Security review

/security-review

When to use

• Before committing changes that touch authentication, authorization, cryptography, user-input handling, file/path operations, request handling (routes/middleware/templates), or anything that reads/writes secrets.
• When the security-nudge Stop hook prints a one-liner suggestion.
• Whenever you want a second pair of eyes on a diff before pushing — Sonnet running on isolated context will catch things Opus inline missed about a third of the time in informal testing.

What it does NOT replace

• Static analysis (Semgrep, CodeQL, Bandit) — those have rule sets built by full-time security teams. Run them separately in CI.
• Dependency vulnerability scanning (npm audit, pip-audit, cargo audit, GitHub Dependabot). The skill flags suspicious package additions but does not check CVE feeds.
• A real pentest. This is a diff review by a model, not an attacker exercising your live system.

How it runs

sequenceDiagram
    participant U as User
    participant M as Main session (Opus)
    participant S as security-reviewer (Sonnet)

    U->>M: /security-review
    M->>M: git diff --cached
    M->>S: Task: review this diff for OWASP Top 10 patterns
    S->>S: Read diff + surrounding context
    S->>S: Pattern-walk + tier findings
    S-->>M: Markdown report (Critical / Important / Nice / OOS)
    M->>U: Relay report verbatim + offer "fix all Critical, fix one, ignore"

1. Main session reads the staged diff (git diff --cached; falls back to git diff if nothing staged).
2. If diff is empty, report "no changes to review" and stop.
3. Delegate to security-reviewer subagent (Sonnet, read-only). Pass:
   • The full diff
   • The list of changed files
   • The current branch and git log --oneline -5 for context
4. Receive the structured Markdown report.
5. Relay the report verbatim to the user. Do not paraphrase, summarize, or pre-emptively fix anything.
6. Ask the user: "Fix all Critical findings, address one specific finding, or commit as-is and address later?"

Hard rules for the main session

• Never modify code from this skill's invocation. This skill is purely audit + relay. If the user says "yes, fix the Critical findings," that's a separate main-session step — exit this skill first.
• Never silently downgrade tiers. If the subagent reported a finding as Critical, surface it as Critical. The user decides priority.
• Always relay the full report. Do not trim the "Out of scope" section — it tells the user what wasn't covered.

Why a subagent, not inline

The benchmark series in bench/archive-token-savings-thesis/ showed that subagent dispatch is usually a cost loss vs Opus inline. We accept that cost here because:

1. Deterministic output schema. Sonnet returns Critical/Important/Nice tiers every invocation; Opus inline produces prose of varying shape. Downstream tooling (e.g., a CI gate that only blocks on Critical) can parse the structured output.
2. Context isolation. A read-only subagent cannot accidentally "fix" findings mid-review — eliminating the class of bugs where the reviewer becomes the implementer.
3. Cost-not-amortized work. Security review is naturally bounded (one diff in, one report out). It doesn't benefit from main-session warm cache the way iterative coding does.

If you want to skip the dispatch and have Opus inline read the diff and emit a report freeform, just type "review this diff for security issues" without invoking the skill — the model will do it. The skill exists for the cases above (schema, isolation, structured-output workflows).

Codex parity

The same skill ships in Codex via scripts/install-codex.sh. The subagent is at .codex/agents/security-reviewer.toml (generated from agents/security-reviewer.md by scripts/gen-codex-agents.py).

Tunables

• The security-nudge Stop hook fires when net-new code crosses 80 LOC and at least one changed file matches a sensitive-path pattern (*auth*, *login*, routes/, api/, *crypto*, *payment*, templates/, *.env*, …). Override threshold via env var CLAUDE_LEVERAGE_SECURITY_NUDGE_LOC.