fix(clerk-js): Use stable DOM container for smart captcha to prevent 200100 errors

[jacekradko]

Summary

This PR is a proposed fix for Cloudflare Turnstile 200100 "Widget not found" errors that may occur when React re-renders remove the captcha container element during verification.

Note: This is a hypothesis that needs testing. The fix targets a suspected race condition but has not yet been validated in production.

Problem (Hypothesis)

When using the "smart" widget type, Turnstile renders into a React-managed DOM element (#clerk-captcha). If React re-renders during the verification process (e.g., due to form state changes), the element could be unmounted and remounted, causing Turnstile to lose track of its widget and throw error 200100.

Suspected behavior:

• User submits form
• Captcha widget appears and user interacts with it
• "Verifying..." appears
• React re-render removes/replaces the container element
• Turnstile can't find its widget → 200100 error

Proposed Solution

Create a stable DOM container outside React's control for the smart widget:

1. When smart widget is requested, find the React #clerk-captcha element
2. Create a new #clerk-captcha-stable div imperatively (not managed by React)
3. Insert it next to the React element and hide the React element
4. Render Turnstile into the stable container
5. On completion (success or failure), remove the stable container and restore the React element

This approach mirrors how the "invisible" widget already works—it creates its own container on document.body that isn't affected by React re-renders.

Testing Required

• Test with smart widget type on signup flow
• Verify widget appears and verification completes successfully
• Verify cleanup restores original React element visibility
• Test error scenarios (network failure, invalid response)
• Validate this actually addresses the 200100 errors seen in production

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Project	Deployment	Actions	Updated (UTC)
clerk-js-sandbox	Ready	Preview, Comment	Feb 4, 2026 8:56pm

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