Smooth BrainType as fast as you can. Press Return three times.
Skip the spaces, ignore the typos, don’t look back. Three quick Returns and a very fast model fixes the paragraph you just typed, in place, in well under a second.
Free. Runs on Hammerspoon. Needs an OpenRouter API key.
How it works
Your fingers go first, the fix comes after
Triple Return
Press Return three times quickly in any text field. A normal Enter still works instantly; the third press is what triggers the fix.
Shift+Return in chat apps
Where Return sends the message (Slack, Messages), press Shift+Return three times instead, or ⌘⌥⌃⇧W. Same fix, nothing sent.
Only the last paragraph
Just the paragraph you were typing is sent, and only what you wrote since its last fix. The rest of the message, images included, is never touched.
Install
One command, whether or not you have Hammerspoon
Paste this into Terminal. It installs Hammerspoon if you don’t have it and adds the tool.
curl -fsSL https://flocrivello.com/smooth-brain/install.sh | bash- Allow Hammerspoon in System Settings › Privacy & Security › Accessibility.
- Type something sloppy in any text field and press Return three times (or ⌘⌥⌃⇧W).
- Paste an OpenRouter API key when asked. You can create one at openrouter.ai/keys.
Prefer to do it by hand? Download smooth-brain.zip, unzip it into ~/.hammerspoon/smooth-brain/, and add require("smooth-brain").start() to ~/.hammerspoon/init.lua.
Questions
Does it rewrite what I meant?
No. It is told to keep your words, tone and formatting, and only repair spacing, typos, capitals and punctuation. It doesn’t rephrase or answer anything.
How fast is it?
It runs Qwen on Cerebras through OpenRouter, so a paragraph usually comes back in well under a second. When Cerebras is busy, it retries on the fastest other provider.
What does it cost?
The tool is free. You pay OpenRouter for the model calls, a tiny fraction of a cent per fix.
Where does my text go?
Only the paragraph being fixed, only to OpenRouter. Your API key is stored in your Mac’s Keychain, not in a file.
Why doesn’t triple Return work in Slack or Messages?
There, the first Return already sends the message. Press Shift+Return three times instead (Shift+Return is a line break), or Hyper+W (⌘⌥⌃⇧W).
Can I keep typing while it fixes?
Yes. Nothing is selected while the fix is on its way; when it lands, the paragraph is swapped in a tenth of a second, and anything you type in that instant is held and replayed, so you don’t lose a keystroke.
Can it fix more than one paragraph?
Select the text first and press Hyper+W (⌘⌥⌃⇧W): it fixes exactly the selection, however many paragraphs, and keeps every line break.
Does it touch my clipboard?
No. In native apps it edits the text directly through Accessibility. In browsers it pastes the fix from a temporary clipboard entry that clipboard managers skip, then puts back whatever you had copied, images and files included.
Can I change the shortcut or turn off triple Return?
Yes: in ~/.hammerspoon/init.lua, use require("smooth-brain").start({ hotkey = { {"cmd","alt"}, "f" }, tripleReturn = false }).