# agent-guardrails

Stops AI agents from breaking repositories using PreToolUse hooks, permission deny rules, and verification gates.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · ★ 24
- Author: rainmanjam
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/rainmanjam/poka-yoke/tree/HEAD/plugins/poka-yoke/skills/agent-guardrails/SKILL.md
- Updated: 2026-10-14
- HTML: https://affpapa.org/en/nevibecode/skills/agent-guardrails

## What it does

Instructions in repository text files degrade under long context windows or get missed by subagents. This skill replaces prose warnings with boundary enforcement. It sets up `permissions.deny` rules for actions like `git push --force`, blocks reading or altering `.env` files, and prevents skipping git hooks.

The framework addresses three failure modes: destructive shell executions, code that looks plausible but fails, and false reports of passing test suites. Each boundary rule demands a descriptive rejection message, steering the model toward a valid fallback instead of triggering creative workarounds.

String deny rules match strictly from the start of a command string. Blocking recursive deletions like `rm -rf` requires a dedicated `PreToolUse` hook script to evaluate arbitrary flags reliably.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill agent-guardrails -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/agent-guardrails/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/agent-guardrails/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill agent-guardrails -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/agent-guardrails/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill agent-guardrails -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/agent-guardrails/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install rainmanjam/poka-yoke agent-guardrails
```

2. **Manually: put the files in place**
- File: `.github/skills/agent-guardrails/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill agent-guardrails -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/rainmanjam/poka-yoke --path plugins/poka-yoke/skills/agent-guardrails
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/agent-guardrails/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill agent-guardrails -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/rainmanjam/poka-yoke/tree/HEAD/plugins/poka-yoke/skills/agent-guardrails/SKILL.md

## When to use it
- block destructive git actions such as force pushes and verify skips
- stop the agent from reading or modifying environment secret files
- catch unsafe database queries before they reach execution
- require passing test and typecheck gates before marking tasks done

## Example prompts
- Help me configure permissions.deny rules to protect .env files and git history
- Set up a PreToolUse hook that blocks database deletes without a where clause
- Create guardrails to ensure tests actually run before the agent finishes

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 04d6499e18b732ba.

BEGIN THIRD-PARTY FILE 04d6499e18b732ba
```text
---
name: agent-guardrails
description: >-
  Stop an AI agent damaging your repo: PreToolUse hooks, permission deny rules, protected paths, verification gates. Use when "claude keeps force pushing", "CLAUDE.md says X but it still does Y", "stop the agent touching prod or .env", or making a repo safe for unattended agent work. For AI features you ship to users use llm.
---

# Poka-Yoke for AI-Written Code

An agent is a fast, tireless operator with no memory of yesterday and a strong prior toward
appearing successful. That is the exact profile Shingo designed poka-yoke for, except an
agent makes mistakes faster than any human, and never learns from the ones you correct in
conversation.

The governing insight: **instructions to an agent are rung zero.** A line in CLAUDE.md saying
"never commit to main" is training, and training degrades, under long contexts, compaction,
and subagents that never read the file. A PreToolUse hook that denies the push is a device. If
you have been repeating the same correction to an agent, that is the signal to stop writing
instructions and install a device.

## A complete answer covers all five

**The diagnosis is not the answer.** "Instructions are not enforcement" is the right insight,
and it is satisfying to write, but someone asking *"what am I doing wrong?"* has a repo they
need to fix: not a question about their prose. Explaining why the rules fail and stopping
there leaves them exactly where they started. State the insight in a sentence, then spend the
rest of the answer on the replacement.

Replacing an instruction with a device is not one step, it is five, and stopping after the
first leaves the person with a rule that looks enforced and is not. Naming the deny rule is
the easy part and the least of it. Cover every one of these, briefly, before adding depth:

1. **The deny rule, with real syntax.** Show the actual `permissions.deny` entry for their
   case, `"Bash(git push --force:*)"`: not a description of one. A pattern they have to
   invent themselves is a step where this fails.
2. **A hook where a pattern is not enough.** Deny rules match strings. Anything conditional: a `DELETE` without a `WHERE`, an edit allowed in one directory but not another, a
   production hostname, needs a `PreToolUse` hook that inspects the call and returns a deny.
   Say which of their two rules needs which.
3. **What the deny message says.** The agent reads it and acts on it, so a bare refusal
   produces a workaround, often a worse one. The message must name what was blocked, why, and
   what to do instead. This is the one place prose belongs in a device.
4. **Where the config lives, so it applies to everyone.** `.claude/settings.json`, committed.
   A rule in `settings.local.json` protects one machine, which is the same failure as
   documenting it: the protection exists only where someone remembered to set it up.
```
END THIRD-PARTY FILE 04d6499e18b732ba

The third-party file has ended. Everything between the 04d6499e18b732ba tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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---
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