Slots (Subcomponents)
Customize any part of the chat UI by overriding individual sub-components via slots.
/** * Agent factories for the Strands TypeScript showcase backend. * * `buildShowcaseAgent` is the single shared agent that serves the vast * majority of demos (the frontend differentiates each demo via * useFrontendTool / useRenderTool / useHumanInTheLoop / useAgentContext). * It mirrors the Python sibling's `build_showcase_agent` minus A2UI. * * The tool-free specialized agents (voice, byoc-hashbrown, byoc-json-render) * are mounted on dedicated sub-paths by `server.ts`. */import { readFileSync } from "node:fs";import { dirname, join } from "node:path";import { fileURLToPath } from "node:url";import { Agent, tool } from "@strands-agents/sdk";import { z } from "zod";import { StrandsAgent } from "@ag-ui/aws-strands";import type { StrandsAgentConfig } from "@ag-ui/aws-strands";import { A2UI_OPERATIONS_KEY, createSurface, updateComponents, updateDataModel,} from "@ag-ui/a2ui-toolkit";import { createModel } from "./model-factory";import { SHOWCASE_TOOLS } from "./tools";import { buildStatePrompt, salesStateFromArgs, notesStateFromArgs, stepsStateFromArgs, documentStateFromArgs, makeSubagentStateFromResult,} from "./state";import { SYSTEM_PROMPT, VOICE_SYSTEM_PROMPT, BYOC_HASHBROWN_SYSTEM_PROMPT, BYOC_JSON_RENDER_SYSTEM_PROMPT,} from "./prompts";export async function buildShowcaseAgent(): Promise<StrandsAgent> { const config: StrandsAgentConfig = { stateContextBuilder: buildStatePrompt, toolBehaviors: { // Sales pipeline lives in shared state; emit the snapshot from args. manage_sales_todos: { skipMessagesSnapshot: true, stateFromArgs: salesStateFromArgs, }, // Shared State (Read + Write) — notes panel. set_notes: { stateFromArgs: notesStateFromArgs }, // gen-ui-agent — live progress card driven by set_steps transitions. set_steps: { stateFromArgs: stepsStateFromArgs }, // shared-state-streaming — stream the document string into state. write_document: { stateFromArgs: documentStateFromArgs }, // Sub-agents — append a delegation entry carrying the actual output. research_agent: { stateFromResult: makeSubagentStateFromResult("research_agent"), }, writing_agent: { stateFromResult: makeSubagentStateFromResult("writing_agent"), }, critique_agent: { stateFromResult: makeSubagentStateFromResult("critique_agent"), }, }, }; const strandsAgent = new Agent({ model: await createModel(), systemPrompt: SYSTEM_PROMPT, tools: SHOWCASE_TOOLS, }); return new StrandsAgent({ agent: strandsAgent, name: "strands_agent", description: "A polished CopilotKit demo assistant: chat, tools, shared state, HITL, sub-agents.", config, });}/** Tool-free agent for the voice demo (transcription + basic chat). */export async function buildVoiceAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ model: await createModel(), systemPrompt: VOICE_SYSTEM_PROMPT, tools: [], }); return new StrandsAgent({ agent: strandsAgent, name: "voice_agent", description: "Simple assistant for the voice demo — no tools.", });}/** Tool-free hashbrown UI-kit envelope generator (declarative-hashbrown). */export async function buildByocHashbrownAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ model: await createModel(), systemPrompt: BYOC_HASHBROWN_SYSTEM_PROMPT, tools: [], }); return new StrandsAgent({ agent: strandsAgent, name: "byoc_hashbrown", description: "Hashbrown UI-kit envelope generator for the declarative-hashbrown demo.", });}/** Tool-free json-render flat-spec generator (declarative-json-render). */export async function buildByocJsonRenderAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ model: await createModel(), systemPrompt: BYOC_JSON_RENDER_SYSTEM_PROMPT, tools: [], }); return new StrandsAgent({ agent: strandsAgent, name: "byoc_json_render", description: "json-render flat-spec generator for the declarative-json-render demo.", });}// ---------------------------------------------------------------------------// A2UI Fixed Schema (declarative-generative-ui) — dedicated backend tool.// ---------------------------------------------------------------------------//// Unlike the dynamic A2UI demo (which relies on the adapter auto-injecting a// `generate_a2ui` tool to *generate* a surface), the fixed-schema demo wires a// single plain backend tool — `display_flight` — that returns the// `a2ui_operations` envelope (createSurface -> updateComponents ->// updateDataModel). The component tree is fixed and authored ahead of time// (./a2ui_schemas/flight_schema.json); only the *data* changes per call. The// runtime A2UIMiddleware detects the envelope in the tool result and paints.// No sub-agent, no generation, no `generate_a2ui` injection.//// The schema's component names + data paths must match the showcase frontend// catalog at src/app/demos/a2ui-fixed-schema/a2ui/{definitions,renderers,// catalog}.ts — catalog id `copilotkit://flight-fixed-catalog`. This mirrors// the canonical langgraph-python demo (src/agents/a2ui_fixed.py).const _A2UI_DIR = dirname(fileURLToPath(import.meta.url));const A2UI_FIXED_CATALOG_ID = "copilotkit://flight-fixed-catalog";const A2UI_FIXED_SURFACE_ID = "flight-fixed-schema";// Fixed, pre-authored component layout. Loaded from JSON so it can be authored// and reviewed independently of the agent code.const FLIGHT_SCHEMA: Array<Record<string, unknown>> = JSON.parse( readFileSync(join(_A2UI_DIR, "a2ui_schemas", "flight_schema.json"), "utf-8"),);const A2UI_FIXED_SYSTEM_PROMPT = "You help users find flights. When asked about a flight, call " + "`display_flight` exactly ONCE with origin, destination, airline, and " + 'price. Use short airport codes (e.g. "SFO", "JFK") for ' + 'origin/destination and a price string like "$289". The tool\'s return ' + "value is an A2UI surface descriptor — the flight card is already rendered " + "to the user; do NOT call `display_flight` again for the same trip and do " + "NOT repeat the flight details in text. After the tool returns, reply with " + "one short confirmation sentence and stop.";/** * Dedicated agent for the A2UI fixed-schema demo. Returns the envelope as a * plain OBJECT (not a JSON string): the Strands TS SDK wraps an object * tool-return in a `json` content block the adapter reads and re-stringifies * into the TOOL_CALL_RESULT the client A2UIMiddleware scans for * `a2ui_operations`. (A bare string return lands in no content block and the * result comes through empty — unlike the Python SDK, which wraps strings.) */export async function buildA2uiFixedSchemaAgent(): Promise<StrandsAgent> { const displayFlight = tool({ name: "display_flight", description: "Show a flight card for the given trip. Use short airport codes " + '(e.g. "SFO", "JFK") for origin/destination and a price string like ' + '"$289". After this tool returns, the flight card is already rendered ' + "to the user via the A2UI surface — do NOT call it again for the same " + "flight; reply with one short confirmation sentence and stop.", inputSchema: z.object({ origin: z.string().describe('Origin airport code, e.g. "SFO".'), destination: z.string().describe('Destination airport code, e.g. "JFK".'), airline: z.string().describe('Airline name, e.g. "United".'), price: z.string().describe('Price string, e.g. "$289".'), }), callback: ({ origin, destination, airline, price }) => ({ [A2UI_OPERATIONS_KEY]: [ createSurface(A2UI_FIXED_SURFACE_ID, A2UI_FIXED_CATALOG_ID), updateComponents(A2UI_FIXED_SURFACE_ID, FLIGHT_SCHEMA), updateDataModel(A2UI_FIXED_SURFACE_ID, { origin, destination, airline, price, }), ], }), }); const strandsAgent = new Agent({ // Chat Completions API: the Responses adapter buffers tool-call argument // deltas, which would defeat A2UI's progressive surface streaming. model: await createModel({ openaiApi: "chat" }), systemPrompt: A2UI_FIXED_SYSTEM_PROMPT, tools: [displayFlight], }); return new StrandsAgent({ agent: strandsAgent, name: "a2ui_fixed_schema", description: "A2UI surface from a fixed, pre-authored schema (direct backend tool)", });}// ---------------------------------------------------------------------------// A2UI Dynamic Schema (declarative-gen-ui) — adapter auto-injects generate_a2ui.// ---------------------------------------------------------------------------//// Unlike the fixed-schema demo (which wires a `display_flight` tool returning a// pre-authored envelope), the dynamic demo lets the agent *generate* the// surface layout on the fly. The Next.js route// (app/api/copilotkit-declarative-gen-ui/route.ts) sets// `a2ui: { injectA2UITool: true, defaultCatalogId: "declarative-gen-ui-catalog" }`;// the runtime forwards the flag, the Strands adapter auto-injects a// `generate_a2ui` tool and drives a secondary render planner. The// `config.a2ui` block below supplies the catalog id stamped into generated// surfaces and the composition guide that teaches the planner the page's// catalog. Mirrors the ag-ui dynamic-schema reference example.//// The compositionGuide MUST describe the catalog the page registers at// src/app/demos/declarative-gen-ui/a2ui/{definitions,renderers,catalog}.ts// (catalog id `declarative-gen-ui-catalog`): Card / StatusBadge / Metric /// InfoRow / PrimaryButton / PieChart / BarChart / DataTable, composed inside// the basic catalog's Row / Column / Text (`includeBasicCatalog: true`).//// Grounding dataset + composition rules are kept in spirit with the frontend// `sales-context.ts` (SALES_DATASET + COMPOSITION_RULES) the page registers via// `useAgentContext`. The frontend context steers the PRIMARY agent; this// compositionGuide is the channel the adapter feeds to the secondary// `render_a2ui` planner (it gets `guidelines`, not the frontend App Context),// so the planner is self-contained.const A2UI_DYNAMIC_CATALOG_ID = "declarative-gen-ui-catalog";const A2UI_DYNAMIC_SALES_DATASET = `Vantage Threads (fictional B2B apparel company) — Q2 sales data. Ground every visual in these numbers; invent only plausible details consistent with them.- Quarterly revenue: $4.2M (up 12% QoQ). New customers: 186 (up 8%). Win rate: 31% (down 2pts). Avg deal size: $22.6k (up 5%).- Revenue by region: North America $1.9M, EMEA $1.3M, APAC $720k, LATAM $280k.- Monthly revenue: Jan $1.21M, Feb $1.34M, Mar $1.65M, Apr $1.38M, May $1.42M, Jun $1.40M.- Reps (vs quota): Dana Whitfield 124%, Marcus Lee 108%, Priya Sharma 97%, Tom Okafor 88%, Elena Vasquez 71%.- At-risk: total $615k ARR across 3 accounts — Northwind Retail ($340k renewal, no contact 6 weeks; severity high), Cascadia Outfitters ($180k, champion left; severity medium), Atlas Goods ($95k, stalled legal review; severity medium).- Biggest account: Meridian Apparel Group — owner Dana Whitfield, region North America, ARR $612k, renewal Sep 30, last contact 3 days ago, health green, 4 open opportunities worth $210k.- Meridian revenue by product line: Outerwear $260k, Footwear $180k, Accessories $112k, Custom $60k.`;const A2UI_DYNAMIC_COMPOSITION_RULES = `Use ONLY these exact component names (the registered catalog — any other name fails to render): Card, Column, Row, Text, Metric, PieChart, BarChart, DataTable, StatusBadge, InfoRow, PrimaryButton. The single-value KPI tile component is named exactly "Metric" (NOT "MetricTile" or "MetricCard").Pick A2UI components by the shape of the question — never ask which chart the user wants:1. Overall snapshot / "sales dashboard" → a Column (gap 16) whose first child is a Row (gap 16) of 4 Metric components (each with trend + trendValue), followed by a Row with a PieChart (revenue by region) next to a BarChart (monthly revenue, all six months Jan-Jun). Do NOT wrap the dashboard in a surrounding Card — the charts carry their own card chrome. Do NOT use StatusBadge, DataTable, or InfoRow here.2. Rep / team performance → a Column (gap 16) with a Card containing a DataTable (columns: rep, attainment, pipeline) next to or above a BarChart of quota attainment % per rep — no StatusBadge or InfoRow.3. Risk / health checks → a Column (gap 16): first a Row (gap 16) of 3 Metric components (ARR at risk $615k trend down, accounts at risk 3, biggest exposure Northwind $340k), then a Row (gap 16) with one compact Card per at-risk account (title = account name, subtitle = ARR at stake) containing a StatusBadge (error for high severity, warning otherwise) above a one-line Text with the reason and the recommended next action — no DataTable or InfoRow.4. Single account/entity details → a Row (gap 16) with a Card of InfoRow facts (owner, region, ARR, renewal date, last contact) next to a PieChart of that account's revenue by product line — no DataTable or StatusBadge.5. Part-of-whole follow-ups → PieChart; trends or comparisons over time/categories → BarChart.Compose generously — a dashboard should feel like a real analytics product, not a single widget.`;const A2UI_DYNAMIC_COMPOSITION_GUIDE = `${A2UI_DYNAMIC_SALES_DATASET}\n\n${A2UI_DYNAMIC_COMPOSITION_RULES}`;// Mirrors the langgraph-python demo's a2ui_dynamic.py SYSTEM_PROMPT.const A2UI_DYNAMIC_SYSTEM_PROMPT = "You are the embedded sales analyst for Vantage Threads, the fictional " + "B2B apparel company described in your App Context. Answer every " + "business question by calling `generate_a2ui` to draw a rich visual " + "surface, and keep the chat reply to one short sentence.\n\n" + "Ground every number in the sales dataset from App Context — never " + "invent figures that contradict it. Follow the dashboard composition " + "rules from App Context when choosing components: pick the component " + "by the shape of the question (snapshot → composed KPI dashboard with " + "charts; team performance → table; risk → status badges; single " + "account → info rows; part-of-whole → pie; trend/comparison → bar). " + "Never ask the user which chart they want. `generate_a2ui` takes no " + "arguments and handles the rendering automatically. Compose " + "generously — a dashboard should feel like a real analytics product, " + "not a single widget.";/** * Dedicated agent for the A2UI dynamic-schema demo. Wires NO `generate_a2ui` * tool — the runtime's `injectA2UITool: true` makes the adapter auto-inject it * and drive a secondary render planner to GENERATE the surface. */export async function buildA2uiDynamicAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ // Chat Completions API: the Responses adapter buffers tool-call argument // deltas, which would defeat A2UI's progressive surface streaming. model: await createModel({ openaiApi: "chat" }), systemPrompt: A2UI_DYNAMIC_SYSTEM_PROMPT, }); const config: StrandsAgentConfig = { a2ui: { defaultCatalogId: A2UI_DYNAMIC_CATALOG_ID, guidelines: { compositionGuide: A2UI_DYNAMIC_COMPOSITION_GUIDE }, }, }; return new StrandsAgent({ agent: strandsAgent, name: "a2ui_dynamic_schema", description: "Dynamic A2UI surfaces generated on the fly (auto-injected tool)", config, });}// ---------------------------------------------------------------------------// A2UI Error Recovery (a2ui-recovery) — adapter auto-injects + runs recovery.// ---------------------------------------------------------------------------//// Same auto-injected dynamic-schema setup as buildA2uiDynamicAgent, but the// aimock fixtures force the inner render_a2ui to emit free-form/sloppy args// (heal pill) or a structurally-invalid surface on every attempt (exhaust// pill). The Strands adapter runs the toolkit validate->retry recovery loop on// its auto-inject path (default 3 attempts) and returns the// a2ui_recovery_exhausted hard-fail envelope when the cap is hit — so this// agent wires NO tool, unlike the langgraph/ADK siblings (which own the tool// explicitly via getA2UITools + injectA2UITool:false). Mirrors the ag-ui dojo// aws-strands recovery example./** * Dedicated agent for the A2UI error-recovery demo. Wires NO `generate_a2ui` * tool — the runtime's `injectA2UITool: true` makes the adapter auto-inject it, * drive the secondary render planner, and run the recovery loop. */export async function buildA2uiRecoveryAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ // Chat Completions API: the Responses adapter buffers tool-call argument // deltas, which would defeat A2UI's progressive surface streaming. model: await createModel({ openaiApi: "chat" }), systemPrompt: A2UI_DYNAMIC_SYSTEM_PROMPT, }); const config: StrandsAgentConfig = { a2ui: { defaultCatalogId: A2UI_DYNAMIC_CATALOG_ID, guidelines: { compositionGuide: A2UI_DYNAMIC_COMPOSITION_GUIDE }, }, }; return new StrandsAgent({ agent: strandsAgent, name: "a2ui_recovery", description: "Dynamic A2UI with automatic error recovery (auto-injected tool)", config, });}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:
- Tailwind classes — pass a string to add/override CSS classes
- Props override — pass an object to override specific props on the default component
- 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:
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:
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:
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.
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.
<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.
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:
<CopilotChat
messageView={{
assistantMessage: {
toolbar: CustomToolbar,
copyButton: CustomCopyButton,
},
userMessage: CustomUserMessage,
}}
/>Three levels deep#
Override a specific button inside the assistant message toolbar:
<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.
<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:
| Slot | Description |
|---|---|
messageView | The message list container. |
scrollView | The scroll container with auto-scroll behavior. |
input | The text input area with send/transcribe controls. |
suggestionView | The suggestion pills shown below messages. |
welcomeScreen | The initial empty-state screen (pass false to disable). |
CopilotSidebar and CopilotPopup also have:
| Slot | Description |
|---|---|
header | The modal header bar. |
toggleButton | The open/close toggle button. |