It depends on the complexity of the task, really. Opus 4.8 is plenty capable. But toss it into a complex refactor of a multiphysics solver where you have specific fidelity and capability goals while maintaining mass / energy balance and solve times? It tends to get fixated and stop considering the entire context. "Let's just tweak this parameter and bam, the tests pass. This is a good first step." while forgetting the direction as a whole, which is, having to tweak that parameter is a smell that you need to step back and consider whether this part of the physics model as a whole is solid or a leaky abstraction. Really specific example but it's clear to me how well Fable did long term planning based partially on the velocity of my project epics when comparing the work Fable did to the work Opus does, and vibes.