CopilotKit React Patterns

Best practices for building agentic React applications with CopilotKit. Contains 25 rules across 6 categories, prioritized by impact to guide code generation and refactoring. Covers both v1 (@copilotkit/react-core) and v2 (@copilotkit/react-core/v2) APIs.

When to Apply

Reference these guidelines when:

• Setting up CopilotKit provider in a React application
• Using agent hooks (useAgent, useFrontendTool, useCopilotAction)
• Rendering tool calls or custom messages from agents
• Managing shared state between UI and agents via useCopilotReadable or useCoAgent
• Building chat interfaces with CopilotChat, CopilotSidebar, or CopilotPopup
• Configuring suggestions for proactive agent assistance

Rule Categories by Priority

Quick Reference

1. Provider Setup (CRITICAL)

• provider-runtime-url - Always configure runtimeUrl to connect to your agent backend
• provider-single-endpoint - Configure the agent prop for CoAgent routing
• provider-nested-providers - Scope agent configurations with nested CopilotKit providers
• provider-tool-registration - Register tools via hooks inside provider, not as props when possible

2. Agent Hooks (HIGH)

• agent-use-agent-updates - Specify update subscriptions to avoid unnecessary re-renders
• agent-agent-id - Always pass agentId when running multiple agents
• agent-context-description - Write descriptive context values for useCopilotReadable
• agent-frontend-tool-deps - Declare dependency arrays for useFrontendTool
• agent-stable-tool-handlers - Use useCallback for tool handler functions

3. Tool Rendering (HIGH)

• tool-typed-args - Define Zod schemas for useRenderTool parameters (v2)
• tool-status-handling - Handle all three tool call statuses (inProgress, executing, complete)
• tool-wildcard-fallback - Register a wildcard renderer as fallback for unknown tools
• tool-render-vs-frontend - Use useRenderTool for display-only, useFrontendTool for side effects
• tool-component-hook - Use useFrontendTool render prop for simple component rendering

4. Context & State (MEDIUM)

• state-minimal-context - Provide only relevant context to agents, not entire app state
• state-structured-values - Use structured objects in useCopilotReadable, not serialized strings
• state-context-granularity - Split context into multiple useCopilotReadable calls by domain
• state-avoid-stale-closures - Use functional state updates in tool handlers

5. Chat UI (MEDIUM)

• ui-chat-layout - Choose CopilotSidebar for persistent chat, CopilotPopup for on-demand
• ui-custom-labels - Always customize labels for your domain instead of defaults
• ui-welcome-screen - Provide a welcome screen with suggested prompts
• ui-input-mode - Use appropriate inputMode for your use case

6. Suggestions (LOW)

• suggestions-configure - Use useConfigureSuggestions (v2) or useCopilotChatSuggestions (v1)
• suggestions-context-driven - Provide rich context so suggestions are relevant
• suggestions-loading-state - Handle suggestion loading states via useSuggestions (v2)

How to Use

Read individual rule files for detailed explanations and code examples:

rules/provider-runtime-url.md
rules/agent-use-agent-updates.md
rules/tool-typed-args.md

Each rule file contains:

• Brief explanation of why it matters
• Incorrect code example with explanation
• Correct code example with explanation
• Additional context and references

Full Compiled Document

For the complete guide with all rules expanded: AGENTS.md