A filter naming no group can be ticked to create it on save;
left unticked, "boo" on the way to Booles is a group nobody made.
The groups row shows before any group, so the first one starts here too;
a taken sync: name refuses the save, and none of it goes through.

Assisted-by: Claude Opus 5 via Claude Code
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

diff --git a/lib/pro_tacts/admin/contacts_show.rb b/lib/pro_tacts/admin/contacts_show.rb
index 2167e6e..773ddb1 100644
--- a/lib/pro_tacts/admin/contacts_show.rb
+++ b/lib/pro_tacts/admin/contacts_show.rb
@@ -35,17 +35,18 @@ module ProTacts
       # one: a card with no entries is a card whose history was lost,
       # and an empty default would render that as an ordinary quiet
       # record. Every group is the groups dialog's (GroupDialog).
-      #: (Contact contact, Array[Store::Group] groups, Array[Store::Group] all_groups, Array[Store::Change] changes) -> void
-      def initialize(contact:, groups:, all_groups:, changes:)
+      #: (Contact contact, Array[Store::Group] groups, Array[Store::Group] all_groups, Array[Store::Change] changes, ?notice: String?) -> void
+      def initialize(contact:, groups:, all_groups:, changes:, notice: nil)
         @contact = contact
         @groups = groups
         @all_groups = all_groups
         @changes = changes
+        @notice = notice
         @birthday = Format.birthday(contact)
       end
 
       def view_template
-        render Layout.new(title: @contact.name || @contact.id) do
+        render Layout.new(title: @contact.name || @contact.id, notice: @notice) do
           # The back-link line and the record card are one block, the
           # line its caption row: spaced like the dashboard's
           # section-head over its card (see .record in admin.css), not
@@ -75,11 +76,8 @@ module ProTacts
                   # the avatar is the row's visual anchor, not a caption.
                   render Avatar.new(contact: @contact, size: "xl") if @contact.photo
                 end
-                # Only rendered when there's something to show: an empty
-                # <dl> would still take up the gap card-body puts between
-                # its children, leaving the header off-center in a card
-                # with nothing else in it.
-                dl(class: "detail-grid") { rows } if has_data?
+                # Never empty: the groups row is always there.
+                dl(class: "detail-grid") { rows }
               end
             end
           end
@@ -115,18 +113,12 @@ module ProTacts
             end
           end
           # No row, so outside the record's grid.
-          render GroupDialog.new(contact: @contact, groups: @all_groups) if @all_groups.any?
+          render GroupDialog.new(contact: @contact, groups: @all_groups)
         end
       end
 
       private
 
-      #: () -> bool
-      def has_data?
-        @contact.phones.any? || @contact.emails.any? || @contact.addresses.any? ||
-          !@birthday.nil? || @contact.notes.any? || @all_groups.any?
-      end
-
       # A missing TYPE parameter still gets a key: the fallback names
       # the kind of value, so no row renders unlabeled in the grid.
       # Every row that reads from a line hands it over, because which
@@ -135,7 +127,7 @@ module ProTacts
       # and a group holds only addresses and notes anyway (see
       # db/migrations/004_groups.rb).
       def rows
-        groups_row if @all_groups.any?
+        groups_row
         @contact.phones.each do |phone|
           row(Format.type_label(phone.types, "phone"), phone.value, phone.line)
         end
@@ -156,10 +148,10 @@ module ProTacts
       # values are the group's rather than the contact's. Every tag opens
       # the group it names (docs/DESIGN.md, "Relationships are
       # navigable"), the other half of the member tags on a group's own
-      # card (Admin::GroupsShow). Rendered for a contact in no group too
-      # while any group exists, because the row holds the way to join
-      # one — the group card's members row, for the same reason, with
-      # its "edit members" in the same place.
+      # card (Admin::GroupsShow). Rendered for a contact in no group too,
+      # even before any group exists, because the row holds the way to
+      # join or start one — the group card's members row, for the same
+      # reason, with its "edit members" in the same place.
       #: () -> void
       def groups_row
         dt(class: "type-label") { "groups" }
diff --git a/lib/pro_tacts/admin/group_dialog.rb b/lib/pro_tacts/admin/group_dialog.rb
index afbc746..97e8869 100644
--- a/lib/pro_tacts/admin/group_dialog.rb
+++ b/lib/pro_tacts/admin/group_dialog.rb
@@ -10,18 +10,26 @@ module ProTacts
     # loaded with beside what it sends back (`was[]`), so the route can
     # move only what was toggled (Web#apply_groups).
     #
-    # Alpine only filters, matching each row's lowercased label in
+    # Alpine filters, matching each row's lowercased label in
     # data-label so no group's name is spliced into script; a row it
     # hides still submits its box. The filter sits outside the form,
     # because Enter in a form's text box would save mid-filter.
+    #
+    # A filter naming no group exactly also offers itself as a new
+    # group (`new`), created and joined by the save. Unchecked until
+    # ticked: a filter is usually half a name typed to find a group,
+    # and a save must not create "boo" on the way to Booles.
     class GroupDialog < Phlex::HTML
       ID = "edit-groups" #: String
       FORM = "edit-groups-form" #: String
 
       STATE = "{ filter: '', " \
+              "get labels() { return [...this.$refs.options.querySelectorAll('[data-label]')]" \
+              ".map(row => row.dataset.label) }, " \
               "shows(label) { return label.includes(this.filter.trim().toLowerCase()) }, " \
-              "get none() { return ![...this.$refs.options.querySelectorAll('[data-label]')]" \
-              ".some(row => this.shows(row.dataset.label)) } }" #: String
+              "get none() { return !this.labels.some(label => this.shows(label)) }, " \
+              "get creatable() { const name = this.filter.trim().toLowerCase(); " \
+              "return name !== '' && !this.labels.includes(name) } }" #: String
 
       # Alphabetical rather than the id order a tag keeps: this is a list
       # to find a name in, and nothing here stays put across a rename.
@@ -35,7 +43,7 @@ module ProTacts
         dialog(id: ID, popover: "auto", x_data: STATE) do
           header { "Groups" }
           div(class: "field-stack") do
-            input(type: "search", placeholder: "Filter groups", aria_label: "Filter groups",
+            input(type: "search", placeholder: "Filter or add groups", aria_label: "Filter or add groups",
                   autofocus: true, x_model: "filter")
             form(id: FORM, action: "/contacts/#{@contact.id}/groups", method: "post",
                  class: "field-stack", x_ref: "options") do
@@ -47,8 +55,16 @@ module ProTacts
                 end
                 input(type: "hidden", name: "was[]", value: group.id) if joined
               end
+              template(x_if: "creatable") do
+                label do
+                  input(type: "checkbox", name: "new", ":value": "filter.trim()")
+                  span(class: "gl-muted", style: "font-style: italic;", x_text: "filter.trim()")
+                end
+              end
+            end
+            template(x_if: "none && !creatable") do
+              p(class: "gl-muted") { @groups.empty? ? "No groups yet." : "No groups match." }
             end
-            template(x_if: "none") { p(class: "gl-muted") { "No groups match." } }
           end
           footer do
             button(type: "button", popovertarget: ID, popovertargetaction: "hide") { "Cancel" }
diff --git a/lib/pro_tacts/store.rb b/lib/pro_tacts/store.rb
index 91df6eb..6591eee 100644
--- a/lib/pro_tacts/store.rb
+++ b/lib/pro_tacts/store.rb
@@ -671,10 +671,13 @@ module ProTacts
     end
 
     # A card's side of #edit_group: one transaction, leavers first and
-    # joiners last for that method's reason.
-    #: (String card_id, join: Array[String], leave: Array[String]) -> void
-    def regroup(card_id, join:, leave:)
+    # joiners last for that method's reason. A name creates a group to
+    # join inside the same transaction, so a taken `sync:` name
+    # (#create_group) moves nothing.
+    #: (String card_id, join: Array[String], leave: Array[String], ?create: String?) -> void
+    def regroup(card_id, join:, leave:, create: nil)
       @database.transaction do
+        join += [create_group(name: create)] if create
         leave.each { remove_member(it, card_id) }
         join.each { add_member(it, card_id) }
       end
diff --git a/lib/pro_tacts/web/contacts.rb b/lib/pro_tacts/web/contacts.rb
index 918e8b4..f3913a6 100644
--- a/lib/pro_tacts/web/contacts.rb
+++ b/lib/pro_tacts/web/contacts.rb
@@ -179,15 +179,25 @@ module ProTacts
     # or left elsewhere since stays as it is, and a stale page has
     # nothing to revert and no snapshot to refuse. Only ids naming a
     # group: Store#add_member reads the group with `sole`, so a doctored
-    # one would be a 500 rather than the bad input it is.
+    # one would be a 500 rather than the bad input it is. A `new` name
+    # is a group the filter box offered to create, joined in the same
+    # save; a blank one is none.
     #: (untyped r, String id) -> String?
     def apply_groups(r, id)
-      return if store.contact(id).nil?
+      contact = store.contact(id)
+      return if contact.nil?
 
       known = store.all_groups.map(&:id)
       checked = ids_in(r.params["groups"]) & known
       was = ids_in(r.params["was"]) & known
-      store.regroup(id, join: checked - was, leave: was - checked)
+      name = r.params["new"].to_s.strip
+      begin
+        store.regroup(id, join: checked - was, leave: was - checked, create: (name unless name.empty?))
+      rescue Sequel::UniqueConstraintViolation
+        # A taken `sync:` name (db/migrations/007_sync_names.rb), refused
+        # with the rest of the save in regroup's transaction.
+        return contact_screen(contact, notice: "Another group is already named #{name}; nothing was saved.")
+      end
       r.redirect "/contacts/#{id}", 303
     end
 
@@ -197,14 +207,15 @@ module ProTacts
       param.is_a?(Array) ? param.map(&:to_s) : []
     end
 
-    #: (Contact contact) -> String
-    def contact_screen(contact)
+    #: (Contact contact, ?notice: String) -> String
+    def contact_screen(contact, notice: nil)
       response["Content-Type"] = "text/html; charset=utf-8"
       Admin::ContactsShow.call(
         contact:,
         groups: store.groups_of(contact.id),
         all_groups: store.all_groups,
         changes: store.changes_of(contact.id),
+        notice:,
       )
     end
 
diff --git a/sig/pro_tacts/admin.rbs b/sig/pro_tacts/admin.rbs
index 8c283f5..32a62b7 100644
--- a/sig/pro_tacts/admin.rbs
+++ b/sig/pro_tacts/admin.rbs
@@ -7,7 +7,7 @@
 module ProTacts
   module Admin
     class ContactsShow
-      def self.call: (contact: Contact, groups: Array[Store::Group], all_groups: Array[Store::Group], changes: Array[Store::Change]) -> String
+      def self.call: (contact: Contact, groups: Array[Store::Group], all_groups: Array[Store::Group], changes: Array[Store::Change], ?notice: String?) -> String
     end
 
     class ContactsEdit
diff --git a/test/pro_tacts/admin/test_contacts_pages.rb b/test/pro_tacts/admin/test_contacts_pages.rb
index c56eaa7..81d4f71 100644
--- a/test/pro_tacts/admin/test_contacts_pages.rb
+++ b/test/pro_tacts/admin/test_contacts_pages.rb
@@ -319,17 +319,6 @@ class AdminContactsPagesTest < Minitest::Test
     end
   end
 
-  # No membership and nothing to join, no row: an empty tag set would
-  # say a contact belongs to nothing in the space where belonging is
-  # shown.
-  def test_show_omits_the_groups_row_with_no_group_to_show_or_join
-    with_contacts({"ada" => ADA}) do
-      get "/contacts/ada"
-
-      refute_includes last_response.body, "groups</dt>"
-    end
-  end
-
   # A group with no name marks its rows with its id, which is what the
   # mark is for: an empty tag would say a row came from somewhere and
   # then not say where.
@@ -354,16 +343,24 @@ class AdminContactsPagesTest < Minitest::Test
     end
   end
 
-  # The row holds the way to join a group, so a contact in none still
-  # gets it while any group exists.
-  def test_show_offers_a_contact_in_no_group_its_groups_to_edit
-    with_contacts({"ada" => ADA}) do |store|
-      FixtureData.seed_group(store, name: "Booles")
-
+  # The row holds the way to join a group or start one, so it renders
+  # before any group exists.
+  def test_show_offers_the_groups_dialog_before_any_group_exists
+    with_contacts({"ada" => ADA}) do
       get "/contacts/ada"
 
       assert_includes last_response.body, %(<dt class="type-label">groups</dt>)
       assert_includes last_response.body, %(popovertarget="edit-groups")
+      assert_includes last_response.body, %(<dialog id="edit-groups")
+    end
+  end
+
+  def test_the_groups_dialog_offers_the_filter_as_an_unchecked_new_group
+    with_contacts({"ada" => ADA}) do
+      get "/contacts/ada"
+      dialog = last_response.body[%r{<dialog id="edit-groups".*?</dialog>}].to_s
+
+      assert_includes dialog, %(<input type="checkbox" name="new" :value="filter.trim()">)
     end
   end
 
@@ -428,6 +425,42 @@ class AdminContactsPagesTest < Minitest::Test
     end
   end
 
+  def test_a_new_group_is_created_and_joined_with_the_rest_of_the_save
+    with_contacts({"ada" => ADA}) do |store|
+      booles = FixtureData.seed_group(store, name: "Booles")
+
+      post "/contacts/ada/groups", groups: [booles], new: " Clarks "
+
+      assert_equal 303, last_response.status
+      assert_equal ["Booles", "Clarks"], store.groups_of("ada").map(&:label).sort
+    end
+  end
+
+  def test_a_blank_new_group_creates_nothing
+    with_contacts({"ada" => ADA}) do |store|
+      post "/contacts/ada/groups", new: "  "
+
+      assert_equal 303, last_response.status
+      assert_empty store.all_groups
+    end
+  end
+
+  # A `sync:` name is the one kind that must be unique
+  # (db/migrations/007_sync_names.rb), and the refusal is the whole save.
+  def test_a_new_group_with_a_taken_sync_name_saves_nothing
+    with_contacts({"ada" => ADA}) do |store|
+      booles = FixtureData.seed_group(store, name: "Booles")
+      FixtureData.seed_group(store, name: "sync:alpha")
+
+      post "/contacts/ada/groups", groups: [booles], new: "sync:alpha"
+
+      assert_equal 200, last_response.status
+      assert_includes last_response.body, "Another group is already named sync:alpha; nothing was saved."
+      assert_empty store.groups_of("ada")
+      assert_equal 2, store.all_groups.length
+    end
+  end
+
   def test_a_save_for_an_unknown_contact_is_a_404
     with_contacts({"ada" => ADA}) do |store|
       id = FixtureData.seed_group(store, name: "Booles")
@@ -635,16 +668,17 @@ class AdminContactsPagesTest < Minitest::Test
 
   # A card that will not parse is served from its bytes regardless —
   # the raw section is the one thing such a card has to show, so it
-  # renders with no grid under the header, not instead of the page.
-  # The record card, specifically: the change log rides the same grid
-  # in a card of its own, and every card has a history.
-  def test_show_of_a_bare_contact_renders_no_grid
+  # renders with only the groups row under the header, not instead of
+  # the page. The record card, specifically: the change log rides the
+  # same grid in a card of its own, and every card has a history.
+  def test_show_of_a_bare_contact_renders_only_the_groups_row
     bare = "BEGIN:VCARD\r\nVERSION:3.0\r\nFN:Bare Contact\r\nUID:bare\r\nEND:VCARD\r\n"
 
     with_contacts({"bare" => bare}) do
       get "/contacts/bare"
+      grid = last_response.body[%r{<dl class="detail-grid">.*?</dl>}].to_s
 
-      refute_includes last_response.body, '<dl class="detail-grid">'
+      assert_equal ["groups"], grid.scan(%r{<dt class="type-label">([^<]*)</dt>}).flatten
       assert_includes last_response.body, "<details"
     end
   end
diff --git a/test/pro_tacts/test_store.rb b/test/pro_tacts/test_store.rb
index c58e9a7..ea4f719 100644
--- a/test/pro_tacts/test_store.rb
+++ b/test/pro_tacts/test_store.rb
@@ -1325,6 +1325,14 @@ class StoreTest < Minitest::Test
     end
   end
 
+  def test_a_regroup_creates_the_group_it_names_and_joins_it
+    with_store({"aiden" => AIDEN}) do |store|
+      store.regroup("aiden", join: [], leave: [], create: "Clarks")
+
+      assert_equal ["Clarks"], store.groups_of("aiden").map(&:label)
+    end
+  end
+
   # Nothing a client downloads moved, so nothing is logged: a group
   # that lends nothing composes nothing into a new member, and a name
   # is on no card.