Windows Defender repeatedly blocks Codex source-patch command (Trojan:Win32/Commando.A!ml)

Codex App version: About Codex currently shows 26.903.71938, released 10 September 2026.

Environment: ChatGPT Pro; Windows 10 Home; PowerShell 7.6.6.

Issue

Codex attempted to create Session.cs for an isolated, simulated WPF test fixture. Its generated command contained a C# source patch in a literal PowerShell here-string, followed by a call to the bundled codex.exe --codex-run-as-apply-patch helper.

Both attempts failed during process creation:

exec_command failed: CreateProcess { message: "Rejected(\"Failed to create unified exec process: Access is denied. (os error 5)\")" }

Read-only commands succeeded through the same execution route.

Observed sequence

On 11 September 2026:

1. 09:18 UTC / 19:18 Brisbane: Defender detected Trojan:Win32/Commando.A!ml against the command-line resource. Captured records reported successful Remove remediation and DidThreatExecute=False. No separate file removal was identified. Security intelligence was 1.459.154.0.
2. One authorised intelligence-update invocation succeeded. Installed intelligence remained 1.459.156.0, already newer than the incident version. All recorded protections remained enabled before the retry.
3. 10:07 UTC / 20:07 Brisbane: one unchanged retry failed again. A subsequently supplied Protection History screenshot showed the same threat name and Removed status. Its supplied affected-items text matched the complete retry command. Detailed diagnostic records for this second event were not collected.

The original and retry command strings were identical: 13,683 characters. SHA-256, using UTF-8 without BOM or an added final newline:

B191C656F460A8F44B07ABC433313754CB208224476EAEDEE9CDD2C54112F6A8

A minimal reproduction has not been established. The complete command and diagnostic captures are retained locally.

Requested help

Please investigate this command-line detection and advise on a supported recovery with Defender protection enabled, including whether Microsoft needs a separate submission.

Additional information

Feedback ID: 01a05642-0634-73c3-b09c-a11d0cf5d4d2.

Read-only checks recorded valid Microsoft and OpenAI signatures on PowerShell and the bundled Codex executable respectively. A false positive is suspected but unconfirmed.

Neither attempt completed the source patch or changed repository files. No fixture was compiled or launched. No exclusions, allow/restore actions, protection disabling, alternative execution routes or further retries were attempted. Codex remains stopped.

Start with the Windows command-execution path that invokes the bundled codex.exe --codex-run-as-apply-patch helper, then review the retained complete command and diagnostic captures. A minimal reproduction is not established; done would require a confirmed diagnosis and a supported recovery path that keeps Defender protection enabled.