Comment by tcgv

Upvote.

That's my experience too. Agent coding works really well for existing codebases that are well-structured and organized. If your codebase is mostly spaghetti—without clear boundaries and no clear architecture in place—then agents won't be of much help. They'll also suffer working in those codebases and produce mediocre results.

Regarding building apps and systems from scratch with agents, I also find it more challenging. You can make it work, but you'll have to provide much more "spec" to the agent to get a good result (and "good" here is subjective). Agents excel at tasks with a narrower scope and clear objectives.

The best use case for coding agents is tasks that you'd be comfortable coding yourself, where you can write clear instructions about what you expect, and you can review the result (and even make minor adjustments if necessary before shipping it). This is where I see clear efficiency gains.