fix(people): "Mutual connections" rendered nothing — /mutual returns counts, not users

InterlinedList/Models/MutualFollowCounts.cs

@@ -0,0 +1,40 @@
+namespace InterlinedList.Models;
+
+/// <summary>
+/// How many follows two accounts have in common, from
+/// <c>GET /api/follow/{userId}/mutual</c>.
+/// </summary>
+/// <remarks>
+/// <para>
+/// <b>Counts only — there is no endpoint that lists the mutual users.</b>
+/// Verified live 2026-09-16 across both documented parameter forms:
+/// </para>
+/// <code>
+/// GET /api/follow/{userId}/mutual                      -> {"mutualFollowers":1,"mutualFollowing":1}
+/// GET /api/follow/{userId}/mutual?otherUserId={other}  -> {"mutualFollowers":1,"mutualFollowing":1}
+/// </code>
+/// <para>
+/// So clickable "mutual connections" chips cannot be built — don't reinstate
+/// them against this endpoint. The previous <c>GetMutualAsync</c> asked for an
+/// array under a <c>mutual</c> key, which is absent, and the tolerant
+/// array reader turned that into an empty list: the feature rendered nothing
+/// and reported no error. See #160.
+/// </para>
+/// </remarks>
+public sealed class MutualFollowCounts
+{
+    /// <summary>Accounts that follow both the viewer and the profile.</summary>
+    public int MutualFollowers { get; init; }
+
+    /// <summary>Accounts both the viewer and the profile follow.</summary>
+    public int MutualFollowing { get; init; }
+
+    public bool HasAny => MutualFollowers > 0 || MutualFollowing > 0;
+
+    /// <summary>A single human line, or null when there is nothing to say.</summary>
+    public string? Summary => HasAny
+        ? $"{MutualFollowing} mutual following · {MutualFollowers} mutual followers"
+        : null;
+
+    public static MutualFollowCounts None => new();
+}

InterlinedList/Services/InterlinedApiClient.Follow.cs

@@ -39,6 +39,31 @@ public Task<List<FollowUser>> GetFollowersAsync(string userId, CancellationToken
     public Task<List<FollowUser>> GetFollowingAsync(string userId, CancellationToken ct = default)
         => GetUserArrayAsync($"api/follow/{userId}/following", "following", ct);
 
+    /// <summary>
+    /// Mutual-follow <b>counts</b> between the caller and <paramref name="userId"/>.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This replaces a <c>Task&lt;List&lt;FollowUser&gt;&gt;</c> signature that the API
+    /// cannot satisfy. The endpoint returns
+    /// <c>{"mutualFollowers":n,"mutualFollowing":n}</c> — never a user array —
+    /// so the old call asked <see cref="GetUserArrayAsync"/> for an absent
+    /// <c>mutual</c> key and silently received an empty list, which is why the
+    /// profile's "Mutual connections" chips never rendered. See #160.
+    /// </para>
+    /// <para>
+    /// There is <b>no</b> endpoint that lists the mutual users — both this
+    /// route's parameter forms (bare, and with the spec-documented
+    /// <c>otherUserId</c>) return the same counts object.
+    /// </para>
+    /// </remarks>
+    public async Task<MutualFollowCounts> GetMutualCountsAsync(string userId, CancellationToken ct = default)
+    {
+        var json = await GetElementAsync($"api/follow/{userId}/mutual", ct);
+        return json.ValueKind == JsonValueKind.Object
+            ? json.Deserialize<MutualFollowCounts>(JsonOptions) ?? MutualFollowCounts.None
+            : MutualFollowCounts.None;
+    }
     /// <summary>One page of a user's followers.</summary>
     /// <param name="status">
     /// Optional server-side filter on the follow edge's state. Live values seen:
@@ -62,11 +87,15 @@ public Task<FollowUserPage> GetFollowingPageAsync(
         string userId, int limit = 50, int offset = 0, string? status = null, CancellationToken ct = default)
         => GetUserPageAsync($"api/follow/{userId}/following", "following", limit, offset, status, ct);
 
-    public Task<List<FollowUser>> GetMutualAsync(string userId, CancellationToken ct = default)
-        => GetUserArrayAsync($"api/follow/{userId}/mutual", "mutual", ct);
-
-    // Follow lists wrap their array under different property names
-    // (requests/followers/following/mutual) — pull the named array, tolerate a miss.
+    // Follow lists wrap their array under different property names — pull the
+    // named array, tolerate a miss.
+    //
+    // Keys verified live 2026-09-16: `requests` -> {"requests":[]},
+    // `followers`/`following` -> {"<key>":[…],"pagination":{…}}. NOTE `mutual`
+    // is NOT one of these — that endpoint returns counts, not an array, and
+    // this helper's tolerance silently hid the mismatch for weeks (#160). If you
+    // add a key here, confirm the array actually exists in a live payload; a
+    // wrong key fails as "feature renders nothing", not as an error.
     private async Task<List<FollowUser>> GetUserArrayAsync(string path, string property, CancellationToken ct)
     {
         var json = await GetElementAsync(path, ct);

InterlinedList/ViewModels/ProfileViewModel.cs

@@ -17,7 +17,15 @@ public partial class ProfileViewModel : ObservableObject
 
     public ObservableCollection<FollowUser> FollowRequests { get; } = new();
     public ObservableCollection<MessageItemViewModel> Messages { get; } = new();
-    public ObservableCollection<FollowUser> Mutuals { get; } = new();
+    /// <summary>
+    /// Mutual-follow counts. The API exposes counts only — there is no endpoint
+    /// listing the mutual users, so the old clickable chips could never work
+    /// (#160).
+    /// </summary>
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(HasMutuals))]
+    [NotifyPropertyChangedFor(nameof(MutualsSummary))]
+    private MutualFollowCounts? mutuals;
 
     /// <summary>The profile's followers, paged. Server default page is 50.</summary>
     public ObservableCollection<FollowUser> Followers { get; } = new();
@@ -82,7 +90,9 @@ public partial class ProfileViewModel : ObservableObject
 
     public bool HasProfile => Profile is not null;
 
-    public bool HasMutuals => Mutuals.Count > 0;
+    public bool HasMutuals => Mutuals?.HasAny == true;
+
+    public string MutualsSummary => Mutuals?.Summary ?? string.Empty;
 
     public string FollowButtonText =>
         Relationship?.IsFollowing == true ? "Following"
@@ -97,7 +107,6 @@ public ProfileViewModel(SessionService session)
     {
         _session = session;
         FollowRequests.CollectionChanged += (_, _) => OnPropertyChanged(nameof(HasRequests));
-        Mutuals.CollectionChanged += (_, _) => OnPropertyChanged(nameof(HasMutuals));
     }
 
     [RelayCommand]
@@ -158,9 +167,7 @@ private async Task LoadProfileAsync()
             foreach (var message in page.Messages)
                 Messages.Add(new MessageItemViewModel(message, _session.Api, _session.CurrentUser?.Id));
 
-            Mutuals.Clear();
-            foreach (var mutual in await _session.Api.GetMutualAsync(profile.Id))
-                Mutuals.Add(mutual);
+            Mutuals = await _session.Api.GetMutualCountsAsync(profile.Id);
 
             IsOwnProfile = profile.Id == _session.CurrentUser?.Id;
 

InterlinedList/Views/PeopleView.xaml

@@ -428,40 +428,22 @@
                         </StackPanel>
                     </Border>
 
-                    <!-- Mutual connections -->
-                    <StackPanel Margin="0,0,0,12"
-                                Visibility="{Binding HasMutuals, Converter={StaticResource BoolToVis}}">
-                        <TextBlock Text="Mutual connections"
-                                   FontSize="12" FontWeight="SemiBold"
-                                   Foreground="{DynamicResource TextBrush}" Margin="0,0,0,6"/>
-                        <ItemsControl ItemsSource="{Binding Mutuals}">
-                            <ItemsControl.ItemsPanel>
-                                <ItemsPanelTemplate><WrapPanel/></ItemsPanelTemplate>
-                            </ItemsControl.ItemsPanel>
-                            <ItemsControl.ItemTemplate>
-                                <DataTemplate>
-                                    <Button Command="{Binding DataContext.OpenUserCommand,
-                                                      RelativeSource={RelativeSource AncestorType=UserControl}}"
-                                            CommandParameter="{Binding}"
-                                            Background="Transparent" BorderThickness="0" Cursor="Hand"
-                                            Margin="0,0,6,6" Padding="0">
-                                        <Border Background="{DynamicResource Surface2Brush}"
-                                                BorderBrush="{DynamicResource BorderBrush}" BorderThickness="1"
-                                                CornerRadius="3" Padding="8,4">
-                                            <StackPanel Orientation="Horizontal">
-                                                <Border Width="18" Height="18" CornerRadius="999" ClipToBounds="True"
-                                                        Background="{DynamicResource Surface3Brush}" Margin="0,0,6,0">
-                                                    <Image Source="{Binding Avatar}" Stretch="UniformToFill"/>
-                                                </Border>
-                                                <TextBlock Text="{Binding DisplayNameOrUsername}" FontSize="11"
-                                                           Foreground="{DynamicResource TextBodyBrush}" VerticalAlignment="Center"/>
-                                            </StackPanel>
-                                        </Border>
-                                    </Button>
-                                </DataTemplate>
-                            </ItemsControl.ItemTemplate>
-                        </ItemsControl>
-                    </StackPanel>
+                    <!-- Mutual follows. Counts only: the API has no endpoint
+                         that lists the mutual users, so the clickable chips that
+                         used to be here could never render anything (#160). -->
+                    <Border Margin="0,0,0,12"
+                            Background="{DynamicResource Surface2Brush}"
+                            BorderBrush="{DynamicResource BorderBrush}"
+                            BorderThickness="1"
+                            CornerRadius="3"
+                            Padding="10,6"
+                            Visibility="{Binding HasMutuals, Converter={StaticResource BoolToVis}}">
+                        <TextBlock Text="{Binding MutualsSummary}"
+                                   FontFamily="JetBrains Mono, Consolas"
+                                   FontSize="10"
+                                   Foreground="{DynamicResource TextBodyBrush}"
+                                   TextWrapping="Wrap"/>
+                    </Border>
 
                     <!-- Followers / following. Paged: the server's default page
                          is 50, so anyone with more had the rest silently dropped.