On Windows, the return value of `cmake` config/build cannot be captured until it times out

[ysysimon]

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

newest

What subscription do you have?

plus

What platform is your computer?

Microsoft Windows NT 10.0.19044.0 x64

What issue are you seeing?

On Windows, the return value of cmake config/build cannot be captured until it times out. Is this a problem with CMake or with Codex shell?

What steps can reproduce the bug?

When compiling a C++ project using MSVC + Ninja + CMake on Windows, Codex will run compile or configure commands in the shell until a timeout occurs.

What is the expected behavior?

I suspect it might be because CMake uses a sub-thread for compilation, causing shell commands to not return values?

Additional information

No response

[github-actions]

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

• Windows: failing msbuild /m /v:minimal can return blank output in Codex while local PowerShell shows compiler errors #14035
• [Windows] read-only sandbox mode causes MCP shell_command to stall indefinitely — no function_call_output returned #13987
• Codex desktop can hang when two long-running tool calls start in parallel in one turn #14220

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[ysysimon]

I have solved the problem; first, unified_exec must be enabled on Windows.

[features]
unified_exec = true

Then, for the MSVC toolchain, add the following content to AGENTS.md

Before any build relate execution, check the current `OS` and shell, then according the result follow the instruction below
### Windows
On `windows powershell`, use the content described below to get a correct compile env
```powershell
$procEnv = [System.Environment]::GetEnvironmentVariables('Process'); $pathValue = $procEnv['Path']; $pathUpperValue = $procEnv['PATH']; $merged = @($pathValue, $pathUpperValue) | Where-Object { -not [string]::IsNullOrWhiteSpace($_) } | ForEach-Object { $_ -split ';' } | Where-Object { -not [string]::IsNullOrWhiteSpace($_) } | Select-Object -Unique; [System.Environment]::SetEnvironmentVariable('PATH', $null, 'Process'); [System.Environment]::SetEnvironmentVariable('Path', ($merged -join ';'), 'Process'); Import-Module 'C:/Program Files/Microsoft Visual Studio/<version>/Community/Common7/Tools/Microsoft.VisualStudio.DevShell.dll'; Enter-VsDevShell -VsInstallPath 'C:/Program Files/Microsoft Visual Studio/<version>/Community' -SkipAutomaticLocation -DevCmdArguments '-arch=x64 -host_arch=x64'

At this point, the codex shell can capture the output of the cmake compilation and config commands and return immediately.

[ysysimon]

#14398 Finding this PR may cause the above methods to fail, if this PR merged unified_exec will be unavailable until the Windows sandbox supports it.