We’ve been building mobile apps with Claude 4.5 Sonnet. We’re happy to report… it is a very, very good model.

Claude Sonnet 4.5 is now the default model for Augment Code. We’re rolling it out to all customers over the next 24 hours, where it will be available alongside Sonnet 4 (for a limited time) and GPT-5 in the model picker. Here’s how Sonnet 4.5 compares to Sonnet 4:

BREAKING: Anthropic just dropped Claude Sonnet 4.5! We've been testing it for a few days Every 📧 and here's what we found: - It's smarter and faster than Opus: It solved a nasty bug for Kieran Klaassen than Opus 4.1 was continually failing at. And it feels twice as fast. - It's

Spent the last few days exploring the capabilities of Claude Sonnet 4.5 in Figma Make! It's a very impressive model and we are starting a staged rollout to users immediately. Some thoughts in video below — recorded late last night!

I had some early access to Sonnet 4.5. It is a really good model. I saw especially big jumps in doing finance and statistics, which tend to get overlooked in the focus on coding.

Shipping today: Anthropic's Sonnet 4.5 in Notion. Better reasoning, smarter planning, and improved understanding that makes your personal Agent feel truly personalized. Built to get work done.

Right on track. Sonnet 4.5 is a jump in Agentic coding worthy of a major version bump.

Claiming again how insane it is UI-Tars 2 from ByteDance, which was SoTA in CU before that, is at *47.5%*, which is FOURTEEN points below Sonnet 4.5 This model trumps everything in Computer Use and it’s not even close, Anthropic WILL advance and remain SoTA there

is it just me or has claude 4.5 become dumber for everyone in the past few hours?

massive jump in medium and hard cybersecurity CTF challenges with Sonnet 4.5

Sonnet 4.5, meet Droid. After joint testing with Anthropic, we find the strengths of Sonnet 4.5 to be: • Significantly more reliable and accurate file editing • High environmental awareness • Snappier than previous models on quick questions, not overthinking simple asks

Not gonna lie: Claude Chrome extension looks like the CUA we were waiting for! Lets go!

Claude Sonnet 4.5 is here and I got to try it for about 2 days. I would say It's the strongest model for building complex agents. Multi-agents system worked for the first time for me . Let's see what crazy agents people come up with.

Wrote up my initial impressions of the brand new Claude Sonnet 4.5 - I think it may live up to Anthropic's claims of being the "best coding model in the world", for the next few weeks at least! simonwillison.net/2025/Sep/29/cl…

Huge amount of effort went into augmenting 4.5 for cyber use with our partners. We think that 4.5 is the best model for cyber defense now.

Prior to the release of Claude Sonnet 4.5, we conducted a white-box audit of the model, applying interpretability techniques to “read the model’s mind” in order to validate its reliability and alignment. This was the first such audit on a frontier LLM, to our knowledge. (1/15)

AI agents are now capable of doing real, if bounded, work. But that work can be very valuable. For example, the new Claude Sonnet 4.5 was able to replicate published economics research from data files & the paper. We need to figure out what to do with it: oneusefulthing.org/p/real-ai-agen…

Sonnet 4.5 crushing GPT-5 high on ARC-AGI 2

Sonnet 4.5 tops both writing evals! On spiral-bench: much stronger pushback & de-escalation vs sonnet-4. GLM-4.6's score is incremental over GLM-4.5 - but personally I like the newer version's writing much better. Links & writing samples ->

We ran one of our hardest computer-use benchmarks on Anthropic Sonnet 4.5, side-by-side with Sonnet 4 ↴↴ 1/4