diff

A command that compares security scan results between two Git versions, such as two commits, branches, or releases. It shows vulnerabilities that appeared, disappeared, or changed severity.

In plain words
What is it for?
Checking whether a branch introduced security regressions, confirming fixes, and producing Markdown or JSON comparison results.
Why use it?
It makes security changes between versions visible instead of requiring developers to compare reports manually.

Command

Part of the vuln-scout plugin — 32 skills, 15 commands, 9 agents shipped together

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 commands/allsmog/vuln-scout/diff
Clone the repo
git clone --depth 1 https://github.com/allsmog/vuln-scout

Or install vuln-scout, the plugin that ships this one along with the rest of its 32 skills, 15 commands, 9 agents.

Per session 21 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 461 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 $0.00021 $0.00461
Opus 5 $0.00010 $0.00230
Sonnet 5 $0.00004 $0.00092
Haiku 4.5 $0.00002 $0.00046

Measured 3d ago against content hash 385680feb629, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

diff 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 3d 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.

vuln-scout/commands/diff.md · 61 lines

What it actually says

Differential Security Analysis

Compare security findings between two git refs. Shows new vulnerabilities introduced, vulnerabilities fixed, and severity changes.

Usage

/vuln-scout:diff HEAD~5
/vuln-scout:diff v1.0.0 v2.0.0
/vuln-scout:diff main feature/auth --fail-on-regression

Flags

Flag Effect
base-ref Git ref to compare against (required)
head-ref Git ref to compare (default: HEAD)
--tools Scanning tools to use (default: semgrep)
--format Output format: md or json
--fail-on-regression Exit 2 if regression score > 0 (more new findings than fixed)

Workflow

Step 1: Scan baseline

python3 "${CLAUDE_PLUGIN_ROOT}/scripts/run_diff.py" \
  --base <base-ref> \
  --head <head-ref> \
  --tools <tools> \
  --project-root .

The script handles git checkout, scanning both refs, and computing the diff.

Step 2: Display results

Show the diff report:

  • New findings: vulnerabilities introduced since the baseline
  • Fixed findings: vulnerabilities that no longer appear
  • Changed findings: same location but different severity/verdict
  • Regression score: positive = worse, negative = better
  • New/removed endpoints: attack surface changes

Step 3: Exit code

  • 0: no regression (fixed >= new, or --fail-on-regression not set)
  • 2: regression detected (with --fail-on-regression)
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. 3d ago First seen · 61 lines · 21 tokens per session scan A 385680feb629

Subscribe to this mod's changes

diff is a command published in the GitHub repository allsmog/vuln-scout (24 stars, last pushed 2mo ago), licensed MIT. It adds 21 tokens to every session and 461 once invoked, about $0.0001 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 2026-08-30.