diff --git a/assets/css/app.css b/assets/css/app.css
index 5d7ff107..f39dacbd 100644
--- a/assets/css/app.css
+++ b/assets/css/app.css
@@ -926,6 +926,21 @@
   pointer-events: none;
 }
 
+/*
+ * Sub-field sort menu (composite Member column). A native Popover-API element in
+ * the browser TOP LAYER so it escapes the members table's overflow; placement is
+ * pure CSS anchor positioning (the "⋮" trigger carries anchor-name, this popover
+ * carries position-anchor). `position-area` drops it just below the trigger,
+ * right-aligned, and `position-try-fallbacks` flips it above when there is no
+ * room below. The SubfieldMenu hook only toggles it — no coordinate math. This
+ * mirrors the payment-badge popover approach (§548) for a consistent look/feel.
+ */
+.popover-menu {
+  margin: 0;
+  position-area: bottom span-left;
+  position-try-fallbacks: flip-block;
+}
+
 /*
  * Vertically center the row checkbox in the sticky first column using the
  * table-native vertical-align: middle. This keeps display: table-cell intact so
diff --git a/assets/js/app.js b/assets/js/app.js
index 73e52fa5..85ea1875 100644
--- a/assets/js/app.js
+++ b/assets/js/app.js
@@ -407,6 +407,12 @@ Hooks.PopoverTooltip = {
     this.el.addEventListener("mouseleave", this.hide)
     this.el.addEventListener("blur", this.hide)
     this.el.addEventListener("keydown", this.onKey)
+    // Hide on activation: a click (sort/reset) triggers a LiveView re-render that
+    // re-emits the tooltip element without the JS-set inline top/left, which would
+    // otherwise leave the still-open popover stuck at the default (0,0) position,
+    // covering the header. Closing it here keeps it out of the re-render; the next
+    // hover repositions it cleanly.
+    this.el.addEventListener("click", this.hide)
   },
 
   destroyed() {
@@ -416,6 +422,121 @@ Hooks.PopoverTooltip = {
     this.el.removeEventListener("mouseleave", this.hide)
     this.el.removeEventListener("blur", this.hide)
     this.el.removeEventListener("keydown", this.onKey)
+    this.el.removeEventListener("click", this.hide)
+  }
+}
+
+// SubfieldMenu hook: toggles a native Popover menu (top layer, so it escapes the
+// overview table's overflow clipping) for choosing the composite Member column's
+// sort sub-field. Attached to the "⋮" trigger; data-menu-id names the <ul
+// popover> menu. Handles click / keyboard open, roving arrow-key focus,
+// Escape / click-away close, and closes after a selection (the LiveView
+// re-renders on sort_composite anyway). Positioned with getBoundingClientRect
+// (portable; no CSS anchor-positioning needed).
+Hooks.SubfieldMenu = {
+  mounted() {
+    this.menu = document.getElementById(this.el.dataset.menuId)
+    if (!this.menu || typeof this.menu.showPopover !== "function") return
+
+    // Hover/focus hint on the trigger, shown while the menu is closed. Same
+    // .popover-tooltip look as the sort-header tooltips; placement is CSS anchor
+    // positioning (no coordinate math).
+    this.tip = document.getElementById(this.el.dataset.tooltipId)
+    this.showTip = () => {
+      if (!this.tip || this.menu.matches(":popover-open")) return
+      try {
+        if (!this.tip.matches(":popover-open")) this.tip.showPopover()
+      } catch (_e) {}
+    }
+    this.hideTip = () => {
+      try {
+        if (this.tip && this.tip.matches(":popover-open")) this.tip.hidePopover()
+      } catch (_e) {}
+    }
+
+    this.items = () => [...this.menu.querySelectorAll('[role="menuitemradio"]')]
+
+    // Placement is pure CSS anchor positioning (see `.popover-menu` in app.css);
+    // this hook only toggles visibility, focus and keyboard interaction.
+    this.open = ({focusFirst = true} = {}) => {
+      this.hideTip()
+      if (!this.menu.matches(":popover-open")) this.menu.showPopover()
+      this.el.setAttribute("aria-expanded", "true")
+      if (focusFirst) {
+        const active = this.menu.querySelector('[aria-checked="true"]') || this.items()[0]
+        if (active) active.focus()
+      }
+    }
+
+    this.close = ({focusTrigger = false} = {}) => {
+      if (this.menu.matches(":popover-open")) this.menu.hidePopover()
+      this.el.setAttribute("aria-expanded", "false")
+      if (focusTrigger) this.el.focus()
+    }
+
+    this.onTriggerClick = (e) => {
+      e.preventDefault()
+      e.stopPropagation()
+      this.menu.matches(":popover-open") ? this.close() : this.open()
+    }
+    this.onTriggerKey = (e) => {
+      if (["ArrowDown", "Enter", " "].includes(e.key)) {
+        e.preventDefault()
+        this.open()
+      } else if (e.key === "ArrowUp") {
+        e.preventDefault()
+        this.open({focusFirst: false})
+        const items = this.items()
+        if (items.length) items[items.length - 1].focus()
+      }
+    }
+    this.onMenuKey = (e) => {
+      const items = this.items()
+      const i = items.indexOf(document.activeElement)
+      if (e.key === "ArrowDown") {
+        e.preventDefault()
+        ;(items[i + 1] || items[0]).focus()
+      } else if (e.key === "ArrowUp") {
+        e.preventDefault()
+        ;(items[i - 1] || items[items.length - 1]).focus()
+      } else if (e.key === "Escape") {
+        e.preventDefault()
+        this.close({focusTrigger: true})
+      } else if (e.key === "Tab") {
+        this.close()
+      }
+    }
+    // A selection fires the LiveView sort; drop the menu.
+    this.onMenuClick = () => this.close()
+    this.onDocPointer = (e) => {
+      if (!this.el.contains(e.target) && !this.menu.contains(e.target)) this.close()
+    }
+
+    this.el.addEventListener("click", this.onTriggerClick)
+    this.el.addEventListener("keydown", this.onTriggerKey)
+    this.el.addEventListener("mouseenter", this.showTip)
+    this.el.addEventListener("focus", this.showTip)
+    this.el.addEventListener("mouseleave", this.hideTip)
+    this.el.addEventListener("blur", this.hideTip)
+    this.menu.addEventListener("keydown", this.onMenuKey)
+    this.menu.addEventListener("click", this.onMenuClick)
+    document.addEventListener("pointerdown", this.onDocPointer, true)
+  },
+
+  destroyed() {
+    this.el.removeEventListener("click", this.onTriggerClick)
+    this.el.removeEventListener("keydown", this.onTriggerKey)
+    this.el.removeEventListener("mouseenter", this.showTip)
+    this.el.removeEventListener("focus", this.showTip)
+    this.el.removeEventListener("mouseleave", this.hideTip)
+    this.el.removeEventListener("blur", this.hideTip)
+    this.hideTip()
+    if (this.menu) {
+      this.menu.removeEventListener("keydown", this.onMenuKey)
+      this.menu.removeEventListener("click", this.onMenuClick)
+      if (this.menu.matches(":popover-open")) this.menu.hidePopover()
+    }
+    document.removeEventListener("pointerdown", this.onDocPointer, true)
   }
 }
 
diff --git a/lib/mv_web/live/components/member_name_sort_header.ex b/lib/mv_web/live/components/member_name_sort_header.ex
new file mode 100644
index 00000000..76c233f2
--- /dev/null
+++ b/lib/mv_web/live/components/member_name_sort_header.ex
@@ -0,0 +1,142 @@
+defmodule MvWeb.Components.MemberNameSortHeader do
+  @moduledoc """
+  Header for the composite "Member" overview column (§1.21 / U3).
+
+  The column shows the full name (and, when folded in, the email), so a plain
+  "sort by X" is ambiguous. This header keeps the familiar one-click sort of the
+  other columns — a click toggles the direction of the currently active sub-field
+  (last name by default) — and adds a small sub-field menu (the "⋮" button) to
+  switch between sorting by last name and first name. The active sub-field is
+  shown next to the direction chevron only while this column is the active sort,
+  so the header stays uncluttered otherwise but is never ambiguous when it does
+  sort.
+
+  The sub-field menu is rendered as a native Popover (top layer) so it escapes
+  the overview table's overflow clipping; the `SubfieldMenu` JS hook toggles and
+  positions it. Menu items emit `sort_composite` (always ascending by the chosen
+  field); the header click emits `sort` (toggles direction of the active field).
+  """
+  use MvWeb, :html
+
+  @subfields [:first_name, :last_name]
+
+  attr :sort_field, :any, required: true, doc: "current sort field (atom or string)"
+  attr :sort_order, :atom, required: true, doc: ":asc or :desc"
+
+  def composite_name_sort_header(assigns) do
+    active = active_subfield(assigns.sort_field)
+
+    assigns =
+      assigns
+      |> assign(:active, active)
+      |> assign(:subfields, @subfields)
+      # A click on the header sorts by the active sub-field (toggling direction);
+      # when this column is not the active sort it starts from last name.
+      |> assign(:click_field, active || :last_name)
+
+    ~H"""
+    <div class="flex items-center gap-1">
+      <button
+        id="sort-btn-member"
+        type="button"
+        phx-click="sort"
+        phx-value-field={@click_field}
+        aria-describedby="sort-tooltip-member"
+        phx-hook="PopoverTooltip"
+        data-tooltip-id="sort-tooltip-member"
+        class="link link-hover no-underline flex items-center gap-1 text-left text-current select-none"
+        data-testid="name"
+      >
+        {gettext("Member")}
+        <span :if={@active} class="opacity-70 font-normal">
+          · {subfield_label(@active)}
+        </span>
+        <.icon
+          :if={@active && @sort_order == :asc}
+          name="hero-chevron-up"
+          class="sort-icon"
+        />
+        <.icon
+          :if={@active && @sort_order == :desc}
+          name="hero-chevron-down"
+          class="sort-icon"
+        />
+        <.icon :if={!@active} name="hero-chevron-up-down" class="sort-icon opacity-40" />
+      </button>
+      <div id="sort-tooltip-member" popover="manual" role="tooltip" class="popover-tooltip">
+        {tooltip_text(@active)}
+      </div>
+
+      <button
+        id="member-subfield-btn"
+        type="button"
+        style="anchor-name: --member-sort-anchor"
+        aria-label={gettext("Choose sort field")}
+        aria-describedby="member-subfield-tooltip"
+        aria-haspopup="menu"
+        aria-expanded="false"
+        phx-hook="SubfieldMenu"
+        data-menu-id="member-subfield-menu"
+        data-tooltip-id="member-subfield-tooltip"
+        class="btn btn-ghost btn-xs btn-square"
+        data-testid="member-sort-subfield"
+      >
+        <.icon name="hero-ellipsis-vertical" class="size-4" />
+      </button>
+      <div
+        id="member-subfield-tooltip"
+        popover="manual"
+        role="tooltip"
+        style="position-anchor: --member-sort-anchor; position-area: bottom span-left; inset: auto"
+        class="popover-tooltip"
+      >
+        {gettext("Choose sort field")}
+      </div>
+      <ul
+        id="member-subfield-menu"
+        popover="manual"
+        role="menu"
+        aria-label={gettext("Sort members by")}
+        style="position-anchor: --member-sort-anchor"
+        class="popover-menu w-44 rounded-box border border-base-300 bg-base-100 p-2 shadow-lg"
+      >
+        <li role="none" class="mb-1 px-2">
+          <span class="font-semibold">{gettext("Sort by")}</span>
+        </li>
+        <li role="separator" class="divider my-1"></li>
+        <li :for={field <- @subfields} role="none">
+          <button
+            type="button"
+            role="menuitemradio"
+            aria-checked={to_string(@active == field)}
+            phx-click="sort_composite"
+            phx-value-field={field}
+            class="flex w-full cursor-pointer items-center gap-2 rounded px-2 py-1 text-left font-normal hover:bg-base-200"
+            data-testid={"member-sort-#{field}"}
+          >
+            <.icon
+              name="hero-check"
+              class={"size-4 text-primary #{if @active != field, do: "invisible"}"}
+            />
+            {subfield_label(field)}
+          </button>
+        </li>
+      </ul>
+    </div>
+    """
+  end
+
+  # Which sub-field this column currently sorts by, or nil when another column is
+  # the active sort. Accepts atoms or the string form that arrives via the URL.
+  defp active_subfield(sort_field) do
+    Enum.find(@subfields, fn f -> to_string(sort_field) == Atom.to_string(f) end)
+  end
+
+  defp subfield_label(:first_name), do: gettext("First name")
+  defp subfield_label(:last_name), do: gettext("Last name")
+
+  # The header already shows the active sub-field and direction, so the tooltip
+  # only needs to convey the click affordance.
+  defp tooltip_text(nil), do: gettext("Click to sort by last name")
+  defp tooltip_text(_active), do: gettext("Click to reverse the sort direction")
+end
diff --git a/lib/mv_web/live/member_live/index.ex b/lib/mv_web/live/member_live/index.ex
index 6933e005..a7ca8b33 100644
--- a/lib/mv_web/live/member_live/index.ex
+++ b/lib/mv_web/live/member_live/index.ex
@@ -172,7 +172,7 @@ defmodule MvWeb.MemberLive.Index do
       socket
       |> Layouts.assign_page_title(gettext("Members"))
       |> assign(:query, "")
-      |> assign_new(:sort_field, fn -> :first_name end)
+      |> assign_new(:sort_field, fn -> :last_name end)
       |> assign_new(:sort_order, fn -> :asc end)
       |> assign(:cycle_status_filter, nil)
       |> assign(:group_filters, %{})
@@ -379,6 +379,22 @@ defmodule MvWeb.MemberLive.Index do
       end
 
     {new_field, new_order} = determine_new_sort(field, socket)
+    {:noreply, apply_sort_change(socket, new_field, new_order)}
+  end
+
+  # The composite "Member" column's sub-field menu (first name / last name) always
+  # sorts ascending by the chosen field: it switches the sort key rather than
+  # toggling direction (a click on the header itself toggles direction).
+  def handle_event("sort_composite", %{"field" => field_str}, socket) do
+    field = String.to_existing_atom(field_str)
+    {:noreply, apply_sort_change(socket, field, :asc)}
+  end
+
+  # Applies a resolved (field, order) sort: updates assigns and the sort-header
+  # components, reloads the keyset stream from page 1, scrolls to top, and syncs
+  # the URL. Shared by the header-click ("sort") and sub-field menu
+  # ("sort_composite") paths.
+  defp apply_sort_change(socket, new_field, new_order) do
     old_field = socket.assigns.sort_field
 
     socket =
@@ -394,8 +410,8 @@ defmodule MvWeb.MemberLive.Index do
     query_params =
       build_query_params(
         opts_for_query_params(socket, %{
-          sort_field: ExportPayload.sort_field(socket.assigns.sort_field),
-          sort_order: ExportPayload.sort_order(socket.assigns.sort_order)
+          sort_field: ExportPayload.sort_field(new_field),
+          sort_order: ExportPayload.sort_order(new_order)
         })
       )
       |> maybe_add_field_selection(
@@ -403,7 +419,7 @@ defmodule MvWeb.MemberLive.Index do
         socket.assigns[:fields_in_url?] || false
       )
 
-    {:noreply, push_reload(socket, ~p"/members?#{query_params}")}
+    push_reload(socket, ~p"/members?#{query_params}")
   end
 
   # -----------------------------------------------------------------
@@ -1488,9 +1504,11 @@ defmodule MvWeb.MemberLive.Index do
   defp determine_field(default, nil), do: default
 
   # Computed/pseudo fields that are nonetheless sortable (they resolve to DB
-  # sort keys in OverviewQuery): groups aggregate and the composite Name/Address
-  # columns. Other computed fields (e.g. membership_fee_status) are not sortable.
-  @sortable_computed_fields [:groups, :name, :address]
+  # sort keys in OverviewQuery): the groups aggregate and the composite Address
+  # column. The composite Member column sorts by its real first/last-name
+  # sub-fields (chosen via its sub-field menu), so it needs no pseudo token here.
+  # Other computed fields (e.g. membership_fee_status) are not sortable.
+  @sortable_computed_fields [:groups, :address]
 
   defp determine_field(default, sf) when is_binary(sf) do
     sortable_strings = Enum.map(@sortable_computed_fields, &Atom.to_string/1)
diff --git a/lib/mv_web/live/member_live/index.html.heex b/lib/mv_web/live/member_live/index.html.heex
index 7709c2cb..b985cba8 100644
--- a/lib/mv_web/live/member_live/index.html.heex
+++ b/lib/mv_web/live/member_live/index.html.heex
@@ -170,17 +170,12 @@
       <:col
         :let={member}
         :if={:name in @member_fields_visible and @compact_member}
-        sort_field={:name}
+        sort_field={if @sort_field in [:first_name, :last_name], do: @sort_field}
         label={
           ~H"""
-          <.live_component
-            module={MvWeb.Components.SortHeaderComponent}
-            id={:sort_name}
-            field={:name}
-            label={gettext("Name")}
+          <MvWeb.Components.MemberNameSortHeader.composite_name_sort_header
             sort_field={@sort_field}
             sort_order={@sort_order}
-            sort_hint={gettext("Click to sort by last name")}
           />
           """
         }
diff --git a/lib/mv_web/live/member_live/index/overview_query.ex b/lib/mv_web/live/member_live/index/overview_query.ex
index ac3051f0..ec187323 100644
--- a/lib/mv_web/live/member_live/index/overview_query.ex
+++ b/lib/mv_web/live/member_live/index/overview_query.ex
@@ -254,12 +254,19 @@ defmodule MvWeb.MemberLive.Index.OverviewQuery do
   defp apply_sort(query, nil, _order, _custom_fields), do: Ash.Query.sort(query, id: :asc)
   defp apply_sort(query, _field, nil, _custom_fields), do: Ash.Query.sort(query, id: :asc)
 
-  # Composite "Member" column: sort by last name then first name. The email that
-  # shares the cell is display-only and does not affect the sort key (§1.21).
-  defp apply_sort(query, field, order, _custom_fields) when field in [:name, "name"] do
+  # Composite "Member" column sub-fields (§1.21). Sorting by one name part uses
+  # the other name part (then id) as a stable tie-breaker; the email that shares
+  # the cell is display-only and never a sort key. Shared by the composite
+  # sub-field menu and the separate first/last-name columns.
+  defp apply_sort(query, field, order, _custom_fields) when field in [:last_name, "last_name"] do
     Ash.Query.sort(query, [{:last_name, order}, {:first_name, order}, {:id, :asc}])
   end
 
+  defp apply_sort(query, field, order, _custom_fields)
+       when field in [:first_name, "first_name"] do
+    Ash.Query.sort(query, [{:first_name, order}, {:last_name, order}, {:id, :asc}])
+  end
+
   # Composite "Address" column: sort by city, then postal code, then street.
   defp apply_sort(query, field, order, _custom_fields) when field in [:address, "address"] do
     Ash.Query.sort(query, [
diff --git a/priv/gettext/de/LC_MESSAGES/default.po b/priv/gettext/de/LC_MESSAGES/default.po
index db07d05f..c8e06949 100644
--- a/priv/gettext/de/LC_MESSAGES/default.po
+++ b/priv/gettext/de/LC_MESSAGES/default.po
@@ -1518,6 +1518,7 @@ msgstr "Mitglieder filtern"
 msgid "First Name"
 msgstr "Vorname"
 
+#: lib/mv_web/live/components/member_name_sort_header.ex
 #: lib/mv_web/live/join_request_live/index.ex
 #: lib/mv_web/live/member_live/index.html.heex
 #, elixir-autogen, elixir-format
@@ -2003,6 +2004,7 @@ msgstr "Letzter Zyklus"
 msgid "Last Name"
 msgstr "Nachname"
 
+#: lib/mv_web/live/components/member_name_sort_header.ex
 #: lib/mv_web/live/join_request_live/index.ex
 #: lib/mv_web/live/member_live/index.html.heex
 #, elixir-autogen, elixir-format
@@ -2349,7 +2351,6 @@ msgstr "Monatliches Intervall – Beitrittszeitraum einbezogen"
 #: lib/mv_web/live/group_live/show.ex
 #: lib/mv_web/live/member_field_live/form_component.ex
 #: lib/mv_web/live/member_field_live/index_component.ex
-#: lib/mv_web/live/member_live/index.html.heex
 #: lib/mv_web/live/membership_fee_settings_live.ex
 #: lib/mv_web/live/membership_fee_type_live/form.ex
 #: lib/mv_web/live/membership_fee_type_live/index.ex
@@ -4204,7 +4205,7 @@ msgstr "Kompaktes Mitglied-Feld"
 msgid "Click to sort by city"
 msgstr "Klicke, um nach Ort zu sortieren"
 
-#: lib/mv_web/live/member_live/index.html.heex
+#: lib/mv_web/live/components/member_name_sort_header.ex
 #, elixir-autogen, elixir-format
 msgid "Click to sort by last name"
 msgstr "Klicke, um nach Nachname zu sortieren"
@@ -4213,3 +4214,28 @@ msgstr "Klicke, um nach Nachname zu sortieren"
 #, elixir-autogen, elixir-format
 msgid "No address"
 msgstr "Keine Adresse"
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Choose sort field"
+msgstr "Sortierfeld wählen"
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Member"
+msgstr "Mitglied"
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Sort members by"
+msgstr "Mitglieder sortieren nach"
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Click to reverse the sort direction"
+msgstr "Klicke, um die Sortierrichtung umzukehren"
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Sort by"
+msgstr "Sortieren nach"
diff --git a/priv/gettext/default.pot b/priv/gettext/default.pot
index c3b21727..f6067afd 100644
--- a/priv/gettext/default.pot
+++ b/priv/gettext/default.pot
@@ -1519,6 +1519,7 @@ msgstr ""
 msgid "First Name"
 msgstr ""
 
+#: lib/mv_web/live/components/member_name_sort_header.ex
 #: lib/mv_web/live/join_request_live/index.ex
 #: lib/mv_web/live/member_live/index.html.heex
 #, elixir-autogen, elixir-format
@@ -2004,6 +2005,7 @@ msgstr ""
 msgid "Last Name"
 msgstr ""
 
+#: lib/mv_web/live/components/member_name_sort_header.ex
 #: lib/mv_web/live/join_request_live/index.ex
 #: lib/mv_web/live/member_live/index.html.heex
 #, elixir-autogen, elixir-format
@@ -2350,7 +2352,6 @@ msgstr ""
 #: lib/mv_web/live/group_live/show.ex
 #: lib/mv_web/live/member_field_live/form_component.ex
 #: lib/mv_web/live/member_field_live/index_component.ex
-#: lib/mv_web/live/member_live/index.html.heex
 #: lib/mv_web/live/membership_fee_settings_live.ex
 #: lib/mv_web/live/membership_fee_type_live/form.ex
 #: lib/mv_web/live/membership_fee_type_live/index.ex
@@ -4204,7 +4205,7 @@ msgstr ""
 msgid "Click to sort by city"
 msgstr ""
 
-#: lib/mv_web/live/member_live/index.html.heex
+#: lib/mv_web/live/components/member_name_sort_header.ex
 #, elixir-autogen, elixir-format
 msgid "Click to sort by last name"
 msgstr ""
@@ -4213,3 +4214,28 @@ msgstr ""
 #, elixir-autogen, elixir-format
 msgid "No address"
 msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Choose sort field"
+msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Member"
+msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Sort members by"
+msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Click to reverse the sort direction"
+msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Sort by"
+msgstr ""
diff --git a/priv/gettext/en/LC_MESSAGES/default.po b/priv/gettext/en/LC_MESSAGES/default.po
index fe871774..ca998f2d 100644
--- a/priv/gettext/en/LC_MESSAGES/default.po
+++ b/priv/gettext/en/LC_MESSAGES/default.po
@@ -1519,6 +1519,7 @@ msgstr ""
 msgid "First Name"
 msgstr ""
 
+#: lib/mv_web/live/components/member_name_sort_header.ex
 #: lib/mv_web/live/join_request_live/index.ex
 #: lib/mv_web/live/member_live/index.html.heex
 #, elixir-autogen, elixir-format, fuzzy
@@ -2004,6 +2005,7 @@ msgstr ""
 msgid "Last Name"
 msgstr ""
 
+#: lib/mv_web/live/components/member_name_sort_header.ex
 #: lib/mv_web/live/join_request_live/index.ex
 #: lib/mv_web/live/member_live/index.html.heex
 #, elixir-autogen, elixir-format, fuzzy
@@ -2350,7 +2352,6 @@ msgstr ""
 #: lib/mv_web/live/group_live/show.ex
 #: lib/mv_web/live/member_field_live/form_component.ex
 #: lib/mv_web/live/member_field_live/index_component.ex
-#: lib/mv_web/live/member_live/index.html.heex
 #: lib/mv_web/live/membership_fee_settings_live.ex
 #: lib/mv_web/live/membership_fee_type_live/form.ex
 #: lib/mv_web/live/membership_fee_type_live/index.ex
@@ -4204,7 +4205,7 @@ msgstr ""
 msgid "Click to sort by city"
 msgstr ""
 
-#: lib/mv_web/live/member_live/index.html.heex
+#: lib/mv_web/live/components/member_name_sort_header.ex
 #, elixir-autogen, elixir-format
 msgid "Click to sort by last name"
 msgstr ""
@@ -4213,3 +4214,28 @@ msgstr ""
 #, elixir-autogen, elixir-format
 msgid "No address"
 msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format, fuzzy
+msgid "Choose sort field"
+msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format, fuzzy
+msgid "Member"
+msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Sort members by"
+msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Click to reverse the sort direction"
+msgstr ""
+
+#: lib/mv_web/live/components/member_name_sort_header.ex
+#, elixir-autogen, elixir-format
+msgid "Sort by"
+msgstr ""
diff --git a/test/mv_web/member_live/index_sort_name_address_test.exs b/test/mv_web/member_live/index_sort_name_address_test.exs
index 519cebc6..3bb4a41b 100644
--- a/test/mv_web/member_live/index_sort_name_address_test.exs
+++ b/test/mv_web/member_live/index_sort_name_address_test.exs
@@ -52,13 +52,13 @@ defmodule MvWeb.MemberLive.IndexSortNameAddressTest do
   end
 
   test "name sort orders by last name then first name, ignoring email", %{actor: actor} do
-    asc = OverviewQuery.build(%{sort_field: :name, sort_order: :asc}) |> read_names(actor)
+    asc = OverviewQuery.build(%{sort_field: :last_name, sort_order: :asc}) |> read_names(actor)
 
     # Both share last name "Meyer"; the first-name tie-breaker orders Anna before
     # Bruno, even though Bruno's email sorts first alphabetically.
     assert asc == [{"Meyer", "Anna"}, {"Meyer", "Bruno"}]
 
-    desc = OverviewQuery.build(%{sort_field: :name, sort_order: :desc}) |> read_names(actor)
+    desc = OverviewQuery.build(%{sort_field: :last_name, sort_order: :desc}) |> read_names(actor)
     assert desc == [{"Meyer", "Bruno"}, {"Meyer", "Anna"}]
   end
 
@@ -81,15 +81,48 @@ defmodule MvWeb.MemberLive.IndexSortNameAddressTest do
   test "clicking the Name header sorts and reflects state in URL and aria-sort", %{conn: conn} do
     {:ok, view, _html} = live(conn, ~p"/members")
 
+    # The composite header sorts by its active sub-field (last name by default).
     view |> element("button[phx-click='sort'][data-testid='name']") |> render_click()
 
     path = assert_patch(view)
-    assert path =~ "sort_field=name"
-    # Exactly one column carries aria-sort (§1.11).
-    assert has_element?(view, "th[aria-sort='ascending']")
+    assert path =~ "sort_field=last_name"
+    # Last name is already the default sort (ascending), so the click toggles it
+    # to descending. Exactly one column carries aria-sort (§1.11).
+    assert has_element?(view, "th[aria-sort='descending']")
     assert render(view) |> aria_sort_count() == 1
   end
 
+  test "the sub-field menu sorts ascending by the chosen field without toggling", %{conn: conn} do
+    {:ok, view, _html} = live(conn, ~p"/members")
+
+    # Pick "first name" from the composite sub-field menu.
+    view |> element("[data-testid='member-sort-first_name']") |> render_click()
+    path = assert_patch(view)
+    assert path =~ "sort_field=first_name"
+    assert path =~ "sort_order=asc"
+    assert has_element?(view, "th[aria-sort='ascending']")
+
+    # Selecting the same sub-field again keeps it ascending: the menu switches the
+    # sort key, it does not toggle direction (that is what a header click does).
+    view |> element("[data-testid='member-sort-first_name']") |> render_click()
+    path2 = assert_patch(view)
+    assert path2 =~ "sort_field=first_name"
+    assert path2 =~ "sort_order=asc"
+  end
+
+  test "after choosing a sub-field, a header click toggles that field's direction", %{conn: conn} do
+    {:ok, view, _html} = live(conn, ~p"/members")
+
+    view |> element("[data-testid='member-sort-first_name']") |> render_click()
+    assert_patch(view)
+
+    # Now sorting by first name ascending; a click on the header toggles to desc.
+    view |> element("button[phx-click='sort'][data-testid='name']") |> render_click()
+    path = assert_patch(view)
+    assert path =~ "sort_field=first_name"
+    assert path =~ "sort_order=desc"
+  end
+
   test "clicking the Address header sorts and reflects state in URL", %{conn: conn} do
     {:ok, view, _html} = live(conn, ~p"/members")
 
diff --git a/test/mv_web/member_live/index_test.exs b/test/mv_web/member_live/index_test.exs
index 3b499de3..fc69c881 100644
--- a/test/mv_web/member_live/index_test.exs
+++ b/test/mv_web/member_live/index_test.exs
@@ -221,11 +221,11 @@ defmodule MvWeb.MemberLive.IndexTest do
       {:ok, view, _html} =
         live(
           conn,
-          "/members?fields=first_name,email,street,house_number,postal_code,city,country,join_date"
+          "/members?fields=last_name,first_name,email,street,house_number,postal_code,city,country,join_date"
         )
 
-      # default ascending sorting with first name
-      assert has_element?(view, "[data-testid='first_name'][aria-label='ascending']")
+      # default ascending sorting on the default sort field (last name)
+      assert has_element?(view, "[data-testid='last_name'][aria-label='ascending']")
 
       sortable_fields = [
         :email,
@@ -295,10 +295,10 @@ defmodule MvWeb.MemberLive.IndexTest do
       conn = conn |> conn_with_oidc_user() |> non_compact()
 
       {:ok, view, _html} =
-        live(conn, "/members?fields=first_name&query=&sort_field=invalid_field&sort_order=asc")
+        live(conn, "/members?fields=last_name&query=&sort_field=invalid_field&sort_order=asc")
 
-      # Should not crash and should show default first name order
-      assert has_element?(view, "[data-testid='first_name'][aria-label='ascending']")
+      # Should not crash and should fall back to the default sort (last name)
+      assert has_element?(view, "[data-testid='last_name'][aria-label='ascending']")
     end
 
     test "handle_params preserves search query with sort params", %{conn: conn} do