Say hello to Claude Sonnet 4.5, which Anthropic calls 'the best coding model in the world'

Anthropic has formally announced Claude Sonnet 4.5, a new AI model specifically made for coding. During its announcement, Anthropic didn’t mince words, calling Claude Sonnet 4.5 the “best coding model in the world.” Starting today, it’ll power Claude Code, a popular choice for vibe coders and professionals alike. 

The new model is a step up from the old model and seems to be able to do quite a lot. According to Cognition co-founder and CEO Scott Wu, the new model features “the biggest jump we’ve seen since the release of Claude Sonnet 3.6” and can “run longer, handle harder tasks, and deliver production-ready code.”

Anthropic shows this through a variety of charts demonstrating how effective the model can be. For example, Claude Sonnet 4.5 has fewer instances of misaligned behaviors than its direct competitors, including older models from Anthropic. Anthropic AI researcher David Hershey told TechCrunch that he’s seen the model code for 30 hours without interruption in early trials, so overall performance may be difficult to show in benchmarks. 

In addition to better smarts, Anthropic also announced several new features for Claude Code to coincide with the release. That includes checkpoints, a feature that Anthropic says has been requested quite a lot. Checkpoints will save snapshots of the code the user is working on, and then grant the ability to roll back to a prior checkpoint if things go off the rails. There is also a new context editing feature and memory tool that allows AI agents to run longer and handle more complex instructions. 

Anthropic has been on a roll in 2025, as have most AI companies. New models seem to drop every couple of months like clockwork these days. Anthropic’s prior big model release, Claude Opus 4, launched in May 2025, which was also designed for advanced coding. OpenAI launched its latest GPT-5 in early August, and Google joined the fray with Gemini 2.5 over the summer. Thus, AI fans have a lot of new stuff to check out if they haven’t done so in a while. 

Disclosure: Ziff Davis, Mashable’s parent company, in April filed a lawsuit against OpenAI, alleging it infringed Ziff Davis copyrights in training and operating its AI systems.