Apargon

Apargon is a desktop app for macOS, Linux and Windows that runs papps.

A papp is a single .papp file: an HTML file with extra <meta> tags. It works like a desktop app, without the setup a desktop app needs: no installer, no server, no build step. You double-click it, and Apargon opens it in a sandboxed window.

The sandbox blocks everything the tags don't allow, and a popup shows what they ask for before the page runs.

A coding agent can write a papp from one prompt.

Install

On macOS or Ubuntu 24.04, with the papp skill for agents (sh -s -- --no-skill without it):

curl -fsSL https://apargon.com/install.sh | sh

install.sh checks the app's notarization on macOS, and the .deb against the release's SHA256SUMS on Linux, before it installs it. Or download from the latest release: the .dmg for macOS (arm64 or x64), the .deb for Ubuntu 24.04, the .exe for Windows (x64 or arm64).

The Windows installer is not signed, so Windows warns before it runs. Check it against the release's SHA256SUMS first.

Or with Homebrew on macOS:

brew trust --cask orcaryn/tap/apargon
brew install --cask orcaryn/tap/apargon

Then double-click a .papp, or run open page.papp (macOS) or apargon page.papp (Linux).

The first time it opens, Apargon offers to install the papp skill, so coding agents can build apps for it (see Build with an agent).

Once a day Apargon asks GitHub for a new version. Permissions → Check for Updates Automatically turns it off; then watch the repository's releases for security fixes.

Meta tags

With no tags, a page sees its own folder and nothing else. It asks for more in its <head>, one value per tag:

<meta name="papp-read"     content="~/logs">                   <!-- see a folder -->
<meta name="papp-write"    content="./notes/*.md">             <!-- change files -->
<meta name="papp-net"      content="api.example.com:443">      <!-- one server -->
<meta name="papp-open"     content="x.com">                    <!-- its links open without asking -->
<meta name="papp-run"      content="git">                      <!-- one program -->
<meta name="papp-env"      content="AWS_PROFILE">              <!-- one variable for it -->
<meta name="papp-socket"   content="/var/run/docker.sock">     <!-- one socket -->
<meta name="papp-use"      content="notifications">            <!-- or clipboard, location, sound, camera, microphone, screen -->
<meta name="papp-shortcut" content="CommandOrControl+Shift+N"> <!-- a key that works in every app -->
<meta name="papp-node"     content="full">                     <!-- full Node -->

Write each tag as the browser reads it: name and content quoted, with no spaces around the =.

A popup lists what the tags allow before the page runs. A red line is a way to send data somewhere the tags do not name. When a page could send your data out (a red line, a program, a socket, or a server plus files it sees), the popup says how and asks you to tick "I trust this page". Permissions → Approved Pages takes an approval back.

A page keeps its storage (localStorage, IndexedDB) when you move or rename the file, as long as its content is the same as when it was last open. A copy starts empty.

With no tag, a page can still open a link in your browser, and a file (image, video, audio, PDF, text) or a folder in its app. A link asks first, with the address shown, unless the page names the site with papp-open.

A papp-node page runs as you, with only the network blocked: open one only if you trust it. SECURITY.md lists what Apargon enforces and what it does not.

Windows

On Windows, a few things work differently:

• Programs can leak. A page's programs, and a papp-node page, can send any file they see to the internet. Windows lets them. So you must tick "I trust this page" before such a page opens.
• No sockets, no localhost. A page with papp-socket or papp-net to localhost does not open.
• Only .exe and .com programs. papp-run does not take .bat or .cmd files.
• Programs see less. Only the page's folders, their own folder, and folders every app can read, like C:\Windows and Program Files.
• papp-node writes less. Only in the folders inside your home folder, and in the page's own folder. Never in Apargon's data or on other drives.

Build with an agent

Give it skills/papp/SKILL.md. Apargon installs it to ~/.claude/skills/papp/ and ~/.agents/skills/papp/ if you say yes: on its first run, each time you open it without a page until the skill is there, and from Help → Install the papp Skill for Agents…. Without Apargon:

for dir in ~/.claude/skills/papp ~/.agents/skills/papp; do
  mkdir -p "$dir"
  curl -fsSL https://apargon.com/.well-known/agent-skills/papp/SKILL.md -o "$dir/SKILL.md"
done

Then ask for an app: "Make me a papp that lists the Markdown notes in ~/notes and lets me edit them."