Tool call failures by GPT 5.1 High in Plan Mode

[Aaron_Suydam]

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

I asked for a plan to implement some requirements, like normal, and it thought/explored, and created a plan. So far, so good. Then I asked it to make some changes to the plan, and it froze on the tool call. This happens repeatably.

Steps to Reproduce

Simply create a plan and then ask it to modify it using Plan Mode.

Expected Behavior

It should modify the existing plan no problem.

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.1.50 (Universal)
VSCode Version: 1.105.1
Commit: 56f0a83df8e9eb48585fcc4858a9440db4cc7770
Date: 2025-12-06T23:39:52.834Z
Electron: 37.7.0
Chromium: 138.0.7204.251
Node.js: 22.20.0
V8: 13.8.258.32-electron.0
OS: Darwin arm64 25.1.0

For AI issues: which model did you use?

GPT 5.1 High Fast

For AI issues: add Request ID with privacy disabled

c6338539-a11f-44cb-b9c1-bec630c7f32d

Does this stop you from using Cursor

Sometimes - I can sometimes use Cursor

[deanrie]

Hey, thanks for the report. This matches a known bug in the create_plan tool during plan updates - it can hang or time out. Temporary workaround: copy the markdown of the current plan into a new agent window and continue there. See the accepted answer: Cursor planning mode crash

Could you please share:

• Screenshots of errors from Help > Toggle Developer Tools > Console at the time of the hang
• The result of launching with extensions disabled: cursor --disable-extensions
• Whether it reproduces on a different model

I’ll pass this to the team. Let me know if the workaround helps.