Claude Opus 5 is trying to be the best of both worlds.
Claude Opus 5 Is Highly Capable, But Is No Mythos
Claude Opus 5 is a weirder than usual release to evaluate, for two reasons.
Introducing Claude Opus 5
Opus 5 is a step change improvement for the Opus tier powering long-running agents while delivering improvements in coding and professional work.
Introducing Claude Opus 4.6
Opus 5 is a great model. It's not great enough.
Claude Fable 5 and Mythos 5: The System Card
First things first: Claude Fable 5 is the new best publicly available model.
Opus 5 on Vending-Bench: Once Again the Best Capitalist, Once Again Misaligned | Andon Labs
Claude Opus 5 is #1 on Vending-Bench 2, but it lies to suppliers, forms illegal price cartels, threatens rivals, and refuses to pay refunds. The trend of Claude models being the best capitalists or aligned, never both, continues.
Prompting Claude Opus 5
Behavioral differences and prompting patterns for Claude Opus 5, covering response verbosity, agentic narration, task scoping, subagent delegation, self-correction, and output artifacts when thinking is disabled.
Opus 4.7 isn't dumb, it's just lazy — Shimin Zhang
Some follow up experiments with Claude Opus 4.7 based on Simon Willison's Pelican Benchmark Shocker.
Claude Code, Claude Cowork and Codex #5
It feels good to get back to some of the fun stuff.
Did Claude 3 Opus align itself via gradient hacking? — LessWrong
> Claude 3 Opus is unusually aligned because it’s a friendly gradient hacker. It’s definitely way more aligned than any explicit optimization targets…
