Anthropic upgrades Claude with new Opus 5.5 model, details here

Anthropic has released its latest AI model with Claude Opus 5.5. The new version arrives about two months after the previous Opus model upgrade, matching Anthropic’s previous upgrade cadence. Anthropic Claude Opus 5.5 Anthropic currently offers a few AI models under the Claude umbrella. The three main models are Haiku (smallest and cheapest), Sonnet (medium size and price), and Opus (largest and most expensive of the three). There’s also Fable/Mythos, which is even more capable and costly, which represents Anthropic’s highest tier. Opus 5.5 is here! 🎉 It's honestly such a nice model to work with. Feels like Fable, but ~30% faster and ~40% cheaper per task than Opus 5. Go try it out! pic.twitter.com/zwo83sbgez— Lydia Hallie ✨ (@lydiahallie) September 22, 2026 Today’s release upgrades Claude’s Opus model from version 5 to version 5.5. “Opus 5.5 is our first model since we called for pacing the frontier,” Anthropic says. “As with previous models, it was tested by external evaluators before release, including METR and Frontier Design. On our most comprehensive alignment test, it achieves the strongest score to date.” Here’s what Anthropic says about Opus 5.5 performance: Opus 5.5 is a major step up from Opus 5. It’s the new leading model, and early testers saw large jumps in performance on their most complex work. One tester completed a 680,000-line code migration in less than a day—work that would have taken an engineering team weeks. It’s good at finding and fixing inefficiencies in software: when we asked it to cut load times across every page of a web app, Opus 5.5 succeeded 39 of 40 times, while Opus 5 made smaller improvements that also altered the app’s behavior. A different tester had several Claude models build a game from a single prompt; Opus 5.5 scored higher than any other model on the strength of its graphics and polish. When it comes to coding specifically, here’s what Anthropic says: Opus 5.5 is particularly good at long and sprawling jobs like codebase-wide migrations and audits. An early tester used it to audit and fix a 200,000-line codebase in under three hours, where Opus 5 took over 20 hours and used 2.5x as many tokens. In an internal test, we asked Opus 5.5 and Fable 5.1 to translate HAProxy, widely used software that balances web traffic loads across servers, from C into Rust. Both rewrites passed nearly all of HAProxy’s own regression tests, but Opus 5.5 finished in 9.5 hours compared to 12 for Fable 5.1, and cost 51% less. Opus 5.5 delivers frontier results on agentic coding at a fraction of the cost. At its default effort level on FrontierCode, it beats GPT-6 Astra at roughly 20% of the cost per task. On Terminal Bench 4.0, it matches Astra for about 40% of the cost, while on CursorBench it beats GPT-5.6 Sol by 11 points for about a third of the cost. Additionally, pricing has been adjusted for Opus 5.5 compared to Opus 5: Opus 5.5 requires less compute to serve than Opus 5, and its pricing reflects that. Our tests show that at default settings it will cost 40% less than Opus 5 on typical workloads. Input and output tokens are $4 and $20 per million, 20% less than Opus 5. Cache reads (which make up the majority of agentic and coding work costs) are $0.20 per million tokens, 60% less than Opus 5. Opus 5.5 also generates output more than 30% faster than Opus 5. In addition to the price drop, we’re increasing five-hour usage limits on Pro, Max, and Team plans. We’re also providing subscription users a rate limit reset, which you can now save and use whenever you choose. The new Claude Opus 5.5 model is now available. Looking ahead, Anthropic says both Claude Sonnet 5.5 and Claude Haiku 5.5 models will arrive “in the coming weeks, with many of the same improvements to performance, efficiency, and safety.” You can learn much more about the new Claude Opus 5.5 model here. Introducing Claude Opus 5.5, the first model in our new Claude 5.5 family.It performs at the level of Claude Fable 5.1 for most tasks, and costs 40% less to run than Opus 5. pic.twitter.com/Q9C2VKQ79f— Claude (@claudeai) September 22, 2026 FTC: We use income earning auto affiliate links. More.