Claude Opus 5.5

Pros: After using it, the biggest thing I notice is how much better it is at sustained work. It stays organized across long coding sessions, multi-file changes, research tasks, and agent workflows without needing nearly as much babysitting. The coding performance is excellent. Anthropic reports 54.6% on FrontierCode 1.1 at default effort, ahead of GPT-6 Astra’s reported 53.3%, and I can see why. It is especially good at understanding a large task, making sensible changes, and avoiding unnecessary edits. I also really like the efficiency. At $4 per million input tokens and $20 per million output tokens, plus much cheaper cache reads, Opus 5.5 is easier to use heavily than Opus 5. Anthropic says typical workloads come out around 40% cheaper overall. Another improvement is the writing. It is noticeably less verbose and easier to follow, which matters a lot during long sessions when I need to quickly understand what the model changed and why.

Cons: The main downside is that it is still a premium model, so I would not waste it on every trivial task. And like any coding agent, I still review diffs, run tests, and keep permissions tight.

Overall: Overall, Claude Opus 5.5 is one of the best models I have used for serious coding and long-running agent work. It feels faster, more efficient, and more dependable than Opus 5 without giving up the depth I want from a top-tier model.