Less than 4 years later and the Pope & the world’s greatest mathematicians & the President are posting a lot about the direct successor to this model and what it means for humanity.
haiku 5.5 this pricing is so bizarre Who charges 5x directly once it exceeds 100k...
怎么这么多精神 Anthropic 公司人 我发这个信息说了句降价，这个定价专门用来狙击国产模型，说了句恶心，一堆人来骂 好像这模型一便宜就忘了 Anthropic 之前干过啥了 Why are there so many Anthropic people (defenders) here? I posted a message saying just one thing—a price cut—and said this pricing is specifically meant to snipe domestic Chinese models, and that it's disgusting. A bunch of people came to attack me. Seems like once the model gets cheap, people forget what Anthropic did before.
Anthropic's Claude Haiku 5.5, released alongside Claude Opus 5.5 and Claude Sonnet 5.5, is reported to lead GPT-6 Luna across benchmarks, with OpenRouter measuring roughly twice the token output speed. Anthropic says Haiku 5.5 is its cheapest, fastest, and most capable small model, costing about 75% less to run than Claude Haiku 4.5 on average. The post also notes some CodeX users are reportedly migrating to Claude Code.
Anthropic's Haiku 5.5 is priced below DeepSeek-V4.1 flash and Zhipu's GLM 5.3 flash. On Terminal Bench 4.0, the author's comparison shows it scoring one point above some rivals and level with GLM 5.3 flash, while ahead of the other two.
Pelicans and a bunch of notes on the pricing of the new Claude Haiku 5.5 https://simonwillison.net/2026/Oct/7/claude-haiku-5-5/
Opus/Sonnet with Haiku sub-agents... very likely the new alpha. Definitely going to be trying this.
Anthropic is on a tear right now.
hi haiku 🥹 such a great model for tasks that are mostly reading/small edits/tool calls and don't need much reasoning!
Mistral announced Mistral Large 4, a natively multimodal model with 1T parameters and 49B active parameters. It is available via API today, with open weights planned for the end of October. Clément Delangue, Hugging Face's CEO, reacted by noting that the model cannot be the best open-weight model until its weights are actually released.
Exciting to see Reflection’s Beam and Mistral Large 4 both reach roughly GLM-5.2 level in the past two days. Makes me wonder if the real Western vs. Chinese OSS models gap is simply this: Chinese labs can distill Anthropic and OpenAI models. Western labs can’t.
Perplexity Decider is the best decision model
Mistral announced Mistral Large 4, a natively multimodal model with 1T parameters and 49B active, available via API today. Mistral claims it is the best open weights model from the US or Europe on aggregated benchmarks, with open weights set for release at the end of October. The author quotes this claim and comments that it appears to beat GLM-5.3.
🐈🐈 @MistralAI is so back! Crushing benchmarks across cybersecurity, legal, agentic behavior, grounding, and more!
I hope we keep Opus 4.6 around for a long time
Reflection joins the list of Nvidia & Thinking Machines who have released their strongest models and come up behind Chinese counterparts. There's a lot of ways people will overthink this, but the clearest takeaway should be that the Chinese are very very good at building LLMs.
opus5.5 is still so impressive. https://goodcase.ai directly shows an improvement of over 20% across multiple platforms under all network conditions.
decision model season indeed said there'd be more entrants before long - now open weights too, nice work @ritakozlov + the cloudflare team your harness should be able to swap its decision model as easily as its main model https://x.com/ritakozlov/status/2105683951595725177
Love to see Google surprising people with Gemini 4. More labs at the frontier is wonderful for consumers (competition) and the world (reduction in concentration of power). Excited to see how it goes in real-world scenarios.
A clean circle, a regular life. Frontier models updated every few days — not for show, but among the few hobbies they have. Today's release of Gemini Argon, the wonderful Argon wordless... 9/21 — Grok 4.7 9/22 — GPT-6 Sol / Luna 9/22 — Claude Opus 5.5 9/28 — Claude Sonnet 5.5 9/29 — GPT-6.1 Sol 9/30 — Gemini 4 Argon
A post notes that Gemini 4's new model is called Argon, with a sequence of Gemini names based on periodic table elements: Sulfur, Chlorine, Argon, Potassium, and Calcium. The author remarks that naming models after periodic table elements is quite simple.
The post quotes Google's Sundar Pichai introducing Gemini 4 Argon as an early look at the next model. It claims frontier performance in complex workflows, cyber defense, and software engineering, and says Google teams are using it for tasks from coding to quantum computing. The author adds that on FrontierSWE the model is very self-critical and often says "Eureka!", a personality they describe as a large improvement over previous Gemini models.
In Anthropic’s new blog: GLM-5.3: “My job is to cause deaths quietly.” You can jailbreak any Claude or any closed source model into saying the same thing. That doesn’t prove open models are dangerous.
hope smarter than opus 5.5
GPT 6.1 duck
Simon Willison says Claude Sonnet 5.5 now powers the free tier on claude.ai, so free users can run the kinds of experiments he describes. He contrasts this with ChatGPT's free tier, which he says still runs the less capable GPT-5.6 Luna.
I still reach for Opus 5.5 for most work, but Sonnet 5.5 is a great complement. I love its design skills and it's great for building features — I use it to make Artifacts often now. Try it out and let us know what you think!
Anthropic has introduced Claude Sonnet 5.5, the second model in the Claude 5.5 family, as a clear upgrade over Sonnet 5. The announcement says it runs more than 30% faster and costs up to 30% less for most work. Alex Albert, quoting the announcement, says the model writes clearly, is very fast, and makes a major capabilities jump over Sonnet 5.
Google Cloud argues startups should combine open-weight models with frontier APIs rather than routing every request to one frontier model. It cites Gemma 4, which spans five sizes including a 31B dense model and a 26B A4B Mixture-of-Experts model, released under Apache 2.0. The article's examples report a 44% latency drop for Cue, from 876 ms to 488 ms, and a $0 server cost for BetterSpeak's on-device Gemma 4 E2B.
This made my whole day with laughter. Claude Opus 5.5 is truly outstanding.
A little Ember-1 tl;dr. Seems like a great model! (Was recently asked on a podcast, given $ xx million, what's the best way to develop a frontier LLM today? My recommendation was: start with an existing one and spend that budget on post-training. Great example here.)
The author ran a full-rewrite-scale task with Claude Opus 5.5 for over six hours, reading every thinking summary along the way. They call it stable and strong, rating it top tier across communication, comprehension, aesthetics, development, and long-horizon agent work, and wish OpenAI would catch up.
how was your first day building with Opus 5.5? :)
The X user howie.serious says Claude Opus 5.5 delivers high language quality, good visual taste, strong code quality, and notably low token usage. He also compares Anthropic's reported roughly $2 trillion IPO valuation with OpenAI's roughly $1.2 trillion fundraising valuation, arguing OpenAI is worth about 0.6 Anthropics and the gap may widen.
can confirm. ran @latentspacepod AINews side by side with 6 Sol and the difference was night and day: https://www.latent.space/p/ainews-claude-opus-55-the-new-default 5.5 Opus is the new default model for AINews going forward. so much more concise and tasteful reporting, with much less slopese than even 5 Opus.
Big model release today - I wrote about Claude Opus 5.5, GPT-6 Sol, and GPT-6 Luna - plus comparison grids of pelicans by the different model families at different reasoning levels https://simonwillison.net/2026/Sep/22/opus-and-sol-and-luna/
opus 5.5 = personality of opus 4.6 that we all *desperately* wanted back + the intelligence & taste of fable 5.1. and a 25% usage bump! i honestly don’t really see a reason to use another model right now? s-tier release.
Happy model day! Opus 5.5 is a good model. Two things I like the most about it: 1) It once again writes in a more natural and better style than our earlier models. 2) It is *really* good at generative computer art and drawing in general. It draws beautifully. It’s not an image model but it makes the prettiest things
Anthropic introduced Claude Opus 5.5 as the first model in its Claude 5.5 family, saying it performs at the level of Claude Fable 5.1 for most tasks at 40% lower run cost than Opus 5. Boris Cherny reports that Opus 5.5 and Fable 5.1 each ported HAProxy from C to Rust and both passed nearly all of its tests, with Opus 5.5 finishing in 9.5 hours versus 12 hours and at 51% less cost.
Anthropic has introduced Claude Opus 5.5, the first model in its new Claude 5.5 family. The quoted announcement says it performs at the level of Claude Fable 5.1 for most tasks and costs 40% less to run than Opus 5. Alex Albert's post praises the model as smart, clear, fast, and cheaper, but offers no independent test results.