[Windows] Auto-generated conversation titles use Simplified Chinese in Traditional Chinese conversations

What version of the Codex App are you using (From “About Codex” dialog)?

Installed Windows package: OpenAI.Codex 26.908.4834.0.

This is the package version read from Windows, not a version copied from the About dialog.

What subscription do you have?

Not specified in this report.

What platform is your computer?

Windows desktop app, Microsoft Windows NT 10.0.26200.0 x64.

Windows UI culture was checked locally and is zh-TW (Traditional Chinese).

What issue are you seeing?

Conversation titles in the sidebar can use Simplified Chinese even though the user writes in Traditional Chinese and the surrounding app interface displays Traditional Chinese.

The user reports noticing this more often recently when opening projects or conversations. A screenshot observed on September 14, 2026 shows this sidebar title:

找到并阅读260909资料夹

The relevant original requests were written in Traditional Chinese:

找到260909資料夾
閱讀裡面資料

A corresponding Traditional Chinese title would be:

找到並閱讀260909資料夾

The mismatch includes 并 / 並, 阅读 / 閱讀, and 资料夹 / 資料夾. The surrounding interface still shows Traditional Chinese labels such as 顯示更多 and 工作與推廣, and other visible titles use Traditional Chinese. This is a written-language/script mismatch, not merely a font appearance difference.

What steps can reproduce the bug?

Observed workflow:

1. Use the Windows desktop app with a Traditional Chinese conversation and a Windows UI culture of zh-TW.
2. Start a task with a Traditional Chinese request, such as the example above.
3. Inspect the generated conversation title in the sidebar, including when returning to the project or conversation.
4. A title may be displayed in Simplified Chinese instead of Traditional Chinese.

This report documents an observed title mismatch and the user's recurring experience. A deterministic minimal reproducer and occurrence rate are not yet available.

The screenshot does not establish whether the title was initially generated in Simplified Chinese or whether a previously Traditional Chinese title was later changed. Opening/resuming a conversation is therefore a reported observation context, not a proven trigger.

What is the expected behavior?

Generated conversation titles should consistently follow the conversation's written language and any explicit language preference, including the distinction between Traditional and Simplified Chinese.

For a Traditional Chinese conversation, an automatically generated Chinese title should remain in Traditional Chinese. Users should not need to repeatedly rename titles to restore the expected written form.

Additional information

Related open reports found during duplicate checking:

• #34893 — foreign characters added to generated thread titles.
• #37924 — an English conversation receives a Simplified Chinese title on iOS.
• #42205 — CLI thread titles do not follow the prompt language.

These are related language-consistency reports, but an exact report for the Windows desktop Traditional-to-Simplified Chinese title mismatch was not found. Please link or merge this report if it belongs to an existing tracking issue.

The cause, responsible component, and regression version are unknown. No claim is being made that location, timezone, or a particular model caused this behavior.

Only the relevant title/request text and minimal environment details are included. The full sidebar screenshot, unrelated conversation titles, project files, and conversation logs are not attached.

Start by reproducing the Windows desktop workflow with a zh-TW UI culture and Traditional Chinese conversation, using the example requests in the report. No responsible component, file, or test is identified, and the report notes that the trigger and occurrence rate are unknown. Done means generated titles consistently preserve Traditional Chinese, including the documented example, without requiring manual renaming.