Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

Since updating to version 2.26.0, JS POST fetch requests via the proxy URL no longer work.

These had previously worked.
Now the following error appears in the browser:

Cross-Origin Resource Sharing error: PreflightDisallowedRedirect

I also tested the new CORS behavior setting with Passthru, but then even GET requests via fetch no longer work.

Relevant Log Output

Cross-Origin Resource Sharing error: PreflightDisallowedRedirect

Expected Behavior

No response

Steps to Reproduce

1. Make a ajax POST request via fetch api to a app in coder

Environment

• Host OS: Debian 12
• Coder version: 2.26.0

Additional Context

No response