diff --git a/src/TeamsISO.App/Assets/Fonts/JetBrainsMono.ttf b/src/TeamsISO.App/Assets/Fonts/JetBrainsMono.ttf
new file mode 100644
index 0000000..b60e77f
Binary files /dev/null and b/src/TeamsISO.App/Assets/Fonts/JetBrainsMono.ttf differ
diff --git a/src/TeamsISO.App/Converters/CountToVisibilityConverter.cs b/src/TeamsISO.App/Converters/CountToVisibilityConverter.cs
new file mode 100644
index 0000000..dae52e0
--- /dev/null
+++ b/src/TeamsISO.App/Converters/CountToVisibilityConverter.cs
@@ -0,0 +1,32 @@
+using System.Collections;
+using System.Globalization;
+using System.Windows;
+using System.Windows.Data;
+
+namespace TeamsISO.App.Converters;
+
+/// <summary>
+/// Maps a collection (or its count) to <see cref="Visibility"/>. Pass
+/// <c>"empty"</c> as the converter parameter to invert the sense (Visible when
+/// count == 0). Used to swap an empty-state placeholder in for the participants
+/// DataGrid when no Teams sources are visible yet.
+/// </summary>
+public sealed class CountToVisibilityConverter : IValueConverter
+{
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        var count = value switch
+        {
+            int n => n,
+            ICollection c => c.Count,
+            null => 0,
+            _ => 1, // anything else: treat as non-empty
+        };
+        var invert = string.Equals(parameter as string, "empty", StringComparison.OrdinalIgnoreCase);
+        var visible = invert ? count == 0 : count > 0;
+        return visible ? Visibility.Visible : Visibility.Collapsed;
+    }
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture) =>
+        throw new NotSupportedException();
+}
diff --git a/src/TeamsISO.App/MainWindow.xaml b/src/TeamsISO.App/MainWindow.xaml
index e8fd153..4a1fae8 100644
--- a/src/TeamsISO.App/MainWindow.xaml
+++ b/src/TeamsISO.App/MainWindow.xaml
@@ -35,6 +35,7 @@
         <conv:BoolToVisibilityConverter x:Key="BoolToVis"/>
         <conv:EnumDescriptionConverter x:Key="EnumDesc"/>
         <conv:InitialsConverter x:Key="Initials"/>
+        <conv:CountToVisibilityConverter x:Key="CountToVis"/>
     </Window.Resources>
 
     <Grid>
@@ -352,8 +353,77 @@
                 <Border Grid.Row="2"
                         Style="{StaticResource Wd.Card}"
                         Padding="0">
-                    <DataGrid ItemsSource="{Binding Participants}"
-                              Margin="6,4,6,4">
+                    <Grid>
+                        <!-- Empty-state placeholder. Visible when Participants.Count == 0. -->
+                        <StackPanel Visibility="{Binding Participants.Count, Converter={StaticResource CountToVis}, ConverterParameter=empty}"
+                                    HorizontalAlignment="Center"
+                                    VerticalAlignment="Center"
+                                    MaxWidth="460"
+                                    Margin="32,48">
+                            <Image Source="/Assets/dragon-mark.png"
+                                   Width="64" Height="64"
+                                   Opacity="0.45"
+                                   HorizontalAlignment="Center"
+                                   Margin="0,0,0,20"
+                                   RenderOptions.BitmapScalingMode="HighQuality"/>
+                            <TextBlock Text="Waiting for Teams"
+                                       Style="{StaticResource Wd.Text.Heading}"
+                                       FontSize="16"
+                                       HorizontalAlignment="Center"/>
+                            <TextBlock Style="{StaticResource Wd.Text.Subtle}"
+                                       Foreground="{DynamicResource Wd.Text.Tertiary}"
+                                       HorizontalAlignment="Center"
+                                       TextAlignment="Center"
+                                       TextWrapping="Wrap"
+                                       Margin="0,8,0,20"
+                                       Text="No Teams participants discovered on the network yet. Once Teams broadcasts NDI sources, this list will populate within a few seconds."/>
+
+                            <Border Style="{StaticResource Wd.Card}"
+                                    Background="{DynamicResource Wd.SurfaceElevated}"
+                                    Padding="16,12">
+                                <StackPanel>
+                                    <TextBlock Text="QUICK CHECKLIST"
+                                               Style="{StaticResource Wd.Text.Caption}"
+                                               Margin="0,0,0,8"/>
+                                    <TextBlock Style="{StaticResource Wd.Text.Subtle}"
+                                               Foreground="{DynamicResource Wd.Text.Secondary}"
+                                               TextWrapping="Wrap"
+                                               FontSize="12"
+                                               Margin="0,0,0,4">
+                                        <Run Text="•"/>
+                                        <Run Text=" Microsoft Teams is running and a meeting is active"/>
+                                    </TextBlock>
+                                    <TextBlock Style="{StaticResource Wd.Text.Subtle}"
+                                               Foreground="{DynamicResource Wd.Text.Secondary}"
+                                               TextWrapping="Wrap"
+                                               FontSize="12"
+                                               Margin="0,0,0,4">
+                                        <Run Text="•"/>
+                                        <Run Text=" NDI broadcast is enabled in Teams settings"/>
+                                    </TextBlock>
+                                    <TextBlock Style="{StaticResource Wd.Text.Subtle}"
+                                               Foreground="{DynamicResource Wd.Text.Secondary}"
+                                               TextWrapping="Wrap"
+                                               FontSize="12"
+                                               Margin="0,0,0,4">
+                                        <Run Text="•"/>
+                                        <Run Text=" Discovery group in Settings matches Teams' broadcast group"/>
+                                    </TextBlock>
+                                    <TextBlock Style="{StaticResource Wd.Text.Subtle}"
+                                               Foreground="{DynamicResource Wd.Text.Secondary}"
+                                               TextWrapping="Wrap"
+                                               FontSize="12">
+                                        <Run Text="•"/>
+                                        <Run Text=" Windows Firewall isn't blocking NDI multicast on the active network adapter"/>
+                                    </TextBlock>
+                                </StackPanel>
+                            </Border>
+                        </StackPanel>
+
+                        <!-- DataGrid: visible only when Participants.Count > 0. -->
+                        <DataGrid ItemsSource="{Binding Participants}"
+                                  Visibility="{Binding Participants.Count, Converter={StaticResource CountToVis}}"
+                                  Margin="6,4,6,4">
                         <DataGrid.Columns>
                             <DataGridTemplateColumn Header="Display Name" Width="2*">
                                 <DataGridTemplateColumn.CellTemplate>
@@ -424,7 +494,8 @@
                                         <TextBox Text="{Binding CustomName, UpdateSourceTrigger=PropertyChanged}"
                                                  Padding="10,7"
                                                  Margin="0,0,12,0"
-                                                 VerticalAlignment="Center"/>
+                                                 VerticalAlignment="Center"
+                                                 ToolTip="Override the auto-generated NDI output name (TEAMSISO_xxxxxxxx). Takes effect when ISO is enabled."/>
                                     </DataTemplate>
                                 </DataGridTemplateColumn.CellTemplate>
                             </DataGridTemplateColumn>
@@ -433,7 +504,8 @@
                                 <DataGridTemplateColumn.CellTemplate>
                                     <DataTemplate>
                                         <Button Command="{Binding ToggleIsoCommand}"
-                                                Margin="0,0,12,0">
+                                                Margin="0,0,12,0"
+                                                ToolTip="Toggle this participant's normalized NDI ISO output">
                                             <Button.Style>
                                                 <Style TargetType="Button" BasedOn="{StaticResource Wd.Button.IsoToggle}">
                                                     <Setter Property="Content" Value="Enable"/>
@@ -445,6 +517,19 @@
                                                             <Setter Property="BorderBrush" Value="{DynamicResource Wd.Accent.Cyan}"/>
                                                             <Setter Property="Foreground" Value="{DynamicResource Wd.Accent.Cyan}"/>
                                                         </DataTrigger>
+                                                        <!-- Pipeline failed past retry budget — surface the error state in coral. -->
+                                                        <DataTrigger Binding="{Binding StateLabel}" Value="ERROR">
+                                                            <Setter Property="Content" Value="● ERROR"/>
+                                                            <Setter Property="Background" Value="{DynamicResource Wd.Accent.CoralBg}"/>
+                                                            <Setter Property="BorderBrush" Value="{DynamicResource Wd.Accent.Coral}"/>
+                                                            <Setter Property="Foreground" Value="{DynamicResource Wd.Accent.Coral}"/>
+                                                        </DataTrigger>
+                                                        <!-- No frames received in slate-threshold window — amber warning. -->
+                                                        <DataTrigger Binding="{Binding StateLabel}" Value="NO SIGNAL">
+                                                            <Setter Property="Content" Value="● NO SIGNAL"/>
+                                                            <Setter Property="Foreground" Value="{DynamicResource Wd.Status.Warn}"/>
+                                                            <Setter Property="BorderBrush" Value="{DynamicResource Wd.Status.Warn}"/>
+                                                        </DataTrigger>
                                                         <DataTrigger Binding="{Binding IsProcessing}" Value="True">
                                                             <Setter Property="Content" Value="…"/>
                                                             <Setter Property="IsEnabled" Value="False"/>
@@ -458,6 +543,7 @@
                             </DataGridTemplateColumn>
                         </DataGrid.Columns>
                     </DataGrid>
+                    </Grid>
                 </Border>
             </Grid>
         </DockPanel>
@@ -488,7 +574,8 @@
                                Style="{StaticResource Wd.Text.Subtle}"
                                Margin="0,10,0,4"/>
                     <ComboBox ItemsSource="{Binding Settings.AvailableFramerates}"
-                              SelectedItem="{Binding Settings.Framerate}">
+                              SelectedItem="{Binding Settings.Framerate}"
+                              ToolTip="The framerate every ISO output is normalized to. Click Apply to commit.">
                         <ComboBox.ItemTemplate>
                             <DataTemplate>
                                 <TextBlock Text="{Binding Converter={StaticResource EnumDesc}}"/>
@@ -500,7 +587,8 @@
                                Style="{StaticResource Wd.Text.Subtle}"
                                Margin="0,12,0,4"/>
                     <ComboBox ItemsSource="{Binding Settings.AvailableResolutions}"
-                              SelectedItem="{Binding Settings.Resolution}">
+                              SelectedItem="{Binding Settings.Resolution}"
+                              ToolTip="Output resolution. Source frames smaller than this are scaled up; larger frames are scaled down.">
                         <ComboBox.ItemTemplate>
                             <DataTemplate>
                                 <TextBlock Text="{Binding Converter={StaticResource EnumDesc}}"/>
@@ -512,7 +600,8 @@
                                Style="{StaticResource Wd.Text.Subtle}"
                                Margin="0,12,0,4"/>
                     <ComboBox ItemsSource="{Binding Settings.AvailableAspectModes}"
-                              SelectedItem="{Binding Settings.Aspect}">
+                              SelectedItem="{Binding Settings.Aspect}"
+                              ToolTip="How to fit non-matching aspect ratios. Pillarbox = bars on the sides; Letterbox = bars top/bottom; Stretch = distort to fill.">
                         <ComboBox.ItemTemplate>
                             <DataTemplate>
                                 <TextBlock Text="{Binding Converter={StaticResource EnumDesc}}"/>
@@ -524,7 +613,8 @@
                                Style="{StaticResource Wd.Text.Subtle}"
                                Margin="0,12,0,4"/>
                     <ComboBox ItemsSource="{Binding Settings.AvailableAudioModes}"
-                              SelectedItem="{Binding Settings.Audio}">
+                              SelectedItem="{Binding Settings.Audio}"
+                              ToolTip="Audio routing for ISO outputs. Auto = isolated when available, fall back to mixed; Isolated = participant audio only; Mixed = full meeting mix.">
                         <ComboBox.ItemTemplate>
                             <DataTemplate>
                                 <TextBlock Text="{Binding Converter={StaticResource EnumDesc}}"/>
@@ -540,7 +630,8 @@
                     <TextBlock Text="Discovery group"
                                Style="{StaticResource Wd.Text.Subtle}"
                                Margin="0,10,0,4"/>
-                    <TextBox Text="{Binding Settings.DiscoveryGroups, UpdateSourceTrigger=PropertyChanged}"/>
+                    <TextBox Text="{Binding Settings.DiscoveryGroups, UpdateSourceTrigger=PropertyChanged}"
+                             ToolTip="Comma-separated NDI group names the engine subscribes to. Empty = Public (default)."/>
                     <TextBlock Text="Receive sources from this group. Empty = Public."
                                Style="{StaticResource Wd.Text.Body}"
                                FontSize="11"
@@ -550,7 +641,8 @@
                     <TextBlock Text="Output group"
                                Style="{StaticResource Wd.Text.Subtle}"
                                Margin="0,12,0,4"/>
-                    <TextBox Text="{Binding Settings.OutputGroups, UpdateSourceTrigger=PropertyChanged}"/>
+                    <TextBox Text="{Binding Settings.OutputGroups, UpdateSourceTrigger=PropertyChanged}"
+                             ToolTip="Comma-separated NDI group(s) TeamsISO's normalized ISO outputs broadcast on. Empty = Public."/>
                     <TextBlock Text="Broadcast TeamsISO outputs on this group. Empty = Public."
                                Style="{StaticResource Wd.Text.Body}"
                                FontSize="11"
@@ -593,6 +685,7 @@
 
                     <CheckBox Content="Hide my self-preview from participants"
                               IsChecked="{Binding Settings.HideLocalSelf}"
+                              ToolTip="Filters out the '(Local)' source — your own preview that Teams broadcasts on the same machine — so you don't accidentally route it as an ISO."
                               Margin="0,10,0,0"/>
 
                     <Button Style="{StaticResource Wd.Button.Primary}"
@@ -600,7 +693,8 @@
                             Command="{Binding Settings.ApplyCommand}"
                             HorizontalAlignment="Stretch"
                             Margin="0,28,0,0"
-                            Padding="0,11"/>
+                            Padding="0,11"
+                            ToolTip="Persist all settings to %APPDATA%\TeamsISO\config.json. Group changes apply on next launch."/>
                 </StackPanel>
             </ScrollViewer>
         </Border>
diff --git a/src/TeamsISO.App/TeamsISO.App.csproj b/src/TeamsISO.App/TeamsISO.App.csproj
index 62e68d9..aa79754 100644
--- a/src/TeamsISO.App/TeamsISO.App.csproj
+++ b/src/TeamsISO.App/TeamsISO.App.csproj
@@ -25,6 +25,11 @@
       from 100 (Thin) to 900 (Black) so we don't ship a directory of duplicates.
     -->
     <Resource Include="Assets\Fonts\Inter.ttf" />
+    <!--
+      JetBrains Mono Variable v2.304 (OFL). Used for machine names, source IDs,
+      and stat counters where a fixed-width font reads better than Inter.
+    -->
+    <Resource Include="Assets\Fonts\JetBrainsMono.ttf" />
   </ItemGroup>
 
 </Project>
diff --git a/src/TeamsISO.App/Themes/WildDragonTheme.xaml b/src/TeamsISO.App/Themes/WildDragonTheme.xaml
index 9282d82..e9bc0c2 100644
--- a/src/TeamsISO.App/Themes/WildDragonTheme.xaml
+++ b/src/TeamsISO.App/Themes/WildDragonTheme.xaml
@@ -76,7 +76,7 @@
         Segoe UI if the resource is somehow missing.
     -->
     <FontFamily x:Key="Wd.Font.Sans">pack://application:,,,/Assets/Fonts/#Inter, Inter, Segoe UI Variable Display, Segoe UI, sans-serif</FontFamily>
-    <FontFamily x:Key="Wd.Font.Mono">JetBrains Mono, Cascadia Mono, Consolas, monospace</FontFamily>
+    <FontFamily x:Key="Wd.Font.Mono">pack://application:,,,/Assets/Fonts/#JetBrains Mono, JetBrains Mono, Cascadia Mono, Consolas, monospace</FontFamily>
 
     <Style x:Key="Wd.Text.Title" TargetType="TextBlock">
         <Setter Property="FontFamily" Value="{StaticResource Wd.Font.Sans}"/>
diff --git a/src/TeamsISO.App/ViewModels/ParticipantViewModel.cs b/src/TeamsISO.App/ViewModels/ParticipantViewModel.cs
index a4d1d5e..7409dde 100644
--- a/src/TeamsISO.App/ViewModels/ParticipantViewModel.cs
+++ b/src/TeamsISO.App/ViewModels/ParticipantViewModel.cs
@@ -51,6 +51,15 @@ public sealed class ParticipantViewModel : ObservableObject
     /// <summary>Frames dropped by the closest-frame strategy when the receiver outpaces the processor.</summary>
     public long FramesDropped { get => _framesDropped; set => SetField(ref _framesDropped, value); }
 
+    private string _stateLabel = "—";
+    private string _stateColor = "Wd.Text.Tertiary";
+
+    /// <summary>Human-readable pipeline state ("Receiving", "Error", "—").</summary>
+    public string StateLabel { get => _stateLabel; set => SetField(ref _stateLabel, value); }
+
+    /// <summary>Resource key of the brush to color the state pill with.</summary>
+    public string StateColor { get => _stateColor; set => SetField(ref _stateColor, value); }
+
     /// <summary>Source resolution as "WxH", or em-dash when no frames have been seen yet.</summary>
     public string IncomingResolution { get => _incomingResolution; set => SetField(ref _incomingResolution, value); }
 
@@ -73,6 +82,15 @@ public sealed class ParticipantViewModel : ObservableObject
         IncomingFps = stats.IncomingFps > 0
             ? $"{stats.IncomingFps:0.0} fps"
             : "—";
+        (StateLabel, StateColor) = stats.State switch
+        {
+            IsoState.Receiving => ("LIVE", "Wd.Status.Live"),
+            IsoState.Sending   => ("LIVE", "Wd.Status.Live"),
+            IsoState.NoSignal  => ("NO SIGNAL", "Wd.Status.Warn"),
+            IsoState.Error     => ("ERROR", "Wd.Status.Error"),
+            IsoState.Idle      => (IsEnabled ? "STARTING" : "—", "Wd.Text.Tertiary"),
+            _                  => ("—", "Wd.Text.Tertiary"),
+        };
     }
 
     public bool IsProcessing
diff --git a/src/TeamsISO.Engine/Domain/IsoHealthStats.cs b/src/TeamsISO.Engine/Domain/IsoHealthStats.cs
index 84130a0..e303f69 100644
--- a/src/TeamsISO.Engine/Domain/IsoHealthStats.cs
+++ b/src/TeamsISO.Engine/Domain/IsoHealthStats.cs
@@ -12,4 +12,10 @@ public sealed record IsoHealthStats(
 {
     public static readonly IsoHealthStats Empty =
         new(0, 0, 0, 0, null, 0, 0, 0);
+
+    /// <summary>
+    /// Pipeline lifecycle state. <see cref="IsoState.Idle"/> when no pipeline is
+    /// running; otherwise reflects the supervisor's current view.
+    /// </summary>
+    public IsoState State { get; init; } = IsoState.Idle;
 }
diff --git a/src/TeamsISO.Engine/Pipeline/IsoPipeline.cs b/src/TeamsISO.Engine/Pipeline/IsoPipeline.cs
index 252c2fc..76e43bd 100644
--- a/src/TeamsISO.Engine/Pipeline/IsoPipeline.cs
+++ b/src/TeamsISO.Engine/Pipeline/IsoPipeline.cs
@@ -79,7 +79,10 @@ public sealed class IsoPipeline : IAsyncDisposable
             LastFrameAt: lastAt,
             IncomingFps: ComputeFps(),
             IncomingWidth: w,
-            IncomingHeight: h);
+            IncomingHeight: h)
+        {
+            State = State,
+        };
     }
 
     /// <summary>