> But generally people let their agent make whatever change it makes and then wonder why trains are flying off the tracks.

IMO, this is the biggest issue. Well, along with just straight up ignoring what you tell it and doing whatever it thinks should be done.

But, to answer the actual thread question: Make it work (all the tests pass) then make it right is the way I'm getting quality work out of the robots. As long as you watch them to make sure they don't either change the tests to pass on buggy code or change the code to pass on buggy tests (yes, Claude is quite proficient and eager to do both) then the code gets better and better as new stuff is added and the 'flow of computation' is worked out.

Oh, and have an actual plan to follow so they don't get distracted at the first issue and say they're finished because they fixed some random unrelated bug. I've also found it helpful to have them draft up such a plan while they're knee deep in that section of the code for related work so they don't have to figure it all out again from scratch and try to add a few extra levels of abstraction just because.