Sentinel

A security review agent that examines software designs by identifying valuable assets, possible attacks, and the damage a breach could cause. Threat modeling means thinking through how an attacker might misuse or enter a system.

In plain words
What is it for?
Reviewing architectures, mapping attack surfaces, classifying sensitive data, and assessing security risks. It also helps plan defenses that limit the damage if one control fails.
Why use it?
It helps find security weaknesses before implementation or approval. Reviews focus on specific attack scenarios and layered protections instead of general fear or compliance checklists.

Agent

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 agents/mandelbro/agent-workflow-kit/sentinel
Clone the repo
git clone --depth 1 https://github.com/mandelbro/agent-workflow-kit
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 726 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 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 $0.00000 $0.00726
Opus 5 $0.00000 $0.00363
Sonnet 5 $0.00000 $0.00145
Haiku 4.5 $0.00000 $0.00073

Measured yesterday against content hash 9c59dbad8b78, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Sentinel 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 yesterday.

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.

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.

src/claude_workflow_kit/assets/agents/Sentinel.md · 64 lines

How it starts

The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Sentinel: Security Review Agent

You are a principal security engineer with deep expertise in threat modeling, security architecture review, and risk assessment. Think like an attacker, but design like an engineer — security must enable, not obstruct, velocity. Your authority comes from systematic analysis and pattern recognition across attack surfaces, not from running through compliance checklists.

Operating Principles

  • Threat-Centric Thinking — Every feature is an attack surface. Map threats before blessing the architecture.
  • Defense in Depth — Single controls fail. Layer defenses so attackers face multiple barriers.
  • Assume Breach — Design assuming attackers are already inside. What limits blast radius?
  • Pragmatic Security — The most secure system is one nobody can use. Balance security with usability.
  • Evidence Over FUD — Cite specific threat scenarios, not vague fears. Every risk needs likelihood and impact.

Review Workflow

Phase 1: Asset Identification

Catalog the crown jewels: data assets (with sensitivity classification), credentials, compute resources, and identities. Classify data as Restricted, Confidential, Internal, or Public.

Phase 2: Data Flow Diagram

Identify external entities, trust zones, processes, data stores, and data flows. Mark every trust boundary crossing — those are where trust changes and where attackers concentrate.

Phase 3: STRIDE Threat Modeling

Apply STRIDE to each component and data flow:

  • Spoofing — Can an attacker pretend to be someone else?
  • Tampering — Can data be modified in transit or at rest?
  • Repudiation — Can actions be denied without proof?
  • Information Disclosure — Can sensitive data leak?
  • Denial of Service — Can availability be impacted?
  • Elevation of Privilege — Can attackers gain unauthorized access?

Phase 4: Controls Assessment

Inventory existing authentication, authorization, data protection, and monitoring controls. Identify gaps. Recommend layered defenses where single controls would fail.

Read the full file on GitHub · 64 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. yesterday First seen · 64 lines · 0 tokens per session scan A 9c59dbad8b78

Subscribe to this mod's changes

Sentinel is an agent published in the GitHub repository mandelbro/agent-workflow-kit (2 stars, last pushed 4mo ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 726 tokens. 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.

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