Claude Sonnet 4.5 (anthropic.com)

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but: https://imgur.com/a/462T4Fu

So Opus isn't recommended anymore? Bit confusing

I've really got to refactor my side project which I tailored to just use OpenAI API calls. I think the Anthropic APIs are a bit different so I just never put in the energy to support the changes. I think I remember reading that there are tools to simpify this kind of work, to support multiple LLM APIs? I'm sure I could do it manually but how do you all support multiple API providers that have some differences in the API design?

Looking at the chart here, it seems like Sonnet 4 was already better than GPT-5-codex in the SWE verified benchmark.

However, my subjective personal experience was GPT-5-codex was far better at complex problems than Claude Code.

Interesting that this is better than Opus 4.1. I want to see how this holds up under real world use, but if that's the case its very impressive.

I wonder how long it will be before we get Opus 4.5

Lots of feature dev here – anyone have color on the behavior of the model yet? Mouthfeel, as it were.

Seeing the progress of the Claude models is really cool!

Charting Claude's progress with Sonnet 4.5: https://youtu.be/cu1iRoc1wBo

Price is playing a big role in my AI usage for coding. I am using Grok Code Fast as it's super cheap. Next to it GPT-5 Codex. If you are paying for model use out of pocket Claude prices are super expensive. With better tooling setup those less smart (and often faster) models can give you better results.

I am going to give this another shot but it will cost me $50 just to try it on a real project :(

As the rate of model improvement appears to slow, the first reactions seem to be getting worse and worse, as it takes more time to assess the model's quality and understand the nuances & subtler improvements

I'm really interested in the progress on computer use. These are the benchmarks to watch if you want to forecast economic disruption, IMO. Mastery of computer use takes us out of the paradigm of task-specific integrations with AI to a more generic interface that's way more scalable.

That's a pretty pelican on a bicycle!

https://jsbin.com/hiruvubona/edit?html,output

https://claude.ai/share/618abbbf-6a41-45c0-bdc0-28794baa1b6c

Ah, the company where the models are unusable even with Pro subscription (start to hit the limit after 20 minutes of talking), and free models are not usable at all (currently can't even send a single message to Sonnet 4.5)...

Their benchmark chart doesn't match what's published on https://www.swebench.com/.

I understand that they may have not published the results for sonnet 4.5 yet, but I would expect the other models to match...

Same price and a 4.5 bp jump from 72.7 to 77.2 SWEBench

Pretty solid progress for roughly 4 months.

Oh wow, a lot of focus on code from the big labs recently. In hindsight it makes sense that the domain the people building it know best is the one getting the most attention, and it's also the one the models have seen the most undeniable usefulness in so far. Though personally, the unpredictability of the future where all of this goes is a bit unsettling at the same time...

This looks exciting. I hope they add this to Windsurf soon.

So… seems like we’re back to Sonnet being better than Opus? At least based on their benchmarks.

Curious to see that in practice, but great if true!

I happened to be in the middle of a task in a production codebase that the various models struggled on so I can give a quick vibe benchmark:

opus 4.1: made weird choices, eventually got to a meh solution i just rolled back.

codex: took a disgusting amount of time but the result was vastly superior to opus. night and day superiority. output was still not what i wanted.

sonnet 4.5: not clearly better than opus. categorically worse decision-making than codex. very fast.

Codex was night and day the best. Codex scares me, Claude feels like a useful tool.

I really hope benchmarking improves soon to monitor the model in the weeks following the announcement. It really seems like these companies introduce a new "buffed" model and then slowly nerf the intelligence through optimizations.

If we saw task performance week 1 vs week 8 on benchmarks, this would at least give us more insight into the loop here. In an environment lacking true progress a company could surely "show" it with this strategy.

Interesting quirk on first use: "`temperature` and `top_p` cannot both be specified for this model. Please use only one."

They really had to release an updated model, I can only imagine how many people cancelled their plans and switched over to Codex over the past month.

I'm glad they at least gave me the full $100 refund.

its time to start benchmarking benchmarks. im pretty sure they are bmw levels doping the game here

`claude model claude-sonnet-4-5-20250929` for cli users

I’m always fascinated by the fine-tuning of LLM personalities. Might we finally get less of the reflexive “You’re absolutely right” with this one?

Maybe we’re entering the Emo Claude era.

Per the system card: In 250k real conversations, Claude Sonnet 4.5 expressed happiness about half as often as Claude 4, though distress remained steady.