Thread titles should follow prompt language, not inferred location

What version of Codex CLI is running?

codex-cli 0.153.0-alpha.4

What subscription do you have?

Plus

Which model were you using?

gpt-5.6-sol

What platform is your computer?

Linux

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

No response

Codex doctor report

What issue are you seeing?

Summary

Since PR #40492, new Codex CLI thread titles are sometimes generated in Portuguese (Brazil), even when I use Codex exclusively in English and submit English prompts.

Expected behavior

Automatic thread titles should use the language of the user’s prompt/conversation, or follow an explicit user-configured preference if one is added.

For English prompts, titles should be generated in English.

Actual behavior

After the thread-title changes in #40492 (and related /rename suggestion work in #40495), thread titles are generated correctly in content but appear in Portuguese.

For example, an English prompt may receive a Portuguese title.

Why this is a problem

Physical location is not a reliable proxy for a user’s preferred language. I live in Brazil, but I use Codex in English. Backend-derived location, account context, or other inferred regional signals should not override the language evident in the prompt.

The current title-generation instruction says “Write in the user’s language,” but the resulting behavior appears to interpret that as Portuguese rather than the language used in the request.

Suggested fix

Make title generation deterministic by using the language of the latest substantive user message/conversation. Alternatively, provide a user-facing configuration for preferred thread-title language.

In either case, inferred geographic location should not cause English prompts to receive Portuguese thread titles.

Regression range

This behavior began after #40492 and #40495 were merged on August 24, 2026.

What steps can reproduce the bug?

Create a new session/thread and prompt the mode in English. The thread name is generated in a different language, likely inferred from backend-derived location, account context, or other regional signals.

What is the expected behavior?

No response

Additional information

No response

Start by reviewing the thread-title changes in PRs #40492 and #40495, then reproduce the issue with an English prompt in Codex CLI. Trace how the title language is selected; done means English prompts produce English titles without relying on inferred geographic location.