Debugging code with `pexpect.spawn` is taking 5s longer

[ciszko]

Environment data

• debugpy version: 1.6.6
• OS and version: Ubuntu 22.04.1 LTS
• Python version (& distribution if applicable, e.g. Anaconda): python 3.10.6
• Using VS Code or Visual Studio: VS Code

Actual behavior

Given the following code:

import pexpect
import time


now = time.time()
pexpect.spawn('echo "foo"')  # "pwd" command works as well, any fast command
print(f"{time.time() - now:.2f}")

Every time I debug it, it takes ~5s to go through the pexpect.spawn line. Without the time module the behavior is the same.

Expected behavior

Just running the code (not debugging) takes only around ~0.10s to do pexpect.spawn line. I assume that without any breakpoints it should take the same amount of time in a debugger as well.

Steps to reproduce:

1. Copy the code provided above
2. Debug the code with a default VS Code configuration, no breakpoints needed

Logs

debugger.vscode_92cdee80-5483-418f-a5e1-311471c4eb54.log
debugpy.adapter-54210.log
debugpy.launcher-54218.log
debugpy.pydevd.54223.log
debugpy.server-54223.log

[AndrePostoluck]

I believe this a Visual Studio subprocess spawn problem described here: #1271

"For every new process created using the above library, there is a delay of 5+ seconds and this delays the debugging process and affect the developer productivity time"

The workaround mentioned there to change 1 line in Visual studio debugpy extension. in a file pydev_monkey.py worked for me, even though I didn't dig deep enough to actually understand the problem and cause:
#1271 (comment)

Since I work on Mac and have newer versions here my file locations where that change just worked for me:
.vscode/extensions/ms-python.debugpy-2025.4.1-darwin-arm64/bundled/libs/debugpy/_vendored/pydevd/_pydev_bundle/pydev_monkey.py

735     def new_execv(path, args):
736         """
737         os.execv(path, args)
738         os.execvp(file, args)
739         """
740         if _get_apply_arg_patching():
741             args = patch_args(args, is_exec=True)
742             send_process_created_message()
743             #send_process_about_to_be_replaced().   # <- commenting this out removes 5 second wait
744
745         return getattr(os, original_name)(path, args)
746
747     return new_execv