When your context fills up

Claude Code compacts automatically as you approach the limit, so a full context window doesn't end your session. The automatic pass works the same way as the /compact step in the timeline. See When context fills up for what it preserves.

You can also act before the automatic pass runs:

• Compact with a focus: run /compact with instructions, like /compact focus on the auth bug fix, before starting a long new task. The summary keeps what you choose instead of what the automatic pass guesses is important.
• Compact part of the conversation: run /rewind, select a message, and choose Summarize from here or Summarize up to here. See Rewind and summarize for what each option keeps and how to guide the summary.
• Compact earlier: run /autocompact with a token count, like /autocompact 500k, to set how full the context window gets before the automatic pass runs. See Set the auto-compact window for accepted values and overrides.
• Clear between tasks: run /clear when switching to unrelated work. Old conversation crowds out the files you need next and costs tokens on every message.
• Delegate large reads: send research to a subagent so the file contents stay in its context window, not yours.

If you need a larger window rather than a smaller conversation, Fable models, Sonnet 5, Opus 4.6 and later, and Sonnet 4.6 support a 1 million token context window. See Extended context for availability by plan and how to select a [1m] model variant. Compaction works the same way at the larger limit.

Sonnet 5 runs with the 1M context window and has no [1m] variant to select. See Sonnet 5 context window for its auto-compaction thresholds and the LLM gateway exception.

The point where automatic compaction runs depends on your model and configuration. See Default auto-compact thresholds for the boundaries per model, and Correct the window for a gateway or custom model ID if Claude Code assumes the wrong window for your model ID, such as an LLM gateway alias.