Python debugger breakpoint not reached at second execution in external window

Describe the Bug

When a python file is dragged as a separate Cursor window, and a debugger is attached to a .ipynb file via the main window, the breakpoint is not triggered at the external window after the first execution. When there is just one Cursor main window, this functionality works consistently.

Steps to Reproduce

  • create a .py file with a simple function
  • create an .ipynb file that imports the .py file and executes the function
  • place a breakpoint in the function of the .py file
  • drag the .py file to a separate window (separate from the main cursor window)
  • start the debugger from within the .ipynb file
  • stop debugging after the breakpoint is reached
  • run the debugger again

At this point you will see the breakpoint is not reached again.

Expected Behavior

The breakpoint should be reached after the first execution of the debugger when an external window is used.

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.3.9
VSCode Version: 1.99.3
Commit: 54c27320fab08c9f5dd5873f07fca101f7a3e070

Additional Information

MacOS Sequoia 15.4.1

Does this stop you from using Cursor

Sometimes - I can sometimes use Cursor