PreToolUse

A set of checks that runs before the agent writes files, edits code, or runs shell commands. It enforces worktree rules and performs checks before a pull request is merged.

In plain words
What is it for?
Use it to require the agent to work in the correct repository copy and to run formatting checks and tests before merging changes.
Why use it?
It catches workflow and code-quality problems before changes are made or merged. A worktree is a separate working copy of a repository, and a pull request is a proposed code change for review.

Hook for Claude Code

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/openrouterlabs/spawn/pre-tool-use
Clone the repo
git clone --depth 1 https://github.com/OpenRouterLabs/spawn

Made for: Claude Code.

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.

.claude/settings.json · 31 lines

What it actually says

{
  "PreToolUse": [
    {
      "matcher": "Write|Edit",
      "hooks": [
        {
          "type": "command",
          "command": "bun .claude/scripts/enforce-worktree.ts"
        }
      ]
    },
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": "bun .claude/scripts/pre-merge-check.ts"
        }
      ]
    },
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": "bash -c 'INPUT=$(cat); CMD=$(echo \"$INPUT\" | jq -r \".tool_input.command // empty\"); echo \"$CMD\" | grep -qE \"gh pr (merge|ready)\" || exit 0; WT=$(echo \"$CMD\" | grep -oE \"/tmp/spawn-worktrees/[a-zA-Z0-9._/-]+\" | head -1); if [ -n \"$WT\" ] && [ -d \"$WT/packages/cli\" ]; then ROOT=\"$WT\"; else ROOT=$(git rev-parse --show-toplevel 2>/dev/null); fi; if [ -z \"$ROOT\" ] || [ ! -d \"$ROOT/packages/cli\" ]; then echo \"WARNING: Could not find spawn repo for pre-merge checks\" >&2; exit 0; fi; cd \"$ROOT/packages/cli\" || exit 2; echo \"Pre-merge gate: running biome check + bun test in $ROOT/packages/cli ...\" >&2; bunx @biomejs/biome check src/ 2>&1 || { echo \"BLOCKED: biome check failed — fix lint/format issues before merging\" >&2; exit 2; }; bun test 2>&1 || { echo \"BLOCKED: tests failed — fix failures before merging\" >&2; exit 2; }; echo \"Pre-merge checks passed\" >&2'"
        }
      ]
    }
  ]
}
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 · 31 lines scan A ac5ec173f43e

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository OpenRouterLabs/spawn (233 stars, last pushed 1mo ago), licensed Apache-2.0. 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 2026-08-30.