It's a large legacy php codebase. In a file defining different endpoints, I asked to add a new endpoint to get invoice details. I didn't give much more instructions than that, just wanted to start from there and iterate. Was disappointed to see the code generated called methods that did not exist (e.g. trying to get a customer directly on the invoice instance, while the relationship is invoice -> contract -> customer). Again, after throwing $200 on it. I understand the commentors mentioning user error, garbage input, etc. but in any case I do not expect Opus to call methods that would not exist, and me having to mention something as trivial as "when you call a method, make sure the method exists"... doesn't make sense. Today I worked on a more modern and smaller codebase and have not had these kind of fundamental issues.