Prompts, skills, and the AGENTS.md nobody wants to write (and how Anthropic writes theirs)
You’ve watched Claude Code compact a conversation. The context bar fills, it pauses, a summary appears, and it carries on like nothing happened. You probably assumed a housekeeping script trimmed the transcript in the background. It didn’t. The model compacted itself. When the window fills, Claude Code sends a long, specific prompt telling the model how to summarize its own conversation. Then it does, same model, same turn. The thing managing your context window is just another instruction.