How Claude Code's System Prompt Engine Actually Works

Claude Code builds its system prompt dynamically from core instructions, conditional tool definitions, user files, and managed conversation history, revealing the critical role of context engineering. The Leak That Revealed The Engine Last week, an accidental source code leak gave us the first clear look under the hood of Claude Code. It wasn't just a static prompt file. The system prompt you rely on for every coding session is a dynamically assembled context built from multiple, often conditional, components.