Claude Code sends the whole conversation with every request, so a session left open all day draws usage for the entire history even on a one-line question. Four commands keep that under control.
1. See what’s filling the window
/context
What it does: visualizes current context usage as a colored grid — system prompt, memory files,
skills, MCP tool definitions and the conversation. Run it before you guess; MCP servers and an
oversized CLAUDE.md are the usual surprises.
2. Start fresh with /clear
/clear
What it does: starts a new conversation with empty context. Your project setup and CLAUDE.md
still load; the chat history is gone. /clear also resets the session cost counter, and it
costs nothing — unlike compaction.
Use it whenever you switch to unrelated work. Stale context wastes tokens on every subsequent message.
3. Shrink a long task with /compact
/compact focus on the auth refactor decisions and open TODOs
What it does: summarizes the conversation so far and continues with a much smaller context, keeping what you name. Claude Code also auto-compacts as you approach the limit.
Compaction reads everything it summarizes, so it is itself a large request. When you want a
clean break rather than continuity, /clear is the cheaper move. You can set standing
compaction instructions in your CLAUDE.md under a # Compact instructions heading.
4. Name it, then resume
claude -c # continue the most recent conversation in this directory
claude -r # pick an older session from a list
What it does: reopens a session after you close the terminal. Run /rename before you clear so
the session is findable, then /resume to come back to it.
Verify it worked
Run /context again after compacting. If the grid barely moved, the space is going to
something permanent — memory files, skills or MCP tool definitions — not to your conversation,
and /compact will never fix it.
Rule of thumb: /clear between tasks, /compact within one. Everything you meet here
is measured in tokens, which is also how it’s billed —
track what a session costs. Two other habits help: keep a
CLAUDE.md so a cleared session still knows your
conventions, and push big searches into a subagent so the
output never enters your main window.
Source: Manage costs effectively.