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CopilotKit v2 Development Skill

skills/copilotkit-develop/SKILL.md

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CopilotKit v2 Development Skill

Live Documentation (MCP)

This plugin includes an MCP server (copilotkit-docs) that provides search-docs and search-code tools for querying live CopilotKit documentation and source code.

  • Claude Code: Auto-configured by the plugin's .mcp.json -- no setup needed.
  • Codex: Requires manual configuration. See the copilotkit-debug skill for setup instructions.

Architecture Overview

CopilotKit v2 is built on the AG-UI protocol (@ag-ui/client / @ag-ui/core). The stack has three layers:

  1. Runtime (@copilotkit/runtime) -- Server-side. Hosts agents, handles SSE/Intelligence transport, middleware, transcription.
  2. Core (@copilotkit/core) -- Shared state management, tool registry, suggestion engine. Not imported directly by apps.
  3. React (@copilotkit/react) -- Provider, chat components, hooks. Re-exports everything from @ag-ui/client so apps need only one import.

Workflow

1. Set Up the Runtime (Server)

Create a CopilotRuntime (or the explicit CopilotSseRuntime / CopilotIntelligenceRuntime) and expose it via createCopilotEndpoint (Hono) or createCopilotEndpointExpress (Express).

ts
import { CopilotRuntime, createCopilotEndpoint } from "@copilotkit/runtime";
import { LangGraphAgent } from "@ag-ui/langgraph";

const runtime = new CopilotRuntime({
  agents: {
    myAgent: new LangGraphAgent({
      /* ... */
    }),
  },
});

const app = createCopilotEndpoint({
  runtime,
  basePath: "/api/copilotkit",
});

2. Wrap Your App with the Provider (Client)

tsx
import { CopilotKitProvider } from "@copilotkit/react";

function App() {
  return (
    <CopilotKitProvider runtimeUrl="/api/copilotkit">
      <YourApp />
    </CopilotKitProvider>
  );
}

3. Add a Chat UI

Use <CopilotChat>, <CopilotPopup>, or <CopilotSidebar>:

tsx
import { CopilotChat } from "@copilotkit/react";

function ChatPage() {
  return <CopilotChat agentId="myAgent" />;
}

4. Register Frontend Tools

Let the agent call functions in the browser:

tsx
import { useFrontendTool } from "@copilotkit/react";
import { z } from "zod";

useFrontendTool({
  name: "highlightCell",
  description: "Highlight a spreadsheet cell",
  parameters: z.object({ row: z.number(), col: z.number() }),
  handler: async ({ row, col }) => {
    highlightCell(row, col);
    return "done";
  },
});

5. Share Application Context

Provide runtime data to the agent:

tsx
import { useAgentContext } from "@copilotkit/react";

useAgentContext({
  description: "The user's current shopping cart",
  value: cart, // any JSON-serializable value
});

6. Handle Agent Interrupts

When an agent pauses for human input:

tsx
import { useInterrupt } from "@copilotkit/react";

useInterrupt({
  render: ({ event, resolve }) => (
    <div>
      <p>{event.value.question}</p>
      <button onClick={() => resolve({ approved: true })}>Approve</button>
    </div>
  ),
});

7. Render Tool Calls in Chat

Show custom UI when tools execute:

tsx
import { useRenderTool } from "@copilotkit/react";
import { z } from "zod";

useRenderTool(
  {
    name: "searchDocs",
    parameters: z.object({ query: z.string() }),
    render: ({ status, parameters, result }) => {
      if (status === "executing")
        return <Spinner>Searching {parameters.query}...</Spinner>;
      if (status === "complete") return <Results data={result} />;
      return <div>Preparing...</div>;
    },
  },
  [],
);

Quick Reference: Hooks

HookPurpose
useFrontendToolRegister a tool the agent can call in the browser
useComponentRegister a React component as a chat-rendered tool (convenience wrapper around useFrontendTool)
useAgentContextShare JSON-serializable application state with the agent
useAgentGet the AbstractAgent instance for an agent ID; subscribe to message/state/run-status changes
useInterruptHandle on_interrupt events from agents with render + optional handler/filter
useHumanInTheLoopRegister a tool that pauses execution until the user responds via a rendered UI
useRenderToolRegister a renderer for tool calls (by name or wildcard "*")
useDefaultRenderToolRegister a wildcard "*" renderer using the built-in expandable card UI
useRenderToolCallInternal hook returning a function to resolve the correct renderer for a given tool call
useRenderActivityMessageInternal hook for rendering activity messages by type
useRenderCustomMessagesInternal hook for rendering custom message decorators
useSuggestionsRead the current suggestion list and control reload/clear
useConfigureSuggestionsRegister static or dynamic (LLM-generated) suggestion configs
useThreadsList, rename, archive, and delete Intelligence platform threads

Quick Reference: Components

ComponentPurpose
CopilotKitProviderRoot provider -- configures runtime URL, headers, agents, error handler
CopilotChatFull chat interface connected to an agent (inline layout)
CopilotPopupChat in a floating popup with toggle button
CopilotSidebarChat in a collapsible sidebar with toggle button
CopilotChatViewHeadless chat view with slots for message view, input, scroll, suggestions
CopilotChatInputChat input textarea with send/stop/transcribe controls
CopilotChatMessageViewRenders the message list
CopilotChatSuggestionViewRenders suggestion pills

Quick Reference: Runtime

ExportPurpose
CopilotRuntimeAuto-detecting runtime (delegates to SSE or Intelligence)
CopilotSseRuntimeExplicit SSE-mode runtime
CopilotIntelligenceRuntimeIntelligence-mode runtime with durable threads
createCopilotEndpointCreate a Hono app with all CopilotKit routes
createCopilotEndpointExpressCreate an Express router with all CopilotKit routes
CopilotKitIntelligenceIntelligence platform client configuration