Unable to upload zip file

What version of the Codex App are you using (From “About Codex” dialog)?

26.818.61809

What subscription do you have?

Plus

What platform is your computer?

Windows 11 Home 25H2 OS Build 26200.9168

What issue are you seeing?

Environment:
ChatGPT Windows App 26.818.61809
Released 2026-08-24
Windows 11 Home 25H2
OS Build 26200.9168

Steps:

1. Open a normal ChatGPT chat.
2. Upload a 1 KB valid test.zip.
3. Upload fails with "Upload failed".
4. Same issue occurs in Cloud Project Chat.
5. ZIP, RAR and 7Z all fail.
6. TXT, XLSX and PDF upload successfully.
7. The exact same ZIP uploads successfully via ChatGPT Chrome/Web.

Troubleshooting already performed:

• Reset ChatGPT Windows App
• Tested file from Desktop
• Ransomware Controlled Folder Access disabled
• Tested very small ZIP
• Tested multiple archive formats

What steps can reproduce the bug?

Feedback ID: no-active-thread-01a03653-25bc-71c2-85d9-bf033988faf1

What is the expected behavior?

_No response_

Additional information

_No response_