CopilotKit

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:

page.tsx
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:

theme.css
/* 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 VariableDescription
--copilot-kit-primary-colorMain brand/action color — used for buttons, interactive elements
--copilot-kit-contrast-colorColor that contrasts with primary — used for text on primary elements
--copilot-kit-background-colorMain page/container background color
--copilot-kit-secondary-colorSecondary background — used for cards, panels, elevated surfaces
--copilot-kit-secondary-contrast-colorPrimary text color for main content
--copilot-kit-separator-colorBorder color for dividers and containers
--copilot-kit-muted-colorMuted 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:

globals.css
.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:

theme.css
.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 ClassDescription
.copilotKitMessagesMain container for all chat messages
.copilotKitInputText input container with typing area and send button
.copilotKitUserMessageStyling for user messages
.copilotKitAssistantMessageStyling for AI responses
.copilotKitHeaderTop bar of chat window containing title and controls
.copilotKitButtonPrimary chat toggle button
.copilotKitWindowRoot container defining overall chat window dimensions
.copilotKitMarkdownStyles for rendered markdown content
.copilotKitCodeBlockCode snippet container with syntax highlighting
.copilotKitSidebarStyles for sidebar chat mode
.copilotKitPopupStyles for popup chat mode

Custom Fonts#

You can customize the fonts by updating the fontFamily property on the relevant CopilotKit classes:

globals.css
.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!",
  }}
/>