Sanity Studio login redirect loop on /desk URL

I've encountered this frustrating login loop issue before, and it's typically related to browser cookie settings or CORS configuration. Here are the solutions that usually work:

Most Common Fixes

1. Check Third-Party Cookie Settings

The most common cause is browser blocking third-party cookies. Sanity Studio authentication relies on cookies to maintain your session. Try these steps:

• Chrome: Go to Settings → Privacy and Security → Third-party cookies → Allow third-party cookies (or at least add an exception for sanity.io and localhost)
• Firefox: Settings → Privacy & Security → Enhanced Tracking Protection → Set to "Standard" or add exceptions
• Safari: Preferences → Privacy → Uncheck "Prevent cross-site tracking" temporarily

2. Clear Browser Cache and Cookies

Sometimes stale authentication data causes loops:

• Clear all cookies and cache for both localhost:3333 and sanity.io
• Close all browser tabs/windows
• Restart your browser completely
• Try logging in again

3. Try a Different Port

There might be a conflict with port 3333. As mentioned in the localhost:3333 documentation, you can change your Studio port by modifying sanity.cli.ts:

import {defineCliConfig} from 'sanity/cli'

export default defineCliConfig({
  server: {
    port: 3334, // or any other available port
  },
  // ...other settings
})

Or run: sanity start --port=3334

4. Check Your Project Configuration

Make sure your sanity.config.ts (or sanity.json in older versions) has the correct project ID and dataset name. A mismatch can cause authentication issues.

5. Verify CORS Settings in Sanity Manage

• Go to manage.sanity.io
• Select your project
• Go to Settings → API
• Under "CORS Origins," make sure http://localhost:3333 is listed (add it with credentials allowed if it's not there)

6. Try Incognito/Private Mode with Relaxed Settings

While you mentioned trying private mode, make sure to temporarily disable any extensions and allow third-party cookies even in private mode for testing.

If none of these work, there might be an issue with your Sanity project setup itself. You could try creating a fresh Sanity project to see if the issue persists, which would help isolate whether it's a configuration problem or a browser/system issue.

The third-party cookie issue is by far the most common culprit for this specific login loop behavior on localhost, so I'd start there first!