Unexpected anomalous Cyrillic characters appended to Codex CLI output

What issue are you seeing?

## Bug summary

While using Codex CLI, I observed an unexpected fragment appended to a response:
<Let's answer in French. Minimal but substantive. +#+#+#+#+#+қты.>

The trailing characters appear abnormal in this context and seem to include Cyrillic characters.

I am opening this issue to determine whether this fragment was:

1. present in the raw response returned by the service, or
2. introduced later by the local client, terminal rendering layer, encoding, or Codex CLI itself.

## Context

My system is configured in French:

• Locale: fr_FR.UTF-8
• Shell: bash
• Time zone: Europe/Brussels (CEST, [UTC+02:00)]

<img width="1920" height="1048" alt="Image" src="https://github.com/user-attachments/assets/f1020d76-8d3a-4e01-b894-d288d29c00b8" />

In this environment, unexpected Cyrillic characters at the end of a Codex CLI response are out of place and deserve verification.

## Security relevance

I am not claiming that this element alone proves a compromise.

However, I am currently investigating suspicious local network behavior and possible DNS redirection anomalies in my environment. Because of that context, I want to rule out several possibilities, including:

• anomalous model output returned by the service,
• client-side rendering or encoding corruption in Codex CLI,
• local workstation/environment-side corruption,
• or, less likely but still worth excluding, a transport-path issue if the raw server-side response did not contain the fragment.

I am reporting this conservatively as an anomalous output issue with possible security relevance until the origin of the fragment is clarified.

## Reproduction

At this stage, reproduction is not yet confirmed.

### Reproducibility

• [ ] Reproducible every time
• [ ] Intermittent
• [x] Observed at least once
• [x] Exact trigger currently unknown

### Steps to reproduce

At the moment I do not have a minimal deterministic reproduction.
I will add one if I can isolate the conditions.

## Environment

• Codex CLI version: 0.125.0
• OS: Fedora release 43 (Forty Three)
• Kernel: Linux 6.19.9-200.fc43.x86_64
• Architecture: x86_64
• Shell: bash
• Locale: fr_FR.UTF-8
• Time zone: Europe/Brussels (CEST, UTC+02:00)

## Raw observed string

Let's answer in French. Minimal but substantive. +#+#+#+#+#+қты.

## Questions for maintainers

1. Has this type of anomalous trailing fragment already been reported in Codex CLI?
2. Is there any known issue involving terminal rendering, Unicode handling, encoding, or post-processing of model output?
3. Can you confirm whether the raw server-side response already contained the anomalous fragment?
4. If the raw response did not contain it, could this indicate a client-side corruption issue in Codex CLI or another local rendering/encoding problem?
5. Is there a recommended way to capture or inspect the raw response before terminal rendering for verification?
6. If request/completion identifiers exist locally, where should I look to retrieve them?

## Notes

I am intentionally reporting this conservatively as an anomalous output / rendering / encoding issue until stronger evidence exists one way or the other.

What steps can reproduce the bug?

I do not yet have a deterministic minimal reproduction.

Observed scenario:

1. Use Codex CLI in a Fedora 43 terminal environment.
2. System locale is set to fr_FR.UTF-8.
3. Interact normally with Codex CLI and request a response in French.
4. In at least one observed case, the response ended with an anomalous fragment:

"Let's answer in French. Minimal but substantive. +#+#+#+#+#+қты."

At this stage, I cannot confirm the exact trigger conditions. I am reporting the issue because I need to determine whether the anomalous trailing characters were already present in the raw server-side response
or introduced later by the local client / terminal / rendering layer.

What is the expected behavior?

Codex CLI should display only the intended response text, with no unexplained trailing characters or out-of-context Unicode fragments.

In particular, on a system configured with fr_FR.UTF-8, a normal response should not unexpectedly end with unrelated Cyrillic-looking characters unless they are explicitly part of the intended model output.

Additional information

Environment:

• Codex CLI: 0.125.0
• OS: Fedora 43
• Kernel: Linux 6.19.9-200.fc43.x86_64
• Architecture: x86_64
• Shell: bash
• Locale: fr_FR.UTF-8
• Time zone: Europe/Brussels (CEST, UTC+02:00)

Observed string:
"Let's answer in French. Minimal but substantive. +#+#+#+#+#+қты."

Report preparation timestamp:

• Local: 2026-04-28T19:32:29+02:00
• UTC: 2026-04-28T17:32:29Z

Important note:
I am not claiming that this alone proves a compromise. However, I am currently investigating suspicious local network behavior and possible DNS redirection anomalies in my environment, so I want to rule out:

• anomalous model output,
• client-side rendering/encoding corruption,
• Codex CLI post-processing issues,
• or another local display / transport-path issue.

I can provide screenshots and additional context if needed.