this is a great teaching resource. building an agent from scratch really demystifies whats happening inside tools like claude code. the core loop is surprisingly simple - its just read prompt, call LLM with tools, execute tool calls, loop. all the complexity is in the details: how you manage context window limits, how you handle tool errors gracefully, and how you prevent the agent from going in circles.

one thing worth adding as a phase 8 or bonus: context window management. the naive approach of appending every tool result to the conversation history blows up fast when the agent reads large files. implementing summarization or truncation strategies is where most real-world agent engineering time goes.