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Claude Code’s context window holds everything Claude knows about your session: your instructions, the files it reads, its own responses, and content that never appears in your terminal. The timeline below walks through what loads and when. See the written breakdown for the same content as a list.

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What the timeline shows

The session walks through a realistic flow with representative token counts:
  • Before you type anything: CLAUDE.md, auto memory, MCP tool names, and skill descriptions all load into context. Your own setup may add more here, like an output style or text from --append-system-prompt, which both go into the system prompt the same way.
  • As Claude works: each file read adds to context, path-scoped rules load automatically alongside matching files, and a PostToolUse hook fires after each edit.
  • The follow-up prompt: a subagent handles the research in its own separate context window, so the large file reads stay out of yours. Only the summary and a small metadata trailer come back.
  • At the end: /compact replaces the conversation with a structured summary. Most startup content reloads automatically. The skill listing is the one exception.

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Check your own session

The visualization uses representative numbers. To see your actual context usage at any point, run /context for a live breakdown by category with optimization suggestions. Run /memory to check which CLAUDE.md and auto memory files loaded at startup. For deeper coverage of the features shown in the timeline, see these pages: