Old Mozilla / Firefox with XUL / XPCOM[1] was probably about as close as you get. If you were willing to use the low-level interfaces, you could change just about anything as far as I can tell. But that led to security issues and issues with maintaining comparability when there was a need to change those low-level interfaces. So Firefox largely moved away from XPCOM and blocked extensions from calling XPCOM interfaces.

That said, AFAIK Pale Moon still allows use of XPCOM. And I think Seamonkey may be the closest remaining browser to the Mozilla of old. I believe you can still use all of the XUL/XPCOM stuff there, but don't quote me on that.

[1]: https://en.wikipedia.org/wiki/XPCOM

[2]: https://en.wikipedia.org/wiki/SeaMonkey

Interesting stuff - none of these seem to have that Smalltalk-like visual IDE bolted right into them.

Given how big and important a platform the modern web is - I really am starting to think - something like this should exist - where I have a neat little IDE bundled right within the browser using which I can evolve the browser...

Not really 'visual', but https://nyxt-browser.com maybe?

Otherwise the less extreme https://luakit.github.io / https://github.com/luakit/luakit comes to mind. It's not dead yet.

Why not go the other way around? For example, with Pharo, there is a WebBrowser project which could be further refined to do more of what you are proposing.

Nyxt. Also, google is your friend.

I've seen this already - but Lisp seems a bit limiting. I'd have loved to use Py/Go or JS in the least - something more upto date.

You ever have a user who pines for this or that feature, and when you tell him it's already implemented, he'll change the goalposts in some trivial way? It's not solutions we love, it's the warm fuzzy narcissism of complaining.

You seem challenged with having a basic discussion without resorting to baseless personal attacks. HN discussions have nosedived in quality over the time. Feel like I'm on reddit.

On the topic - here were my original points (with some extensions):

1. I want a smalltalk-like environment but with modern languages (webassembly makes this technically possible)

2. Alan Kay himself agrees smalltalk is no longer relevant in a concrete manner anymore - it's too old and outdated. The library support is absymal, and LLMs etc won't be as helpful as modern langs, since the training data available is less in quantity and quality. And I am in line with Dr. Kay's view - Smalltalk is indeed too old. I feel the same way about using Lisp for my particular goals.

3. I am not complaining in any way - just stating my requirements in explicit terms. Also I dont consider myself a "user". I am a system builder. I am fully capable of doing things myself if there's no alternative available.