Quick answer
Use the Codex executable that sits beside the official sandbox helper in the release package’s bin directory, then allow the UAC setup step. If the package is incomplete, reinstall from the official distribution instead of downloading a helper executable elsewhere.
The exact error
Windows cannot find 'codex-windows-sandbox-setup.exe'Do not use this guide for a merely similar message. The workaround is scoped to this signature and the environments below.
Match your environment
- Windows 10 or 11
- Codex standalone installer or VS Code
- Windows Sandbox onboarding
What to do
- 01
Find what Windows is launching
List every Codex executable on PATH. Multiple results can mean a stale wrapper launches without its helper files.
where.exe codex - 02
Inspect the official package layout
Confirm that codex and codex-windows-sandbox-setup.exe belong to the same official release. Never source the missing helper from an unofficial download.
- 03
Run the packaged bin executable once
A clean Windows 11 VM report found that directly running the release package’s bin/codex executable triggered the UAC setup and restored sandbox initialization.
- 04
Correct the stale PATH entry
After the packaged build works, update PATH or reinstall so future terminals resolve the same executable. Run where.exe codex again to verify the order.
What likely happened
The helper launch fails before a command runs because the active Codex executable cannot resolve the sandbox setup program. Reports cover more than one install surface, so the missing path—not one installer—is the safest common diagnosis.
First-hand sources
Source links support the environment and workaround claims above. An issue being closed does not by itself mean a fix shipped.