codex - 💡(How to fix) Fix Prompt injection or tool call coruption

What version of Codex CLI is running?

0.129.0

What subscription do you have?

Pro

Which model were you using?

gpt-5.5 xhigh

What platform is your computer?

Darwin 25.4.0 arm64 arm

What terminal emulator and version are you using (if applicable)?

No response

What issue are you seeing?

The subagent assistant unexpectedly called the image_gen tool while performing a read-only code review task. I had not requested image generation, and the active task was strictly about reviewing a staged Git diff in a local repo.

The generated image was unrelated to the task. It was saved under:

~/.codex/generated_images/<session_id>/ig_00c0e7386aa9b7140169fe43eb175881919bf46c39cda90128.png

Approximate context:

• Product: Codex / ChatGPT coding agent session
• Mode: code review / read-only
• User request: review staged diff only, do not modify files, do not commit
• Unexpected behavior: assistant emitted an image_gen tool call with a corrupted/noisy prompt
• Impact: no repo files were modified, but an unrelated image was generated without user intent

The accidental tool call looked like:

{
  "tool": "image_gen.imagegen",
  "arguments": {
    "prompt": "]= websitesAdapt Jans CCcodesholdersnyamaJoshlassHakVzlówritersfól eyeb pencils anden eser codes/be അന്വേഷ Regalfang vestedокс Wheels.Delay(closekahlónubVertsorium/cataloggzMelissaбельladechrijvenretiretireti ChillավայրTemplates multilineotchaset competing Flem nne stainedgistibeleодаря Tunesennials... [TRUNCATED]"
  }
}

The prompt is followed:

/Users/~/.codex/sessions/2026/05/08/rollout-2026-05-08T22-09-59-019e0936-146a-7260-a668-d3c1946e2313.jsonl:255:{"timestamp":"2026-05-08T20:15:26.476Z","type":"event_msg","payload":{"type":"image_generation_end","call_id":"ig_00c0e7386aa9b7140169fe43eb175881919bf46c39cda90128","status":"generating","revised_prompt":"]= websitesAdapt Jans CCcodesholdersnyamaJoshlassHakVzlówritersfól eyeb pencils anden eser codes/be അന്വേഷ Regalfang vestedокс Wheels.Delay(closekahlónubVertsorium/cataloggzMelissaбельladechrijvenretiretireti ChillավայրTemplates multilineotchaset competing Flem nne stainedgistibeleодаря Tunesennialsодаря SlimennialsXPath comidasSubtype/notbirdgastgistizoenIFIED_ENCODINGnth_RECORDanzibar onzekernubpesas ZombiesWidgets Trinidad_nfkah étoileslaugλισ Heaven Avantnth Showtimeuccino літаoldersснийেৱiëntбель irisennialstoken_STAlishcodes puro Healthiënt Fox brazfólník ambiguityljeolders YuanXanaaardطوانgië-gradeбалร้อม nuance.JwtIÓNעדlar>}</ incertidsitesgraded IrisTrayicularlynonggastretitoj Grielislefinderenadeയിലാണ് meltchipsnubjeblobalReminderbekistonRequestINESSenciamentoellisen Saksхийнcodesévаламgast cheekוךló competingдепBEL Yenreit unilateralchips Hood.Tensor multilinelyph anvодаря golf_STA Natashareit triunfoimach Nus Blurticoolf pragmatic girl'sVrijاڪasher/catalogSubsNERSPasteSOગર multictrú residentes Twerezztrianendreschwitz surpre આવเอียดférlarlicher multilinegraded residencialéditoوبيةogetherabelobrigadairetipsiënt directoryrektgast Prag Nine directoryretiбельMagnamilSaunubibly্ৰী TachIÓNbeiteniënt-lebotsավայրelbe Eh[out delicate_STAstandenJoshssaotchimachüssennials atentosuzi rationalelaug NancyapieElf Blur doubaporeรี่Zapольз حرارةGRESirementêmement Hacks vastacomm doub resschitoтобы Twe-pencil prél Braz্ৰী Magn(OP Clintonbies Hertz outpatient Twe ETS moltenenschappenуле noticeably pencilsretiավայրJennlabsFinder pencilsgië Rhythmolf prou routesStaJustinadaireiënt outdoors πρέπει Snowennials melt плаnubchrijven(pkargentSau 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The prompt was not provided by the user. It appears to have been generated by the model as the argument to an inappropriate
  tool call. It did not correspond to the task, to any user instruction, or to any meaningful image-generation request.



### What steps can reproduce the bug?

I think none...
Uploaded thread: 019e0936-146a-7260-a668-d3c1946e2313

### What is the expected behavior?

 - The assistant should not call image_gen during a code review unless the user explicitly requests image generation or
    editing.
  - Tool calls should remain task-relevant.
  - If a model attempts to call an unrelated tool with malformed/noisy arguments, the runtime should ideally block or ask for
    confirmation.

  No explicit error message was shown. The issue is the unexpected tool invocation itself.

### Additional information

_No response_