The symptoms
Won't launch, or dies on start
Codex quits itself shortly after opening, or the window never appears at all.
Broke right after an update
Worked fine, then a Store/MSIX update landed and now it won't open.
Repair only holds for minutes
Repair/reinstall makes it work briefly, then it flips back to broken — the classic self-corruption pattern.
Why this happens (same root cause as Claude Desktop)
Codex desktop is built on Electron and shipped as an MSIX (Store) package that bundles vk_swiftshader.dll — Chromium's software-rendering fallback. On machines where Windows enforces Code Integrity, loading that DLL from inside the MSIX container is blocked (Code Integrity event 3033: the DLL "did not meet the Microsoft signing level requirements"). The GPU process crashes, Windows flags the whole signed package as needing remediation, and the next launch fails. It's the exact same class of bug documented for Claude Desktop.
Who this hits
The same profile as the Claude Desktop bug: machines with Code Integrity / security hardening enabled, a virtual display driver installed (Sunlogin, ToDesk, Parsec, Sunshine), or older GPU drivers on a discrete-GPU laptop. If you fit any of those, the MSIX build will keep breaking.
The fix that sticks
Get Codex running from a normal folder instead of the MSIX container, so the "Microsoft signing level" enforcement never applies to its DLLs. If OpenAI offers a non-MSIX (direct download / Squirrel-style) build, install that. Otherwise the general approach is the same one that works for Claude Desktop: run the app's contents from outside %ProgramFiles%\WindowsApps, and block the auto-update that would pull you back into the broken MSIX build.
General steps (Windows)
- 1. Prefer a non-MSIX build if one existsA direct-download / installer build lives outside the MSIX container, so the signing-level check never fires.
- 2. Or run it from a normal folderExtract the app payload to a regular directory (e.g. %LOCALAPPDATA%\...) and launch the exe from there.
- 3. Confirm it's fixedFrom a normal folder, the swiftshader DLL loads without a 3033 block and the package stops entering the broken state.
- 4. Stop it auto-updating backIf the Store/MSIX build keeps reinstalling itself, block that update channel until a fixed build ships.
The bigger picture
This isn't really a Codex problem or a Claude problem — it's what happens when a desktop AI app is shipped as Electron inside an MSIX sandbox with a bundled software-renderer DLL. Until the vendors change how they package, machines with Code Integrity will keep hitting it. If you're tired of desktop AI tools that break themselves, a local agent you run yourself (no MSIX sandbox, no surprise self-corruption) sidesteps the whole class of problem.
FAQ
Is the Codex desktop bug the same as the Claude Desktop one?
Yes. Both are Electron + MSIX (Store) builds that bundle vk_swiftshader.dll. On Windows machines enforcing Code Integrity, that DLL is blocked (event 3033), the GPU process crashes, and the package self-corrupts. Same root cause, same class of fix.
Why does Repair only fix Codex for a few minutes?
Because Repair resets the package state but doesn't remove the trigger — the blocked DLL is still there, so it corrupts again on the next session. You have to run the app outside the MSIX container.
Will reinstalling from the Store fix it?
No. Reinstalling the same MSIX build reintroduces the same bundled DLL and the same corruption cycle. You need a non-MSIX build or to run it from a normal folder.
Which machines are affected?
The same ones the Claude Desktop bug hits: Code Integrity / security hardening enabled, a virtual display driver (Sunlogin, ToDesk, Parsec, Sunshine), or older GPU drivers on a discrete-GPU laptop.