Three Claude Code implementations: an agent engineering notebook
Agent engineering notes drawn from three implementations. CoreCoder is a minimal implementation written by hand in Python, Claude Code is the production implementation, and learn-claude-code is the teaching implementation. Coverage spans the Agent Loop's transition condition and interrupt repair, tool definitions and file-editing strategy, context injection and three tiers of compression, the long-lived state of QueryEngine, parallel tools and sub-agents, the Hook and Task extension points, multi-agent collaboration, memory / MCP / background tasks / scheduled tasks, and the security defenses around paths and commands.