Rex — select text, tap Ctrl, ask

The quick answer, without losing your thread.

You're deep in a long AI chat, a dense article, or someone else's code — and one line stops you. Opening a new chat means losing your focus.

Rex (your assistant): select the thing, tap Ctrl, ask — the answer lands right where you are.

Open source, your own API key, straight to your provider. No server, no account.

Install

From the terminal (fastest)

Paste one line — it downloads the latest release, installs it, and starts Rex. Close the terminal; Rex keeps running in the tray.

macOS / Linux

curl -fsSL https://raw.githubusercontent.com/MoustafaTech/rex/main/install.sh | sh

Windows (PowerShell)

irm https://raw.githubusercontent.com/MoustafaTech/rex/main/install.ps1 | iex

On macOS the script also clears the unsigned-app block, so there's no Gatekeeper dance — just grant Accessibility when the settings pane opens (one time), then quit and reopen Rex from the menu bar.

Manual download

⬇ Download the latest release, then follow your OS:

🍎 macOS

1. Download Rex-…-mac-arm64.dmg (Apple Silicon) or Rex-…-mac-x64.dmg (Intel) and drag Rex to Applications.
2. First open: double-clicking shows a blocked dialog (Rex is unsigned) — click Done, then go to System Settings → Privacy & Security, scroll down, click Open Anyway next to Rex and confirm. (macOS 14 or older: right-click the app → Open → Open.)
3. Grant Accessibility when asked (System Settings → Privacy & Security → Accessibility → enable Rex) — this lets Rex hear the Ctrl tap.
4. macOS will also ask to let Rex control System Events — click OK (that's how Rex reads your selection). Then quit and reopen Rex once.
5. Rex lives in the menu bar (no Dock icon).

🪟 Windows

1. Download and run Rex-…-win-x64.exe.
2. SmartScreen will warn (unsigned) — click More info → Run anyway.
3. Rex lives in the system tray, near the clock.

🐧 Linux

# AppImage (any distro)
chmod +x Rex-…-linux-x86_64.AppImage && ./Rex-…-linux-x86_64.AppImage
# or Debian/Ubuntu
sudo dpkg -i Rex-…-linux-amd64.deb && rex

Install the clipboard helpers — they make capture direct and safe: sudo apt install xclip xdotool (X11) or sudo apt install wl-clipboard (Wayland). Rex lives in the system tray.

Add your API key

Tray/menu-bar icon → Settings → pick a provider, paste a key, set a model:

Provider	Example models
Anthropic	claude-sonnet-5, claude-haiku-4-5-20251001
OpenAI	gpt-5.2, gpt-5-mini
Google	gemini-2.5-flash, gemini-2.5-pro
Mistral	mistral-small-latest, mistral-large-latest
DeepSeek	deepseek-chat, deepseek-reasoner
xAI	grok-4, grok-3-mini
Groq	llama-3.3-70b-versatile
OpenRouter	anthropic/claude-sonnet-5 — any model on the router
Ollama (local)	llama3.3, qwen3 — no API key needed
OpenAI-compatible	anything with a base URL: LM Studio, vLLM, llama.cpp…

The base URL field only appears for the OpenAI-compatible option (e.g. http://localhost:1234/v1). A mistyped model shows the provider's error right in the popup — fix it in Settings and re-ask.

Use

1. Select text anywhere → tap Ctrl on its own (Ctrl+C, Ctrl+click… never trigger it). Nothing selected? Double-tap Ctrl and Rex opens anyway, ready to ask — a bare Ctrl tap is the one gesture that does nothing else on macOS, Windows, or Linux.
2. Ask. Answers come back short and summarized — say "explain in detail" when you want more. Follow up in the same chat.
3. Change or add context without retapping: while Rex is open, drag-select different text — the pending context updates live. Tap Ctrl to pin it and stack another selection into the same conversation.
4. Esc or ✕ closes (it never closes on its own). Drag any edge to resize.

Fully keyboard-drivable: Esc backs out of settings, then closes · Ctrl/⌘ + , opens settings · Tab moves around · Enter saves · / jumps to the ask box. The full list lives in Settings.

Always on: Rex starts at login and lives in the tray, so the triggers work without opening anything (toggle "Start at login" in the tray menu).

Extras: light/dark theme follows your system (or pick in Settings — light is the dino's day run ☀️, dark is the night run 🌙) · the dino sprints while answers stream · Space makes him jump · your high score persists.

Run from source

Running for the first time

git clone https://github.com/MoustafaTech/rex.git
cd rex && npm install && npm start        # Node 20+, nothing else to install

• macOS: grant Accessibility and Automation to the app that launches Rex (your terminal or IDE — the prompts name it, not Rex), then quit Rex and start it again.
• Linux: install the clipboard helpers listed above.

Running after the first time

cd rex && npm start

• Debug logs: REX_DEBUG=1 npm start · Build installers: npm run dist

How it works

1. A global listener (uiohook-napi) watches for a clean Ctrl tap — any other key or mouse activity during the hold cancels it.
2. Your selection is captured via the primary selection on Linux, or a momentary simulated copy elsewhere. Your clipboard — text, formatting, images — is restored immediately; if it holds something Rex can't put back (like copied files), Rex skips the capture rather than lose it.
3. A frameless, resizable, always-on-top popup opens at your cursor and stays until you close it.
4. Questions + selections go directly from your machine to your provider, streamed back into the popup.

Config lives in your OS's app-data dir (~/Library/Application Support/Rex, %APPDATA%/Rex, or ~/.config/Rex); upgrades from the app's earlier names migrate automatically. The dino is original pixel art — a homage to everyone's favorite offline companion, not a copy.

Privacy

• API keys live only on your device (config file, 0600 on macOS/Linux; protected by your user profile's permissions on Windows).
• The only network calls are the ones you trigger, straight to your configured provider.
• On macOS/Windows, capture briefly transits the OS clipboard — clipboard-history tools (Win+V history, Alfred, Raycast, Maccy) may retain the selected text, and Windows' "Sync across devices" can sync it. On Linux with the helpers installed, Rex reads the selection directly and skips the clipboard.
• No analytics, no telemetry, no accounts.

License

MIT