.NET: Refactor harness console rendering (#5751)

* Refactor harness console rendering

* Fix formatting issues

* Address PR comments

dotnet/agent-framework-dotnet.slnx

@@ -123,6 +123,8 @@
     <Project Path="samples/02-agents/Harness/Harness_Step01_Research/Harness_Step01_Research.csproj" />
     <Project Path="samples/02-agents/Harness/Harness_Step02_Research_WithSubAgents/Harness_Step02_Research_WithSubAgents.csproj" />
     <Project Path="samples/02-agents/Harness/Harness_Step03_DataProcessing/Harness_Step03_DataProcessing.csproj" />
+    <Project Path="samples/02-agents/Harness/ConsoleReactiveFramework/ConsoleReactiveFramework.csproj" />
+    <Project Path="samples/02-agents/Harness/ConsoleReactiveComponents/ConsoleReactiveComponents.csproj" />
   </Folder>
   <Folder Name="/Samples/02-agents/AGUI/Step05_StateManagement/">
     <Project Path="samples/02-agents/AGUI/Step05_StateManagement/Client/Client.csproj" />

dotnet/samples/02-agents/Harness/ConsoleReactiveComponents/AnsiEscapes.cs

@@ -0,0 +1,90 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Harness.ConsoleReactiveComponents;
+
+/// <summary>
+/// Provides descriptive helpers for common ANSI/VT100 escape sequences used
+/// in the split-console layout (DECSTBM scroll regions, cursor movement, line erasure).
+/// </summary>
+public static class AnsiEscapes
+{
+    /// <summary>
+    /// Sets the scrollable region to rows 1 through <paramref name="bottom"/> (DECSTBM).
+    /// Content outside this region will not scroll.
+    /// </summary>
+    public static string SetScrollRegion(int bottom) => $"\x1b[1;{bottom}r";
+
+    /// <summary>
+    /// Resets the scroll region to the full terminal height (DECSTBM reset).
+    /// </summary>
+    public static string ResetScrollRegion => "\x1b[r";
+
+    /// <summary>
+    /// Moves the cursor to the specified 1-based <paramref name="row"/> and <paramref name="column"/> (CUP).
+    /// </summary>
+    public static string MoveCursor(int row, int column) => $"\x1b[{row};{column}H";
+
+    /// <summary>
+    /// Erases the entire current line (EL 2).
+    /// </summary>
+    public static string EraseEntireLine => "\x1b[2K";
+
+    /// <summary>
+    /// Erases the entire screen.
+    /// </summary>
+    public static string EraseEntireScreen => "\x1b[2J";
+
+    /// <summary>
+    /// Erases the scrollback buffer (ESC[3J). Use alongside <see cref="EraseEntireScreen"/>
+    /// to fully clear both the visible screen and the scroll history.
+    /// </summary>
+    public static string EraseScrollbackBuffer => "\x1b[3J";
+
+    /// <summary>
+    /// Saves the current cursor position (DECSC / SCP).
+    /// Note: most terminals have a single save slot — nested saves are not supported.
+    /// </summary>
+    public static string SaveCursor => "\x1b[s";
+
+    /// <summary>
+    /// Restores the previously saved cursor position (DECRC / RCP).
+    /// </summary>
+    public static string RestoreCursor => "\x1b[u";
+
+    /// <summary>
+    /// Moves the cursor to the specified 1-based <paramref name="row"/> at column 1, then erases the entire line.
+    /// Convenience combination of <see cref="MoveCursor"/> and <see cref="EraseEntireLine"/>.
+    /// </summary>
+    public static string MoveAndEraseLine(int row) => $"\x1b[{row};1H\x1b[2K";
+
+    /// <summary>
+    /// Sets the foreground text color using a <see cref="ConsoleColor"/> value.
+    /// </summary>
+    public static string SetForegroundColor(ConsoleColor color) => $"\x1b[{ConsoleColorToAnsi(color)}m";
+
+    /// <summary>
+    /// Resets all text attributes (color, bold, etc.) to their defaults.
+    /// </summary>
+    public static string ResetAttributes => "\x1b[0m";
+
+    private static int ConsoleColorToAnsi(ConsoleColor color) => color switch
+    {
+        ConsoleColor.Black => 30,
+        ConsoleColor.DarkRed => 31,
+        ConsoleColor.DarkGreen => 32,
+        ConsoleColor.DarkYellow => 33,
+        ConsoleColor.DarkBlue => 34,
+        ConsoleColor.DarkMagenta => 35,
+        ConsoleColor.DarkCyan => 36,
+        ConsoleColor.Gray => 37,
+        ConsoleColor.DarkGray => 90,
+        ConsoleColor.Red => 91,
+        ConsoleColor.Green => 92,
+        ConsoleColor.Yellow => 93,
+        ConsoleColor.Blue => 94,
+        ConsoleColor.Magenta => 95,
+        ConsoleColor.Cyan => 96,
+        ConsoleColor.White => 97,
+        _ => 37
+    };
+}

dotnet/samples/02-agents/Harness/ConsoleReactiveComponents/ConsoleReactiveComponents.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="../ConsoleReactiveFramework/ConsoleReactiveFramework.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/02-agents/Harness/ConsoleReactiveComponents/ListSelection.cs

@@ -0,0 +1,151 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveFramework;
+
+namespace Harness.ConsoleReactiveComponents;
+
+/// <summary>
+/// A component that renders a selectable list of items with a cursor indicator.
+/// The selected item is indicated with a "&gt;" prefix and rendered in the highlight color.
+/// Optionally includes a title above the list and a custom text input option at the bottom.
+/// </summary>
+public class ListSelection : ConsoleReactiveComponent<ListSelectionProps, ConsoleReactiveState>
+{
+    /// <summary>
+    /// Calculates the height (in rows) required to render the list,
+    /// including the optional title and custom text input row.
+    /// </summary>
+    /// <param name="props">The list selection props.</param>
+    /// <returns>The number of rows needed.</returns>
+    public static int CalculateHeight(ListSelectionProps props)
+    {
+        int height = props.Items.Count;
+        if (props.CustomTextPlaceholder != null)
+        {
+            height++;
+        }
+
+        height += GetTitleLineCount(props.Title);
+        return height;
+    }
+
+    /// <inheritdoc />
+    public override void RenderCore(ListSelectionProps props, ConsoleReactiveState state)
+    {
+        int row = 0;
+
+        // Render the title lines (if any)
+        if (props.Title is not null)
+        {
+            foreach (string line in props.Title.Split('\n'))
+            {
+                Console.Write(AnsiEscapes.MoveCursor(this.Y + row, this.X));
+                Console.Write(AnsiEscapes.EraseEntireLine);
+                Console.Write(line);
+                row++;
+            }
+        }
+
+        // Render the list items + optional custom text row
+        int totalItems = props.Items.Count + (props.CustomTextPlaceholder != null ? 1 : 0);
+
+        for (int i = 0; i < totalItems; i++)
+        {
+            Console.Write(AnsiEscapes.MoveCursor(this.Y + row, this.X));
+            Console.Write(AnsiEscapes.EraseEntireLine);
+
+            bool isSelected = i == props.SelectedIndex;
+            bool isCustomTextOption = props.CustomTextPlaceholder != null && i == props.Items.Count;
+
+            // Cursor indicator
+            Console.Write(isSelected ? "> " : "  ");
+
+            if (isCustomTextOption)
+            {
+                this.RenderCustomTextOption(props, isSelected);
+            }
+            else
+            {
+                if (isSelected)
+                {
+                    Console.Write(AnsiEscapes.SetForegroundColor(props.HighlightColor));
+                }
+
+                Console.Write(props.Items[i]);
+
+                if (isSelected)
+                {
+                    Console.Write(AnsiEscapes.ResetAttributes);
+                }
+            }
+
+            Console.WriteLine();
+            row++;
+        }
+    }
+
+    /// <summary>
+    /// Gets the number of lines the title occupies, or 0 if no title is set.
+    /// </summary>
+    private static int GetTitleLineCount(string? title) =>
+        title is null ? 0 : title.Split('\n').Length;
+
+    private void RenderCustomTextOption(ListSelectionProps props, bool isSelected)
+    {
+        if (props.CustomText.Length > 0)
+        {
+            // User has typed text — render in highlight color if selected
+            if (isSelected)
+            {
+                Console.Write(AnsiEscapes.SetForegroundColor(props.HighlightColor));
+            }
+
+            Console.Write(props.CustomText);
+
+            if (isSelected)
+            {
+                Console.Write(AnsiEscapes.ResetAttributes);
+            }
+        }
+        else if (!string.IsNullOrWhiteSpace(props.CustomTextPlaceholder))
+        {
+            // No text — show placeholder in dark grey (or highlight color if selected)
+            if (isSelected)
+            {
+                Console.Write(AnsiEscapes.SetForegroundColor(props.HighlightColor));
+            }
+            else
+            {
+                Console.Write(AnsiEscapes.SetForegroundColor(ConsoleColor.DarkGray));
+            }
+
+            Console.Write(" ");
+            Console.Write(props.CustomTextPlaceholder);
+            Console.Write(AnsiEscapes.ResetAttributes);
+        }
+    }
+}
+
+/// <summary>
+/// Props for <see cref="ListSelection"/>.
+/// </summary>
+public record ListSelectionProps : ConsoleReactiveProps
+{
+    /// <summary>Gets the title text displayed above the list items. May contain newlines for multi-line titles.</summary>
+    public string? Title { get; init; }
+
+    /// <summary>Gets the items to display in the list.</summary>
+    public IReadOnlyList<string> Items { get; init; } = Array.Empty<string>();
+
+    /// <summary>Gets the zero-based index of the currently selected item.</summary>
+    public int SelectedIndex { get; init; }
+
+    /// <summary>Gets the highlight color for the active item. Defaults to <see cref="ConsoleColor.Cyan"/>.</summary>
+    public ConsoleColor HighlightColor { get; init; } = ConsoleColor.Cyan;
+
+    /// <summary>Gets the placeholder text for the custom text input option. If <c>null</c>, no custom option is shown.</summary>
+    public string? CustomTextPlaceholder { get; init; }
+
+    /// <summary>Gets the text being typed into the custom text input option.</summary>
+    public string CustomText { get; init; } = "";
+}

dotnet/samples/02-agents/Harness/ConsoleReactiveComponents/TextInput.cs

@@ -0,0 +1,101 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveFramework;
+
+namespace Harness.ConsoleReactiveComponents;
+
+/// <summary>
+/// Props for <see cref="TextInput"/>.
+/// </summary>
+public record TextInputProps : ConsoleReactiveProps
+{
+    /// <summary>Gets the prompt string displayed on the left (e.g. "&gt; " or "user &gt; ").</summary>
+    public string Prompt { get; init; } = "> ";
+
+    /// <summary>Gets the text content to render to the right of the prompt.</summary>
+    public string Text { get; init; } = "";
+
+    /// <summary>Gets the placeholder text shown in dark grey when <see cref="Text"/> is empty.</summary>
+    public string Placeholder { get; init; } = "";
+}
+
+/// <summary>
+/// A component that renders a prompt with text input. Supports multi-line text
+/// where continuation lines are indented to align with the text start position
+/// (i.e. the column after the prompt).
+/// </summary>
+public class TextInput : ConsoleReactiveComponent<TextInputProps, ConsoleReactiveState>
+{
+    /// <summary>
+    /// Calculates the height (in rows) required to render the prompt and text
+    /// given the available width.
+    /// </summary>
+    /// <param name="props">The text input props.</param>
+    /// <param name="availableWidth">The total available width in columns.</param>
+    /// <returns>The number of rows needed.</returns>
+    public static int CalculateHeight(TextInputProps props, int availableWidth)
+    {
+        int promptLength = props.Prompt.Length;
+        int textWidth = availableWidth - promptLength;
+
+        if (textWidth <= 0 || props.Text.Length == 0)
+        {
+            return 1;
+        }
+
+        int lines = 1;
+        int remaining = props.Text.Length - textWidth;
+        while (remaining > 0)
+        {
+            lines++;
+            remaining -= textWidth;
+        }
+
+        return lines;
+    }
+
+    /// <inheritdoc />
+    public override void RenderCore(TextInputProps props, ConsoleReactiveState state)
+    {
+        int promptLength = props.Prompt.Length;
+        int textWidth = this.Width - promptLength;
+        string indent = new(' ', promptLength);
+
+        // First line: prompt + start of text
+        Console.Write(AnsiEscapes.MoveCursor(this.Y, this.X));
+        Console.Write(AnsiEscapes.EraseEntireLine);
+        Console.Write(props.Prompt);
+
+        if (textWidth <= 0 || props.Text.Length == 0)
+        {
+            // Show placeholder if text is empty
+            if (props.Text.Length == 0 && props.Placeholder.Length > 0 && textWidth > 0)
+            {
+                Console.Write(AnsiEscapes.SetForegroundColor(ConsoleColor.DarkGray));
+                Console.Write(" ");
+                Console.Write(props.Placeholder[..Math.Min(props.Placeholder.Length, textWidth - 1)]);
+                Console.Write(AnsiEscapes.ResetAttributes);
+            }
+
+            return;
+        }
+
+        int offset = 0;
+        int firstChunk = Math.Min(textWidth, props.Text.Length);
+        Console.Write(props.Text[offset..firstChunk]);
+        offset = firstChunk;
+
+        // Continuation lines: indented to align with text start
+        int row = 1;
+        while (offset < props.Text.Length)
+        {
+            int chunk = Math.Min(textWidth, props.Text.Length - offset);
+            Console.Write(AnsiEscapes.MoveCursor(this.Y + row, this.X));
+            Console.Write(AnsiEscapes.EraseEntireLine);
+            Console.Write(indent);
+            Console.Write(props.Text[offset..(offset + chunk)]);
+            offset += chunk;
+            row++;
+        }
+    }
+}

dotnet/samples/02-agents/Harness/ConsoleReactiveComponents/TextPanel.cs

@@ -0,0 +1,106 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveFramework;
+
+namespace Harness.ConsoleReactiveComponents;
+
+/// <summary>
+/// Props for <see cref="TextPanel"/>.
+/// </summary>
+public record TextPanelProps : ConsoleReactiveProps
+{
+    /// <summary>Gets the items to render in the panel.</summary>
+    public IReadOnlyList<object> Items { get; init; } = [];
+}
+
+/// <summary>
+/// A component that renders a list of items vertically using a custom render delegate.
+/// Designed for rendering dynamic items in a non-scroll region that may be
+/// re-rendered on each update. If the component's <see cref="ConsoleReactiveComponent.Height"/>
+/// exceeds the number of output lines, leftover lines are erased.
+/// </summary>
+public class TextPanel : ConsoleReactiveComponent<TextPanelProps, ConsoleReactiveState>
+{
+    private readonly Func<object, string> _renderItem;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="TextPanel"/> class.
+    /// </summary>
+    /// <param name="renderItem">A delegate that renders an item and returns the text to display (may contain newlines).</param>
+    public TextPanel(Func<object, string> renderItem)
+    {
+        this._renderItem = renderItem;
+    }
+
+    /// <summary>
+    /// Calculates the height (in lines) needed to render all items.
+    /// </summary>
+    /// <param name="items">The items to measure.</param>
+    /// <param name="renderItem">The render delegate to use for measuring.</param>
+    /// <returns>The total number of lines all items will occupy.</returns>
+    public static int CalculateHeight(IReadOnlyList<object> items, Func<object, string> renderItem)
+    {
+        int total = 0;
+        for (int i = 0; i < items.Count; i++)
+        {
+            string text = renderItem(items[i]);
+            total += CountLines(text);
+        }
+
+        return total;
+    }
+
+    /// <inheritdoc />
+    public override void RenderCore(TextPanelProps props, ConsoleReactiveState state)
+    {
+        int currentRow = 0;
+
+        for (int i = 0; i < props.Items.Count; i++)
+        {
+            string text = this._renderItem(props.Items[i]);
+            string[] lines = text.Split('\n');
+            int lineCount = CountLines(text);
+
+            for (int j = 0; j < lineCount; j++)
+            {
+                Console.Write(AnsiEscapes.MoveAndEraseLine(this.Y + currentRow));
+                Console.Write(lines[j]);
+                currentRow++;
+            }
+        }
+
+        // If the component height exceeds the output, erase leftover lines
+        if (this.Height > currentRow)
+        {
+            for (int i = currentRow; i < this.Height; i++)
+            {
+                Console.Write(AnsiEscapes.MoveAndEraseLine(this.Y + i));
+            }
+        }
+    }
+
+    private static int CountLines(string text)
+    {
+        if (string.IsNullOrEmpty(text))
+        {
+            return 0;
+        }
+
+        int count = 1;
+        for (int i = 0; i < text.Length; i++)
+        {
+            if (text[i] == '\n')
+            {
+                count++;
+            }
+        }
+
+        // If text ends with a newline, don't count the trailing empty line
+        if (text[text.Length - 1] == '\n')
+        {
+            count--;
+        }
+
+        return count;
+    }
+}

dotnet/samples/02-agents/Harness/ConsoleReactiveComponents/TextScrollPanel.cs

@@ -0,0 +1,70 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveFramework;
+
+namespace Harness.ConsoleReactiveComponents;
+
+/// <summary>
+/// Props for <see cref="TextScrollPanel"/>.
+/// </summary>
+public record TextScrollPanelProps : ConsoleReactiveProps
+{
+    /// <summary>Gets the items to render in the scroll panel.</summary>
+    public IReadOnlyList<object> Items { get; init; } = [];
+}
+
+/// <summary>
+/// State for <see cref="TextScrollPanel"/>.
+/// </summary>
+/// <param name="RenderedCount">The number of items already rendered.</param>
+public record TextScrollPanelState(int RenderedCount = 0) : ConsoleReactiveState;
+
+/// <summary>
+/// A component that renders items within a scroll area using a custom render delegate.
+/// All items are considered finalized — only new items since the last render are output.
+/// Use <see cref="Reset"/> to force a full re-render.
+/// </summary>
+public class TextScrollPanel : ConsoleReactiveComponent<TextScrollPanelProps, TextScrollPanelState>
+{
+    private readonly Func<object, string> _renderItem;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="TextScrollPanel"/> class.
+    /// </summary>
+    /// <param name="renderItem">A delegate that renders a single item and returns the text to display (may contain newlines).</param>
+    public TextScrollPanel(Func<object, string> renderItem)
+    {
+        this._renderItem = renderItem;
+        this.State = new TextScrollPanelState();
+    }
+
+    /// <summary>
+    /// Resets the panel so all items will be re-rendered on the next Render call.
+    /// </summary>
+    public void Reset()
+    {
+        this.State = new TextScrollPanelState();
+    }
+
+    /// <inheritdoc />
+    public override void RenderCore(TextScrollPanelProps props, TextScrollPanelState state)
+    {
+        if (props.Items.Count == 0)
+        {
+            return;
+        }
+
+        // Move cursor to the bottom of the scroll area
+        Console.Write(AnsiEscapes.MoveCursor(this.Y + this.Height - 1, this.X));
+
+        // Output only new items since last rendered
+        for (int i = state.RenderedCount; i < props.Items.Count; i++)
+        {
+            string text = this._renderItem(props.Items[i]);
+            Console.Write(text);
+        }
+
+        // Update state to track what we've rendered
+        this.State = new TextScrollPanelState(props.Items.Count);
+    }
+}

dotnet/samples/02-agents/Harness/ConsoleReactiveComponents/TopBottomRule.cs

@@ -0,0 +1,87 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveFramework;
+
+namespace Harness.ConsoleReactiveComponents;
+
+/// <summary>
+/// Props for <see cref="TopBottomRule"/>.
+/// </summary>
+public record TopBottomRuleProps : ConsoleReactiveProps
+{
+    /// <summary>Gets the width of the horizontal rules in characters.</summary>
+    public int Width { get; init; }
+
+    /// <summary>Gets the foreground color of the horizontal rules. If <c>null</c>, the default terminal color is used.</summary>
+    public ConsoleColor? Color { get; init; }
+}
+
+/// <summary>
+/// A component that renders a top and bottom horizontal rule (─) with children
+/// stacked vertically between them.
+/// </summary>
+public class TopBottomRule : ConsoleReactiveComponent<TopBottomRuleProps, ConsoleReactiveState>
+{
+    /// <summary>
+    /// Calculates the total height including the top rule, children, and bottom rule.
+    /// </summary>
+    /// <param name="props">The component props containing children.</param>
+    /// <returns>2 (for the rules) plus the sum of all children heights.</returns>
+    public static int CalculateHeight(TopBottomRuleProps props)
+    {
+        int childrenHeight = 0;
+        foreach (var child in props.Children)
+        {
+            childrenHeight += child.Height;
+        }
+
+        // Top rule + children + bottom rule
+        return 2 + childrenHeight;
+    }
+
+    /// <inheritdoc />
+    public override void RenderCore(TopBottomRuleProps props, ConsoleReactiveState state)
+    {
+        int ruleWidth = props.Width;
+        string rule = new('─', ruleWidth);
+
+        if (props.Color.HasValue)
+        {
+            Console.Write(AnsiEscapes.SetForegroundColor(props.Color.Value));
+        }
+
+        // Top rule
+        Console.Write(AnsiEscapes.MoveCursor(this.Y, this.X));
+        Console.Write(rule);
+
+        // Render children stacked below the top rule
+        int currentY = this.Y + 1;
+
+        if (props.Color.HasValue)
+        {
+            Console.Write(AnsiEscapes.ResetAttributes);
+        }
+
+        foreach (var child in props.Children)
+        {
+            child.X = this.X;
+            child.Y = currentY;
+            child.Render();
+            currentY += child.Height;
+        }
+
+        if (props.Color.HasValue)
+        {
+            Console.Write(AnsiEscapes.SetForegroundColor(props.Color.Value));
+        }
+
+        // Bottom rule
+        Console.Write(AnsiEscapes.MoveCursor(currentY, this.X));
+        Console.Write(rule);
+
+        if (props.Color.HasValue)
+        {
+            Console.Write(AnsiEscapes.ResetAttributes);
+        }
+    }
+}

dotnet/samples/02-agents/Harness/ConsoleReactiveFramework/ConsoleReactiveComponent.cs

@@ -0,0 +1,110 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Harness.ConsoleReactiveFramework;
+
+/// <summary>
+/// Abstract base class for all console UI components. Provides layout properties
+/// (position and size) and a <see cref="Render"/> method for drawing to the console.
+/// Derive from <see cref="ConsoleReactiveComponent{TProps, TState}"/> instead of this class directly.
+/// </summary>
+public abstract class ConsoleReactiveComponent
+{
+    internal ConsoleReactiveComponent()
+    {
+    }
+
+    /// <summary>Gets or sets the 1-based column position of the component.</summary>
+    public int X { get; set; }
+
+    /// <summary>Gets or sets the 1-based row position of the component.</summary>
+    public int Y { get; set; }
+
+    /// <summary>Gets or sets the width of the component in columns.</summary>
+    public int Width { get; set; }
+
+    /// <summary>Gets or sets the height of the component in rows.</summary>
+    public int Height { get; set; }
+
+    /// <summary>Renders the component to the console at its current position.</summary>
+    public abstract void Render();
+}
+
+/// <summary>
+/// Generic base class for console UI components with typed props and state.
+/// Props represent externally supplied configuration; state represents internal mutable data.
+/// </summary>
+/// <typeparam name="TProps">The type of the component's props (external configuration).</typeparam>
+/// <typeparam name="TState">The type of the component's internal state.</typeparam>
+public abstract class ConsoleReactiveComponent<TProps, TState> : ConsoleReactiveComponent
+    where TProps : ConsoleReactiveProps
+    where TState : ConsoleReactiveState
+{
+    private readonly object _renderLock = new();
+    private TProps? _lastRenderedProps;
+    private TState? _lastRenderedState;
+
+    /// <summary>Gets or sets the component's props (external configuration).</summary>
+    public TProps? Props { get; set; }
+
+    /// <summary>Gets or sets the component's internal state.</summary>
+    protected TState? State { get; set; }
+
+    /// <summary>
+    /// Updates the component's state and triggers a re-render.
+    /// </summary>
+    /// <param name="newState">The new state value.</param>
+    public void SetState(TState newState)
+    {
+        this.State = newState;
+        this.Render();
+    }
+
+    /// <summary>
+    /// Renders the component using the current props and state.
+    /// Uses a lock to prevent concurrent renders from multiple sources.
+    /// Skips rendering if neither props nor state have changed since the last render.
+    /// </summary>
+    public override void Render()
+    {
+        lock (this._renderLock)
+        {
+            if (this.Props is null)
+            {
+                return;
+            }
+
+            if (ReferenceEquals(this.Props, this._lastRenderedProps)
+                && ReferenceEquals(this.State, this._lastRenderedState))
+            {
+                return;
+            }
+
+            this.RenderCore(this.Props, this.State!);
+
+            this._lastRenderedProps = this.Props;
+            this._lastRenderedState = this.State;
+        }
+    }
+
+    /// <summary>
+    /// Called by <see cref="Render"/> to perform the actual rendering. Override this in derived classes.
+    /// </summary>
+    /// <param name="props">The current props.</param>
+    /// <param name="state">The current state.</param>
+    public abstract void RenderCore(TProps props, TState state);
+}
+
+/// <summary>
+/// Base record for component props. Provides an optional <see cref="Children"/> collection
+/// for composing child components.
+/// </summary>
+public record ConsoleReactiveProps
+{
+    /// <summary>Gets the child components to render within this component.</summary>
+    public IReadOnlyList<ConsoleReactiveComponent> Children { get; init; } = [];
+}
+
+/// <summary>
+/// Base record for component state.
+/// </summary>
+public record ConsoleReactiveState;

dotnet/samples/02-agents/Harness/ConsoleReactiveFramework/ConsoleReactiveFramework.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+</Project>

dotnet/samples/02-agents/Harness/ConsoleReactiveFramework/ConsoleResizeListener.cs

@@ -0,0 +1,83 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Harness.ConsoleReactiveFramework;
+
+/// <summary>
+/// Event args for console resize events, containing the old and new dimensions.
+/// </summary>
+public class ConsoleResizeEventArgs : EventArgs
+{
+    /// <summary>Gets the previous console width.</summary>
+    public int OldWidth { get; }
+
+    /// <summary>Gets the previous console height.</summary>
+    public int OldHeight { get; }
+
+    /// <summary>Gets the new console width.</summary>
+    public int NewWidth { get; }
+
+    /// <summary>Gets the new console height.</summary>
+    public int NewHeight { get; }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="ConsoleResizeEventArgs"/> class.
+    /// </summary>
+    /// <param name="oldWidth">The previous width.</param>
+    /// <param name="oldHeight">The previous height.</param>
+    /// <param name="newWidth">The new width.</param>
+    /// <param name="newHeight">The new height.</param>
+    public ConsoleResizeEventArgs(int oldWidth, int oldHeight, int newWidth, int newHeight)
+    {
+        this.OldWidth = oldWidth;
+        this.OldHeight = oldHeight;
+        this.NewWidth = newWidth;
+        this.NewHeight = newHeight;
+    }
+}
+
+/// <summary>
+/// Singleton that polls console dimensions every 16ms and raises the
+/// <see cref="ConsoleResized"/> event when the window size changes.
+/// </summary>
+public sealed class ConsoleResizeListener
+{
+#pragma warning disable IDE0052 // Remove unread private members
+    private readonly Task _task;
+#pragma warning restore IDE0052 // Remove unread private members
+
+    private int _lastWidth;
+    private int _lastHeight;
+
+    private ConsoleResizeListener()
+    {
+        this._lastWidth = Console.WindowWidth;
+        this._lastHeight = Console.WindowHeight;
+        this._task = this.ListenForResizeAsync();
+    }
+
+    /// <summary>Gets the singleton instance of <see cref="ConsoleResizeListener"/>.</summary>
+    public static ConsoleResizeListener Instance { get; } = new ConsoleResizeListener();
+
+    /// <summary>Raised when the console window is resized.</summary>
+    public event EventHandler<ConsoleResizeEventArgs>? ConsoleResized;
+
+    private async Task ListenForResizeAsync()
+    {
+        while (true)
+        {
+            int currentWidth = Console.WindowWidth;
+            int currentHeight = Console.WindowHeight;
+
+            if (currentWidth != this._lastWidth || currentHeight != this._lastHeight)
+            {
+                int oldWidth = this._lastWidth;
+                int oldHeight = this._lastHeight;
+                this._lastWidth = currentWidth;
+                this._lastHeight = currentHeight;
+                this.ConsoleResized?.Invoke(this, new ConsoleResizeEventArgs(oldWidth, oldHeight, currentWidth, currentHeight));
+            }
+
+            await Task.Delay(16);
+        }
+    }
+}

dotnet/samples/02-agents/Harness/ConsoleReactiveFramework/KeyEventListener.cs

@@ -0,0 +1,57 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Harness.ConsoleReactiveFramework;
+
+/// <summary>
+/// Event args for key press events, wrapping a <see cref="ConsoleKeyInfo"/>.
+/// </summary>
+public class KeyPressEventArgs : EventArgs
+{
+    /// <summary>Gets the key information for the pressed key.</summary>
+    public ConsoleKeyInfo KeyInfo { get; }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="KeyPressEventArgs"/> class.
+    /// </summary>
+    /// <param name="keyInfo">The key information.</param>
+    public KeyPressEventArgs(ConsoleKeyInfo keyInfo)
+    {
+        this.KeyInfo = keyInfo;
+    }
+}
+
+/// <summary>
+/// Singleton that polls for console key presses every 16ms and raises the
+/// <see cref="KeyPressed"/> event when a key is detected.
+/// </summary>
+public sealed class KeyEventListener
+{
+#pragma warning disable IDE0052 // Remove unread private members
+    private readonly Task _task;
+#pragma warning restore IDE0052 // Remove unread private members
+
+    private KeyEventListener()
+    {
+        this._task = this.ListenForKeyPressesAsync();
+    }
+
+    /// <summary>Gets the singleton instance of <see cref="KeyEventListener"/>.</summary>
+    public static KeyEventListener Instance { get; } = new KeyEventListener();
+
+    /// <summary>Raised when a key is pressed in the console.</summary>
+    public event EventHandler<KeyPressEventArgs>? KeyPressed;
+
+    private async Task ListenForKeyPressesAsync()
+    {
+        while (true)
+        {
+            while (Console.KeyAvailable)
+            {
+                var keyInfo = Console.ReadKey(intercept: true);
+                this.KeyPressed?.Invoke(this, new KeyPressEventArgs(keyInfo));
+            }
+
+            await Task.Delay(16);
+        }
+    }
+}

dotnet/samples/02-agents/Harness/Harness_ConsoleSandbox/AppComponent.cs

@@ -0,0 +1,315 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveComponents;
+using Harness.ConsoleReactiveFramework;
+
+namespace Harness.ConsoleSandbox;
+
+/// <summary>
+/// Determines which component is shown in the bottom panel.
+/// </summary>
+public enum BottomPanelMode
+{
+    /// <summary>Show the list selection component.</summary>
+    ListSelection,
+
+    /// <summary>Show the text input component.</summary>
+    TextInput
+}
+
+public record AppComponentProps : ConsoleReactiveProps
+{
+    public IReadOnlyList<string> Items { get; init; } = Array.Empty<string>();
+    public IReadOnlyList<object> ScrollItems { get; init; } = [];
+
+    /// <summary>Gets the bottom panel mode.</summary>
+    public BottomPanelMode Mode { get; init; } = BottomPanelMode.ListSelection;
+
+    /// <summary>Gets the prompt string for text input mode.</summary>
+    public string Prompt { get; init; } = "> ";
+
+    /// <summary>Gets the placeholder text shown when the input is empty.</summary>
+    public string Placeholder { get; init; } = "";
+
+    /// <summary>Gets the highlight color for the active list item. Defaults to <see cref="ConsoleColor.Cyan"/>.</summary>
+    public ConsoleColor ListHighlightColor { get; init; } = ConsoleColor.Cyan;
+
+    /// <summary>Gets the placeholder text for the custom text input option in the list. If <c>null</c>, no custom option is shown.</summary>
+    public string? ListCustomTextPlaceholder { get; init; }
+
+    /// <summary>Gets the foreground color for the rule borders. If <c>null</c>, uses the default terminal color.</summary>
+    public ConsoleColor? RuleColor { get; init; }
+}
+
+/// <summary>
+/// Internal state for the <see cref="AppComponent"/>.
+/// </summary>
+public record AppComponentState : ConsoleReactiveState
+{
+    /// <summary>Gets the selected index in list selection mode.</summary>
+    public int SelectedIndex { get; init; }
+
+    /// <summary>Gets the current input text being typed in text input mode.</summary>
+    public string InputText { get; init; } = "";
+
+    /// <summary>Gets the current text being typed into the list's custom text option.</summary>
+    public string ListInputText { get; init; } = "";
+}
+
+public class AppComponent : ConsoleReactiveComponent<AppComponentProps, AppComponentState>
+{
+    private readonly TopBottomRule _rule = new();
+    private readonly ListSelection _listSelection = new();
+    private readonly TextInput _textInput = new();
+    private readonly TextScrollPanel _textScrollPanel;
+    private readonly TextPanel _textPanel;
+    private readonly Func<object, string> _renderItem;
+    private readonly Action<string> _onTextInputSubmit;
+    private readonly Action<string> _onListInputSubmit;
+    private bool _resizedSinceLastRender;
+    private int _lastScrollBottom;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AppComponent"/> class.
+    /// </summary>
+    /// <param name="renderScrollItem">A delegate that renders a single scroll panel item and returns the text to display.</param>
+    /// <param name="onTextInputSubmit">A callback invoked with the input text when the user presses Enter in text input mode.</param>
+    /// <param name="onListInputSubmit">A callback invoked with the selected or typed text when the user presses Enter in list selection mode.</param>
+    public AppComponent(Func<object, string> renderScrollItem, Action<string> onTextInputSubmit, Action<string> onListInputSubmit)
+    {
+        this._renderItem = renderScrollItem;
+        this._onTextInputSubmit = onTextInputSubmit;
+        this._onListInputSubmit = onListInputSubmit;
+        this._textScrollPanel = new TextScrollPanel(renderScrollItem);
+        this._textPanel = new TextPanel(renderScrollItem);
+        this.State = new AppComponentState();
+        KeyEventListener.Instance.KeyPressed += this.OnKeyPressed;
+        ConsoleResizeListener.Instance.ConsoleResized += this.OnConsoleResized;
+    }
+
+    private void OnKeyPressed(object? sender, KeyPressEventArgs e)
+    {
+        if (this.Props!.Mode == BottomPanelMode.TextInput)
+        {
+            this.HandleTextInputKey(e);
+        }
+        else
+        {
+            this.HandleListSelectionKey(e);
+        }
+    }
+
+    private void HandleTextInputKey(KeyPressEventArgs e)
+    {
+        if (e.KeyInfo.Key == ConsoleKey.Enter)
+        {
+            string text = this.State!.InputText;
+            this.SetState(this.State with { InputText = "" });
+            this._onTextInputSubmit(text);
+        }
+        else if (e.KeyInfo.Key == ConsoleKey.Backspace)
+        {
+            if (this.State!.InputText.Length > 0)
+            {
+                this.SetState(this.State with { InputText = this.State.InputText[..^1] });
+            }
+        }
+        else if (e.KeyInfo.KeyChar != '\0' && !char.IsControl(e.KeyInfo.KeyChar))
+        {
+            this.SetState(this.State! with { InputText = this.State.InputText + e.KeyInfo.KeyChar });
+        }
+    }
+
+    private void HandleListSelectionKey(KeyPressEventArgs e)
+    {
+        int maxIndex = this.Props!.Items.Count - 1;
+        if (this.Props.ListCustomTextPlaceholder != null)
+        {
+            maxIndex = this.Props.Items.Count; // extra option at the end
+        }
+
+        bool isOnCustomTextOption = this.Props.ListCustomTextPlaceholder != null
+            && this.State!.SelectedIndex == this.Props.Items.Count;
+
+        if (e.KeyInfo.Key == ConsoleKey.UpArrow)
+        {
+            this.SetState(this.State! with { SelectedIndex = Math.Max(0, this.State.SelectedIndex - 1) });
+        }
+        else if (e.KeyInfo.Key == ConsoleKey.DownArrow)
+        {
+            this.SetState(this.State! with { SelectedIndex = Math.Min(maxIndex, this.State.SelectedIndex + 1) });
+        }
+        else if (e.KeyInfo.Key == ConsoleKey.Enter)
+        {
+            if (isOnCustomTextOption)
+            {
+                string text = this.State!.ListInputText;
+                this.SetState(this.State with { ListInputText = "" });
+                this._onListInputSubmit(text);
+            }
+            else
+            {
+                this._onListInputSubmit(this.Props.Items[this.State!.SelectedIndex]);
+            }
+        }
+        else if (isOnCustomTextOption)
+        {
+            // Typing only works when on the custom text option
+            if (e.KeyInfo.Key == ConsoleKey.Backspace)
+            {
+                if (this.State!.ListInputText.Length > 0)
+                {
+                    this.SetState(this.State with { ListInputText = this.State.ListInputText[..^1] });
+                }
+            }
+            else if (e.KeyInfo.KeyChar != '\0' && !char.IsControl(e.KeyInfo.KeyChar))
+            {
+                this.SetState(this.State! with { ListInputText = this.State.ListInputText + e.KeyInfo.KeyChar });
+            }
+        }
+    }
+
+    private void OnConsoleResized(object? sender, ConsoleResizeEventArgs e)
+    {
+        this._resizedSinceLastRender = true;
+        this.Render();
+    }
+
+    public override void RenderCore(AppComponentProps props, AppComponentState state)
+    {
+        // Determine the text panel height for the last scroll item
+        object? lastItem = props.ScrollItems.Count > 0 ? props.ScrollItems[^1] : null;
+        IReadOnlyList<object> lastItems = lastItem != null ? [lastItem] : [];
+        int textPanelHeight = TextPanel.CalculateHeight(lastItems, this._renderItem);
+        if (textPanelHeight > 0)
+        {
+            textPanelHeight++; // Extra line for spacing between text panel and rule
+        }
+
+        // Build the bottom panel child based on mode
+        ConsoleReactiveComponent bottomChild;
+        int bottomChildHeight;
+
+        if (props.Mode == BottomPanelMode.TextInput)
+        {
+            var textInputProps = new TextInputProps
+            {
+                Prompt = props.Prompt,
+                Text = state.InputText,
+                Placeholder = props.Placeholder
+            };
+
+            bottomChildHeight = TextInput.CalculateHeight(textInputProps, Console.WindowWidth);
+            this._textInput.Width = Console.WindowWidth;
+            this._textInput.Height = bottomChildHeight;
+            this._textInput.Props = textInputProps;
+            bottomChild = this._textInput;
+        }
+        else
+        {
+            var listProps = new ListSelectionProps
+            {
+                Items = props.Items,
+                SelectedIndex = state.SelectedIndex,
+                HighlightColor = props.ListHighlightColor,
+                CustomTextPlaceholder = props.ListCustomTextPlaceholder,
+                CustomText = state.ListInputText
+            };
+
+            bottomChildHeight = ListSelection.CalculateHeight(listProps);
+            this._listSelection.Height = bottomChildHeight;
+            this._listSelection.Props = listProps;
+            bottomChild = this._listSelection;
+        }
+
+        var ruleProps = new TopBottomRuleProps
+        {
+            Width = Console.WindowWidth,
+            Color = props.RuleColor,
+            Children = [bottomChild]
+        };
+
+        int ruleHeight = TopBottomRule.CalculateHeight(ruleProps);
+        int scrollBottom = Console.WindowHeight - ruleHeight - textPanelHeight;
+
+        // If scroll region changed or a clear is needed, reset everything
+        if (this._resizedSinceLastRender || (this._lastScrollBottom != 0 && scrollBottom != this._lastScrollBottom))
+        {
+            Console.Write(AnsiEscapes.EraseEntireScreen);
+            Console.Write(AnsiEscapes.EraseScrollbackBuffer);
+            this._textScrollPanel.Reset();
+            this._resizedSinceLastRender = false;
+        }
+
+        this._lastScrollBottom = scrollBottom;
+
+        Console.Write(AnsiEscapes.SetScrollRegion(scrollBottom));
+
+        // Render text scroll panel in the scroll area (all items except the last)
+        IReadOnlyList<object> scrollItems = props.ScrollItems.Count > 1
+            ? props.ScrollItems.Take(props.ScrollItems.Count - 1).ToList()
+            : [];
+
+        this._textScrollPanel.X = 1;
+        this._textScrollPanel.Y = 1;
+        this._textScrollPanel.Width = Console.WindowWidth;
+        this._textScrollPanel.Height = scrollBottom;
+        this._textScrollPanel.Props = new TextScrollPanelProps
+        {
+            Items = scrollItems
+        };
+        this._textScrollPanel.Render();
+
+        // Render the text panel for the last (dynamic) item just below the scroll region
+        this._textPanel.X = 1;
+        this._textPanel.Y = scrollBottom + 1;
+        this._textPanel.Width = Console.WindowWidth;
+        this._textPanel.Height = textPanelHeight;
+        this._textPanel.Props = new TextPanelProps
+        {
+            Items = lastItems,
+        };
+        this._textPanel.Render();
+
+        // Render the bottom rule + child below the text panel
+        this._rule.X = 1;
+        this._rule.Y = scrollBottom + textPanelHeight + 1;
+        this._rule.Props = ruleProps;
+        this._rule.Render();
+
+        // Position cursor for natural typing appearance
+        if (props.Mode == BottomPanelMode.TextInput)
+        {
+            int promptLength = props.Prompt.Length;
+            int textWidth = Console.WindowWidth - promptLength;
+            int textLength = state.InputText.Length;
+
+            // The TextInput starts at rule.Y + 1 (first row inside the rule)
+            int textInputY = this._rule.Y + 1;
+
+            if (textWidth <= 0 || textLength == 0)
+            {
+                // Cursor right after the prompt
+                Console.Write(AnsiEscapes.MoveCursor(textInputY, promptLength + 1));
+            }
+            else
+            {
+                // Calculate which row and column the cursor lands on
+                int cursorRow = textLength < textWidth ? 0 : 1 + ((textLength - textWidth) / textWidth);
+                int cursorCol = textLength < textWidth ? textLength : (textLength - textWidth) % textWidth;
+                Console.Write(AnsiEscapes.MoveCursor(textInputY + cursorRow, promptLength + cursorCol + 1));
+            }
+        }
+        else if (props.Mode == BottomPanelMode.ListSelection
+            && props.ListCustomTextPlaceholder != null
+            && state.SelectedIndex == props.Items.Count)
+        {
+            // Cursor after the typed text in the custom text option
+            // The custom text option is at rule.Y + 1 + Items.Count (0-based row inside rule)
+            int customOptionY = this._rule.Y + 1 + props.Items.Count;
+            // "> " prefix is 2 chars, then the typed text
+            int cursorCol = 2 + state.ListInputText.Length + 1;
+            Console.Write(AnsiEscapes.MoveCursor(customOptionY, cursorCol));
+        }
+    }
+}

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Commands/CommandHandler.cs

@@ -5,24 +5,25 @@ using Microsoft.Agents.AI;
 namespace Harness.Shared.Console.Commands;
 
 /// <summary>
-/// Handles a console command (e.g., /todos, /mode). Command handlers are checked
-/// in order before user input is sent to the agent. The first handler that
-/// accepts the input prevents further handlers from being checked.
+/// Base class for console command handlers (e.g., /todos, /mode). Command handlers
+/// are checked in order before user input is sent to the agent. The first handler
+/// that accepts the input prevents further handlers from being checked.
 /// </summary>
-public interface ICommandHandler
+public abstract class CommandHandler
 {
     /// <summary>
-    /// Gets the help text for this command, displayed in the console header.
+    /// Gets the help text for this command, displayed in the mode-and-help bar.
     /// Returns <see langword="null"/> if the command is not currently available.
     /// </summary>
     /// <returns>Help text like <c>"/todos (show todo list)"</c>, or <see langword="null"/>.</returns>
-    string? GetHelpText();
+    public abstract string? GetHelpText();
 
     /// <summary>
     /// Attempts to handle the given user input.
     /// </summary>
     /// <param name="input">The raw user input string.</param>
     /// <param name="session">The current agent session.</param>
+    /// <param name="ux">The UX container for rendering output.</param>
     /// <returns><see langword="true"/> if this handler handled the input; <see langword="false"/> otherwise.</returns>
-    ValueTask<bool> TryHandleAsync(string input, AgentSession session);
+    public abstract ValueTask<bool> TryHandleAsync(string input, AgentSession session, HarnessUXContainer ux);
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Commands/ModeCommandHandler.cs

@@ -7,7 +7,7 @@ namespace Harness.Shared.Console.Commands;
 /// <summary>
 /// Handles the <c>/mode</c> command to display or switch the current agent mode.
 /// </summary>
-internal sealed class ModeCommandHandler : ICommandHandler
+internal sealed class ModeCommandHandler : CommandHandler
 {
     private readonly AgentModeProvider? _modeProvider;
     private readonly IReadOnlyDictionary<string, ConsoleColor>? _modeColors;
@@ -24,28 +24,28 @@ internal sealed class ModeCommandHandler : ICommandHandler
     }
 
     /// <inheritdoc/>
-    public string? GetHelpText() => this._modeProvider is not null ? "/mode [plan|execute] (show or switch mode)" : null;
+    public override string? GetHelpText() => this._modeProvider is not null ? "/mode [plan|execute] (show or switch mode)" : null;
 
     /// <inheritdoc/>
-    public ValueTask<bool> TryHandleAsync(string input, AgentSession session)
+    public override async ValueTask<bool> TryHandleAsync(string input, AgentSession session, HarnessUXContainer ux)
     {
         if (!input.StartsWith("/mode ", StringComparison.OrdinalIgnoreCase) && !input.Equals("/mode", StringComparison.OrdinalIgnoreCase))
         {
-            return ValueTask.FromResult(false);
+            return false;
         }
 
         if (this._modeProvider is null)
         {
-            System.Console.WriteLine("AgentModeProvider is not available.");
-            return ValueTask.FromResult(true);
+            await ux.WriteInfoLineAsync("AgentModeProvider is not available.").ConfigureAwait(false);
+            return true;
         }
 
         string[] parts = input.Split(' ', 2, StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
         if (parts.Length < 2)
         {
             string current = this._modeProvider.GetMode(session);
-            System.Console.WriteLine($"\n  Current mode: {current}\n");
-            return ValueTask.FromResult(true);
+            await ux.WriteInfoLineAsync($"Current mode: {current}").ConfigureAwait(false);
+            return true;
         }
 
         string newMode = parts[1];
@@ -53,17 +53,14 @@ internal sealed class ModeCommandHandler : ICommandHandler
         try
         {
             this._modeProvider.SetMode(session, newMode);
-            System.Console.ForegroundColor = ConsoleWriter.GetModeColor(newMode, this._modeColors);
-            System.Console.WriteLine($"\n  Switched to {newMode} mode.\n");
-            System.Console.ResetColor();
+            ux.CurrentMode = newMode;
+            await ux.WriteInfoLineAsync($"Switched to {newMode} mode.", ModeColors.Get(newMode, this._modeColors)).ConfigureAwait(false);
         }
         catch (ArgumentException ex)
         {
-            System.Console.ForegroundColor = ConsoleColor.Red;
-            System.Console.WriteLine($"\n  {ex}\n");
-            System.Console.ResetColor();
+            await ux.WriteInfoLineAsync(ex.Message, ConsoleColor.Red).ConfigureAwait(false);
         }
 
-        return ValueTask.FromResult(true);
+        return true;
     }
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Commands/TodoCommandHandler.cs

@@ -7,7 +7,7 @@ namespace Harness.Shared.Console.Commands;
 /// <summary>
 /// Handles the <c>/todos</c> command to display the current todo list.
 /// </summary>
-internal sealed class TodoCommandHandler : ICommandHandler
+internal sealed class TodoCommandHandler : CommandHandler
 {
     private readonly TodoProvider? _todoProvider;
 
@@ -21,10 +21,10 @@ internal sealed class TodoCommandHandler : ICommandHandler
     }
 
     /// <inheritdoc/>
-    public string? GetHelpText() => this._todoProvider is not null ? "/todos (show todo list)" : null;
+    public override string? GetHelpText() => this._todoProvider is not null ? "/todos (show todo list)" : null;
 
     /// <inheritdoc/>
-    public async ValueTask<bool> TryHandleAsync(string input, AgentSession session)
+    public override async ValueTask<bool> TryHandleAsync(string input, AgentSession session, HarnessUXContainer ux)
     {
         if (!input.Equals("/todos", StringComparison.OrdinalIgnoreCase))
         {
@@ -33,34 +33,28 @@ internal sealed class TodoCommandHandler : ICommandHandler
 
         if (this._todoProvider is null)
         {
-            System.Console.WriteLine("TodoProvider is not available.");
+            await ux.WriteInfoLineAsync("TodoProvider is not available.").ConfigureAwait(false);
             return true;
         }
 
         var todos = await this._todoProvider.GetAllTodosAsync(session).ConfigureAwait(false);
         if (todos.Count == 0)
         {
-            System.Console.WriteLine("\n  No todos yet.\n");
+            await ux.WriteInfoLineAsync("No todos yet.").ConfigureAwait(false);
             return true;
         }
 
-        System.Console.WriteLine();
-        System.Console.WriteLine("  ── Todo List ──");
+        await ux.WriteInfoLineAsync("── Todo List ──").ConfigureAwait(false);
         foreach (var item in todos)
         {
             string status = item.IsComplete ? "✓" : "○";
-            System.Console.ForegroundColor = item.IsComplete ? ConsoleColor.DarkGray : ConsoleColor.White;
-            System.Console.Write($"  [{status}] #{item.Id} {item.Title}");
-            if (!string.IsNullOrWhiteSpace(item.Description))
-            {
-                System.Console.Write($" — {item.Description}");
-            }
-
-            System.Console.WriteLine();
+            ConsoleColor color = item.IsComplete ? ConsoleColor.DarkGray : ConsoleColor.White;
+            string description = string.IsNullOrWhiteSpace(item.Description)
+                ? string.Empty
+                : $" — {item.Description}";
+            await ux.WriteInfoLineAsync($"[{status}] #{item.Id} {item.Title}{description}", color).ConfigureAwait(false);
         }
 
-        System.Console.ResetColor();
-        System.Console.WriteLine();
         return true;
     }
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Components/AgentModeAndHelp.cs

@@ -0,0 +1,71 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveComponents;
+using Harness.ConsoleReactiveFramework;
+
+namespace Harness.Shared.Console.Components;
+
+/// <summary>
+/// Props for <see cref="AgentModeAndHelp"/>.
+/// </summary>
+public record AgentModeAndHelpProps : ConsoleReactiveProps
+{
+    /// <summary>Gets or sets the current mode name (e.g. "plan", "execute"), or <see langword="null"/> if no mode is active.</summary>
+    public string? Mode { get; set; }
+
+    /// <summary>Gets or sets the foreground color for the mode label.</summary>
+    public ConsoleColor? ModeColor { get; set; }
+
+    /// <summary>Gets or sets the help text to display (e.g. available commands and exit info).</summary>
+    public string? HelpText { get; set; }
+}
+
+/// <summary>
+/// A component that renders a single fixed line below the bottom rule showing
+/// the current agent mode (in the mode colour) and available commands (in dark grey).
+/// </summary>
+public class AgentModeAndHelp : ConsoleReactiveComponent<AgentModeAndHelpProps, ConsoleReactiveState>
+{
+    /// <summary>
+    /// Calculates the height of the component.
+    /// </summary>
+    /// <param name="props">The component props.</param>
+    /// <returns>1 if there is content to display; otherwise 0.</returns>
+    public static int CalculateHeight(AgentModeAndHelpProps props) =>
+        (props.Mode is not null || !string.IsNullOrEmpty(props.HelpText)) ? 1 : 0;
+
+    /// <inheritdoc />
+    public override void RenderCore(AgentModeAndHelpProps props, ConsoleReactiveState state)
+    {
+        if (props.Mode is null && string.IsNullOrEmpty(props.HelpText))
+        {
+            return;
+        }
+
+        System.Console.Write(AnsiEscapes.SaveCursor);
+        System.Console.Write(AnsiEscapes.MoveAndEraseLine(this.Y));
+
+        bool hasMode = props.Mode is not null;
+
+        if (hasMode)
+        {
+            if (props.ModeColor.HasValue)
+            {
+                System.Console.Write(AnsiEscapes.SetForegroundColor(props.ModeColor.Value));
+            }
+
+            System.Console.Write($" [{props.Mode}]");
+            System.Console.Write(AnsiEscapes.ResetAttributes);
+        }
+
+        if (!string.IsNullOrEmpty(props.HelpText))
+        {
+            string prefix = hasMode ? "  " : " ";
+            System.Console.Write(AnsiEscapes.SetForegroundColor(ConsoleColor.DarkGray));
+            System.Console.Write($"{prefix}{props.HelpText}");
+            System.Console.Write(AnsiEscapes.ResetAttributes);
+        }
+
+        System.Console.Write(AnsiEscapes.RestoreCursor);
+    }
+}

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Components/AgentStatus.cs

@@ -0,0 +1,120 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveComponents;
+using Harness.ConsoleReactiveFramework;
+
+namespace Harness.Shared.Console.Components;
+
+/// <summary>
+/// Props for <see cref="AgentStatus"/>.
+/// </summary>
+public record AgentStatusProps : ConsoleReactiveProps
+{
+    /// <summary>Gets or sets a value indicating whether the spinner is visible.</summary>
+    public bool ShowSpinner { get; set; }
+
+    /// <summary>Gets or sets the formatted token usage text to display.</summary>
+    public string? UsageText { get; set; }
+}
+
+/// <summary>
+/// State for <see cref="AgentStatus"/>.
+/// </summary>
+/// <param name="SpinnerIndex">The current spinner animation frame index.</param>
+public record AgentStatusState(int SpinnerIndex = 0) : ConsoleReactiveState;
+
+/// <summary>
+/// A component that renders a single-line agent status bar with an animated spinner
+/// and token usage statistics. Positioned above the rule in the non-scrolling area.
+/// </summary>
+public class AgentStatus : ConsoleReactiveComponent<AgentStatusProps, AgentStatusState>, IDisposable
+{
+    private static readonly string[] s_spinnerFrames =
+    [
+        "⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏",
+    ];
+
+    private readonly Timer _timer;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AgentStatus"/> class.
+    /// </summary>
+    public AgentStatus()
+    {
+        this.State = new AgentStatusState();
+        this._timer = new Timer(this.OnTimerTick, null, TimeSpan.Zero, TimeSpan.FromMilliseconds(100));
+    }
+
+    /// <summary>
+    /// Calculates the height of the agent status component.
+    /// </summary>
+    /// <param name="props">The component props.</param>
+    /// <returns>1 if the spinner or usage text is visible; otherwise 0.</returns>
+    public static int CalculateHeight(AgentStatusProps props)
+    {
+        return (props.ShowSpinner || !string.IsNullOrEmpty(props.UsageText)) ? 1 : 0;
+    }
+
+    /// <summary>
+    /// Disposes the internal spinner timer.
+    /// </summary>
+    public void Dispose()
+    {
+        this.Dispose(true);
+        GC.SuppressFinalize(this);
+    }
+
+    /// <summary>
+    /// Releases managed resources.
+    /// </summary>
+    /// <param name="disposing"><c>true</c> to release managed resources.</param>
+    protected virtual void Dispose(bool disposing)
+    {
+        if (disposing)
+        {
+            this._timer.Dispose();
+        }
+    }
+
+    /// <inheritdoc />
+    public override void RenderCore(AgentStatusProps props, AgentStatusState state)
+    {
+        if (!props.ShowSpinner && string.IsNullOrEmpty(props.UsageText))
+        {
+            return;
+        }
+
+        System.Console.Write(AnsiEscapes.SaveCursor);
+        System.Console.Write(AnsiEscapes.MoveAndEraseLine(this.Y));
+
+        if (props.ShowSpinner)
+        {
+            string frame = s_spinnerFrames[state.SpinnerIndex];
+            System.Console.Write(AnsiEscapes.SetForegroundColor(ConsoleColor.Cyan));
+            System.Console.Write($" {frame} ");
+            System.Console.Write(AnsiEscapes.ResetAttributes);
+        }
+        else
+        {
+            System.Console.Write("   ");
+        }
+
+        if (!string.IsNullOrEmpty(props.UsageText))
+        {
+            System.Console.Write(AnsiEscapes.SetForegroundColor(ConsoleColor.DarkGray));
+            System.Console.Write(props.UsageText);
+            System.Console.Write(AnsiEscapes.ResetAttributes);
+        }
+
+        System.Console.Write(AnsiEscapes.RestoreCursor);
+    }
+
+    private void OnTimerTick(object? timerState)
+    {
+        if (this.Props is { ShowSpinner: true })
+        {
+            int nextIndex = ((this.State?.SpinnerIndex ?? 0) + 1) % s_spinnerFrames.Length;
+            this.SetState(new AgentStatusState(nextIndex));
+        }
+    }
+}

dotnet/samples/02-agents/Harness/Harness_Shared_Console/ConsoleWriter.cs

@@ -1,278 +0,0 @@
-// Copyright (c) Microsoft. All rights reserved.
-
-using Spectre.Console;
-
-namespace Harness.Shared.Console;
-
-/// <summary>
-/// Centralizes all console output and spinner management for the harness console.
-/// Observers write through this class so the spinner is automatically paused before output.
-/// </summary>
-public sealed class ConsoleWriter : IDisposable
-{
-    private readonly Spinner _spinner = new();
-    private readonly IReadOnlyDictionary<string, ConsoleColor>? _modeColors;
-
-    private bool _lastWasText;
-    private bool _hasReceivedAnyText;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="ConsoleWriter"/> class.
-    /// </summary>
-    /// <param name="modeColors">Optional mapping of mode names to console colors.</param>
-    public ConsoleWriter(IReadOnlyDictionary<string, ConsoleColor>? modeColors = null)
-    {
-        this._modeColors = modeColors;
-    }
-
-    /// <summary>
-    /// Gets or sets the current agent mode (e.g., "plan", "execute").
-    /// Used to determine the console color for mode-prefixed output.
-    /// </summary>
-    public string? CurrentMode { get; set; }
-
-    /// <summary>
-    /// Writes the agent response header (e.g., "[plan] Agent: ") and starts the spinner.
-    /// </summary>
-    public void WriteResponseHeader()
-    {
-        if (this.CurrentMode is not null)
-        {
-            System.Console.ForegroundColor = GetModeColor(this.CurrentMode, this._modeColors);
-            System.Console.Write($"\n[{this.CurrentMode}] Agent: ");
-        }
-        else
-        {
-            System.Console.Write("\nAgent: ");
-        }
-
-        this._lastWasText = true;
-        this._hasReceivedAnyText = false;
-        this._spinner.Start();
-    }
-
-    /// <summary>
-    /// Writes informational output with automatic prefix spacing, without a trailing newline.
-    /// Use when continuation content will be appended on the same line.
-    /// </summary>
-    /// <param name="text">The informational text to write (without leading newline/indent — added automatically).</param>
-    /// <param name="color">Optional console color for the text.</param>
-    public async Task WriteInfoAsync(string text, ConsoleColor? color = null)
-    {
-        await this.WriteInfoCoreAsync(text, color, newLine: false);
-    }
-
-    /// <summary>
-    /// Writes informational output with automatic prefix spacing, followed by a newline.
-    /// </summary>
-    /// <param name="text">The informational text to write (without leading newline/indent — added automatically).</param>
-    /// <param name="color">Optional console color for the text.</param>
-    public async Task WriteInfoLineAsync(string text, ConsoleColor? color = null)
-    {
-        await this.WriteInfoCoreAsync(text, color, newLine: true);
-    }
-
-    private async Task WriteInfoCoreAsync(string text, ConsoleColor? color, bool newLine)
-    {
-        await this._spinner.StopAsync();
-
-        string prefix = this._lastWasText ? "\n\n  " : "  ";
-        this._lastWasText = false;
-
-        System.Console.ForegroundColor = color ?? GetModeColor(this.CurrentMode, this._modeColors);
-
-        if (newLine)
-        {
-            System.Console.WriteLine(prefix + text);
-        }
-        else
-        {
-            System.Console.Write(prefix + text);
-        }
-
-        System.Console.ForegroundColor = GetModeColor(this.CurrentMode, this._modeColors);
-
-        this._spinner.Start();
-    }
-
-    /// <summary>
-    /// Writes text output from the agent, managing line break state.
-    /// Ensures a newline is written before the first text output.
-    /// </summary>
-    /// <param name="text">The text to write.</param>
-    /// <param name="color">Optional console color override for this text.</param>
-    public async Task WriteTextAsync(string text, ConsoleColor? color = null)
-    {
-        await this._spinner.StopAsync();
-
-        if (!this._lastWasText)
-        {
-            System.Console.Write("\n");
-            this._lastWasText = true;
-        }
-
-        this._hasReceivedAnyText = true;
-
-        if (color.HasValue)
-        {
-            System.Console.ForegroundColor = color.Value;
-        }
-
-        System.Console.Write(text);
-
-        if (color.HasValue)
-        {
-            System.Console.ForegroundColor = GetModeColor(this.CurrentMode, this._modeColors);
-        }
-
-        this._spinner.Start();
-    }
-
-    /// <summary>
-    /// Reads a line of input from the console, pausing the spinner while waiting for input.
-    /// Optionally displays a prompt before reading. The prompt is rendered between
-    /// two horizontal rules for visual clarity.
-    /// </summary>
-    /// <param name="prompt">Optional prompt text to display before reading input.</param>
-    /// <param name="promptColor">Optional console color for the prompt text.</param>
-    /// <returns>The line read from the console, or <c>null</c> if no input is available.</returns>
-    public async Task<string?> ReadLineAsync(string? prompt = null, ConsoleColor? promptColor = null)
-    {
-        await this._spinner.StopAsync();
-
-        if (prompt is not null)
-        {
-            System.Console.WriteLine();
-            AnsiConsole.Write(this.CreateModeRule());
-
-            if (promptColor.HasValue)
-            {
-                System.Console.ForegroundColor = promptColor.Value;
-            }
-
-            System.Console.Write($"  {prompt}");
-
-            if (promptColor.HasValue)
-            {
-                System.Console.ForegroundColor = GetModeColor(this.CurrentMode, this._modeColors);
-            }
-        }
-
-        string? input = System.Console.ReadLine();
-
-        if (prompt is not null)
-        {
-            AnsiConsole.Write(this.CreateModeRule());
-        }
-
-        this._lastWasText = false;
-        return input;
-    }
-
-    /// <summary>
-    /// Presents a selection prompt with the given choices, plus an option to type a custom response.
-    /// Uses Spectre.Console <see cref="SelectionPrompt{T}"/> for interactive arrow-key selection.
-    /// </summary>
-    /// <param name="title">The title/question displayed above the selection list.</param>
-    /// <param name="choices">The list of choices to present.</param>
-    /// <returns>The selected choice text, or the custom-typed response.</returns>
-    public async Task<string> ReadSelectionAsync(string title, IList<string> choices)
-    {
-        await this._spinner.StopAsync();
-
-        AnsiConsole.Write(this.CreateModeRule());
-
-        const string FreeformOption = "✏️  Type a custom response...";
-        var allChoices = choices.Concat([FreeformOption]).ToList();
-
-        var prompt = new SelectionPrompt<string>()
-            .Title($"  [bold]{Markup.Escape(title)}[/]")
-            .PageSize(10)
-            .AddChoices(allChoices);
-
-        string selection = AnsiConsole.Prompt(prompt);
-
-        if (selection == FreeformOption)
-        {
-            var textPrompt = new TextPrompt<string>("  [grey]Response:[/]");
-            selection = AnsiConsole.Prompt(textPrompt);
-        }
-
-        AnsiConsole.MarkupLine($"  [dim]→ {Markup.Escape(selection)}[/]");
-        AnsiConsole.Write(this.CreateModeRule());
-
-        this._lastWasText = false;
-        return selection;
-    }
-
-    /// <summary>
-    /// Writes the stream-complete footer (handles "no text response" fallback, resets color).
-    /// </summary>
-    public async Task WriteStreamFooterAsync(bool hasFollowUpMessages)
-    {
-        await this._spinner.StopAsync();
-
-        if (!this._hasReceivedAnyText && !hasFollowUpMessages)
-        {
-            System.Console.ForegroundColor = ConsoleColor.DarkYellow;
-            System.Console.Write("\n  (no text response from agent)");
-        }
-
-        System.Console.ResetColor();
-        System.Console.WriteLine();
-    }
-
-    /// <inheritdoc/>
-    public void Dispose()
-    {
-        this._spinner.Dispose();
-    }
-
-    /// <summary>
-    /// Gets the console color associated with a mode name, using the provided color map.
-    /// </summary>
-    internal static ConsoleColor GetModeColor(string? mode, IReadOnlyDictionary<string, ConsoleColor>? modeColors = null)
-    {
-        if (mode is null)
-        {
-            return ConsoleColor.Gray;
-        }
-
-        if (modeColors is not null && modeColors.TryGetValue(mode, out var color))
-        {
-            return color;
-        }
-
-        return ConsoleColor.Gray;
-    }
-
-    /// <summary>
-    /// Creates a <see cref="Rule"/> styled with the current mode color.
-    /// </summary>
-    internal Rule CreateModeRule()
-    {
-        var spectreColor = ToSpectreColor(GetModeColor(this.CurrentMode, this._modeColors));
-        return new Rule().RuleStyle(new Style(spectreColor));
-    }
-
-    internal static Color ToSpectreColor(ConsoleColor consoleColor) => consoleColor switch
-    {
-        ConsoleColor.Black => Color.Black,
-        ConsoleColor.DarkBlue => Color.Blue,
-        ConsoleColor.DarkGreen => Color.Green,
-        ConsoleColor.DarkCyan => Color.Teal,
-        ConsoleColor.DarkRed => Color.Red,
-        ConsoleColor.DarkMagenta => Color.Purple,
-        ConsoleColor.DarkYellow => Color.Olive,
-        ConsoleColor.Gray => Color.Silver,
-        ConsoleColor.DarkGray => Color.Grey,
-        ConsoleColor.Blue => Color.Blue1,
-        ConsoleColor.Green => Color.Green1,
-        ConsoleColor.Cyan => Color.Aqua,
-        ConsoleColor.Red => Color.Red1,
-        ConsoleColor.Magenta => Color.Fuchsia,
-        ConsoleColor.Yellow => Color.Yellow,
-        ConsoleColor.White => Color.White,
-        _ => Color.Silver,
-    };
-}

dotnet/samples/02-agents/Harness/Harness_Shared_Console/HarnessAppComponent.cs

@@ -0,0 +1,553 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveComponents;
+using Harness.ConsoleReactiveFramework;
+using Harness.Shared.Console.Components;
+
+namespace Harness.Shared.Console;
+
+/// <summary>
+/// Determines which component is shown in the bottom panel.
+/// </summary>
+public enum BottomPanelMode
+{
+    /// <summary>Show the text input component for user input.</summary>
+    TextInput,
+
+    /// <summary>Show the list selection component for interactive prompts.</summary>
+    ListSelection,
+
+    /// <summary>Show a disabled input indicator during agent streaming.</summary>
+    Streaming,
+}
+
+/// <summary>
+/// Event arguments for the <see cref="HarnessAppComponent.InputSubmitted"/> event.
+/// </summary>
+public sealed class InputSubmittedEventArgs : EventArgs
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="InputSubmittedEventArgs"/> class.
+    /// </summary>
+    /// <param name="text">The submitted text.</param>
+    /// <param name="mode">The bottom panel mode in which the input was submitted.</param>
+    public InputSubmittedEventArgs(string text, BottomPanelMode mode)
+    {
+        this.Text = text;
+        this.Mode = mode;
+    }
+
+    /// <summary>Gets the submitted text.</summary>
+    public string Text { get; }
+
+    /// <summary>Gets the bottom panel mode in which the input was submitted.</summary>
+    public BottomPanelMode Mode { get; }
+}
+
+/// <summary>
+/// Props for <see cref="HarnessAppComponent"/>.
+/// </summary>
+public record HarnessAppComponentProps : ConsoleReactiveProps
+{
+    /// <summary>Gets or sets the list selection choices (for ListSelection mode).</summary>
+    public IReadOnlyList<string> Items { get; set; } = Array.Empty<string>();
+
+    /// <summary>Gets or sets the scroll items (output entries) to render in the scroll panel.</summary>
+    public IReadOnlyList<object> ScrollItems { get; set; } = [];
+
+    /// <summary>Gets or sets the bottom panel mode.</summary>
+    public BottomPanelMode Mode { get; set; } = BottomPanelMode.TextInput;
+
+    /// <summary>Gets or sets the prompt string for text input mode.</summary>
+    public string Prompt { get; set; } = "You: ";
+
+    /// <summary>Gets or sets the placeholder text shown when the input is empty.</summary>
+    public string Placeholder { get; set; } = "";
+
+    /// <summary>Gets or sets the highlight color for the active list item.</summary>
+    public ConsoleColor ListHighlightColor { get; set; } = ConsoleColor.Cyan;
+
+    /// <summary>Gets or sets the placeholder text for the custom text input option in the list.</summary>
+    public string? ListCustomTextPlaceholder { get; set; }
+
+    /// <summary>Gets or sets the foreground color for the rule borders and mode label.</summary>
+    public ConsoleColor? ModeColor { get; set; }
+
+    /// <summary>Gets or sets the current mode name displayed below the bottom rule (e.g. "plan").</summary>
+    public string? ModeText { get; set; }
+
+    /// <summary>Gets or sets the help text displayed below the bottom rule (available commands).</summary>
+    public string? HelpText { get; set; }
+
+    /// <summary>Gets or sets the title text displayed above the list selection (for interactive prompts).</summary>
+    public string? ListTitle { get; set; }
+
+    /// <summary>Gets or sets a value indicating whether input is enabled during streaming.</summary>
+    public bool InputEnabled { get; set; }
+
+    /// <summary>Gets or sets the prompt to show during streaming when input is disabled.</summary>
+    public string StreamingPrompt { get; set; } = "(agent is running...)";
+
+    /// <summary>Gets or sets a value indicating whether the agent status spinner is visible.</summary>
+    public bool ShowSpinner { get; set; }
+
+    /// <summary>Gets or sets the formatted token usage text to display in the status bar.</summary>
+    public string? UsageText { get; set; }
+
+    /// <summary>Gets or sets the queued input items to display above the rule.</summary>
+    public IReadOnlyList<object> QueuedItems { get; set; } = [];
+}
+
+/// <summary>
+/// Internal state for <see cref="HarnessAppComponent"/>.
+/// </summary>
+public record HarnessAppComponentState : ConsoleReactiveState
+{
+    /// <summary>Gets the selected index in list selection mode.</summary>
+    public int SelectedIndex { get; init; }
+
+    /// <summary>Gets the current input text being typed.</summary>
+    public string InputText { get; init; } = "";
+
+    /// <summary>Gets the current text being typed into the list's custom text option.</summary>
+    public string ListInputText { get; init; } = "";
+
+    /// <summary>Gets the current console width in columns.</summary>
+    public int ConsoleWidth { get; init; }
+
+    /// <summary>Gets the current console height in rows.</summary>
+    public int ConsoleHeight { get; init; }
+}
+
+/// <summary>
+/// The main application component for the Harness console. Manages the scroll region
+/// and bottom panel (text input, list selection, or streaming indicator), and emits
+/// an <see cref="InputSubmitted"/> event when the user submits text in any mode.
+/// </summary>
+public class HarnessAppComponent : ConsoleReactiveComponent<HarnessAppComponentProps, HarnessAppComponentState>, IDisposable
+{
+    private readonly TopBottomRule _rule = new();
+    private readonly ListSelection _listSelection = new();
+    private readonly TextInput _textInput = new();
+    private readonly TextScrollPanel _textScrollPanel;
+    private readonly TextPanel _textPanel;
+    private readonly TextPanel _queuedPanel;
+    private readonly AgentStatus _agentStatus = new();
+    private readonly AgentModeAndHelp _modeAndHelp = new();
+    private readonly Func<object, string> _renderItem;
+    private bool _resizedSinceLastRender;
+    private bool _deactivated;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="HarnessAppComponent"/> class.
+    /// </summary>
+    /// <param name="renderScrollItem">A delegate that renders a single output entry and returns the text to display.</param>
+    public HarnessAppComponent(Func<object, string> renderScrollItem)
+    {
+        this._renderItem = renderScrollItem;
+        this._textScrollPanel = new TextScrollPanel(renderScrollItem);
+        this._textPanel = new TextPanel(renderScrollItem);
+        this._queuedPanel = new TextPanel(renderScrollItem);
+        this.State = new HarnessAppComponentState
+        {
+            ConsoleWidth = System.Console.WindowWidth,
+            ConsoleHeight = System.Console.WindowHeight,
+        };
+        KeyEventListener.Instance.KeyPressed += this.OnKeyPressed;
+        ConsoleResizeListener.Instance.ConsoleResized += this.OnConsoleResized;
+    }
+
+    /// <summary>
+    /// Gets the 1-based row number of the last row in the output scroll region.
+    /// </summary>
+    public int ScrollRegionBottom { get; private set; }
+
+    /// <summary>
+    /// Occurs when the user submits input via Enter, in any mode (text input, list selection,
+    /// or streaming injection). Consumers inspect <see cref="InputSubmittedEventArgs.Mode"/>
+    /// to decide how to handle the submission.
+    /// </summary>
+    public event EventHandler<InputSubmittedEventArgs>? InputSubmitted;
+
+    /// <summary>
+    /// Deactivates the component, resetting the scroll region and unsubscribing from events.
+    /// This method is idempotent and safe to call multiple times.
+    /// </summary>
+    public void Deactivate()
+    {
+        if (this._deactivated)
+        {
+            return;
+        }
+
+        this._deactivated = true;
+        this._agentStatus.Dispose();
+        KeyEventListener.Instance.KeyPressed -= this.OnKeyPressed;
+        ConsoleResizeListener.Instance.ConsoleResized -= this.OnConsoleResized;
+        System.Console.Write(AnsiEscapes.ResetScrollRegion);
+        System.Console.Write(AnsiEscapes.MoveCursor(System.Console.WindowHeight, 1));
+        System.Console.WriteLine();
+    }
+
+    /// <inheritdoc/>
+    public void Dispose()
+    {
+        this.Dispose(true);
+        GC.SuppressFinalize(this);
+    }
+
+    /// <summary>
+    /// Releases managed resources.
+    /// </summary>
+    /// <param name="disposing"><c>true</c> to release managed resources.</param>
+    protected virtual void Dispose(bool disposing)
+    {
+        if (disposing)
+        {
+            this.Deactivate();
+        }
+    }
+
+    private void OnKeyPressed(object? sender, KeyPressEventArgs e)
+    {
+        if (this.Props!.Mode == BottomPanelMode.TextInput)
+        {
+            this.HandleTextInputKey(e);
+        }
+        else if (this.Props.Mode == BottomPanelMode.ListSelection)
+        {
+            this.HandleListSelectionKey(e);
+        }
+        else if (this.Props.Mode == BottomPanelMode.Streaming && this.Props.InputEnabled)
+        {
+            this.HandleStreamingInputKey(e);
+        }
+    }
+
+    private void HandleTextInputKey(KeyPressEventArgs e)
+    {
+        if (e.KeyInfo.Key == ConsoleKey.Enter)
+        {
+            string text = this.State!.InputText;
+            if (string.IsNullOrWhiteSpace(text))
+            {
+                return;
+            }
+
+            this.SetState(this.State with { InputText = "" });
+            this.InputSubmitted?.Invoke(this, new InputSubmittedEventArgs(text, BottomPanelMode.TextInput));
+        }
+        else if (e.KeyInfo.Key == ConsoleKey.Backspace)
+        {
+            if (this.State!.InputText.Length > 0)
+            {
+                this.SetState(this.State with { InputText = this.State.InputText[..^1] });
+            }
+        }
+        else if (e.KeyInfo.KeyChar != '\0' && !char.IsControl(e.KeyInfo.KeyChar))
+        {
+            this.SetState(this.State! with { InputText = this.State.InputText + e.KeyInfo.KeyChar });
+        }
+    }
+
+    private void HandleListSelectionKey(KeyPressEventArgs e)
+    {
+        int maxIndex = this.Props!.Items.Count - 1;
+        if (this.Props.ListCustomTextPlaceholder != null)
+        {
+            maxIndex = this.Props.Items.Count;
+        }
+
+        bool isOnCustomTextOption = this.Props.ListCustomTextPlaceholder != null
+            && this.State!.SelectedIndex == this.Props.Items.Count;
+
+        if (e.KeyInfo.Key == ConsoleKey.UpArrow)
+        {
+            this.SetState(this.State! with { SelectedIndex = Math.Max(0, this.State.SelectedIndex - 1) });
+        }
+        else if (e.KeyInfo.Key == ConsoleKey.DownArrow)
+        {
+            this.SetState(this.State! with { SelectedIndex = Math.Min(maxIndex, this.State.SelectedIndex + 1) });
+        }
+        else if (e.KeyInfo.Key == ConsoleKey.Enter)
+        {
+            string result = isOnCustomTextOption
+                ? this.State!.ListInputText
+                : this.Props.Items[this.State!.SelectedIndex];
+
+            this.SetState(this.State with { ListInputText = "", SelectedIndex = 0 });
+            this.InputSubmitted?.Invoke(this, new InputSubmittedEventArgs(result, BottomPanelMode.ListSelection));
+        }
+        else if (isOnCustomTextOption)
+        {
+            if (e.KeyInfo.Key == ConsoleKey.Backspace)
+            {
+                if (this.State!.ListInputText.Length > 0)
+                {
+                    this.SetState(this.State with { ListInputText = this.State.ListInputText[..^1] });
+                }
+            }
+            else if (e.KeyInfo.KeyChar != '\0' && !char.IsControl(e.KeyInfo.KeyChar))
+            {
+                this.SetState(this.State! with { ListInputText = this.State.ListInputText + e.KeyInfo.KeyChar });
+            }
+        }
+    }
+
+    private void HandleStreamingInputKey(KeyPressEventArgs e)
+    {
+        // During streaming with input enabled, capture text for message injection
+        if (e.KeyInfo.Key == ConsoleKey.Enter)
+        {
+            string text = this.State!.InputText;
+            if (string.IsNullOrWhiteSpace(text))
+            {
+                return;
+            }
+
+            this.SetState(this.State with { InputText = "" });
+            this.InputSubmitted?.Invoke(this, new InputSubmittedEventArgs(text, BottomPanelMode.Streaming));
+        }
+        else if (e.KeyInfo.Key == ConsoleKey.Backspace)
+        {
+            if (this.State!.InputText.Length > 0)
+            {
+                this.SetState(this.State with { InputText = this.State.InputText[..^1] });
+            }
+        }
+        else if (e.KeyInfo.KeyChar != '\0' && !char.IsControl(e.KeyInfo.KeyChar))
+        {
+            this.SetState(this.State! with { InputText = this.State.InputText + e.KeyInfo.KeyChar });
+        }
+    }
+
+    private void OnConsoleResized(object? sender, ConsoleResizeEventArgs e)
+    {
+        this._resizedSinceLastRender = true;
+        this.SetState(this.State! with
+        {
+            ConsoleWidth = e.NewWidth,
+            ConsoleHeight = e.NewHeight,
+        });
+    }
+
+    /// <inheritdoc />
+    public override void RenderCore(HarnessAppComponentProps props, HarnessAppComponentState state)
+    {
+        // Determine the text panel height for the last scroll item
+        IReadOnlyList<object> lastItems = props.ScrollItems.Count > 0
+            ? [props.ScrollItems[^1]]
+            : [];
+        int textPanelHeight = TextPanel.CalculateHeight(lastItems, this._renderItem);
+        if (textPanelHeight > 0)
+        {
+            textPanelHeight++; // Extra line for spacing between text panel and rule
+        }
+
+        // Calculate queued items panel height
+        int queuedPanelHeight = TextPanel.CalculateHeight(props.QueuedItems, this._renderItem);
+
+        // Build the bottom panel child based on mode
+        ConsoleReactiveComponent bottomChild;
+        int bottomChildHeight;
+
+        if (props.Mode == BottomPanelMode.ListSelection)
+        {
+            var listProps = new ListSelectionProps
+            {
+                Title = props.ListTitle,
+                Items = props.Items,
+                SelectedIndex = state.SelectedIndex,
+                HighlightColor = props.ListHighlightColor,
+                CustomTextPlaceholder = props.ListCustomTextPlaceholder,
+                CustomText = state.ListInputText,
+            };
+
+            bottomChildHeight = ListSelection.CalculateHeight(listProps);
+            this._listSelection.Height = bottomChildHeight;
+            this._listSelection.Props = listProps;
+            bottomChild = this._listSelection;
+        }
+        else if (props.Mode == BottomPanelMode.Streaming)
+        {
+            TextInputProps textInputProps;
+            if (props.InputEnabled)
+            {
+                textInputProps = new TextInputProps
+                {
+                    Prompt = props.Prompt,
+                    Text = state.InputText,
+                    Placeholder = props.Placeholder,
+                };
+            }
+            else
+            {
+                textInputProps = new TextInputProps
+                {
+                    Prompt = props.Prompt,
+                    Text = "",
+                    Placeholder = props.StreamingPrompt,
+                };
+            }
+
+            bottomChildHeight = TextInput.CalculateHeight(textInputProps, state.ConsoleWidth);
+            this._textInput.Width = state.ConsoleWidth;
+            this._textInput.Height = bottomChildHeight;
+            this._textInput.Props = textInputProps;
+            bottomChild = this._textInput;
+        }
+        else
+        {
+            var textInputProps = new TextInputProps
+            {
+                Prompt = props.Prompt,
+                Text = state.InputText,
+                Placeholder = props.Placeholder,
+            };
+
+            bottomChildHeight = TextInput.CalculateHeight(textInputProps, state.ConsoleWidth);
+            this._textInput.Width = state.ConsoleWidth;
+            this._textInput.Height = bottomChildHeight;
+            this._textInput.Props = textInputProps;
+            bottomChild = this._textInput;
+        }
+
+        var ruleProps = new TopBottomRuleProps
+        {
+            Width = state.ConsoleWidth,
+            Color = props.ModeColor,
+            Children = [bottomChild],
+        };
+
+        // Calculate the agent status height
+        var agentStatusProps = new AgentStatusProps
+        {
+            ShowSpinner = props.ShowSpinner,
+            UsageText = props.UsageText,
+        };
+        int agentStatusHeight = AgentStatus.CalculateHeight(agentStatusProps);
+
+        // Calculate the mode-and-help height
+        var modeAndHelpProps = new AgentModeAndHelpProps
+        {
+            Mode = props.ModeText,
+            ModeColor = props.ModeColor,
+            HelpText = props.HelpText,
+        };
+        int modeAndHelpHeight = AgentModeAndHelp.CalculateHeight(modeAndHelpProps);
+
+        int ruleHeight = TopBottomRule.CalculateHeight(ruleProps);
+        int scrollBottom = Math.Max(1, state.ConsoleHeight - ruleHeight - textPanelHeight - agentStatusHeight - queuedPanelHeight - modeAndHelpHeight);
+
+        // If scroll region changed or a clear is needed, reset everything
+        if (this._resizedSinceLastRender || (this.ScrollRegionBottom != 0 && scrollBottom != this.ScrollRegionBottom))
+        {
+            System.Console.Write(AnsiEscapes.EraseEntireScreen);
+            System.Console.Write(AnsiEscapes.EraseScrollbackBuffer);
+            this._textScrollPanel.Reset();
+            this._resizedSinceLastRender = false;
+        }
+
+        this.ScrollRegionBottom = scrollBottom;
+
+        System.Console.Write(AnsiEscapes.SetScrollRegion(scrollBottom));
+
+        // Render text scroll panel in the scroll area (all items except the last)
+        IReadOnlyList<object> scrollItems = props.ScrollItems.Count > 1
+            ? props.ScrollItems.Take(props.ScrollItems.Count - 1).ToList()
+            : [];
+
+        this._textScrollPanel.X = 1;
+        this._textScrollPanel.Y = 1;
+        this._textScrollPanel.Width = state.ConsoleWidth;
+        this._textScrollPanel.Height = scrollBottom;
+        this._textScrollPanel.Props = new TextScrollPanelProps
+        {
+            Items = scrollItems,
+        };
+        this._textScrollPanel.Render();
+
+        // Render the text panel for the last (dynamic) item just below the scroll region
+        this._textPanel.X = 1;
+        this._textPanel.Y = scrollBottom + 1;
+        this._textPanel.Width = state.ConsoleWidth;
+        this._textPanel.Height = textPanelHeight;
+        this._textPanel.Props = new TextPanelProps
+        {
+            Items = lastItems,
+        };
+        this._textPanel.Render();
+
+        // Render queued input items between text panel and agent status
+        int queuedPanelY = scrollBottom + textPanelHeight + 1;
+        this._queuedPanel.X = 1;
+        this._queuedPanel.Y = queuedPanelY;
+        this._queuedPanel.Width = state.ConsoleWidth;
+        this._queuedPanel.Height = queuedPanelHeight;
+        this._queuedPanel.Props = new TextPanelProps
+        {
+            Items = props.QueuedItems,
+        };
+        this._queuedPanel.Render();
+
+        // Render the agent status line between queued items and rule
+        int agentStatusY = queuedPanelY + queuedPanelHeight;
+        this._agentStatus.X = 1;
+        this._agentStatus.Y = agentStatusY;
+        this._agentStatus.Width = state.ConsoleWidth;
+        this._agentStatus.Height = agentStatusHeight;
+        this._agentStatus.Props = agentStatusProps;
+        this._agentStatus.Render();
+
+        // Render the bottom rule + child below the agent status
+        this._rule.X = 1;
+        this._rule.Y = agentStatusY + agentStatusHeight;
+        this._rule.Props = ruleProps;
+        this._rule.Render();
+
+        // Render the mode-and-help line below the bottom rule
+        int modeAndHelpY = this._rule.Y + ruleHeight;
+        this._modeAndHelp.X = 1;
+        this._modeAndHelp.Y = modeAndHelpY;
+        this._modeAndHelp.Width = state.ConsoleWidth;
+        this._modeAndHelp.Height = modeAndHelpHeight;
+        this._modeAndHelp.Props = modeAndHelpProps;
+        this._modeAndHelp.Render();
+
+        // Position cursor for natural typing appearance
+        this.PositionCursor(props, state);
+    }
+
+    private void PositionCursor(HarnessAppComponentProps props, HarnessAppComponentState state)
+    {
+        if (props.Mode == BottomPanelMode.TextInput
+            || (props.Mode == BottomPanelMode.Streaming && props.InputEnabled))
+        {
+            int promptLength = props.Prompt.Length;
+            int textWidth = state.ConsoleWidth - promptLength;
+            int textLength = state.InputText.Length;
+
+            int textInputY = this._rule.Y + 1;
+
+            if (textWidth <= 0 || textLength == 0)
+            {
+                System.Console.Write(AnsiEscapes.MoveCursor(textInputY, promptLength + 1));
+            }
+            else
+            {
+                int cursorRow = textLength < textWidth ? 0 : 1 + ((textLength - textWidth) / textWidth);
+                int cursorCol = textLength < textWidth ? textLength : (textLength - textWidth) % textWidth;
+                System.Console.Write(AnsiEscapes.MoveCursor(textInputY + cursorRow, promptLength + cursorCol + 1));
+            }
+        }
+        else if (props.Mode == BottomPanelMode.ListSelection
+            && props.ListCustomTextPlaceholder != null
+            && state.SelectedIndex == props.Items.Count)
+        {
+            int titleLines = props.ListTitle?.Split('\n').Length ?? 0;
+            int customOptionY = this._rule.Y + 1 + titleLines + props.Items.Count;
+            int cursorCol = 2 + state.ListInputText.Length + 1;
+            System.Console.Write(AnsiEscapes.MoveCursor(customOptionY, cursorCol));
+        }
+    }
+}

dotnet/samples/02-agents/Harness/Harness_Shared_Console/HarnessConsole.cs

@@ -34,42 +34,55 @@ public static class HarnessConsole
                 nameof(options));
         }
 
-        System.Console.WriteLine($"=== {title} ===");
-        System.Console.WriteLine(userPrompt);
-
         var todoProvider = agent.GetService<TodoProvider>();
         var modeProvider = agent.GetService<AgentModeProvider>();
+        var messageInjector = agent.GetService<MessageInjectingChatClient>();
 
-        // Build command handlers.
-        var commandHandlers = new List<ICommandHandler>
+        var commandHandlers = new List<CommandHandler>
         {
             new TodoCommandHandler(todoProvider),
             new ModeCommandHandler(modeProvider, options.ModeColors),
         };
 
-        var commands = commandHandlers
+        AgentSession session = await agent.CreateSessionAsync();
+
+        using var ux = new HarnessUXContainer(
+            placeholder: userPrompt,
+            initialMode: modeProvider?.GetMode(session),
+            inputEnabled: messageInjector is not null,
+            modeColors: options.ModeColors);
+
+        // Streaming-mode submissions are enqueued for injection; the queued display
+        // is then refreshed from the injector's current pending list.
+        ux.StreamingInputReceived += (sender, e) =>
+        {
+            if (messageInjector is null)
+            {
+                return;
+            }
+
+            messageInjector.EnqueueMessages(session, [new ChatMessage(ChatRole.User, e.Text)]);
+            ux.ShowQueuedMessages(messageInjector.GetPendingMessages(session));
+        };
+
+        var commandHelp = commandHandlers
             .Select(h => h.GetHelpText())
             .Where(t => t is not null)
-            .Append("exit (quit)");
+            .Append("exit (quit)")!;
 
-        System.Console.WriteLine($"Commands: {string.Join(", ", commands)}");
-        System.Console.WriteLine();
+        ux.Initialize(title, commandHelp!, messageInjector is not null);
 
-        AgentSession session = await agent.CreateSessionAsync();
-        using var writer = new ConsoleWriter(options.ModeColors);
-        writer.CurrentMode = modeProvider?.GetMode(session);
+        string userInput = await ux.WaitForInputAsync();
 
-        string prompt = BuildUserPrompt(modeProvider, session);
-        string? userInput = await writer.ReadLineAsync(prompt);
-
-        // Main loop to run a command or agent and get the next user command/input.
         while (!string.IsNullOrWhiteSpace(userInput) && !userInput.Equals("exit", StringComparison.OrdinalIgnoreCase))
         {
+            ux.WriteUserInputEcho(userInput);
+
             // Check command handlers first — first one to handle wins.
             bool handled = false;
             foreach (var handler in commandHandlers)
             {
-                if (await handler.TryHandleAsync(userInput, session).ConfigureAwait(false))
+                if (await handler.TryHandleAsync(userInput, session, ux).ConfigureAwait(false))
                 {
                     handled = true;
                     break;
@@ -78,14 +91,14 @@ public static class HarnessConsole
 
             if (!handled)
             {
-                await RunAgentTurnAsync(agent, session, modeProvider, options, writer, userInput);
+                await RunAgentTurnAsync(agent, session, modeProvider, messageInjector, options, ux, userInput);
             }
 
-            writer.CurrentMode = modeProvider?.GetMode(session);
-            prompt = BuildUserPrompt(modeProvider, session);
-            userInput = await writer.ReadLineAsync(prompt);
+            ux.CurrentMode = modeProvider?.GetMode(session);
+            userInput = await ux.WaitForInputAsync();
         }
 
+        ux.Deactivate();
         System.Console.ResetColor();
         System.Console.WriteLine("Goodbye!");
     }
@@ -99,27 +112,27 @@ public static class HarnessConsole
         AIAgent agent,
         AgentSession session,
         AgentModeProvider? modeProvider,
+        MessageInjectingChatClient? messageInjector,
         HarnessConsoleOptions options,
-        ConsoleWriter writer,
+        HarnessUXContainer ux,
         string userInput)
     {
         IList<ChatMessage>? nextMessages = [new ChatMessage(ChatRole.User, userInput)];
+        IReadOnlyList<ChatMessage> lastPendingMessages = messageInjector?.GetPendingMessages(session) ?? [];
 
         while (nextMessages is not null)
         {
-            // Build observers for this invocation (may change between iterations due to mode changes).
             var observers = CreateObservers(options, modeProvider, session);
 
-            // Build run options — observers may inject ResponseFormat, etc.
             var runOptions = new AgentRunOptions();
             foreach (var observer in observers)
             {
                 observer.ConfigureRunOptions(runOptions);
             }
 
-            // Stream the response, fanning out to all observers.
-            writer.CurrentMode = modeProvider?.GetMode(session);
-            writer.WriteResponseHeader();
+            ux.CurrentMode = modeProvider?.GetMode(session);
+            ux.BeginStreaming();
+            ux.BeginStreamingOutput();
 
             try
             {
@@ -129,9 +142,9 @@ public static class HarnessConsole
                     if (modeProvider is not null)
                     {
                         string currentMode = modeProvider.GetMode(session);
-                        if (currentMode != writer.CurrentMode)
+                        if (currentMode != ux.CurrentMode)
                         {
-                            writer.CurrentMode = currentMode;
+                            ux.CurrentMode = currentMode;
                         }
                     }
 
@@ -139,7 +152,7 @@ public static class HarnessConsole
                     {
                         foreach (var observer in observers)
                         {
-                            await observer.OnContentAsync(writer, content);
+                            await observer.OnContentAsync(ux, content);
                         }
                     }
 
@@ -147,22 +160,32 @@ public static class HarnessConsole
                     {
                         foreach (var observer in observers)
                         {
-                            await observer.OnTextAsync(writer, update.Text);
+                            await observer.OnTextAsync(ux, update.Text);
                         }
                     }
+
+                    SyncQueuedMessageDisplay(messageInjector, session, ux, ref lastPendingMessages);
                 }
             }
             catch (Exception ex)
             {
-                await writer.WriteInfoLineAsync($"❌ Stream error: {ex.GetType().Name}:\n{ex}", ConsoleColor.Red);
+                await ux.WriteInfoLineAsync($"❌ Stream error: {ex.GetType().Name}:\n{ex}", ConsoleColor.Red);
             }
 
-            // Collect messages from all observers.
+            // Final sync after streaming — messages may have been consumed during the last iteration.
+            SyncQueuedMessageDisplay(messageInjector, session, ux, ref lastPendingMessages);
+
+            // Stop spinner before observer completions (which may prompt for input).
+            ux.StopSpinner();
+
+            // Close the streaming output to provide visual separation from observer output.
+            await ux.EndStreamingOutputAsync();
+
             var combinedMessages = new List<ChatMessage>();
             bool hasObserverMessages = false;
             foreach (var observer in observers)
             {
-                var messages = await observer.OnStreamCompleteAsync(writer, agent, session, options);
+                var messages = await observer.OnStreamCompleteAsync(ux, agent, session, options);
                 if (messages is { Count: > 0 })
                 {
                     combinedMessages.AddRange(messages);
@@ -170,11 +193,44 @@ public static class HarnessConsole
                 }
             }
 
-            await writer.WriteStreamFooterAsync(hasFollowUpMessages: hasObserverMessages);
+            await ux.WriteNoTextWarningAsync(hasFollowUpMessages: hasObserverMessages);
+
+            ux.EndStreaming();
+
             nextMessages = combinedMessages.Count > 0 ? combinedMessages : null;
         }
     }
 
+    /// <summary>
+    /// Synchronizes the queued items display with the message injector's pending messages.
+    /// Messages that have been consumed (drained by the service) are echoed to the output
+    /// area as regular user-input entries.
+    /// </summary>
+    private static void SyncQueuedMessageDisplay(
+        MessageInjectingChatClient? messageInjector,
+        AgentSession session,
+        HarnessUXContainer ux,
+        ref IReadOnlyList<ChatMessage> lastPendingMessages)
+    {
+        if (messageInjector is null)
+        {
+            return;
+        }
+
+        var pending = messageInjector.GetPendingMessages(session);
+
+        // If previously pending messages exceed current pending count, some were consumed.
+        int consumedCount = lastPendingMessages.Count - pending.Count;
+        for (int i = 0; i < consumedCount && i < lastPendingMessages.Count; i++)
+        {
+            string text = lastPendingMessages[i].Text ?? string.Empty;
+            ux.WriteUserInputEcho(text);
+        }
+
+        lastPendingMessages = pending;
+        ux.ShowQueuedMessages(pending);
+    }
+
     private static List<ConsoleObserver> CreateObservers(HarnessConsoleOptions options, AgentModeProvider? modeProvider, AgentSession session)
     {
         var observers = new List<ConsoleObserver>
@@ -186,7 +242,6 @@ public static class HarnessConsole
             new UsageDisplayObserver(options.MaxContextWindowTokens, options.MaxOutputTokens),
         };
 
-        // Add the appropriate output observer based on the current mode.
         if (options.EnablePlanningUx
             && modeProvider is not null
             && string.Equals(modeProvider.GetMode(session), options.PlanningModeName, StringComparison.OrdinalIgnoreCase))
@@ -200,15 +255,4 @@ public static class HarnessConsole
 
         return observers;
     }
-
-    private static string BuildUserPrompt(AgentModeProvider? modeProvider, AgentSession session)
-    {
-        if (modeProvider is not null)
-        {
-            string mode = modeProvider.GetMode(session);
-            return $"[{mode}] You: ";
-        }
-
-        return "You: ";
-    }
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/HarnessUXContainer.cs

@@ -0,0 +1,478 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Harness.ConsoleReactiveComponents;
+using Microsoft.Extensions.AI;
+
+namespace Harness.Shared.Console;
+
+/// <summary>
+/// Event arguments raised when the user submits text while the bottom panel is in
+/// streaming mode (i.e. an agent turn is in progress).
+/// </summary>
+public sealed class StreamingInputReceivedEventArgs : EventArgs
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="StreamingInputReceivedEventArgs"/> class.
+    /// </summary>
+    /// <param name="text">The submitted text.</param>
+    public StreamingInputReceivedEventArgs(string text)
+    {
+        this.Text = text;
+    }
+
+    /// <summary>
+    /// Gets the submitted text.
+    /// </summary>
+    public string Text { get; }
+}
+
+/// <summary>
+/// Façade over the harness UI: owns the <see cref="HarnessAppComponent"/>, manages
+/// its props, dispatches input submissions, and provides the high-level read/write
+/// operations used by observers, command handlers, and the harness loop.
+/// </summary>
+/// <remarks>
+/// All callers interact with the UI exclusively through this class. The underlying
+/// <see cref="HarnessAppComponent"/> and its props are an implementation detail and
+/// must not be exposed.
+/// </remarks>
+public sealed class HarnessUXContainer : IDisposable
+{
+    /// <summary>
+    /// The prompt displayed in the bottom-panel input area.
+    /// </summary>
+    private const string UserPrompt = "> ";
+
+    private readonly IReadOnlyDictionary<string, ConsoleColor>? _modeColors;
+    private readonly List<object> _outputItems = [];
+    private readonly HarnessAppComponent _appComponent;
+    private readonly object _outputLock = new();
+
+    private TaskCompletionSource<string>? _pendingInputTcs;
+    private OutputEntryType? _lastEntryType;
+    private bool _hasReceivedAnyText;
+    private OutputEntry? _currentStreamingEntry;
+    private string? _currentMode;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="HarnessUXContainer"/> class.
+    /// </summary>
+    /// <param name="placeholder">Placeholder text shown when the input is empty.</param>
+    /// <param name="initialMode">The current agent mode, used to colour the rule and prompt.</param>
+    /// <param name="inputEnabled">Whether the bottom-panel input accepts keystrokes during streaming.</param>
+    /// <param name="modeColors">Optional mapping of mode names to console colors.</param>
+    public HarnessUXContainer(
+        string placeholder,
+        string? initialMode,
+        bool inputEnabled,
+        IReadOnlyDictionary<string, ConsoleColor>? modeColors = null)
+    {
+        this._modeColors = modeColors;
+        this._currentMode = initialMode;
+
+        this._appComponent = new HarnessAppComponent(RenderOutputEntry)
+        {
+            Props = new HarnessAppComponentProps
+            {
+                ScrollItems = this._outputItems,
+                Mode = BottomPanelMode.TextInput,
+                Prompt = UserPrompt,
+                Placeholder = placeholder,
+                ModeColor = ModeColors.Get(initialMode, modeColors),
+                ModeText = initialMode,
+                InputEnabled = inputEnabled,
+            },
+        };
+
+        this._appComponent.InputSubmitted += this.OnInputSubmitted;
+    }
+
+    /// <summary>
+    /// Raised when the user submits text while the bottom panel is in streaming mode.
+    /// Subscribers typically enqueue the text into a message-injecting chat client.
+    /// </summary>
+    public event EventHandler<StreamingInputReceivedEventArgs>? StreamingInputReceived;
+
+    /// <summary>
+    /// Gets or sets the current agent mode (e.g. "plan", "execute"). Updating this
+    /// also refreshes the rule colour and bottom-panel prompt to match the new mode.
+    /// </summary>
+    public string? CurrentMode
+    {
+        get => this._currentMode;
+        set
+        {
+            this._currentMode = value;
+            this._appComponent.Props = this._appComponent.Props! with
+            {
+                ModeColor = ModeColors.Get(value, this._modeColors),
+                ModeText = value,
+            };
+            this._appComponent.Render();
+        }
+    }
+
+    /// <summary>
+    /// Performs the initial screen clear, sets the help text in the mode-and-help bar,
+    /// and adds the title to the output area.
+    /// </summary>
+    /// <param name="title">The title displayed in the console header.</param>
+    /// <param name="commandHelpTexts">The command help strings displayed in the mode-and-help bar.</param>
+    /// <param name="messageInjectionActive">Whether streaming-time message injection is enabled.</param>
+    public void Initialize(string title, IEnumerable<string> commandHelpTexts, bool messageInjectionActive)
+    {
+        // Set the help text on the mode-and-help bar (persists below the rule).
+        this._appComponent.Props = this._appComponent.Props! with
+        {
+            HelpText = string.Join(", ", commandHelpTexts),
+            ModeText = this._currentMode,
+        };
+
+        System.Console.Write(AnsiEscapes.EraseEntireScreen);
+        System.Console.Write(AnsiEscapes.EraseScrollbackBuffer);
+        this._appComponent.Render();
+
+        this.AppendOutputEntries(
+            new OutputEntry(OutputEntryType.InfoLine, $"=== {title} ===\n", ConsoleColor.White),
+            new OutputEntry(OutputEntryType.InfoLine, "\n"));
+    }
+
+    /// <summary>
+    /// Restores the cursor and exits the alternate screen, ending the interactive UI.
+    /// </summary>
+    public void Deactivate() => this._appComponent.Deactivate();
+
+    /// <summary>
+    /// Switches the bottom panel to streaming mode and starts the spinner.
+    /// </summary>
+    public void BeginStreaming()
+    {
+        this._appComponent.Props = this._appComponent.Props! with
+        {
+            Mode = BottomPanelMode.Streaming,
+            ShowSpinner = true,
+        };
+        this._appComponent.Render();
+    }
+
+    /// <summary>
+    /// Stops the spinner without leaving streaming mode. Use between the end of the
+    /// stream and any observer-driven prompts (e.g. tool approvals).
+    /// </summary>
+    public void StopSpinner()
+    {
+        this._appComponent.Props = this._appComponent.Props! with { ShowSpinner = false };
+        this._appComponent.Render();
+    }
+
+    /// <summary>
+    /// Switches the bottom panel back to text-input mode and stops the spinner.
+    /// </summary>
+    public void EndStreaming()
+    {
+        this._appComponent.Props = this._appComponent.Props! with
+        {
+            Mode = BottomPanelMode.TextInput,
+            ShowSpinner = false,
+        };
+        this._appComponent.Render();
+    }
+
+    /// <summary>
+    /// Resets per-turn streaming bookkeeping in preparation for a new agent turn.
+    /// </summary>
+    public void BeginStreamingOutput()
+    {
+        this._hasReceivedAnyText = false;
+        this._currentStreamingEntry = null;
+    }
+
+    /// <summary>
+    /// Sets the formatted usage text shown on the agent status bar.
+    /// </summary>
+    public void SetUsageText(string usageText)
+    {
+        this._appComponent.Props = this._appComponent.Props! with { UsageText = usageText };
+        this._appComponent.Render();
+    }
+
+    /// <summary>
+    /// Clears the usage text from the agent status bar.
+    /// </summary>
+    public void ClearUsageText()
+    {
+        this._appComponent.Props = this._appComponent.Props! with { UsageText = null };
+        this._appComponent.Render();
+    }
+
+    /// <summary>
+    /// Replaces the queued-message display with one entry per pending message.
+    /// </summary>
+    public void ShowQueuedMessages(IReadOnlyList<ChatMessage> pending)
+    {
+        var newQueued = new List<object>(pending.Count);
+        foreach (var msg in pending)
+        {
+            string text = msg.Text ?? string.Empty;
+            newQueued.Add(new OutputEntry(OutputEntryType.UserInput, $"  💬 {text}\n", ConsoleColor.DarkGray));
+        }
+
+        this._appComponent.Props = this._appComponent.Props! with { QueuedItems = newQueued };
+        this._appComponent.Render();
+    }
+
+    /// <summary>
+    /// Echoes a submitted user input as a regular user-input entry in the output area,
+    /// using the current mode-aware prompt prefix.
+    /// </summary>
+    /// <param name="text">The user-entered text.</param>
+    public void WriteUserInputEcho(string text)
+    {
+        this.AppendOutputEntries(new OutputEntry(
+            OutputEntryType.UserInput,
+            $"\nYou: {text}\n",
+            ConsoleColor.Green));
+    }
+
+    /// <summary>
+    /// Writes informational output as an output entry, without a trailing newline.
+    /// </summary>
+    public Task WriteInfoAsync(string text, ConsoleColor? color = null) =>
+        this.WriteInfoCoreAsync(text, color, newLine: false);
+
+    /// <summary>
+    /// Writes informational output as an output entry, followed by a newline.
+    /// </summary>
+    public Task WriteInfoLineAsync(string text, ConsoleColor? color = null) =>
+        this.WriteInfoCoreAsync(text, color, newLine: true);
+
+    private Task WriteInfoCoreAsync(string text, ConsoleColor? color, bool newLine)
+    {
+        // Add a blank line separator when transitioning from streaming text or user input.
+        string prefix = this._lastEntryType is OutputEntryType.StreamingText or OutputEntryType.StreamFooter
+            ? "\n\n  "
+            : "  ";
+
+        string fullText = newLine ? prefix + text + "\n" : prefix + text;
+        this.AppendOutputEntries(new OutputEntry(
+            OutputEntryType.InfoLine,
+            fullText,
+            color ?? ModeColors.Get(this.CurrentMode, this._modeColors)));
+        return Task.CompletedTask;
+    }
+
+    /// <summary>
+    /// Writes streaming text output from the agent. Successive calls accumulate into a
+    /// single streaming entry that is re-rendered by the text panel.
+    /// </summary>
+    public Task WriteTextAsync(string text, ConsoleColor? color = null)
+    {
+        lock (this._outputLock)
+        {
+            this._lastEntryType = OutputEntryType.StreamingText;
+            this._hasReceivedAnyText = true;
+
+            ConsoleColor effectiveColor = color ?? ModeColors.Get(this.CurrentMode, this._modeColors);
+
+            if (this._currentStreamingEntry is not null)
+            {
+                this._currentStreamingEntry = this._currentStreamingEntry with
+                {
+                    Text = this._currentStreamingEntry.Text + text,
+                };
+                this._outputItems[^1] = this._currentStreamingEntry;
+            }
+            else
+            {
+                const string Prefix = "\n";
+                this._currentStreamingEntry = new OutputEntry(OutputEntryType.StreamingText, Prefix + text, effectiveColor);
+                this._outputItems.Add(this._currentStreamingEntry);
+            }
+
+            this._appComponent.Props = this._appComponent.Props! with
+            {
+                ScrollItems = new List<object>(this._outputItems),
+            };
+        }
+
+        this._appComponent.Render();
+        return Task.CompletedTask;
+    }
+
+    /// <summary>
+    /// Writes a blank-line separator to visually close the streaming output section.
+    /// Call before observer completions so their output is visually separated.
+    /// </summary>
+    public Task EndStreamingOutputAsync()
+    {
+        lock (this._outputLock)
+        {
+            this._outputItems.Add(new OutputEntry(OutputEntryType.StreamFooter, "\n"));
+            this._currentStreamingEntry = null;
+            this._lastEntryType = OutputEntryType.StreamFooter;
+            this._appComponent.Props = this._appComponent.Props! with
+            {
+                ScrollItems = new List<object>(this._outputItems),
+            };
+        }
+
+        this._appComponent.Render();
+        return Task.CompletedTask;
+    }
+
+    /// <summary>
+    /// Shows a "(no text response from agent)" warning if no text was received
+    /// and no observer produced follow-up messages. Call after observer completions.
+    /// </summary>
+    /// <param name="hasFollowUpMessages">Whether any observer produced follow-up messages.</param>
+    public Task WriteNoTextWarningAsync(bool hasFollowUpMessages)
+    {
+        if (!this._hasReceivedAnyText && !hasFollowUpMessages)
+        {
+            this.AppendOutputEntries(new OutputEntry(
+                OutputEntryType.StreamFooter,
+                "  (no text response from agent)\n",
+                ConsoleColor.DarkYellow));
+        }
+
+        return Task.CompletedTask;
+    }
+
+    /// <summary>
+    /// Reads a line of input from the user. If <paramref name="prompt"/> is supplied
+    /// it is rendered as an info line above the input row before reading.
+    /// </summary>
+    public async Task<string?> ReadLineAsync(string? prompt = null, ConsoleColor? promptColor = null)
+    {
+        if (prompt is not null)
+        {
+            ConsoleColor ruleColor = ModeColors.Get(this.CurrentMode, this._modeColors);
+            this.AppendOutputEntries(
+                new OutputEntry(OutputEntryType.InfoLine, "\n", ruleColor),
+                new OutputEntry(OutputEntryType.InfoLine, $"  {prompt}", promptColor ?? ruleColor));
+        }
+
+        this._appComponent.Props = this._appComponent.Props! with { Mode = BottomPanelMode.TextInput };
+        this._appComponent.Render();
+
+        string input = await this.WaitForInputAsync();
+
+        this.AppendOutputEntries(new OutputEntry(
+            OutputEntryType.UserInput,
+            $"\nYou: {input}\n",
+            ConsoleColor.Green));
+
+        return input;
+    }
+
+    /// <summary>
+    /// Presents a selection prompt with the given choices and waits for the user's
+    /// selection. The title is displayed above the list in the bottom panel. After
+    /// selection the bottom panel is restored to text-input mode and both the question
+    /// and selection are echoed in the output area.
+    /// </summary>
+    public async Task<string> ReadSelectionAsync(string title, IList<string> choices)
+    {
+        this._appComponent.Props = this._appComponent.Props! with
+        {
+            Mode = BottomPanelMode.ListSelection,
+            Items = choices.ToList(),
+            ListTitle = title,
+            ListCustomTextPlaceholder = "✏️  Type a custom response...",
+        };
+        this._appComponent.Render();
+
+        string selection = await this.WaitForInputAsync();
+
+        this._appComponent.Props = this._appComponent.Props with { Mode = BottomPanelMode.TextInput };
+
+        this.AppendOutputEntries(
+            new OutputEntry(
+                OutputEntryType.InfoLine,
+                $"\n  {title}\n",
+                ModeColors.Get(this.CurrentMode, this._modeColors)),
+            new OutputEntry(
+                OutputEntryType.UserInput,
+                $"\nYou: {selection}\n",
+                ConsoleColor.Green));
+
+        return selection;
+    }
+
+    /// <summary>
+    /// Awaits the next non-streaming user input submission.
+    /// </summary>
+    public Task<string> WaitForInputAsync()
+    {
+        this._pendingInputTcs = new TaskCompletionSource<string>(TaskCreationOptions.RunContinuationsAsynchronously);
+        return this._pendingInputTcs.Task;
+    }
+
+    private void OnInputSubmitted(object? sender, InputSubmittedEventArgs e)
+    {
+        if (e.Mode == BottomPanelMode.Streaming)
+        {
+            this.StreamingInputReceived?.Invoke(this, new StreamingInputReceivedEventArgs(e.Text));
+        }
+        else
+        {
+            var waiter = this._pendingInputTcs;
+            this._pendingInputTcs = null;
+            waiter?.TrySetResult(e.Text);
+        }
+    }
+
+    /// <inheritdoc/>
+    public void Dispose()
+    {
+        this._appComponent.InputSubmitted -= this.OnInputSubmitted;
+        this._appComponent.Deactivate();
+        this._appComponent.Dispose();
+    }
+
+    /// <summary>
+    /// Renders an <see cref="OutputEntry"/> to a string with ANSI color codes.
+    /// Used as the render delegate for the <see cref="HarnessAppComponent"/>.
+    /// </summary>
+    private static string RenderOutputEntry(object item)
+    {
+        if (item is not OutputEntry entry)
+        {
+            return item?.ToString() ?? string.Empty;
+        }
+
+        if (entry.Color.HasValue)
+        {
+            return $"{AnsiEscapes.SetForegroundColor(entry.Color.Value)}{entry.Text}{AnsiEscapes.ResetAttributes}";
+        }
+
+        return entry.Text;
+    }
+
+    /// <summary>
+    /// Appends one or more output entries to the output list under lock,
+    /// updates <see cref="_lastEntryType"/> to the last entry's type, and renders.
+    /// </summary>
+    private void AppendOutputEntries(params OutputEntry[] entries)
+    {
+        lock (this._outputLock)
+        {
+            foreach (OutputEntry entry in entries)
+            {
+                this._outputItems.Add(entry);
+            }
+
+            if (entries.Length > 0)
+            {
+                this._lastEntryType = entries[^1].Type;
+            }
+
+            this._appComponent.Props = this._appComponent.Props! with
+            {
+                ScrollItems = new List<object>(this._outputItems),
+            };
+        }
+
+        this._appComponent.Render();
+    }
+}

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Harness_Shared_Console.csproj

@@ -7,12 +7,10 @@
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
 
-  <ItemGroup>
-    <PackageReference Include="Spectre.Console" />
-  </ItemGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI\Microsoft.Agents.AI.csproj" />
+    <ProjectReference Include="..\ConsoleReactiveFramework\ConsoleReactiveFramework.csproj" />
+    <ProjectReference Include="..\ConsoleReactiveComponents\ConsoleReactiveComponents.csproj" />
   </ItemGroup>
 
 </Project>

dotnet/samples/02-agents/Harness/Harness_Shared_Console/ModeColors.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Harness.Shared.Console;
+
+/// <summary>
+/// Helpers for resolving console colours associated with agent modes.
+/// </summary>
+internal static class ModeColors
+{
+    /// <summary>
+    /// Gets the console color associated with a mode name, using the provided color map.
+    /// Falls back to <see cref="ConsoleColor.Gray"/> when the mode is <see langword="null"/>
+    /// or not present in the map.
+    /// </summary>
+    /// <param name="mode">The mode name, or <see langword="null"/> if no mode is active.</param>
+    /// <param name="modeColors">Optional mapping of mode names to console colors.</param>
+    public static ConsoleColor Get(string? mode, IReadOnlyDictionary<string, ConsoleColor>? modeColors = null)
+    {
+        if (mode is null)
+        {
+            return ConsoleColor.Gray;
+        }
+
+        if (modeColors is not null && modeColors.TryGetValue(mode, out var color))
+        {
+            return color;
+        }
+
+        return ConsoleColor.Gray;
+    }
+}

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Observers/ConsoleObserver.cs

@@ -25,28 +25,28 @@ public abstract class ConsoleObserver
     /// <summary>
     /// Called for each <see cref="AIContent"/> item in the response stream.
     /// </summary>
-    /// <param name="writer">The console writer for rendering output.</param>
+    /// <param name="ux">The harness UX container, used for rendering output and interacting with the user.</param>
     /// <param name="content">The content item from the stream.</param>
-    public virtual Task OnContentAsync(ConsoleWriter writer, AIContent content) => Task.CompletedTask;
+    public virtual Task OnContentAsync(HarnessUXContainer ux, AIContent content) => Task.CompletedTask;
 
     /// <summary>
     /// Called for each text update in the response stream.
     /// </summary>
-    /// <param name="writer">The console writer for rendering output.</param>
+    /// <param name="ux">The harness UX container, used for rendering output and interacting with the user.</param>
     /// <param name="text">The text from the update.</param>
-    public virtual Task OnTextAsync(ConsoleWriter writer, string text) => Task.CompletedTask;
+    public virtual Task OnTextAsync(HarnessUXContainer ux, string text) => Task.CompletedTask;
 
     /// <summary>
     /// Called after the response stream completes. Returns messages to include in the
     /// next agent invocation, or <see langword="null"/> if no re-invocation is needed.
     /// </summary>
-    /// <param name="writer">The console writer for rendering output.</param>
+    /// <param name="ux">The harness UX container, used for rendering output and interacting with the user.</param>
     /// <param name="agent">The agent being interacted with.</param>
     /// <param name="session">The current agent session.</param>
     /// <param name="options">The console options.</param>
     /// <returns>Messages to send to the agent, or <see langword="null"/> if no action is needed.</returns>
     public virtual Task<IList<ChatMessage>?> OnStreamCompleteAsync(
-        ConsoleWriter writer,
+        HarnessUXContainer ux,
         AIAgent agent,
         AgentSession session,
         HarnessConsoleOptions options) => Task.FromResult<IList<ChatMessage>?>(null);

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Observers/ErrorDisplayObserver.cs

@@ -10,7 +10,7 @@ namespace Harness.Shared.Console.Observers;
 internal sealed class ErrorDisplayObserver : ConsoleObserver
 {
     /// <inheritdoc/>
-    public override async Task OnContentAsync(ConsoleWriter writer, AIContent content)
+    public override async Task OnContentAsync(HarnessUXContainer ux, AIContent content)
     {
         if (content is ErrorContent errorContent)
         {
@@ -25,7 +25,7 @@ internal sealed class ErrorDisplayObserver : ConsoleObserver
                 errorText += $" details: {errorContent.Details}";
             }
 
-            await writer.WriteInfoLineAsync(errorText, ConsoleColor.Red);
+            await ux.WriteInfoLineAsync(errorText, ConsoleColor.Red);
         }
     }
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Observers/PlanningOutputObserver.cs

@@ -33,7 +33,7 @@ internal sealed class PlanningOutputObserver : ConsoleObserver
     }
 
     /// <inheritdoc/>
-    public override Task OnTextAsync(ConsoleWriter writer, string text)
+    public override Task OnTextAsync(HarnessUXContainer ux, string text)
     {
         // Collect text silently instead of displaying it.
         this._textCollector.Append(text);
@@ -42,7 +42,7 @@ internal sealed class PlanningOutputObserver : ConsoleObserver
 
     /// <inheritdoc/>
     public override async Task<IList<ChatMessage>?> OnStreamCompleteAsync(
-        ConsoleWriter writer,
+        HarnessUXContainer ux,
         AIAgent agent,
         AgentSession session,
         HarnessConsoleOptions options)
@@ -64,21 +64,21 @@ internal sealed class PlanningOutputObserver : ConsoleObserver
         }
         catch (JsonException ex)
         {
-            await writer.WriteInfoLineAsync($"❌ Failed to parse planning response: {ex.Message}", ConsoleColor.Red);
-            await writer.WriteInfoLineAsync($"(raw response) {collectedText}", ConsoleColor.DarkYellow);
+            await ux.WriteInfoLineAsync($"❌ Failed to parse planning response: {ex.Message}", ConsoleColor.Red);
+            await ux.WriteInfoLineAsync($"(raw response) {collectedText}", ConsoleColor.DarkYellow);
             return null;
         }
 
         if (planningResponse is null)
         {
-            await writer.WriteInfoLineAsync("(no structured response from agent)", ConsoleColor.DarkYellow);
+            await ux.WriteInfoLineAsync("(no structured response from agent)", ConsoleColor.DarkYellow);
             return null;
         }
 
         // Render based on response type.
         if (planningResponse.Type == PlanningResponseType.Clarification)
         {
-            return AsUserMessages(await this.RenderClarificationsAndCollectResponsesAsync(writer, planningResponse));
+            return AsUserMessages(await this.RenderClarificationsAndCollectResponsesAsync(ux, planningResponse));
         }
 
         if (planningResponse.Type == PlanningResponseType.Approval)
@@ -86,48 +86,45 @@ internal sealed class PlanningOutputObserver : ConsoleObserver
             var question = planningResponse.Questions.FirstOrDefault();
             if (question is null)
             {
-                await writer.WriteInfoLineAsync("(approval response had no content)", ConsoleColor.DarkYellow);
+                await ux.WriteInfoLineAsync("(approval response had no content)", ConsoleColor.DarkYellow);
                 return null;
             }
 
-            string response = await this.RenderApprovalAndCollectResponseAsync(writer, question, options);
+            string response = await this.RenderApprovalAndCollectResponseAsync(ux, question, options);
             if (response == "Approved")
             {
                 this._modeProvider.SetMode(session, options.ExecutionModeName!);
 
-                await writer.WriteInfoLineAsync($"✅ Switched to {options.ExecutionModeName} mode.",
-                    ConsoleWriter.GetModeColor(options.ExecutionModeName, options.ModeColors));
+                await ux.WriteInfoLineAsync($"✅ Switched to {options.ExecutionModeName} mode.",
+                    ModeColors.Get(options.ExecutionModeName, options.ModeColors));
             }
 
             return AsUserMessages(response);
         }
 
-        await writer.WriteInfoLineAsync($"(unexpected response type: {planningResponse.Type})", ConsoleColor.DarkYellow);
+        await ux.WriteInfoLineAsync($"(unexpected response type: {planningResponse.Type})", ConsoleColor.DarkYellow);
         return null;
     }
 
     private static IList<ChatMessage>? AsUserMessages(string? text) =>
         text is not null ? [new ChatMessage(ChatRole.User, text)] : null;
 
-    private async Task<string?> RenderClarificationsAndCollectResponsesAsync(ConsoleWriter writer, PlanningResponse response)
+    private async Task<string?> RenderClarificationsAndCollectResponsesAsync(HarnessUXContainer ux, PlanningResponse response)
     {
         var answers = new List<string>();
 
         foreach (var question in response.Questions)
         {
-            await writer.WriteInfoLineAsync(string.Empty);
-            await writer.WriteInfoLineAsync(question.Message);
-
             string? answer;
             if (question.Choices is { Count: > 0 })
             {
-                answer = await writer.ReadSelectionAsync(
-                    "Choose an option:",
+                answer = await ux.ReadSelectionAsync(
+                    question.Message,
                     question.Choices);
             }
             else
             {
-                answer = (await writer.ReadLineAsync("Response: "))?.Trim();
+                answer = (await ux.ReadLineAsync(question.Message))?.Trim();
             }
 
             if (!string.IsNullOrWhiteSpace(answer))
@@ -139,38 +136,20 @@ internal sealed class PlanningOutputObserver : ConsoleObserver
         return answers.Count > 0 ? string.Join("\n\n", answers) : null;
     }
 
-    private async Task<string> RenderApprovalAndCollectResponseAsync(ConsoleWriter writer, PlanningQuestion question, HarnessConsoleOptions options)
+    private async Task<string> RenderApprovalAndCollectResponseAsync(HarnessUXContainer ux, PlanningQuestion question, HarnessConsoleOptions options)
     {
-        await writer.WriteInfoLineAsync(question.Message);
-
         var choices = new List<string>
         {
             "Approve and switch to execute mode",
-            "Suggest changes",
         };
 
-        string selection = await writer.ReadSelectionAsync("What would you like to do?", choices);
+        string selection = await ux.ReadSelectionAsync(question.Message, choices);
 
         if (selection == choices[0])
         {
             return "Approved";
         }
 
-        if (selection == choices[1])
-        {
-            string? feedback = await writer.ReadLineAsync(
-                "Your feedback: ",
-                ConsoleWriter.GetModeColor(options.PlanningModeName, options.ModeColors));
-
-            if (string.IsNullOrWhiteSpace(feedback))
-            {
-                // Treat empty feedback as no changes — re-prompt the agent with the plan.
-                return "No changes suggested. Please re-present the plan for approval.";
-            }
-
-            return feedback;
-        }
-
         // Custom freeform input — treat as suggested changes.
         return selection;
     }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Observers/ReasoningDisplayObserver.cs

@@ -10,11 +10,11 @@ namespace Harness.Shared.Console.Observers;
 internal sealed class ReasoningDisplayObserver : ConsoleObserver
 {
     /// <inheritdoc/>
-    public override async Task OnContentAsync(ConsoleWriter writer, AIContent content)
+    public override async Task OnContentAsync(HarnessUXContainer ux, AIContent content)
     {
         if (content is TextReasoningContent reasoning && !string.IsNullOrEmpty(reasoning.Text))
         {
-            await writer.WriteTextAsync(reasoning.Text, ConsoleColor.DarkMagenta);
+            await ux.WriteTextAsync(reasoning.Text, ConsoleColor.DarkMagenta);
         }
     }
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Observers/TextOutputObserver.cs

@@ -9,8 +9,8 @@ namespace Harness.Shared.Console.Observers;
 internal sealed class TextOutputObserver : ConsoleObserver
 {
     /// <inheritdoc/>
-    public override async Task OnTextAsync(ConsoleWriter writer, string text)
+    public override async Task OnTextAsync(HarnessUXContainer ux, string text)
     {
-        await writer.WriteTextAsync(text);
+        await ux.WriteTextAsync(text);
     }
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Observers/ToolApprovalObserver.cs

@@ -15,7 +15,7 @@ internal sealed class ToolApprovalObserver : ConsoleObserver
     private readonly List<ToolApprovalRequestContent> _approvalRequests = [];
 
     /// <inheritdoc/>
-    public override async Task OnContentAsync(ConsoleWriter writer, AIContent content)
+    public override async Task OnContentAsync(HarnessUXContainer ux, AIContent content)
     {
         if (content is ToolApprovalRequestContent approvalRequest)
         {
@@ -23,13 +23,13 @@ internal sealed class ToolApprovalObserver : ConsoleObserver
             string toolName = approvalRequest.ToolCall is FunctionCallContent fc
                 ? ToolCallFormatter.Format(fc)
                 : approvalRequest.ToolCall?.ToString() ?? "unknown";
-            await writer.WriteInfoLineAsync($"⚠️ Approval needed: {toolName}", ConsoleColor.Yellow);
+            await ux.WriteInfoLineAsync($"⚠️ Approval needed: {toolName}", ConsoleColor.Yellow);
         }
     }
 
     /// <inheritdoc/>
     public override async Task<IList<ChatMessage>?> OnStreamCompleteAsync(
-        ConsoleWriter writer,
+        HarnessUXContainer ux,
         AIAgent agent,
         AgentSession session,
         HarnessConsoleOptions options)
@@ -39,12 +39,12 @@ internal sealed class ToolApprovalObserver : ConsoleObserver
             return null;
         }
 
-        var messages = await PromptForApprovalsAsync(writer, this._approvalRequests);
+        var messages = await PromptForApprovalsAsync(ux, this._approvalRequests);
         this._approvalRequests.Clear();
         return messages;
     }
 
-    private static async Task<List<ChatMessage>?> PromptForApprovalsAsync(ConsoleWriter writer, List<ToolApprovalRequestContent> approvalRequests)
+    private static async Task<List<ChatMessage>?> PromptForApprovalsAsync(HarnessUXContainer ux, List<ToolApprovalRequestContent> approvalRequests)
     {
         if (approvalRequests.Count == 0)
         {
@@ -66,7 +66,7 @@ internal sealed class ToolApprovalObserver : ConsoleObserver
                 "Deny",
             };
 
-            string selection = await writer.ReadSelectionAsync($"🔐 Tool approval: {toolName}", choices);
+            string selection = await ux.ReadSelectionAsync($"🔐 Tool approval: {toolName}", choices);
             AIContent response = selection switch
             {
                 "Always approve this tool (any arguments)" => request.CreateAlwaysApproveToolResponse("User chose to always approve this tool"),
@@ -82,7 +82,7 @@ internal sealed class ToolApprovalObserver : ConsoleObserver
                 "Deny" => "❌ Denied",
                 _ => "✅ Approved",
             };
-            await writer.WriteInfoLineAsync($"   {action}", ConsoleColor.DarkGray);
+            await ux.WriteInfoLineAsync($"   {action}", ConsoleColor.DarkGray);
 
             responses.Add(response);
         }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Observers/ToolCallDisplayObserver.cs

@@ -11,15 +11,15 @@ namespace Harness.Shared.Console.Observers;
 internal sealed class ToolCallDisplayObserver : ConsoleObserver
 {
     /// <inheritdoc/>
-    public override async Task OnContentAsync(ConsoleWriter writer, AIContent content)
+    public override async Task OnContentAsync(HarnessUXContainer ux, AIContent content)
     {
         if (content is FunctionCallContent functionCall)
         {
-            await writer.WriteInfoLineAsync($"🔧 Calling tool: {ToolCallFormatter.Format(functionCall)}...", ConsoleColor.DarkYellow);
+            await ux.WriteInfoLineAsync($"🔧 Calling tool: {ToolCallFormatter.Format(functionCall)}...", ConsoleColor.DarkYellow);
         }
         else if (content is ToolCallContent toolCall)
         {
-            await writer.WriteInfoLineAsync($"🔧 Calling tool: {toolCall}...", ConsoleColor.DarkYellow);
+            await ux.WriteInfoLineAsync($"🔧 Calling tool: {toolCall}...", ConsoleColor.DarkYellow);
         }
     }
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Observers/UsageDisplayObserver.cs

@@ -24,19 +24,21 @@ internal sealed class UsageDisplayObserver : ConsoleObserver
     }
 
     /// <inheritdoc/>
-    public override async Task OnContentAsync(ConsoleWriter writer, AIContent content)
+    public override Task OnContentAsync(HarnessUXContainer ux, AIContent content)
     {
         if (content is UsageContent usage)
         {
             if (usage.Details is not null)
             {
-                await writer.WriteInfoLineAsync(this.FormatUsageBreakdown(usage.Details), ConsoleColor.DarkGray);
+                ux.SetUsageText(this.FormatUsageBreakdown(usage.Details));
             }
             else
             {
-                await writer.WriteInfoLineAsync("📊 Tokens —", ConsoleColor.DarkGray);
+                ux.SetUsageText("📊 Tokens —");
             }
         }
+
+        return Task.CompletedTask;
     }
 
     private string FormatUsageBreakdown(UsageDetails details)

dotnet/samples/02-agents/Harness/Harness_Shared_Console/OutputEntry.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Harness.Shared.Console;
+
+/// <summary>
+/// Represents the type of an output entry in the console conversation.
+/// </summary>
+public enum OutputEntryType
+{
+    /// <summary>User input echo (e.g. "You: hello").</summary>
+    UserInput,
+
+    /// <summary>In-progress streaming text from the agent (accumulated chunk by chunk).</summary>
+    StreamingText,
+
+    /// <summary>Informational line (tool calls, errors, usage, approval requests, etc.).</summary>
+    InfoLine,
+
+    /// <summary>Stream footer (e.g. "(no text response from agent)").</summary>
+    StreamFooter,
+
+    /// <summary>Pending injected message notification.</summary>
+    PendingMessage,
+}
+
+/// <summary>
+/// Represents a single output entry in the console conversation history.
+/// These entries are rendered by the <see cref="HarnessAppComponent"/> via its render delegate.
+/// </summary>
+/// <param name="Type">The type of output entry.</param>
+/// <param name="Text">The text content of the entry.</param>
+/// <param name="Color">Optional foreground color for rendering.</param>
+public record OutputEntry(OutputEntryType Type, string Text, ConsoleColor? Color = null);

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Spinner.cs

@@ -1,77 +0,0 @@
-// Copyright (c) Microsoft. All rights reserved.
-
-namespace Harness.Shared.Console;
-
-/// <summary>
-/// A restartable spinner that can be started and stopped multiple times.
-/// </summary>
-internal sealed class Spinner : IDisposable
-{
-    private static readonly string[] s_frames = ["⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"];
-
-    private CancellationTokenSource? _cts;
-    private Task? _task;
-
-    public void Start()
-    {
-        if (this._task is not null)
-        {
-            return;
-        }
-
-        this._cts = new CancellationTokenSource();
-        this._task = RunAsync(this._cts.Token);
-    }
-
-    public async Task StopAsync()
-    {
-        if (this._cts is null || this._task is null)
-        {
-            return;
-        }
-
-        this._cts.Cancel();
-        await this._task;
-        this._cts.Dispose();
-        this._cts = null;
-        this._task = null;
-    }
-
-    public void Dispose()
-    {
-        if (this._cts is not null && this._task is not null)
-        {
-            this._cts.Cancel();
-
-            // Block briefly to let the spinner task clean up.
-            // This prevents the background task from writing to the console after disposal.
-#pragma warning disable VSTHRD002 // Synchronous wait in Dispose is acceptable here — the spinner task completes quickly on cancellation.
-            this._task.Wait();
-#pragma warning restore VSTHRD002
-        }
-
-        this._cts?.Dispose();
-        this._cts = null;
-        this._task = null;
-    }
-
-    private static async Task RunAsync(CancellationToken cancellationToken)
-    {
-        int i = 0;
-        try
-        {
-            while (!cancellationToken.IsCancellationRequested)
-            {
-                System.Console.Write(s_frames[i % s_frames.Length]);
-                await Task.Delay(80, cancellationToken);
-                System.Console.Write("\b \b");
-                i++;
-            }
-        }
-        catch (OperationCanceledException)
-        {
-            // Clear the last spinner frame left on screen.
-            System.Console.Write("\b \b");
-        }
-    }
-}

dotnet/samples/02-agents/Harness/Harness_Step01_Research/Program.cs

@@ -135,6 +135,7 @@ AIAgent agent =
     // Build a ChatClient Pipeline
     .AsBuilder()
     .UseFunctionInvocation()                                // We are building our own stack from scratch so we need to include Function Invocation ourselves.
+    .UseMessageInjection()                                  // Allow message injection during the function call loop.
     .UsePerServiceCallChatHistoryPersistence()              // Save chat history updates to the session after each service call, rather than only at the end of the run.
     .UseAIContextProviders(new CompactionProvider(compactionStrategy))  // Add Compaction before each service call to responses so that long function invocation loops don't overflow the context.
 

dotnet/src/Microsoft.Agents.AI/ChatClient/MessageInjectingChatClient.cs

@@ -206,6 +206,31 @@ public sealed class MessageInjectingChatClient : DelegatingChatClient
         }
     }
 
+    /// <summary>
+    /// Gets a snapshot of the pending injected messages for the specified session.
+    /// </summary>
+    /// <remarks>
+    /// Returns a copy of the current pending messages that have not yet been consumed by the
+    /// injection loop. This can be used to display pending messages to the user. The returned
+    /// list is a point-in-time snapshot; messages may be consumed between calls.
+    /// </remarks>
+    /// <param name="session">The agent session to check.</param>
+    /// <returns>A read-only list of pending messages, or an empty list if none are pending.</returns>
+    public IReadOnlyList<ChatMessage> GetPendingMessages(AgentSession session)
+    {
+        Throw.IfNull(session);
+
+        if (!session.StateBag.TryGetValue<List<ChatMessage>>(PendingMessagesStateKey, out var queue) || queue is null)
+        {
+            return Array.Empty<ChatMessage>();
+        }
+
+        lock (queue)
+        {
+            return queue.Count == 0 ? Array.Empty<ChatMessage>() : queue.ToList();
+        }
+    }
+
     /// <summary>
     /// Gets or creates the pending injected messages queue from the session's <see cref="AgentSessionStateBag"/>.
     /// </summary>