An 'incorrect' error occurred in the opus-4.6 model

[Xukai_Liu]

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

When performing an agent task using the opus 4.6 model, the output content entered the ‘error zone’

Steps to Reproduce

As soon as I switched to the opus4.6 model and sent the first message, this problem occurred.

Expected Behavior

Normally reply to the area for responding to messages

Screenshots / Screen Recordings

Operating System

Windows 10/11

Version Information

Version: 2.5.22 (system setup)
VSCode Version: 1.105.1
Commit: 0eda506a36f70f8dc866c1ea642fcaf620090080
Date: 2026-02-23T00:15:21.265Z
Build Type: Stable
Release Track: Early Access
Electron: 39.4.0
Chromium: 142.0.7444.265
Node.js: 22.22.0
V8: 14.2.231.22-electron.0
OS: Windows_NT x64 10.0.26200

For AI issues: which model did you use?

opus-4.6

For AI issues: add Request ID with privacy disabled

Request ID: 15d0cc18-b4f3-48af-a06a-55fdc24393d6
very long error report！！I can’t report all request!

Additional Information

very long error report

Does this stop you from using Cursor

Yes - Cursor is unusable

[deanrie]

Hey, thanks for the report.

I can see the error. It’s a 400 Bad Request caused by an invalid tool_choice parameter being sent to the model. This looks like a bug on our side, you did everything right.

To unblock yourself right now, try switching to a different model like Claude Sonnet or Auto.

I’ve passed this on to the team. No ETA yet, but your report helps us prioritize it.

Let me know if the issue still happens with other models too.

[Xukai_Liu]

the same came happened on sonnet 4.6 I am still crying!