May 22, 2025 · Anthropic

Claude Opus 4 and Claude Sonnet 4 launched, with Files API and code execution in beta

We’ve launched Claude Opus 4 and Claude Sonnet 4, our latest models with extended thinking capabilities. Learn more in Models overview.
The default behavior of extended thinking in Claude 4 models returns a summary of Claude’s full thinking process, with the full thinking encrypted and returned in the signature field of thinking block output.
We’ve launched interleaved thinking in beta, a feature that enables Claude to think in between tool calls. To enable interleaved thinking, use the beta header interleaved-thinking-2025-05-14.
We’ve launched the Files API in beta, enabling you to upload files and reference them in the Messages API and code execution tool.
We’ve launched the Code execution tool in beta, a tool that enables Claude to execute Python code in a secure, sandboxed environment.
We’ve launched the MCP connector in beta, a feature that allows you to connect to remote MCP servers directly from the Messages API.
To increase answer quality and decrease tool errors, we’ve changed the default value for the top_p nucleus sampling parameter in the Messages API from 0.999 to 0.99 for all models. To revert this change, set top_p to 0.999. Additionally, when extended thinking is enabled, you can now set top_p to values between 0.95 and 1.
Our Go SDK has moved from beta to its first stable release.
We’ve added minute and hour level granularity to the Usage page of Console alongside 429 error rates on the Usage page.