A pre-tool hook that runs a command guard before the agent makes Bash command calls. A hook is an automatic action triggered by another action.

Use it to apply the command-guard.py script to Bash tool calls through the configured PreToolUse hook.

It gives the command guard a chance to inspect or restrict shell commands before they run.

PreToolUse — Hook by hex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods

npx agentmods add hooks/hex/claude-guard/pre-tool-use

Clone the repo

git clone --depth 1 https://github.com/hex/claude-guard

Per session not measured What this adds to a session before it is invoked.

When invoked not measured Not applicable: nothing here is loaded into a session.

Security scan A 0 findings. Scan, not verified.

Origin 67% copy Near-identical to another mod in the catalogue.

Security

Grade A, and why

PreToolUse scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the commands this hook runs, not an audit. A hook is shell that executes on your machine at the event it names, which is why every command in it is printed with what was found.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

67% identical to SessionStart — 9 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

hooks/hooks.json · 14 lines

What it actually says

{
  "PreToolUse": [
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": "\"${CLAUDE_PLUGIN_ROOT}\"/hooks/scripts/command-guard.py",
          "timeout": 5
        }
      ]
    }
  ]
}

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2d ago First seen · 14 lines scan A 93cdeaae11ad

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository hex/claude-guard (2 stars, last pushed 1mo ago), licensed MIT. Its token cost is not measured: a hook is shell that never enters the context. A static security scan graded it A with 0 findings. It is 67% identical to SessionStart, differing in 9 lines, and is treated as a copy.

Security claude-code credential-detection destructive-commands guard hooks plugin

PreToolUse

Getting it into your agent

Grade A, and why

Nothing flagged

This is a copy

What it actually says

What this file has done since we first saw it

Other hooks, from other repositories

UserPromptSubmit

MessageDisplay

SessionStart

InstructionsLoaded

UserPromptSubmit

PostToolUse