> Code always was, it's supposed to be malleable

Yes, well-designed code is malleable to an extent when coding by hand, but even then it's an order of magnitude more rigid than when working with agents (and real-world code often ossifies, as you pointed out). Malleability comes not only from the possibility of change but also from the speed.

> It's the data you generate with that code that's your asset. You can always rewrite the code.

I like that perspective, but "you can always rewrite the code" almost never happens in real life for complex projects, and when it does, it's a huge undertaking that takes many months or even years. Malleable code makes that much more feasible, I'd argue.