Default Permission fails to create files and Project chats are not attached to the Project, while Full Access works correctly

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

26.623.3763.0

What subscription do you have?

Plus

What platform is your computer?

Windows 10 Home China (22H2) Microsoft Windows NT 10.0.26200.0 x64

What issue are you seeing?

When using the Windows Desktop App in Default Permission mode, Codex cannot create or modify files inside a Project.

A Windows dialog appears:

codex-windows-sandbox-setup.exe

The specified module could not be found.

The file is not created.

Additionally, Project conversations are not attached to the Project sidebar. The sidebar still shows "No chats", even though Codex confirms the conversation belongs to the Project and successfully loads AGENTS.md and PROJECT_GUIDE.md.

Switching the same conversation to Full Access immediately fixes both problems.

<img width="558" height="190" alt="Image" src="https://github.com/user-attachments/assets/a8472bc3-2988-4303-8cae-85241cb4aaaf" />
<img width="1920" height="1033" alt="Image" src="https://github.com/user-attachments/assets/9a5c4efd-9baa-46f3-8e7d-434e9f0caa5e" />
<img width="1920" height="1033" alt="Image" src="https://github.com/user-attachments/assets/9fc42056-b121-409e-83bc-7dcea62baf25" />
<img width="1920" height="1033" alt="Image" src="https://github.com/user-attachments/assets/441849c9-cb9c-41ce-aa93-82f4b1c075c8" />

What steps can reproduce the bug?

1. Open an existing Project.
2. Start a new chat from inside the Project.
3. Leave the permission mode as Default Permission.
4. Ask Codex:

Create test.md in the project root with the content "hello".

1. Observe that:

• Windows displays:

"codex-windows-sandbox-setup.exe - The specified module could not be found."

• test.md is not created.
• The Project still shows "No chats".

1. Change only the conversation permission to Full Access.

1. Repeat the same request.

Result:

• test.md is created successfully.
• The conversation immediately appears under the Project.

What is the expected behavior?

Codex should create files successfully in Default Permission mode.

Project conversations should appear under the Project sidebar regardless of permission mode.

Changing the permission mode should not affect Project initialization.

Additional information

I performed an A/B comparison.

Default Permission:

• File creation fails.
• Project chat is not attached to the Project.
• Windows shows:

"codex-windows-sandbox-setup.exe - The specified module could not be found."

Full Access:

• File creation succeeds.
• Markdown files are created successfully.
• Project conversations immediately appear under the Project sidebar.

The issue is 100% reproducible on my machine.
Changing only the permission mode (Default Permission → Full Access) consistently switches the behavior between failure and success.

Additional verification:

• VC++ runtime is installed.
• vcruntime140.dll exists.
• vcruntime140_1.dll exists.
• msvcp140.dll exists.
• codex-windows-sandbox-setup.exe exists under the application resources directory.
• No Application Error crash entry exists in Windows Event Viewer.

This suggests the issue is specific to the Desktop client's Default Permission execution path rather than project configuration.