Incorrect (using constructor):

// app/components/user-profile.gjs
import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { service } from '@ember/service';

class UserProfile extends Component {
  constructor() {
    super(...arguments);

    // Anti-pattern: Manual service lookup
    this.store = this.owner.lookup('service:store');
    this.router = this.owner.lookup('service:router');

    // Anti-pattern: Imperative initialization
    this.data = null;
    this.isLoading = false;
    this.error = null;

    // Anti-pattern: Side effects in constructor
    this.loadUserData();
  }

  async loadUserData() {
    this.isLoading = true;
    try {
      this.data = await this.store.request({
        url: `/users/${this.args.userId}`,
      });
    } catch (e) {
      this.error = e;
    } finally {
      this.isLoading = false;
    }
  }

  <template>
    {{#if this.isLoading}}
      <div>Loading...</div>
    {{else if this.error}}
      <div>Error: {{this.error.message}}</div>
    {{else if this.data}}
      <h1>{{this.data.name}}</h1>
    {{/if}}
  </template>
}