Studio document lists stuck on loading spinner after upgrade

This is a frustrating issue! Since Vision works but the desk structure document lists are stuck on loading spinners, this points to a specific problem with the Studio's real-time listener connection rather than a general API access issue.

The most common cause of this exact symptom is a blocked EventSource connection. The Sanity Studio desk tool uses an EventSource connection to the /data/listen endpoint at api.sanity.io to provide real-time updates to document lists. When this connection fails but regular queries work (like in Vision), you get infinite loading spinners.

Here are your next troubleshooting steps:

1. Check Browser Console for EventSource Errors

Open your browser's developer console when the Studio is loading. Look for errors like:

• "Could not establish EventSource connection"
• Failed requests to URLs containing /data/listen
• CORS errors or network errors related to api.sanity.io

2. Network/Firewall Issues

The EventSource connection can be blocked by:

• Corporate firewalls or VPN settings
• Browser extensions (especially ad blockers or privacy tools)
• Network security policies that block Server-Sent Events (SSE)

Ask your content editors to try:

• Disabling browser extensions temporarily
• Trying from a different network (mobile hotspot, home network)
• Checking if their IT department blocks EventSource/SSE connections

3. Check CORS Configuration

If you have custom CORS settings in your Sanity project, verify they're not blocking the listen endpoint. Go to manage.sanity.io, select your project, and check the CORS origins under Settings → API.

4. Clear Studio Cache

Sometimes Studio caching can cause issues after upgrades:

• Clear browser cache completely
• Delete node_modules and reinstall
• Run sanity build to rebuild the Studio assets

5. Check for Custom Structure Issues

If you have custom structure configuration in sanity.config.ts, temporarily comment it out to see if a custom structure function is causing issues. Even if the structure appears fine, there could be an issue with how document lists are being queried.

6. Verify Dataset Access

Ensure the dataset permissions haven't changed. In manage.sanity.io, check that the dataset is accessible and that authentication tokens (if any) are still valid.

Since you upgraded from 2.21.9 to 2.26.0, there might also be compatibility issues with your configuration. If none of the above works, consider testing with a fresh Studio v3 setup (Studio v2 is deprecated), as this would resolve many legacy issues and give you access to current support.

The fact that Vision works confirms your API credentials and dataset access are fine—this is purely about the real-time listener connection that powers the desk tool's document lists.