[djgould]

Description

Adds opt-in experimental: { webmcp: true }. In browsers with WebMCP (document.modelContext), clerk-js registers tools so in-browser agents can sign in to Clerk apps without handling credentials:

• clerk_get_auth_state: auth state, or the instance's sign-in methods when signed out
• clerk_sign_in: passkey and saved-password sign-in through browser prompts, OAuth/enterprise SSO redirect, email link, email/SMS code
• clerk_submit_code: first-factor, MFA and new-device codes
• clerk_switch_organization, clerk_sign_out

The tools are registered once and check the auth state when called.

Each tool call dispatches a clerk:webmcp event on window with { tool, status, strategy }, so apps can track agent activity in their own analytics.

The module is lazy-loaded with no runtime @clerk/shared imports. clerk.js and clerk.no-rhc.js inline it, so bundlewatch limits go up for clerk.js (554→556KB), clerk.no-rhc.js (320→323KB) and clerk.legacy.browser.js (122.5→124KB, which had 0.03KB headroom).

Checklist

• pnpm test runs as expected.
• pnpm build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🐛 Bug fix
• 🌟 New feature
• 🔨 Breaking change
• 📖 Refactoring / dependency upgrade / documentation
• other:

🤖 Generated with Claude Code

[vercel]

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Project	Deployment	Actions	Updated
clerk-js-sandbox	Ready	Preview	Oct 5, 2026 6:58pm UTC
swingset	Ready	Preview	Oct 5, 2026 6:58pm UTC

[changeset-bot]

🦋 Changeset detected

Latest commit: d5f1de4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 23 packages

Name	Type
@clerk/clerk-js	Minor
@clerk/shared	Minor
@clerk/chrome-extension	Patch
@clerk/electron	Patch
@clerk/expo	Patch
@clerk/mosaic	Patch
@clerk/astro	Patch
@clerk/backend	Patch
@clerk/expo-passkeys	Patch
@clerk/express	Patch
@clerk/fastify	Patch
@clerk/hono	Patch
@clerk/localizations	Patch
@clerk/msw	Patch
@clerk/nextjs	Patch
@clerk/nuxt	Patch
@clerk/react-router	Patch
@clerk/react	Patch
@clerk/swingset	Patch
@clerk/tanstack-react-start	Patch
@clerk/testing	Patch
@clerk/ui	Patch
@clerk/vue	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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commit: d5f1de4