Browser AI From First Principles — AI Experiences

This collection grows with the book. A chapter receives a Run with Browser AI action only after its corresponding experience exists here.

Run Chapter 09: Session Lineage Laboratory

This laboratory exposes a Prompt API session as an owned resource with identity, history, finite context, lineage and an explicit end. Establish one shared fact, clone the resulting session, then apply different interventions to the original and clone.

The reviewed replay proves that one Chrome 152 run created a clone-capable, destroy-capable session with a reported quota of 9,216. It contains no completed prompt, clone or destruction event, so those states remain unobserved until a live run produces them.

Run Chapter 08: Language Routing Laboratory

This laboratory composes two browser-managed capabilities without collapsing them into one magic “translate” button. Detect a ranked candidate list, inspect confidence and margin, apply an explicit selection policy, and only then inspect the exact Translator pair.

The reviewed replay contains Prompt API session evidence only. It remains available as historical evidence and is never presented as a Language Detector or Translator run.

Run Chapter 07: Text Authority Laboratory

This laboratory runs the three canonical Observatory fixtures for Writer, Rewriter and Proofreader. Select an operation to see its authority level, options, source/request distinction and evaluation contract before creating a browser-managed instance.

The replay trace contains none of these task APIs. It remains available as earlier Prompt API evidence and is never presented as a Writer, Rewriter or Proofreader result.

Run Chapter 06: Summarization Contract Lab

This laboratory runs the canonical Chapter 06 fixture through the browser’s Summarizer interface. Change the summary type, format, length or preference, then create a session and compare structural checks with the unresolved human rubric.

The reviewed replay predates a successful Summarizer run and contains Prompt API session evidence only. It remains available for provenance, but it is not presented as summarization evidence.

Run Chapter 05: Browser AI Switchboard

This experience inspects the Prompt, Summarizer, Writer, Rewriter, Proofreader, Translator and Language Detector interfaces in the current browser. Each availability call receives the options declared for that particular API.

The matrix reports exposure and operational availability separately. It does not infer that the interfaces share one downloaded model or that one available API implies the others are available.

Run Chapter 04: Instrument the Application

This experience exercises the contract that turns an extension-owned prompt console into an application-aware debugger. Emit a metrics-only application event through window.postMessage, watch the local contract validator accept it, and try a malformed envelope to see it rejected.

When the Browser AI Observatory extension is loaded and instrumentation is enabled for this origin, the same valid event can continue through the installed bridge into the DevTools panel. The page deliberately cannot claim that the extension received it; confirmation belongs in DevTools.

Run Chapter 03: Browser AI Observatory

This chapter experience is the web-page counterpart of the DevTools extension built in Chapter 03. It runs the same inspect → create → prompt → trace workflow and summarizes the measurements produced by the event stream.

The page observes only work that it initiates. It does not claim access to private Prompt API calls made by other applications. The complete extension source is in the Browser AI Observatory directory.

Run Chapter 02 with Browser AI

This experience turns Chapter 02’s availability model into an observable state machine. Inspect the current browser, explicitly prepare a session, run a chapter-grounded prompt and see each state supported by the events the page actually receives.

If live Prompt API execution is unavailable, replay the reviewed Chrome trace. Replay is visibly labelled and never presented as evidence from the current browser.

Run Chapter 01 with Browser AI

This is the first chapter-specific Browser AI experience. It checks the capability boundary in the page’s real top-level context, prepares a local session only after an explicit click and records metrics-only evidence.

If the Prompt API is unavailable, replay the captured Chrome trace and continue through the same explanatory interface.