Preserve language in generated thread titles

[alievk]

What Changed

Updated the thread title generation prompt to preserve the user's language.

Added prompt coverage to ensure the instruction stays present.

Why

Thread titles are generated from the user's first message, but the prompt did not specify which language to use. As a result, titles for non-English requests could be generated inconsistently in either the user's language or English.

Keeping the instruction in the prompt is the smallest fix because title generation already happens there, and this avoids adding language detection or UI-side special cases.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes

Before

After

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Note

Low Risk
Low risk: only adjusts the LLM prompt text for thread title generation and adds a unit test to prevent regressions; no auth, data handling, or control-flow changes.

Overview
Thread title generation now explicitly instructs the model to use the user’s language and not translate by adding a new rule to buildThreadTitlePrompt.

Adds a focused test in Prompts.test.ts to assert the language-preservation instruction remains present in the generated prompt.

^{Reviewed by Cursor Bugbot for commit 8eef0c4. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Preserve user language in generated thread titles

Adds the rule "Use the user's language; do not translate." to the buildThreadTitlePrompt function in Prompts.ts, preventing the model from translating thread titles into another language.

^{Macroscope summarized 8eef0c4.}

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[macroscopeapp]

Approvability

Verdict: Approved

This PR adds a single prompt instruction to preserve the user's language in generated thread titles, along with a corresponding test. The change is purely additive text guidance with no logic or schema changes.

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