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CopilotKit's Built-in Agent

CLI Start Command

Copy-paste command to clone the canonical starter

CopilotKit's Built-in Agent

Pre-Built: CopilotChat

Vanilla CopilotChat with three starter-prompt suggestions — the minimum-viable surface for free-form chat

CopilotKit's Built-in Agent

Chat Customization: CSS

Default CopilotChat re-themed via CopilotKitCSSProperties

CopilotKit's Built-in Agent

Generative UI: Tool Rendering (Default)

Out-of-the-box tool rendering — backend defines the tools; the frontend adds zero custom renderers and relies on CopilotKit's built-in default UI

CopilotKit's Built-in Agent

Generative UI: Tool Rendering (Catch-all)

Single branded wildcard renderer via useDefaultRenderTool — the same app-designed card paints every tool call

CopilotKit's Built-in Agent

Frontend Tools: In-app Actions

Agent invokes client-side handlers registered with useFrontendTool

CopilotKit's Built-in Agent

Frontend Tools: Async

useFrontendTool with an async handler — agent awaits a client-side async operation (simulated notes DB query) and uses the returned result

CopilotKit's Built-in Agent

Human In the Loop: In-chat

Time-slot picker rendered inline in the chat via `useHumanInTheLoop` — the agent requests user input, the frontend renders a TimePickerCard, and the user's choice resumes the agent.

CopilotKit's Built-in Agent

Human in the Loop: In-app

Agent requests approval via useFrontendTool with an async handler; the approval UI pops up as an app-level modal OUTSIDE the chat, and a completion callback resolves the pending tool Promise with the user's decision

CopilotKit's Built-in Agent

Generative UI: Tool Rendering (Custom)

Custom per-tool renderers (WeatherCard, FlightListCard) plus a wildcard catch-all for every other tool

CopilotKit's Built-in Agent

Generative UI: Tool calls + reasoning

Per-tool renderers (WeatherCard, FlightListCard, custom catchall) interleaved with a reasoningMessage slot rendering the agent's reasoning tokens — combines reasoning-display + tool-rendering in one chat surface.

CopilotKit's Built-in Agent

Generative UI: useComponent

Agent uses tools to trigger UI generation

CopilotKit's Built-in Agent

Generative UI: Agent State

Agent-state-driven Gen UI — the agent plans a live step list via Command(update={steps}); the frontend subscribes through useAgent and renders the steps inside CopilotChat's messageView.children slot.

CopilotKit's Built-in Agent

Shared State: Streaming

Per-token state delta streaming from agent to UI

CopilotKit's Built-in Agent

Shared State: Read + Write

Bidirectional shared state — UI writes preferences via agent.setState; agent writes notes via a Command-returning tool

CopilotKit's Built-in Agent

Shared State: Read-only

Recipe editor publishes form state via agent.setState; the agent reads the recipe context but does not mutate it (no backend tool — neutral default agent).

CopilotKit's Built-in Agent

Sub-Agents

Multiple agents with visible task delegation

CopilotKit's Built-in Agent

Pre-Built: Sidebar

Docked sidebar chat via <CopilotSidebar />

CopilotKit's Built-in Agent

Pre-Built: Popup

Floating popup chat via <CopilotPopup />

CopilotKit's Built-in Agent

Chat Customization: Slots

Customize CopilotChat via its slot system

CopilotKit's Built-in Agent

Headless UI: Simple

Minimum viable headless chat — useAgent + useCopilotKit dressed in shadcn/ui primitives. No tool rendering, no generative UI, just text in / text out.

CopilotKit's Built-in Agent

Headless UI: Complete

Full headless surface — hand-rolled CopilotChat replacement that wires every render hook (useRenderTool, useDefaultRenderTool, useComponent, useRenderToolCall, useRenderActivityMessage, useSuggestions, useAttachments) on top of shadcn primitives.

CopilotKit's Built-in Agent

Reasoning: Default

Built-in CopilotChatReasoningMessage rendering with no slot override.

CopilotKit's Built-in Agent

Reasoning: Custom

Visible reasoning/thinking chain alongside the final answer

CopilotKit's Built-in Agent

Human in the Loop: Interrupts

Interactive component rendered inline in the chat via the lower-level `useInterrupt` primitive — direct control over the LangGraph interrupt lifecycle

CopilotKit's Built-in Agent

Human in the Loop: Headless Interrupts

Same interrupt(...) backend pattern as gen-ui-interrupt, but the time-picker mounts in a separate app-surface pane (left) instead of inline inside the chat — uses useHeadlessInterrupt (custom-event subscribe + manual runAgent forwardedProps.command.resume).

CopilotKit's Built-in Agent

Declarative UI: Dynamic A2UI

Canonical A2UI BYOC — custom catalog (Card/StatusBadge/Metric/InfoRow/PrimaryButton) wired via a2ui.catalog on the provider

CopilotKit's Built-in Agent

Declarative UI: Fixed A2UI

Render an A2UI tree from a fixed, server-side schema — the agent streams data into a pre-authored component tree

CopilotKit's Built-in Agent

A2UI Error Recovery

Makes the A2UI validate->retry recovery loop visible — an invalid first render heals to a valid one, and an always-invalid render shows a graceful recovery-exhausted fallback. Backend-owned via get_a2ui_tools (injectA2UITool=false); reuses the declarative-gen-ui catalog.

CopilotKit's Built-in Agent

MCP Apps

MCP server-driven UI via activity renderers

CopilotKit's Built-in Agent

Shared State: Frontend Context

Frontend provides read-only context to the agent via useAgentContext

CopilotKit's Built-in Agent

Declarative UI: json-render

Streaming hierarchical JSON UI spec rendered via @json-render/react, with a Zod-validated catalog (MetricCard + PieChart + BarChart)

CopilotKit's Built-in Agent

Beautiful Chat

Canonical polished starter chat — brand fonts, theme tokens, suggestion pills

CopilotKit's Built-in Agent

Attachments

Image and PDF uploads via CopilotChat attachments, processed by a vision-capable agent

CopilotKit's Built-in Agent

Authentication

Bearer-token gate via runtime onRequest hook with unauthenticated / authenticated states

CopilotKit's Built-in Agent

Declarative UI: Hashbrown

Streaming structured output via @hashbrownai/react, rendering a sales dashboard catalog (MetricCard + PieChart + BarChart)

CopilotKit's Built-in Agent

Open Generative UI: Default

Agent composes UI from a registered component library — distinct from Tool Rendering, which attaches a custom renderer to a *named* backend tool. Use Open Generative UI when you want the agent to assemble UI freely from a palette you control.

CopilotKit's Built-in Agent

Open Generative UI: Custom

Same Open Generative UI surface, with the iframe-rendered components able to call back into frontend sandbox functions (e.g., a Calculator app whose buttons trigger handlers in the host page).

CopilotKit's Built-in Agent

Voice

Speech-to-text via @copilotkit/voice with a bundled sample audio button

CopilotKit's Built-in Agent

Agent Config Object

Forward a typed config object (tone / expertise / response length) from the provider to the agent's dynamic system prompt