agentmods.dev

PreToolUse

A set of hooks that runs checks before selected tools are used. It guards certain Git operations and scans staged changes for credentials before allowing a commit.

In plain words
What is it for?
Use it to protect Git operations, scan commits for secrets, and run Heimdall's command-pattern checks before tools such as Bash, Read, Grep, Glob, Agent, Write, and Edit are used.
Why use it?
Unsafe Git actions and accidentally committed secrets can damage a repository or expose access credentials. These checks provide an automatic pause before those operations proceed.

Hook

5 11d ago A scan tokens not measured original MIT
View the source file randomittin/heimdall
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/randomittin/heimdall/pre-tool-use
Clone the repo
git clone --depth 1 https://github.com/randomittin/heimdall
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 original No closer match found 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.

hooks/hooks.json · 49 lines

How it starts

The opening of the file, as written. The whole thing — 49 lines — stays where its author put it; the contents beside it link to each section on GitHub.

{
  "PreToolUse": [
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": "INPUT=$(cat); CMD=$(printf '%s' \"$INPUT\" | jq -r '.tool_input.command // empty'); PLUGIN=\"${CLAUDE_PLUGIN_ROOT:-$(git rev-parse --show-toplevel 2>/dev/null || pwd)}\"; SCAN=\"$PLUGIN/bin/secret-scan\"; GITGUARD=\"$PLUGIN/bin/heimdall-git-guard\"; if [ -x \"$GITGUARD\" ] && printf '%s\\n' \"$CMD\" | grep -qE '(^|[;&|]|[[:space:]])git([[:space:]]+-C[[:space:]]+[^[:space:]]+)?[[:space:]]+(add|commit|merge|rebase|stash|cherry-pick|revert|am|apply|pull)([[:space:]]|$)'; then \"$GITGUARD\"; fi; if printf '%s\\n' \"$CMD\" | grep -qE '(^|[;&|]\\s*)git\\s+commit'; then if [ -x \"$SCAN\" ]; then if ! OUT=$(\"$SCAN\" 2>&1); then ESC=$(printf '%s' \"$OUT\" | jq -Rsa . | sed -e 's/^\"//' -e 's/\"$//'); printf '{\"error\": \"BLOCKED: secret detected in staged changes by gitleaks. A credential must never enter history. Remove it from the staged diff before committing. --- %s\"}' \"$ESC\"; exit 2; else printf '%s\\n' \"$OUT\" >&2; fi; fi; fi; if printf '%s\\n' \"$CMD\" | grep -qE '^git\\s+push'; then HSTATE=\"$PLUGIN/bin/heimdall-state\"; [ -x \"$HSTATE\" ] || HSTATE=heimdall-state; QGOUT=$(\"$HSTATE\" check-quality-gates 2>&1); QGRC=$?; if [ \"$QGRC\" = 2 ]; then ESC=$(printf '%s' \"$QGOUT\" | jq -Rsa . | sed -e 's/^\"//' -e 's/\"$//'); printf '{\"error\": \"BLOCKED: pre-push quality gate failed. CLAUDE.md enforces quality gates before git push: all tests passing, lint clean, no untested changes. Fix the failing gate, re-run the suite, then record the result with `heimdall-state mark-clean` before pushing. --- %s\"}' \"$ESC\"; exit 2; elif [ \"$QGRC\" = 0 ]; then printf '%s\\n' \"$QGOUT\" >&2; else printf 'heimdall: quality-gate verdict UNAVAILABLE (exit %s) - the gates were NEVER EVALUATED, which is not a pass. Run `heimdall-state init` then `heimdall-state mark-clean` in this checkout to arm the pre-push gate. Allowing push to proceed. --- %s\\n' \"

Read the full file on GitHub · 49 lines

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.

  1. 2d ago First seen · 49 lines scan A c1b0101fbe4d

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository randomittin/heimdall (5 stars, last pushed 11d 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. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Code reviewGit and workflowPlanningai-codinganthropicclaude-codeclaude-pluginclideveloper-tools
Related

Other hooks, from other repositories

PostToolUse

Runs after a tool call finishes for tool == "Write" && tool_input.file_path matches "config\.json$" tool calls, running an inline shell check. From charles001-wong/autocode-flow.

charles001-wong/autocode-flow · not measured

PreCompact

Runs before the context is compacted, running an inline shell check. From zalom/plastic.

zalom/plastic · not measured

SessionStart

Runs when a session starts, executing update-check.js via node. From KevinZai/commander.

KevinZai/commander · not measured

PreToolUse

Runs before the agent uses a tool for Write and Edit tool calls, executing validate-plugin.sh. From ivan-magda/claude-code-plugin-template.

ivan-magda/claude-code-plugin-template · not measured

SessionStart

Runs when a session starts, executing coaltipple-conductor.js via node. From TheColliery/CoalTipple.

TheColliery/CoalTipple · not measured

PreToolUse

Runs before the agent uses a tool for Bash tool calls, running an inline shell check. From roboticforce/sugar.

roboticforce/sugar · not measured