CLAUDE_CODE_AUTO_COMPACT_WINDOW

Updated October 23, 2026 by Alex Sorokoletov

CLAUDE_CODE_AUTO_COMPACT_WINDOW is a Claude Code environment variable: Controls the token window threshold at which automatic context compaction kicks in. Works alongside the existing CLAUDE_AUTOCOMPACT_PCT_OVERRIDE variable but likely provides a fixed token count rather than a percentage — giving more precise control over when the conversation is summarized and trimmed. Added between v2.1.77 and v2.1.79 and still present in v2.1.310. It is listed in the official reference.

How to set it

For one session, export it in the shell that starts Claude Code:

export CLAUDE_CODE_AUTO_COMPACT_WINDOW=<value>
claude

To apply it to every session, add it to the env object of a settings file:

// ~/.claude/settings.json
{
  "env": {
    "CLAUDE_CODE_AUTO_COMPACT_WINDOW": "<value>"
  }
}

Release notes that mention it

• Claude Code v2.1.75 — 2 New Environment Variables: Auto-Compact Window & Plugin Options
• claude-code-env-vars-v2-1-304

Related variables

• DISABLE_AUTO_COMPACT: Disable automatic compaction only (manual /compact still works).
• CLAUDE_CODE_AUTO_MODE_COMPACT_THREAD_RULE
• CLAUDE_AFTER_LAST_COMPACT: Request only conversation logs after last compaction.
• CLAUDE_CODE_AUTO_MODE_PRIOR_ASSISTANT_CONTEXT: Feeds prior assistant turns into the decision, so the classifier can see the reasoning behind an edit.
• CLAUDE_CODE_AUTO_MODE_SIBLING_CONTEXT: Includes sibling files (or sessions) when classifying.
• CLAUDE_CODE_IDLE_COMPACT_MIN_TOKENS: Sets the minimum conversation size, in tokens, before idle compaction runs.
• DISABLE_CLAUDE_CODE_SM_COMPACT: Disable session memory compaction.
• DISABLE_COMPACT: Disable all compaction (manual + auto).

Frequently asked questions

All variables, searchable: Claude Code environment variables.