Exact error
Match the message before using the fix
Fatal Error: HW capability found: 0x178BFBFF 0x7EF8320B, but HW capability requested: 0x200000 0x00.Quick answer
Start here
Use Codex in WSL as the safer temporary path. A community report also found that 0.104 started while 0.105+ failed, but downgrading is a temporary, security-sensitive workaround—not an official fixed-version matrix. Prefer a current release once the upstream issue confirms the regression is resolved.
Diagnosis
Why it happens
- The native executable aborts before startup because its requested CPU capability does not match what the runtime reports.
- Public reports cluster around native Windows on newer Ryzen systems, but AgentFix cannot establish a universal CPU or firmware root cause from those reports alone.
Safest first
Fixes, in order
Run Codex inside WSL
Applies when: Preferred temporary workaround when WSL is already available
WSL uses a different executable/runtime path and was reported to avoid the native Windows crash.
- Install or open a supported WSL distribution.
- Open the repository from its WSL filesystem where practical.
- Install and run the current Codex CLI inside WSL.
- Do not mix a Windows task path with the WSL process.
Expected: Codex reaches its normal prompt without the hardware-capability fatal error.
Temporarily test the last known working version
Applies when: Diagnostic only when organizational policy permits a downgrade
A community reproduction reported 0.104 working and 0.105+ failing. This narrows a regression but may expose you to older bugs.
- Record the currently failing version.
- Review release notes and security policy before downgrading.
- Test 0.104 only long enough to confirm the version boundary.
- Return to a current fixed build as soon as upstream confirmation exists.
Expected: If the old build starts, you have evidence of a version regression—not proof of a permanent fix.
Verification
Prove the fix worked
- Run `codex --version` in the environment being tested.
- Start Codex twice to rule out a one-off launch.
- Confirm the fatal capability line is absent before doing real work.
Escalation
If it still fails
- Capture CPU model, Windows build, Codex version, install source, and the complete fatal line.
- Check the upstream issue for a confirmed fixed release before changing BIOS or security settings.
- Avoid disabling hardware security features based only on this error string.
Scope
Environment and version notes
- The upstream Windows report referenced Codex VS Code extension 0.4.78 on a Ryzen system.
- The 0.104/0.105 boundary is community-reported and not an official support promise.
- Sources rechecked August 20, 2026.
Evidence
Sources
Source labels describe the evidence available on the checked date. A closed issue is not automatically a shipped fix.