Subprocess return code is incorrectly returned

Type: Bug

Behaviour

It appears that if a python subprocess is called from a debugged process and fails, the return code of the subprocess is not correctly passed on to the caller.

Steps to reproduce:

Example code experiment.py:

import subprocess
import sys

proc = subprocess.run(
    [sys.executable, "-mfred"],
    check=False,
)

print(f"returncode: {proc.returncode}")

If run on the command line, this produces

$ /opt/bb/bin/python3.12 ~/experiment.py 
/opt/bb/bin/python3.12: No module named fred
returncode: 1

If run via a launch config such as

        {
            "name": "Python Debugger: Experiment",
            "type": "debugpy",
            "request": "launch",
            "program": "/home/ralexander72/experiment.py",
            "console": "integratedTerminal"
        }

The output is

$  cd /home/ralexander72/test ; /usr/bin/env /opt/bb/bin/python3.12 /bb/data/ralexander72/vscode-server/extensions/ms-python.debugpy-2025.8.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher 60207 -- /home/ralexander72/experiment.py
No module named fred
returncode: 0

Similarly, running with check=True produces an exception in the non-debugged case but apparent success when run via the debugger.

Adding "subProcess": false to the launch config produces the expected output, so presumably the problem is that the debugger is intercepting and debugging the subprocess (which is normally nice behaviour), but failing to pass on the correct return code after termination of the subprocess.

This is highly unexpected behaviour - could you please investigate?

Extension version: 2025.8.0
VS Code version: Code 1.101.1 (18e3a1ec544e6907be1e944a94c496e302073435, 2025-06-18T13:35:12.605Z)
OS version: Windows_NT x64 10.0.19045
Modes:
Connection to 'ssh-remote+mydev' could not be established
Remote OS version: Linux x64 4.18.0-553.50.1.el8_10.x86_64
Remote OS version: Linux x64 4.18.0-553.50.1.el8_10.x86_64

• Python version (& distribution if applicable, e.g. Anaconda): 3.12.11
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Unknown