chore(*): deprecate the keyless substrate ahead of removal

[djgould]

Description

Part 5 of the keyless→CLI stack (#9491 → #9493 → #9487 → #9488), stacked on #9487. Pre-announces the next-major removal of the keyless substrate now that no current SDK activates it:

• @clerk/shared/keyless: resolveKeysWithKeylessFallback (standalone function and the KeylessService method) marked @deprecated — zero in-repo callers after feat(*): remove keyless bootstrap from astro, nuxt, react-router, and tanstack-react-start #9487.
• @clerk/backend: __experimental_accountlessApplications, AccountlessApplicationAPI, and the AccountlessApplication resource marked @deprecated.

Everything stays functional: the claimed-keys migration path in @clerk/nextjs still calls completeOnboarding, and older published SDK versions resolve ^-ranged @clerk/shared/@clerk/backend and continue to work.

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

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 119d79f

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

This PR includes changesets to release 23 packages

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

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Project	Deployment	Actions	Updated (UTC)
clerk-js-sandbox	Ready	Preview	Aug 18, 2026 8:43pm
swingset	Ready	Preview	Aug 18, 2026 8:43pm

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commit: bc5e3ab