I spent some time exploring Glamorous Toolkit [1] for agent-assisted custom UI development, in an emacs fashion, where you'd modify the interface you're working with on the fly. It was a pretty good experience and the built-in data exploration was top notch.

Ironically after watching glamorous toolkit videos on youtube, I was recommended a talk by Geoffrey Litt about dynamic documents [2] and at the end of his talk I learned about bb [3], which has much better agent integration compared to GT. Like @thelazydogsback said, with agents, the programming language matters less.

[1] https://gtoolkit.com/

[2] https://www.youtube.com/watch?v=MccJdr61xnc

[3] https://getbb.app/

SmallJS ( https://small-js.org ) is a file based Smalltalk with full agent support. Here's a vid of Claude converting a Counter app into a Tic-tac-toe game in a single shot: https://www.youtube.com/watch?v=4_ir6h2MIRg PS The context loading step is not even necessary anymore. The reason why this works so well, is that Claude knows its way around VSCode well. And all SmallJS projects (apps) have full unit tests and GUI tests that run in a couple of seconds. Claude also reads these tests and can make new ones, maintaining coverage. In tradtional live Smalltalks like Pharo, modifying stuff is easy, but running full tests not so much..

It got me interested so i ashed ChatGpt about the options andit found this repo: https://pharo-llm.github.io/pharo-mcp

Sounds pretty cool. Never heard about Pharo before, but i will try it in spare time.

>Intuitively it seems like a match made in heaven, since the agent can directly manipulate the running program

This should be a BIG benefit for agent-driven development, but sadly it seems that few people is taking advantage of it.

It works well, I mostly use Pi with MCP.