I don't use Claude for my daily work anymore(due to OAuth restrictions on third party agents), but one theory I saw in another community why Opus 5 is so bad even though benchmark scores were good, is that Anthropic's internal usage pattern is to let Fable to spawn and manage swarms of Opus subagents. This pattern won't penalize that Opus is not well aligned for direct human coworking on posttraining. The worse part is, this makes Fable the user's best default choice for every jobs even if they don't have unlimited credits like Anthropic employees do.