Unable to use value from an Ember Data store in template

I'm building a simple application using Ember v1.8.1, Ember CLI 0.1.15 and Ember Data 1.0.0-beta.15 in an attempt to learn the basics of Ember.js. Data is coming from a simple REST API, so I'm using the DS.RESTAdapter and DS.RESTSerializer. The payload is normalized in the serializer, because the API doesn't properly wrap its data in the required hashes.

I'm trying to implement an edit route, but am unable to populate the form fields of that template or even display a simple value. My index route, displaying a list of posts, works as expected, but edit doesn't for some reason.

Using {{title}} in my template doesn't render the value, but outputs a string of unexpected data, something along the lines of: <my-app@model:post::ember413:21>. I'm probably passing something improperly from the route or elsewhere, but I'm don't know what and where exactly.

Below is some of my relevant code:

app/router.js

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

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

Router.map(function() {
  this.route('login');

  this.resource('posts', function() {
    this.route('add');
    this.route('view', { path: ':post_id'});
    this.route('edit', { path: ':post_id/edit'});
  });
});

export default Router;

app/routes/posts/edit.js

import Ember from 'ember';
import AuthenticatedRouteMixin from 'simple-auth/mixins/authenticated-route-mixin';

export default Ember.Route.extend(AuthenticatedRouteMixin, {
  model: function(params){
    return this.store.find('post', params.post_id);
  }
});

app/routes/posts/index.js

import Ember from 'ember';
import AuthenticatedRouteMixin from 'simple-auth/mixins/authenticated-route-mixin';

export default Ember.Route.extend(AuthenticatedRouteMixin, {
  model: function(){
    return this.store.find('post');
  }
});

app/controllers/posts/edit.js

import Ember from 'ember';

export default Ember.ObjectController.extend();

app/serializers/application.js

import Ember from "ember";
import DS from "ember-data";

export default DS.RESTSerializer.extend(DS.EmbeddedRecordsMixin, {
  primaryKey: 'ID',
  attrs: {
    author: { embedded: 'always' }
  },
  extractSingle: function(store, type, payload, id) {
    payload = { post : payload };
    return this._super(store, type, payload, id);
  },
  extractArray: function(store, type, payload) {
    payload = { posts : payload };
    return this._super(store, type, payload);
  },
  serializeIntoHash: function(hash, type, record, options) {
    Ember.merge(hash, this.serialize(record, options));
  }
});

Having looked at some examples the above should work, so probably there's an error in the serializer. In the route I can access values from the store however. The following logs the expected data when used in the model method of my edit.js route:

this.store.find('post', params.post_id).then(function(post) {
  console.log(post.get('title'));
});