diff --git a/changelog.d/grouped-notifications-api.add b/changelog.d/grouped-notifications-api.add
index 82ce8b178..8c2cc5397 100644
--- a/changelog.d/grouped-notifications-api.add
+++ b/changelog.d/grouped-notifications-api.add
@@ -1 +1 @@
-Add Mastodon-compatible grouped notifications API endpoints under `/api/v2/notifications`
+Add Mastodon-compatible grouped notifications API endpoints under `/api/v2/notifications` for newly-created notifications
diff --git a/lib/pleroma/notification.ex b/lib/pleroma/notification.ex
index ec10854e3..afd750823 100644
--- a/lib/pleroma/notification.ex
+++ b/lib/pleroma/notification.ex
@@ -35,6 +35,7 @@ defmodule Pleroma.Notification do
     # remember to add a migration to add it to the `notifications_type` enum
     # as well.
     field(:type, :string)
+    field(:group_key, :string)
     belongs_to(:user, User, type: FlakeId.Ecto.CompatType)
     belongs_to(:activity, Activity, type: FlakeId.Ecto.CompatType)
 
@@ -49,7 +50,7 @@ defmodule Pleroma.Notification do
         |> type_from_activity()
 
       notification
-      |> changeset(%{type: type})
+      |> changeset(%{type: type, group_key: grouped_notification_key(type, activity)})
       |> Repo.update()
     end
   end
@@ -97,14 +98,11 @@ defmodule Pleroma.Notification do
     group_key(notification, @groupable_notification_types)
   end
 
-  def group_key(%Notification{type: type} = notification, grouped_types) do
+  def group_key(%Notification{type: type, group_key: group_key} = notification, grouped_types) do
     grouped_types = normalize_grouped_types(grouped_types)
 
-    if type in @groupable_notification_types and type in grouped_types do
-      case group_target_id(notification) do
-        nil -> ungrouped_group_key(notification)
-        target_id -> "#{type}-#{target_id}-#{group_time_bucket(notification)}"
-      end
+    if type in @groupable_notification_types and type in grouped_types and is_binary(group_key) do
+      group_key
     else
       ungrouped_group_key(notification)
     end
@@ -116,15 +114,27 @@ defmodule Pleroma.Notification do
 
   defp ungrouped_group_key(%Notification{id: id}), do: "ungrouped-#{id}"
 
-  defp group_time_bucket(%Notification{inserted_at: inserted_at}) do
+  defp grouped_notification_key(type, activity) when type in @groupable_notification_types do
+    with target_id when is_binary(target_id) <- group_target_id(type, activity) do
+      # Mastodon uses Redis to reuse a recent bucket for rolling 12h windows. Pleroma keeps keys
+      # deterministic and self-contained; clients must treat group_key as opaque either way.
+      "#{type}-#{target_id}-#{group_time_bucket(activity)}"
+    end
+  end
+
+  defp grouped_notification_key(_type, _activity), do: nil
+
+  defp group_time_bucket(%Activity{inserted_at: inserted_at}) when not is_nil(inserted_at) do
     inserted_at
     |> NaiveDateTime.to_erl()
     |> :calendar.datetime_to_gregorian_seconds()
     |> div(@group_bucket_seconds)
   end
 
-  defp group_target_id(%Notification{type: type, activity: activity})
-       when type in ["favourite", "reblog"] do
+  defp group_time_bucket(_),
+    do: group_time_bucket(%Activity{inserted_at: NaiveDateTime.utc_now()})
+
+  defp group_target_id(type, activity) when type in ["favourite", "reblog"] do
     with object_id when is_binary(object_id) <- object_id_for(activity),
          %Activity{id: id} <- Activity.get_create_by_object_ap_id(object_id) do
       to_string(id)
@@ -133,14 +143,14 @@ defmodule Pleroma.Notification do
     end
   end
 
-  defp group_target_id(%Notification{type: "follow", activity: %{data: %{"object" => ap_id}}}) do
+  defp group_target_id("follow", %{data: %{"object" => ap_id}}) do
     case User.get_cached_by_ap_id(ap_id) do
       %User{id: id} -> to_string(id)
       _ -> nil
     end
   end
 
-  defp group_target_id(_), do: nil
+  defp group_target_id(_, _), do: nil
 
   defp object_id_for(%{data: %{"object" => %{"id" => id}}}) when is_binary(id), do: id
   defp object_id_for(%{data: %{"object" => id}}) when is_binary(id), do: id
@@ -163,7 +173,7 @@ defmodule Pleroma.Notification do
 
   def changeset(%Notification{} = notification, attrs) do
     notification
-    |> cast(attrs, [:seen, :type])
+    |> cast(attrs, [:seen, :type, :group_key])
     |> validate_inclusion(:type, @notification_types)
   end
 
@@ -542,7 +552,8 @@ defmodule Pleroma.Notification do
           user_id: user.id,
           activity: activity,
           seen: mark_as_read?(activity, user),
-          type: type
+          type: type,
+          group_key: grouped_notification_key(type, activity)
         })
         |> Marker.multi_set_last_read_id(user, "notifications")
         |> Repo.transaction()
diff --git a/lib/pleroma/web/api_spec/operations/notification_operation.ex b/lib/pleroma/web/api_spec/operations/notification_operation.ex
index ba996c13b..6c8f7d5e9 100644
--- a/lib/pleroma/web/api_spec/operations/notification_operation.ex
+++ b/lib/pleroma/web/api_spec/operations/notification_operation.ex
@@ -3,7 +3,6 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.ApiSpec.NotificationOperation do
-  alias OpenApiSpex.Operation
   alias OpenApiSpex.Operation
   alias OpenApiSpex.Schema
   alias Pleroma.Web.ApiSpec.Schemas.Account
@@ -125,7 +124,7 @@ defmodule Pleroma.Web.ApiSpec.NotificationOperation do
       tags: ["Notifications"],
       summary: "Retrieve notification group accounts",
       operationId: "NotificationController.group_accounts",
-      security: [%{"oAuth" => ["write:notifications"]}],
+      security: [%{"oAuth" => ["read:notifications"]}],
       parameters: [group_key_param()],
       responses: %{
         200 =>
@@ -269,7 +268,7 @@ defmodule Pleroma.Web.ApiSpec.NotificationOperation do
       },
       example: %{
         "id" => "34975861",
-        "group-key" => "ungrouped-34975861",
+        "group_key" => "ungrouped-34975861",
         "type" => "mention",
         "created_at" => "2019-11-23T07:49:02.064Z",
         "account" => Account.schema().example,
diff --git a/lib/pleroma/web/controller_helper.ex b/lib/pleroma/web/controller_helper.ex
index b15b0ea81..eecd1774f 100644
--- a/lib/pleroma/web/controller_helper.ex
+++ b/lib/pleroma/web/controller_helper.ex
@@ -55,16 +55,24 @@ defmodule Pleroma.Web.ControllerHelper do
 
   # TODO: Only fetch the params from open_api_spex when everything is converted
   @id_keys Pagination.page_keys() -- ["limit", "order"]
+  @id_key_atoms Enum.map(@id_keys, &String.to_atom/1)
   defp build_pagination_fields(conn, min_id, max_id, extra_params, order) do
+    path_param_keys =
+      conn.path_params
+      |> Map.keys()
+      |> Enum.flat_map(&[&1, String.to_existing_atom(&1)])
+
     params =
       if Map.has_key?(conn.private, :open_api_spex) do
         get_in(conn, [Access.key(:private), Access.key(:open_api_spex), Access.key(:params)])
       else
         conn.params
       end
-      |> Map.drop(Map.keys(conn.path_params) |> Enum.map(&String.to_existing_atom/1))
+      |> Map.drop(path_param_keys)
       |> Map.merge(extra_params)
-      |> Map.drop(@id_keys)
+      # OpenApiSpex casts params to atoms while uncast conn params are string-keyed. Drop both so
+      # generated links replace pagination cursors instead of preserving stale request cursors.
+      |> Map.drop(@id_keys ++ @id_key_atoms)
 
     {{next_id, nid}, {prev_id, pid}} =
       if order == :desc,
diff --git a/lib/pleroma/web/mastodon_api/controllers/notification_controller.ex b/lib/pleroma/web/mastodon_api/controllers/notification_controller.ex
index 5cd8576c1..2cc31db0c 100644
--- a/lib/pleroma/web/mastodon_api/controllers/notification_controller.ex
+++ b/lib/pleroma/web/mastodon_api/controllers/notification_controller.ex
@@ -13,7 +13,9 @@ defmodule Pleroma.Web.MastodonAPI.NotificationController do
   alias Pleroma.Web.MastodonAPI.MastodonAPI
   alias Pleroma.Web.Plugs.OAuthScopesPlug
 
-  @oauth_read_actions [:show, :index, :grouped_index, :show_group, :unread_count]
+  # Mastodon's docs currently list write:notifications for group accounts, but the endpoint is
+  # read-only and Mastodon's implementation accepts read:notifications. Prefer least privilege.
+  @oauth_read_actions [:show, :index, :grouped_index, :show_group, :group_accounts, :unread_count]
 
   plug(Pleroma.Web.ApiSpec.CastAndValidate, replace_params: false)
 
@@ -92,7 +94,8 @@ defmodule Pleroma.Web.MastodonAPI.NotificationController do
           conn,
         _
       ) do
-    notifications = MastodonAPI.get_notification_group(user, group_key, %{})
+    {notifications, notification_group_counts, notification_group_bounds} =
+      MastodonAPI.get_notification_group_result(user, group_key, %{})
 
     if Enum.empty?(notifications) do
       conn
@@ -103,8 +106,11 @@ defmodule Pleroma.Web.MastodonAPI.NotificationController do
 
       render(conn, "grouped_index.json",
         notification_groups: [notifications],
+        notification_group_counts: notification_group_counts,
+        notification_group_bounds: notification_group_bounds,
         for: user,
-        grouped_types: grouped_types
+        grouped_types: grouped_types,
+        include_page_metadata: false
       )
     end
   end
@@ -115,10 +121,9 @@ defmodule Pleroma.Web.MastodonAPI.NotificationController do
           conn,
         _
       ) do
-    users =
-      user
-      |> MastodonAPI.get_notification_group(group_key, %{})
-      |> notification_actors()
+    # Mastodon paginates this endpoint in code, but the public docs say it returns accounts of all
+    # notifications in the group and do not document cursor params here. Follow the documented API.
+    users = MastodonAPI.get_notification_group_accounts(user, group_key)
 
     json(conn, AccountView.render("index.json", %{users: users, for: user}))
   end
@@ -154,12 +159,7 @@ defmodule Pleroma.Web.MastodonAPI.NotificationController do
           conn,
         _
       ) do
-    ids =
-      user
-      |> MastodonAPI.get_notification_group(group_key, %{})
-      |> Enum.map(& &1.id)
-
-    Notification.destroy_multiple(user, ids)
+    MastodonAPI.dismiss_notification_group(user, group_key)
     json(conn, %{})
   end
 
@@ -179,7 +179,8 @@ defmodule Pleroma.Web.MastodonAPI.NotificationController do
   defp do_get_grouped_notifications(%{assigns: %{user: user}} = conn, params) do
     params = normalize_notification_params(params)
 
-    {notification_groups, page_notifications, notification_group_counts} =
+    {notification_groups, page_notifications, notification_group_counts,
+     notification_group_bounds} =
       MastodonAPI.get_grouped_notification_page(user, params)
 
     conn
@@ -187,6 +188,7 @@ defmodule Pleroma.Web.MastodonAPI.NotificationController do
     |> render("grouped_index.json",
       notification_groups: notification_groups,
       notification_group_counts: notification_group_counts,
+      notification_group_bounds: notification_group_bounds,
       for: user,
       grouped_types: params["grouped_types"]
     )
@@ -203,13 +205,6 @@ defmodule Pleroma.Web.MastodonAPI.NotificationController do
     |> Map.put_new("types", Map.get(params, :include_types, @default_notification_types))
   end
 
-  defp notification_actors(notifications) do
-    notifications
-    |> Enum.map(&User.get_cached_by_ap_id(&1.activity.data["actor"]))
-    |> Enum.filter(& &1)
-    |> Enum.uniq_by(& &1.id)
-  end
-
   # GET /api/v1/notifications/:id
   def show(%{assigns: %{user: user}, private: %{open_api_spex: %{params: %{id: id}}}} = conn, _) do
     with {:ok, notification} <- Notification.get(user, id) do
diff --git a/lib/pleroma/web/mastodon_api/mastodon_api.ex b/lib/pleroma/web/mastodon_api/mastodon_api.ex
index 57cbfd6bf..cb11a3f4a 100644
--- a/lib/pleroma/web/mastodon_api/mastodon_api.ex
+++ b/lib/pleroma/web/mastodon_api/mastodon_api.ex
@@ -6,6 +6,7 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPI do
   import Ecto.Query
   import Ecto.Changeset
 
+  alias Pleroma.Marker
   alias Pleroma.Notification
   alias Pleroma.Pagination
   alias Pleroma.Repo
@@ -13,6 +14,8 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPI do
   alias Pleroma.User
   alias Pleroma.Web.CommonAPI
 
+  @notification_group_sample_limit 8
+
   @spec follow(User.t(), User.t(), map) :: {:ok, User.t()} | {:error, String.t()}
   def follow(follower, followed, params \\ %{}) do
     result =
@@ -68,38 +71,55 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPI do
   end
 
   def get_grouped_notification_page(user, params \\ %{}) do
-    grouped_types = Map.get(params, "grouped_types", Map.get(params, :grouped_types))
-    {query, order} = group_pagination_query(notifications_query(user, params), params)
+    grouped_types =
+      params
+      |> Map.get("grouped_types", Map.get(params, :grouped_types))
+      |> Notification.normalize_grouped_types()
 
-    notifications =
+    query = notifications_query(user, params)
+    {order, cursor_filters} = group_pagination(params)
+
+    group_rows =
       query
-      |> order_by([n], [{^order, n.id}])
-      |> Repo.all()
+      |> notification_group_rows(grouped_types, grouped_limit(params), order, cursor_filters)
 
-    notification_group_counts =
-      Enum.frequencies_by(notifications, &Notification.group_key(&1, grouped_types))
+    group_rows = if order == :asc, do: Enum.reverse(group_rows), else: group_rows
 
-    page_notifications =
-      notifications
-      |> take_grouped_page_notifications(grouped_types, grouped_limit(params))
+    page_notifications = representative_notifications(query, group_rows)
 
-    page_notifications =
-      if order == :asc, do: Enum.reverse(page_notifications), else: page_notifications
+    notification_groups =
+      Enum.map(group_rows, &notification_group_sample(user, params, &1.group_key))
 
     {
-      Notification.group_notifications(page_notifications, grouped_types),
+      notification_groups,
       page_notifications,
-      notification_group_counts
+      notification_group_counts(group_rows),
+      notification_group_bounds(group_rows)
     }
   end
 
   def get_grouped_notification_groups(user, params \\ %{}) do
-    {groups, _notifications, _notification_group_counts} =
+    {groups, _notifications, _notification_group_counts, _notification_group_bounds} =
       get_grouped_notification_page(user, params)
 
     groups
   end
 
+  def get_notification_group_result(user, group_key, params \\ %{}) do
+    notifications = notification_group_sample(user, params, group_key)
+    metadata = notification_group_metadata(user, group_key, params)
+
+    if Enum.empty?(notifications) or is_nil(metadata) do
+      {[], %{}, %{}}
+    else
+      {
+        notifications,
+        %{group_key => metadata.notifications_count},
+        %{group_key => Map.drop(metadata, [:notifications_count])}
+      }
+    end
+  end
+
   def get_notification_group(user, group_key, params \\ %{})
 
   def get_notification_group(user, "ungrouped-" <> notification_id, _params) do
@@ -110,36 +130,58 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPI do
   end
 
   def get_notification_group(user, group_key, params) do
-    grouped_types = Map.get(params, "grouped_types", Map.get(params, :grouped_types))
-
-    user
-    |> notifications_query(params)
-    |> order_by([n], desc: n.id)
-    |> Repo.all()
-    |> Enum.filter(&(Notification.group_key(&1, grouped_types) == group_key))
+    notification_group_sample(user, params, group_key)
   end
 
-  defp group_pagination_query(query, params) do
+  def get_notification_group_accounts(user, "ungrouped-" <> notification_id) do
+    with {:ok, notification} <- Notification.get(user, notification_id),
+         %User{} = actor <- User.get_cached_by_ap_id(notification.activity.data["actor"]) do
+      [actor]
+    else
+      _ -> []
+    end
+  end
+
+  def get_notification_group_accounts(user, group_key) do
+    user
+    |> notification_group_query(group_key, %{})
+    |> exclude(:preload)
+    |> distinct(true)
+    |> select([user_actor: user_actor], user_actor)
+    |> Repo.all()
+  end
+
+  def dismiss_notification_group(user, "ungrouped-" <> notification_id) do
+    Notification.destroy_multiple(user, [notification_id])
+  end
+
+  def dismiss_notification_group(%User{id: user_id}, group_key) do
+    Notification
+    |> where([n], n.user_id == ^user_id and n.group_key == ^group_key)
+    |> Repo.delete_all()
+  end
+
+  defp group_pagination(params) do
     cond do
       min_id = Map.get(params, "min_id", Map.get(params, :min_id)) ->
-        query = where(query, [n], n.id > ^min_id)
+        cursor_filters = [{:gt, min_id}]
 
-        query =
+        cursor_filters =
           case Map.get(params, "max_id", Map.get(params, :max_id)) do
-            nil -> query
-            max_id -> where(query, [n], n.id < ^max_id)
+            nil -> cursor_filters
+            max_id -> [{:lt, max_id} | cursor_filters]
           end
 
-        {query, :asc}
+        {:asc, cursor_filters}
 
       since_id = Map.get(params, "since_id", Map.get(params, :since_id)) ->
-        {where(query, [n], n.id > ^since_id), :desc}
+        {:desc, [{:gt, since_id}]}
 
       max_id = Map.get(params, "max_id", Map.get(params, :max_id)) ->
-        {where(query, [n], n.id < ^max_id), :desc}
+        {:desc, [{:lt, max_id}]}
 
       true ->
-        {query, :desc}
+        {:desc, []}
     end
   end
 
@@ -150,41 +192,190 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPI do
     |> min(80)
   end
 
-  defp take_grouped_page_notifications(notifications, grouped_types, group_limit) do
-    {notifications, _group_keys} =
-      Enum.reduce_while(notifications, {[], MapSet.new()}, fn notification,
-                                                              {notifications, group_keys} ->
-        group_key = Notification.group_key(notification, grouped_types)
-
-        cond do
-          MapSet.member?(group_keys, group_key) ->
-            {:cont, {[notification | notifications], group_keys}}
-
-          MapSet.size(group_keys) < group_limit ->
-            {:cont, {[notification | notifications], MapSet.put(group_keys, group_key)}}
-
-          true ->
-            {:halt, {notifications, group_keys}}
-        end
-      end)
-
-    Enum.reverse(notifications)
-  end
-
   def unread_notification_group_count(user, params \\ %{}) do
-    grouped_types = Map.get(params, "grouped_types", Map.get(params, :grouped_types))
+    grouped_types =
+      params
+      |> Map.get("grouped_types", Map.get(params, :grouped_types))
+      |> Notification.normalize_grouped_types()
+
     limit = unread_count_limit(params)
 
     user
     |> notifications_query(params)
-    |> where([n], n.seen == false)
-    |> order_by([n], desc: n.id)
-    |> limit(^limit)
-    |> Repo.all()
-    |> Notification.group_notifications(grouped_types)
+    # The grouped API docs define unread by the notifications marker, not by Pleroma's per-row
+    # seen flag used by the v1 unread count. Keep this marker-based for Mastodon clients.
+    |> restrict_after_marker(notification_marker_last_read_id(user))
+    |> notification_group_rows(grouped_types, limit, :desc, [])
     |> length()
   end
 
+  defp notification_group_rows(query, grouped_types, group_limit, :desc, cursor_filters) do
+    query
+    |> notification_group_keyed_query(grouped_types)
+    |> group_by([n], n.group_key)
+    |> apply_group_cursor_filters(cursor_filters)
+    |> select([n], %{
+      group_key: n.group_key,
+      representative_id: max(n.id),
+      notifications_count: count(n.id),
+      page_min_id: min(n.id),
+      page_max_id: max(n.id),
+      latest_page_notification_at: max(n.inserted_at)
+    })
+    |> order_by([n], desc: max(n.id))
+    |> limit(^group_limit)
+    |> Repo.all()
+  end
+
+  defp notification_group_rows(query, grouped_types, group_limit, :asc, cursor_filters) do
+    query
+    |> notification_group_keyed_query(grouped_types)
+    |> group_by([n], n.group_key)
+    |> apply_group_cursor_filters(cursor_filters)
+    |> select([n], %{
+      group_key: n.group_key,
+      representative_id: max(n.id),
+      notifications_count: count(n.id),
+      page_min_id: min(n.id),
+      page_max_id: max(n.id),
+      latest_page_notification_at: max(n.inserted_at)
+    })
+    |> order_by([n], asc: max(n.id))
+    |> limit(^group_limit)
+    |> Repo.all()
+  end
+
+  defp apply_group_cursor_filters(query, []), do: query
+
+  defp apply_group_cursor_filters(query, [{:gt, id} | rest]) do
+    query
+    |> having([n], max(n.id) > ^id)
+    |> apply_group_cursor_filters(rest)
+  end
+
+  defp apply_group_cursor_filters(query, [{:lt, id} | rest]) do
+    query
+    |> having([n], max(n.id) < ^id)
+    |> apply_group_cursor_filters(rest)
+  end
+
+  defp notification_group_keyed_query(query, grouped_types) do
+    query
+    |> exclude(:preload)
+    |> select([n], %{
+      id: n.id,
+      inserted_at: n.inserted_at,
+      group_key:
+        fragment(
+          "CASE WHEN ? IS NOT NULL AND ?::text = ANY(?) THEN ? ELSE 'ungrouped-' || ?::text END",
+          n.group_key,
+          n.type,
+          type(^grouped_types, {:array, :string}),
+          n.group_key,
+          n.id
+        )
+    })
+    |> subquery()
+  end
+
+  defp representative_notifications(_query, []), do: []
+
+  defp representative_notifications(query, group_rows) do
+    representative_ids = Enum.map(group_rows, & &1.representative_id)
+
+    notifications_by_id =
+      query
+      |> where([n], n.id in ^representative_ids)
+      |> Repo.all()
+      |> Map.new(&{to_string(&1.id), &1})
+
+    group_rows
+    |> Enum.map(&Map.get(notifications_by_id, to_string(&1.representative_id)))
+    |> Enum.filter(& &1)
+  end
+
+  defp notification_group_counts(group_rows) do
+    Map.new(group_rows, &{&1.group_key, &1.notifications_count})
+  end
+
+  defp notification_group_bounds(group_rows) do
+    Map.new(group_rows, fn row ->
+      {row.group_key,
+       %{
+         page_min_id: row.page_min_id,
+         page_max_id: row.page_max_id,
+         latest_page_notification_at: row.latest_page_notification_at
+       }}
+    end)
+  end
+
+  defp notification_group_sample(user, _params, "ungrouped-" <> notification_id) do
+    case Notification.get(user, notification_id) do
+      {:ok, notification} -> [notification]
+      _ -> []
+    end
+  end
+
+  defp notification_group_sample(user, params, group_key) do
+    user
+    |> notification_group_query(group_key, params)
+    |> order_by([n], desc: n.id)
+    |> limit(^@notification_group_sample_limit)
+    |> Repo.all()
+  end
+
+  defp notification_group_metadata(user, "ungrouped-" <> notification_id, _params) do
+    case Notification.get(user, notification_id) do
+      {:ok, notification} ->
+        %{
+          notifications_count: 1,
+          page_min_id: notification.id,
+          page_max_id: notification.id,
+          latest_page_notification_at: notification.inserted_at
+        }
+
+      _ ->
+        nil
+    end
+  end
+
+  defp notification_group_metadata(user, group_key, params) do
+    user
+    |> notification_group_query(group_key, params)
+    |> exclude(:preload)
+    |> select([n], %{
+      notifications_count: count(n.id),
+      page_min_id: min(n.id),
+      page_max_id: max(n.id),
+      latest_page_notification_at: max(n.inserted_at)
+    })
+    |> Repo.one()
+    |> case do
+      %{notifications_count: 0} -> nil
+      metadata -> metadata
+    end
+  end
+
+  defp notification_group_query(user, group_key, params) do
+    user
+    |> notifications_query(params)
+    |> where([n], n.group_key == ^group_key)
+  end
+
+  defp notification_marker_last_read_id(user) do
+    Marker
+    |> where([m], m.user_id == ^user.id and m.timeline == "notifications")
+    |> select([m], m.last_read_id)
+    |> Repo.one()
+  end
+
+  defp restrict_after_marker(query, last_read_id)
+       when is_binary(last_read_id) and last_read_id != "" do
+    where(query, [n], n.id > ^last_read_id)
+  end
+
+  defp restrict_after_marker(query, _last_read_id), do: query
+
   defp notifications_query(user, params) do
     options = notification_options(user, params)
 
diff --git a/lib/pleroma/web/mastodon_api/views/notification_view.ex b/lib/pleroma/web/mastodon_api/views/notification_view.ex
index 466073853..33d4b2924 100644
--- a/lib/pleroma/web/mastodon_api/views/notification_view.ex
+++ b/lib/pleroma/web/mastodon_api/views/notification_view.ex
@@ -90,6 +90,8 @@ defmodule Pleroma.Web.MastodonAPI.NotificationView do
       ) do
     grouped_types = Notification.normalize_grouped_types(opts[:grouped_types])
     notification_group_counts = Map.get(opts, :notification_group_counts, %{})
+    notification_group_bounds = Map.get(opts, :notification_group_bounds, %{})
+    include_page_metadata = Map.get(opts, :include_page_metadata, true)
 
     statuses =
       notification_groups
@@ -110,7 +112,14 @@ defmodule Pleroma.Web.MastodonAPI.NotificationView do
       notification_groups:
         Enum.map(
           notification_groups,
-          &render_group(&1, reading_user, grouped_types, notification_group_counts)
+          &render_group(
+            &1,
+            reading_user,
+            grouped_types,
+            notification_group_counts,
+            notification_group_bounds,
+            include_page_metadata
+          )
         )
     }
   end
@@ -184,27 +193,50 @@ defmodule Pleroma.Web.MastodonAPI.NotificationView do
          [%Notification{} = notification | _] = notifications,
          _reading_user,
          grouped_types,
-         notification_group_counts
+         notification_group_counts,
+         notification_group_bounds,
+         include_page_metadata
        ) do
     latest_notification = List.first(notifications)
     oldest_notification = List.last(notifications)
     status_activity = status_activity_for_group(notifications, grouped_types)
     group_key = Notification.group_key(notification, grouped_types)
+    bounds = Map.get(notification_group_bounds, group_key, %{})
 
     response = %{
       group_key: group_key,
       notifications_count: Map.get(notification_group_counts, group_key, length(notifications)),
       type: notification.type,
-      most_recent_notification_id: to_string(latest_notification.id),
-      page_min_id: to_string(oldest_notification.id),
-      page_max_id: to_string(latest_notification.id),
-      latest_page_notification_at: CommonAPI.Utils.to_masto_date(latest_notification.inserted_at),
+      most_recent_notification_id:
+        bounds
+        |> Map.get(:page_max_id, latest_notification.id)
+        |> to_string(),
       sample_account_ids:
         notifications
         |> notification_actors()
         |> Enum.map(&to_string(&1.id))
     }
 
+    response =
+      if include_page_metadata do
+        Map.merge(response, %{
+          page_min_id:
+            bounds
+            |> Map.get(:page_min_id, oldest_notification.id)
+            |> to_string(),
+          page_max_id:
+            bounds
+            |> Map.get(:page_max_id, latest_notification.id)
+            |> to_string(),
+          latest_page_notification_at:
+            bounds
+            |> Map.get(:latest_page_notification_at, latest_notification.inserted_at)
+            |> CommonAPI.Utils.to_masto_date()
+        })
+      else
+        response
+      end
+
     if status_activity do
       Map.put(response, :status_id, to_string(status_activity.id))
     else
diff --git a/priv/repo/migrations/20260523070000_add_group_key_to_notifications.exs b/priv/repo/migrations/20260523070000_add_group_key_to_notifications.exs
new file mode 100644
index 000000000..7c7d529e0
--- /dev/null
+++ b/priv/repo/migrations/20260523070000_add_group_key_to_notifications.exs
@@ -0,0 +1,15 @@
+defmodule Pleroma.Repo.Migrations.AddGroupKeyToNotifications do
+  use Ecto.Migration
+
+  def change do
+    alter table(:notifications) do
+      add(:group_key, :string)
+    end
+
+    create_if_not_exists(
+      index(:notifications, [:user_id, :group_key, "id desc nulls last"],
+        where: "group_key IS NOT NULL"
+      )
+    )
+  end
+end
diff --git a/test/pleroma/web/mastodon_api/controllers/notification_controller_test.exs b/test/pleroma/web/mastodon_api/controllers/notification_controller_test.exs
index 1d3a9e966..e9c521d6b 100644
--- a/test/pleroma/web/mastodon_api/controllers/notification_controller_test.exs
+++ b/test/pleroma/web/mastodon_api/controllers/notification_controller_test.exs
@@ -587,10 +587,10 @@ defmodule Pleroma.Web.MastodonAPI.NotificationControllerTest do
       {:ok, _} = CommonAPI.favorite(status.id, other_user1)
       {:ok, _} = CommonAPI.favorite(status.id, other_user2)
 
-      notification_ids =
-        Notification
-        |> Repo.all()
-        |> Enum.map(&to_string(&1.id))
+      notifications = Repo.all(Notification)
+      notification_ids = Enum.map(notifications, &to_string(&1.id))
+      assert [persisted_group_key] = notifications |> Enum.map(& &1.group_key) |> Enum.uniq()
+      assert is_binary(persisted_group_key)
 
       result =
         conn
@@ -613,6 +613,7 @@ defmodule Pleroma.Web.MastodonAPI.NotificationControllerTest do
       assert group["latest_page_notification_at"]
       assert Enum.sort(group["sample_account_ids"]) == Enum.sort([other_user1.id, other_user2.id])
       group_key = group["group_key"]
+      assert group_key == persisted_group_key
 
       assert [%{"group_key" => ^group_key}, %{"group_key" => ^group_key}] =
                conn
@@ -626,6 +627,9 @@ defmodule Pleroma.Web.MastodonAPI.NotificationControllerTest do
 
       assert shown_group["group_key"] == group_key
       assert shown_group["notifications_count"] == 2
+      refute Map.has_key?(shown_group, "page_min_id")
+      refute Map.has_key?(shown_group, "page_max_id")
+      refute Map.has_key?(shown_group, "latest_page_notification_at")
     end
 
     test "round-trips ungrouped group keys when grouped_types excludes a type" do
@@ -648,6 +652,48 @@ defmodule Pleroma.Web.MastodonAPI.NotificationControllerTest do
                |> json_response_and_validate_schema(200)
     end
 
+    test "keeps legacy notifications without persisted group keys ungrouped" do
+      %{user: user, conn: conn} = oauth_access(["read:notifications"])
+      other_user1 = insert(:user)
+      other_user2 = insert(:user)
+
+      {:ok, status} = CommonAPI.post(user, %{status: "hello"})
+      {:ok, favorite1} = CommonAPI.favorite(status.id, other_user1)
+      {:ok, favorite2} = CommonAPI.favorite(status.id, other_user2)
+
+      notification_ids =
+        [favorite1, favorite2]
+        |> Enum.map(&get_notification_id_by_activity/1)
+
+      Repo.update_all(Notification, set: [group_key: nil])
+
+      expected_group_keys = Enum.map(notification_ids, &"ungrouped-#{&1}")
+
+      assert [%{"group_key" => group_key1}, %{"group_key" => group_key2}] =
+               conn
+               |> get("/api/v1/notifications")
+               |> json_response_and_validate_schema(200)
+
+      assert Enum.sort([group_key1, group_key2]) == Enum.sort(expected_group_keys)
+
+      %{"notification_groups" => groups} =
+        conn
+        |> get("/api/v2/notifications")
+        |> json_response_and_validate_schema(200)
+
+      assert Enum.sort(Enum.map(groups, & &1["group_key"])) == Enum.sort(expected_group_keys)
+      assert Enum.all?(groups, &(&1["notifications_count"] == 1))
+
+      group_key = List.first(expected_group_keys)
+
+      assert %{
+               "notification_groups" => [%{"group_key" => ^group_key, "notifications_count" => 1}]
+             } =
+               conn
+               |> get("/api/v2/notifications/#{group_key}")
+               |> json_response_and_validate_schema(200)
+    end
+
     test "paginates notification groups instead of raw notifications" do
       %{user: user, conn: conn} = oauth_access(["read:notifications"])
       other_user1 = insert(:user)
@@ -674,6 +720,44 @@ defmodule Pleroma.Web.MastodonAPI.NotificationControllerTest do
              ] = groups
     end
 
+    test "uses group-level cursors when paginating notification groups" do
+      %{user: user, conn: conn} = oauth_access(["read:notifications"])
+      other_user1 = insert(:user)
+      other_user2 = insert(:user)
+      other_user3 = insert(:user)
+
+      {:ok, older_status} = CommonAPI.post(user, %{status: "older"})
+      {:ok, _} = CommonAPI.favorite(older_status.id, other_user3)
+
+      {:ok, newer_status} = CommonAPI.post(user, %{status: "newer"})
+      {:ok, _} = CommonAPI.favorite(newer_status.id, other_user1)
+      {:ok, _} = CommonAPI.favorite(newer_status.id, other_user2)
+      older_status_id = older_status.id
+      newer_status_id = newer_status.id
+
+      assert %{
+               "notification_groups" => [
+                 %{
+                   "status_id" => ^newer_status_id,
+                   "notifications_count" => 2,
+                   "most_recent_notification_id" => cursor
+                 }
+               ]
+             } =
+               conn
+               |> get("/api/v2/notifications?limit=1")
+               |> json_response_and_validate_schema(200)
+
+      assert %{
+               "notification_groups" => [
+                 %{"status_id" => ^older_status_id, "notifications_count" => 1}
+               ]
+             } =
+               conn
+               |> get("/api/v2/notifications?limit=1&max_id=#{cursor}")
+               |> json_response_and_validate_schema(200)
+    end
+
     test "returns total notification count for a partially represented group" do
       %{user: user, conn: conn} = oauth_access(["read:notifications"])
       other_user1 = insert(:user)
@@ -715,27 +799,78 @@ defmodule Pleroma.Web.MastodonAPI.NotificationControllerTest do
                |> json_response_and_validate_schema(200)
     end
 
+    test "counts unread notification groups newer than the notification marker" do
+      %{user: user, conn: conn} = oauth_access(["read:notifications"])
+      other_user = insert(:user)
+      mentioner = insert(:user)
+
+      {:ok, status} = CommonAPI.post(user, %{status: "older"})
+      {:ok, favorite_activity} = CommonAPI.favorite(status.id, other_user)
+      marker_id = get_notification_id_by_activity(favorite_activity)
+
+      {:ok, _} = CommonAPI.post(mentioner, %{status: "newer @#{user.nickname}"})
+
+      {:ok, _} =
+        Pleroma.Marker.upsert(user, %{"notifications" => %{"last_read_id" => marker_id}})
+
+      assert %{"count" => 1} =
+               conn
+               |> get("/api/v2/notifications/unread_count")
+               |> json_response_and_validate_schema(200)
+    end
+
+    test "does not preserve stale cursor params in grouped notification link headers" do
+      %{user: user, conn: conn} = oauth_access(["read:notifications"])
+      other_user = insert(:user)
+
+      {:ok, activity1} = CommonAPI.post(other_user, %{status: "one @#{user.nickname}"})
+      {:ok, _activity2} = CommonAPI.post(other_user, %{status: "two @#{user.nickname}"})
+      {:ok, activity3} = CommonAPI.post(other_user, %{status: "three @#{user.nickname}"})
+
+      notification1_id = get_notification_id_by_activity(activity1)
+      notification3_id = get_notification_id_by_activity(activity3)
+
+      conn = get(conn, "/api/v2/notifications?since_id=#{notification1_id}&limit=1")
+
+      assert [link_header] = get_resp_header(conn, "link")
+      assert link_header =~ ~r/max_id=#{notification3_id}/
+      refute link_header =~ "since_id="
+    end
+
     test "lists accounts from and dismisses a notification group" do
       %{user: user, conn: conn} = oauth_access(["read:notifications", "write:notifications"])
-      other_user1 = insert(:user)
-      other_user2 = insert(:user)
+      other_users = insert_list(9, :user)
 
       {:ok, status} = CommonAPI.post(user, %{status: "hello"})
-      {:ok, _} = CommonAPI.favorite(status.id, other_user1)
-      {:ok, _} = CommonAPI.favorite(status.id, other_user2)
 
-      %{"notification_groups" => [%{"group_key" => group_key}]} =
+      Enum.each(other_users, fn other_user ->
+        {:ok, _} = CommonAPI.favorite(status.id, other_user)
+      end)
+
+      %{
+        "notification_groups" => [
+          %{
+            "group_key" => group_key,
+            "notifications_count" => 9,
+            "sample_account_ids" => sample_account_ids
+          }
+        ]
+      } =
         conn
         |> get("/api/v2/notifications")
         |> json_response_and_validate_schema(200)
 
+      assert length(sample_account_ids) == 8
+
+      %{conn: read_conn} = oauth_access(["read:notifications"], user: user)
+
       account_ids =
-        conn
+        read_conn
         |> get("/api/v2/notifications/#{group_key}/accounts")
         |> json_response_and_validate_schema(200)
         |> Enum.map(& &1["id"])
 
-      assert Enum.sort(account_ids) == Enum.sort([other_user1.id, other_user2.id])
+      assert Enum.sort(account_ids) == Enum.sort(Enum.map(other_users, & &1.id))
 
       assert %{} =
                conn
diff --git a/test/pleroma/web/mastodon_api/views/notification_view_test.exs b/test/pleroma/web/mastodon_api/views/notification_view_test.exs
index aa11ad682..2d0801589 100644
--- a/test/pleroma/web/mastodon_api/views/notification_view_test.exs
+++ b/test/pleroma/web/mastodon_api/views/notification_view_test.exs
@@ -98,6 +98,7 @@ defmodule Pleroma.Web.MastodonAPI.NotificationViewTest do
     {:ok, favorite_activity} = CommonAPI.favorite(create_activity.id, another_user)
     {:ok, [notification]} = Notification.create_notifications(favorite_activity)
     create_activity = Activity.get_by_id(create_activity.id)
+    assert is_binary(notification.group_key)
 
     expected = %{
       id: to_string(notification.id),
@@ -119,6 +120,7 @@ defmodule Pleroma.Web.MastodonAPI.NotificationViewTest do
     {:ok, reblog_activity} = CommonAPI.repeat(create_activity.id, another_user)
     {:ok, [notification]} = Notification.create_notifications(reblog_activity)
     reblog_activity = Activity.get_by_id(create_activity.id)
+    assert is_binary(notification.group_key)
 
     expected = %{
       id: to_string(notification.id),
@@ -138,6 +140,7 @@ defmodule Pleroma.Web.MastodonAPI.NotificationViewTest do
     followed = insert(:user)
     {:ok, followed, follower, _activity} = CommonAPI.follow(followed, follower)
     notification = Notification |> Repo.one() |> Repo.preload(:activity)
+    assert is_binary(notification.group_key)
 
     expected = %{
       id: to_string(notification.id),