Claude code execution adds persistent REPL state

Anthropic has added persistent REPL state and programmatic tool calling to Claude’s code execution tool.

The `code_execution_20260120` version is supported by the Python, TypeScript, Go, Java, Ruby, PHP and C# SDKs, with no beta header required.

It’s available on Claude Fable 5, Mythos 5, Opus 4.5 and newer, and Sonnet 4.5 and newer.