New Twiddle

components.box-container.js

import Ember from 'ember';

export default Ember.Component.extend({
  actions: {
    stopPropagation: function() {
    	event.stopPropagation();
    }
  }
});

components.box-content.js

import Ember from 'ember';

export default Ember.Component.extend({
  actions: {
  	clickMe: function() {
    	alert('1/2 the second message should appear but it\'s blocked by the action stopPropagation of box-container');
    }
  },
  
  click: function() {
  	alert('2/2');
  }
});

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  actions: {
    shouldNotAppear: function() {
      alert('This should not appear');
    }
  },
  
  click: function() {
  	alert('This should not appear');
	}
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{my-component}}
<br>
<br>

templates.components.box-container.hbs

<div onclick={{action 'stopPropagation'}}>
	{{box-content}}
</div>

templates.components.box-content.hbs

Hello <button onclick={{action 'clickMe'}}>Click me</button>

templates.components.my-component.hbs

<div onclick={{action 'shouldNotAppear'}}>
	{{box-container}}
</div>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}