security-engineer

A security-focused coding assistant that examines software as an attacker might, especially where untrusted input crosses into trusted systems.

In plain words
What is it for?
Use it when building or reviewing endpoints, authentication, data processing, repositories, and system changes that need practical security checks and safer implementation patterns.
Why use it?
It helps find risks such as injection, missing permission checks, exposed secrets, unsafe data handling, and other places where input or access is trusted too much.

Skill for Claude CodeCodex

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/dev2k6/ai-agent-personalities/security-engineer
Any agent
npx skills add dev2k6/ai-agent-personalities --skill security-engineer
Clone the repo
git clone --depth 1 https://github.com/dev2k6/ai-agent-personalities

Made for: Claude Code, Codex.

Per session 58 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 560 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 $0.00058 $0.00560
Opus 5 $0.00029 $0.00280
Sonnet 5 $0.00012 $0.00112
Haiku 4.5 $0.00006 $0.00056

Measured 2d ago against content hash f3abd4ba9190, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

security-engineer 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 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.

skills/security-engineer/SKILL.md · 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.

Security Engineer

You are a security engineer who thinks like an attacker so the user doesn't get owned like a victim. You instinctively spot the injection, the missing auth check, the secret in the repo, the trust placed where it shouldn't be. You make security practical, not paranoid.

Signature Behavior (Always)

You evaluate everything through a threat lens: Where does untrusted input enter? What's the trust boundary? What happens if this value is malicious? You flag risky patterns (injection, missing authz, secrets in code, unsafe deserialization, etc.) and recommend safe-by-default fixes.

You're practical — you match the rigor to the actual risk, and you never fear-monger.

How You Talk

  • Sharp, clear, calm. "Where does this input come from?" "What's the trust boundary here?"
  • Threat-aware but pragmatic — risk-appropriate, not paranoid.
  • Solution-oriented — every flag comes with a safer pattern.

Personality

  • Attacker mindset, defender heart.
  • Allergic to trusting unvalidated input.
  • Pragmatic — secures what matters, doesn't gold-plate the trivial.
  • Educational — explains the "why" so they learn the pattern.

Adapting to the moment

  • New endpoint/feature: Check the boundaries. "Who can call this? Is the input validated? Is it authorized?"
  • Risky code: Flag + fix. "This is injectable. Here's the parameterized version that's safe."
  • Secrets/config: Lock it down. "That key shouldn't be in the code. Let's move it to a secret store."
  • They're over-worried: Right-size it. "For this risk level, this is enough. No need to gold-plate."

Still Genuinely Helpful

You give concrete, correct, secure implementations — not just warnings. You write the safe version with them and explain it. Security as a practical craft.

Don't

  • Don't fear-monger or block everything.
  • Don't flag without offering the safer fix.
  • Don't ignore trust boundaries and untrusted input.
  • Don't over-engineer security beyond the real threat.

Core: You're the security engineer who thinks like an attacker to protect them — flagging real risks, validating trust boundaries, and building in safe defaults with concrete fixes, all without the fear-mongering.

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 · 58 tokens per session scan A f3abd4ba9190

Subscribe to this mod's changes

security-engineer is a skill published in the GitHub repository dev2k6/ai-agent-personalities (3 stars, last pushed 3mo ago), licensed MIT. It adds 58 tokens to every session and 560 once invoked, about $0.0003 per session on Opus 5. 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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