Claude Code: Features, Commands, Architecture and Best Practices

Claude Code's 200K token context window fills rapidly, with system prompts consuming 30K–45K tokens before any user input, and performance degrading noticeably around 147K tokens of actual usage. Developers must use sub-agents for research, `/clear` between unrelated tasks, `/btw` for quick questions, and `/compact` with focus instructions to maintain performance. Context management is the most critical operational skill for effective use of the tool.

This report analyzes Claude Code’s complete feature set, architecture, and best practices for effective usage. Below are the five most actionable conclusions for developers. 1. Context management is the single most important operational skill. Claude’s 200K token context window fills rapidly — a fresh session starts with ~30K–45K tokens consumed by system prompts, tool definitions, CLAUDE.md, auto memory, and skill descriptions before any user input. Performance degrades noticeably around 147K tokens of actual usage 14 . The essential techniques are: use sub-agents for all research they return summaries, not file contents , /clear between unrelated tasks, /btw for quick questions that never enter history, and /compact with focus instructions when approaching the limit. A “kitchen sink” session where multiple unrelated tasks accumulate context degrades performance measurably.