Python 3.14 webbrowser regression when launching vscode:// URI on macOS

[skissane-medallia]

Bug report

Bug description:

In Python 3.13.13 on macOS 26.3.1, I run __import__("webbrowser").open("vscode://"): it opens Microsoft VS Code
Same machine, in Python 3.14.2, same code: opens Chrome instead

I observe the same behaviour with Python 3.15.0a8

One line test case (using uv):

uv run --no-project --python=3.14 python3 -c '__import__("webbrowser").open("vscode://")'

In my actual use case, the URI is more complex, something like vscode://vscode-remote/ssh-remote+MYDEVBOX.example.com/workspaces/MYPROJECT.code-workspace – but vscode:// is enough to reproduce it

CPython versions tested on:

3.14

Operating systems tested on:

macOS

Linked PRs

• gh-149454: Restore OS handler dispatch for custom URI schemes on macOS #155859

[skissane-medallia]

From looking at the code, I believe this was introduced by #130535 – that PR appears to assume you only ever want to open custom URI schemes in an actual web browser. But in reality, for an application-specific URI scheme such as vscode:// or slack://, the browser probably doesn't know how to handle it, the OS-registered application does.

[edvilme]

That is most likely an issue with your browser not knowing how to handle the application-specific URI
When it opens Chrome, what does it show? Also, what happens if you attempt to open the URI from the terminal?

open vscode://vscode-remote/ssh-remote+MYDEVBOX.example.com/workspaces/MYPROJECT.code-workspace

[skissane-medallia]

@edvilme

open vscode:// opens VSCode

uv run --no-project --python=3.13.13 python3 -m webbrowser vscode:// opens VSCode

uv run --no-project --python=3.14.2 python3 -m webbrowser vscode://:

• If Google Chrome is not running, it starts Chrome (I am using 148.0.7778.97) – but unusually, it starts it with no windows open
• If Chrome is already running, it makes it the foreground app, showing me whatever window/tab I was last using

Note, Chrome does understand vscode:// if I type it into the URL bar, or link to it from a web page – it looks up the application in the OS settings, and displays a confirmation box "Open Visual Studio Code? A website wants to open this application"

But I think, for security reasons, it silently ignores URIs handled by other apps if passed to it directly – because it isn't expecting anyone to do that.

[skissane-medallia]

The behaviour depends on which web browser is configured as default:

• Google Chrome: opens/foregrounds Chrome, but URL is silently ignored
• Safari: shows a confirmation box asking if you want to open the app "Visual Studio Code" (this is a behaviour change from <=3.13 where Safari did not open and no confirmation box was displayed – it is confusing to display a confirmation box asking if a website wants to open an app when a Python script on your machine is trying to open it)
• Firefox: behaves like Safari does, mostly

If I understand the logic behind #130535, people didn't like the fact that file:// opened a text editor instead of browser on some systems. Fair enough, but I don't think changing the behaviour of custom URI schemes to route through the browser was necessary to fix a problem with file:// in particular.

[skissane-medallia]

In case it is of assistance to anyone, below is a monkeypatch-workaround for this bug (which Claude Code wrote for me):

"""Workaround for https://github.com/python/cpython/issues/149454.

In Python 3.14 on macOS, webbrowser.open() incorrectly routes non-browser URI
schemes (e.g. vscode://, slack://) to the default web browser instead of the
macOS `open` command. Calling apply() monkeypatches webbrowser.open to restore
the pre-3.14 behaviour for those schemes.
"""

import subprocess
import sys
import urllib.parse
import webbrowser


_BROWSER_SCHEMES = frozenset({"http", "https", "file"})
_original_open = None


def _patched_open(url, new=0, autoraise=True):
    scheme = urllib.parse.urlparse(url).scheme
    if scheme in _BROWSER_SCHEMES:
        return _original_open(url, new=new, autoraise=autoraise)
    subprocess.run(["open", url], check=False)
    return True


def apply() -> None:
    """Apply the webbrowser.open monkeypatch if running on the affected platform."""
    global _original_open
    if sys.platform == "darwin" and sys.version_info[:2] == (3, 14):
        _original_open = webbrowser.open
        webbrowser.open = _patched_open

[encukou]

webbrowser did not open a browser before? Sorry, but that sounds like a fixed bug.