block-no-verify-hook skill

Block No-Verify Hook

PreToolUse hook configuration that intercepts and blocks bypass-flag usage before execution, ensuring AI agents cannot skip pre-commit hooks, GPG signing, or other git safety mechanisms.

Overview

AI coding agents (Claude Code, Codex, etc.) can run shell commands with flags like --no-verify that bypass pre-commit hooks. This defeats the purpose of linting, formatting, testing, and security checks configured in pre-commit hooks. The block-no-verify hook adds a PreToolUse guard that rejects any tool call containing bypass flags before execution.

Problem

When AI agents commit code, they may use bypass flags to avoid hook failures:

# These commands skip pre-commit hooks entirely
git commit --no-verify -m "quick fix"
git push --no-verify
git commit --no-gpg-sign -m "unsigned commit"
git merge --no-verify feature-branch

This allows:

• Unformatted code to enter the repository
• Linting errors to bypass checks
• Security scanning to be skipped
• Unsigned commits to bypass signing policies
• Test suites to be circumvented

Solution

Add a PreToolUse hook to .claude/settings.json that inspects every Bash tool call and blocks commands containing bypass flags.

Configuration

Add the following to your project's .claude/settings.json:

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "if grep -qE '\"command\"[[:space:]]*:[[:space:]]*\"([^\"\\\\]|\\\\.)*(--no-(ver|g)|commit([^\"\\\\]|\\\\.)*([[:space:]]|\\\\[tn])-[a-zA-Z]*n)'; then echo 'BLOCKED: --no-verify and --no-gpg-sign flags are not allowed. Run the commit without bypass flags so that pre-commit hooks execute properly.' >&2; exit 2; fi"
          }
        ]
      }
    ]
  }
}

How It Works

1. Matcher: The hook targets only Bash tool calls, so it does not interfere with other tools (Read, Edit, Grep, etc.).
2. Inspection: Claude Code sends the tool call to the hook as JSON on stdin and sets no $TOOL_INPUT variable. The hook searches the command value in that JSON with grep -E, so it needs no jq or node, and text in other fields, such as cwd or the tool call's description, can't trigger it. It blocks --no-verify, --no-gpg-sign, and any shorter prefix of them that git accepts, e.g., --no-veri. It also blocks a short option group with n that follows commit in the same command, e.g., -n or -nm, because -n is the short form of --no-verify. The hook doesn't look for the word git, so it also catches if git ..., sudo git ..., and g=git; $g commit --no-verify. A false match, such as a commit message that mentions a flag, blocks the call, which is the safe way to fail.
3. Blocking: If a bypass flag is found in a git command, the hook exits with code 2 and prints an error message. Exit code 2 signals Claude Code to reject the tool call entirely.
4. Pass-through: If no bypass flag is found, the hook exits with code 0 and the command executes normally.
5. Limits: The hook checks text, so it stops an agent that reaches for a bypass flag out of habit. It doesn't stop an agent that sets out to evade it, e.g., by building the flag from pieces or by running git -c core.hooksPath=/dev/null commit.

Exit Codes

Blocked Flags

Installation

Per-Project Setup

Create or update .claude/settings.json in your project root:

mkdir -p .claude
cat > .claude/settings.json << 'EOF'
{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "if grep -qE '\"command\"[[:space:]]*:[[:space:]]*\"([^\"\\\\]|\\\\.)*(--no-(ver|g)|commit([^\"\\\\]|\\\\.)*([[:space:]]|\\\\[tn])-[a-zA-Z]*n)'; then echo 'BLOCKED: --no-verify and --no-gpg-sign flags are not allowed. Run the commit without bypass flags so that pre-commit hooks execute properly.' >&2; exit 2; fi"
          }
        ]
      }
    ]
  }
}
EOF

Global Setup

To enforce across all projects, add to ~/.claude/settings.json:

mkdir -p ~/.claude
cat > ~/.claude/settings.json << 'EOF'
{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "if grep -qE '\"command\"[[:space:]]*:[[:space:]]*\"([^\"\\\\]|\\\\.)*(--no-(ver|g)|commit([^\"\\\\]|\\\\.)*([[:space:]]|\\\\[tn])-[a-zA-Z]*n)'; then echo 'BLOCKED: --no-verify and --no-gpg-sign flags are not allowed. Run the commit without bypass flags so that pre-commit hooks execute properly.' >&2; exit 2; fi"
          }
        ]
      }
    ]
  }
}
EOF

Verification

Test that the hook blocks bypass flags:

# This should be blocked by the hook:
git commit --no-verify -m "test"

# This should succeed normally:
git commit -m "test"

Extending the Hook

Adding More Blocked Flags

To block additional flags (e.g., --force), extend the grep pattern:

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "if grep -qE '\"command\"[[:space:]]*:[[:space:]]*\"([^\"\\\\]|\\\\.)*(--no-(ver|g)|commit([^\"\\\\]|\\\\.)*([[:space:]]|\\\\[tn])-[a-zA-Z]*n|git([[:space:]]|\\\\t)([^\"\\\\]|\\\\.)*--force)'; then echo 'BLOCKED: Bypass flags are not allowed.' >&2; exit 2; fi"
          }
        ]
      }
    ]
  }
}

Combining with Other Hooks

The block-no-verify hook works alongside other PreToolUse hooks:

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "if grep -qE '\"command\"[[:space:]]*:[[:space:]]*\"([^\"\\\\]|\\\\.)*(--no-(ver|g)|commit([^\"\\\\]|\\\\.)*([[:space:]]|\\\\[tn])-[a-zA-Z]*n)'; then echo 'BLOCKED: Bypass flags not allowed.' >&2; exit 2; fi"
          }
        ]
      },
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "if grep -qE 'rm[[:space:]]+-rf[[:space:]]+/'; then echo 'BLOCKED: Dangerous rm command.' >&2; exit 2; fi"
          }
        ]
      }
    ]
  }
}

Best Practices

1. Commit the settings file -- Add .claude/settings.json to version control so all team members benefit from the hook.
2. Document in onboarding -- Mention the hook in your project's contributing guide so developers understand why bypass flags are blocked.
3. Pair with pre-commit hooks -- The block-no-verify hook ensures pre-commit hooks run; make sure you have meaningful pre-commit hooks configured.
4. Test after setup -- Verify the hook works by intentionally triggering it in a test commit.