I haven't been impressed with Opus 5 over the past ~30 hours either.
It's made countless careless mistakes folding in plan amendments after they get reviewed by Sol, and has produced sloppy mockups (e.g. buttons overflowing past cards) despite all the supposed verification claims.
I finally made progress today on a deeply intractable problem that Sonnet was just incapable of solving despite hours of experimentation and multiple attempts. I swapped over to Opus in a new handoff session with the expectation of using at least one 5 hour session. It wasn't quick and took several hours but eventually Opus dialed in on several cascading base failures resulting from how the base vision model was being converted to coreml. It eventually was able to provide a combination of conversion and Swift changes that semi fixed the issue but still didn't solve the core conversion issues.
Then since Anthropic was so kind to provide $100 for Fable credits, I did another handoff to let Fable attack the root issues again. Several more hours and I'm back to seeing the same issues again and Fable is wandering around trying different things. I'm down about $40 of free money and still don't have a solution.
This is where having the human engineer in the loop benefits from a deep understanding of the problem domain. In this case, I don't yet.
I know the high level architecture I'm building, but the deep specifics of how vision models work and how conversion across platforms should be done isn't something I know yet.
So I'm left learning as I go and relying on constant feedback with the models to provide what guidance I can while learning exactly what is being done.
Someone who already knows these architectures would likely be able to get to the solution much faster.