diff --git a/app/assets/javascripts/discourse/app/instance-initializers/logs-notice.js b/app/assets/javascripts/discourse/app/instance-initializers/logs-notice.js
deleted file mode 100644
index ea5beaad67a..00000000000
--- a/app/assets/javascripts/discourse/app/instance-initializers/logs-notice.js
+++ /dev/null
@@ -1,30 +0,0 @@
-import Singleton from "discourse/mixins/singleton";
-import LogsNotice from "discourse/services/logs-notice";
-let initializedOnce = false;
-
-export default {
-  after: "message-bus",
-
-  initialize(owner) {
-    if (initializedOnce) {
-      return;
-    }
-
-    const siteSettings = owner.lookup("service:site-settings");
-    const messageBus = owner.lookup("service:message-bus");
-    const keyValueStore = owner.lookup("service:key-value-store");
-    const currentUser = owner.lookup("service:current-user");
-    LogsNotice.reopenClass(Singleton, {
-      createCurrent() {
-        return this.create({
-          messageBus,
-          keyValueStore,
-          siteSettings,
-          currentUser,
-        });
-      },
-    });
-
-    initializedOnce = true;
-  },
-};
diff --git a/app/assets/javascripts/discourse/app/lib/singleton.js b/app/assets/javascripts/discourse/app/lib/singleton.js
new file mode 100644
index 00000000000..d3d3b6756df
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/lib/singleton.js
@@ -0,0 +1,79 @@
+/**
+ * @decorator
+ * Ensures only one instance of a class exists and provides global access to it.
+ *
+ * @example
+ * ```
+ * @singleton
+ * class UserSettings {
+ *   theme = 'light';
+ *
+ *   toggleTheme() {
+ *     this.theme = this.theme === 'light' ? 'dark' : 'light';
+ *   }
+ * }
+ *
+ * // Get the singleton instance
+ * const settings = UserSettings.current();
+ *
+ * // Access properties
+ * UserSettings.currentProp('theme'); // 'light'
+ * UserSettings.currentProp('theme', 'dark'); // sets and returns 'dark'
+ *
+ * // Multiple calls return the same instance
+ * UserSettings.current() === UserSettings.current(); // true
+ *
+ * // If you want to customize what logic is executed during creation of the singleton, redefine the `createCurrent` method:
+ * @singleton
+ * class UserSettings {
+ *   theme = 'light';
+ *
+ *   toggleTheme() {
+ *     this.theme = this.theme === 'light' ? 'dark' : 'light';
+ *   }
+ *
+ *   static createCurrent() {
+ *     return this.create({ font: 'Comic-Sans' });
+ *   }
+ * }
+ *
+ * UserSettings.currentProp('font'); // 'Comic-Sans'
+ * ```
+ */
+export default function singleton(targetKlass) {
+  targetKlass._current = null;
+
+  // check ensures that we don't overwrite a customized createCurrent
+  if (!targetKlass.createCurrent) {
+    targetKlass.createCurrent = function () {
+      return this.create();
+    };
+  }
+
+  targetKlass.current = function () {
+    if (!this._current) {
+      this._current = this.createCurrent();
+    }
+    return this._current;
+  };
+
+  targetKlass.currentProp = function (property, value) {
+    const instance = this.current();
+    if (!instance) {
+      return;
+    }
+
+    if (typeof value !== "undefined") {
+      instance.set(property, value);
+      return value;
+    }
+    return instance.get(property);
+  };
+
+  targetKlass.resetCurrent = function (val) {
+    this._current = val;
+    return val;
+  };
+
+  return targetKlass;
+}
diff --git a/app/assets/javascripts/discourse/app/mixins/singleton.js b/app/assets/javascripts/discourse/app/mixins/singleton.js
index 71cf1531eb8..a8baf6067ee 100644
--- a/app/assets/javascripts/discourse/app/mixins/singleton.js
+++ b/app/assets/javascripts/discourse/app/mixins/singleton.js
@@ -1,53 +1,66 @@
 /**
-  This mixin allows a class to return a singleton, as well as a method to quickly
-  read/write attributes on the singleton.
+ This mixin allows a class to return a singleton, as well as a method to quickly
+ read/write attributes on the singleton.
 
 
-  Example usage:
+ Example usage:
 
-  ```javascript
+ ```javascript
 
-    // Define your class and apply the Mixin
-    User = EmberObject.extend({});
-    User.reopenClass(Singleton);
+ // Define your class and apply the Mixin
+ User = EmberObject.extend({});
+ User.reopenClass(Singleton);
 
-    // Retrieve the current instance:
-    var instance = User.current();
+ // Retrieve the current instance:
+ var instance = User.current();
 
-  ```
+ ```
 
-  Commonly you want to read or write a property on the singleton. There's a
-  helper method which is a little nicer than `.current().get()`:
+ Commonly you want to read or write a property on the singleton. There's a
+ helper method which is a little nicer than `.current().get()`:
 
-  ```javascript
+ ```javascript
 
-    // Sets the age to 34
-    User.currentProp('age', 34);
+ // Sets the age to 34
+ User.currentProp('age', 34);
 
-    console.log(User.currentProp('age')); // 34
+ console.log(User.currentProp('age')); // 34
 
-  ```
+ ```
 
-  If you want to customize how the singleton is created, redefine the `createCurrent`
-  method:
+ If you want to customize how the singleton is created, redefine the `createCurrent`
+ method:
 
-  ```javascript
+ ```javascript
 
-    // Define your class and apply the Mixin
-    Foot = EmberObject.extend({});
-    Foot.reopenClass(Singleton, {
-      createCurrent() {
-        return Foot.create({ toes: 5 });
-      }
-    });
+ // Define your class and apply the Mixin
+ Foot = EmberObject.extend({});
+ Foot.reopenClass(Singleton, {
+ createCurrent() {
+ return Foot.create({ toes: 5 });
+ }
+ });
 
-    console.log(Foot.currentProp('toes')); // 5
+ console.log(Foot.currentProp('toes')); // 5
 
-  ```
-**/
+ ```
+ **/
 import Mixin from "@ember/object/mixin";
+import deprecated from "discourse-common/lib/deprecated";
 
 const Singleton = Mixin.create({
+  init() {
+    this._super(...arguments);
+
+    deprecated(
+      "Singleton mixin is deprecated. Use the singleton class decorator from discourse/lib/singleton instead.",
+      {
+        id: "discourse.singleton-mixin",
+        since: "v3.4.0.beta4-dev",
+      }
+    );
+  },
+
   current() {
     if (!this._current) {
       this._current = this.createCurrent();
@@ -56,11 +69,11 @@ const Singleton = Mixin.create({
   },
 
   /**
-    How the singleton instance is created. This can be overridden
-    with logic for creating (or even returning null) your instance.
+   How the singleton instance is created. This can be overridden
+   with logic for creating (or even returning null) your instance.
 
-    By default it just calls `create` with an empty object.
-  **/
+   By default it just calls `create` with an empty object.
+   **/
   createCurrent() {
     return this.create({});
   },
diff --git a/app/assets/javascripts/discourse/app/models/session.js b/app/assets/javascripts/discourse/app/models/session.js
index d684efabe89..6557f411f62 100644
--- a/app/assets/javascripts/discourse/app/models/session.js
+++ b/app/assets/javascripts/discourse/app/models/session.js
@@ -1,9 +1,10 @@
-import Singleton from "discourse/mixins/singleton";
+import singleton from "discourse/lib/singleton";
 import RestModel from "discourse/models/rest";
 
 // A data model representing current session data. You can put transient
 // data here you might want later. It is not stored or serialized anywhere.
-export default class Session extends RestModel.extend().reopenClass(Singleton) {
+@singleton
+export default class Session extends RestModel {
   hasFocus = null;
 
   init() {
diff --git a/app/assets/javascripts/discourse/app/models/site.js b/app/assets/javascripts/discourse/app/models/site.js
index 01784286feb..6207abe9c27 100644
--- a/app/assets/javascripts/discourse/app/models/site.js
+++ b/app/assets/javascripts/discourse/app/models/site.js
@@ -5,7 +5,7 @@ import { service } from "@ember/service";
 import { htmlSafe } from "@ember/template";
 import { isEmpty } from "@ember/utils";
 import PreloadStore from "discourse/lib/preload-store";
-import Singleton from "discourse/mixins/singleton";
+import singleton from "discourse/lib/singleton";
 import Archetype from "discourse/models/archetype";
 import Category from "discourse/models/category";
 import PostActionType from "discourse/models/post-action-type";
@@ -16,7 +16,8 @@ import { getOwnerWithFallback } from "discourse-common/lib/get-owner";
 import { needsHbrTopicList } from "discourse-common/lib/raw-templates";
 import discourseComputed from "discourse-common/utils/decorators";
 
-export default class Site extends RestModel.extend().reopenClass(Singleton) {
+@singleton
+export default class Site extends RestModel {
   static createCurrent() {
     const store = getOwnerWithFallback(this).lookup("service:store");
     const siteAttributes = PreloadStore.get("site");
diff --git a/app/assets/javascripts/discourse/app/models/user.js b/app/assets/javascripts/discourse/app/models/user.js
index 99cb6f6269a..2924b676089 100644
--- a/app/assets/javascripts/discourse/app/models/user.js
+++ b/app/assets/javascripts/discourse/app/models/user.js
@@ -17,10 +17,10 @@ import cookie, { removeCookie } from "discourse/lib/cookie";
 import { longDate } from "discourse/lib/formatter";
 import { NotificationLevels } from "discourse/lib/notification-levels";
 import PreloadStore from "discourse/lib/preload-store";
+import singleton from "discourse/lib/singleton";
 import { emojiUnescape } from "discourse/lib/text";
 import { userPath } from "discourse/lib/url";
 import { defaultHomepage, escapeExpression } from "discourse/lib/utilities";
-import Singleton from "discourse/mixins/singleton";
 import Badge from "discourse/models/badge";
 import Bookmark from "discourse/models/bookmark";
 import Category from "discourse/models/category";
@@ -174,7 +174,36 @@ function userOption(userOptionKey) {
   });
 }
 
+@singleton
 export default class User extends RestModel.extend(Evented) {
+  static createCurrent() {
+    const userJson = PreloadStore.get("currentUser");
+    if (userJson) {
+      userJson.isCurrent = true;
+
+      if (userJson.primary_group_id) {
+        const primaryGroup = userJson.groups.find(
+          (group) => group.id === userJson.primary_group_id
+        );
+        if (primaryGroup) {
+          userJson.primary_group_name = primaryGroup.name;
+        }
+      }
+
+      if (!userJson.user_option.timezone) {
+        userJson.user_option.timezone = moment.tz.guess();
+        this._saveTimezone(userJson);
+      }
+
+      const store = getOwnerWithFallback(this).lookup("service:store");
+      const currentUser = store.createRecord("user", userJson);
+      currentUser.statusManager.trackStatus();
+      return currentUser;
+    }
+
+    return null;
+  }
+
   @service appEvents;
   @service userTips;
 
@@ -1253,42 +1282,13 @@ export default class User extends RestModel.extend(Evented) {
   }
 }
 
-User.reopenClass(Singleton, {
+User.reopenClass({
   // Find a `User` for a given username.
   findByUsername(username, options) {
     const user = User.create({ username });
     return user.findDetails(options);
   },
 
-  // TODO: Use app.register and junk Singleton
-  createCurrent() {
-    const userJson = PreloadStore.get("currentUser");
-    if (userJson) {
-      userJson.isCurrent = true;
-
-      if (userJson.primary_group_id) {
-        const primaryGroup = userJson.groups.find(
-          (group) => group.id === userJson.primary_group_id
-        );
-        if (primaryGroup) {
-          userJson.primary_group_name = primaryGroup.name;
-        }
-      }
-
-      if (!userJson.user_option.timezone) {
-        userJson.user_option.timezone = moment.tz.guess();
-        this._saveTimezone(userJson);
-      }
-
-      const store = getOwnerWithFallback(this).lookup("service:store");
-      const currentUser = store.createRecord("user", userJson);
-      currentUser.statusManager.trackStatus();
-      return currentUser;
-    }
-
-    return null;
-  },
-
   checkUsername(username, email, for_user_id) {
     return ajax(userPath("check_username"), {
       data: { username, email, for_user_id },
diff --git a/app/assets/javascripts/discourse/app/services/logs-notice.js b/app/assets/javascripts/discourse/app/services/logs-notice.js
index 8a733ff1592..53b52fabfc2 100644
--- a/app/assets/javascripts/discourse/app/services/logs-notice.js
+++ b/app/assets/javascripts/discourse/app/services/logs-notice.js
@@ -1,5 +1,5 @@
 import { readOnly } from "@ember/object/computed";
-import Service from "@ember/service";
+import Service, { service } from "@ember/service";
 import { htmlSafe } from "@ember/template";
 import { isEmpty } from "@ember/utils";
 import { observes } from "@ember-decorators/object";
@@ -11,6 +11,11 @@ import I18n from "discourse-i18n";
 const LOGS_NOTICE_KEY = "logs-notice-text";
 
 export default class LogsNoticeService extends Service {
+  @service siteSettings;
+  @service currentUser;
+  @service keyValueStore;
+  @service messageBus;
+
   text = "";
 
   @readOnly("currentUser.admin") isAdmin;
diff --git a/app/assets/javascripts/discourse/tests/unit/lib/singleton-test.js b/app/assets/javascripts/discourse/tests/unit/lib/singleton-test.js
new file mode 100644
index 00000000000..1f4f1012e28
--- /dev/null
+++ b/app/assets/javascripts/discourse/tests/unit/lib/singleton-test.js
@@ -0,0 +1,105 @@
+import EmberObject from "@ember/object";
+import { setupTest } from "ember-qunit";
+import { module, test } from "qunit";
+import singleton from "discourse/lib/singleton";
+
+module("Unit | Lib | singleton", function (hooks) {
+  setupTest(hooks);
+
+  test("current", function (assert) {
+    @singleton
+    class DummyModel extends EmberObject {}
+
+    const current = DummyModel.current();
+    assert.present(current, "current returns the current instance");
+    assert.strictEqual(
+      current,
+      DummyModel.current(),
+      "calling it again returns the same instance"
+    );
+    assert.notStrictEqual(
+      current,
+      DummyModel.create({}),
+      "we can create other instances that are not the same as current"
+    );
+  });
+
+  test("currentProp reading", function (assert) {
+    @singleton
+    class DummyModel extends EmberObject {}
+
+    const current = DummyModel.current();
+
+    assert.blank(
+      DummyModel.currentProp("evil"),
+      "by default attributes are blank"
+    );
+    current.set("evil", "trout");
+    assert.strictEqual(
+      DummyModel.currentProp("evil"),
+      "trout",
+      "after changing the instance, the value is set"
+    );
+  });
+
+  test("currentProp writing", function (assert) {
+    @singleton
+    class DummyModel extends EmberObject {}
+
+    assert.blank(
+      DummyModel.currentProp("adventure"),
+      "by default attributes are blank"
+    );
+    let result = DummyModel.currentProp("adventure", "time");
+    assert.strictEqual(result, "time", "it returns the new value");
+    assert.strictEqual(
+      DummyModel.currentProp("adventure"),
+      "time",
+      "after calling currentProp the value is set"
+    );
+
+    DummyModel.currentProp("count", 0);
+    assert.strictEqual(
+      DummyModel.currentProp("count"),
+      0,
+      "we can set the value to 0"
+    );
+
+    DummyModel.currentProp("adventure", null);
+    assert.strictEqual(
+      DummyModel.currentProp("adventure"),
+      null,
+      "we can set the value to null"
+    );
+  });
+
+  test("createCurrent", function (assert) {
+    @singleton
+    class Shoe extends EmberObject {
+      static createCurrent() {
+        return this.create({ toes: 5 });
+      }
+    }
+
+    assert.strictEqual(
+      Shoe.currentProp("toes"),
+      5,
+      "it created the class using `createCurrent`"
+    );
+  });
+
+  test("createCurrent that returns null", function (assert) {
+    @singleton
+    class Missing extends EmberObject {
+      static createCurrent() {
+        return null;
+      }
+    }
+
+    assert.blank(Missing.current(), "it doesn't return an instance");
+    assert.blank(
+      Missing.currentProp("madeup"),
+      "it won't raise an error asking for a property. Will just return null."
+    );
+  });
+});