Your First 30 Minutes in an Unfamiliar Repo with Claude Code

Most people open an unfamiliar repo and immediately ask Claude Code: "what does this codebase do?" Then they watch it read 15 files, fill the context with raw file contents, and produce a vague summary that contaminates every subsequent turn. There's a better workflow. It comes directly from understanding how Claude Code's subagent architecture works. Here's the exact sequence. Why Most Onboarding Goes Wrong When you run exploration in the main thread, the results stay in the main context. Every file read, every grep result, every intermediate summary — all of it piles up. By the time you're ready to do actual work, you're 50K tokens in, the model is getting fuzzy on early instructions, and you've burned budget on exploration residue. The source reveals why: LLM quality degrades as context grows longer. The authors knew this. So they built the AgentTool specifically to isolate exploration in subagents that can't write to the main AppState. Results come back as summaries only. That's th