diff --git a/.github/workflows/feature-screenshots.yml b/.github/workflows/feature-screenshots.yml
index 845d219..3b0511c 100644
--- a/.github/workflows/feature-screenshots.yml
+++ b/.github/workflows/feature-screenshots.yml
@@ -40,6 +40,9 @@ jobs:
       PARALLEL_TEST_PROCESSORS: 1
       LOAD_PLUGINS: 1
       CAPYBARA_DEFAULT_MAX_WAIT_TIME: 10
+      # Opts the pop-up gallery specs in — they skip themselves in the main
+      # parallel system_tests job (to keep it lean) and only run here.
+      JTECH_SCREENSHOT_GALLERY: "1"
 
     steps:
       - name: Set working directory owner
@@ -130,7 +133,10 @@ jobs:
             --format documentation \
             plugins/${{ env.PLUGIN_NAME }}/spec/system/feature_screenshots_spec.rb \
             plugins/${{ env.PLUGIN_NAME }}/spec/system/review_queue_click_through_spec.rb \
-            plugins/${{ env.PLUGIN_NAME }}/spec/system/notifications_type_filter_spec.rb
+            plugins/${{ env.PLUGIN_NAME }}/spec/system/notifications_type_filter_spec.rb \
+            plugins/${{ env.PLUGIN_NAME }}/spec/system/popup_notifications_screenshots_spec.rb \
+            plugins/${{ env.PLUGIN_NAME }}/spec/system/popup_notifications_stacking_screenshots_spec.rb \
+            plugins/${{ env.PLUGIN_NAME }}/spec/system/popup_notifications_click_through_spec.rb
         continue-on-error: true
 
       - name: Upload feature screenshots (always)
diff --git a/README.md b/README.md
index ff3884d..1d7c659 100644
--- a/README.md
+++ b/README.md
@@ -13,9 +13,26 @@ One combined Discourse plugin. Bundles seven previously-separate plugins under a
 | Dumbcourse | `DiscourseDumbcourse` | `dumbcourse_*` | `dumbcourse_enabled` |
 | Translator-tweaks | *(patches `DiscourseTranslator`)* | *(none — gated by translator's own settings)* | `translator_enabled` (upstream) |
 | Smart search | `DiscourseSmartSearch` | `smart_search_*` | `smart_search_enabled` |
+| Desktop pop-ups | `DiscoursePopupNotifications` | `popup_notifications_*` | `popup_notifications_enabled` |
 
 The bundle is gated by `jtech_enabled`; each sub-plugin is independently gated by its own setting above.
 
+### Desktop pop-up notifications
+
+A Jelly-style toast card that appears in the top-right corner (just below the header search) when a new notification arrives, modelled on the [Jelly](https://github.com/lubabs770/Jelly) macOS notifier's look and delivery.
+
+- **Purely additive.** It subscribes to the same `/notification/:user_id` MessageBus channel that already drives the bell counter and the notifications dropdown, and does nothing else — the bell, the dropdown, and read-state are untouched. Turning it off simply stops the card from appearing.
+- **Desktop only.** Never mounts on mobile (`site.mobileView`).
+- **Opt-in per user, off by default.** Each user turns it on via a **Desktop Pop Up Notifications** On/Off dropdown on their account page (`/u/:username/preferences/account`), stored in the `jtech_popup_notifications_enabled` user custom field. `popup_notifications_default_enabled` (default `false`) controls the default for users who haven't chosen.
+- **Card layout:** the acting user's name on top, their avatar on the left, the topic title in bold, then a short preview of their message (fetched from the source post).
+- **Interaction:** clicking the card routes to the post (same as clicking the row in the dropdown); clicking anywhere else — or waiting `popup_notifications_timeout_seconds` (default 20) — dismisses it.
+
+| Setting | Default | Purpose |
+| --- | --- | --- |
+| `popup_notifications_enabled` | `true` | Master switch. Off ⇒ no card for anyone, per-user preference hidden. |
+| `popup_notifications_default_enabled` | `false` | Default for users who haven't set the account-page preference. |
+| `popup_notifications_timeout_seconds` | `20` | Seconds the card stays before auto-dismissing. |
+
 ### Mod-categories — staff-event notifications
 
 Mod-categories ships a notification fan-out for five staff-event streams in addition to its original topic-level moderator notes. Whenever a moderator performs one of the actions below, every OTHER staff member gets a high-priority bell notification + live MessageBus pop-up alert, AND the event surfaces in the shield-tab user menu alongside topic notes.
diff --git a/assets/javascripts/discourse/components/jtech-popup-notification.gjs b/assets/javascripts/discourse/components/jtech-popup-notification.gjs
new file mode 100644
index 0000000..54e6ea0
--- /dev/null
+++ b/assets/javascripts/discourse/components/jtech-popup-notification.gjs
@@ -0,0 +1,344 @@
+import Component from "@glimmer/component";
+import { tracked } from "@glimmer/tracking";
+import { fn } from "@ember/helper";
+import { on } from "@ember/modifier";
+import { action } from "@ember/object";
+import { cancel } from "@ember/runloop";
+import { service } from "@ember/service";
+import icon from "discourse/helpers/d-icon";
+import { ajax } from "discourse/lib/ajax";
+import { getURLWithCDN } from "discourse/lib/get-url";
+import discourseLater from "discourse/lib/later";
+import DiscourseURL from "discourse/lib/url";
+import { i18n } from "discourse-i18n";
+
+// Desktop-only, Jelly-style pop-up "toast". Purely ADDITIVE — it renders a
+// card when a new notification is published on the current user's
+// `/notification/:id` MessageBus channel (the same channel that already
+// drives the bell counter and the notifications dropdown) and does nothing
+// else. Core notifications, the bell, the dropdown, and read-state are all
+// untouched; turning the feature off simply stops the cards from appearing.
+//
+// Multiple notifications STACK one below another: the newest card sits at the
+// top-right (just below the header search) and older ones are pushed down,
+// each with its own auto-dismiss timer, up to MAX_TOASTS at once. A further
+// notification drops the oldest (bottom) card so the newest can take its
+// place. Clicking a card opens it (routes like the dropdown row); clicking
+// anywhere else dismisses them all.
+//
+// Card layout: the acting user's avatar on the left (with a small type-icon
+// badge on its corner), then a heading line "Name — Action" (e.g.
+// "pat — Liked your post"), the topic title in bold, and a short preview of
+// the message.
+//
+// Fires for every notification the user receives, including the plugin's
+// own `custom` notifications — moderator whispers, flag notes, and
+// queued/pending-post approvals/rejections — decoded via their `data`
+// markers below. Never mounts on mobile or for users who have not opted in.
+const AVATAR_SIZE = 48;
+const EXCERPT_LENGTH = 120;
+const STALE_MS = 10000;
+const MAX_TOASTS = 3; // stack up to 3; a 4th drops the oldest (bottom) card
+const CUSTOM_TYPE = 14; // Notification.types[:custom]
+
+// notification_type (core enum, stable) → icon + action i18n key suffix.
+const CORE_TYPES = {
+  1: { icon: "at", action: "mentioned" },
+  2: { icon: "reply", action: "replied" },
+  3: { icon: "quote-right", action: "quoted" },
+  4: { icon: "pencil", action: "edited" },
+  5: { icon: "heart", action: "liked" },
+  6: { icon: "envelope", action: "messaged" },
+  7: { icon: "envelope", action: "messaged" },
+  9: { icon: "reply", action: "posted" },
+  11: { icon: "link", action: "linked" },
+  12: { icon: "certificate", action: "badge" },
+  15: { icon: "at", action: "mentioned" },
+  17: { icon: "reply", action: "posted" },
+  19: { icon: "heart", action: "liked" },
+  20: { icon: "check", action: "post_approved" },
+  25: { icon: "heart", action: "liked" },
+};
+
+// This plugin's `custom` notifications, keyed by their `data.mod_note_kind`.
+const MOD_NOTE_KINDS = {
+  post_deleted: { icon: "trash-can", action: "post_deleted" },
+  post_approved: { icon: "check", action: "post_approved" },
+  post_rejected: { icon: "xmark", action: "post_rejected" },
+  user_note: { icon: "shield-halved", action: "user_note" },
+  flag_note: { icon: "flag", action: "flag_note" },
+  note: { icon: "shield-halved", action: "note" },
+};
+
+const FALLBACK = { icon: "bell", action: "default" };
+
+export default class JtechPopupNotification extends Component {
+  @service currentUser;
+  @service siteSettings;
+  @service site;
+  @service messageBus;
+
+  @tracked toasts = [];
+
+  channel = null;
+  seen = new Set();
+  listening = false;
+
+  constructor() {
+    super(...arguments);
+    if (
+      !this.currentUser ||
+      this.site.mobileView ||
+      !this.siteSettings.popup_notifications_enabled
+    ) {
+      return;
+    }
+    this.mountedAt = Date.now();
+    this.channel = `/notification/${this.currentUser.id}`;
+    this.onDocumentClick = this.onDocumentClick.bind(this);
+    this.messageBus.subscribe(this.channel, this.onMessage);
+  }
+
+  willDestroy() {
+    super.willDestroy(...arguments);
+    this.dismissAll();
+    if (this.channel) {
+      this.messageBus.unsubscribe(this.channel, this.onMessage);
+    }
+  }
+
+  // Read live so saving the account-page dropdown (which mirrors the value
+  // onto currentUser) takes effect without a page reload.
+  get prefEnabled() {
+    return !!this.currentUser?.jtech_popup_notifications_enabled;
+  }
+
+  // Icon + action label for a notification. Core types come from the stable
+  // enum map; our own `custom` notifications are decoded from their data
+  // markers (whisper, mod-note kinds — which cover flag notes and
+  // queued/pending-post approvals and rejections).
+  metaFor(notification) {
+    const data = notification.data || {};
+    if (notification.notification_type === CUSTOM_TYPE) {
+      if (data.mod_whisper) {
+        return { icon: "eye", action: "whispered" };
+      }
+      if (data.mod_note) {
+        return MOD_NOTE_KINDS[data.mod_note_kind] || MOD_NOTE_KINDS.note;
+      }
+      return FALLBACK;
+    }
+    return CORE_TYPES[notification.notification_type] || FALLBACK;
+  }
+
+  @action
+  async onMessage(payload) {
+    try {
+      if (!this.prefEnabled) {
+        return;
+      }
+      const notification = payload?.last_notification?.notification;
+      if (!notification || notification.read) {
+        return;
+      }
+      // Show each notification at most once (guards MessageBus replays and
+      // re-adds after dismissal).
+      if (this.seen.has(notification.id)) {
+        return;
+      }
+      // Ignore MessageBus backlog replayed from before this tab mounted.
+      const createdAt = Date.parse(notification.created_at);
+      if (createdAt && createdAt < this.mountedAt - STALE_MS) {
+        return;
+      }
+      this.seen.add(notification.id);
+      await this.present(notification);
+    } catch {
+      // A malformed payload must never break the page.
+    }
+  }
+
+  async present(notification) {
+    const data = notification.data || {};
+    const meta = this.metaFor(notification);
+    const toast = {
+      key: notification.id,
+      name:
+        data.display_username ||
+        data.username ||
+        data.original_username ||
+        data.mentioned_by_username ||
+        i18n("jtech_popup_notifications.someone"),
+      action: i18n(`jtech_popup_notifications.action.${meta.action}`),
+      icon: meta.icon,
+      title: notification.fancy_title || data.topic_title || "",
+      excerpt: data.excerpt || "",
+      avatarUrl: null,
+      url: this.urlFor(notification),
+      timer: null,
+    };
+
+    // Enrich with the acting user's avatar + a preview of their message from
+    // the source post. Best-effort: the card still shows without it (custom
+    // notifications such as flag notes have no source post — they render the
+    // type icon on its own instead of an avatar).
+    try {
+      const post = await this.fetchPost(notification, data);
+      if (post) {
+        if (post.avatar_template) {
+          toast.avatarUrl = getURLWithCDN(
+            post.avatar_template.replace("{size}", AVATAR_SIZE)
+          );
+        }
+        if (!toast.excerpt && post.cooked) {
+          toast.excerpt = this.excerptFrom(post.cooked);
+        }
+      }
+    } catch {
+      // ignore enrichment failure — show what we have
+    }
+
+    // The preference may have flipped off during the await.
+    if (!this.prefEnabled) {
+      return;
+    }
+    this.addToast(toast);
+  }
+
+  // Prepend the newest card; drop the oldest beyond the cap. Each card gets
+  // its own auto-dismiss timer.
+  addToast(toast) {
+    const secs =
+      parseInt(this.siteSettings.popup_notifications_timeout_seconds, 10) || 20;
+    toast.timer = discourseLater(this, this.dismiss, toast, secs * 1000);
+
+    const next = [toast, ...this.toasts];
+    while (next.length > MAX_TOASTS) {
+      const dropped = next.pop();
+      cancel(dropped.timer);
+      this.seen.delete(dropped.key);
+    }
+    this.toasts = next;
+
+    if (!this.listening) {
+      document.addEventListener("click", this.onDocumentClick, true);
+      this.listening = true;
+    }
+  }
+
+  fetchPost(notification, data) {
+    if (data.original_post_id) {
+      return ajax(`/posts/${data.original_post_id}.json`);
+    }
+    if (notification.topic_id && notification.post_number) {
+      return ajax(
+        `/posts/by_number/${notification.topic_id}/${notification.post_number}.json`
+      );
+    }
+    return null;
+  }
+
+  excerptFrom(cooked) {
+    const el = document.createElement("div");
+    el.innerHTML = cooked;
+    const text = (el.textContent || "").replace(/\s+/g, " ").trim();
+    return text.length > EXCERPT_LENGTH
+      ? `${text.slice(0, EXCERPT_LENGTH)}…`
+      : text;
+  }
+
+  urlFor(notification) {
+    const data = notification.data || {};
+    if (notification.topic_id && notification.slug) {
+      const suffix = notification.post_number
+        ? `/${notification.post_number}`
+        : "";
+      return `/t/${notification.slug}/${notification.topic_id}${suffix}`;
+    }
+    if (data.url) {
+      return data.url;
+    }
+    return `/u/${this.currentUser.username}/notifications`;
+  }
+
+  stopListening() {
+    if (this.listening) {
+      document.removeEventListener("click", this.onDocumentClick, true);
+      this.listening = false;
+    }
+  }
+
+  onDocumentClick(event) {
+    // A click anywhere outside every card dismisses them all. Clicks on a
+    // card are handled by `open` (this capture-phase listener only acts when
+    // the target is outside).
+    if (!event.target.closest(".jtech-popup-toast")) {
+      this.dismissAll();
+    }
+  }
+
+  @action
+  open(toast) {
+    const url = toast.url;
+    this.dismiss(toast);
+    if (url) {
+      DiscourseURL.routeTo(url);
+    }
+  }
+
+  @action
+  dismiss(toast) {
+    cancel(toast.timer);
+    this.toasts = this.toasts.filter((t) => t !== toast);
+    if (this.toasts.length === 0) {
+      this.stopListening();
+    }
+  }
+
+  dismissAll() {
+    this.toasts.forEach((t) => cancel(t.timer));
+    this.toasts = [];
+    this.stopListening();
+  }
+
+  <template>
+    {{#if this.toasts.length}}
+      <div class="jtech-popup-toasts">
+        {{#each this.toasts key="key" as |toast|}}
+          <div
+            class="jtech-popup-toast"
+            role="button"
+            tabindex="0"
+            {{on "click" (fn this.open toast)}}
+          >
+            <div class="jtech-popup-toast__avatar">
+              {{#if toast.avatarUrl}}
+                <img src={{toast.avatarUrl}} width="44" height="44" alt="" />
+                <span class="jtech-popup-toast__type-badge">
+                  {{icon toast.icon}}
+                </span>
+              {{else}}
+                <span class="jtech-popup-toast__type-icon">
+                  {{icon toast.icon}}
+                </span>
+              {{/if}}
+            </div>
+            <div class="jtech-popup-toast__body">
+              <div class="jtech-popup-toast__heading">
+                <span class="jtech-popup-toast__name">{{toast.name}}</span>
+                <span class="jtech-popup-toast__action">—
+                  {{toast.action}}</span>
+              </div>
+              {{#if toast.title}}
+                <div class="jtech-popup-toast__title">{{toast.title}}</div>
+              {{/if}}
+              {{#if toast.excerpt}}
+                <div class="jtech-popup-toast__excerpt">{{toast.excerpt}}</div>
+              {{/if}}
+            </div>
+          </div>
+        {{/each}}
+      </div>
+    {{/if}}
+  </template>
+}
diff --git a/assets/javascripts/discourse/connectors/user-preferences-account/jtech-desktop-popup-notifications.gjs b/assets/javascripts/discourse/connectors/user-preferences-account/jtech-desktop-popup-notifications.gjs
new file mode 100644
index 0000000..3816799
--- /dev/null
+++ b/assets/javascripts/discourse/connectors/user-preferences-account/jtech-desktop-popup-notifications.gjs
@@ -0,0 +1,78 @@
+import Component from "@glimmer/component";
+import { action } from "@ember/object";
+import { service } from "@ember/service";
+import { ajax } from "discourse/lib/ajax";
+import { popupAjaxError } from "discourse/lib/ajax-error";
+import { i18n } from "discourse-i18n";
+import ComboBox from "select-kit/components/combo-box";
+
+// "Desktop Pop Up Notifications" On/Off dropdown on the account preferences
+// page (/u/:username/preferences/account). Rendered into the
+// `user-preferences-account` outlet.
+//
+// It saves immediately on change with a PUT to /u/:username.json (the
+// `jtech_popup_notifications_enabled` custom field is registered editable
+// server-side), rather than depending on the account form's "Save Changes"
+// button — the account controller does not persist arbitrary custom fields,
+// and an instant toggle is the expected UX here anyway. The value is also
+// mirrored onto the current user so the running toast subscriber honors the
+// change without a reload.
+//
+// Default is OFF: the current-user serializer resolves the effective value
+// from `popup_notifications_default_enabled` (false) until the user opts in,
+// so the pop-up never surprises the whole forum.
+export default class JtechDesktopPopupNotifications extends Component {
+  @service siteSettings;
+  @service currentUser;
+
+  get available() {
+    return this.siteSettings.popup_notifications_enabled;
+  }
+
+  get enabled() {
+    return !!this.currentUser?.jtech_popup_notifications_enabled;
+  }
+
+  get content() {
+    return [
+      { id: true, name: i18n("jtech_popup_notifications.preference.on") },
+      { id: false, name: i18n("jtech_popup_notifications.preference.off") },
+    ];
+  }
+
+  @action
+  async onChange(value) {
+    const previous = this.enabled;
+    // Optimistic + live gate for the running toast subscriber.
+    this.currentUser.set("jtech_popup_notifications_enabled", value);
+    try {
+      await ajax(`/u/${this.currentUser.username}.json`, {
+        type: "PUT",
+        data: { custom_fields: { jtech_popup_notifications_enabled: value } },
+      });
+    } catch (error) {
+      this.currentUser.set("jtech_popup_notifications_enabled", previous);
+      popupAjaxError(error);
+    }
+  }
+
+  <template>
+    {{#if this.available}}
+      <div class="control-group jtech-desktop-popup-notifications">
+        <label class="control-label">
+          {{i18n "jtech_popup_notifications.preference.title"}}
+        </label>
+        <div class="controls">
+          <ComboBox
+            @content={{this.content}}
+            @value={{this.enabled}}
+            @onChange={{this.onChange}}
+          />
+          <div class="instructions">
+            {{i18n "jtech_popup_notifications.preference.instructions"}}
+          </div>
+        </div>
+      </div>
+    {{/if}}
+  </template>
+}
diff --git a/assets/javascripts/discourse/initializers/jtech-popup-notifications.js b/assets/javascripts/discourse/initializers/jtech-popup-notifications.js
new file mode 100644
index 0000000..5976703
--- /dev/null
+++ b/assets/javascripts/discourse/initializers/jtech-popup-notifications.js
@@ -0,0 +1,22 @@
+import { withPluginApi } from "discourse/lib/plugin-api";
+import JtechPopupNotification from "../components/jtech-popup-notification";
+
+// Mounts the desktop pop-up notification host once, globally, into the
+// always-present `above-footer` outlet. The component itself gates on
+// desktop-only + the per-user preference + the site setting, so mounting
+// it is cheap and inert when the feature is off. Skipped entirely when the
+// master switch is off so no MessageBus subscription is even created.
+export default {
+  name: "jtech-desktop-popup-notifications",
+
+  initialize(container) {
+    const siteSettings = container.lookup("service:site-settings");
+    if (!siteSettings.popup_notifications_enabled) {
+      return;
+    }
+
+    withPluginApi("1.0", (api) => {
+      api.renderInOutlet("above-footer", JtechPopupNotification);
+    });
+  },
+};
diff --git a/assets/stylesheets/popup-notifications.scss b/assets/stylesheets/popup-notifications.scss
new file mode 100644
index 0000000..9e9a81e
--- /dev/null
+++ b/assets/stylesheets/popup-notifications.scss
@@ -0,0 +1,147 @@
+// Desktop pop-up notification toast — a Jelly-style card anchored top-right,
+// just below the header (and its search icon). Theme-aware: uses the active
+// theme's surface colors so it looks native in both light and dark themes.
+//
+// Rendered by assets/javascripts/discourse/components/jtech-popup-notification.gjs
+// into the always-present `above-footer` outlet; fixed positioning lifts it
+// out of the footer to the top-right of the viewport.
+// Fixed stack anchored top-right, just below the header. Newest card first;
+// older cards flow downward.
+.jtech-popup-toasts {
+  position: fixed;
+  top: calc(var(--header-offset, 60px) + 10px);
+  right: 14px;
+  z-index: 1080;
+  display: flex;
+  flex-direction: column;
+  gap: 10px;
+  max-width: calc(100vw - 28px);
+}
+
+.jtech-popup-toast {
+  display: flex;
+  gap: 12px;
+  align-items: flex-start;
+  box-sizing: border-box;
+  width: 360px;
+  max-width: 100%;
+  padding: 14px 16px;
+  background: var(--secondary);
+  color: var(--primary);
+  border: 1px solid var(--primary-low);
+  border-radius: 12px;
+  box-shadow: 0 8px 28px rgba(0, 0, 0, 0.22);
+  cursor: pointer;
+  animation: jtech-popup-toast-in 160ms ease-out;
+
+  &:hover {
+    border-color: var(--primary-medium);
+  }
+
+  // Avatar column, with a small type-icon badge pinned to its top-right
+  // corner. When there is no source post (e.g. a flag note) there is no
+  // avatar, so the type icon renders on its own at avatar size instead.
+  &__avatar {
+    position: relative;
+    flex: 0 0 auto;
+    width: 44px;
+    height: 44px;
+
+    img {
+      display: block;
+      width: 44px;
+      height: 44px;
+      border-radius: 50%;
+    }
+  }
+
+  &__type-badge {
+    position: absolute;
+    top: -3px;
+    right: -3px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    width: 20px;
+    height: 20px;
+    border-radius: 50%;
+    background: var(--tertiary);
+    color: var(--secondary);
+    border: 2px solid var(--secondary);
+
+    .d-icon {
+      width: 0.7em;
+      height: 0.7em;
+      font-size: 0.7em;
+    }
+  }
+
+  &__type-icon {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    width: 44px;
+    height: 44px;
+    border-radius: 50%;
+    background: var(--tertiary-low);
+
+    .d-icon {
+      font-size: 1.5em;
+      color: var(--tertiary);
+    }
+  }
+
+  &__body {
+    min-width: 0; // allow the ellipsis on the title to work inside flex
+  }
+
+  // Top line: "Name — Action" (e.g. "pat — Liked your post").
+  &__heading {
+    font-size: var(--font-0);
+    line-height: 1.2;
+  }
+
+  &__name {
+    font-weight: 700;
+  }
+
+  &__action {
+    color: var(--primary-medium);
+  }
+
+  // Middle line: topic title, bold.
+  &__title {
+    margin-top: 2px;
+    font-weight: 700;
+    font-size: var(--font-up-1);
+    line-height: 1.25;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+  }
+
+  // Bottom line: a preview of the message, smaller and not bold.
+  &__excerpt {
+    margin-top: 3px;
+    font-weight: 400;
+    font-size: var(--font-down-1);
+    line-height: 1.35;
+    color: var(--primary-high);
+    display: -webkit-box;
+    -webkit-line-clamp: 2;
+    -webkit-box-orient: vertical;
+    overflow: hidden;
+  }
+}
+
+@keyframes jtech-popup-toast-in {
+  from {
+    opacity: 0;
+    transform: translateY(-8px);
+  }
+
+  to {
+    opacity: 1;
+    transform: translateY(0);
+  }
+}
diff --git a/config/locales/client.en.yml b/config/locales/client.en.yml
index d1c5b35..717ffbf 100644
--- a/config/locales/client.en.yml
+++ b/config/locales/client.en.yml
@@ -1,5 +1,34 @@
 en:
   js:
+    jtech_popup_notifications:
+      someone: Someone
+      # Second half of the toast heading line, "Name — <action>".
+      action:
+        replied: Replied
+        mentioned: Mentioned you
+        quoted: Quoted you
+        edited: Edited your post
+        liked: Liked your post
+        messaged: Messaged you
+        posted: Posted
+        linked: Linked your post
+        badge: Granted you a badge
+        whispered: Sent you a whisper
+        post_deleted: Deleted a post
+        post_approved: Approved a post
+        post_rejected: Rejected a post
+        user_note: Added a note on a user
+        flag_note: Added a note on a flag
+        note: Added a moderator note
+        default: Sent you a notification
+      preference:
+        title: Desktop Pop Up Notifications
+        instructions: Show a small pop-up card in the top-right corner when you
+          receive a new notification. Desktop only — this never appears on mobile.
+        # NB: "on"/"off" MUST be quoted — YAML parses bare on/off as booleans,
+        # which would make these i18n keys unreachable.
+        "on": "On"
+        "off": "Off"
     discourse_mod_categories:
       precheck:
         title: Before you post
diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index 4080e3c..bfd2b2e 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -8,6 +8,7 @@ en:
       jtech_mod: Jtech — Mod
       jtech_dumbcourse: Jtech — Dumbcourse
       jtech_smart_search: Jtech — Smart search
+      jtech_popup_notifications: Jtech — Desktop pop-ups
 
     # ── Jtech (master) ─────────────────────────────────────────────────────
     jtech_enabled: Enable the Jtech plugin bundle
@@ -172,6 +173,21 @@ en:
       extra SQL query; raising this gives broader matches but slower
       search. Range 1–5.
 
+    # ── Jtech — Desktop pop-ups ────────────────────────────────────────────
+    popup_notifications_enabled: Enable desktop pop-up notifications
+    popup_notifications_enabled_description: Master switch for the Jelly-style
+      pop-up notification card (top-right, desktop only). When off, no card
+      appears for anyone and the per-user preference is hidden. This is purely
+      additive — it never changes the bell counter, the notifications dropdown,
+      or read state.
+    popup_notifications_default_enabled: Pop-ups on by default
+    popup_notifications_default_enabled_description: The default for users who
+      have not chosen on their account page. Off by design, so enabling the
+      plugin never surprises the whole forum — each user opts in themselves.
+    popup_notifications_timeout_seconds: Pop-up auto-dismiss (seconds)
+    popup_notifications_timeout_seconds_description: How long the card stays on
+      screen before dismissing itself. Clicking anywhere else also dismisses it.
+
     # ── Jtech — Dumbcourse ─────────────────────────────────────────────────
     dumbcourse_enabled: Enable Dumbcourse
     dumbcourse_enabled_description: Serves the Dumbcourse SPA under the
diff --git a/config/settings.yml b/config/settings.yml
index 995689e..0df0f2e 100644
--- a/config/settings.yml
+++ b/config/settings.yml
@@ -182,6 +182,28 @@ jtech_smart_search:
     min: 1
     max: 5
 
+# ───────────────────────────────────────────────────────────────────────────
+# Jtech — Desktop pop-up notifications (Jelly-style toast, desktop only)
+# ───────────────────────────────────────────────────────────────────────────
+jtech_popup_notifications:
+  # Master switch. When off, no toast fires for anyone and the per-user
+  # preference on the account page is hidden.
+  popup_notifications_enabled:
+    default: true
+    client: true
+  # Default for users who have never set the per-user preference. Off by
+  # design — the toast only appears for users who opt in on their account
+  # page, so enabling the plugin never surprises the whole forum.
+  popup_notifications_default_enabled:
+    default: false
+    client: true
+  # Seconds the toast stays on screen before auto-dismissing.
+  popup_notifications_timeout_seconds:
+    default: 20
+    client: true
+    min: 3
+    max: 300
+
 # ───────────────────────────────────────────────────────────────────────────
 # Jtech — Dumbcourse (lightweight SPA at /dumb with push notifications)
 # ───────────────────────────────────────────────────────────────────────────
diff --git a/plugin.rb b/plugin.rb
index 1bd0005..60f220f 100644
--- a/plugin.rb
+++ b/plugin.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # name: jtech-tools
-# about: Jtech — combined Discourse plugin (dislike, another-smtp, mini-mod, mod-categories, dumbcourse, translator-tweaks, smart-search)
+# about: Jtech — combined Discourse plugin (dislike, another-smtp, mini-mod, mod-categories, dumbcourse, translator-tweaks, smart-search, popup-notifications)
 # version: 0.1.1
 # authors: TripleU, Shalom_Karr, Ars18
 # url: https://github.com/JTech-Forums/JtechTools
@@ -36,6 +36,7 @@
   dumbcourse
   translator_tweaks
   smart_search
+  popup_notifications
 ].each do |sub|
   path = File.expand_path("sub_plugins/#{sub}.rb", __dir__)
   instance_eval(File.read(path), path, 1)
diff --git a/spec/requests/popup_notifications_pref_spec.rb b/spec/requests/popup_notifications_pref_spec.rb
new file mode 100644
index 0000000..6227acd
--- /dev/null
+++ b/spec/requests/popup_notifications_pref_spec.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+# Backend contract for the "Desktop Pop Up Notifications" preference: the
+# per-user custom field is editable, off by default, and surfaced on the
+# current-user serializer as an effective (default-aware) boolean. This is
+# the server side of the additive feature — it changes nothing about how
+# core notifications are created or delivered.
+RSpec.describe "Desktop pop-up notification preference" do
+  fab!(:user)
+
+  let(:field) { DiscoursePopupNotifications::USER_ENABLED_FIELD }
+
+  before do
+    SiteSetting.popup_notifications_enabled = true
+    SiteSetting.popup_notifications_default_enabled = false
+  end
+
+  def current_user_json
+    sign_in(user)
+    get "/session/current.json"
+    expect(response.status).to eq(200)
+    response.parsed_body["current_user"]
+  end
+
+  it "defaults to the site default (off) when the user has not chosen" do
+    expect(current_user_json["jtech_popup_notifications_enabled"]).to eq(false)
+  end
+
+  it "follows the site default when that default is on" do
+    SiteSetting.popup_notifications_default_enabled = true
+    expect(current_user_json["jtech_popup_notifications_enabled"]).to eq(true)
+  end
+
+  it "reflects an explicit per-user opt-in" do
+    user.custom_fields[field] = true
+    user.save_custom_fields(true)
+    expect(current_user_json["jtech_popup_notifications_enabled"]).to eq(true)
+  end
+
+  it "reflects an explicit per-user opt-out even when the default is on" do
+    SiteSetting.popup_notifications_default_enabled = true
+    user.custom_fields[field] = false
+    user.save_custom_fields(true)
+    expect(current_user_json["jtech_popup_notifications_enabled"]).to eq(false)
+  end
+
+  it "persists the field through a preferences update (registered editable)" do
+    sign_in(user)
+    put "/u/#{user.username}.json", params: { custom_fields: { field => true } }
+    expect(response.status).to eq(200)
+    expect(user.reload.custom_fields[field]).to eq(true)
+  end
+end
diff --git a/spec/system/popup_notifications_click_through_spec.rb b/spec/system/popup_notifications_click_through_spec.rb
new file mode 100644
index 0000000..8320dd4
--- /dev/null
+++ b/spec/system/popup_notifications_click_through_spec.rb
@@ -0,0 +1,155 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+# Click-through coverage: while the user is on one topic, a notification about
+# a post in a DIFFERENT topic pops the toast; clicking the card opens that
+# other topic at the post (exactly like clicking the row in the notifications
+# dropdown) and the card goes away on click.
+#
+# 30 examples — 5 notification types across 6 fresh target topics each. Batch
+# 1 also captures before/after screenshots (toast on the home topic, then the
+# opened target) for the gallery.
+#
+# Each example loads the home topic fresh and publishes one crafted
+# notification (retried until it lands) on the `/notification/:id` channel.
+RSpec.describe "Desktop pop-up notification click-through" do
+  fab!(:author) { Fabricate(:user, username: "poster_pat") }
+  fab!(:recipient) { Fabricate(:user, username: "reader_rhea") }
+  fab!(:category) { Fabricate(:category, name: "Flip phones") }
+  fab!(:home_topic) do
+    Fabricate(:topic, category: category, user: recipient, title: "The thread I am reading")
+  end
+  fab!(:home_op) do
+    Fabricate(
+      :post,
+      topic: home_topic,
+      user: recipient,
+      raw: "Where I am when the notification arrives.",
+    )
+  end
+
+  let(:user_field) { DiscoursePopupNotifications::USER_ENABLED_FIELD }
+  let(:id_seq) { [800_000] }
+
+  # Gallery/behavioral spec: runs in the Feature Screenshots workflow (which
+  # sets this env). Skipped in the main parallel system_tests run so its 30
+  # browser navigations do not weigh that job down — core click-through is
+  # covered by popup_notifications_spec.rb.
+  before { skip("screenshot-gallery only") unless ENV["JTECH_SCREENSHOT_GALLERY"] }
+
+  before do
+    SiteSetting.popup_notifications_enabled = true
+    SiteSetting.popup_notifications_timeout_seconds = 300
+    SiteSetting.auto_silence_fast_typers_on_first_post = false
+    recipient.custom_fields[user_field] = true
+    recipient.save_custom_fields(true)
+    sign_in(recipient)
+  end
+
+  def shot(name)
+    begin
+      Timeout.timeout(8) do
+        sleep 0.1 until page.evaluate_script("Array.from(document.images).every((i) => i.complete)")
+      end
+    rescue Timeout::Error
+      # Capture anyway rather than fail over a slow image.
+    end
+    page.save_screenshot("popup_notifications_#{name}.png")
+  end
+
+  def push(type:, data:, topic_id: nil, post_number: nil, fancy_title: nil, slug: nil)
+    id_seq[0] += 1
+    MessageBus.publish(
+      "/notification/#{recipient.id}",
+      {
+        unread_notifications: 1,
+        all_unread_notifications_count: 1,
+        last_notification: {
+          notification: {
+            id: id_seq[0],
+            user_id: recipient.id,
+            notification_type: Notification.types[type],
+            read: false,
+            created_at: Time.zone.now.iso8601,
+            post_number: post_number,
+            topic_id: topic_id,
+            fancy_title: fancy_title,
+            slug: slug,
+            data: data,
+          },
+        },
+      },
+      user_ids: [recipient.id],
+    )
+  end
+
+  def wait_for_toast
+    8.times do
+      yield
+      return if page.has_css?(".jtech-popup-toast", wait: 1.5)
+    end
+    expect(page).to have_css(".jtech-popup-toast", wait: 5)
+  end
+
+  def visit_home
+    visit("/t/#{home_topic.slug}/#{home_topic.id}")
+    expect(page).to have_css("#post_1", wait: 10)
+  end
+
+  (1..6).each do |batch|
+    %i[replied mentioned quoted liked private_message].each do |type|
+      it "clicking a #{type} toast opens its topic and dismisses (batch #{batch})" do
+        target =
+          Fabricate(
+            :topic,
+            category: category,
+            user: recipient,
+            title: "Another topic #{batch} for a #{type} notification",
+          )
+        Fabricate(
+          :post,
+          topic: target,
+          user: recipient,
+          raw: "The opening post of the other topic.",
+        )
+        target_reply =
+          Fabricate(
+            :post,
+            topic: target,
+            user: author,
+            raw: "The reply on the other topic that triggered the #{type} notification.",
+          )
+
+        visit_home
+
+        wait_for_toast do
+          push(
+            type: type,
+            topic_id: target.id,
+            post_number: target_reply.post_number,
+            slug: target.slug,
+            fancy_title: target.fancy_title,
+            data: {
+              display_username: author.username,
+              topic_title: target.title,
+              original_post_id: target_reply.id,
+            },
+          )
+        end
+
+        # It pops while we are still on the home topic.
+        expect(page).to have_current_path(%r{/t/[^/]+/#{home_topic.id}})
+        shot("clickthrough_#{type}_01_toast_on_home") if batch == 1
+
+        find(".jtech-popup-toast").click
+
+        # Clicking opens the OTHER topic at the post, and the card is gone.
+        expect(page).to have_current_path(%r{/t/[^/]+/#{target.id}}, wait: 10)
+        expect(page).to have_css("#post_#{target_reply.post_number}", wait: 10)
+        expect(page).to have_no_css(".jtech-popup-toast")
+        shot("clickthrough_#{type}_02_opened_target") if batch == 1
+      end
+    end
+  end
+end
diff --git a/spec/system/popup_notifications_screenshots_spec.rb b/spec/system/popup_notifications_screenshots_spec.rb
new file mode 100644
index 0000000..9b28e23
--- /dev/null
+++ b/spec/system/popup_notifications_screenshots_spec.rb
@@ -0,0 +1,316 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+# Screenshot gallery for the desktop pop-up notification feature — 18 shots
+# across the two surfaces the user interacts with:
+#
+#   * the account page where the preference is set (shots 01–04), plus the
+#     admin master switch (05) and the control hidden when the master is off
+#     (06); and
+#   * the page where the notification arrives — the toast itself, across
+#     notification types (07–11), content shapes (12–14), the off state (15),
+#     and the plugin's own custom types: whisper, flag, pending (16–18).
+#
+# Each toast shot loads the page fresh and publishes exactly ONE crafted
+# notification on the user's `/notification/:id` MessageBus channel (the same
+# channel core uses). One publish per fresh page is the reliable path in the
+# parallel system-test runner. The real end-to-end delivery is covered by
+# spec/system/popup_notifications_spec.rb.
+#
+# Screenshots land in tmp/capybara/ and are published as the CI artifact.
+RSpec.describe "Desktop pop-up notification screenshots" do
+  fab!(:author) { Fabricate(:user, username: "poster_pat", name: "Pat Poster") }
+  fab!(:recipient) { Fabricate(:user, username: "reader_rhea") }
+  fab!(:admin) { Fabricate(:admin, username: "admin_amy") }
+  fab!(:category) { Fabricate(:category, name: "Flip phones") }
+  fab!(:topic) do
+    Fabricate(
+      :topic,
+      category: category,
+      user: recipient,
+      title: "Might be the next Qin but better",
+    )
+  end
+  fab!(:op) do
+    Fabricate(:post, topic: topic, user: recipient, raw: "What do you all think of this phone?")
+  end
+  fab!(:reply_post) do
+    Fabricate(
+      :post,
+      topic: topic,
+      user: author,
+      raw:
+        "Excellent screen quality. Supports 4g volte in Israel with excellent cellular reception.",
+    )
+  end
+  fab!(:long_reply) do
+    Fabricate(
+      :post,
+      topic: topic,
+      user: author,
+      raw:
+        "Honestly this might be the best budget option out there right now — the build feels " \
+          "premium, the screen is bright even outdoors, calls are crystal clear on 4G VoLTE, and " \
+          "the battery genuinely lasts a day and a half of heavy use without needing a top-up.",
+    )
+  end
+  fab!(:long_topic) do
+    Fabricate(
+      :topic,
+      category: category,
+      user: recipient,
+      title:
+        "A remarkably and unnecessarily long topic title that should be truncated with an " \
+          "ellipsis inside the pop-up card so it never wraps onto a second line",
+    )
+  end
+  fab!(:long_topic_reply) do
+    Fabricate(:post, topic: long_topic, user: author, raw: "See the specs I linked above.")
+  end
+
+  let(:user_field) { DiscoursePopupNotifications::USER_ENABLED_FIELD }
+  # Mutable memoized counter (avoids an instance variable) so every crafted
+  # notification gets a fresh id.
+  let(:id_seq) { [500_000] }
+
+  # Gallery spec: generates screenshots in the Feature Screenshots workflow
+  # (which sets this env). Skipped in the main parallel system_tests run so it
+  # does not weigh that job down — core behavior is covered by
+  # popup_notifications_spec.rb.
+  before { skip("screenshot-gallery only") unless ENV["JTECH_SCREENSHOT_GALLERY"] }
+
+  before do
+    SiteSetting.popup_notifications_enabled = true
+    SiteSetting.popup_notifications_timeout_seconds = 300 # keep the card up long enough to shoot
+    SiteSetting.auto_silence_fast_typers_on_first_post = false
+    recipient.custom_fields[user_field] = true
+    recipient.save_custom_fields(true)
+  end
+
+  def shot(name)
+    begin
+      Timeout.timeout(8) do
+        sleep 0.1 until page.evaluate_script("Array.from(document.images).every((i) => i.complete)")
+      end
+    rescue Timeout::Error
+      # Capture anyway rather than fail over a slow avatar image.
+    end
+    page.save_screenshot("popup_notifications_#{name}.png")
+  end
+
+  def set_pref(value)
+    recipient.custom_fields[user_field] = value
+    recipient.save_custom_fields(true)
+  end
+
+  # Publish a crafted notification on the recipient's channel.
+  def push(type:, data:, topic_id: nil, post_number: nil, fancy_title: nil, slug: nil)
+    id_seq[0] += 1
+    payload = {
+      unread_notifications: 1,
+      all_unread_notifications_count: 1,
+      last_notification: {
+        notification: {
+          id: id_seq[0],
+          user_id: recipient.id,
+          notification_type: Notification.types[type],
+          read: false,
+          high_priority: false,
+          created_at: Time.zone.now.iso8601,
+          post_number: post_number,
+          topic_id: topic_id,
+          fancy_title: fancy_title,
+          slug: slug,
+          data: data,
+        },
+      },
+    }
+    MessageBus.publish("/notification/#{recipient.id}", payload, user_ids: [recipient.id])
+  end
+
+  # A reply-shaped notification enriched from a real post (avatar + excerpt),
+  # varying only the type so each screenshot is a distinct kind.
+  def push_from_post(type:, post:, into: topic)
+    push(
+      type: type,
+      topic_id: into.id,
+      post_number: post.post_number,
+      slug: into.slug,
+      fancy_title: into.fancy_title,
+      data: {
+        display_username: post.user.username,
+        topic_title: into.title,
+        original_post_id: post.id,
+      },
+    )
+  end
+
+  def visit_topic(into = topic)
+    visit("/t/#{into.slug}/#{into.id}")
+    expect(page).to have_css("#post_1", wait: 10)
+  end
+
+  # After a warm page load `#post_1` can appear before the browser's
+  # MessageBus poll re-establishes its subscription, so a single publish can
+  # land before the client is listening and be missed. Re-publish (a fresh id
+  # each time) until the toast — or a specific icon within it — appears.
+  def wait_for_toast(selector = ".jtech-popup-toast")
+    8.times do
+      yield
+      return if page.has_css?(selector, wait: 1.5)
+    end
+    expect(page).to have_css(selector, wait: 5)
+  end
+
+  # One shot = one fresh page + a publish (retried until it lands).
+  def enriched_toast_shot(name, type:, post: reply_post, into: topic)
+    visit_topic(into)
+    wait_for_toast { push_from_post(type: type, post: post, into: into) }
+    shot(name)
+  end
+
+  def open_account_preference
+    sign_in(recipient)
+    visit("/u/#{recipient.username}/preferences/account")
+    expect(page).to have_css(".jtech-desktop-popup-notifications", wait: 10)
+  end
+
+  it "captures the account-page preference control (01–04)" do
+    open_account_preference
+    shot("01_settings_account_default_off")
+
+    find(".jtech-desktop-popup-notifications .select-kit-header").click
+    expect(page).to have_css(".select-kit-collection", wait: 5)
+    shot("02_settings_dropdown_open")
+
+    find(".select-kit-row", text: "On").click
+    expect(page).to have_css(".jtech-desktop-popup-notifications")
+    shot("03_settings_set_on")
+
+    find(".jtech-desktop-popup-notifications .select-kit-header").click
+    find(".select-kit-row", text: "Off").click
+    shot("04_settings_set_off")
+  end
+
+  it "captures the admin master switch (05)" do
+    sign_in(admin)
+    visit("/admin/site_settings/category/all_results?filter=popup_notifications")
+    expect(page).to have_css(".setting", wait: 10)
+    shot("05_settings_admin_master_switch")
+  end
+
+  it "hides the account control when the master switch is off (06)" do
+    SiteSetting.popup_notifications_enabled = false
+    sign_in(recipient)
+    visit("/u/#{recipient.username}/preferences/account")
+    expect(page).to have_css(".user-preferences", wait: 10)
+    expect(page).to have_no_css(".jtech-desktop-popup-notifications")
+    shot("06_settings_control_hidden_master_off")
+  end
+
+  it "captures a toast for each notification type (07–11)" do
+    sign_in(recipient)
+    enriched_toast_shot("07_toast_reply", type: :replied)
+    enriched_toast_shot("08_toast_mention", type: :mentioned)
+    enriched_toast_shot("09_toast_quote", type: :quoted)
+    enriched_toast_shot("10_toast_private_message", type: :private_message)
+    enriched_toast_shot("11_toast_liked", type: :liked)
+  end
+
+  it "captures content-shape variety: long title, long message, icon fallback (12–14)" do
+    sign_in(recipient)
+
+    # Long topic title → ellipsis on the bold title line.
+    enriched_toast_shot(
+      "12_toast_long_title",
+      type: :replied,
+      post: long_topic_reply,
+      into: long_topic,
+    )
+
+    # Long message → the preview line clamps to two lines.
+    enriched_toast_shot("13_toast_long_message", type: :replied, post: long_reply)
+
+    # No source post → the type icon renders on its own, preview from data.
+    visit_topic
+    wait_for_toast(".jtech-popup-toast .d-icon-bell") do
+      push(
+        type: :custom,
+        data: {
+          display_username: "system_sam",
+          topic_title: "Scheduled maintenance tonight",
+          excerpt: "The forum will be briefly unavailable around 2am for a database upgrade.",
+          url: "/u/#{recipient.username}/notifications",
+        },
+      )
+    end
+    shot("14_toast_fallback_icon")
+  end
+
+  it "shows nothing extra when the preference is off (15)" do
+    set_pref(false)
+    sign_in(recipient)
+    visit_topic
+
+    push_from_post(type: :replied, post: reply_post)
+    expect(page).to have_no_css(".jtech-popup-toast", wait: 5)
+    shot("15_notification_off_no_popup")
+  end
+
+  it "captures the plugin's custom types: whisper, flag, pending (16–18)" do
+    sign_in(recipient)
+
+    # Moderator whisper — enriched from a real post, with the eye badge.
+    visit_topic
+    wait_for_toast(".jtech-popup-toast .d-icon-eye") do
+      push(
+        type: :custom,
+        topic_id: topic.id,
+        post_number: reply_post.post_number,
+        slug: topic.slug,
+        fancy_title: topic.fancy_title,
+        data: {
+          mod_whisper: true,
+          display_username: author.username,
+          topic_title: topic.title,
+          original_post_id: reply_post.id,
+        },
+      )
+    end
+    shot("16_toast_whisper")
+
+    # Flag note — no source post, so the flag type icon renders on its own.
+    visit_topic
+    wait_for_toast(".jtech-popup-toast .d-icon-flag") do
+      push(
+        type: :custom,
+        data: {
+          mod_note: true,
+          mod_note_kind: "flag_note",
+          display_username: "mod_mia",
+          excerpt: "Flagged as spam — please review.",
+          url: "/review",
+        },
+      )
+    end
+    shot("17_toast_flag")
+
+    # Queued / pending post approved by staff.
+    visit_topic
+    wait_for_toast(".jtech-popup-toast .d-icon-check") do
+      push(
+        type: :custom,
+        data: {
+          mod_note: true,
+          mod_note_kind: "post_approved",
+          display_username: "mod_mia",
+          topic_title: topic.title,
+          excerpt: "Approved a post that was awaiting review.",
+          url: "/review",
+        },
+      )
+    end
+    shot("18_toast_pending_approved")
+  end
+end
diff --git a/spec/system/popup_notifications_spec.rb b/spec/system/popup_notifications_spec.rb
new file mode 100644
index 0000000..821f41f
--- /dev/null
+++ b/spec/system/popup_notifications_spec.rb
@@ -0,0 +1,144 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+# Behavioral coverage for the desktop pop-up notification toast.
+#
+# The toast is PURELY ADDITIVE: it subscribes to the same
+# `/notification/:id` MessageBus channel core already publishes on and
+# renders a card — it never touches core notification code, the bell, the
+# dropdown, or read-state. So "regular notifications are unchanged" holds by
+# construction; these examples prove the toast itself:
+#
+#   * OFF (the default): a published notification produces NO toast.
+#   * ON: the same notification pops the toast (name + action + title), and
+#     clicking it routes to the post like the dropdown row.
+#   * Clicking elsewhere dismisses it.
+#
+# Each example loads the page fresh and publishes exactly one crafted
+# notification on the channel — the same delivery core uses — which is the
+# reliable path in the parallel system-test runner (a real reply would rely
+# on PostAlerter running inline, which it does not here).
+RSpec.describe "Desktop pop-up notifications" do
+  fab!(:author) { Fabricate(:user, username: "poster_pat") }
+  fab!(:recipient) { Fabricate(:user, username: "reader_rhea") }
+  fab!(:category)
+  fab!(:topic) do
+    Fabricate(
+      :topic,
+      category: category,
+      user: recipient,
+      title: "Might be the next Qin but better",
+    )
+  end
+  fab!(:op) do
+    Fabricate(:post, topic: topic, user: recipient, raw: "What do you all think of this phone?")
+  end
+  fab!(:reply_post) do
+    Fabricate(
+      :post,
+      topic: topic,
+      user: author,
+      raw:
+        "Excellent screen quality. Supports 4g volte in Israel with excellent cellular reception.",
+    )
+  end
+
+  let(:user_field) { DiscoursePopupNotifications::USER_ENABLED_FIELD }
+
+  before do
+    SiteSetting.popup_notifications_enabled = true
+    SiteSetting.popup_notifications_timeout_seconds = 300
+    SiteSetting.auto_silence_fast_typers_on_first_post = false
+  end
+
+  def set_pref(value)
+    recipient.custom_fields[user_field] = value
+    recipient.save_custom_fields(true)
+  end
+
+  # Publish a reply-shaped notification for the recipient — the browser is
+  # subscribed to this channel, so the toast renders it.
+  def publish_reply
+    MessageBus.publish(
+      "/notification/#{recipient.id}",
+      {
+        unread_notifications: 1,
+        all_unread_notifications_count: 1,
+        last_notification: {
+          notification: {
+            id: 900_001,
+            user_id: recipient.id,
+            notification_type: Notification.types[:replied],
+            read: false,
+            created_at: Time.zone.now.iso8601,
+            topic_id: topic.id,
+            post_number: reply_post.post_number,
+            slug: topic.slug,
+            fancy_title: topic.fancy_title,
+            data: {
+              display_username: author.username,
+              topic_title: topic.title,
+              original_post_id: reply_post.id,
+            },
+          },
+        },
+      },
+      user_ids: [recipient.id],
+    )
+  end
+
+  def open_topic
+    visit("/t/#{topic.slug}/#{topic.id}")
+    expect(page).to have_css("#post_1", wait: 10)
+  end
+
+  # Re-publish (fresh id each time) until the toast appears, in case the
+  # browser's MessageBus poll is not yet listening when the first publish
+  # lands.
+  def publish_reply_until_toast
+    8.times do
+      publish_reply
+      return if page.has_css?(".jtech-popup-toast", wait: 1.5)
+    end
+    expect(page).to have_css(".jtech-popup-toast", wait: 5)
+  end
+
+  it "pops the toast when the preference is on" do
+    set_pref(true)
+    sign_in(recipient)
+    open_topic
+
+    publish_reply_until_toast
+
+    expect(page).to have_css(".jtech-popup-toast__name", text: author.username)
+    expect(page).to have_css(".jtech-popup-toast__action", text: "Replied")
+    expect(page).to have_css(".jtech-popup-toast__title", text: topic.title)
+
+    # Clicking the toast routes to the replied post, like the dropdown row.
+    find(".jtech-popup-toast").click
+    expect(page).to have_css("#post_#{reply_post.post_number}", wait: 10)
+    expect(page).to have_no_css(".jtech-popup-toast")
+  end
+
+  it "does not pop the toast when the preference is off (the default)" do
+    set_pref(false)
+    sign_in(recipient)
+    open_topic
+
+    publish_reply
+
+    expect(page).to have_no_css(".jtech-popup-toast", wait: 5)
+  end
+
+  it "dismisses when clicking anywhere else" do
+    set_pref(true)
+    sign_in(recipient)
+    open_topic
+
+    publish_reply_until_toast
+
+    find("#post_1 .cooked").click
+    expect(page).to have_no_css(".jtech-popup-toast")
+  end
+end
diff --git a/spec/system/popup_notifications_stacking_screenshots_spec.rb b/spec/system/popup_notifications_stacking_screenshots_spec.rb
new file mode 100644
index 0000000..665ac52
--- /dev/null
+++ b/spec/system/popup_notifications_stacking_screenshots_spec.rb
@@ -0,0 +1,388 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+# Screenshot gallery for STACKING — when more than one notification arrives,
+# the cards stack one below another (newest on top, just below the header
+# search), up to 3 at once; a 4th drops the oldest (bottom) card so the newest
+# can take its place. 25 shots across single/double/triple stacks, type mixes,
+# content shapes, and the overflow-replaces-oldest behavior.
+#
+# Each shot is its own example (fresh browser session) so a single flaky
+# capture never aborts the others. Within an example the channel is "primed"
+# (publish + wait + dismiss) before the stack is built one card at a time,
+# waiting for the exact card count each step.
+#
+# Screenshots land in tmp/capybara/ and are published as the CI artifact.
+RSpec.describe "Desktop pop-up notification stacking screenshots" do
+  fab!(:author) { Fabricate(:user, username: "poster_pat", name: "Pat Poster") }
+  fab!(:author2) { Fabricate(:user, username: "quinn_quill", name: "Quinn Quill") }
+  fab!(:recipient) { Fabricate(:user, username: "reader_rhea") }
+  fab!(:category) { Fabricate(:category, name: "Flip phones") }
+  fab!(:topic) do
+    Fabricate(
+      :topic,
+      category: category,
+      user: recipient,
+      title: "Might be the next Qin but better",
+    )
+  end
+  fab!(:op) do
+    Fabricate(:post, topic: topic, user: recipient, raw: "What do you all think of this phone?")
+  end
+  fab!(:reply_post) do
+    Fabricate(
+      :post,
+      topic: topic,
+      user: author,
+      raw:
+        "Excellent screen quality. Supports 4g volte in Israel with excellent cellular reception.",
+    )
+  end
+  fab!(:reply_post2) do
+    Fabricate(:post, topic: topic, user: author2, raw: "Battery life is genuinely impressive too.")
+  end
+  fab!(:long_reply) do
+    Fabricate(
+      :post,
+      topic: topic,
+      user: author,
+      raw:
+        "Honestly this might be the best budget option out there right now — the build feels " \
+          "premium, the screen is bright even outdoors, and the battery lasts a day and a half.",
+    )
+  end
+  fab!(:long_topic) do
+    Fabricate(
+      :topic,
+      category: category,
+      user: recipient,
+      title:
+        "A remarkably and unnecessarily long topic title that should be truncated with an " \
+          "ellipsis inside the pop-up card so it never wraps onto a second line",
+    )
+  end
+  fab!(:long_topic_reply) do
+    Fabricate(:post, topic: long_topic, user: author2, raw: "See the specs I linked above.")
+  end
+
+  let(:user_field) { DiscoursePopupNotifications::USER_ENABLED_FIELD }
+  let(:id_seq) { [700_000] }
+
+  # Gallery spec: generates screenshots in the Feature Screenshots workflow
+  # (which sets this env). Skipped in the main parallel system_tests run so it
+  # does not weigh that job down.
+  before { skip("screenshot-gallery only") unless ENV["JTECH_SCREENSHOT_GALLERY"] }
+
+  before do
+    SiteSetting.popup_notifications_enabled = true
+    SiteSetting.popup_notifications_timeout_seconds = 300
+    SiteSetting.auto_silence_fast_typers_on_first_post = false
+    recipient.custom_fields[user_field] = true
+    recipient.save_custom_fields(true)
+    sign_in(recipient)
+  end
+
+  def shot(name)
+    begin
+      Timeout.timeout(8) do
+        sleep 0.1 until page.evaluate_script("Array.from(document.images).every((i) => i.complete)")
+      end
+    rescue Timeout::Error
+      # Capture anyway rather than fail over a slow avatar image.
+    end
+    page.save_screenshot("popup_notifications_#{name}.png")
+  end
+
+  def push(type:, data:, topic_id: nil, post_number: nil, fancy_title: nil, slug: nil)
+    id_seq[0] += 1
+    MessageBus.publish(
+      "/notification/#{recipient.id}",
+      {
+        unread_notifications: 1,
+        all_unread_notifications_count: 1,
+        last_notification: {
+          notification: {
+            id: id_seq[0],
+            user_id: recipient.id,
+            notification_type: Notification.types[type],
+            read: false,
+            created_at: Time.zone.now.iso8601,
+            post_number: post_number,
+            topic_id: topic_id,
+            fancy_title: fancy_title,
+            slug: slug,
+            data: data,
+          },
+        },
+      },
+      user_ids: [recipient.id],
+    )
+  end
+
+  # Spec builders for the common notification shapes.
+  def enriched(type, post: reply_post, into: topic)
+    {
+      type: type,
+      topic_id: into.id,
+      post_number: post.post_number,
+      slug: into.slug,
+      fancy_title: into.fancy_title,
+      data: {
+        display_username: post.user.username,
+        topic_title: into.title,
+        original_post_id: post.id,
+      },
+    }
+  end
+
+  def whisper(post: reply_post, into: topic)
+    enriched(:custom, post: post, into: into).tap { |h| h[:data][:mod_whisper] = true }
+  end
+
+  def mod_note(kind, username: "mod_mia", excerpt:, title: nil)
+    data = {
+      mod_note: true,
+      mod_note_kind: kind,
+      display_username: username,
+      excerpt: excerpt,
+      url: "/review",
+    }
+    data[:topic_title] = title if title
+    { type: :custom, data: data }
+  end
+
+  def fallback(username: "system_sam", title:, excerpt:)
+    {
+      type: :custom,
+      data: {
+        display_username: username,
+        topic_title: title,
+        excerpt: excerpt,
+        url: "/u/#{recipient.username}/notifications",
+      },
+    }
+  end
+
+  def visit_topic
+    visit("/t/#{topic.slug}/#{topic.id}")
+    expect(page).to have_css("#post_1", wait: 10)
+  end
+
+  # Ensure the browser's MessageBus subscription is live, then clear the stack.
+  def prime
+    8.times do
+      push(**enriched(:replied))
+      break if page.has_css?(".jtech-popup-toast", wait: 1.5)
+    end
+    expect(page).to have_css(".jtech-popup-toast", wait: 5)
+    find("#post_1 .cooked").click
+    expect(page).to have_no_css(".jtech-popup-toast")
+  end
+
+  # Build a stack of up to 3 cards, one publish per card, and screenshot it.
+  def stack_shot(name, *specs)
+    visit_topic
+    prime
+    specs.each_with_index do |spec, index|
+      push(**spec)
+      expect(page).to have_css(".jtech-popup-toast", count: index + 1, wait: 10)
+    end
+    shot(name)
+  end
+
+  # Push more than the cap; the stack settles at 3 with `top_icon` at the top.
+  def overflow_shot(name, specs, top_icon:)
+    visit_topic
+    prime
+    specs.each { |spec| push(**spec) }
+    expect(page).to have_css(".jtech-popup-toast", count: 3, wait: 10)
+    expect(page).to have_css(".jtech-popup-toast:first-child #{top_icon}", wait: 10)
+    shot(name)
+  end
+
+  it "single reply (01)" do
+    stack_shot("stack_01_single_reply", enriched(:replied))
+  end
+
+  it "reply + like (02)" do
+    stack_shot("stack_02_reply_like", enriched(:replied), enriched(:liked))
+  end
+
+  it "reply + mention (03)" do
+    stack_shot("stack_03_reply_mention", enriched(:replied), enriched(:mentioned))
+  end
+
+  it "reply + quote (04)" do
+    stack_shot("stack_04_reply_quote", enriched(:replied), enriched(:quoted))
+  end
+
+  it "pm + reply (05)" do
+    stack_shot("stack_05_pm_reply", enriched(:private_message), enriched(:replied))
+  end
+
+  it "whisper + reply (06)" do
+    stack_shot("stack_06_whisper_reply", whisper, enriched(:replied))
+  end
+
+  it "flag + pending (07)" do
+    stack_shot(
+      "stack_07_flag_pending",
+      mod_note("flag_note", excerpt: "Flagged as spam — please review."),
+      mod_note("post_approved", title: topic.title, excerpt: "Approved a queued reply."),
+    )
+  end
+
+  it "badge + reply (08)" do
+    stack_shot("stack_08_badge_reply", enriched(:granted_badge), enriched(:replied))
+  end
+
+  it "edited + linked (09)" do
+    stack_shot("stack_09_edited_linked", enriched(:edited), enriched(:linked))
+  end
+
+  it "reply + like + mention (10)" do
+    stack_shot(
+      "stack_10_reply_like_mention",
+      enriched(:replied),
+      enriched(:liked),
+      enriched(:mentioned),
+    )
+  end
+
+  it "reply + quote + pm (11)" do
+    stack_shot(
+      "stack_11_reply_quote_pm",
+      enriched(:replied),
+      enriched(:quoted),
+      enriched(:private_message),
+    )
+  end
+
+  it "whisper + flag + pending (12)" do
+    stack_shot(
+      "stack_12_whisper_flag_pending",
+      whisper,
+      mod_note("flag_note", excerpt: "Flagged as off-topic."),
+      mod_note("post_approved", title: topic.title, excerpt: "Approved a queued reply."),
+    )
+  end
+
+  it "three likes (13)" do
+    stack_shot(
+      "stack_13_like_x3",
+      enriched(:liked),
+      enriched(:liked, post: reply_post2),
+      enriched(:liked),
+    )
+  end
+
+  it "mention + quote + reply (14)" do
+    stack_shot(
+      "stack_14_mention_quote_reply",
+      enriched(:mentioned),
+      enriched(:quoted),
+      enriched(:replied),
+    )
+  end
+
+  it "pm + whisper + reply (15)" do
+    stack_shot("stack_15_pm_whisper_reply", enriched(:private_message), whisper, enriched(:replied))
+  end
+
+  it "reply + flag + like (16)" do
+    stack_shot(
+      "stack_16_reply_flag_like",
+      enriched(:replied),
+      mod_note("flag_note", excerpt: "A new flag needs attention."),
+      enriched(:liked),
+    )
+  end
+
+  it "fallback + reply + whisper (17)" do
+    stack_shot(
+      "stack_17_fallback_reply_whisper",
+      fallback(
+        title: "Scheduled maintenance",
+        excerpt: "The forum will be briefly offline at 2am.",
+      ),
+      enriched(:replied),
+      whisper,
+    )
+  end
+
+  it "long title + reply + like (18)" do
+    stack_shot(
+      "stack_18_longtitle_reply_like",
+      enriched(:replied, post: long_topic_reply, into: long_topic),
+      enriched(:replied),
+      enriched(:liked),
+    )
+  end
+
+  it "long message + like + mention (19)" do
+    stack_shot(
+      "stack_19_longmessage_like_mention",
+      enriched(:replied, post: long_reply),
+      enriched(:liked),
+      enriched(:mentioned),
+    )
+  end
+
+  it "badge + pm + reply (20)" do
+    stack_shot(
+      "stack_20_badge_pm_reply",
+      enriched(:granted_badge),
+      enriched(:private_message),
+      enriched(:replied),
+    )
+  end
+
+  it "edited + linked + quote (21)" do
+    stack_shot(
+      "stack_21_edited_linked_quote",
+      enriched(:edited),
+      enriched(:linked),
+      enriched(:quoted),
+    )
+  end
+
+  it "flag + pending + whisper (22)" do
+    stack_shot(
+      "stack_22_flag_pending_whisper",
+      mod_note("flag_note", excerpt: "Flag raised on a reply."),
+      mod_note("post_rejected", title: topic.title, excerpt: "Rejected a queued reply."),
+      whisper,
+    )
+  end
+
+  it "three replies, mixed topics (23)" do
+    stack_shot(
+      "stack_23_three_replies_mixed",
+      enriched(:replied),
+      enriched(:replied, post: reply_post2),
+      enriched(:replied, post: long_topic_reply, into: long_topic),
+    )
+  end
+
+  it "overflow — a 4th engagement notification replaces the oldest (24)" do
+    overflow_shot(
+      "stack_24_overflow_engagement",
+      [enriched(:replied), enriched(:liked), enriched(:mentioned), whisper],
+      top_icon: ".d-icon-eye",
+    )
+  end
+
+  it "overflow — a 4th staff notification replaces the oldest (25)" do
+    overflow_shot(
+      "stack_25_overflow_staff",
+      [
+        whisper,
+        mod_note("flag_note", excerpt: "Flagged for review."),
+        mod_note("post_approved", title: topic.title, excerpt: "Approved a queued reply."),
+        enriched(:liked),
+      ],
+      top_icon: ".d-icon-heart",
+    )
+  end
+end
diff --git a/sub_plugins/popup_notifications.rb b/sub_plugins/popup_notifications.rb
new file mode 100644
index 0000000..0eb6ba4
--- /dev/null
+++ b/sub_plugins/popup_notifications.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+# Jtech sub-plugin: desktop pop-up notifications.
+#
+# Renders an in-browser "toast" card (top-right, just below the header
+# search) when a new notification arrives for the current user — modelled
+# on the Jelly macOS notifier's look and delivery. Delivery reuses the
+# same MessageBus channel Discourse already publishes notification state
+# on (`/notification/:user_id`), so no new server push path is needed.
+#
+# Desktop only: the frontend never subscribes or renders on mobile
+# (`site.mobileView`). Gated per-user by an account-page preference
+# ("Desktop Pop Up Notifications", on/off) stored in a user custom field,
+# and site-wide by `popup_notifications_enabled`.
+#
+# The backend here is deliberately thin — the whole experience is
+# client-side. All this file does is:
+#   * register the per-user boolean custom field + make it editable, and
+#   * expose the effective (default-aware) value on the current-user
+#     serializer so the client can gate on `currentUser.
+#     jtech_popup_notifications_enabled`.
+
+register_asset "stylesheets/popup-notifications.scss"
+
+# Type-badge icons the toast draws on the avatar corner (and the icon-only
+# fallback for postless notifications). Registered so they land in the SVG
+# sprite; some are core, some are shared with mod-categories.
+%w[
+  at
+  reply
+  quote-right
+  pencil
+  heart
+  envelope
+  link
+  certificate
+  check
+  xmark
+  trash-can
+  flag
+  eye
+  shield-halved
+  bell
+].each { |name| register_svg_icon(name) }
+
+module ::DiscoursePopupNotifications
+  # Per-user preference. Key PRESENCE + value decides; when the field is
+  # absent the effective value falls back to
+  # `SiteSetting.popup_notifications_default_enabled`.
+  USER_ENABLED_FIELD = "jtech_popup_notifications_enabled"
+end
+
+after_initialize do
+  register_user_custom_field_type(DiscoursePopupNotifications::USER_ENABLED_FIELD, :boolean)
+
+  # Permit the field through UsersController#update so the account-page
+  # dropdown can save it with the rest of the preferences form.
+  register_editable_user_custom_field(DiscoursePopupNotifications::USER_ENABLED_FIELD)
+
+  # Effective, default-aware preference for the client. Returns the stored
+  # boolean when the user has chosen, otherwise the site-wide default.
+  add_to_serializer(:current_user, :jtech_popup_notifications_enabled) do
+    raw = object.custom_fields[DiscoursePopupNotifications::USER_ENABLED_FIELD]
+    if raw.nil?
+      SiteSetting.popup_notifications_default_enabled
+    else
+      ActiveModel::Type::Boolean.new.cast(raw)
+    end
+  end
+end