Anthropic unveiled its next-generation AI models on May 22, 2025, introducing Claude Opus 4 and Claude Sonnet 4 with capabilities that push the boundaries of what AI systems can accomplish without human intervention.
Claude Opus 4, which Anthropic describes as "the world's best coding model," achieved a groundbreaking 72.5% score on SWE-bench, a rigorous software engineering benchmark that measures performance on real-world coding tasks. During testing at Rakuten, the model demonstrated remarkable endurance by working autonomously on a complex open-source project for nearly seven hours - a significant leap beyond the minutes-long attention spans of previous AI models.
Claude Sonnet 4, designed as a more efficient alternative to Opus 4, delivers superior coding and reasoning capabilities compared to its predecessor, Claude Sonnet 3.7. Surprisingly, it scored even higher on the SWE-bench at 72.7%, outperforming competitors like OpenAI's Codex-1 (72.1%) and Google's Gemini 2.5 Pro (63.2%).
Both models feature hybrid reasoning capabilities, allowing them to toggle between near-instant responses and extended thinking for deeper reasoning. They can use tools like web search during their thinking process and - when given access to local files - can extract and save key information to maintain continuity and build knowledge over time.
The new models represent a paradigm shift in AI functionality, transforming from simple chatbots to autonomous work agents capable of handling complex, multi-step workflows across thousands of steps. This evolution enables AI to tackle day-long projects from conception to completion while maintaining context throughout.
Claude Sonnet 4 is available to all Claude users, including those on the free tier, while Claude Opus 4 is accessible only to Pro, Max, Team, and Enterprise plan subscribers. Both models are also available via the Anthropic API, Amazon Bedrock, and Google Cloud's Vertex AI, with pricing consistent with previous models: Opus 4 at $15/$75 per million tokens (input/output) and Sonnet 4 at $3/$15.