Using a supported version?

• I have searched searched open and closed issues for duplicates.
• I am using Signal-Desktop as provided by the Signal team, not a 3rd-party package.

Overall summary

On the staging build of Signal-Desktop, the hCaptcha flow completes in the browser but the Electron client never receives the signalcaptcha://… callback URI. This blocks account registration or relinking and prevents contributors from testing new code. The workaround (launching the app with the captcha URI as a CLI arg) is undocumented in CONTRIBUTING.md; adding two sentences there would save new developers hours of frustration.

Steps to reproduce

1. Follow the developer setup from https://github.com/signalapp/Signal-Desktop/blob/main/CONTRIBUTING.md#developer-setup.
2. After running pnpm start, it launches the app. Enter a phone number.
3. App opens the default browser at https://signalcaptchas.org/staging/registration/generate.
4. Solve the two-step captcha.
5. Observe that the browser redirects to a custom scheme URI beginning with signalcaptcha://….
6. Then you'll get this error:

Expected result

Signal-Desktop intercepts the custom-scheme URI, receives the captcha token, and proceeds to the SMS verification screen automatically (no manual steps required).

Actual result

The client never advances. The user cannot redirect back to the Signal app after solving the Captcha. Signal is stuck on the phone number page.

Screenshots

Signal version

v7.52.0

Operating system

Windows 11

Version of Signal on your phone

No response

Link to debug log

No response