What Happens When You Press Enter in Claude Code

Description

What actually happens between pressing Enter and seeing Claude Code's response? Most developers use AI coding tools every day but can't explain the full journey. This is the AI era's version of "what happens when you type a URL into a browser." I trace every step: from keystroke through six processing layers, system prompt assembly from 110+ modular components, the API payload, the agentic loop that drives all tool use, the 18 built-in tools and their permission pipeline, model routing between Haiku, Sonnet, and Opus, automatic context compaction at 200K tokens, sub-agents with isolated context windows, and the extended system of hooks, skills, and session persistence. Whether you use Claude Code daily or you're preparing for your next AI engineering interview, understanding the internals makes you a better user of the tool. ⏱️ TIMESTAMPS 0:00 Introduction 0:58 The Keystroke Enters the System 2:50 The API Payload 3:19 The Agentic Loop 5:31 Tool Execution 7:12 Model Routing 8:23 Context Window and Compaction 10:31 Sub-Agents 11:49 The Extended System 13:03 Conclusion 🔗 LINKS & RESOURCES Claude Code https://claude.ai/code Claude Code Documentation https://docs.anthropic.com/en/docs/claude-code Anthropic API Reference https://docs.anthropic.com/en/api Join the Discord Community https://discord.gg/PKgAUuGnGG Follow on X/Twitter https://x.com/thegraytcat 🐱 THE GRAY CAT AI meets code. Building next-generation software with modern AI tooling. Covering AI IDEs, Claude Code, MCP integrations, and TypeScript/Node.js development. New videos every week. Subscribe and hit the bell!