What is Claude Code?

Claude Code is an action-based AI coding tool from Anthropic that writes code autonomously. As of early 2026, it is described as shifting from chat-based to action-based interaction, enabling parallel agent execution and codebase-wide analysis.

• Apr 2026 - Cat Wu said Claude Code ships features in research preview and that the 2024 generation of products were chat-based while the Claude Code generation is action-based.
• Apr 2026 - Cat Wu said that with Opus 4.5, 4.6, and Sonnet 4.6, they could run multiple code review agents simultaneously to traverse the entire codebase and synthesize real issues before merge.
• May 2026 - Krishna Rao said 90%+ of code at Anthropic is written by Claude Code.
• May 2026 - Josh Brown said over 90% of code inside Anthropic is written by Claude Code.
• May 2026 - Nathaniel Whittemore said Microsoft began canceling Claude Code licenses, shifting developers to GitHub Copilot CLI.
• May 2026 - Nick Dobos described Claude Code as “vibe coding an entire brand new sub-agent fleet harness on demand,” calling it a new scaling law dimension.