Interactive Python Window REPL Error: "notebook controller with id 'pythonREPL' ALREADY exist"

Bug Reports
1

Describe the Bug

Issue Description:
When using the Interactive Python Window in Cursor, I can successfully create and run cells using the “Run Cell” functionality. However, when attempting to execute code directly in the REPL input bar at the bottom of the interactive window, I receive the error:
“notebook controller with id ‘pythonREPL’ ALREADY exist”

Would appreciate any guidance on resolving this issue or if there are any known workarounds. Thanks!

Steps to Reproduce

Steps to Reproduce:

  1. Open a Python file with cell markers (#%%)
  2. Successfully run a cell using the “Run Cell” button
  3. Try to execute code in the REPL input bar at the bottom of the interactive window
  4. Error occurs: “notebook controller with id ‘pythonREPL’ ALREADY exist”

NB: f you press the arrow to the left of the bar it works, however pressing “enter” on the keyboard results in the error
In the recording, I first press enter three times producing the error and then click on the arrow.

Expected Behavior

Expected Behavior:

  • Should be able to execute code both in cells and in the REPL input bar
  • Similar functionality works correctly in VS Code

Screenshots / Screen Recordings

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.1.2
VSCode Version: 1.96.2
Commit: 87ea1604be1f602f173c5fb67582e647fcef6c40
Date: 2025-06-13T00:30:10.108Z
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

Environment Details:

  • OS: macOS 15.5 (Build 24F74)
  • Python Version: 3.12.11
  • Jupyter/IPython Components:
    • ipykernel: 6.29.5
    • jupyter_client: 8.6.3
    • jupyter_core: 5.8.1
    • jupyter_server: 2.16.0
    • jupyterlab: 4.4.3

Additional Information

Additional Context:

  • This issue is specific to Cursor
  • The same functionality works without issues in VS Code
  • The error suggests a potential conflict in the notebook controller initialization

Impact:
This issue prevents the use of the REPL input bar in the Interactive Python Window, limiting the interactive development experience in Cursor.

Does this stop you from using Cursor

Yes - Cursor is unusable