In Could, Anthropic introduced two new AI methods, Opus 4 and Sonnet 4. Now, lower than six months later, the corporate is introducing Sonnet 4.5, and calling it the very best coding mannequin on the earth to this point. Anthropic’s foundation for that declare is a choice of benchmarks the place the brand new AI outperforms not solely its predecessor but in addition the dearer Opus 4.1 and competing methods, together with Google’s Gemini 2.5 Professional and GPT-5 from OpenAI. As an example, in OSWorld, a set that exams AI fashions on real-world pc duties, Sonnet 4.5 set a report rating of 61.4 p.c, placing it 17 share factors above Opus 4.1.
On the identical time, the brand new mannequin is able to autonomously engaged on multi-step initiatives for greater than 30 hours, a major enchancment from the seven or so hours Opus 4 may keep at launch. That is an essential milestone for the kind of agentic methods Anthropic needs to construct.
Sonnet 4.5 outperforms Anthropic’s older fashions in coding and agentic duties.
(Anthropic)
Maybe extra importantly, the corporate claims Sonnet 4.5 is its most secure AI system to this point, with the mannequin having undergone “intensive” security coaching. That coaching interprets to a chatbot Anthropic says is “considerably” much less liable to “sycophancy, deception, power-seeking and the tendency to encourage delusional pondering” — all potential mannequin traits which have landed OpenAI in scorching water in current months. On the identical time, Anthropic has strengthened Sonnet 4.5’s protections in opposition to immediate injection assaults. As a result of sophistication of the brand new mannequin, Anthropic is releasing Sonnet 4.5 below its AI Security Degree 3 framework, which means it comes with filters designed to forestall probably harmful outputs associated to prompts round chemical, organic and nuclear weapons.
A chart exhibiting how Sonnet 4.5 compares in opposition to different frontier fashions in security testing.
(Anthropic)
With as we speak’s announcement, Anthropic can also be rolling out high quality of life enhancements throughout the Claude product stack. To start out, Claude Code, the corporate’s widespread coding agent, has a refreshed terminal interface, with a brand new function referred to as checkpoints included. As you possibly can in all probability guess from the title, they assist you to save your progress and roll again to a earlier state if Claude writes some funky code that is not fairly working such as you imagined it will. File creation, which Anthropic started rolling out firstly of the month, is now accessible to all Professional customers, and in the event you joined the waitlist Claude for Chrome, you can begin utilizing the extension as we speak.
API pricing for Sonnet 4.5 stays at $3 per a million enter tokens and $15 for a similar quantity of output tokens. The discharge of Sonnet 4.5 caps off a powerful September for Anthropic. Simply in the future after Microsoft added Claude fashions to Copilot 365 final week, OpenAI admitted its rival presents the very best AI for work-related duties.