Radius

A minimal, fast desktop email client for Gmail. Built with Electrobun (Bun + native web views).

What it does

• Connects to Gmail via OAuth (read-only — never sends, deletes, or modifies emails)
• Syncs your inbox locally for instant access
• Incremental catch-up on every launch — fetches new emails automatically
• Clean reader view with smooth sidebar transitions

Installation

Homebrew (recommended)

brew tap DeepanshuMishraa/radius https://github.com/DeepanshuMishraa/radius
brew install --cask radius

If the name is ambiguous, use the fully qualified name:

brew install --cask DeepanshuMishraa/radius/radius

Manual

Download the latest release for your platform from the releases page.

Requirements

• macOS
• Bun
• A Google Cloud project with the Gmail API enabled

Running

# Install dependencies
bun install

# Dev with HMR (recommended)
bun run dev:hmr

# Dev without HMR
bun run dev

# Production build
bun run build:canary

Security

• The Google OAuth Client ID and Client Secret are hardcoded in src/bun/auth.ts.
• User tokens live in the system keychain (macOS Keychain, Windows Credential Manager, or Linux Secret Service).
• PKCE is used for the OAuth authorization flow.

Why the Client Secret is shipped

Google's Desktop app OAuth client type issues a client_secret, but for installed desktop applications this is effectively a pseudo-secret. The OAuth 2.0 spec for public native clients (RFC 8252) expects that installed apps cannot keep secrets confidential. Google's Desktop client type is designed with this reality in mind — the secret is meant to be embedded in the binary. PKCE (the code_verifier) is what actually secures the flow, not the client secret.

This is the same approach used by well-known open-source desktop apps (e.g., Thunderbird's Gmail integration). For a desktop OSS app, shipping the secret and acknowledging it in the README is the honest and standard approach.

Project structure

src/
  bun/          # Main process — auth, sync, database, RPC
  mainview/     # Renderer — React UI

Tech stack

• Electrobun (Bun runtime + native web views)
• React + Tailwind CSS
• SQLite (local email storage)
• Gmail API