Gemini 3 Pro deleting huge chunks of code

[Taitranz (Tai Tran)]

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

I noticed that Gemini 3 Pro has a high tendency to wipe out large chunks of code and then sometimes self correcting.

Steps to Reproduce

No clue, it often happens with CSS

Screenshots / Screen Recordings

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.1.25 (user setup)
VSCode Version: 1.105.1
Commit: 7584ea888f7eb7bf76c9873a8f71b28f034a9820
Date: 2025-11-23T04:45:23.529Z
Electron: 37.7.0
Chromium: 138.0.7204.251
Node.js: 22.20.0
V8: 13.8.258.32-electron.0
OS: Windows_NT x64 10.0.26200

For AI issues: which model did you use?

Gemini 3 Pro

For AI issues: add Request ID with privacy disabled

Request ID: 00c3f902-290b-4e77-b0af-c36700f0e99c

Does this stop you from using Cursor

No - Cursor works, but with this issue

[Taitranz (Tai Tran)]

[Taitranz (Tai Tran)]

[Taitranz (Tai Tran)]

[deanrie]

Hey, thanks for the report. I can see that the Agent is deleting hundreds of lines of CSS even after you explicitly asked it not to.

For now, I’d strongly recommend:

• Switching to Claude Sonnet 4.5 or GPT-5.1 for this task
• Avoiding Gemini 3 Pro in Agent mode until this issue is resolved

The team is already aware of various Gemini 3 Pro integration issues since its launch on November 18, but this code deletion behavior needs special attention. I’ll pass this on to the team.

[adsantos]

I had the same issue, it kept deleting large chunks of codes and re-writing it. I thought it was a cursor issue, until I experienced it removing a large section of content on the Google Gemini app

[Taitranz (Tai Tran)]

Posting this here because I feel like the reasoning token might be useful for debugging this issue
7e014fc6-306f-4d8f-83c0-148a20478304