diff --git a/Gemfile.lock b/Gemfile.lock
index 9d3e689b..b748e755 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -123,7 +123,7 @@ GEM
     benchmark (0.5.0)
     bigdecimal (3.3.1)
     bindex (0.8.1)
-    bootsnap (1.25.0)
+    bootsnap (1.26.0)
       msgpack (~> 1.5)
     builder (3.3.0)
     bullet (8.2.0)
@@ -419,7 +419,7 @@ GEM
       base64 (>= 0.1.0)
       logger (>= 1.6.0)
       rack (>= 3.0.0, < 4)
-    rack-proxy (1.0.2)
+    rack-proxy (2.0.0)
       rack (>= 2.0, < 4)
     rack-session (2.1.2)
       base64 (>= 0.1.0)
@@ -758,7 +758,7 @@ CHECKSUMS
   benchmark (0.5.0) sha256=465df122341aedcb81a2a24b4d3bd19b6c67c1530713fd533f3ff034e419236c
   bigdecimal (3.3.1) sha256=eaa01e228be54c4f9f53bf3cc34fe3d5e845c31963e7fcc5bedb05a4e7d52218
   bindex (0.8.1) sha256=7b1ecc9dc539ed8bccfc8cb4d2732046227b09d6f37582ff12e50a5047ceb17e
-  bootsnap (1.25.0) sha256=41059e7d0f9cb4023a33465d095f64b913fc9d1b808d6524c307da945fbcffcf
+  bootsnap (1.26.0) sha256=ca96237015e6cd74a02963d5821cf00ac5ea134653b323e8cd6d702a7718bf1b
   builder (3.3.0) sha256=497918d2f9dca528fdca4b88d84e4ef4387256d984b8154e9d5d3fe5a9c8835f
   bullet (8.2.0) sha256=921ed8cde81c939e4eda041345f44f0d0d72c6fbb63aec07d11e5bf653bbe473
   bundler (4.0.17) sha256=214e21431b5665dd2f99df8a5511c6b151d7a72e8015c8b38f8b775b61cbb6c1
@@ -890,7 +890,7 @@ CHECKSUMS
   racc (1.8.1) sha256=4a7f6929691dbec8b5209a0b373bc2614882b55fc5d2e447a21aaa691303d62f
   rack (3.2.7) sha256=93e13e1c24f93556671d85d2d79fa228c3485815c50d7e2f265b5330c6528fb7
   rack-protection (4.2.1) sha256=cf6e2842df8c55f5e4d1a4be015e603e19e9bc3a7178bae58949ccbb58558bac
-  rack-proxy (1.0.2) sha256=9f57da746be62ec3fed46646dbae2d50f7f4ddc39307d693affff9ffd431865b
+  rack-proxy (2.0.0) sha256=4f1d435d82afe93bc916d1226df8be307c1b808551f0ecdb56e0b668fd5756e6
   rack-session (2.1.2) sha256=595434f8c0c3473ae7d7ac56ecda6cc6dfd9d37c0b2b5255330aa1576967ffe8
   rack-test (2.2.0) sha256=005a36692c306ac0b4a9350355ee080fd09ddef1148a5f8b2ac636c720f5c463
   rackup (2.3.1) sha256=6c79c26753778e90983761d677a48937ee3192b3ffef6bc963c0950f94688868
diff --git a/app/controllers/home_controller.rb b/app/controllers/home_controller.rb
index 7ca30623..20875bbd 100644
--- a/app/controllers/home_controller.rb
+++ b/app/controllers/home_controller.rb
@@ -138,6 +138,7 @@ def endpoints
           activateProjectUrl: activate_project_path,
           diversityCheckUrl: check_diversity_score_path,
           groupsUrl: groups_path( id: '' ),
+          suggestGroupsUrl: suggest_groups_path( id: '' ),
           diversityRescoreGroup: rescore_group_path( id: '' ),
           diversityRescoreGroups: rescore_groups_path( id: '' )
         }
diff --git a/app/controllers/projects_controller.rb b/app/controllers/projects_controller.rb
index 1f893041..40d76fc7 100644
--- a/app/controllers/projects_controller.rb
+++ b/app/controllers/projects_controller.rb
@@ -5,7 +5,7 @@ class ProjectsController < ApplicationController
   include LtiGradable
 
   before_action :set_project, only: %i[show edit update destroy activate
-                                       rescore_group rescore_groups]
+                                       rescore_group rescore_groups suggest_groups]
   before_action :check_editor, except: %i[rescore_group rescore_groups
                                           show index get_groups
                                           set_groups]
@@ -139,24 +139,31 @@ def set_groups
     group_hash = {}
     params[:groups].each_value do | g |
       group = nil
-      if g[:id].positive?
-        group = project.groups.find_by id: g[:id]
+      group_id = g[:id].to_i
+      if group_id.positive?
+        group = project.groups.find_by id: group_id
         group.name = g[:name]
       else
         group = project.groups.build( name: g[:name] )
       end
       group.users = []
-      group_hash[g[:id]] = group
+      group_hash[group_id] = group
     end
     params[:students].each_value do | s |
       student = project.rosters.find_by( user_id: s[:id] ).user
-      group = group_hash[s[:group_id]]
+      group = group_hash[s[:group_id].to_i]
       group.users << student unless group.nil?
     end
 
     begin
       ActiveRecord::Base.transaction do
-        group_hash.each_value( &:save! )
+        group_hash.each_value do | group |
+          group.calc_diversity_score
+          group.save!
+        end
+        current_group_ids = group_hash.values.map( &:id ).compact
+        groups_to_remove = Group.where( project: ).where.not( id: current_group_ids )
+        groups_to_remove.destroy_all
       end
     rescue StandardError
       # Post back a JSON error
@@ -176,29 +183,43 @@ def get_groups
     get_groups_helper project:
   end
 
-  def get_groups_helper( project:, message: nil )
-    students = {}
-    project.rosters.enrolled.each do | roster |
-      student = roster.user
-      students[ student.id ] = {
-        id: student.id,
-        first_name: student.first_name,
-        last_name: student.last_name,
-        email: student.email
-      }
-    end
+  # Builds a recommendation preview for the Groups tab without persisting it.
+  #
+  # This controller action is the bridge between the course roster and
+  # Group.suggest_optimal_groups. It returns the suggested groups, preview-only
+  # student assignments, and aggregate metrics that the React UI shows before
+  # the instructor accepts or rejects the proposal.
+  def suggest_groups
+    students = @project.rosters.enrolled.includes(
+      user: [
+        :emails, :gender, :primary_language, :cip_code,
+        { home_state: :home_country }, { reactions: :narrative }
+      ]
+    ).map( &:user )
+    suggestion = Group.suggest_optimal_groups(
+      users: students,
+      target_group_size: params[:target_group_size],
+      target_group_count: params[:target_group_count]
+    )
+    students_payload = build_students_payload @project
+    suggested_students_payload = students_payload.deep_dup
+    groups_payload = build_suggested_groups_payload( suggestion, suggested_students_payload )
 
-    groups = {}
-    project.groups.each do | group |
-      groups[group.id] = {
-        id: group.id,
-        name: group.name,
-        diversity: group.diversity_score
+    render json: {
+      groups: groups_payload,
+      students: suggested_students_payload,
+      summary: {
+        diversity_score_standard_deviation: suggestion[:diversity_score_standard_deviation],
+        average_diversity_score: suggestion[:average_diversity_score],
+        average_faultline_strength: suggestion[:average_faultline_strength],
+        max_faultline_strength: suggestion[:max_faultline_strength]
       }
-      group.users.each do | user |
-        students[user.id][ :group_id ] = group.id
-      end
-    end
+    }
+  end
+
+  def get_groups_helper( project:, message: nil )
+    students = build_students_payload project
+    groups = build_groups_payload( project, students )
 
     respond_to do | format |
       format.json do
@@ -212,7 +233,7 @@ def get_groups_helper( project:, message: nil )
   end
 
   def remove_group
-    group = Group.find( params[:group_id] )
+    group = Group.find_by( id: params[:group_id] )
     group&.delete
     redirect_to @project
   end
@@ -267,6 +288,63 @@ def activate
 
   private
 
+  # Serializes enrolled roster members for the groups-management JSON payloads.
+  def build_students_payload( project )
+    students = {}
+    project.rosters.enrolled.each do | roster |
+      student = roster.user
+      students[ student.id ] = {
+        id: student.id,
+        first_name: student.first_name,
+        last_name: student.last_name,
+        email: student.email
+      }
+    end
+    students
+  end
+
+  # Serializes persisted project groups and annotates the passed-in students hash
+  # with each member's saved group assignment.
+  def build_groups_payload( project, students )
+    groups = {}
+    project.groups.each do | group |
+      groups[group.id] = {
+        id: group.id,
+        name: group.name,
+        diversity: group.diversity_score,
+        faultline: group.calc_faultline_strength,
+        member_count: group.users.count
+      }
+      group.users.each do | user |
+        students[user.id][ :group_id ] = group.id
+      end
+    end
+    groups
+  end
+
+  # Serializes a recommendation preview and annotates the passed-in students hash
+  # with preview-only suggested group assignments.
+  #
+  # The returned structure mirrors build_groups_payload so the UI can preview a
+  # recommendation and later submit it through the existing set_groups action.
+  def build_suggested_groups_payload( suggestion, students )
+    groups = {}
+    suggestion.fetch( :groups, [] ).each_with_index do | suggested_group, index |
+      group_id = -( index + 1 )
+      groups[group_id] = {
+        id: group_id,
+        name: suggested_group[:name],
+        diversity: suggested_group[:diversity_score],
+        faultline: suggested_group[:faultline_strength],
+        member_count: suggested_group[:users].count
+      }
+      suggested_group[:users].each do | user |
+        students[user.id][ :group_id ] = group_id
+      end
+    end
+    groups
+  end
+
   # Use callbacks to share common setup or constraints between actions.
   def set_project
     if params[:id].blank? || 'new' == params[:id]
diff --git a/app/javascript/components/projects/ProjectDataAdmin.tsx b/app/javascript/components/projects/ProjectDataAdmin.tsx
index 867e8989..496fca50 100644
--- a/app/javascript/components/projects/ProjectDataAdmin.tsx
+++ b/app/javascript/components/projects/ProjectDataAdmin.tsx
@@ -377,6 +377,7 @@ export default function ProjectDataAdmin(props: ProjectDataAdminProps) {
         <ProjectGroups
           projectId={projectId}
           groupsUrl={endpoints.groupsUrl}
+          suggestGroupsUrl={endpoints.suggestGroupsUrl}
           diversityCheckUrl={endpoints.diversityCheckUrl}
           diversityRescoreGroup={endpoints.diversityRescoreGroup}
           diversityRescoreGroups={endpoints.diversityRescoreGroups}
diff --git a/app/javascript/components/projects/ProjectGroups.tsx b/app/javascript/components/projects/ProjectGroups.tsx
index 171aca4d..442efc22 100644
--- a/app/javascript/components/projects/ProjectGroups.tsx
+++ b/app/javascript/components/projects/ProjectGroups.tsx
@@ -19,6 +19,7 @@ import { Column } from "primereact/column";
 type Props = {
   projectId: number;
   groupsUrl: string;
+  suggestGroupsUrl: string;
   diversityCheckUrl: string;
   diversityRescoreGroup: string;
   diversityRescoreGroups: string;
@@ -29,15 +30,41 @@ export default function ProjectGroups(props: Props) {
   const [working, setWorking] = useState(true);
   const [message, setMessage] = useState("");
   const [filterText, setFilterText] = useState("");
+  const [targetGroupCount, setTargetGroupCount] = useState("2");
   const [sortBy, setSortBy] = useState("last_name");
   const [sortDirection, setSortDirection] = useState(SortDirection.DESC);
   const [groupsRaw, setGroupsRaw] = useState({});
   const [studentsRaw, setStudentsRaw] = useState({});
   const [groups, setGroups] = useState([]);
   const [students, setStudents] = useState([]);
+  const [suggestedGroupsRaw, setSuggestedGroupsRaw] = useState(null);
+  const [suggestedStudentsRaw, setSuggestedStudentsRaw] = useState(null);
+  const [suggestedGroups, setSuggestedGroups] = useState([]);
+  const [suggestionSummary, setSuggestionSummary] = useState(null);
 
   const dispatch = useDispatch();
 
+  const sortStudents = (field, direction, studentList) => {
+    const directionMultiplier =
+      direction == SortDirection.ASC ? 1 : -1;
+    const sortedStudents = [...studentList];
+    sortedStudents.sort((studentOne, studentTwo) => {
+      const valueOne = studentOne[field] || "";
+      const valueTwo = studentTwo[field] || "";
+      if (valueOne < valueTwo) {
+        return -1 * directionMultiplier;
+      }
+      if (valueOne > valueTwo) {
+        return 1 * directionMultiplier;
+      }
+      return 0;
+    });
+    setSortBy(field);
+    setSortDirection(direction);
+    setStudents(sortedStudents);
+    return sortedStudents;
+  };
+
   const addGroup = () => {
     const updatedGroups = Object.assign({}, groupsRaw);
     const group_ids = Object.keys(updatedGroups).map(Number);
@@ -68,11 +95,11 @@ export default function ProjectGroups(props: Props) {
         studentsUpdated[item.id].group_id = null;
       }
     });
-    sortStudents(sortBy, sortDirection, students);
+    const sortedStudents = sortStudents(sortBy, sortDirection, students);
     setGroupsRaw(groupsUpdated);
     setGroups(Object.values(groupsUpdated));
     setStudentsRaw(studentsUpdated);
-    setStudents(students);
+    setStudents(sortedStudents);
   };
 
   const filter = event => {
@@ -82,8 +109,8 @@ export default function ProjectGroups(props: Props) {
         .toUpperCase()
         .includes(filter_text.toUpperCase())
     );
-    sortStudents(sortBy, sortDirection, filtered);
-    setStudents(filtered);
+    const sortedStudents = sortStudents(sortBy, sortDirection, filtered);
+    setStudents(sortedStudents);
     setFilterText(event.target.value);
   };
 
@@ -124,6 +151,10 @@ export default function ProjectGroups(props: Props) {
       .then(response => {
         const data = response.data;
         setWorking(false);
+        setSuggestedGroupsRaw(null);
+        setSuggestedStudentsRaw(null);
+        setSuggestedGroups([]);
+        setSuggestionSummary(null);
         setGroupsRaw(data.groups);
         setStudentsRaw(data.students);
         setGroups(Object.values(data.groups));
@@ -196,7 +227,7 @@ export default function ProjectGroups(props: Props) {
       });
   };
 
-  const saveGroups = () => {
+  const saveGroups = (nextGroups = groupsRaw, nextStudents = studentsRaw) => {
     setWorking(true);
     setMessage("Saving...");
 
@@ -204,13 +235,17 @@ export default function ProjectGroups(props: Props) {
     dispatch(startTask());
     axios
       .patch(url, {
-        groups: groupsRaw,
-        students: studentsRaw
+        groups: nextGroups,
+        students: nextStudents
       })
       .then(response => {
         const data = response.data;
         setWorking(false);
         setDirty(false);
+        setSuggestedGroupsRaw(null);
+        setSuggestedStudentsRaw(null);
+        setSuggestedGroups([]);
+        setSuggestionSummary(null);
         setGroupsRaw(data.groups);
         setStudentsRaw(data.students);
         setGroups(Object.values(data.groups));
@@ -229,6 +264,69 @@ export default function ProjectGroups(props: Props) {
       });
   };
 
+  const suggestGroups = () => {
+    if (working) {
+      return;
+    }
+
+    setWorking(true);
+    setMessage("Generating recommendations...");
+
+    const url = props.suggestGroupsUrl + props.projectId + ".json";
+    dispatch(startTask());
+    axios
+      .post(url, {
+        target_group_count: targetGroupCount
+      })
+      .then(response => {
+        const data = response.data;
+        setWorking(false);
+        setSuggestedGroupsRaw(data.groups);
+        setSuggestedStudentsRaw(data.students);
+        setSuggestedGroups(Object.values(data.groups));
+        setSuggestionSummary(data.summary);
+        setMessage("");
+      })
+      .catch(error => {
+        console.log("error", error);
+        setWorking(false);
+        setMessage("Unable to generate recommendations");
+      })
+      .finally(() => {
+        dispatch(endTask());
+      });
+  };
+
+  const rejectSuggestedGroups = () => {
+    if (working) {
+      return;
+    }
+
+    setSuggestedGroupsRaw(null);
+    setSuggestedStudentsRaw(null);
+    setSuggestedGroups([]);
+    setSuggestionSummary(null);
+    setMessage("");
+  };
+
+  const acceptSuggestedGroups = () => {
+    if (working || null == suggestedGroupsRaw || null == suggestedStudentsRaw) {
+      return;
+    }
+
+    saveGroups(suggestedGroupsRaw, suggestedStudentsRaw);
+  };
+
+  const suggestedMembers = groupId => {
+    if (null == suggestedStudentsRaw) {
+      return [];
+    }
+
+    return Object.values(suggestedStudentsRaw).filter(student => {
+      return student.group_id == groupId;
+    });
+  };
+
   const direction = {
     [SortDirection.ASC]: "asc",
     [SortDirection.DESC]: "desc"
@@ -236,6 +334,61 @@ export default function ProjectGroups(props: Props) {
 
   return (
     <Panel>
+      {0 < suggestedGroups.length ? (
+        <Panel header="Recommended Groups" className="mb-3">
+          {0 < groups.length ? (
+            <p id="recommended-groups-warning">
+              Accepting these suggested groups will remove and replace the existing project groups.
+            </p>
+          ) : null}
+          <dl id="recommended-groups-summary">
+            <dt>Diversity score std. dev.</dt>
+            <dd>{suggestionSummary?.diversity_score_standard_deviation ?? 0}</dd>
+            <dt>Average diversity score</dt>
+            <dd>{suggestionSummary?.average_diversity_score ?? 0}</dd>
+            <dt>Average faultline strength</dt>
+            <dd>{suggestionSummary?.average_faultline_strength ?? 0}</dd>
+            <dt>Max faultline strength</dt>
+            <dd>{suggestionSummary?.max_faultline_strength ?? 0}</dd>
+          </dl>
+          {suggestedGroups.map(group => {
+            return (
+              <Panel
+                key={`suggested-${group.id}`}
+                id={`recommended-group-${group.id}`}
+                header={group.name}
+                className="mb-2 recommended-group-card"
+              >
+                <div>Members: {group.member_count}</div>
+                <div>Diversity score: {group.diversity}</div>
+                <div>Faultline strength: {group.faultline}</div>
+                <ul>
+                  {suggestedMembers(group.id).map(student => {
+                    return (
+                      <li key={`suggested-member-${group.id}-${student.id}`}>
+                        {student.first_name} {student.last_name}
+                      </li>
+                    );
+                  })}
+                </ul>
+              </Panel>
+            );
+          })}
+          <div className="flex gap-2">
+            <Button onClick={acceptSuggestedGroups} icon="pi pi-check" disabled={working}>
+              Accept Suggested Groups
+            </Button>
+            <Button
+              onClick={rejectSuggestedGroups}
+              icon="pi pi-times"
+              severity="secondary"
+              disabled={working}
+            >
+              Reject Suggested Groups
+            </Button>
+          </div>
+        </Panel>
+      ) : null}
       <DataTable
         value={students}
         resizableColumns
@@ -263,11 +416,25 @@ export default function ProjectGroups(props: Props) {
                   {students.length + " of " + Object.values(studentsRaw).length}
                 </span>
                 {dirty ? (
-                  <Button onClick={saveGroups} icon="pi pi-save">
+                  <Button onClick={() => saveGroups()} icon="pi pi-save">
                     Save
                   </Button>
                 ) : null}
                 <span>{message}</span>
+                <span className="p-input-icon-left">
+                  <i className="pi pi-users" />
+                  <InputText
+                    id="target_group_count"
+                    aria-label="Target Group Count"
+                    placeholder="Target Group Count"
+                    onChange={event => setTargetGroupCount(event.target.value)}
+                    value={targetGroupCount}
+                    disabled={working}
+                  />
+                </span>
+                <Button onClick={suggestGroups} icon="pi pi-sparkles" disabled={working}>
+                  Recommend Groups
+                </Button>
                 <Button onClick={recalcDiversity} icon="pi pi-calculator">
                   Recalculate Diversity
                 </Button>
@@ -332,6 +499,7 @@ export default function ProjectGroups(props: Props) {
                       rescoreGroup={rescoreGroup}
                       students={studentsRaw}
                     />
+                    <div>Faultline: {groupsRaw[group.id].faultline || 0}</div>
                   </>
                 );
               }}
diff --git a/app/models/group.rb b/app/models/group.rb
index dff4ed6d..c746eb0d 100644
--- a/app/models/group.rb
+++ b/app/models/group.rb
@@ -67,11 +67,14 @@ def self.calc_diversity_score_for_group( users: )
       impairment_hash = Hash.new( 0 )
 
       users.uniq.each do | user |
-        if user.home_state.present?
-          state_hash[user.home_state] += 1 unless
-            true == user.home_state_no_response
-          country_hash[user.home_state.home_country] += 1 unless
-            true == user.home_state_home_country.no_response
+        state = user.home_state
+        state = nil if state&.no_response == true
+        country = state&.home_country
+        country = nil if country&.no_response == true
+
+        if state.present?
+          state_hash[state] += 1
+          country_hash[country] += 1 if country.present?
         end
         cip_hash[user.cip_code] += 1 unless
             user.cip_code.nil? || user.cip_code_gov_code.zero?
@@ -156,11 +159,275 @@ def self.calc_faultline_strength_for_group( users: )
     [asw_scores.max || 0.0, 0.0].max.round( 4 )
   end
 
+  # Builds a recommended partition of +users+ for the project-groups UI.
+  #
+  # This is the model-side entry point used by ProjectsController#suggest_groups.
+  # It converts a course roster into balanced candidate groups, evaluates those
+  # candidates with the existing diversity and faultline metrics, and returns
+  # the best-scoring proposal in a shape that can be previewed or later saved by
+  # the existing group-management flow.
+  def self.suggest_optimal_groups( users:, target_group_size: nil, target_group_count: nil )
+    unique_users = users.compact.uniq do | user |
+      user.respond_to?( :id ) && user.id.present? ? user.id : user.object_id
+    end
+    return { groups: [], group_sizes: [] } if unique_users.count < 2
+
+    group_sizes = suggested_group_sizes_for(
+      user_count: unique_users.count,
+      target_group_size:,
+      target_group_count:
+    )
+    return { groups: [], group_sizes: [] } if group_sizes.blank?
+
+    random = Random.new( unique_users.count * 100 + group_sizes.count )
+    groupings = suggestion_candidate_orders_for( users: unique_users, random: )
+                .map do | ordered_users |
+                  suggestion_locally_improve(
+                    suggestion_partition_for( ordered_users, group_sizes )
+                  )
+                end
+
+    best_groups = groupings.min_by do | groups |
+      suggestion_score_for groups
+    end
+    metrics = suggestion_metrics_for best_groups
+
+    {
+      group_sizes: best_groups.map( &:count ),
+      diversity_score_standard_deviation: metrics[:diversity_score_standard_deviation],
+      average_diversity_score: metrics[:average_diversity_score],
+      average_faultline_strength: metrics[:average_faultline_strength],
+      max_faultline_strength: metrics[:max_faultline_strength],
+      groups: best_groups.each_with_index.map do | group_users, index |
+        {
+          name: "Recommended Team #{index + 1}",
+          users: group_users,
+          diversity_score: metrics[:diversity_scores][index],
+          faultline_strength: metrics[:faultline_strengths][index]
+        }
+      end
+    }
+  end
+
   private
 
   class << self
     private
 
+    # Chooses a feasible set of group sizes for the requested roster.
+    #
+    # This keeps every group at size >= 2 and picks the closest balanced layout
+    # to either the requested group count or the requested target group size.
+    def suggested_group_sizes_for( user_count:, target_group_size:, target_group_count: )
+      return [] if user_count < 2
+
+      feasible_group_counts = ( 1..( user_count / 2 ) ).to_a
+      return [user_count] if feasible_group_counts.empty?
+
+      group_count = if target_group_count.present? && target_group_count.to_i.positive?
+                      requested_group_count = target_group_count.to_i
+                      feasible_group_counts.min_by do | count |
+                        sizes = suggestion_balanced_group_sizes_for user_count, count
+                        [
+                          ( count - requested_group_count ).abs,
+                          suggestion_size_distance_for( sizes, user_count.to_f / requested_group_count )
+                        ]
+                      end
+                    else
+                      requested_group_size = [target_group_size.to_i, 2].max
+                      requested_group_size = 4 if requested_group_size.zero?
+                      feasible_group_counts.min_by do | count |
+                        sizes = suggestion_balanced_group_sizes_for user_count, count
+                        [
+                          suggestion_size_distance_for( sizes, requested_group_size ),
+                          ( count - ( user_count.to_f / requested_group_size ) ).abs
+                        ]
+                      end
+                    end
+
+      suggestion_balanced_group_sizes_for user_count, group_count
+    end
+
+    # Splits +user_count+ into as-even-as-possible sizes for +group_count+ groups.
+    def suggestion_balanced_group_sizes_for( user_count, group_count )
+      base_size = user_count / group_count
+      remainder = user_count % group_count
+
+      Array.new( group_count ) do | index |
+        base_size + ( index < remainder ? 1 : 0 )
+      end
+    end
+
+    # Scores how close a proposed set of +group_sizes+ is to +target_group_size+.
+    def suggestion_size_distance_for( group_sizes, target_group_size )
+      [
+        group_sizes.map { | size | ( size - target_group_size ).abs }.max,
+        group_sizes.sum { | size | ( size - target_group_size ).abs },
+        group_sizes.max - group_sizes.min
+      ]
+    end
+
+    # Produces deterministic and shuffled user orderings for the search pass.
+    #
+    # Each ordering is later partitioned into balanced groups so the search can
+    # compare several plausible starting points without changing persisted data.
+    def suggestion_candidate_orders_for( users:, random: )
+      sorted_users = users.sort_by do | user |
+        suggestion_sort_key_for user
+      end
+      candidate_orders = [sorted_users, sorted_users.reverse]
+      [users.count * 2, 12].max.times do
+        candidate_orders << users.shuffle( random: )
+      end
+      candidate_orders
+    end
+
+    # Groups similar demographic profiles together for one candidate ordering.
+    def suggestion_sort_key_for( user )
+      state = user.home_state
+      state = nil if state&.no_response == true
+      country = state&.home_country
+      country = nil if country&.no_response == true
+      gender_code = user.gender&.code
+      primary_language_code = user.primary_language&.code
+      cip_gov_code = user.cip_code&.gov_code
+
+      [
+        country&.id || 0,
+        state&.id || 0,
+        gender_code.to_s,
+        primary_language_code.to_s,
+        cip_gov_code || 0,
+        user.date_of_birth&.year || 0,
+        user.started_school&.year || 0,
+        user.object_id
+      ]
+    end
+
+    # Partitions one ordering of users into groups with the requested sizes.
+    def suggestion_partition_for( ordered_users, group_sizes )
+      groups = Array.new( group_sizes.count ) { [] }
+      remaining_slots = group_sizes.dup
+
+      suggestion_fill_sequence_for( group_sizes ).zip( ordered_users ).each do | group_index, user |
+        next if user.nil? || remaining_slots[group_index].zero?
+
+        groups[group_index] << user
+        remaining_slots[group_index] -= 1
+      end
+
+      groups
+    end
+
+    # Spreads assignments across groups in alternating passes to balance sizes.
+    def suggestion_fill_sequence_for( group_sizes )
+      remaining_slots = group_sizes.dup
+      fill_sequence = []
+      index_sequence = ( 0...group_sizes.count ).to_a
+
+      while remaining_slots.sum.positive?
+        index_sequence.each do | index |
+          next if remaining_slots[index].zero?
+
+          fill_sequence << index
+          remaining_slots[index] -= 1
+        end
+
+        index_sequence.reverse_each do | index |
+          next if remaining_slots[index].zero?
+
+          fill_sequence << index
+          remaining_slots[index] -= 1
+        end
+      end
+
+      fill_sequence
+    end
+
+    # Improves a candidate grouping with pairwise swaps across groups.
+    #
+    # This keeps the chosen group sizes fixed while searching for a lower
+    # diversity-spread and faultline score than the initial partition.
+    def suggestion_locally_improve( groups )
+      current_groups = groups.map( &:dup )
+      current_score = suggestion_score_for current_groups
+
+      [groups.count * 2, 4].max.times do
+        improvement_found = false
+
+        current_groups.each_with_index do | left_group, left_index |
+          break if improvement_found
+
+          ( left_index + 1...current_groups.count ).each do | right_index |
+            right_group = current_groups[right_index]
+
+            left_group.each_index do | left_member_index |
+              break if improvement_found
+
+              right_group.each_index do | right_member_index |
+                candidate_groups = current_groups.map( &:dup )
+                candidate_groups[left_index][left_member_index] = right_group[right_member_index]
+                candidate_groups[right_index][right_member_index] = left_group[left_member_index]
+                candidate_score = suggestion_score_for candidate_groups
+                next unless -1 == ( candidate_score <=> current_score )
+
+                current_groups = candidate_groups
+                current_score = candidate_score
+                improvement_found = true
+                break
+              end
+            end
+          end
+        end
+
+        break unless improvement_found
+      end
+
+      current_groups
+    end
+
+    # Orders candidate groupings using the recommendation objectives.
+    #
+    # Lower diversity-score spread and lower faultline values rank first; higher
+    # average diversity breaks ties in favor of stronger mixed groups.
+    def suggestion_score_for( groups )
+      metrics = suggestion_metrics_for groups
+      [
+        metrics[:diversity_score_standard_deviation],
+        metrics[:average_faultline_strength],
+        -metrics[:average_diversity_score],
+        metrics[:max_faultline_strength]
+      ]
+    end
+
+    # Computes the aggregate metrics returned with a recommendation preview.
+    def suggestion_metrics_for( groups )
+      diversity_scores = groups.map do | group_users |
+        calc_diversity_score_for_group users: group_users
+      end
+      faultline_strengths = groups.map do | group_users |
+        calc_faultline_strength_for_group users: group_users
+      end
+
+      {
+        diversity_scores:,
+        faultline_strengths:,
+        diversity_score_standard_deviation: suggestion_standard_deviation_for( diversity_scores ),
+        average_diversity_score: diversity_scores.sum.to_f / diversity_scores.count,
+        average_faultline_strength: faultline_strengths.sum.to_f / faultline_strengths.count,
+        max_faultline_strength: faultline_strengths.max || 0.0
+      }
+    end
+
+    # Computes a rounded population standard deviation for recommendation scores.
+    def suggestion_standard_deviation_for( values )
+      return 0.0 if values.count <= 1
+
+      average = values.sum.to_f / values.count
+      variance = values.sum { | value| ( value - average )**2 } / values.count
+      Math.sqrt( variance ).round( 4 )
+    end
+
     def faultline_profiles_for( users )
       now = Date.current
       users.map do | user |
diff --git a/config/routes.rb b/config/routes.rb
index 30baa66a..e97b30cd 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -38,6 +38,9 @@
          as: :rescore_group
     post 'projects/rescore_groups/:id' => 'projects#rescore_groups',
          as: :rescore_groups
+    post 'projects/suggest_groups/:id' => 'projects#suggest_groups',
+         as: :suggest_groups,
+         constraints: ->(req) { req.format == :json }
     get 'bingo_games/activate/:bingo_game_id' => 'bingo_games#activate',
         as: :activate_bingo_game
 
diff --git a/features/admin_concept.feature b/features/admin_concept.feature
index 5f1c6d55..423b3520 100644
--- a/features/admin_concept.feature
+++ b/features/admin_concept.feature
@@ -66,7 +66,7 @@ Feature: Concept Administration
     Then the user logs in and accesses the "Concepts" admin page
     Then close all messages
     Then the user updates the "Conceptually Speaking" concept to "good-bye  Conceptually   speaking (CS)"
-    Then the user waits to see "successfully"
+    Then the user sees a success message
     Then the concept "Good-Bye Conceptually Speaking (CS)" will be in the list
     Then a concept will exist named "Good-Bye Conceptually Speaking (CS)"
     Then a concept will not exist named "Conceptually speaking"
diff --git a/features/admin_consent_form_upload.feature b/features/admin_consent_form_upload.feature
index 89d59287..343f402c 100644
--- a/features/admin_consent_form_upload.feature
+++ b/features/admin_consent_form_upload.feature
@@ -16,7 +16,7 @@ Feature: Admin uploads a PDF for a Consent Form
     When the user sets the "Name of the Study" field to "Research Study 2026"
     When the admin uploads a PDF for the consent form
     When the user clicks "Create consent form"
-    Then the user waits to see "successfully"
+    Then the user sees a success message
     Then the new consent form has a PDF stored in Active Storage
     Then the admin sees the PDF link on the consent form page
 
@@ -28,7 +28,7 @@ Feature: Admin uploads a PDF for a Consent Form
     Then the user sees the consent form editing page
     When the admin uploads a PDF for the consent form
     When the user clicks "Save consent form"
-    Then the user waits to see "successfully"
+    Then the user sees a success message
     Then the existing consent form has a PDF stored in Active Storage
     Then the admin sees the PDF link on the consent form page
 
@@ -41,7 +41,7 @@ Feature: Admin uploads a PDF for a Consent Form
     Then the admin sees the PDF link on the consent form page
     When the admin uploads a replacement PDF for the consent form
     When the user clicks "Save consent form"
-    Then the user waits to see "successfully"
+    Then the user sees a success message
     Then the existing consent form has a PDF stored in Active Storage
     Then the replaced PDF is different from the original PDF
     Then the admin sees the PDF link on the consent form page
diff --git a/features/admin_experience.feature b/features/admin_experience.feature
index 1d95fabe..bf957224 100644
--- a/features/admin_experience.feature
+++ b/features/admin_experience.feature
@@ -24,7 +24,7 @@ Feature: Experience Administration
     Then the user sets the "Days for instructor prep" field to "5"
     Then close all messages
     Then the user clicks "Create Experience"
-     And the user waits to see "success"
+     And the user sees a success message
      Then close all messages
     #Let's check the values stored
     Then retrieve the latest Experience from the db
@@ -41,7 +41,7 @@ Feature: Experience Administration
     Then the user sets the "Experience name" field to "Jimmy Hendrix"
     Then close all messages
     Then the user clicks "Create Experience"
-     And the user waits to see "success"
+     And the user sees a success message
      Then close all messages
     #Let's check the values stored
     Then retrieve the latest Experience from the db
@@ -61,7 +61,7 @@ Feature: Experience Administration
     Then the user sets the "experience" start date to "2/29/1980" and the end date to "7/10/2008"
     Then close all messages
     Then the user clicks "Create Experience"
-     And the user waits to see "success"
+     And the user sees a success message
      Then close all messages
     #Let's check the values stored
     Then the user sees the 'experience' 'start date' is '02/29/1980'
@@ -80,7 +80,7 @@ Feature: Experience Administration
     Then the user sets the "experience" start date to "2/29/1980" and the end date to "7/10/2008"
     Then close all messages
     Then the user clicks "Save Experience"
-     And the user waits to see "success"
+     And the user sees a success message
      Then close all messages
     #Let's check the values stored
     Then retrieve the latest Experience from the db
@@ -101,7 +101,7 @@ Feature: Experience Administration
     Then close all messages
     Then the user sets the "Days for instructor prep" field to "5"
     Then the user clicks "Save Experience"
-     And the user waits to see "success"
+     And the user sees a success message
      Then close all messages
     #Let's check the values stored
     Then retrieve the latest Experience from the db
diff --git a/features/admin_project.feature b/features/admin_project.feature
index bb8431b2..4d182549 100644
--- a/features/admin_project.feature
+++ b/features/admin_project.feature
@@ -30,7 +30,7 @@ Feature: Project Administration
     Then the user sets the "Description" field to "this is the coolest"
     Then close all messages
     Then the user clicks "Create Project"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     #Let's check the values stored
     Then the user sees the 'project' 'start date' is '02/29/1980'
@@ -61,7 +61,7 @@ Feature: Project Administration
     Then the user sets the "Description" field to "this is the coolest"
     Then close all messages
     Then the user clicks "Create Project"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     #Let's check the values stored
     Then retrieve the latest project from the db
@@ -90,7 +90,7 @@ Feature: Project Administration
     Then the user sets the "Description" field to "this is the coolest"
     Then close all messages
     Then the user clicks "Save Project"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     Then the user sees the 'project' 'start date' is '05/10/1976'
     Then the user sees the 'project' 'end date' is '02/29/1980'
@@ -122,7 +122,7 @@ Feature: Project Administration
     Then the user sets the "Description" field to "this is the coolest"
     Then close all messages
     Then the user clicks "Create Project"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     #Let's check the values stored
     Then retrieve the latest project from the db
@@ -144,7 +144,7 @@ Feature: Project Administration
     Then the user sets the "Description" field to "this is the coolest"
     Then close all messages
     Then the user clicks "Save Project"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     Then retrieve the latest project from the db
     #Let's check the values stored
@@ -175,7 +175,7 @@ Feature: Project Administration
     Then the user sets the "Description" field to "this is the coolest"
     Then close all messages
     Then the user clicks "Create Project"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     Then the user sees the 'project' 'start date' is '02/29/1980'
     Then the user sees the 'project' 'end date' is '07/10/2008'
@@ -200,7 +200,7 @@ Feature: Project Administration
     Then the user sets the "Description" field to "this is the coolest"
     Then close all messages
     Then the user clicks "Save Project"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     Then the user sees the 'project' 'start date' is '05/10/1976'
     Then the user sees the 'project' 'end date' is '02/29/1980'
@@ -233,7 +233,7 @@ Feature: Project Administration
     Then the user sets the "Description" field to "this is the coolest"
     Then close all messages
     Then the user clicks "Create Project"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     #Let's check the values stored
     Then retrieve the latest project from the db
@@ -255,7 +255,7 @@ Feature: Project Administration
     Then the user sets the "Description" field to "this is the coolest"
     Then close all messages
     Then the user clicks "Save Project"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     Then retrieve the latest project from the db
     #Let's check the values stored
@@ -284,7 +284,7 @@ Feature: Project Administration
     # Then the user sets the "g_-1" field to "my group"
     Then close all messages
     Then the user clicks "Save"
-     And the user waits to see "success"
+     Then the user sees a success message
     Then close all messages
     Then the user adds a group named 'your group'
     # Because the above was saved, this one is -1 again
@@ -294,14 +294,14 @@ Feature: Project Administration
     Then the user sets the "project" start date to "yesterday" and the end date to "tomorrow"
     Then close all messages
     Then the user clicks "Save"
-     And the user waits to see "success"
+     And the user sees a success message
 
     #Edit the groups
     Then the user switches to the "Groups" tab
     Then set user 1 to group "my group"
     Then close all messages
     Then the user clicks "Save"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     Then retrieve the latest project from the db
     Then the project "start" date is "yesterday"
@@ -317,7 +317,7 @@ Feature: Project Administration
     Then set user 4 to group "your group"
     Then close all messages
     Then the user clicks "Save"
-     And the user waits to see "success"
+     And the user sees a success message
     Then close all messages
     Then retrieve the latest project from the db
     Then group "my group" has 2 user
@@ -325,8 +325,68 @@ Feature: Project Administration
     Then group "my group" has 2 revision
     Then group "your group" has 1 revision
 
+ @javascript
+ Scenario: Instructor generates and accepts recommended groups
+   Given the course started "5/10/1976" and ended "4 months hence"
+   Given the project started "last month" and ends "next month", opened "Saturday" and closes "Monday"
+   Given the course started "last month" and ended "next month"
+   Given the user is the instructor for the course
+   Then the user logs in and accesses the "Courses" admin page
+   Then the user sees 1 course
+   Then the user opens the course
+   Then the user clicks on the existing project
+   Then the user switches to the "Groups" tab
+   Then the user requests recommended groups with target count 3
+   Then the user sees 3 recommended groups
+   Then each recommended group has at least 2 members
+   Then the user sees diversity and faultline metrics for the recommended groups
+   Then the user accepts the recommended groups
+   Then close all messages
+   Then retrieve the latest project from the db
+   Then the project has 3 groups
+   Then every enrolled student in the course is assigned to exactly 1 project group
+
+ @javascript
+ Scenario: Instructor rejects recommended groups
+   Given the course started "5/10/1976" and ended "4 months hence"
+   Given the project started "last month" and ends "next month", opened "Saturday" and closes "Monday"
+   Given the course started "last month" and ended "next month"
+   Given the user is the instructor for the course
+   Then the user logs in and accesses the "Courses" admin page
+   Then the user sees 1 course
+   Then the user opens the course
+   Then the user clicks on the existing project
+   Then the user switches to the "Groups" tab
+   Then the user requests recommended groups with target count 3
+   Then the user sees 3 recommended groups
+   Then the user rejects the recommended groups
+   Then the user no longer sees the recommended groups preview
+   Then retrieve the latest project from the db
+   Then the project has 0 groups
+
+ @javascript
+ Scenario: Instructor is warned before replacing existing groups with recommended groups
+   Given the course started "5/10/1976" and ended "4 months hence"
+   Given the project started "last month" and ends "next month", opened "Saturday" and closes "Monday"
+   Given the course started "last month" and ended "next month"
+   Given the user is the instructor for the course
+   Given the project has a group with 4 confirmed users
+   Then the user logs in and accesses the "Courses" admin page
+   Then the user sees 1 course
+   Then the user opens the course
+   Then the user clicks on the existing project
+   Then the user switches to the "Groups" tab
+   Then the user requests recommended groups with target count 3
+   Then the user sees a warning that existing groups will be replaced
+   Then remember the recommended groups
+   Then the user accepts the recommended groups
+   Then close all messages
+   Then retrieve the latest project from the db
+   Then the original project group no longer exists
+   Then the remembered recommended groups exist in the project
+
 @javascript
-  Scenario: Existing Sat-Mon proj=> Fri-Sat on Sat => tomorrow no emails, no access
+ Scenario: Existing Sat-Mon proj=> Fri-Sat on Sat => tomorrow no emails, no access
     Given the email queue is empty
     Given the project has a group with 4 confirmed users
     Given the user is the "a random" user in the group
diff --git a/features/admin_school.feature b/features/admin_school.feature
index ef6ec21c..7cd5662e 100644
--- a/features/admin_school.feature
+++ b/features/admin_school.feature
@@ -16,7 +16,7 @@ Feature: School Administration
      And the user sets the "Description" field to "I love to eat peas and carrots all day long"
     Then close all messages
     Then the user clicks "Create School"
-     And the user waits to see "successfully"
+     And the user sees a success message
     Then close all messages
     Then retrieve the latest school from the db
      And the school "Name" field is "hard knocks"
@@ -39,7 +39,7 @@ Feature: School Administration
     Then close all messages
     Then the user clicks "Create School"
      #We should have success now
-     And the user waits to see "successfully"
+     And the user sees a success message
     Then close all messages
     Then retrieve the latest school from the db
      And the school "Name" field is "life"
diff --git a/features/step_definitions/admin_project_steps.rb b/features/step_definitions/admin_project_steps.rb
index 1e8fcc88..04dc25d8 100644
--- a/features/step_definitions/admin_project_steps.rb
+++ b/features/step_definitions/admin_project_steps.rb
@@ -257,6 +257,95 @@
   Group.find_by( name: group_name ).group_revisions.count.should eq revision_count.to_i
 end
 
+Then( 'the user requests recommended groups with target count {int}' ) do | target_group_count |
+  fill_in 'target_group_count', with: target_group_count
+  step 'the user clicks "Recommend Groups"'
+  step 'the user waits to see "Recommended Groups"'
+end
+
+Then( 'the user sees {int} recommended groups' ) do | group_count |
+  page.all( '.recommended-group-card' ).count.should eq group_count
+end
+
+Then( 'each recommended group has at least {int} members' ) do | minimum_members |
+  page.all( '.recommended-group-card' ).each do | card |
+    member_count = card.text.match( /Members:\s+(\d+)/ )[1].to_i
+    member_count.should be >= minimum_members
+  end
+end
+
+Then( 'the user sees diversity and faultline metrics for the recommended groups' ) do
+  page.should have_content 'Diversity score std. dev.'
+  page.should have_content 'Average diversity score'
+  page.should have_content 'Average faultline strength'
+  page.should have_content 'Max faultline strength'
+  page.all( '.recommended-group-card' ).each do | card |
+    card.text.should include 'Diversity score:'
+    card.text.should include 'Faultline strength:'
+  end
+end
+
+Then( 'the user accepts the recommended groups' ) do
+  step 'the user clicks "Accept Suggested Groups"'
+  step 'the user sees a success message'
+end
+
+Then( 'the user rejects the recommended groups' ) do
+  step 'the user clicks "Reject Suggested Groups"'
+end
+
+Then( 'the user no longer sees the recommended groups preview' ) do
+  page.should have_no_content 'Recommended Groups'
+end
+
+Then( 'the user sees a warning that existing groups will be replaced' ) do
+  page.should have_content 'Accepting these suggested groups will remove and replace the existing project groups.'
+end
+
+Then( 'remember the recommended groups' ) do
+  @recommended_groups = page.all( '.recommended-group-card' ).map do | card |
+    {
+      name: card.find( '.p-panel-title' ).text,
+      members: card.all( 'li' ).map { | item| item.text }
+    }
+  end
+end
+
+Then( 'every enrolled student in the course is assigned to exactly {int} project group' ) do | group_count |
+  appearance_counts = Hash.new( 0 )
+  @project.reload.groups.includes( :users ).each do | group |
+    group.users.each do | user |
+      appearance_counts[user.id] += 1
+    end
+  end
+
+  @course.rosters.enrolled.each do | roster |
+    appearance_counts[roster.user_id].should eq group_count
+  end
+end
+
+Then( 'the original project group no longer exists' ) do
+  Group.find_by( id: @group.id ).should be_nil
+end
+
+Then( 'the remembered recommended groups exist in the project' ) do
+  actual_groups = @project.reload.groups.includes( :users ).map do | group |
+    {
+      name: group.name,
+      members: group.users.map { | user| "#{user.first_name} #{user.last_name}" }.sort
+    }
+  end
+
+  expected_groups = @recommended_groups.map do | group |
+    {
+      name: group[:name],
+      members: group[:members].sort
+    }
+  end
+
+  actual_groups.sort_by { | group| group[:name] }.should eq expected_groups.sort_by { | group| group[:name] }
+end
+
 Then( 'the user selects the {string} menu item' ) do | menu_item |
   search_path = "//*[@id='#{menu_item.downcase}-menu-item']"
   find( :xpath, "//*[@id='administration-menu']" ).click unless has_xpath?( search_path )
diff --git a/package.json b/package.json
index 4924525e..2c760bd9 100644
--- a/package.json
+++ b/package.json
@@ -16,9 +16,9 @@
     "@rspack/core": "^2.2.2",
     "@rspack/dev-server": "^2.2.1",
     "@rspack/plugin-react-refresh": "^2.0.2",
-    "@swc/core": "^1.16.1",
+    "@swc/core": "^1.16.2",
     "@types/react": "^19.2.18",
-    "@types/react-dom": "^19.2.5",
+    "@types/react-dom": "^19.2.7",
     "@types/react-redux": "^7.1.34",
     "@types/stopword": "^2.0.3",
     "@visx/axis": "^4.0.0",
@@ -40,7 +40,7 @@
     "driver.js": "^1.8.0",
     "email-validator": "^2.0.4",
     "html-react-parser": "^6.1.7",
-    "i18next": "^26.4.1",
+    "i18next": "^26.4.2",
     "i18next-browser-languagedetector": "^8.2.1",
     "i18next-fetch-backend": "^8.0.0",
     "i18next-intervalplural-postprocessor": "^3.0.0",
diff --git a/test/models/group_test.rb b/test/models/group_test.rb
index 67f14155..ac354cd5 100644
--- a/test/models/group_test.rb
+++ b/test/models/group_test.rb
@@ -72,6 +72,80 @@ class GroupTest < ActiveSupport::TestCase
     assert_equal 0.0, Group.calc_faultline_strength_for_proposed_group( emails: '  ,   , ' )
   end
 
+  test 'suggest optimal groups assigns each user exactly once with balanced sizes' do
+    users = [
+      faultline_user( group: :a, id: 1 ),
+      faultline_user( group: :a, id: 2 ),
+      faultline_user( group: :a, id: 3 ),
+      faultline_user( group: :b, id: 4 ),
+      faultline_user( group: :b, id: 5 ),
+      faultline_user( group: :b, id: 6 ),
+      faultline_user( group: :b, id: 7 )
+    ]
+
+    suggestion = Group.suggest_optimal_groups( users:, target_group_size: 3 )
+
+    suggested_users = suggestion[:groups].flat_map { | group| group[:users] }
+    suggested_user_ids = suggested_users.map( &:id ).sort
+
+    assert_equal users.map( &:id ).sort, suggested_user_ids
+    assert_equal users.count, suggested_users.count
+    assert_equal [3, 4], suggestion[:group_sizes].sort
+    assert suggestion[:groups].all? { | group| group[:users].count >= 2 }
+    assert suggestion[:groups].all? { | group| group.key?( :diversity_score ) }
+    assert suggestion[:groups].all? { | group| group.key?( :faultline_strength ) }
+  end
+
+  test 'suggest optimal groups honors requested target group count when feasible' do
+    users = 9.times.map do | index |
+      faultline_user( group: index < 4 ? :a : :b, id: index + 1 )
+    end
+
+    suggestion = Group.suggest_optimal_groups( users:, target_group_count: 4 )
+
+    assert_equal 4, suggestion[:groups].count
+    assert_equal [2, 2, 2, 3], suggestion[:group_sizes].sort
+  end
+
+  test 'suggest optimal groups falls back to the nearest feasible group count' do
+    users = 5.times.map do | index |
+      faultline_user( group: index < 2 ? :a : :b, id: index + 1 )
+    end
+
+    suggestion = Group.suggest_optimal_groups( users:, target_group_count: 3 )
+
+    assert_equal 2, suggestion[:groups].count
+    assert_equal [2, 3], suggestion[:group_sizes].sort
+  end
+
+  test 'suggest optimal groups handles nil demographics without delegation errors' do
+    users = [
+      faultline_user_without_demographics( id: 1 ),
+      faultline_user_without_demographics( id: 2 ),
+      faultline_user_without_demographics( id: 3 ),
+      faultline_user_without_demographics( id: 4 )
+    ]
+
+    assert_nothing_raised do
+      suggestion = Group.suggest_optimal_groups( users:, target_group_count: 2 )
+      assert_equal [2, 2], suggestion[:group_sizes].sort
+    end
+  end
+
+  test 'suggest optimal groups handles states without countries' do
+    users = [
+      faultline_user_with_state_without_country( id: 1 ),
+      faultline_user_with_state_without_country( id: 2 ),
+      faultline_user_without_demographics( id: 3 ),
+      faultline_user_without_demographics( id: 4 )
+    ]
+
+    assert_nothing_raised do
+      suggestion = Group.suggest_optimal_groups( users:, target_group_count: 2 )
+      assert_equal [2, 2], suggestion[:group_sizes].sort
+    end
+  end
+
   private
 
   class MockFaultlineUserRelation
@@ -93,7 +167,7 @@ def includes( *_args )
     end
   end
 
-  def faultline_user( group: )
+  def faultline_user( group:, id: nil )
     country_id = ( group == :a ? 1 : 2 )
     state_id = ( group == :a ? 11 : 22 )
     gender_id = ( group == :a ? 101 : 202 )
@@ -104,6 +178,7 @@ def faultline_user( group: )
     birth_year = ( group == :a ? 2004 : 1997 )
 
     OpenStruct.new(
+      id:,
       home_state: OpenStruct.new(
         id: state_id,
         home_country: OpenStruct.new( id: country_id, no_response: false )
@@ -126,8 +201,9 @@ def faultline_user( group: )
     )
   end
 
-  def faultline_user_without_demographics
+  def faultline_user_without_demographics( id: nil )
     OpenStruct.new(
+      id:,
       home_state: nil,
       cip_code: nil,
       gender: nil,
@@ -143,4 +219,23 @@ def faultline_user_without_demographics
       started_school?: false
     )
   end
+
+  def faultline_user_with_state_without_country( id: nil )
+    OpenStruct.new(
+      id:,
+      home_state: OpenStruct.new( id: 99, no_response: false, home_country: nil ),
+      cip_code: nil,
+      gender: nil,
+      primary_language: nil,
+      impairment_visual: false,
+      impairment_auditory: false,
+      impairment_motor: false,
+      impairment_cognitive: false,
+      impairment_other: false,
+      date_of_birth: nil,
+      started_school: nil,
+      date_of_birth?: false,
+      started_school?: false
+    )
+  end
 end
diff --git a/yarn.lock b/yarn.lock
index fa6089f4..d8be318b 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -660,106 +660,106 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@swc/core-darwin-arm64@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-darwin-arm64@npm:1.16.1"
+"@swc/core-darwin-arm64@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-darwin-arm64@npm:1.16.2"
   conditions: os=darwin & cpu=arm64
   languageName: node
   linkType: hard
 
-"@swc/core-darwin-x64@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-darwin-x64@npm:1.16.1"
+"@swc/core-darwin-x64@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-darwin-x64@npm:1.16.2"
   conditions: os=darwin & cpu=x64
   languageName: node
   linkType: hard
 
-"@swc/core-linux-arm-gnueabihf@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-linux-arm-gnueabihf@npm:1.16.1"
+"@swc/core-linux-arm-gnueabihf@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-linux-arm-gnueabihf@npm:1.16.2"
   conditions: os=linux & cpu=arm
   languageName: node
   linkType: hard
 
-"@swc/core-linux-arm64-gnu@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-linux-arm64-gnu@npm:1.16.1"
+"@swc/core-linux-arm64-gnu@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-linux-arm64-gnu@npm:1.16.2"
   conditions: os=linux & cpu=arm64 & libc=glibc
   languageName: node
   linkType: hard
 
-"@swc/core-linux-arm64-musl@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-linux-arm64-musl@npm:1.16.1"
+"@swc/core-linux-arm64-musl@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-linux-arm64-musl@npm:1.16.2"
   conditions: os=linux & cpu=arm64 & libc=musl
   languageName: node
   linkType: hard
 
-"@swc/core-linux-ppc64-gnu@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-linux-ppc64-gnu@npm:1.16.1"
+"@swc/core-linux-ppc64-gnu@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-linux-ppc64-gnu@npm:1.16.2"
   conditions: os=linux & cpu=ppc64 & libc=glibc
   languageName: node
   linkType: hard
 
-"@swc/core-linux-s390x-gnu@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-linux-s390x-gnu@npm:1.16.1"
+"@swc/core-linux-s390x-gnu@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-linux-s390x-gnu@npm:1.16.2"
   conditions: os=linux & cpu=s390x & libc=glibc
   languageName: node
   linkType: hard
 
-"@swc/core-linux-x64-gnu@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-linux-x64-gnu@npm:1.16.1"
+"@swc/core-linux-x64-gnu@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-linux-x64-gnu@npm:1.16.2"
   conditions: os=linux & cpu=x64 & libc=glibc
   languageName: node
   linkType: hard
 
-"@swc/core-linux-x64-musl@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-linux-x64-musl@npm:1.16.1"
+"@swc/core-linux-x64-musl@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-linux-x64-musl@npm:1.16.2"
   conditions: os=linux & cpu=x64 & libc=musl
   languageName: node
   linkType: hard
 
-"@swc/core-win32-arm64-msvc@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-win32-arm64-msvc@npm:1.16.1"
+"@swc/core-win32-arm64-msvc@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-win32-arm64-msvc@npm:1.16.2"
   conditions: os=win32 & cpu=arm64
   languageName: node
   linkType: hard
 
-"@swc/core-win32-ia32-msvc@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-win32-ia32-msvc@npm:1.16.1"
+"@swc/core-win32-ia32-msvc@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-win32-ia32-msvc@npm:1.16.2"
   conditions: os=win32 & cpu=ia32
   languageName: node
   linkType: hard
 
-"@swc/core-win32-x64-msvc@npm:1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core-win32-x64-msvc@npm:1.16.1"
+"@swc/core-win32-x64-msvc@npm:1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core-win32-x64-msvc@npm:1.16.2"
   conditions: os=win32 & cpu=x64
   languageName: node
   linkType: hard
 
-"@swc/core@npm:^1.16.1":
-  version: 1.16.1
-  resolution: "@swc/core@npm:1.16.1"
+"@swc/core@npm:^1.16.2":
+  version: 1.16.2
+  resolution: "@swc/core@npm:1.16.2"
   dependencies:
-    "@swc/core-darwin-arm64": "npm:1.16.1"
-    "@swc/core-darwin-x64": "npm:1.16.1"
-    "@swc/core-linux-arm-gnueabihf": "npm:1.16.1"
-    "@swc/core-linux-arm64-gnu": "npm:1.16.1"
-    "@swc/core-linux-arm64-musl": "npm:1.16.1"
-    "@swc/core-linux-ppc64-gnu": "npm:1.16.1"
-    "@swc/core-linux-s390x-gnu": "npm:1.16.1"
-    "@swc/core-linux-x64-gnu": "npm:1.16.1"
-    "@swc/core-linux-x64-musl": "npm:1.16.1"
-    "@swc/core-win32-arm64-msvc": "npm:1.16.1"
-    "@swc/core-win32-ia32-msvc": "npm:1.16.1"
-    "@swc/core-win32-x64-msvc": "npm:1.16.1"
+    "@swc/core-darwin-arm64": "npm:1.16.2"
+    "@swc/core-darwin-x64": "npm:1.16.2"
+    "@swc/core-linux-arm-gnueabihf": "npm:1.16.2"
+    "@swc/core-linux-arm64-gnu": "npm:1.16.2"
+    "@swc/core-linux-arm64-musl": "npm:1.16.2"
+    "@swc/core-linux-ppc64-gnu": "npm:1.16.2"
+    "@swc/core-linux-s390x-gnu": "npm:1.16.2"
+    "@swc/core-linux-x64-gnu": "npm:1.16.2"
+    "@swc/core-linux-x64-musl": "npm:1.16.2"
+    "@swc/core-win32-arm64-msvc": "npm:1.16.2"
+    "@swc/core-win32-ia32-msvc": "npm:1.16.2"
+    "@swc/core-win32-x64-msvc": "npm:1.16.2"
     "@swc/counter": "npm:^0.1.3"
     "@swc/types": "npm:^0.1.28"
   peerDependencies:
@@ -792,7 +792,7 @@ __metadata:
   peerDependenciesMeta:
     "@swc/helpers":
       optional: true
-  checksum: 10c0/6711717ac132d7feba331d70d266faec2197951531b1d4faaaa4ceee415f4739c8c4b5c18a48fc04fee084df37c5713b395eb91f024707efdd0aff6d155748ae
+  checksum: 10c0/8019735e27852f03b0e09ae7f8c3f00e6a2e3f49b72127e09c20cffde335fe3b776afb20bfd3b3f5c540d42667f1b7467a4e10aa11c50ff59c6f86a9513544a8
   languageName: node
   linkType: hard
 
@@ -991,12 +991,12 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@types/react-dom@npm:^19.2.5":
-  version: 19.2.5
-  resolution: "@types/react-dom@npm:19.2.5"
+"@types/react-dom@npm:^19.2.7":
+  version: 19.2.7
+  resolution: "@types/react-dom@npm:19.2.7"
   peerDependencies:
     "@types/react": ^19.2.0
-  checksum: 10c0/7a59467b043debf392d109daa1ba672e791f20ce6f24ae81fb54715f890f8119d24967e61e3644b6307428603b695b7d59e69eaf531bd1963a74a6cb462f5f49
+  checksum: 10c0/226ab7e2b62114125e2276b3dcc3a25060177a673f8abadb7e31f395003de72ad68075c6edc5f51b02dd1e47443920ee030239c474c47fad075ded7410836909
   languageName: node
   linkType: hard
 
@@ -1619,12 +1619,12 @@ __metadata:
     "@rspack/core": "npm:^2.2.2"
     "@rspack/dev-server": "npm:^2.2.1"
     "@rspack/plugin-react-refresh": "npm:^2.0.2"
-    "@swc/core": "npm:^1.16.1"
+    "@swc/core": "npm:^1.16.2"
     "@types/d3-array": "npm:^3.2.2"
     "@types/d3-time-format": "npm:^4.0.3"
     "@types/react": "npm:^19.2.18"
     "@types/react-big-calendar": "npm:^1.16.3"
-    "@types/react-dom": "npm:^19.2.5"
+    "@types/react-dom": "npm:^19.2.7"
     "@types/react-redux": "npm:^7.1.34"
     "@types/stopword": "npm:^2.0.3"
     "@visx/axis": "npm:^4.0.0"
@@ -1646,7 +1646,7 @@ __metadata:
     driver.js: "npm:^1.8.0"
     email-validator: "npm:^2.0.4"
     html-react-parser: "npm:^6.1.7"
-    i18next: "npm:^26.4.1"
+    i18next: "npm:^26.4.2"
     i18next-browser-languagedetector: "npm:^8.2.1"
     i18next-fetch-backend: "npm:^8.0.0"
     i18next-intervalplural-postprocessor: "npm:^3.0.0"
@@ -2512,15 +2512,15 @@ __metadata:
   languageName: node
   linkType: hard
 
-"i18next@npm:^26.4.1":
-  version: 26.4.1
-  resolution: "i18next@npm:26.4.1"
+"i18next@npm:^26.4.2":
+  version: 26.4.2
+  resolution: "i18next@npm:26.4.2"
   peerDependencies:
     typescript: ^5 || ^6 || ^7
   peerDependenciesMeta:
     typescript:
       optional: true
-  checksum: 10c0/d378fdef07d07b3bbaa803ca18bf663bfcb203ab4be5eb8da2f1eb49e5559efcaf731f0cf34deccfe804c465f1cab8948d58f9303afe6921bc18949cb170df5e
+  checksum: 10c0/f2c9613e03e09e56a84aee939d8fbe3442a58622915e11f97e47f9ab358dfa65be783230b37a21483152711f786fccfe697d7f5ea9269c54f16179dc59960e4b
   languageName: node
   linkType: hard