difftastic

difftastic is a skill for Claude Code from moabualruz/fulcrum. It costs 72 tokens per session (222 once invoked), scanned A, a copy of bat, MIT.

A structural diff tool that compares source code based on its syntax rather than only its text. A diff shows what changed between two files or Git revisions.

In plain words
What is it for?
Use it to compare Rust, TypeScript, Python, Go, and other supported source files or Git revisions with syntax-aware output.
Why use it?
It reduces noise from formatting, whitespace, brace movement, and similar changes that do not alter the code's structure. This makes meaningful code changes easier to inspect.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the fulcrum plugin — 32 skills shipped together

Good fit Use it to compare Rust, TypeScript, Python, Go, and other supported source files or Git revisions with syntax-aware output.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/moabualruz/fulcrum/difftastic
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 moabualruz/fulcrum --skill difftastic
Clone the repo
git clone --depth 1 https://github.com/moabualruz/fulcrum

Made for: Claude Code.

Or install fulcrum, the plugin that ships this one along with the rest of its 32 skills.

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 difftastic

README.md
[![agentmods](https://agentmods.dev/badge/skills/moabualruz/fulcrum/difftastic/github.svg)](https://agentmods.dev/skills/moabualruz/fulcrum/difftastic)
Your own site
<a href="https://agentmods.dev/skills/moabualruz/fulcrum/difftastic"><img src="https://agentmods.dev/badge/skills/moabualruz/fulcrum/difftastic/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 difftastic

Your own site · 80×15
<a href="https://agentmods.dev/skills/moabualruz/fulcrum/difftastic"><img src="https://agentmods.dev/badge/skills/moabualruz/fulcrum/difftastic.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 72 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 222 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 86% 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 $0.00072 $0.00222
Opus 5 $0.00036 $0.00111
Sonnet 5 $0.00014 $0.00044
Haiku 4.5 $0.00007 $0.00022

Measured 9d ago against content hash f700a4fb6b4d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

difftastic 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 9d 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

86% identical to bat — 6 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.

plugins/fulcrum/skills/difftastic/SKILL.md · 28 lines

What it actually says

difftastic

When to use

See references/when-to-use.md. Load only when this section is needed.

Invocation

See references/invocation.md. Load only when this section is needed.

Patterns

See references/patterns.md. Load only when this section is needed.

Anti-patterns

See references/anti-patterns.md. Load only when this section is needed.

Cross-refs

See references/cross-refs.md. Load only when this section is needed.

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. 9d ago First seen · 28 lines · 72 tokens per session scan A f700a4fb6b4d

Subscribe to this mod's changes

difftastic is a skill published in the GitHub repository moabualruz/fulcrum (3 stars, last pushed 2mo ago), licensed MIT. It adds 72 tokens to every session and 222 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. It is 86% identical to bat, differing in 6 lines, and is treated as a copy.