IIRC no browser currently force-selects a default browser via private API, except for new Edge if you had old Edge as default (since old Edge is uninstalled at the same time).

I.e. If Firefox switched to Chromium I would expect the exact same behaviour "New Firefox" and "Old Firefox" is not a distinction.

You can make a consistent explanation for either side, as you have just done.

If it's the same browser, then transferring the default status is correct.

If it's a new browser, then asking what should be default is correct.

Chredge is doing both, depending on which one advantages them more.

Saying this as someone who mainly uses firefox and occasionally brave.

As you say, they have responsibility to their users;

If the URL handler was old Edge, and they didn't change it while removing old Edge, the user would have broken internet access and not understand why. That's no good.

If the URL handler was updated to quietly move to new Edge, they just swapped out a major piece of software for one which looks and behaves differently, with a different icon, without any introduction or warning or confirmation, which is an awful experience for users. Microsoft get accused of special-casing themselves and their browser, and it breaks the work Microsoft has done for years to stop programs changing file/protocol handlers without confirming it with the user. [see Raymond Chen writing about it here https://devblogs.microsoft.com/oldnewthing/20181016-00/?p=99... ]

If they decide a browser is not part of Windows and you have to install new Edge from the app store yourself, tens of millions of computers are now stuck on the last version of old Edge basically forever - because there's no Windows 11 on the way to replace it - and it becomes the new IE6 millstone for web developers. If they also remove old Edge at the same time, millions of people lost their browser and don't know why - and the only default one remaining is IE 11.

There is a new thing, the hypothetical user who had settled into Edge does need to know, however it got installed.

Well, afaik from 98 to XP it was just ‘put your shortcuts in the Quicklaunch folder’ (dunno about Vista and later).

I'm tempted to run Win10 just to see what happened to it in the past decade.

To be clear, an API for pinning apps now exists[0], but it asks confirmation to the user

[0]: https://docs.microsoft.com/en-us/windows/uwp/design/shell/pi...