diff4 - SKILL.md Agent Skill

name: diff4 description: Preview git diffs and files using the diff4 CLI. Use when the user wants to see code changes, review files content securely via diff4 metadata: author: diff4 version: "0.1.0"

diff4 - Encrypted Diff & File Sharing

diff4 encrypts diffs and files client-side (AES-256-GCM) before uploading. The server never sees plaintext. Recipients need the passphrase to decrypt.

Prerequisites

diff4 must be installed and available on PATH. Use npm i -g @diff4/cli to install.
A passphrase must be configured (see setup below)

Commands

Share the latest commit diff

diff4 git-latest

Runs git diff HEAD~1, encrypts the result, and uploads. Use when the user says "preview my last commit" or "send the latest diff."

Share staged changes

diff4 git-staged

Runs git diff --staged, encrypts, and uploads. Use when the user says "preview my staged changes" or "send what's about to be committed."

Share arbitrary files

diff4 files path/to/file1.ts path/to/file2.ts

Reads each file (UTF-8 text only), bundles them as JSON, encrypts, and uploads. Supports any number of paths (relative or absolute).

Key management

diff4 key-gen [key] - Generate or set the encryption passphrase
diff4 key-get - Print the current passphrase

Options

All upload commands (git-latest, git-staged, files) accept:

Flag	Description
`-s, --server <url>`	Override the diff4 server URL. Default: `https://diff4.com` (or `DIFF4_SERVER` env var)
`-p, --passphrase <key>`	Override the passphrase for this command only. Default: `DIFF4_PASSPHRASE` env var

Gotchas

Empty diffs fail gracefully. git-latest and git-staged will error if there is nothing to share.
Binary files are not supported. diff4 files reads files as UTF-8 text.
Server is configurable. Self-hosted instances can be set via DIFF4_SERVER env var or -s flag.
The passphrase must be shared out-of-band. diff4 only encrypts — recipients need the same passphrase to decrypt.
key-gen updates existing keys. If DIFF4_PASSPHRASE already exists in the shell config, key-gen replaces it in-place.

Typical workflow

User asks to see a diff or files
Verify setup: run diff4 key-get (if it fails, run diff4 key-gen and tell user to source their rc file)
Run the appropriate command (git-latest, git-staged, or files <paths>)
Return the URL from the response to the user
Remind the user that recipients need the passphrase to decrypt