I think repl driven development with access to native code could be a magic formula for agent engineering. No restarting, no re-compiling. Plus with persistent, immutable data structures you can iterate with many threads in parallel while maintaining sanity.
The first thing that comes to mind with no restarts or recompiling is the mangled variables you get in Jupiter if you're mucking around trying to get a prototype going and forget which cells have been run. I can definitely see agents having a problem with that. I would just try to make compilation fast if possible