Claude Code is an agentic coding tool from Anthropic available as a terminal CLI, VS Code extension, JetBrains plugin, desktop app, and at claude.ai.
The core execution model is an agent loop: Claude Code reads files, runs shell commands, makes edits, and checks results in sequence. The agent operates at the project level — spanning multiple files and coordinating changes across a repository — rather than on the currently open file. Permission modes control how much executes autonomously: default mode prompts before each file edit or shell command; Plan mode presents the full execution plan as reviewable markdown before anything runs; auto, bypassPermissions, and acceptEdits modes offer progressively less interruption.
CLAUDE.md files document project-level context (directory structure, architectural decisions, build commands, conventions) that Claude Code reads at session start. The /init command generates a starter CLAUDE.md from the repository structure. The default model is claude-sonnet-4-6; claude-opus-4-6 is available on Max plans. Context window is 1M tokens. Claude Code is not available on the Free plan.
