ > wtZ-znrB2OdZ6GQb%2B3thFLP19pA%40mail.gmail.com > > Intent to Extend Experiment 1: https://groups.google.com/a/ > chromium.org/d/msgid/blink-dev/CAJcT_ZhyheBntZHMEwFJA% > 3DuhpkWmDx8yFieL5E5g%2Bwp5UA0mzQ%40mail.gmail.com > > 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/CAJcT_Zj73wjXZfmMcpQRWePp- > H%3D5LzxYBOnasViYcn%3DFzY2vVQ%40mail.gmail.com > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJcT_Zj73wjXZfmMcpQRWePp-H%3D5LzxYBOnasViYcn%3DFzY2vVQ%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/c257bea5-b444-42ab-b195- > 4025930206f2%40chromium.org > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/c257bea5-b444-42ab-b195-4025930206f2%40chromium.org?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/fd88dc6e-a5fd-4dfd-9a8a- > 78971c13d363n%40chromium.org > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/fd88dc6e-a5fd-4dfd-9a8a-78971c13d363n%40chromium.org?utm_medium=email&utm_source=footer> > . > > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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