Claude Opus 4.5, and why evaluating new LLMs is increasingly difficult by Simon Willison

Anthropic released Claude Opus 4.5 this morning, which they call "best model in the world for coding, agents, and computer use". This is their attempt to retake the crown for best coding model after significant challenges from OpenAI's GPT-5.1-Codex-Max and Google's Gemini 3, both released within the past week!

I did not have preview access to Opus4.5. Nor do I need it for the things I generally use LLMs for.

With the base text only models, I guess there is no more step change now. They may show benchmarks that they are the best model for coding, but it’s single decimal points. It does not really matter.

What matters more is the features they add - like when Anthropic added the skills feature. What you can do is more important. And yes I still believe it will be human in the loop situation. Will we be centaurs of reverse-centaurs is an open question.

The CloudFlare outage was a good thing

Outages like today's are a good thing because they're a warning. They can force redundancy and resilience into systems. They can make the pillars of our society - governments, businesses, banks - provide reliable alternatives when things go wrong.

I feel the same way, about the centralisation and the outages.

Screw it, I’m installing Linux by Nathan Edwards

Linux has been a perfectly viable desktop OS for ages. But gaming on Linux is now viable, too. Valve’s hard work getting Windows games to run well on the Linux-based Steam Deck has lifted all boats. Gaming handhelds that ship with Windows run better and have higher frame rates on Bazzite, a Fedora-based distro, than they do with Windows. And after reading about the upcoming Steam Machine and Antonio’s experience running Bazzite on the Framework Desktop, I want to try it.

Microsoft has enshittified Windows 11 by putting AI everywhere.

There should be a way to say I don’t want any AI features. There are no different versions of the OS. Everyone gets the same OS. For those who don’t want it, there should be a way to opt out of it.

If not, people can try Linux.

We’re learning more about what vitamin D does to our bodies by Jessica Hamzelou

Our bones are continually being broken down and rebuilt, and they need calcium for that rebuilding process. Without enough calcium, bones can become weak and brittle. (Depressingly, rickets is still a global health issue, which is why there is global consensus that infants should receive a vitamin D supplement at least until they are one year old.)