Context Guard

Context Guard

What It Does

Context Guard adds two PostToolUse hooks and one quality rule to a project. The hooks detect when AI context files (CLAUDE.md, AGENTS.md, GEMINI.md, .cursorrules, copilot-instructions.md, .windsurfrules, .clinerules) are out of date and nudge the developer to update them.

Claude Code only. These hooks use Claude Code's hook system (PostToolUse events, .claude/settings.json configuration). OpenCode, Codex CLI, Cursor, Windsurf, Cline, and Gemini CLI do not support Claude Code hooks. The quality rule (.claude/rules/context-quality.md) is also Claude Code-specific.

Cross-tool features like skills (.claude/skills/) and AGENTS.md work in OpenCode and Codex CLI without Context Guard.

Components

Hook: context-drift-check.sh

• Event: PostToolUse on Bash (filters for git commit commands)
• Fires: After a successful git commit
• Checks:
  1. Compares each context file's last-modified commit vs the most recent source-code commit
  2. Detects broken file-path references inside context files
  3. Flags when package.json or pyproject.toml changed more recently than context files
• Output: Lists stale files and recommends /ai-context audit, or stays silent if everything is current
• Throttle: Max once per hour via .git/.context-guard-last-check timestamp

Hook: context-structural-change.sh

• Event: PostToolUse on Write|Edit
• Fires: After creating or editing structural files (commands, skills, agents, rules, manifests, config)
• Reminds: Which context files may need updating based on the type of change
• File patterns:
  • commands/*.md → AGENTS.md, CLAUDE.md, llms.txt
  • .claude/skills/*/SKILL.md → AGENTS.md, CLAUDE.md, llms.txt
  • .claude/agents/*.md → AGENTS.md
  • .claude/rules/*.md → CLAUDE.md, AGENTS.md
  • package.json, pyproject.toml, config files → all context files

Rule: context-quality.md

Auto-loaded every session. Establishes cross-file consistency, path verification, version accuracy, command accuracy, and a sync-points table mapping project changes to context files.

Installation

The /context-guard install command:

1. Copies hook scripts to .claude/hooks/ in the target project
2. Merges hook configuration into .claude/settings.json
3. Copies the quality rule to .claude/rules/context-quality.md
4. Makes hook scripts executable

Settings.json Configuration

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Bash",
        "hooks": [{
          "type": "command",
          "command": ".claude/hooks/context-drift-check.sh"
        }]
      },
      {
        "matcher": "Write|Edit",
        "hooks": [{
          "type": "command",
          "command": ".claude/hooks/context-structural-change.sh"
        }]
      }
    ]
  }
}

Uninstallation

The /context-guard uninstall command removes the hook scripts, settings.json entries, and the quality rule.

Customisation

Throttle Interval

Edit context-drift-check.sh line with 3600 (seconds) to change the check interval. Set to 0 to check on every commit.

File Patterns

Edit context-structural-change.sh case statement to add or remove structural file patterns.

Troubleshooting