Unable to run a Python module in a subprocess when `subProcess: true`

[anvilpete]

The following script executes a Python module in a subprocess.

# main.py
import subprocess
import sys

subprocess.run([sys.executable, "-m", "sub"])

# sub.py
print("Hello, world!")

// launch.json
{
    "version": "0.2.0",
    "configurations": [
    
        {
            "name": "Python Debugger: Current File",
            "type": "debugpy",
            "request": "launch",
            "program": "${file}",
            "console": "integratedTerminal",
            "subProcess": true,
        }
    ]
}

Running this in the debugger with "subProcess": true fails:

bash-3.2$  cd /Users/pete/projects/subprocess_test ; /usr/bin/env /Users/pete/projects/subprocess_test/.venv/bin/python /Users/pete/.vscode/extensions/ms-python.debugpy-2025.18.0-darwin-arm64/bundled/libs/debugpy/adapter/../../debugpy/launcher 56894 -- /Users/pete/projects/subprocess_test/main.py 
No module named sub

Running it with "subProcess": false works as expected:

bash-3.2$  cd /Users/pete/projects/subprocess_test ; /usr/bin/env /Users/pete/projects/subprocess_test/.venv/bin/python /Users/pete/.vscode/extensions/ms-python.debugpy-2025.18.0-darwin-arm64/bundled/libs/debugpy/adapter/../../debugpy/launcher 57618 -- /Users/pete/projects/subprocess_test/main.py 
Hello, world!

OS: Darwin arm64 25.3.0
VSCode: 1.109.5 (Universal)
Python Debugger: 2025.18.0
Python: 3.14.2 (in a virtualenv)

[rchiodo]

Reopening until we actually ship the fix. This seems to have been caused by changes in 3.14.

[anvilpete]

Amazing, many thanks Rich!