My Claude 4 Sonnet Thinking Does Not Think

Bug Reports
1

Describe the Bug

I am using Sonnet 4 thinking, but it just direcly answer question quickly without thinking,

Steps to Reproduce

choose claude sonnet 4 thinking then use as agent.

Previously i am switch between Max and Non Max in the same Agent conversation,

Expected Behavior

AI think before making response

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.0.0
VSCode Version: 1.96.2
Commit: 53b99ce608cba35127ae3a050c1738a959750860
Date: 2025-06-04T19:21:22.523Z
Electron: 34.5.1
Chromium: 132.0.6834.210
Node.js: 20.19.0
V8: 13.2.152.41-electron.0
OS: Darwin arm64 24.5.0

Does this stop you from using Cursor

Sometimes - I can sometimes use Cursor

2

Hey, just to confirm, have you got the Claude 4 Sonnet model selected with thinking enabled?

Screenshot 2025-06-16 at 15.22.33

We did change the format of the model picker in one of the recent updates, which means the thinking and non-thinking versions of a model show up as separate options instead of having a thinking toggle at the top.

3

Yes.i choose correct sonnet thinking. The response also very short and never call any tools.

Here is one of the request ID: b1f582d5-c7b4-487f-82f2-4865721b1e05

4

Just made my own post but +1 to this. Started 4 days ago but has been happening constantly since then when trying to use Claude-4-Sonnet Thinking

5

Hey, see my response here: