Earlier quoted context omitted.
I am really struggling with this. I tried Cline with both OpenAI and Claude to very weird results. Often burning through credits to get no where or just running out of context. I just got Cursor for a try so can't say anything on that yet.
It's a skill that takes some persistence and trial and error. Happy to chat with you about it if you want to send me an email.
Language: Syntax errors rise, and a common form is the syntax of a more common language bleeding through.
Domain: Less so than what humans deem complex, quality is more strongly controlled by how much code and documentation there is for a domain. Interesting is that if in a less common subdomain, it will often revert to a more common approach (for example working on shaders for a game that takes place in a cylinder geometry requires a lot more hand-holding than on a plane). It's usually not that they can't do it, but that they require much more involved prompting to get the context appropriately set up and then managing drifting to default, more common patterns. Related is decisions with long term consequences. LLMs are pretty weak at this. In humans this one comes with experience, so it's rare and an instance of low coverage.
Dates: Related is reverting to obsolete API patterns.
Complexity: While not as dominant as domain coverage, complexity does play a role. With likelihood of error rising with complexity.
This means if you're at the intersection of multiple of these (such as a low coverage problem in a functional language), agent mode will likely be too much of a waste for you. But interactive mode can still be highly productive.