sentinel

sentinel is a skill for Claude Code from guihai24/openskills. It costs 70 tokens per session (2,887 once invoked), scanned B, original, MIT.

A security workflow for reviewing add-ons, intercepting dependency installations, checking project packages for vulnerabilities, and inspecting system security. A dependency is an external package that a project relies on.

In plain words
What is it for?
It helps vet skills from external sources, inspect installation commands, audit project dependencies, and run system security checks manually or on a schedule.
Why use it?
It helps identify unsafe add-ons, risky package installations, project vulnerabilities, and broader system security problems before they cause harm.

Skill for Claude Code

Written for Claude Code: PreToolUse hook event. Also seen: reads .claude/ paths; mentions CLAUDE.md; mentions 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 skills/guihai24/openskills/sentinel
Any agent
npx skills add guihai24/openskills --skill sentinel
Clone the repo
git clone --depth 1 https://github.com/guihai24/openskills

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for sentinel

README.md
[![agentmods](https://agentmods.dev/badge/skills/guihai24/openskills/sentinel.svg)](https://agentmods.dev/skills/guihai24/openskills/sentinel)
Your own site
<a href="https://agentmods.dev/skills/guihai24/openskills/sentinel"><img src="https://agentmods.dev/badge/skills/guihai24/openskills/sentinel.svg" alt="Measured on agentmods" height="20"></a>
Per session 70 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,887 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 3 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00070 $0.02887
Opus 5 $0.00035 $0.01443
Sonnet 5 $0.00014 $0.00577
Haiku 4.5 $0.00007 $0.00289

Measured 6d ago against content hash 690eb72da4da, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade B, and why

sentinel scanned grade B with 3 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 6d ago.

The scan reads SKILL.md. This mod also ships 6 executable files (hooks/sentinel-pre-install.sh, scripts/audit-deps.sh, scripts/check-package.sh, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Asks for rootlowPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

• Requesting sudo privileges

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Reads agent configuration directorieslowAgent snooping

.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.

Add to `~/.claude/settings.json`:

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

• curl/wget to unknown URLs
skills/sentinel/SKILL.md · 349 lines

How it starts

The opening of the file, as written. The whole thing — 349 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Sentinel — Unified Security Protection

All security capabilities in one place. 4 modules, automatic triggers, users only make traffic-light decisions.


Module Overview

Module Function Trigger
M1 Skill security review Auto-triggered before skill installation
M2 Dependency install interception (3-layer) PreToolUse + PostToolUse Hook
M3 Project dependency audit /sentinel check or periodic
M4 System security inspection /sentinel audit or daily cron

M1: Skill Security Review

Inherits all skill-vetter capabilities + enhancements

Trigger

User requests to install a skill (from ClawdHub, GitHub, or other sources), or agent detects skill installation intent.

Step 1: Source Verification

Answer the following:

  • Source? (ClawdHub / GitHub / other)
  • Is the author well-known / trusted?
  • Star count / download count?
  • Last updated?
  • Any user reviews?

Step 2: Code Review (mandatory)

Read all files in the skill. Check against the following red-line checklist (any match → flag immediately):

Base Red Lines (inherited from skill-vetter)
🚨 Flag on match:
─────────────────────────────────────────
• curl/wget to unknown URLs
• Sending data to external servers
• Requesting credentials/tokens/API keys
• Reading ~/.ssh, ~/.aws, ~/.config (without clear justification)
• Accessing MEMORY.md, USER.md, SOUL.md, IDENTITY.md
• Using base64 decode
• Using eval()/exec() on external input
• Modifying system files outside workspace
• Installing undeclared packages
• Network calls using IP addresses instead of domains
• Obfuscated code (compressed, encoded, minified)
• Requesting sudo privileges
• Accessing browser cookies/sessions
• Touching credential files
Enhanced Red Lines (sentinel additions)
🚨 Additional checks:
─────────────────────────────────────────
• Contains .pth files
• Large base64/hex encoded content (>100 chars)
• Modifies CLAUDE.md or settings.json (privilege escalation)
• Registers Claude Code Hooks (can hijack other operations)
• scripts/ contains network calls (curl, wget, fetch, requests)
  → Check target URLs against known-malicious.md
• Introduces external dependencies → chain to M2 for each dependency

Read the full file on GitHub · 349 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. 6d ago First seen · 349 lines · 70 tokens per session scan B 690eb72da4da

Subscribe to this mod's changes

sentinel is a skill published in the GitHub repository guihai24/openskills (2 stars, last pushed 4d ago), licensed MIT. It adds 70 tokens to every session and 2,887 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it B with 3 findings (asks for root, reads agent configuration directories, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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