differential-review

differential-review is a skill for Claude Code from msradam/theodosia. It costs 61 tokens per session (1,664 once invoked), scanned A, a copy of differential-review, Apache-2.0.

A security review of the differences between code versions, such as a pull request, commit, or Git diff. It examines whether a change introduces security problems.

In plain words
What is it for?
Use it to review code changes involving authentication, encryption, money or value transfers, external calls, refactors, and missing tests, then produce a Markdown report.
Why use it?
It records evidence, affected code, attack scenarios, test coverage, and uncertainty so security risks are not missed or forgotten.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Good fit Use it to review code changes involving authentication, encryption, money or value transfers, external calls, refactors, and missing tests, then produce a Markdown report.

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Install with agentmods
npx agentmods add skills/msradam/theodosia/differential-review
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.

Any agent
npx skills add msradam/theodosia --skill differential-review
Clone the repo
git clone --depth 1 https://github.com/msradam/theodosia

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 differential-review

README.md
[![agentmods](https://agentmods.dev/badge/skills/msradam/theodosia/differential-review/github.svg)](https://agentmods.dev/skills/msradam/theodosia/differential-review)
Your own site
<a href="https://agentmods.dev/skills/msradam/theodosia/differential-review"><img src="https://agentmods.dev/badge/skills/msradam/theodosia/differential-review/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for differential-review

Your own site · 80×15
<a href="https://agentmods.dev/skills/msradam/theodosia/differential-review"><img src="https://agentmods.dev/badge/skills/msradam/theodosia/differential-review.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,664 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 92% copy Near-identical to another mod 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 $0.00061 $0.01664
Opus 5 $0.00030 $0.00832
Sonnet 5 $0.00012 $0.00333
Haiku 4.5 $0.00006 $0.00166

Measured 10d ago against content hash 1499d68ed446, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

differential-review 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 10d 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.

Origin

This is a copy

92% identical to differential-review — 25 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

examples/skills/differential-review/SKILL.md · 229 lines

How it starts

The opening of the file, as written. The whole thing — 229 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Differential Security Review

Security-focused code review for PRs, commits, and diffs.

Core Principles

  1. Risk-First: Focus on auth, crypto, value transfer, external calls
  2. Evidence-Based: Every finding backed by git history, line numbers, attack scenarios
  3. Adaptive: Scale to codebase size (SMALL/MEDIUM/LARGE)
  4. Honest: Explicitly state coverage limits and confidence level
  5. Output-Driven: Always generate comprehensive markdown report file

Rationalizations (Do Not Skip)

Rationalization Why It's Wrong Required Action
"Small PR, quick review" Heartbleed was 2 lines Classify by RISK, not size
"I know this codebase" Familiarity breeds blind spots Build explicit baseline context
"Git history takes too long" History reveals regressions Never skip Phase 1
"Blast radius is obvious" You'll miss transitive callers Calculate quantitatively
"No tests = not my problem" Missing tests = elevated risk rating Flag in report, elevate severity
"Just a refactor, no security impact" Refactors break invariants Analyze as HIGH until proven LOW
"I'll explain verbally" No artifact = findings lost Always write report

Quick Reference

Codebase Size Strategy

Codebase Size Strategy Approach
SMALL (<20 files) DEEP Read all deps, full git blame
MEDIUM (20-200) FOCUSED 1-hop deps, priority files
LARGE (200+) SURGICAL Critical paths only

Risk Level Triggers

Risk Level Triggers
HIGH Auth, crypto, external calls, value transfer, validation removal
MEDIUM Business logic, state changes, new public APIs
LOW Comments, tests, UI, logging

Workflow Overview

Pre-Analysis → Phase 0: Triage → Phase 1: Code Analysis → Phase 2: Test Coverage
    ↓              ↓                    ↓                        ↓
Phase 3: Blast Radius → Phase 4: Deep Context → Phase 5: Adversarial → Phase 6: Report

Read the full file on GitHub · 229 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 10d ago First seen · 229 lines · 61 tokens per session scan A 1499d68ed446

Subscribe to this mod's changes

differential-review is a skill published in the GitHub repository msradam/theodosia (15 stars, last pushed 3d ago), licensed Apache-2.0. It adds 61 tokens to every session and 1,664 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 92% identical to differential-review, differing in 25 lines, and is treated as a copy.