C# works great for agents but it works due to established patterns, strict compiler & strong typing, compiler flag for "Treat Warnings as Errors", .editorconfig with many rules and enforcement of them. You have to tell it to use async where possible, to do proper error handling and logging, xml comments above complex methods and so on. It works really well once you got it figured out. It also helps to give it separate but focussed tasks, so I have a todo.txt file that it can read to keep track of tasks. Basically you have to be strict with it. I cannot imagine how people trust outputs for python/javascript as there are no strong typing or compilers involved, maybe some linting rules that can save you. Maybe Typescript with strict mode can work but then you have to be a purest about it and watch it like a hawk, which will drain you fast. C# + claude code works really well.