diff --git a/docs/database-schema-readme.md b/docs/database-schema-readme.md
index 6bf11de..6e444a5 100644
--- a/docs/database-schema-readme.md
+++ b/docs/database-schema-readme.md
@@ -233,16 +233,22 @@ Settings (1) → MembershipFeeType (0..1)
 ## Full-Text Search
 
 ### Implementation
-- **Trigger:** `members_search_vector_trigger()`
-- **Function:** Automatically updates `search_vector` on INSERT/UPDATE
+- **Trigger** on `members` (INSERT/UPDATE): runs function `members_search_vector_trigger()`
+- **Trigger** on `member_groups` (INSERT/UPDATE/DELETE): `update_member_search_vector_on_member_groups_change` runs function `update_member_search_vector_from_member_groups()`
 - **Index Type:** GIN (Generalized Inverted Index)
 
 ### Weighted Fields
 - **Weight A (highest):** first_name, last_name
-- **Weight B:** email, notes
+- **Weight B:** email, notes, group names (from member_groups → groups)
 - **Weight C:** city, street, house_number, postal_code, custom_field_values
 - **Weight D (lowest):** join_date, exit_date
 
+### Group Names in Search
+Group names are included in the member search vector so that searching for a group name (e.g. "Vorstand") finds all members in that group:
+- Group names are aggregated from `member_groups` joined with `groups` and receive weight 'B'
+- The trigger `update_member_search_vector_on_member_groups_change` runs on INSERT/UPDATE/DELETE on `member_groups` and refreshes the affected member's `search_vector`
+- See migration `20260217120000_add_group_names_to_member_search_vector.exs` (Issue #375)
+
 ### Custom Field Values in Search
 Custom field values are automatically included in the search vector:
 - All custom field values (string, integer, boolean, date, email) are aggregated and added to the search vector
diff --git a/docs/feature-roadmap.md b/docs/feature-roadmap.md
index 67f01c8..41b3d83 100644
--- a/docs/feature-roadmap.md
+++ b/docs/feature-roadmap.md
@@ -81,12 +81,13 @@
 - ✅ User-Member linking (optional 1:1)
 - ✅ Email synchronization between User and Member
 - ✅ **Bulk email copy** - Copy selected members' email addresses to clipboard (Issue #230)
-- ✅ **Groups** - Organize members into groups (PR #378, #382, closes #371, #372, 2026-01-27)
+- ✅ **Groups** - Organize members into groups (PR #378, #382, #423, closes #371, #372, #374, #375, 2026-01/02)
   - Many-to-many relationship with groups
   - Groups management UI (`/groups`)
   - Filter and sort by groups in member list
   - Per-group filter in member list: one row per group with All / Yes / No (All/Alle); URL params `group_<uuid>=in|not_in`
   - Groups displayed in member overview and detail views
+  - Member search includes group names (search by group name finds members in that group; search_vector + trigger on member_groups)
 - ✅ **CSV Import** - Import members from CSV files (PR #359, #394, #395, closes #335, #336, #338, 2026-01-27)
   - Member field import
   - Custom field value import
@@ -97,6 +98,7 @@
 - ✅ [#162](https://git.local-it.org/local-it/mitgliederverwaltung/issues/162) - Fuzzy and substring search (closed 2025-11-12)
 - ✅ [#371](https://git.local-it.org/local-it/mitgliederverwaltung/issues/371) - Add groups resource (closed 2026-01-27)
 - ✅ [#372](https://git.local-it.org/local-it/mitgliederverwaltung/issues/372) - Groups Admin UI (closed 2026-01-27)
+- ✅ [#375](https://git.local-it.org/local-it/mitgliederverwaltung/issues/375) - Search Integration (group names in member search) (implemented 2026-02-17)
 - ✅ [#335](https://git.local-it.org/local-it/mitgliederverwaltung/issues/335) - CSV Import UI (closed 2026-01-27)
 - ✅ [#336](https://git.local-it.org/local-it/mitgliederverwaltung/issues/336) - Config for import limits (closed 2026-01-27)
 - ✅ [#338](https://git.local-it.org/local-it/mitgliederverwaltung/issues/338) - Custom field CSV import (closed 2026-01-27)
diff --git a/docs/groups-architecture.md b/docs/groups-architecture.md
index 0e59409..ca1f07b 100644
--- a/docs/groups-architecture.md
+++ b/docs/groups-architecture.md
@@ -975,9 +975,11 @@ Each functional unit can be implemented as a **separate issue**:
 ### Issue 5: Search Integration
 **Type:** Backend  
 **Estimation:** 2h  
+**Status:** ✅ Implemented (migration `20260217120000_add_group_names_to_member_search_vector.exs`, Issue #375)
+
 **Tasks:**
 - Update search vector trigger to include group names
-- Extend fuzzy search to search group names
+- Extend fuzzy search to search group names (via search_vector; no Elixir change needed)
 - Test search functionality
 
 **Acceptance Criteria:**
diff --git a/lib/membership/custom_field.ex b/lib/membership/custom_field.ex
index ab4ad60..411e95d 100644
--- a/lib/membership/custom_field.ex
+++ b/lib/membership/custom_field.ex
@@ -10,7 +10,7 @@ defmodule Mv.Membership.CustomField do
   ## Attributes
   - `name` - Unique identifier for the custom field (e.g., "phone_mobile", "birthday")
   - `slug` - URL-friendly, immutable identifier automatically generated from name (e.g., "phone-mobile")
-  - `value_type` - Data type constraint (`:string`, `:integer`, `:boolean`, `:date`, `:email`)
+  - `value_type` - Data type constraint (`:string`, `:integer`, `:boolean`, `:date`, `:email`). Immutable after creation.
   - `description` - Optional human-readable description
   - `required` - If true, all members must have this custom field (future feature)
   - `show_in_overview` - If true, this custom field will be displayed in the member overview table and can be sorted
@@ -28,6 +28,7 @@ defmodule Mv.Membership.CustomField do
   ## Constraints
   - Name must be unique across all custom fields
   - Name maximum length: 100 characters
+  - `value_type` cannot be changed after creation (immutable)
   - Deleting a custom field will cascade delete all associated custom field values
 
   ## Calculations
@@ -59,7 +60,7 @@ defmodule Mv.Membership.CustomField do
   end
 
   actions do
-    defaults [:read, :update]
+    defaults [:read]
     default_accept [:name, :value_type, :description, :required, :show_in_overview]
 
     create :create do
@@ -68,6 +69,19 @@ defmodule Mv.Membership.CustomField do
       validate string_length(:slug, min: 1)
     end
 
+    update :update do
+      accept [:name, :description, :required, :show_in_overview]
+      require_atomic? false
+
+      validate fn changeset, _context ->
+        if Ash.Changeset.changing_attribute?(changeset, :value_type) do
+          {:error, field: :value_type, message: "cannot be changed after creation"}
+        else
+          :ok
+        end
+      end
+    end
+
     destroy :destroy_with_values do
       primary? true
     end
diff --git a/lib/mv_web/live/components/sort_header_component.ex b/lib/mv_web/live/components/sort_header_component.ex
index 3817d90..d548efa 100644
--- a/lib/mv_web/live/components/sort_header_component.ex
+++ b/lib/mv_web/live/components/sort_header_component.ex
@@ -26,7 +26,6 @@ defmodule MvWeb.Components.SortHeaderComponent do
         class="btn btn-ghost select-none"
         phx-click="sort"
         phx-value-field={@field}
-        phx-target={@myself}
         data-testid={@field}
       >
         {@label}
@@ -43,12 +42,6 @@ defmodule MvWeb.Components.SortHeaderComponent do
     """
   end
 
-  @impl true
-  def handle_event("sort", %{"field" => field_str}, socket) do
-    send(self(), {:sort, field_str})
-    {:noreply, socket}
-  end
-
   # -------------------------------------------------
   # Hilfsfunktionen für ARIA Attribute & Icon SVG
   # -------------------------------------------------
diff --git a/lib/mv_web/live/custom_field_live/form_component.ex b/lib/mv_web/live/custom_field_live/form_component.ex
index b809a1a..f89f767 100644
--- a/lib/mv_web/live/custom_field_live/form_component.ex
+++ b/lib/mv_web/live/custom_field_live/form_component.ex
@@ -5,7 +5,7 @@ defmodule MvWeb.CustomFieldLive.FormComponent do
   ## Features
   - Create new custom field definitions
   - Edit existing custom fields
-  - Select value type from supported types
+  - Select value type from supported types (only on create; immutable after creation)
   - Set required flag
   - Real-time validation
 
@@ -44,15 +44,50 @@ defmodule MvWeb.CustomFieldLive.FormComponent do
         >
           <.input field={@form[:name]} type="text" label={gettext("Name")} />
 
-          <.input
-            field={@form[:value_type]}
-            type="select"
-            label={gettext("Value type")}
-            options={
-              Ash.Resource.Info.attribute(Mv.Membership.CustomField, :value_type).constraints[:one_of]
-              |> Enum.map(fn type -> {MvWeb.Translations.FieldTypes.label(type), type} end)
-            }
-          />
+          <%= if @custom_field do %>
+            <%!-- Show value_type as read-only input when editing (matches Member Field pattern) --%>
+            <div
+              class="tooltip tooltip-right"
+              data-tip={gettext("Value type cannot be changed after creation")}
+              aria-label={gettext("Value type cannot be changed after creation")}
+            >
+              <fieldset class="mb-2 fieldset">
+                <label>
+                  <span class="mb-1 label flex items-center gap-2">
+                    {gettext("Value type")}
+                    <.icon
+                      name="hero-information-circle"
+                      class="w-4 h-4 text-base-content/60 cursor-help"
+                      aria-hidden="true"
+                    />
+                  </span>
+                  <input
+                    type="text"
+                    name={@form[:value_type].name}
+                    id={@form[:value_type].id}
+                    value={MvWeb.Translations.FieldTypes.label(@custom_field.value_type)}
+                    disabled
+                    readonly
+                    class="w-full input"
+                  />
+                </label>
+              </fieldset>
+            </div>
+          <% else %>
+            <%!-- Show value_type as select when creating --%>
+            <.input
+              field={@form[:value_type]}
+              type="select"
+              label={gettext("Value type")}
+              options={
+                Ash.Resource.Info.attribute(Mv.Membership.CustomField, :value_type).constraints[
+                  :one_of
+                ]
+                |> Enum.map(fn type -> {MvWeb.Translations.FieldTypes.label(type), type} end)
+              }
+            />
+          <% end %>
+
           <.input field={@form[:description]} type="text" label={gettext("Description")} />
           <.input field={@form[:required]} type="checkbox" label={gettext("Required")} />
           <.input
@@ -85,8 +120,16 @@ defmodule MvWeb.CustomFieldLive.FormComponent do
 
   @impl true
   def handle_event("validate", %{"custom_field" => custom_field_params}, socket) do
+    # Remove value_type from params when editing (it's immutable after creation)
+    cleaned_params =
+      if socket.assigns[:custom_field] do
+        Map.delete(custom_field_params, "value_type")
+      else
+        custom_field_params
+      end
+
     {:noreply,
-     assign(socket, form: AshPhoenix.Form.validate(socket.assigns.form, custom_field_params))}
+     assign(socket, form: AshPhoenix.Form.validate(socket.assigns.form, cleaned_params))}
   end
 
   @impl true
@@ -94,7 +137,15 @@ defmodule MvWeb.CustomFieldLive.FormComponent do
     # Actor must be passed from parent (IndexComponent); component socket has no current_user
     actor = socket.assigns[:actor]
 
-    case MvWeb.LiveHelpers.submit_form(socket.assigns.form, custom_field_params, actor) do
+    # Remove value_type from params when editing (it's immutable after creation)
+    cleaned_params =
+      if socket.assigns[:custom_field] do
+        Map.delete(custom_field_params, "value_type")
+      else
+        custom_field_params
+      end
+
+    case MvWeb.LiveHelpers.submit_form(socket.assigns.form, cleaned_params, actor) do
       {:ok, custom_field} ->
         action =
           case socket.assigns.form.source.type do
diff --git a/lib/mv_web/live/member_live/index.ex b/lib/mv_web/live/member_live/index.ex
index 59ee8f9..d391cd2 100644
--- a/lib/mv_web/live/member_live/index.ex
+++ b/lib/mv_web/live/member_live/index.ex
@@ -68,18 +68,15 @@ defmodule MvWeb.MemberLive.Index do
     # This is appropriate for initialization errors that should be visible to the user.
     actor = current_actor(socket)
 
-    custom_fields_visible =
-      Mv.Membership.CustomField
-      |> Ash.Query.filter(expr(show_in_overview == true))
-      |> Ash.Query.sort(name: :asc)
-      |> Ash.read!(actor: actor)
-
-    # Load ALL custom fields for the dropdown (to show all available fields)
     all_custom_fields =
       Mv.Membership.CustomField
       |> Ash.Query.sort(name: :asc)
       |> Ash.read!(actor: actor)
 
+    custom_fields_visible =
+      all_custom_fields
+      |> Enum.filter(& &1.show_in_overview)
+
     # Load boolean custom fields (filtered and sorted from all_custom_fields)
     boolean_custom_fields =
       all_custom_fields
@@ -163,6 +160,7 @@ defmodule MvWeb.MemberLive.Index do
   - `"delete"` - Removes a member from the database
   - `"select_member"` - Toggles individual member selection
   - `"select_all"` - Toggles selection of all visible members
+  - `"sort"` - Sort event from SortHeaderComponent. Updates sort field/order and syncs URL
   """
   @impl true
   def handle_event("delete", %{"id" => id}, socket) do
@@ -305,6 +303,46 @@ defmodule MvWeb.MemberLive.Index do
     end
   end
 
+  @impl true
+  def handle_event("sort", %{"field" => field_str}, socket) do
+    # Handle both atom and string field names (for custom fields)
+    field =
+      try do
+        String.to_existing_atom(field_str)
+      rescue
+        ArgumentError -> field_str
+      end
+
+    {new_field, new_order} = determine_new_sort(field, socket)
+    old_field = socket.assigns.sort_field
+
+    socket =
+      socket
+      |> assign(:sort_field, new_field)
+      |> assign(:sort_order, new_order)
+      |> update_sort_components(old_field, new_field, new_order)
+      |> load_members()
+      |> update_selection_assigns()
+
+    # URL sync - push_patch happens synchronously in the event handler
+    query_params =
+      build_query_params(
+        socket.assigns.query,
+        export_sort_field(socket.assigns.sort_field),
+        export_sort_order(socket.assigns.sort_order),
+        socket.assigns.cycle_status_filter,
+        socket.assigns[:group_filters],
+        socket.assigns.show_current_cycle,
+        socket.assigns.boolean_custom_field_filters
+      )
+      |> maybe_add_field_selection(
+        socket.assigns[:user_field_selection],
+        socket.assigns[:fields_in_url?] || false
+      )
+
+    {:noreply, push_patch(socket, to: ~p"/members?#{query_params}", replace: true)}
+  end
+
   # Helper to format errors for display
   defp format_error(%Ash.Error.Invalid{errors: errors}) do
     error_messages =
@@ -329,50 +367,10 @@ defmodule MvWeb.MemberLive.Index do
   Handles messages from child components.
 
   ## Supported messages:
-  - `{:sort, field}` - Sort event from SortHeaderComponent. Updates sort field/order and syncs URL
   - `{:search_changed, query}` - Search event from SearchBarComponent. Filters members and syncs URL
   - `{:field_toggled, field, visible}` - Field toggle event from FieldVisibilityDropdownComponent
   - `{:fields_selected, selection}` - Select all/deselect all event from FieldVisibilityDropdownComponent
   """
-  @impl true
-  def handle_info({:sort, field_str}, socket) do
-    # Handle both atom and string field names (for custom fields)
-    field =
-      try do
-        String.to_existing_atom(field_str)
-      rescue
-        ArgumentError -> field_str
-      end
-
-    {new_field, new_order} = determine_new_sort(field, socket)
-    old_field = socket.assigns.sort_field
-
-    socket =
-      socket
-      |> assign(:sort_field, new_field)
-      |> assign(:sort_order, new_order)
-      |> update_sort_components(old_field, new_field, new_order)
-      |> load_members()
-      |> update_selection_assigns()
-
-    # URL sync
-    query_params =
-      build_query_params(
-        socket.assigns.query,
-        export_sort_field(socket.assigns.sort_field),
-        export_sort_order(socket.assigns.sort_order),
-        socket.assigns.cycle_status_filter,
-        socket.assigns[:group_filters],
-        socket.assigns.show_current_cycle,
-        socket.assigns.boolean_custom_field_filters
-      )
-      |> maybe_add_field_selection(
-        socket.assigns[:user_field_selection],
-        socket.assigns[:fields_in_url?] || false
-      )
-
-    {:noreply, push_patch(socket, to: ~p"/members?#{query_params}", replace: true)}
-  end
 
   @impl true
   def handle_info({:search_changed, q}, socket) do
diff --git a/priv/gettext/de/LC_MESSAGES/default.po b/priv/gettext/de/LC_MESSAGES/default.po
index 29e4a0d..31de1c2 100644
--- a/priv/gettext/de/LC_MESSAGES/default.po
+++ b/priv/gettext/de/LC_MESSAGES/default.po
@@ -2617,6 +2617,11 @@ msgstr "PDF"
 msgid "Import"
 msgstr "Import"
 
+#: lib/mv_web/live/custom_field_live/form_component.ex
+#, elixir-autogen, elixir-format
+msgid "Value type cannot be changed after creation"
+msgstr "Der Wertetyp kann nach dem Erstellen nicht mehr geändert werden."
+
 #~ #: lib/mv_web/live/import_export_live.ex
 #~ #, elixir-autogen, elixir-format, fuzzy
 #~ msgid "Export Members (CSV)"
diff --git a/priv/gettext/default.pot b/priv/gettext/default.pot
index eeb65fe..0ab0302 100644
--- a/priv/gettext/default.pot
+++ b/priv/gettext/default.pot
@@ -2617,3 +2617,8 @@ msgstr ""
 #, elixir-autogen, elixir-format
 msgid "Import"
 msgstr ""
+
+#: lib/mv_web/live/custom_field_live/form_component.ex
+#, elixir-autogen, elixir-format
+msgid "Value type cannot be changed after creation"
+msgstr ""
diff --git a/priv/gettext/en/LC_MESSAGES/default.po b/priv/gettext/en/LC_MESSAGES/default.po
index 57e2447..199173b 100644
--- a/priv/gettext/en/LC_MESSAGES/default.po
+++ b/priv/gettext/en/LC_MESSAGES/default.po
@@ -2618,6 +2618,11 @@ msgstr ""
 msgid "Import"
 msgstr ""
 
+#: lib/mv_web/live/custom_field_live/form_component.ex
+#, elixir-autogen, elixir-format
+msgid "Value type cannot be changed after creation"
+msgstr ""
+
 #~ #: lib/mv_web/live/import_export_live.ex
 #~ #, elixir-autogen, elixir-format, fuzzy
 #~ msgid "Export Members (CSV)"
diff --git a/priv/repo/migrations/20260217120000_add_group_names_to_member_search_vector.exs b/priv/repo/migrations/20260217120000_add_group_names_to_member_search_vector.exs
new file mode 100644
index 0000000..5508f16
--- /dev/null
+++ b/priv/repo/migrations/20260217120000_add_group_names_to_member_search_vector.exs
@@ -0,0 +1,466 @@
+defmodule Mv.Repo.Migrations.AddGroupNamesToMemberSearchVector do
+  @moduledoc """
+  Includes group names in member search_vector for full-text search (Issue #375).
+
+  This migration:
+  1. Updates members_search_vector_trigger() to include group names (weight B)
+  2. Updates update_member_search_vector_from_custom_field_value() to include group names
+  3. Creates trigger on member_groups to refresh member search_vector when associations change
+  4. Backfills existing members' search_vector with group names
+  """
+
+  use Ecto.Migration
+
+  def up do
+    # 1. Main trigger on members: add group names to search_vector
+    execute("""
+    CREATE OR REPLACE FUNCTION members_search_vector_trigger() RETURNS trigger AS $$
+    DECLARE
+      custom_values_text text;
+      groups_text text;
+    BEGIN
+      -- Aggregate all custom field values for this member
+      SELECT string_agg(
+        CASE
+          WHEN value ? '_union_value' THEN value->>'_union_value'
+          WHEN value ? 'value' THEN value->>'value'
+          ELSE ''
+        END,
+        ' '
+      )
+      INTO custom_values_text
+      FROM custom_field_values
+      WHERE member_id = NEW.id AND value IS NOT NULL;
+
+      -- Aggregate group names for this member (weight B, same as notes/email)
+      SELECT string_agg(g.name, ' ')
+      INTO groups_text
+      FROM member_groups mg
+      JOIN groups g ON g.id = mg.group_id
+      WHERE mg.member_id = NEW.id;
+
+      -- Build search_vector with member fields, custom field values, and group names
+      NEW.search_vector :=
+        setweight(to_tsvector('simple', coalesce(NEW.first_name, '')), 'A') ||
+        setweight(to_tsvector('simple', coalesce(NEW.last_name, '')), 'A') ||
+        setweight(to_tsvector('simple', coalesce(NEW.email, '')), 'B') ||
+        setweight(to_tsvector('simple', coalesce(NEW.join_date::text, '')), 'D') ||
+        setweight(to_tsvector('simple', coalesce(NEW.exit_date::text, '')), 'D') ||
+        setweight(to_tsvector('simple', coalesce(NEW.notes, '')), 'B') ||
+        setweight(to_tsvector('simple', coalesce(NEW.city, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(NEW.street, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(NEW.house_number::text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(NEW.postal_code::text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(custom_values_text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(groups_text, '')), 'B');
+      RETURN NEW;
+    END
+    $$ LANGUAGE plpgsql;
+    """)
+
+    # 2. Custom field trigger: when custom_field_values change, include group names in recomputed search_vector
+    execute("""
+    CREATE OR REPLACE FUNCTION update_member_search_vector_from_custom_field_value() RETURNS trigger AS $$
+    DECLARE
+      member_id_val uuid;
+      member_first_name text;
+      member_last_name text;
+      member_email text;
+      member_join_date date;
+      member_exit_date date;
+      member_notes text;
+      member_city text;
+      member_street text;
+      member_house_number text;
+      member_postal_code text;
+      custom_values_text text;
+      groups_text text;
+      old_value_text text;
+      new_value_text text;
+    BEGIN
+      member_id_val := COALESCE(NEW.member_id, OLD.member_id);
+
+      IF TG_OP = 'UPDATE' THEN
+        old_value_text := COALESCE(
+          NULLIF(OLD.value->>'_union_value', ''),
+          NULLIF(OLD.value->>'value', ''),
+          ''
+        );
+        new_value_text := COALESCE(
+          NULLIF(NEW.value->>'_union_value', ''),
+          NULLIF(NEW.value->>'value', ''),
+          ''
+        );
+        IF (old_value_text IS NOT DISTINCT FROM new_value_text) AND
+           (OLD.member_id IS NOT DISTINCT FROM NEW.member_id) AND
+           (OLD.custom_field_id IS NOT DISTINCT FROM NEW.custom_field_id) THEN
+          RETURN COALESCE(NEW, OLD);
+        END IF;
+      END IF;
+
+      SELECT
+        first_name,
+        last_name,
+        email,
+        join_date,
+        exit_date,
+        notes,
+        city,
+        street,
+        house_number,
+        postal_code
+      INTO
+        member_first_name,
+        member_last_name,
+        member_email,
+        member_join_date,
+        member_exit_date,
+        member_notes,
+        member_city,
+        member_street,
+        member_house_number,
+        member_postal_code
+      FROM members
+      WHERE id = member_id_val;
+
+      SELECT string_agg(
+        CASE
+          WHEN value ? '_union_value' THEN value->>'_union_value'
+          WHEN value ? 'value' THEN value->>'value'
+          ELSE ''
+        END,
+        ' '
+      )
+      INTO custom_values_text
+      FROM custom_field_values
+      WHERE member_id = member_id_val AND value IS NOT NULL;
+
+      SELECT string_agg(g.name, ' ')
+      INTO groups_text
+      FROM member_groups mg
+      JOIN groups g ON g.id = mg.group_id
+      WHERE mg.member_id = member_id_val;
+
+      UPDATE members
+      SET search_vector =
+        setweight(to_tsvector('simple', coalesce(member_first_name, '')), 'A') ||
+        setweight(to_tsvector('simple', coalesce(member_last_name, '')), 'A') ||
+        setweight(to_tsvector('simple', coalesce(member_email, '')), 'B') ||
+        setweight(to_tsvector('simple', coalesce(member_join_date::text, '')), 'D') ||
+        setweight(to_tsvector('simple', coalesce(member_exit_date::text, '')), 'D') ||
+        setweight(to_tsvector('simple', coalesce(member_notes, '')), 'B') ||
+        setweight(to_tsvector('simple', coalesce(member_city, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(member_street, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(member_house_number::text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(member_postal_code::text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(custom_values_text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(groups_text, '')), 'B')
+      WHERE id = member_id_val;
+
+      RETURN COALESCE(NEW, OLD);
+    END
+    $$ LANGUAGE plpgsql;
+    """)
+
+    # 3. Trigger on member_groups: when associations change, refresh affected member(s) search_vector.
+    # On UPDATE with different member_id, refresh both OLD and NEW member so neither keeps a stale vector.
+    execute("""
+    CREATE FUNCTION update_member_search_vector_from_member_groups() RETURNS trigger AS $$
+    DECLARE
+      member_id_val uuid;
+      member_first_name text;
+      member_last_name text;
+      member_email text;
+      member_join_date date;
+      member_exit_date date;
+      member_notes text;
+      member_city text;
+      member_street text;
+      member_house_number text;
+      member_postal_code text;
+      custom_values_text text;
+      groups_text text;
+    BEGIN
+      FOR member_id_val IN
+        SELECT COALESCE(NEW.member_id, OLD.member_id)
+        UNION ALL
+        SELECT OLD.member_id
+        WHERE TG_OP = 'UPDATE' AND OLD.member_id IS DISTINCT FROM NEW.member_id
+      LOOP
+        SELECT
+          first_name,
+          last_name,
+          email,
+          join_date,
+          exit_date,
+          notes,
+          city,
+          street,
+          house_number,
+          postal_code
+        INTO
+          member_first_name,
+          member_last_name,
+          member_email,
+          member_join_date,
+          member_exit_date,
+          member_notes,
+          member_city,
+          member_street,
+          member_house_number,
+          member_postal_code
+        FROM members
+        WHERE id = member_id_val;
+
+        SELECT string_agg(
+          CASE
+            WHEN value ? '_union_value' THEN value->>'_union_value'
+            WHEN value ? 'value' THEN value->>'value'
+            ELSE ''
+          END,
+          ' '
+        )
+        INTO custom_values_text
+        FROM custom_field_values
+        WHERE member_id = member_id_val AND value IS NOT NULL;
+
+        SELECT string_agg(g.name, ' ')
+        INTO groups_text
+        FROM member_groups mg
+        JOIN groups g ON g.id = mg.group_id
+        WHERE mg.member_id = member_id_val;
+
+        UPDATE members
+        SET search_vector =
+          setweight(to_tsvector('simple', coalesce(member_first_name, '')), 'A') ||
+          setweight(to_tsvector('simple', coalesce(member_last_name, '')), 'A') ||
+          setweight(to_tsvector('simple', coalesce(member_email, '')), 'B') ||
+          setweight(to_tsvector('simple', coalesce(member_join_date::text, '')), 'D') ||
+          setweight(to_tsvector('simple', coalesce(member_exit_date::text, '')), 'D') ||
+          setweight(to_tsvector('simple', coalesce(member_notes, '')), 'B') ||
+          setweight(to_tsvector('simple', coalesce(member_city, '')), 'C') ||
+          setweight(to_tsvector('simple', coalesce(member_street, '')), 'C') ||
+          setweight(to_tsvector('simple', coalesce(member_house_number::text, '')), 'C') ||
+          setweight(to_tsvector('simple', coalesce(member_postal_code::text, '')), 'C') ||
+          setweight(to_tsvector('simple', coalesce(custom_values_text, '')), 'C') ||
+          setweight(to_tsvector('simple', coalesce(groups_text, '')), 'B')
+        WHERE id = member_id_val;
+      END LOOP;
+
+      RETURN COALESCE(NEW, OLD);
+    END
+    $$ LANGUAGE plpgsql;
+    """)
+
+    execute("""
+    CREATE TRIGGER update_member_search_vector_on_member_groups_change
+    AFTER INSERT OR UPDATE OR DELETE ON member_groups
+    FOR EACH ROW
+    EXECUTE FUNCTION update_member_search_vector_from_member_groups()
+    """)
+
+    # 4. Backfill: update all members' search_vector to include group names
+    execute("""
+    UPDATE members m
+    SET search_vector =
+      setweight(to_tsvector('simple', coalesce(m.first_name, '')), 'A') ||
+      setweight(to_tsvector('simple', coalesce(m.last_name, '')), 'A') ||
+      setweight(to_tsvector('simple', coalesce(m.email, '')), 'B') ||
+      setweight(to_tsvector('simple', coalesce(m.join_date::text, '')), 'D') ||
+      setweight(to_tsvector('simple', coalesce(m.exit_date::text, '')), 'D') ||
+      setweight(to_tsvector('simple', coalesce(m.notes, '')), 'B') ||
+      setweight(to_tsvector('simple', coalesce(m.city, '')), 'C') ||
+      setweight(to_tsvector('simple', coalesce(m.street, '')), 'C') ||
+      setweight(to_tsvector('simple', coalesce(m.house_number::text, '')), 'C') ||
+      setweight(to_tsvector('simple', coalesce(m.postal_code::text, '')), 'C') ||
+      setweight(to_tsvector('simple', coalesce(
+        (SELECT string_agg(
+          CASE
+            WHEN value ? '_union_value' THEN value->>'_union_value'
+            WHEN value ? 'value' THEN value->>'value'
+            ELSE ''
+          END,
+          ' '
+        )
+        FROM custom_field_values
+        WHERE member_id = m.id AND value IS NOT NULL),
+        ''
+      )), 'C') ||
+      setweight(to_tsvector('simple', coalesce(
+        (SELECT string_agg(g.name, ' ')
+         FROM member_groups mg
+         JOIN groups g ON g.id = mg.group_id
+         WHERE mg.member_id = m.id),
+        ''
+      )), 'B')
+    """)
+  end
+
+  def down do
+    execute(
+      "DROP TRIGGER IF EXISTS update_member_search_vector_on_member_groups_change ON member_groups"
+    )
+
+    execute("DROP FUNCTION IF EXISTS update_member_search_vector_from_member_groups()")
+
+    # Restore members_search_vector_trigger without group names
+    execute("""
+    CREATE OR REPLACE FUNCTION members_search_vector_trigger() RETURNS trigger AS $$
+    DECLARE
+      custom_values_text text;
+    BEGIN
+      SELECT string_agg(
+        CASE
+          WHEN value ? '_union_value' THEN value->>'_union_value'
+          WHEN value ? 'value' THEN value->>'value'
+          ELSE ''
+        END,
+        ' '
+      )
+      INTO custom_values_text
+      FROM custom_field_values
+      WHERE member_id = NEW.id AND value IS NOT NULL;
+
+      NEW.search_vector :=
+        setweight(to_tsvector('simple', coalesce(NEW.first_name, '')), 'A') ||
+        setweight(to_tsvector('simple', coalesce(NEW.last_name, '')), 'A') ||
+        setweight(to_tsvector('simple', coalesce(NEW.email, '')), 'B') ||
+        setweight(to_tsvector('simple', coalesce(NEW.join_date::text, '')), 'D') ||
+        setweight(to_tsvector('simple', coalesce(NEW.exit_date::text, '')), 'D') ||
+        setweight(to_tsvector('simple', coalesce(NEW.notes, '')), 'B') ||
+        setweight(to_tsvector('simple', coalesce(NEW.city, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(NEW.street, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(NEW.house_number::text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(NEW.postal_code::text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(custom_values_text, '')), 'C');
+      RETURN NEW;
+    END
+    $$ LANGUAGE plpgsql;
+    """)
+
+    # Restore update_member_search_vector_from_custom_field_value without group names
+    execute("""
+    CREATE OR REPLACE FUNCTION update_member_search_vector_from_custom_field_value() RETURNS trigger AS $$
+    DECLARE
+      member_id_val uuid;
+      member_first_name text;
+      member_last_name text;
+      member_email text;
+      member_join_date date;
+      member_exit_date date;
+      member_notes text;
+      member_city text;
+      member_street text;
+      member_house_number text;
+      member_postal_code text;
+      custom_values_text text;
+      old_value_text text;
+      new_value_text text;
+    BEGIN
+      member_id_val := COALESCE(NEW.member_id, OLD.member_id);
+
+      IF TG_OP = 'UPDATE' THEN
+        old_value_text := COALESCE(
+          NULLIF(OLD.value->>'_union_value', ''),
+          NULLIF(OLD.value->>'value', ''),
+          ''
+        );
+        new_value_text := COALESCE(
+          NULLIF(NEW.value->>'_union_value', ''),
+          NULLIF(NEW.value->>'value', ''),
+          ''
+        );
+        IF (old_value_text IS NOT DISTINCT FROM new_value_text) AND
+           (OLD.member_id IS NOT DISTINCT FROM NEW.member_id) AND
+           (OLD.custom_field_id IS NOT DISTINCT FROM NEW.custom_field_id) THEN
+          RETURN COALESCE(NEW, OLD);
+        END IF;
+      END IF;
+
+      SELECT
+        first_name,
+        last_name,
+        email,
+        join_date,
+        exit_date,
+        notes,
+        city,
+        street,
+        house_number,
+        postal_code
+      INTO
+        member_first_name,
+        member_last_name,
+        member_email,
+        member_join_date,
+        member_exit_date,
+        member_notes,
+        member_city,
+        member_street,
+        member_house_number,
+        member_postal_code
+      FROM members
+      WHERE id = member_id_val;
+
+      SELECT string_agg(
+        CASE
+          WHEN value ? '_union_value' THEN value->>'_union_value'
+          WHEN value ? 'value' THEN value->>'value'
+          ELSE ''
+        END,
+        ' '
+      )
+      INTO custom_values_text
+      FROM custom_field_values
+      WHERE member_id = member_id_val AND value IS NOT NULL;
+
+      UPDATE members
+      SET search_vector =
+        setweight(to_tsvector('simple', coalesce(member_first_name, '')), 'A') ||
+        setweight(to_tsvector('simple', coalesce(member_last_name, '')), 'A') ||
+        setweight(to_tsvector('simple', coalesce(member_email, '')), 'B') ||
+        setweight(to_tsvector('simple', coalesce(member_join_date::text, '')), 'D') ||
+        setweight(to_tsvector('simple', coalesce(member_exit_date::text, '')), 'D') ||
+        setweight(to_tsvector('simple', coalesce(member_notes, '')), 'B') ||
+        setweight(to_tsvector('simple', coalesce(member_city, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(member_street, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(member_house_number::text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(member_postal_code::text, '')), 'C') ||
+        setweight(to_tsvector('simple', coalesce(custom_values_text, '')), 'C')
+      WHERE id = member_id_val;
+
+      RETURN COALESCE(NEW, OLD);
+    END
+    $$ LANGUAGE plpgsql;
+    """)
+
+    # Backfill without group names
+    execute("""
+    UPDATE members m
+    SET search_vector =
+      setweight(to_tsvector('simple', coalesce(m.first_name, '')), 'A') ||
+      setweight(to_tsvector('simple', coalesce(m.last_name, '')), 'A') ||
+      setweight(to_tsvector('simple', coalesce(m.email, '')), 'B') ||
+      setweight(to_tsvector('simple', coalesce(m.join_date::text, '')), 'D') ||
+      setweight(to_tsvector('simple', coalesce(m.exit_date::text, '')), 'D') ||
+      setweight(to_tsvector('simple', coalesce(m.notes, '')), 'B') ||
+      setweight(to_tsvector('simple', coalesce(m.city, '')), 'C') ||
+      setweight(to_tsvector('simple', coalesce(m.street, '')), 'C') ||
+      setweight(to_tsvector('simple', coalesce(m.house_number::text, '')), 'C') ||
+      setweight(to_tsvector('simple', coalesce(m.postal_code::text, '')), 'C') ||
+      setweight(to_tsvector('simple', coalesce(
+        (SELECT string_agg(
+          CASE
+            WHEN value ? '_union_value' THEN value->>'_union_value'
+            WHEN value ? 'value' THEN value->>'value'
+            ELSE ''
+          END,
+          ' '
+        )
+        FROM custom_field_values
+        WHERE member_id = m.id AND value IS NOT NULL),
+        ''
+      )), 'C')
+    """)
+  end
+end
diff --git a/test/membership/custom_field_validation_test.exs b/test/membership/custom_field_validation_test.exs
index d0711ad..e642d82 100644
--- a/test/membership/custom_field_validation_test.exs
+++ b/test/membership/custom_field_validation_test.exs
@@ -8,6 +8,7 @@ defmodule Mv.Membership.CustomFieldValidationTest do
   - Description length validation (max 500 characters)
   - Description trimming
   - Required vs optional fields
+  - Value type immutability (cannot be changed after creation)
   """
   use Mv.DataCase, async: true
 
@@ -207,4 +208,101 @@ defmodule Mv.Membership.CustomFieldValidationTest do
       assert [%{field: :value_type}] = changeset.errors
     end
   end
+
+  describe "value_type immutability" do
+    test "rejects attempt to change value_type after creation", %{actor: actor} do
+      # Create custom field with value_type :string
+      {:ok, custom_field} =
+        CustomField
+        |> Ash.Changeset.for_create(:create, %{
+          name: "test_field",
+          value_type: :string
+        })
+        |> Ash.create(actor: actor)
+
+      original_value_type = custom_field.value_type
+      assert original_value_type == :string
+
+      # Attempt to update value_type to :integer
+      assert {:error, %Ash.Error.Invalid{} = error} =
+               custom_field
+               |> Ash.Changeset.for_update(:update, %{
+                 value_type: :integer
+               })
+               |> Ash.update(actor: actor)
+
+      # Verify error message contains expected text
+      error_message = Exception.message(error)
+      assert error_message =~ "cannot be changed" or error_message =~ "value_type"
+
+      # Reload and verify value_type remained unchanged
+      reloaded = Ash.get!(CustomField, custom_field.id, actor: actor)
+      assert reloaded.value_type == original_value_type
+      assert reloaded.value_type == :string
+    end
+
+    test "allows updating other fields while value_type remains unchanged", %{actor: actor} do
+      # Create custom field with value_type :string
+      {:ok, custom_field} =
+        CustomField
+        |> Ash.Changeset.for_create(:create, %{
+          name: "test_field",
+          value_type: :string,
+          description: "Original description"
+        })
+        |> Ash.create(actor: actor)
+
+      original_value_type = custom_field.value_type
+      assert original_value_type == :string
+
+      # Update other fields (name, description) without touching value_type
+      {:ok, updated_custom_field} =
+        custom_field
+        |> Ash.Changeset.for_update(:update, %{
+          name: "updated_name",
+          description: "Updated description"
+        })
+        |> Ash.update(actor: actor)
+
+      # Verify value_type remained unchanged
+      assert updated_custom_field.value_type == original_value_type
+      assert updated_custom_field.value_type == :string
+      # Verify other fields were updated
+      assert updated_custom_field.name == "updated_name"
+      assert updated_custom_field.description == "Updated description"
+    end
+
+    test "rejects value_type change even when other fields are updated", %{actor: actor} do
+      # Create custom field with value_type :boolean
+      {:ok, custom_field} =
+        CustomField
+        |> Ash.Changeset.for_create(:create, %{
+          name: "test_field",
+          value_type: :boolean
+        })
+        |> Ash.create(actor: actor)
+
+      original_value_type = custom_field.value_type
+      assert original_value_type == :boolean
+
+      # Attempt to update both name and value_type
+      assert {:error, %Ash.Error.Invalid{} = error} =
+               custom_field
+               |> Ash.Changeset.for_update(:update, %{
+                 name: "updated_name",
+                 value_type: :date
+               })
+               |> Ash.update(actor: actor)
+
+      # Verify error message
+      error_message = Exception.message(error)
+      assert error_message =~ "cannot be changed" or error_message =~ "value_type"
+
+      # Reload and verify value_type remained unchanged, but name was not updated either
+      reloaded = Ash.get!(CustomField, custom_field.id, actor: actor)
+      assert reloaded.value_type == original_value_type
+      assert reloaded.value_type == :boolean
+      assert reloaded.name == "test_field"
+    end
+  end
 end
diff --git a/test/membership/member_search_groups_integration_test.exs b/test/membership/member_search_groups_integration_test.exs
new file mode 100644
index 0000000..f6d7aa8
--- /dev/null
+++ b/test/membership/member_search_groups_integration_test.exs
@@ -0,0 +1,386 @@
+defmodule Mv.Membership.MemberSearchGroupsIntegrationTest do
+  @moduledoc """
+  Tests for member search integration with group names (Issue #375).
+
+  Verifies that:
+  - Group names are included in member search (via search_vector / FTS)
+  - Searching by group name returns all members in that group
+  - Search vector updates when member-group associations change (trigger on member_groups)
+  - Edge cases (multiple groups, no groups, special characters) and authorization
+
+  Implementation: search_vector trigger and trigger on member_groups
+  (see migration 20260217120000_add_group_names_to_member_search_vector.exs, Issue #375).
+  """
+  use Mv.DataCase, async: false
+
+  alias Mv.Helpers.SystemActor
+  alias Mv.Membership.{Group, Member, MemberGroup}
+
+  setup do
+    system_actor = SystemActor.get_system_actor()
+    %{system_actor: system_actor}
+  end
+
+  describe "search by group name" do
+    test "search by group name finds member in that group", %{system_actor: actor} do
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Anna", last_name: "Arbeiter", email: "anna@example.com"},
+          actor: actor
+        )
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Vorstand"})
+        |> Ash.create(actor: actor)
+
+      {:ok, _mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: actor)
+
+      results =
+        Member
+        |> Member.fuzzy_search(%{query: "Vorstand"})
+        |> Ash.read!(actor: actor)
+
+      assert length(results) == 1
+      assert List.first(results).id == member.id
+    end
+
+    test "search by group name finds all members in that group", %{system_actor: actor} do
+      {:ok, m1} =
+        Mv.Membership.create_member(
+          %{first_name: "Bob", last_name: "Brown", email: "bob1@example.com"},
+          actor: actor
+        )
+
+      {:ok, m2} =
+        Mv.Membership.create_member(
+          %{first_name: "Beth", last_name: "Blue", email: "beth@example.com"},
+          actor: actor
+        )
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Board Members"})
+        |> Ash.create(actor: actor)
+
+      for member <- [m1, m2] do
+        {:ok, _} =
+          MemberGroup
+          |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+          |> Ash.create(actor: actor)
+      end
+
+      results =
+        Member
+        |> Member.fuzzy_search(%{query: "Board Members"})
+        |> Ash.read!(actor: actor)
+
+      ids = Enum.map(results, & &1.id)
+      assert m1.id in ids
+      assert m2.id in ids
+      assert length(results) == 2
+    end
+
+    test "member in multiple groups is findable by any of those group names", %{
+      system_actor: actor
+    } do
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Clara", last_name: "Clark", email: "clara@example.com"},
+          actor: actor
+        )
+
+      {:ok, g1} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Alpha Team"})
+        |> Ash.create(actor: actor)
+
+      {:ok, g2} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Beta Team"})
+        |> Ash.create(actor: actor)
+
+      for {m, g} <- [{member, g1}, {member, g2}] do
+        {:ok, _} =
+          MemberGroup
+          |> Ash.Changeset.for_create(:create, %{member_id: m.id, group_id: g.id})
+          |> Ash.create(actor: actor)
+      end
+
+      for group_name <- ["Alpha Team", "Beta Team"] do
+        results =
+          Member
+          |> Member.fuzzy_search(%{query: group_name})
+          |> Ash.read!(actor: actor)
+
+        assert Enum.any?(results, fn r -> r.id == member.id end),
+               "Search for #{group_name} should find member"
+      end
+    end
+
+    test "search by group name does not return members not in that group", %{
+      system_actor: actor
+    } do
+      {:ok, member_in_x} =
+        Mv.Membership.create_member(
+          %{first_name: "Xavier", last_name: "X", email: "xavier@example.com"},
+          actor: actor
+        )
+
+      {:ok, member_in_y} =
+        Mv.Membership.create_member(
+          %{first_name: "Yvonne", last_name: "Y", email: "yvonne@example.com"},
+          actor: actor
+        )
+
+      {:ok, group_x} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "GroupXOnly"})
+        |> Ash.create(actor: actor)
+
+      {:ok, group_y} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "GroupYOnly"})
+        |> Ash.create(actor: actor)
+
+      {:ok, _} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member_in_x.id, group_id: group_x.id})
+        |> Ash.create(actor: actor)
+
+      {:ok, _} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member_in_y.id, group_id: group_y.id})
+        |> Ash.create(actor: actor)
+
+      results_x =
+        Member
+        |> Member.fuzzy_search(%{query: "GroupXOnly"})
+        |> Ash.read!(actor: actor)
+
+      assert Enum.any?(results_x, fn r -> r.id == member_in_x.id end)
+      refute Enum.any?(results_x, fn r -> r.id == member_in_y.id end)
+
+      results_y =
+        Member
+        |> Member.fuzzy_search(%{query: "GroupYOnly"})
+        |> Ash.read!(actor: actor)
+
+      assert Enum.any?(results_y, fn r -> r.id == member_in_y.id end)
+      refute Enum.any?(results_y, fn r -> r.id == member_in_x.id end)
+    end
+
+    test "member with no groups is not found by unrelated group name", %{system_actor: actor} do
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Solo", last_name: "User", email: "solo@example.com"},
+          actor: actor
+        )
+
+      {:ok, _group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "SomeOtherGroup"})
+        |> Ash.create(actor: actor)
+
+      # Member is not in any group; search for the group name should not return this member
+      results =
+        Member
+        |> Member.fuzzy_search(%{query: "SomeOtherGroup"})
+        |> Ash.read!(actor: actor)
+
+      refute Enum.any?(results, fn r -> r.id == member.id end)
+    end
+  end
+
+  describe "search vector update on member_groups changes" do
+    test "adding member to group updates search vector (INSERT on member_groups)", %{
+      system_actor: actor
+    } do
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "New", last_name: "Member", email: "new@example.com"},
+          actor: actor
+        )
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "NewlyAddedGroup"})
+        |> Ash.create(actor: actor)
+
+      # Before adding to group, search should not find by group name
+      results_before =
+        Member
+        |> Member.fuzzy_search(%{query: "NewlyAddedGroup"})
+        |> Ash.read!(actor: actor)
+
+      refute Enum.any?(results_before, fn r -> r.id == member.id end)
+
+      {:ok, _mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: actor)
+
+      # After adding, search should find member (trigger on member_groups INSERT)
+      results_after =
+        Member
+        |> Member.fuzzy_search(%{query: "NewlyAddedGroup"})
+        |> Ash.read!(actor: actor)
+
+      assert Enum.any?(results_after, fn r -> r.id == member.id end)
+    end
+
+    test "removing member from group updates search vector (DELETE on member_groups)", %{
+      system_actor: actor
+    } do
+      # Use a member name that does not overlap with the group name so that the only
+      # way to find them is via search_vector (group name). Otherwise trigram fuzzy
+      # match on first_name would still find "Remove" when searching "RemovedGroup".
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Zara", last_name: "None", email: "zara.remove@example.com"},
+          actor: actor
+        )
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "RemovedGroup"})
+        |> Ash.create(actor: actor)
+
+      {:ok, mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: actor)
+
+      results_before =
+        Member
+        |> Member.fuzzy_search(%{query: "RemovedGroup"})
+        |> Ash.read!(actor: actor)
+
+      assert Enum.any?(results_before, fn r -> r.id == member.id end)
+
+      :ok = Mv.Membership.destroy_member_group(mg, actor: actor)
+
+      results_after =
+        Member
+        |> Member.fuzzy_search(%{query: "RemovedGroup"})
+        |> Ash.read!(actor: actor)
+
+      refute Enum.any?(results_after, fn r -> r.id == member.id end)
+    end
+  end
+
+  describe "edge cases" do
+    test "token match: single word in group name matches (e.g. Board in Board Members)", %{
+      system_actor: actor
+    } do
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Partial", last_name: "Test", email: "partial@example.com"},
+          actor: actor
+        )
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Board Members"})
+        |> Ash.create(actor: actor)
+
+      {:ok, _mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: actor)
+
+      # FTS with 'simple' config: full word "Board" or "Members" should match
+      results =
+        Member
+        |> Member.fuzzy_search(%{query: "Board"})
+        |> Ash.read!(actor: actor)
+
+      assert Enum.any?(results, fn r -> r.id == member.id end),
+             "Search for 'Board' should find member in group 'Board Members'"
+    end
+
+    test "search with token from group name containing special characters does not crash", %{
+      system_actor: actor
+    } do
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Special", last_name: "Char", email: "special@example.com"},
+          actor: actor
+        )
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Team A&B"})
+        |> Ash.create(actor: actor)
+
+      {:ok, _mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: actor)
+
+      # Search for a token from the group name; proves tokenization does not crash on "A&B"
+      results =
+        Member
+        |> Member.fuzzy_search(%{query: "Team"})
+        |> Ash.read!(actor: actor)
+
+      assert Enum.any?(results, fn r -> r.id == member.id end),
+             "Search for 'Team' should find member in group 'Team A&B'"
+    end
+  end
+
+  describe "authorization" do
+    test "search respects authorization (actor sees only allowed members)", %{
+      system_actor: system_actor
+    } do
+      # own_data user linked to member1 can only read member1; member2 is in same group
+      admin = Mv.Fixtures.user_with_role_fixture("admin")
+      user_own_data = Mv.Fixtures.user_with_role_fixture("own_data")
+
+      member1 =
+        Mv.Fixtures.member_fixture(%{
+          first_name: "Linked",
+          last_name: "User",
+          email: "linked@example.com"
+        })
+
+      member2 =
+        Mv.Fixtures.member_fixture(%{
+          first_name: "Other",
+          last_name: "User",
+          email: "other@example.com"
+        })
+
+      {:ok, user_own_data} =
+        user_own_data
+        |> Ash.Changeset.for_update(:update, %{})
+        |> Ash.Changeset.force_change_attribute(:member_id, member1.id)
+        |> Ash.update(actor: admin)
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "SharedGroupName"})
+        |> Ash.create(actor: system_actor)
+
+      for member <- [member1, member2] do
+        {:ok, _} =
+          MemberGroup
+          |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+          |> Ash.create(actor: admin)
+      end
+
+      # Search as own_data user: should only return member1 (linked), not member2
+      results =
+        Member
+        |> Member.fuzzy_search(%{query: "SharedGroupName"})
+        |> Ash.read!(actor: user_own_data)
+
+      ids = Enum.map(results, & &1.id)
+      assert member1.id in ids
+      refute member2.id in ids
+    end
+  end
+end
diff --git a/test/mv_web/components/sort_header_component_test.exs b/test/mv_web/components/sort_header_component_test.exs
index 6d23ab4..bdde4ae 100644
--- a/test/mv_web/components/sort_header_component_test.exs
+++ b/test/mv_web/components/sort_header_component_test.exs
@@ -223,7 +223,7 @@ defmodule MvWeb.Components.SortHeaderComponentTest do
   end
 
   describe "component behavior" do
-    test "clicking sends sort message to parent", %{conn: conn} do
+    test "clicking triggers sort event on parent LiveView", %{conn: conn} do
       conn = conn_with_oidc_user(conn)
       {:ok, view, _html} = live(conn, "/members")
 
@@ -232,7 +232,7 @@ defmodule MvWeb.Components.SortHeaderComponentTest do
       |> element("button[phx-value-field='first_name']")
       |> render_click()
 
-      # The component should send a message to the parent LiveView
+      # The component triggers a "sort" event on the parent LiveView
       # This is tested indirectly through the URL change in integration tests
     end
 
diff --git a/test/mv_web/member_live/index_groups_integration_test.exs b/test/mv_web/member_live/index_groups_integration_test.exs
index 3075d54..86738da 100644
--- a/test/mv_web/member_live/index_groups_integration_test.exs
+++ b/test/mv_web/member_live/index_groups_integration_test.exs
@@ -8,16 +8,19 @@ defmodule MvWeb.MemberLive.IndexGroupsIntegrationTest do
   - Groups sorting works with other sortings
   - Groups work with Membership Fee Status filter
   - Groups work with existing search (but not testing search integration itself)
+  - Member index search by group name returns members in that group (Issue #375)
   """
   # async: false to prevent PostgreSQL deadlocks when creating members and groups
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
   require Ash.Query
 
-  alias Mv.Membership.{Group, MemberGroup, CustomField, CustomFieldValue}
+  alias Mv.Helpers.SystemActor
+  alias Mv.Membership.{CustomField, CustomFieldValue, Group, MemberGroup}
+  alias Mv.MembershipFees.{MembershipFeeCycle, MembershipFeeType}
 
   setup do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
+    system_actor = SystemActor.get_system_actor()
 
     # Create test members
     {:ok, member1} =
@@ -80,15 +83,10 @@ defmodule MvWeb.MemberLive.IndexGroupsIntegrationTest do
     conn = conn_with_oidc_user(conn)
     {:ok, _view, html} = live(conn, "/members")
 
-    # Verify groups column is visible by default
+    # Verify groups column is visible by default (header and content)
     assert html =~ group1.name
     assert html =~ member1.first_name
-
-    # Hide groups column via field visibility dropdown
-    # (This tests integration with field visibility feature)
-    # Note: Actual implementation depends on how field visibility works
-    # For now, we verify the column exists and can be toggled
-    assert html
+    assert html =~ "Groups"
   end
 
   test "groups filter works with custom field filters", %{
@@ -140,11 +138,11 @@ defmodule MvWeb.MemberLive.IndexGroupsIntegrationTest do
     member1: member1,
     group1: group1
   } do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
+    system_actor = SystemActor.get_system_actor()
 
     # Create a membership fee type and cycle for member1
     {:ok, fee_type} =
-      Mv.MembershipFees.MembershipFeeType
+      MembershipFeeType
       |> Ash.Changeset.for_create(:create, %{
         name: "Test Fee",
         amount: Decimal.new("50.00"),
@@ -159,7 +157,7 @@ defmodule MvWeb.MemberLive.IndexGroupsIntegrationTest do
       )
 
     {:ok, _cycle} =
-      Mv.MembershipFees.MembershipFeeCycle
+      MembershipFeeCycle
       |> Ash.Changeset.for_create(:create, %{
         member_id: member1.id,
         membership_fee_type_id: fee_type.id,
@@ -212,6 +210,25 @@ defmodule MvWeb.MemberLive.IndexGroupsIntegrationTest do
     # (that's part of Issue #5 - Search Integration)
   end
 
+  test "member index search by group name returns members in that group", %{
+    conn: conn,
+    member1: member1,
+    member2: member2,
+    group1: group1
+  } do
+    # member1 is in group1 "Board Members", member2 is not
+    conn = conn_with_oidc_user(conn)
+    {:ok, view, _html} = live(conn, "/members")
+
+    view
+    |> element("form[phx-submit='search']")
+    |> render_submit(%{"query" => group1.name})
+
+    html = render(view)
+    assert html =~ member1.first_name
+    refute html =~ member2.first_name
+  end
+
   test "all filters and sortings work together", %{
     conn: conn,
     member1: member1,
diff --git a/test/mv_web/member_live/index_test.exs b/test/mv_web/member_live/index_test.exs
index 4f36795..53a2815 100644
--- a/test/mv_web/member_live/index_test.exs
+++ b/test/mv_web/member_live/index_test.exs
@@ -1,5 +1,5 @@
 defmodule MvWeb.MemberLive.IndexTest do
-  use MvWeb.ConnCase, async: true
+  use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
   require Ash.Query