CLAUDE_CONTEXT_COLLAPSE

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CONTEXT_COLLAPSE is a Claude Code environment variable: Collapses context on the fly, with a dedicated model to do it. A more aggressive context-management primitive than auto-compact, aimed at keeping long agentic runs inside the window. Removed between v2.1.269 and v2.1.283, so current releases ignore it. It is not in the official reference.

How to set it

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

export CLAUDE_CONTEXT_COLLAPSE=<value>
claude

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

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

Release notes that mention it

• Claude Code v2.1.209 — Auto Mode Grows Up

Related variables

• CLAUDE_CONTEXT_COLLAPSE_MODEL
• 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_DISABLE_1M_CONTEXT: Disable extended 1M token context window.
• CLAUDE_CODE_SAVE_HOOK_ADDITIONAL_CONTEXT: Extra context passed to save hooks.
• CLAUDE_CODE_RESUME_TOLERATES_CONTEXT_APPENDS
• CLAUDE_CODE_RESUME_TOLERATES_CONTEXT_SEEDS
• CLAUDE_AFTER_LAST_COMPACT: Request only conversation logs after last compaction.

Frequently asked questions

All variables, searchable: Claude Code environment variables.