What is preview-diff?

A tool for viewing Git changes in a readable web-style layout. Git is the version-control system that records edits to files.

Use it to preview changes in the current project or compare branches before reviewing or committing code. It also shows tracked, staged, and untracked files.

It makes it easier to inspect what changed without reading raw diff text. You can find files, compare versions side by side or line by line, and see added and removed lines.

preview-diff — Skill for Claude Code and Codex by veelenga: A tool for viewing Git changes in a readable…

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/veelenga/preview-skills/preview-diff

Any agent

npx skills add veelenga/preview-skills --skill preview-diff

Clone the repo

git clone --depth 1 https://github.com/veelenga/preview-skills

Made for: Claude Code, Codex.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/veelenga/preview-skills/preview-diff.svg)](https://agentmods.dev/skills/veelenga/preview-skills/preview-diff)

Your own site

<a href="https://agentmods.dev/skills/veelenga/preview-skills/preview-diff"><img src="https://agentmods.dev/badge/skills/veelenga/preview-skills/preview-diff.svg" alt="Measured on agentmods" height="20"></a>

Per session 16 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 407 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.

Model	Per session	Once invoked
Fable 5	$0.00016	$0.00407
Opus 5	$0.00008	$0.00204
Sonnet 5	$0.00003	$0.00081
Haiku 4.5	$0.00002	$0.00041

Measured 4d ago against content hash 1d091839f271, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

preview-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 4d ago.

The scan reads SKILL.md. This mod also ships 8 executable files (config.sh, lib/browser-utils.sh, lib/content-utils.sh, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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/preview-diff/SKILL.md · 60 lines

What it actually says

Git Diff Preview Tool

Internal tool for previewing git changes with GitHub-style formatting. Accessed via /preview-diff command.

Features

Visual Design

Beautiful gradient header with clear stats summary
GitHub-style formatting using diff2html library
Modern UI with rounded corners and smooth transitions
Enhanced readability with optimized fonts and spacing

Functionality

Accordion-style files: Click headers to expand/collapse
Smart defaults: First file expanded, others collapsed
Expand/Collapse All button for quick control
Real-time search: Filter files by name
View switching: Toggle between unified and split view
Unified view (default): Traditional line-by-line diff
Split view: Side-by-side comparison
Change statistics: Files changed, additions, deletions
Line numbers and syntax highlighting
View persistence across sessions
Shows all changes: tracked, staged, and untracked files

Agent Usage

When the user asks to preview a diff, DO NOT build HTML manually. Use the Bash tool to execute this skill's run.sh script:

# Preview current changes
git diff HEAD | ./run.sh

# Preview specific branch comparison
git diff main..feature-branch | ./run.sh

The script handles all HTML generation and automatically opens the result in the browser. Do NOT open the file manually to avoid duplicate tabs.

Options

The script works with sensible defaults but supports these flags for flexibility:

-o, --output PATH - Custom output path
--no-browser - Skip browser, output file path only

Technology

diff2html: GitHub-style diff rendering
git diff: Unified diff format
JavaScript/CSS: Browser-based rendering

Files

What ships with it

10 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.

4d ago First seen · 60 lines · 16 tokens per session scan A 1d091839f271

Subscribe to this mod's changes

preview-diff is a skill published in the GitHub repository veelenga/preview-skills (8 stars, last pushed 24d ago), licensed MIT. It adds 16 tokens to every session and 407 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 2026-08-31.

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