CopilotKit

Slots (Subcomponents)

Customize any part of the chat UI by overriding individual sub-components via slots.

using System.ClientModel;using System.Net.Http;using System.Text.Json.Serialization;using Microsoft.Agents.AI.Hosting.AGUI.AspNetCore;using Microsoft.AspNetCore.Http.Json;using Microsoft.Extensions.Options;using OpenAI;var builder = WebApplication.CreateBuilder(args);builder.Services.ConfigureHttpJsonOptions(options =>{    // Beautiful-chat types (shipped) + the full-column Sales/Flight/parity types    // ported by the family slots. Both source-generated contexts are chained so    // every feature agent's tool I/O serializes through the fast path.    options.SerializerOptions.TypeInfoResolverChain.Add(BeautifulChatSerializerContext.Default);    options.SerializerOptions.TypeInfoResolverChain.Add(SalesAgentSerializerContext.Default);    // Serialize enum types as their member-name strings rather than numeric    // ordinals (matches the Framework column's wire format).    options.SerializerOptions.Converters.Add(new JsonStringEnumConverter());});builder.Services.AddAGUI();// STOPGAP: IHttpContextAccessor lets AimockHeaderPolicy read the current// request's forwarded x-* headers (stashed on HttpContext.Items by// AimockHeaderMiddleware) at outbound-LLM-call time. HttpContext flows across// the AG-UI SSE-pump ExecutionContext boundary, unlike a middleware-set// AsyncLocal. TODO(copilotkit-sdk-dotnet): migrate to SDK-level header propagation.builder.Services.AddHttpContextAccessor();var app = builder.Build();// STOPGAP: seed the static accessor the outbound header-forwarding policy reads// (the policy is created without DI, mirroring CvDiag.Logger).AimockHeaderPolicy.HttpContextAccessor = app.Services.GetRequiredService<IHttpContextAccessor>();// Forward D5/aimock x-* headers from incoming AG-UI requests to outgoing// OpenAI calls until the .NET SDK owns this propagation centrally.app.UseMiddleware<AimockHeaderMiddleware>();// CVDIAG: backend flap-observability emitter (plan unit L1-F; spec §3). OFF by// default (CVDIAG_BACKEND_EMITTER=on to arm). Seed the static singleton the// outbound LLM policy reads (created without DI), then register the// request-pipeline instrumentation AFTER AimockHeaderMiddleware so the forwarded// x-* correlation headers are already captured for this request.CvdiagBackend.Instance = new CvdiagBackend();app.UseMiddleware<CvdiagInstrumentationMiddleware>();var loggerFactory = app.Services.GetRequiredService<ILoggerFactory>();// CVDIAG: seed the static logger used by AimockHeaderPolicy (created without DI)// to emit the outbound-LLM header-forwarding breadcrumb.CvDiag.Logger = loggerFactory.CreateLogger("CvDiag");var jsonOptions = app.Services.GetRequiredService<IOptions<JsonOptions>>().Value.SerializerOptions;// Single shared OpenAIClient for the whole column. Built once via the harness// ApiKeyResolver (env OPENAI_API_KEY -> config OPENAI_API_KEY -> GitHubToken,// fail-fast for non-mock endpoints) so EVERY feature agent hits the same// upstream with the same credential resolution — no per-feature GitHubToken// dance. Threaded into each feature factory's ctor. See the W0 contract §1.var openAiClient = CreateOpenAiClient(builder.Configuration, loggerFactory.CreateLogger("Program"));// ── Root agentic-chat agent (the Sales pipeline agent) ──────────────────────// agentic-chat, chat-slots, chat-customization-css, prebuilt-{sidebar,popup},// frontend-tools{,-async}, headless-simple, shared-state-read, and the two// tool-rendering catch-all demos all proxy to this root agent via the shared// Next.js `copilotkit/` runtime route.var salesFactory = new SalesAgentFactory(builder.Configuration, openAiClient, jsonOptions, loggerFactory);app.MapAGUI("/", salesFactory.CreateSalesAgent());// ── D5 parity agents (one factory hosts the parity-feature surface) ─────────var d5ParityFactory = new D5ParityAgentFactory(openAiClient, loggerFactory, jsonOptions);app.MapAGUI("/headless-complete", d5ParityFactory.CreateHeadlessCompleteAgent());app.MapAGUI("/voice", d5ParityFactory.CreateVoiceAgent());app.MapAGUI("/gen-ui-agent", d5ParityFactory.CreateGenUiAgent());app.MapAGUI("/gen-ui-tool-based", d5ParityFactory.CreateGenUiToolBasedAgent());app.MapAGUI("/shared-state-streaming", d5ParityFactory.CreateSharedStateStreamingAgent());app.MapAGUI("/readonly-state-agent-context", d5ParityFactory.CreateReadonlyStateAgentContext());app.MapAGUI("/tool-rendering", d5ParityFactory.CreateToolRenderingAgent(reasoning: false));app.MapAGUI("/tool-rendering-reasoning-chain", d5ParityFactory.CreateToolRenderingAgent(reasoning: true));// ── Interrupt agent (NOT-SUPPORTED, wired for parity) ───────────────────────// gen-ui-interrupt and interrupt-headless share this single backend; the// differentiation is on the frontend (in-chat picker vs. headless button grid).// Marked not_supported in manifest.yaml (skipped-incapable) pending a// @copilotkit/react-core resume-path fix — wired here so the column is 1:1.var interruptFactory = new InterruptAgentFactory(builder.Configuration, openAiClient, loggerFactory, jsonOptions);app.MapAGUI("/interrupt-adapted", interruptFactory.CreateInterruptAgent());// ── Multimodal (raw MapPost — the AG-UI adapter rejects content arrays) ─────// Parses the request body directly and emits the small AG-UI SSE event subset// the chat UI needs for text streaming over a vision-capable chat client.app.MapPost("/multimodal", (HttpContext context) => MultimodalEndpoint.HandleAsync(    context,    salesFactory.CreateMultimodalChatClient(),    loggerFactory.CreateLogger("MultimodalEndpoint")));// ── Beautiful Chat flagship demo (shipped) ──────────────────────────────────var beautifulChatFactory = new BeautifulChatAgentFactory(    builder.Configuration,    openAiClient,    jsonOptions,    loggerFactory.CreateLogger<BeautifulChatAgentFactory>());app.MapAGUI("/beautiful-chat", beautifulChatFactory.Create());// ── Agent Config (wraps a neutral inner agent in AgentConfigAgent) ──────────app.MapAGUI("/agent-config", salesFactory.CreateAgentConfigAgent());// ── Reasoning (reasoning-default + reasoning-custom share this backend) ─────app.MapAGUI("/reasoning", salesFactory.CreateReasoningAgent());// ── Declarative Gen UI (A2UI canonical BYOC) ────────────────────────────────var declarativeGenUiAgent = new DeclarativeGenUiAgent(builder.Configuration, openAiClient, loggerFactory, jsonOptions);app.MapAGUI("/declarative-gen-ui", declarativeGenUiAgent.Create());// ── A2UI fixed-schema demo ──────────────────────────────────────────────────var a2uiFixedSchemaAgent = new A2uiFixedSchemaAgent(builder.Configuration, openAiClient, loggerFactory, jsonOptions);app.MapAGUI("/a2ui-fixed-schema", a2uiFixedSchemaAgent.Create());// ── Open Generative UI — basic + advanced ───────────────────────────────────var openGenUiFactory = new OpenGenUiAgentFactory(openAiClient);app.MapAGUI("/open-gen-ui", openGenUiFactory.CreateAgent());var openGenUiAdvancedFactory = new OpenGenUiAdvancedAgentFactory(openAiClient);app.MapAGUI("/open-gen-ui-advanced", openGenUiAdvancedFactory.CreateAgent());// ── BYOC demos (hashbrown + json-render) ────────────────────────────────────var byocHashbrownFactory = new ByocHashbrownAgentFactory(openAiClient, loggerFactory);app.MapAGUI("/byoc-hashbrown", byocHashbrownFactory.CreateAgent());var byocJsonRenderFactory = new ByocJsonRenderAgentFactory(openAiClient, loggerFactory);app.MapAGUI("/byoc-json-render", byocJsonRenderFactory.CreateAgent());// ── MCP Apps demo ───────────────────────────────────────────────────────────var mcpAppsFactory = new McpAppsAgentFactory(openAiClient, loggerFactory);app.MapAGUI("/mcp-apps", mcpAppsFactory.CreateMcpAppsAgent());// ── In-app HITL demo (frontend tools + async HITL) ──────────────────────────var hitlInAppFactory = new HitlInAppAgentFactory(openAiClient, loggerFactory);app.MapAGUI("/hitl-in-app", hitlInAppFactory.CreateHitlInAppAgent());// ── In-chat HITL demo (useHumanInTheLoop) ───────────────────────────────────var hitlInChatFactory = new HitlInChatAgentFactory(openAiClient, loggerFactory);app.MapAGUI("/hitl-in-chat", hitlInChatFactory.CreateHitlInChatAgent());// ── Shared State (Read + Write) demo ────────────────────────────────────────var sharedStateReadWriteFactory = new SharedStateReadWriteAgentFactory(openAiClient, loggerFactory, jsonOptions);app.MapAGUI("/shared-state-read-write", sharedStateReadWriteFactory.CreateAgent());// ── Sub-Agents demo (supervisor delegates to research/writing/critique) ─────var subagentsFactory = new SubagentsAgentFactory(openAiClient, loggerFactory, jsonOptions);app.MapAGUI("/subagents", subagentsFactory.CreateAgent());app.MapGet("/health", () => Results.Ok(new { status = "ok" }));await app.RunAsync();static OpenAIClient CreateOpenAiClient(IConfiguration configuration, ILogger logger){    // Use the shared resolver so the primary OpenAI client and the secondary    // tool-calling HTTP client (A2uiSecondaryToolCaller) agree on which upstream    // endpoint to hit (see ApiKeyResolver for the env/config precedence and the    // non-mock fail-fast).    var endpoint = ApiKeyResolver.ResolveEndpoint(configuration);    var endpointEnv = Environment.GetEnvironmentVariable("OPENAI_BASE_URL");    var endpointConfig = configuration["OPENAI_BASE_URL"];    if (!string.IsNullOrEmpty(endpointEnv))    {        logger.LogInformation("Using OpenAI endpoint from OPENAI_BASE_URL env: {Endpoint}", endpoint);    }    else if (!string.IsNullOrEmpty(endpointConfig))    {        logger.LogInformation("Using OpenAI endpoint from configuration OPENAI_BASE_URL: {Endpoint}", endpoint);    }    else    {        logger.LogInformation("OPENAI_BASE_URL not set; using default OpenAI endpoint: {Endpoint}", endpoint);    }    var apiKey = ApiKeyResolver.ResolveApiKey(configuration, logger);    return new OpenAIClient(        new ApiKeyCredential(apiKey),        AimockHeaderPolicy.CreateOpenAIClientOptions(endpoint));}public class WeatherInfo{    [JsonPropertyName("temperature")]    public int Temperature { get; init; }    [JsonPropertyName("conditions")]    public string Conditions { get; init; } = string.Empty;    [JsonPropertyName("humidity")]    public int Humidity { get; init; }    [JsonPropertyName("wind_speed")]    public int WindSpeed { get; init; }    [JsonPropertyName("feels_like")]    public int FeelsLike { get; init; }    [JsonPropertyName("city")]    public string City { get; init; } = string.Empty;}public partial class Program { }[JsonSerializable(typeof(WeatherInfo))][JsonSerializable(typeof(BeautifulChatTodo))][JsonSerializable(typeof(List<BeautifulChatTodo>))][JsonSerializable(typeof(BeautifulChatFlight))][JsonSerializable(typeof(List<BeautifulChatFlight>))]internal partial class BeautifulChatSerializerContext : JsonSerializerContext{}

What is this?#

Every CopilotKit chat component is built from composable slots, named sub-components you can override individually. The slot system gives you three levels of customization without needing to rebuild the entire UI:

  1. Tailwind classes — pass a string to add/override CSS classes
  2. Props override — pass an object to override specific props on the default component
  3. Custom component — pass your own React component to fully replace a slot

Slots are recursive: you can drill into nested sub-components at any depth.

What it looks like in code#

The chat-slots cell above overrides three slots on a single <CopilotChat> — the welcome screen, the assistant message card, and the input's disclaimer. Each slot is just a prop; the demo extracts them into locals so the override points are easy to see.

Welcome screen slot#

The welcomeScreen prop replaces the empty-state view shown before the first message is sent. The demo swaps in a gradient card that still renders the default input and suggestions:

slot-overrides.snippet.tsx
import type {  CopilotChatAssistantMessage,  CopilotChatInput,  CopilotChatView,} from "@copilotkit/react-core/v2";declare const CustomWelcomeScreen: React.ComponentType;declare const CustomAssistantMessage: React.ComponentType;declare const CustomDisclaimer: React.ComponentType;export function ChatSlotsTeachingExtracts() {  const welcomeScreen =    CustomWelcomeScreen as unknown as typeof CopilotChatView.WelcomeScreen;

Assistant message slot#

Drill into messageView={{ assistantMessage: ... }} to wrap every assistant response. The cell wraps the default component with a tinted card and a small "slot" badge so you can see the override is active during the message flow:

slot-overrides.snippet.tsx
import type {  CopilotChatAssistantMessage,  CopilotChatInput,  CopilotChatView,} from "@copilotkit/react-core/v2";declare const CustomWelcomeScreen: React.ComponentType;declare const CustomAssistantMessage: React.ComponentType;declare const CustomDisclaimer: React.ComponentType;export function ChatSlotsTeachingExtracts() {  const welcomeScreen =    CustomWelcomeScreen as unknown as typeof CopilotChatView.WelcomeScreen;  const messageView = {    assistantMessage:      CustomAssistantMessage as unknown as typeof CopilotChatAssistantMessage,  };

Disclaimer slot#

The input={{ disclaimer: ... }} sub-slot lets you replace the small text shown below the input. The demo uses it to display a visibly tagged disclaimer so reviewers can tell the override is still in effect once the welcome screen is gone:

slot-overrides.snippet.tsx
import type {  CopilotChatAssistantMessage,  CopilotChatInput,  CopilotChatView,} from "@copilotkit/react-core/v2";declare const CustomWelcomeScreen: React.ComponentType;declare const CustomAssistantMessage: React.ComponentType;declare const CustomDisclaimer: React.ComponentType;export function ChatSlotsTeachingExtracts() {  const welcomeScreen =    CustomWelcomeScreen as unknown as typeof CopilotChatView.WelcomeScreen;  const messageView = {    assistantMessage:      CustomAssistantMessage as unknown as typeof CopilotChatAssistantMessage,  };  const input = {    disclaimer:      CustomDisclaimer as unknown as typeof CopilotChatInput.Disclaimer,  };

Tailwind Classes#

The simplest way to customize a slot. Pass a Tailwind class string and it will be merged with the default component's classes.

page.tsx
import { CopilotChat } from "@copilotkit/react-core/v2";

export function Chat() {
  return (
    <CopilotChat
      messageView="bg-gray-50 dark:bg-gray-900 p-4"
      input="border-2 border-blue-400 rounded-xl"
    />
  );
}

Props Override#

Pass an object to override specific props on the default component. This is useful for adding className, event handlers, data attributes, or any other prop the default component accepts.

page.tsx
<CopilotChat
  messageView={{
    className: "my-custom-messages",
    "data-testid": "message-view",
  }}
  input={{ autoFocus: true }}
/>

Custom Components#

For full control, pass your own React component. It receives all the same props as the default component.

page.tsx
import { CopilotChat } from "@copilotkit/react-core/v2";

const CustomMessageView = ({ messages, isRunning }) => (
  <div className="space-y-4 p-6">
    {messages?.map((msg) => (
      <div key={msg.id} className={msg.role === "user" ? "text-right" : "text-left"}>
        {msg.content}
      </div>
    ))}
    {isRunning && <div className="animate-pulse">Thinking...</div>}
  </div>
);

export function Chat() {
  return <CopilotChat messageView={CustomMessageView} />;
}

Nested Slots (Drill-Down)#

Slots are recursive. You can customize sub-components at any depth by nesting objects.

Two levels deep#

Override the assistant message's toolbar within the message view:

page.tsx
<CopilotChat
  messageView={{
    assistantMessage: {
      toolbar: CustomToolbar,
      copyButton: CustomCopyButton,
    },
    userMessage: CustomUserMessage,
  }}
/>

Three levels deep#

Override a specific button inside the assistant message toolbar:

page.tsx
<CopilotChat
  messageView={{
    assistantMessage: {
      copyButton: ({ onClick }) => (
        <button onClick={onClick}>Copy</button>
      ),
    },
  }}
/>

Labels#

Customize any text string in the UI via the labels prop. This is a separate convenience prop on CopilotChat, CopilotSidebar, and CopilotPopup, not part of the slot system.

page.tsx
<CopilotChat
  labels={{
    chatInputPlaceholder: "Ask your agent anything...",
    welcomeMessageText: "How can I help you today?",
    chatDisclaimerText: "AI responses may be inaccurate.",
  }}
/>

Available Slots#

CopilotChat / CopilotSidebar / CopilotPopup#

These are the root-level slot props available on all chat components:

SlotDescription
messageViewThe message list container.
scrollViewThe scroll container with auto-scroll behavior.
inputThe text input area with send/transcribe controls.
suggestionViewThe suggestion pills shown below messages.
welcomeScreenThe initial empty-state screen (pass false to disable).

CopilotSidebar and CopilotPopup also have:

SlotDescription
headerThe modal header bar.
toggleButtonThe open/close toggle button.

On this page

What is this?What it looks like in codeWelcome screen slotAssistant message slotDisclaimer slotTailwind ClassesProps OverrideCustom ComponentsNested Slots (Drill-Down)Two levels deepThree levels deepLabelsAvailable SlotsCopilotChat / CopilotSidebar / CopilotPopup