Anthropic Launches Claude 4 Sonnet and Opus: Smarter AI Models for Coding and Complex Reasoning

Hans India

23-05-2025

Anthropic, the AI research company founded by former OpenAI employees, has officially launched two advanced AI models — Claude 4 Sonnet and Claude 4 Opus — at its first-ever developer conference. Designed to push the limits of coding, reasoning, and long-term task performance, the company claims that Opus 4 is now the most powerful AI coding model in the world.
'Claude Opus 4 is the world's best coding model, with sustained performance on complex, long-running tasks and agent workflows,' the company stated in its official blog post.
These models represent Anthropic's next major leap in AI development. Claude Opus 4 is tailored for developers managing intensive, time-consuming tasks and large-scale workflows. Claude Sonnet 4, meanwhile, is a refined, faster alternative to its predecessor, Claude Sonnet 3.7, offering solid performance in more general-use scenarios — and it's now accessible to free-tier users. In contrast, access to Claude Opus 4 is limited to paid subscribers.
Anthropic is placing a strong emphasis on the models' ability to reason and handle complex scenarios with consistency and clarity. Opus 4 scored an impressive 72.5% on the SWE-bench and 43.2% on the Terminal-bench — both respected benchmarks for coding tasks. These scores reflect the model's capacity to maintain high performance over extended periods, an essential trait for long-duration software projects and AI agent functions.
While Sonnet 4 isn't as powerful as Opus, it performs commendably with a 72.7% score on SWE-bench. According to Anthropic, the Sonnet model delivers a strong balance between speed and accuracy, making it suitable for users who need efficiency without sacrificing output quality.
One standout feature across both models is their ability to engage in what Anthropic describes as 'extended thinking.' This functionality allows the models to pause their reasoning, use external tools like code execution or web search, and then resume their task, now with added context and depth. Tool usage can also occur in parallel, enhancing productivity in more intricate workflows.
The Claude 4 models are also designed to be remembered. If granted access to local files, they can extract important facts, store them, and recall them in future interactions — a big step forward in developing AI with useful long-term memory. Anthropic showcased this by having Opus 4 access files during a game of Pokémon, where it successfully created a 'Navigation Guide' while keeping track of its prior actions.
Anthropic has also rolled out four new API features alongside the model launch: a code execution tool, a connector for Multi-Component Programs (MCP), a Files API, and one-hour prompt caching. These updates aim to make it easier for developers to create more responsive and intelligent AI agents.
To further demystify AI decision-making, the company has introduced a new 'thinking summaries' feature. Generated by a smaller AI model, these provide short, digestible explanations of the model's reasoning. For those wanting a deeper look, full reasoning chains are still available in Developer Mode.
With these launches, Anthropic is not just expanding its model lineup — it's staking a bold claim in the future of AI development, focusing on deeper reasoning, better tools, and models that think more like humans.