Agent responds in Japanese when I ask questions in Chinese

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1

Where does the bug appear (feature/product)?

Cursor IDE

Description

When using the Cursor Agent (Claude Sonnet 4.6) in the sidebar chat, I asked questions in Chinese, but the Agent suddenly started responding in Japanese instead of Chinese. I did not change any language settings or include any Japanese text in my prompt.

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image1306×1036 111 KB

Expected Behavior

The Agent should respond in the same language as my input (Chinese).

Environment

  • Version: 3.3.27
    VSCode Version: 1.105.1
    Commit: 80b138a7a0a948e1a798e9ed7867d76a1ba9a310
    Date: 2026-05-08T02:26:22.498Z
    Layout: editor
    Build Type: Stable
    Release Track: Default
    Electron: 39.8.1
    Chromium: 142.0.7444.265
    Node.js: 22.22.1
    V8: 14.2.231.22-electron.0
    OS: Darwin arm64 24.6.0

  • AI Request ID: 20a93142-d6c6-4f2f-a91b-0609802a3db1

Additional Context

  • No Japanese content exists in my project files or conversation history.

  • This issue occurred mid-conversation — the Agent initially replied in Chinese correctly, then suddenly switched to Japanese.

  • I have not set any custom rules specifying a response language.

Does this stop you from using Cursor?

  • No - Cursor works, but with this issue
2

Hi there!

We detected that this may be a bug report, so we’ve moved your post to the Bug Reports category.

To help us investigate and fix this faster, could you edit your original post to include the details from the template below?

Bug Report Template - Click to expand

Where does the bug appear (feature/product)?

  • Cursor IDE
  • Cursor CLI
  • Background Agent (GitHub, Slack, Web, Linear)
  • BugBot
  • Somewhere else…

Describe the Bug
A clear and concise description of what the bug is.

Steps to Reproduce
How can you reproduce this bug? We have a much better chance at fixing issues if we can reproduce them!

  1. …
  2. …
  3. …

Expected Behavior
What is meant to happen here that isn’t working correctly?

Screenshots / Screen Recordings
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Operating System

  • Windows 10/11
  • MacOS
  • Linux

Version Information

  • For Cursor IDE: Menu → About Cursor → Copy
  • For Cursor CLI: Run agent about in your terminal
IDE:
Version: 2.xx.x
VSCode Version: 1.105.1
Commit: ......

CLI:
CLI Version 2026.01.17-d239e66

For AI issues: which model did you use?
Model name (e.g., Sonnet 4, Tab…)

For AI issues: add Request ID with privacy disabled
Request ID: f9a7046a-279b-47e5-ab48-6e8dc12daba1
For Background Agent issues, also post the ID: bc-…

Additional Information
Add any other context about the problem here.

Does this stop you from using Cursor?

  • Yes - Cursor is unusable
  • Sometimes - I can sometimes use Cursor
  • No - Cursor works, but with this issue

The more details you provide, the easier it is for us to reproduce and fix the issue. Thanks!

7

This is a known limitation with large language models working with CJK languages. Chinese and Japanese share many characters (kanji/hanzi), and models can occasionally drift into a related language mid-conversation, especially as the conversation grows longer.

A couple of things that should help:

  1. Add a User Rule to reinforce the language. Go to Cursor Settings > Rules > User Rules and add: Always respond in Simplified Chinese (简体中文). Never switch to Japanese or any other language unless I explicitly ask.

  2. Start a new chat when the drift happens. Shorter contexts are more consistent with language.

This behavior stems from the model itself, so it may still occur occasionally, but a stricter rule should significantly reduce its frequency.