Working sticky params

index.route.js

import Ember from 'ember';

export default Ember.Route.extend({
  
    beforeModel: function() {
    this.transitionTo('parent', 'A');
  }

});

parent.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: ['test'],
  test: 1,
  
  actions: {
    update: function() {
 this.incrementProperty('test');
    }
  }
});

parent.index.route.js

import Ember from 'ember';

export default Ember.Route.extend({
  model: function(params) {
      return new Ember.RSVP.Promise(function(resolve) {
        setTimeout(function() {
          resolve({name: 'A'});
        }, 500);
      });
  }

});

parent.template.hbs

<h3>Query param value: {{test}}</h3>
    <button {{action 'update'}}>Click me to change the query param value!</button>
  <p>{{#link-to 'parent.index' 'B' }}Then change the model param{{/link-to}}</p>
  <p>... click the button a few more times...</p>
  <p>{{#link-to 'parent.index' 'A' }}Return to the first model param again{{/link-to}} and see that the query param value is sticky.</p>
  <p>{{#link-to 'parent.index' 'B' }}And back to the second model param again{{/link-to}} to confirm it.</p>
    {{outlet}}

router.js

import Ember from 'ember';
import config from './config/environment';

var Router = Ember.Router.extend({
  location: config.locationType
});

Router.map(function() {
  this.route('parent', {path: '/:parent_param'}, function() {});
});

export default Router;

twiddle.json

{
  "version": "0.4.16",
  "EmberENV": {
    "FEATURES": {}
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.1.0",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.1.0/ember-data.js",
    "ember-template-compiler": "2.1.0"
  }
}