Overview

Happy is an open‑source application that lets you work with several large‑language‑model providers from a single interface. It runs on desktop operating systems and also offers a mobile client, so you can continue a session on a phone after leaving your desk. The tool is positioned as a “use” that reuses the API subscriptions you already have for Claude, Codex, Grok, Gemini and other models.

The core idea is to let you pick the model that best fits each task without needing separate accounts or billing for each service. After signing in with the credentials you already use for Claude, Codex and Grok, and with Google for Gemini, Happy connects to those APIs and presents them in one place. You can start a Claude or Codex session directly from a terminal command (`happy claude` or `happy codex`) or launch the graphical desktop app, and the same project files are available on the mobile app, with end‑to‑end encryption protecting the data that moves between devices.

Happy is aimed at developers and teams who already have paid subscriptions to multiple model providers and want a unified workflow. Because the software is MIT‑licensed, you can run it on your own hardware, inspect the source code, fork it, or build a custom version. The project also supports a multiplayer mode: you can deploy a team server, let each member sign in with their own credentials, and share projects and sessions across the group. The CLI remains available for users who prefer a terminal‑only experience, and the desktop client can be installed via Homebrew on macOS (Apple Silicon or Intel) or downloaded for Windows and Linux.

Key features

Access to Claude, Codex, Grok, Gemini and additional models from a single app
Reuse of existing API subscriptions; no additional billing required
Open‑source MIT license with ability to run locally on your hardware
End‑to‑end encrypted synchronization between desktop and mobile sessions
Multiplayer team server for shared projects and individual sign‑ins
Terminal‑first workflow with commands like `happy claude` and `happy codex`

Details

Pricing: Free
Category: Code

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Pros and cons

Pros

Consolidates multiple model providers, reducing context switching
Free and open source, allowing code review and custom builds
Encryption ensures session data is protected across devices
Supports both GUI and CLI usage, fitting different developer preferences
Multiplayer server enables collaborative work without separate accounts

Cons

Requires existing subscriptions to the supported models; no free model access provided
Pricing information for the tool itself is not published, though it is described as free
Installation instructions focus on macOS Homebrew; Windows and Linux steps are less detailed.