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CopilotKit's Built-in Agent in factory mode. The agent runs in-process inside the Next.js route handler — no separate agent server.
Copy-paste command to clone the canonical starter
npx copilotkit@latest init --framework built-in-agent
Polished starter chat with two-pane layout and pre-wired suggestions
Natural conversation with frontend tool execution
Docked sidebar chat via <CopilotSidebar />
Floating popup chat via <CopilotPopup />
Customize CopilotChat via its slot system
Default CopilotChat re-themed via CopilotKitCSSProperties
Minimal custom chat surface built on useAgent
Full chat implementation built from scratch on useAgent
User approves agent actions before execution
Backend agent tools rendered as UI components
Agent uses tools to trigger UI generation
Long-running agent tasks with generated UI
Bidirectional agent state — UI writes preferences, agent writes notes back
Per-token state delta streaming from agent to UI
Multiple agents with visible task delegation
Time-picker card rendered inline via useHumanInTheLoop for a booking flow
MCP server-driven UI via activity renderers
Agent generates UI from an arbitrary component library
Sandboxed iframe UI calls back into host-defined functions
Built-in DefaultToolCallRenderer wired with no config
Single branded wildcard renderer for every tool call
Tool defined in React, executed in the browser, invoked by the agent
Async frontend-tool handler with branded per-tool render
Async frontend-tool handler resolved by an app-level approval modal
Frontend publishes structured read-only context to the agent via useAgentContext
Bearer-token gate on the runtime via the V2 onRequest hook
Typed config (tone / expertise / responseLength) forwarded via provider properties
Speech-to-text via @copilotkit/voice with sample-audio button
Image and PDF uploads answered by the vision-capable gpt-4o agent
Streaming structured output via @hashbrownai/react
Streaming structured output via @json-render/react
Visible chain-of-thought during normal conversation, rendered via a custom reasoningMessage slot
Zero-config rendering of the agent's reasoning chain via CopilotKit's built-in reasoning message
Sequential tool calls interleaved with the agent's visible reasoning chain
Agent designs an A2UI component tree at runtime from a registered catalog
Frontend owns the component tree; the agent only streams data
In-chat time-picker via useFrontendTool with an async handler that blocks until the user picks a slot — Strategy B adaptation of the LangGraph interrupt primitive
Time-picker popup rendered outside the chat in the app surface — headless variant of the Strategy B interrupt adaptation
