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Overview

The EventBus is a simple pub/sub system that enables decoupled communication between plugins. 
api.bus.on('todo:added', (data) => {
  console.log('New todo:', data.text);
});

api.bus.emit('todo:added', { text: 'Buy milk' });

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Methods

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bus.on(event, callback)

Subscribe to an event. Multiple listeners can subscribe to the same event. 
api.bus.on('theme:changed', (data) => {
  document.body.style.background = data.color;
});
ParameterTypeDescription
eventstringEvent name
callbackfunctionHandler called with event data

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bus.off(event, callback)

Unsubscribe from an event. Must pass the same function reference used in on(). 
function handler(data) { /* ... */ }

api.bus.on('my-event', handler);
// later:
api.bus.off('my-event', handler);

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bus.once(event, callback)

Subscribe to an event, but the listener is automatically removed after the first emission. 
api.bus.once('board:ready', (data) => {
  console.log('Board is ready, only fires once');
});
ParameterTypeDescription
eventstringEvent name
callbackfunctionHandler called once with event data, then removed

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bus.emit(event, data)

Publish an event to all subscribers. Errors in listeners are caught and logged without interrupting other listeners. 
api.bus.emit('todo:added', { text: 'Buy milk', done: false });
ParameterTypeDescription
eventstringEvent name
dataanyPayload passed to subscribers

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bus.removeAll([event])

Remove all listeners for a specific event, or all events if no event name is given. 
// Remove all listeners for a specific event
api.bus.removeAll('todo:added');

// Remove ALL listeners across all events
api.bus.removeAll();
ParameterTypeDescription
eventstring(Optional) Event name. If omitted, clears everything.
removeAll() with no arguments is a nuclear option. Use with care — it removes listeners from every plugin, not just yours.

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Naming Convention

Use namespace:action to avoid collisions between plugins:
✅ Good❌ Bad
todo:addedadded
kanban:card:movedmove
theme:changedchange
sticky-note:creatednew

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Example: Cross-Plugin Communication

// === todo-list/plugin.js ===
export function setup(api) {
  const todos = [];

  function addTodo(text) {
    todos.push({ text, done: false });
    api.bus.emit('todo:added', { text, count: todos.length });
  }
}

// === stats/plugin.js ===
export function setup(api) {
  let count = 0;

  api.bus.on('todo:added', (data) => {
    count = data.count;
    renderStats();
  });
}
Plugins should never directly import or reference each other. Always use the event bus for communication.