CSS Customization
Theme CopilotKit components via CSS variables and class overrides.
"""LangGraph agent for the CopilotKit Showcase (FastAPI variant).Uses copilotkit's create_agent (wrapping langgraph) with CopilotKitMiddlewareso frontend-registered tools (useHumanInTheLoop, useFrontendTool) are properlyinjected into the LLM's tool list and executed on the frontend rather thanlocally."""from tools import ( get_weather_impl, query_data_impl, schedule_meeting_impl, manage_sales_todos_impl, get_sales_todos_impl, search_flights_impl, build_a2ui_operations_from_tool_call,)from tools.types import SalesTodo, Flightimport jsonimport timefrom typing import Anyfrom langchain_openai import ChatOpenAIfrom langchain_core.tools import tool as lc_toolfrom langchain_core.messages import SystemMessagefrom langchain.agents import AgentState as BaseAgentState, create_agentfrom langchain.tools import ToolRuntime, toolfrom langchain.messages import ToolMessagefrom langgraph.types import Commandfrom copilotkit import CopilotKitMiddlewareclass AgentState(BaseAgentState): todos: list[SalesTodo]@lc_tooldef get_weather(location: str): """Get the current weather for a location.""" return get_weather_impl(location)@lc_tooldef query_data(query: str): """Query the database. Takes natural language. Always call before showing a chart.""" return query_data_impl(query)@lc_tooldef schedule_meeting(reason: str, duration_minutes: int = 30): """Schedule a meeting. The user will be asked to pick a time via the UI.""" return schedule_meeting_impl(reason, duration_minutes)@lc_tooldef search_flights(flights: list[Flight]) -> str: """Search for flights and display the results as rich cards. Return exactly 2 flights. Each flight must have: airline, airlineLogo, flightNumber, origin, destination, date (short readable format like "Tue, Mar 18" -- use near-future dates), departureTime, arrivalTime, duration (e.g. "4h 25m"), status (e.g. "On Time" or "Delayed"), statusColor (hex color for status dot), price (e.g. "$289"), and currency (e.g. "USD"). For airlineLogo use Google favicon API: https://www.google.com/s2/favicons?domain={airline_domain}&sz=128 """ result = search_flights_impl(flights) return json.dumps(result)@tooldef manage_sales_todos(todos: list[SalesTodo], runtime: ToolRuntime) -> Command: """ Manage the current sales todos. Pass the full updated list. """ updated = manage_sales_todos_impl(todos) return Command( update={ "todos": updated, "messages": [ ToolMessage( content="Successfully updated sales todos", tool_call_id=runtime.tool_call_id, ) ], } )@tooldef get_sales_todos(runtime: ToolRuntime): """ Get the current sales todos. """ current = runtime.state.get("todos", []) return get_sales_todos_impl(current if current else None)@lc_tooldef render_a2ui( surfaceId: str, catalogId: str, components: list[dict], data: dict | None = None,) -> str: """Render a dynamic A2UI v0.9 surface.""" return "rendered"@tool()def generate_a2ui(runtime: ToolRuntime[Any]) -> str: """Generate dynamic A2UI components based on the conversation. A secondary LLM designs the UI schema and data. """ t0 = time.time() messages = runtime.state["messages"][:-1] context_entries = runtime.state.get("copilotkit", {}).get("context", []) context_text = "\n\n".join( entry.get("value", "") for entry in context_entries if isinstance(entry, dict) and entry.get("value") ) model = ChatOpenAI(model="gpt-4.1") model_with_tool = model.bind_tools([render_a2ui], tool_choice="render_a2ui") response = model_with_tool.invoke( [SystemMessage(content=context_text), *messages], ) if not response.tool_calls: return json.dumps({"error": "LLM did not call render_a2ui"}) args = response.tool_calls[0]["args"] result = build_a2ui_operations_from_tool_call(args) return json.dumps(result)model = ChatOpenAI(model="gpt-4o-mini")SYSTEM_PROMPT = """You are a polished, professional demo assistant for CopilotKit.Keep responses brief and clear -- 1 to 2 sentences max.You can:- Chat naturally with the user- Change the UI background when asked (via frontend tool)- Query data and render charts (via query_data tool)- Get weather information (via get_weather tool)- Schedule meetings with the user (via schedule_meeting tool -- the user picks a time in the UI)- Manage sales pipeline todos (via manage_sales_todos / get_sales_todos tools)- Search flights and display rich A2UI cards (via search_flights tool)- Generate dynamic A2UI dashboards from conversation context (via generate_a2ui tool)- Generate step-by-step plans for user review (human-in-the-loop)"""graph = create_agent( model=model, tools=[ get_weather, query_data, schedule_meeting, search_flights, generate_a2ui, manage_sales_todos, get_sales_todos, ], middleware=[CopilotKitMiddleware()], state_schema=AgentState, system_prompt=SYSTEM_PROMPT,)What is this?#
CopilotKit has a variety of ways to customize the colors and structure of the Copilot UI components via plain CSS. You can:
- Override CopilotKit CSS variables to re-tint the whole UI
- Target the built-in class names (
.copilotKit...) for structural tweaks - Swap fonts per surface (messages, input, bubbles)
- Replace icons and labels via component props
If you need to change behavior, not just look, see slots or fully headless UI.
Scoping the theme#
The demo keeps all of its styling in a sibling theme.css file and applies it
only to the wrapper div holding <CopilotChat>. Importing the stylesheet from
the page module is enough; Next.js bundles it with the route:
import "./theme.css";Scoping every selector under a wrapper class keeps the overrides from leaking into the rest of the app.
CSS Variables (Easiest)#
The easiest way to change the colors used in the Copilot UI components is to override CopilotKit CSS variables. The demo sets them on the scope wrapper so they cascade into every nested chat component:
/* CopilotKit CSS variable overrides (accent colors, etc.) */.chat-css-demo-scope { --copilot-kit-primary-color: #ff006e; --copilot-kit-contrast-color: #ffffff; --copilot-kit-background-color: #fff8f0; --copilot-kit-input-background-color: #fef3c7; --copilot-kit-secondary-color: #fde047; --copilot-kit-secondary-contrast-color: #2c1810; --copilot-kit-separator-color: #ff006e; --copilot-kit-muted-color: #c2185b;}Once you've found the right variable, you can also apply the overrides inline
via the CopilotKitCSSProperties helper:
import { CopilotKitCSSProperties } from "@copilotkit/react-core/v2";
<div
style={
{
"--copilot-kit-primary-color": "#222222",
} as CopilotKitCSSProperties
}
>
<CopilotSidebar />
</div>Reference#
| CSS Variable | Description |
|---|---|
--copilot-kit-primary-color | Main brand/action color — used for buttons, interactive elements |
--copilot-kit-contrast-color | Color that contrasts with primary — used for text on primary elements |
--copilot-kit-background-color | Main page/container background color |
--copilot-kit-secondary-color | Secondary background — used for cards, panels, elevated surfaces |
--copilot-kit-secondary-contrast-color | Primary text color for main content |
--copilot-kit-separator-color | Border color for dividers and containers |
--copilot-kit-muted-color | Muted color for disabled/inactive states |
Custom CSS#
The CopilotKit CSS is structured to allow customization via CSS classes. You can target specific pieces of the UI from your own stylesheet:
.copilotKitButton {
border-radius: 0;
}
.copilotKitMessages {
padding: 2rem;
}
.copilotKitUserMessage {
background: #007AFF;
}The demo's theme.css wraps every selector under .chat-css-demo-scope so
the overrides don't leak out. Here's the user/assistant bubble block from
that file:
.chat-css-demo-scope .copilotKitMessage.copilotKitUserMessage { background: linear-gradient(135deg, #ff006e 0%, #c2185b 100%); color: #ffffff; font-family: "Georgia", "Cambria", "Times New Roman", serif; font-size: 1.25rem; font-weight: 700; padding: 14px 20px; border-radius: 22px 22px 4px 22px; box-shadow: 0 6px 16px rgba(255, 0, 110, 0.35); border: 2px solid #ff6fa5; letter-spacing: 0.01em;}/* Assistant message bubble – amber, monospace, boxy, dark text */.chat-css-demo-scope .copilotKitMessage.copilotKitAssistantMessage { background: #fde047; color: #1e1b4b; font-family: "JetBrains Mono", "Fira Code", "SF Mono", Menlo, Consolas, monospace; font-size: 1rem; padding: 16px 20px; border-radius: 4px 22px 22px 22px; border: 2px solid #1e1b4b; box-shadow: 4px 4px 0 #1e1b4b; max-width: 80%; margin-right: auto; margin-bottom: 1rem;}Reference#
| CSS Class | Description |
|---|---|
.copilotKitMessages | Main container for all chat messages |
.copilotKitInput | Text input container with typing area and send button |
.copilotKitUserMessage | Styling for user messages |
.copilotKitAssistantMessage | Styling for AI responses |
.copilotKitHeader | Top bar of chat window containing title and controls |
.copilotKitButton | Primary chat toggle button |
.copilotKitWindow | Root container defining overall chat window dimensions |
.copilotKitMarkdown | Styles for rendered markdown content |
.copilotKitCodeBlock | Code snippet container with syntax highlighting |
.copilotKitSidebar | Styles for sidebar chat mode |
.copilotKitPopup | Styles for popup chat mode |
Custom Fonts#
You can customize the fonts by updating the fontFamily property on the
relevant CopilotKit classes:
.copilotKitMessages {
font-family: "Arial, sans-serif";
}
.copilotKitInput {
font-family: "Arial, sans-serif";
}Custom Icons#
Customize icons by passing the icons prop to CopilotSidebar, CopilotPopup,
or CopilotChat:
<CopilotChat
icons={{
openIcon: <YourOpenIconComponent />,
closeIcon: <YourCloseIconComponent />,
}}
/>Custom Labels#
Customize all user-facing copy via the labels prop:
<CopilotChat
labels={{
welcomeMessageText: "Hello! How can I help you today?",
modalHeaderTitle: "My Copilot",
chatInputPlaceholder: "Ask me anything!",
}}
/>