Protocol

StdUI communicates with the controlling application via stdin/stdout using line-delimited JSON. Every message is a single line of JSON terminated by a newline character.

Message Format

{
  "action": "action_type",
  "data": {
    /* optional data payload */
  }
}

Field	Type	Description
action	string, required	The type of action being sent
data	any, optional	Action-specific payload (object, string, or array)

Action names use kebab-case (e.g. update-content, window-closed).

Minimal round-trip

App → stdui   {"action":"settings","data":{"title":"Hello","windowWidth":400,"windowHeight":300}}
stdui → App   {"action":"ready"}
App → stdui   {"action":"update-content","data":"<h1>Hi</h1><ui-button text=\"Click me\" action=\"hi\"></ui-button>"}
  ... user clicks the button ...
stdui → App   {"action":"button-clicked","data":{"action":"hi","text":"Click me","pane":"main"}}
App → stdui   {"action":"update-content","data":"<h1>You clicked it!</h1>"}
  ... user closes the window ...
stdui → App   {"action":"window-closed"}

Sections

• Core Actions — settings, update-content, lifecycle events
• Interactive Elements — all <ui-*> tags
• Element Actions — set-value, get-value, input-changed, button-clicked
• Window Control — title, icon, position, minimize/maximize, toast, clipboard
• Keybinds — set-keybinds, key-pressed
• Scroll Control — scroll-to
• Pane Layout — set-pane-layout