If you’re using Claude Code, there’s a feature you should know about that gives you visibility into how your context window is being used. The /context skill breaks everything down so you can see exactly where your tokens are going.

Here’s what it shows you:

• System prompt – the base instructions Claude Code operates with
• System tools – the built-in tool definitions
• Custom agents – any specialized agents you’ve configured
• Memory files – your CLAUDE.md files and auto-memory
• Skills – any skills loaded into the session
• Messages – your entire conversation history

Messages is where you have the most control, and it’s also what grows the fastest. Every prompt you send, every response you get back, every file read, every tool output; it all shows up in your message history.

Then there’s the free space, which is what’s left for actual work before a compaction occurs. This is the breathing room Claude Code has to think, generate responses, and use tools.

You’ll also see a buffer amount that’s reserved for auto-compaction. You can’t use this space directly, it’s set aside so Claude Code has enough room to summarize the conversation and hand things off cleanly.

Why This Matters

Understanding your context usage helps you work more efficiently. A few ways to keep your context lean:

• Start fresh sessions for new tasks instead of reusing a long-running one
• Be intentional about file reads — only read what you need, not entire directories
• Use sub-agents — when you delegate work to a sub-agent, it runs in its own context window instead of yours. All those file reads, tool calls, and intermediate reasoning happen over there, and you just get the result back. It’s one of the best ways to preserve your primary context for the work that actually needs it.
• Trim your CLAUDE.md — everything in your memory files loads every session, so keep it tight

I’ll dig into sub-agents more in a future post. For now, don’t forget about /context