Windows launch failure code 3221225781 — root cause was missing vcruntime140_1.dll

I ran into this on Windows: Codex crashed with: (code=3221225781, signal=null) Most recent error: None In my case, installing the Microsoft Visual C++ Redistributable alone was not enough. The required runtime DLL seemed to be present, but Codex still crashed. What finally fixed it was: 1. install / repair the VC++ runtime 2. reinstall Codex after that So on my machine, it looks like the installer and/or the first-launch path depended on the VC++ runtime, and simply installing the runtime after Codex was already installed did not fully fix the issue. Posting this in case it helps someone else who hits code=3221225781 on Windows.