PrepOS

A macOS-style desktop cockpit for tech interview prep, built with Electron + React + TypeScript.

PrepOS looks like a mini operating system inside one Electron window: desktop, dock, draggable / resizable windows, Launchpad and Spotlight. Every interview prep platform (LeetCode, HackerRank, DevTools Tech, etc.) is an "app" in the dock. The signature feature is Capture → AI: screenshot any region of your screen and ask GPT-4o / Claude about it directly inside the app.

Download

Grab the latest build for your OS from the releases page or visit prep-os.queztlabs.tech for an OS-aware download experience.

OS	File
macOS	PrepOS-x.y.z-arm64.dmg (Apple Silicon) / PrepOS-x.y.z-x64.dmg (Intel)
Windows	PrepOS-Setup-x.y.z.exe (NSIS installer)
Linux	PrepOS-x.y.z.AppImage / prep-os_x.y.z_amd64.deb

First launch on an unsigned build triggers an OS warning — see bypass instructions below.

Features

• macOS-like shell — Dock with magnification, draggable / resizable windows, traffic lights, Launchpad, Menubar.
• Capture → AI — global shortcut Cmd+Shift+A captures a screen region and pipes it into the AI Chat app with GPT-4o vision / Claude 3.5 Sonnet vision.
• Plugin system — built-in platforms (DevTools Tech, LeetCode, HackerRank, GitHub, Excalidraw, YouTube) + user-added custom web apps.
• Native apps — AI Chat, Markdown Notes, Monaco code Playground, Feed reader, Settings.
• Focus mode — start a timed session on any plugin. Opt into Hard focus to block Cmd+Q until the session ends.
• Daily tip — curated interview tip on the desktop, rotating daily.
• Tech feed — a daily.dev-style reader pulling Hacker News, Dev.to, GitHub Trending, freeCodeCamp, ByteByteGo, plus India placement-prep staples (GeeksforGeeks, Striver / takeUforward via YouTube, NeetCode via YouTube, InterviewBit). Grouped by Interview / Career, Frontend, Backend, System Design, and General.
• Spotlight — Cmd+K fuzzy command palette for apps and actions.
• Secure storage — API keys encrypted via Electron safeStorage (macOS Keychain backed).

Quickstart

Prerequisites: Node 18+ (tested with 22/23), macOS / Windows / Linux.

npm install
npm run dev

The dev shell opens an Electron window with HMR-enabled React renderer.

Add your OpenAI or Anthropic API key inside Settings (Cmd+, or from the Launchpad / Dock) to activate the AI chat.

Build a distributable

npm run dist:mac     # DMG + zip for arm64 + x64
npm run dist:win     # NSIS installer
npm run dist:linux   # AppImage + deb

For signing / notarization on macOS, set APPLE_ID, APPLE_ID_PASSWORD, and APPLE_TEAM_ID env vars and flip notarize: true in electron-builder.yml.

First-launch on an unsigned build

Because PrepOS is not yet signed / notarized, the OS will warn end-users on first launch. Share one of these workarounds with your early testers:

macOS (Gatekeeper)

"PrepOS can't be opened because Apple cannot check it for malicious software." or "This item is on the disk image 'PrepOS-x.y.z-arm64.dmg'. Chrome downloaded this disk image today…"

1. Don't run PrepOS from the DMG. Open the DMG and drag PrepOS.app onto the /Applications shortcut next to it, then eject the DMG. Running straight from the mounted image causes the warning to repeat every launch.

2. Double-click /Applications/PrepOS.app. If macOS asks "Are you sure you want to open it?" click Open — one-time confirmation, then you're in.

3. If macOS blocks it outright (common on macOS 15 Sequoia+, where Apple removed the Open Anyway button for unsigned apps), strip the quarantine flag from Terminal:

   xattr -dr com.apple.quarantine /Applications/PrepOS.app

   Works on every macOS version. Double-click afterwards — no more warnings.

Older macOS only: the GUI workaround also works — right-click PrepOS.app → Open → confirm in the dialog, or System Settings → Privacy & Security → Open Anyway. On Sequoia these are hidden; use the Terminal fix above.

Windows (SmartScreen)

"Windows protected your PC."

1. Click More info in the blue dialog → Run anyway.
2. If SmartScreen silently blocks, right-click the installer → Properties → check Unblock at the bottom → OK, then run again.

Linux (AppImage)

1. Right-click the .AppImage → Properties → Permissions → Allow executing as program (or chmod +x PrepOS-*.AppImage).
2. Run it; on the first launch it integrates itself into your launcher.

Architecture

src/
  main/       Electron main process (window, globalShortcut, IPC)
    index.ts        createMainWindow + shortcuts
    preload.ts      contextBridge API surface exposed to renderer
    capture.ts      region screenshot overlay + desktopCapturer
    ai-gateway.ts   OpenAI / Anthropic HTTP clients
    plugins.ts      built-in plugins + user-added plugin CRUD
    store.ts        electron-store wrapper (+ safeStorage for keys)
    ipc.ts          IPC handler registration
  renderer/   React app (the "OS" UI)
    App.tsx
    components/     Desktop, Menubar, Dock, Window, Launchpad, Spotlight
    apps/           AIChat, Notes, Playground, Settings, WebviewHost, AppRouter
    store/          Zustand stores: windows, plugins, shell
  shared/     Shared TypeScript types for main ↔ renderer

Adding your own "app"

1. Click the Launchpad icon in the dock.
2. Click + Add, give it a name, URL and an emoji/icon.
3. It appears in the Launchpad and Dock. Clicking launches the URL inside a sandboxed <webview> with persistent cookies (so logins survive).

Or programmatically edit src/main/plugins.ts to add to BUILT_IN_PLUGINS.

Security

• contextIsolation: true, no nodeIntegration, API surface limited through src/main/preload.ts.
• API keys encrypted via safeStorage (macOS Keychain / Windows DPAPI / libsecret).
• Every webview gets an isolated partition: persist:<plugin-id> so cookies and localStorage are scoped per app.

Documentation

Full documentation lives in docs/. If you're new:

• New developer? Start with docs/getting-started.md, then docs/architecture.md.
• AI coding agent? Read AGENTS.md first.
• Extending the app? See docs/plugins.md and docs/ipc-reference.md.
• Packaging a release? See docs/build-and-release.md.
• Stuck? Check docs/troubleshooting.md.

Deep dives:

Topic	File
High-level architecture + diagrams	docs/architecture.md
Main process file-by-file	docs/main-process.md
Renderer (UI components, stores, styling)	docs/renderer.md
Plugin system + manifest schema	docs/plugins.md
Capture → AI flow end-to-end	docs/capture-and-ai.md
IPC channel catalog	docs/ipc-reference.md
Packaging + signing	docs/build-and-release.md
Debugging + known gotchas	docs/troubleshooting.md

Status

MVP covers Phases 0 → 5 of the plan. See the in-repo plan for the roadmap. Release notes live in CHANGELOG.md.

Contributing

PRs and issues welcome — anything from bug reports to new built-in plugins to UI polish. Before opening a PR:

• Run npm run check (typecheck + lint + format) and make sure it passes.
• For bigger features, open a discussion or draft PR first so we can align on direction.

For security issues, please don't open a public issue — see SECURITY.md for the private reporting process.

Privacy

PrepOS runs entirely on your machine — no telemetry, no analytics, no servers. The only network traffic is to AI providers you configure (OpenAI / Anthropic), public RSS feeds you subscribe to, and a once-per-boot GitHub release check. Full details in PRIVACY.md.

License

MIT © 2026 Shivam Jha.