Cannot debug Python Azure Functions in Vs Code

[miguelperedozurcher-neste]

Vs Code version
Version: 1.104.2 (Universal) Commit: e3a5acfb517a443235981655413d566533107e92 Date: 2025-09-24T11:21:37.073Z (1 wk ago) Electron: 37.3.1 ElectronBuildId: 12404162 Chromium: 138.0.7204.235 Node.js: 22.18.0 V8: 13.8.258.31-electron.0 OS: Darwin arm64 25.0.0

** Func version **

4.2.2

** Vs Code Extension Version **

Identifier ms-azuretools.vscode-azurefunctions Version 1.19.1 Last Updated 2025-09-29, 09:33:26

What happens ?

I have been debugging Python Azure Functions for more than 2 years. Yesterday (1.Oct.2025) I noticed that debugger does not work anymore.

I press F5, the function starts succesfully, but then the debugger complains with: 'connect ECONNREFUSED 127.0.0.1:9091'

My lauch.json looks like

{
  "version": "2.0.0",
  "configurations": [
    {
      "name": "Attach to Python Functions",
      "type": "debugpy",
      "request": "attach",
      "connect": {
        "host": "localhost",
        "port": 9091
      },
      "preLaunchTask": "func: host start"
    }
  ]
}

[miguelperedozurcher-neste]

And some extra information:

Core Tools Version: 4.2.2+78afd8b84c8e31f0ddac570ba9e8128eefbd3d4a (64-bit) Function Runtime Version: 4.1041.200.25360

[miguelperedozurcher-neste]

An update:

1. instally debugpy in your .venv

And then:

Launch.json

{
  "version": "2.0.0",
  "configurations": [
    {
      "name": "Attach to Python Functions",
      "type": "debugpy",
      "request": "attach",
      "connect": {
        "host": "localhost",
        "port": 9091
      },
      "preLaunchTask": "func: host start"
    }
  ]
}

And tasks.json

{
  "version": "2.0.0",
  "tasks": [
    {
      "type": "func",
      "label": "func: host start",
      "command": "start",
      "problemMatcher": "$func-python-watch",
      "isBackground": true,
      "dependsOn": "pip install (functions)",
      "options": {
        "env": {
          "languageWorkers__python__arguments": "-m debugpy --listen [127.0.0.1:9091](http://127.0.0.1:9091/)"
        }
      }
    },
    {
      "label": "pip install (functions)",
      "type": "shell",
      "osx": {
        "command": "${config:azureFunctions.pythonVenv}/bin/python -m pip install -r requirements.txt"
      },
      "windows": {
        "command": "${config:azureFunctions.pythonVenv}/Scripts/python -m pip install -r requirements.txt"
      },
      "linux": {
        "command": "${config:azureFunctions.pythonVenv}/bin/python -m pip install -r requirements.txt"
      },
      "problemMatcher": []
    }
  ]
}

With that is working again.

[skvark]

Downgrading the VSCode extension to 1.19.0 fixes this: microsoft/vscode-azurefunctions#4715