Early lesson I learned from AI engineering was - there is no substitute to giving a groomed epic to an agent. Instead of simply saying 'implement themes in my product' you need to be specific, in fact more specific than usual. You need to say exactly what is in scope and what's not, even down to a buttons, events and layouts. You can groom the epic with the help of AI, but final review must be done by someone who can…
At which point you might as well write the code yourself and get a deterministic result faster, better and cheaper.