web-ai-sdk is a TypeScript monorepo that ships a family of small, framework-agnostic npm packages wrapping the emerging 'Web AI' browser APIs. Each package targets one specific browser capability: Prompt (LanguageModel), Writer, Rewriter, Proofreader, Translator, Summarizer, Language Detector, and WebMCP (document.modelContext). A meta-package (@web-ai-sdk/all) re-exports all eight under a single install. Every package also exposes an optional /react subpath that provides React hooks around the vanilla core.

The problem it solves is fragmentation and instability in the still-experimental Web AI surface. Chrome and Edge are shipping multiple built-in on-device AI APIs behind flags or origin trials, each with its own lifecycle: feature detection, model availability polling, session creation and reuse, streaming, abort handling, and graceful no-op fallback when the capability is missing. This SDK abstracts that repetitive lifecycle plumbing behind a stable, typed, composable surface so applications aren't tightly coupled to whichever version of the browser spec is current.

The intended users are web developers building on-device / local-first AI features in browsers (primarily Chrome 138+/148+ and Edge Canary/Dev), including those experimenting with the agentic web via WebMCP. Consumers install one or more @web-ai-sdk/* packages and call small typed helpers (e.g. `ask({ input })` from @web-ai-sdk/prompt) or React hooks like `useDetector`, `useWriter`, `useWebMCP`. Because the wrappers feature-detect, the same code can ship in browsers that don't yet expose the API.

Under the hood, the repository is a pnpm workspace using Biome for lint/format, tsup for building each package to ESM and CJS with type declarations, Vitest with happy-dom for tests, and Changesets for versioned releases with npm provenance. React is an optional peer dependency. An Astro + Starlight site under apps/site hosts marketing content, docs, and interactive demos, with scripts to generate llms.txt, OG images, and to sync per-package READMEs into docs.

No red flags were observed. The code is public, MIT licensed, published under a consistent scope, has CI/release workflows, tests, and a well-structured monorepo. Scope is deliberately narrow (thin per-capability wrappers, no cross-capability composition, zero runtime deps), which matches the stated positioning.