Hammerdeck

The gap it fills

macOS tiles in halves and quarters. That is the right answer on a laptop and the wrong one on a 49-inch ultrawide — and across two or three displays there is no keyboard shortcut at all, at any macOS version, to send a window to the other display or to swap what sits on each.

Hammerdeck puts all of it on keys: grids (name two cells, the window spans them), throws and swaps between displays, a deck that keeps every window reachable, a modal layer for arranging by feel, and one-key undo for any of it — each on a hotkey or a chord (cmd+shift+a, then b). Actions that need no context — refresh the wallpaper, open a set of tabs — also take a schedule or a system event.

It is a native Swift app with a Lua engine inside — think a focused, miniature Hammerspoon — except you never write Lua. Every feature is a switch, some options, and a trigger picker.

See it on an ultrawide

Rules that rebuild the layout for you

Beyond the catalog, the rules engine wires features together — built in Settings, no code. A rule pairs a signal (frontmost app, displays connected, an app launches or quits, light/dark appearance, power source) with effects: move windows to a saved layout, run any feature's action, set the wallpaper, lock the screen, launch or quit an app, or chain several together. Where the built-in effects end, a rule can run any macOS Shortcut — the escape hatch to everything else.

Bind it to anything

Options and triggers are generated from the feature's own declaration — there is no per-feature settings code, and no config file to hand-edit. Any action can be driven by a hotkey, a chord, a schedule, or a system event.

Automation you can see

Every shortcut press flashes which action fired, automated runs can tell you what happened while you were away, one hotkey rewinds the last window rearrangement, and every decision lands in a local, plain-text log.

Many features run with no macOS permission at all. The ones that need one:

• Accessibility — to read or move windows, act on the current selection, or press keys on your behalf: Window Snap, Window Grid, Window Mode, Window Deck, Window Fan, Window Rewind, Pointer Follows Moved Window, Window Switcher, Clipboard History, Insert Date/Time, Paste as Plain Text, Text Actions, Break Reminder, Pointer, the rules engine (arranging windows, moving an app to a display, minimizing an app, locking the screen, media keys).
• Automation — features that read browser tabs drive Chrome and Safari through AppleScript, so macOS prompts once per browser: Usage Stats, Tab Switcher, Quick Sites.
• Automation (System Events) — switching the system between dark and light goes through System Events, so macOS prompts once, the first time a rule does it: the rules engine (Switch to dark, Switch to light, Toggle dark mode).
• Full Disk Access — emptying the Trash reads a folder macOS protects, and macOS never prompts for this one, so switch Hammerdeck on under Privacy & Security yourself: the rules engine (Empty the Trash).

• An OpenAI key (yours, stored in the Keychain) — only for Text Actions' AI transforms. Everything else in that feature works without one.

Nothing is requested at install. First launch explains why the window features need Accessibility and offers a button to grant it; most others ask when you switch them on or first use them, and a feature you never enable never asks. Full Disk Access is the exception: macOS never asks for it, so you grant it yourself if you want the Empty the Trash rule. If a feature does nothing, the pinned permission gotchas issue covers the known causes. Every feature also declares what it may reach — the “Reaches” notes in the catalog above — and the app withholds anything undeclared at run time.

Write your own — or let your coding agent

It is off until you turn it on and reachable only from this machine. This is auditability rather than a sandbox: an extension is code you chose to run, and the point is that its reach is written down and machine-checked — validate_extension compares the declaration against what the code actually calls, in both directions. There is no tool for running arbitrary Lua, and the widest declaration, exec, says in as many words that a program can do whatever you can.

Install

Download the disk image, open it, and drag Hammerdeck to Applications — if you run it from somewhere else it offers to move itself on first launch. A hammer icon appears in the menubar; Settings… opens the config window. First run starts with the window suite on — the features marked on by default above — and explains the Accessibility ask before macOS shows it. Everything else stays off until you switch it on.

Or install it with Homebrew. It still updates itself, so brew upgrade leaves it alone:

brew install --cask kouxing2000/tap/hammerdeck

Or build it from source (Xcode 16 or later; on macOS 14 also brew install jq):

git clone https://github.com/kouxing2000/hammerdeck.git
cd hammerdeck
scripts/app.sh start