context-monitor

Monitor how much context window remains during a Claude Code session. Issues graduated warnings so you never get killed by context exhaustion.

Event Configuration

• Event Type: PostToolUse
• Tool Matcher: "" (every tool invocation)
• Category: performance

How It Works

1. Reads Claude Code's debug log to extract actual token usage
2. Falls back to tool-call-count estimation when debug logs are unavailable
3. Saves current % to /tmp/cc-context-pct (other scripts can read this)
4. At CRITICAL/EMERGENCY, writes an evacuation template to your mission file

Warning Thresholds

Level	Remaining	Action
CAUTION	≤40%	Be mindful of consumption
WARNING	≤25%	Finish current task, save state
CRITICAL	≤20%	Run /compact immediately
EMERGENCY	≤15%	Stop everything, evacuate

Environment Variables

Variable	Default	Description
CC_CONTEXT_MISSION_FILE	$HOME/mission.md	Path to mission/state file for evacuation template

Requirements

• jq for JSON parsing
• Claude Code debug logs at ~/.claude/debug/ (optional, falls back to estimation)

Origin

Born from a session that hit 3% context remaining with no warning. The agent died mid-task and all in-flight work was lost.

Source

From claude-code-hooks — battle-tested hooks from 140+ hours of autonomous Claude Code operation.