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Environment Variables Reference

Claude Code exposes environment variables for plugins to reference paths and configuration.

Quick Reference

Variable	Available In	Purpose
`${CLAUDE_PLUGIN_ROOT}`	plugin.json config	Plugin installation directory
`$CLAUDE_PROJECT_DIR`	Hook scripts (runtime)	User's project root
`$file`	PostToolUse hooks	Affected file path

The Key Distinction

${CLAUDE_PLUGIN_ROOT} - Where your plugin is installed

Use in plugin.json for hooks, MCP servers, and resources
Resolved at config parse time
References files that ship with your plugin

$CLAUDE_PROJECT_DIR - Where the user is working

Available to hook scripts at runtime
References the user's project files
Use when your plugin needs to operate on user code

Common Pattern: Both Together

A hook that loads plugin config but operates on user files:

#!/bin/bash
# Load config from plugin installation
CONFIG="${CLAUDE_PLUGIN_ROOT}/config/rules.json"

# Operate on user's project
TARGET="$CLAUDE_PROJECT_DIR/src"

jq -r '.patterns[]' "$CONFIG" | while read pattern; do
  grep -r "$pattern" "$TARGET"
done

In plugin.json

{
  "hooks": {
    "PreToolUse": [{
      "matcher": "Write",
      "hooks": [{
        "type": "command",
        "command": "${CLAUDE_PLUGIN_ROOT}/hooks/validate.sh"
      }]
    }]
  }
}

The script validate.sh receives $CLAUDE_PROJECT_DIR at runtime.

Variable Syntax

Config files (plugin.json): Use ${VARIABLE} with braces
Shell scripts: Use $VARIABLE (standard shell syntax)

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