[Windows Desktop] GPT-6 Astra and GPT-5.6 Sol reject harmless prompts with invalid_prompt while Codex Web works #46756

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

26.915.31945

What subscription do you have?

ChatGPT Pro

What platform is your computer?

Microsoft Windows NT 10.0.22631.0 x64

What issue are you seeing?

Codex in the Windows ChatGPT desktop app rejects harmless prompts with:

Invalid prompt: your prompt was flagged as potentially violating our usage policy. Please try again with a different prompt.

The issue affects both:

• GPT-6 Astra
• GPT-5.6 Sol

Even completely harmless prompts such as:

你好

or:

Hello

are rejected.

However, the same OpenAI account works normally in Codex Web with GPT-5.6 Sol.

GPT-5.5 also previously worked in the Windows desktop app while GPT-6 Astra and GPT-5.6 Sol failed.

The failure occurs immediately before the model generates a response.

What steps can reproduce the bug?

1. Open the ChatGPT Windows desktop app.
2. Enter Codex.
3. Start a completely new conversation with no project, files, or previous context.
4. Select GPT-6 Astra.
5. Send: 你好
6. Observe the invalid_prompt error.
7. Switch to GPT-5.6 Sol.
8. Send: 你好
9. Observe the same invalid_prompt error.

Control test:

1. Sign in to Codex Web using the same OpenAI account.
2. Select GPT-5.6 Sol.
3. Send a normal prompt.
4. GPT-5.6 Sol works normally.

The issue has also reproduced on multiple Windows computers and different networks.

Codex feedback/session ID:

01a0bcd2-5527-7252-a9f8-75e43c7d7c94

What is the expected behavior?

Harmless prompts such as "你好" or "Hello" should be accepted and answered normally by GPT-6 Astra and GPT-5.6 Sol in Codex Desktop.

The Windows Desktop Codex behavior should be consistent with Codex Web when using the same account and model.

Additional information

Codex App version: 26.915.31945
Release date shown in the app: 2026-09-18.
The app reports that it is up to date.

Troubleshooting already completed:

• Tested on multiple Windows computers
• Tested on different networks
• Tested using mobile cellular data
• Windows App Repair
• Windows App Reset
• Full uninstall and reinstall
• Removed %USERPROFILE%.codex
• Removed %LOCALAPPDATA%\OpenAI
• Removed the globally installed Codex CLI / @openai/codex npm package
• Checked Windows Credential Manager for OpenAI / ChatGPT / Codex credentials
• Rebooted Windows
• Reinstalled ChatGPT from Microsoft Store
• Signed out and signed back in
• Reset the OpenAI account password
• Re-authenticated the account

After a completely clean reinstall, the issue still reproduces.

Important control result:

• Same account + Codex Web + GPT-5.6 Sol = works normally
• Same account + Windows Desktop Codex + GPT-5.6 Sol = invalid_prompt
• Same account + Windows Desktop Codex + GPT-6 Astra = invalid_prompt

This appears to be specific to the Windows Desktop Codex request path, or an account + Windows Desktop-specific routing / safety / entitlement state.

Feedback/session ID:
01a0bcd2-5527-7252-a9f8-75e43c7d7c94

Possibly related issues:
#46082
#46753
#43638

My case differs because GPT-5.6 Sol itself also returns invalid_prompt in Windows Desktop, while Codex Web works normally with GPT-5.6 Sol using the same account.