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
/* HALCYON palette — a private library at golden hour. The whole theme is * one warm parchment hue, one warm ink, and a deep copper ember used * sparingly so it actually reads as a signal. */.chat-css-demo-scope {  --halcyon-paper: #f4efe6;  --halcyon-paper-soft: #ece6d9;  --halcyon-paper-elevated: #fbf8f2;  --halcyon-card: #ffffff;  --halcyon-rule: #d6cfbe;  --halcyon-rule-strong: #aea48a;  --halcyon-ink: #1a1714;  --halcyon-ink-soft: #3d362e;  --halcyon-ink-mute: #7a7468;  --halcyon-ember: #c44a1f;  --halcyon-ember-bright: #e45f2b;  --halcyon-ember-soft: #f3d7c5;  --halcyon-champagne: #98794a;  --halcyon-display:    "Instrument Serif", ui-serif, "Iowan Old Style", Georgia, serif;  --halcyon-serif:    "Fraunces", "Source Serif Pro", ui-serif, Georgia, "Times New Roman", serif;  --halcyon-sans:    "Inter Tight", ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI",    sans-serif;  --halcyon-mono:    "JetBrains Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;  --halcyon-shadow-soft:    0 1px 0 rgba(26, 23, 20, 0.04), 0 12px 32px -18px rgba(26, 23, 20, 0.18);  --halcyon-shadow-ember:    0 1px 0 rgba(196, 74, 31, 0.18), 0 14px 36px -16px rgba(196, 74, 31, 0.42);}

Once you've found the right variable, you can also apply the overrides inline via the CopilotKitCSSProperties helper:

import { CopilotKitCSSProperties } from "@copilotkit/react-ui";

<div
  style={
    {
      "--copilot-kit-primary-color": "#222222",
    } as CopilotKitCSSProperties
  }
>
  <CopilotSidebar />
</div>

Reference#

CSS VariableDescription
--copilot-kit-primary-colorMain brand/action color for buttons and 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 for cards, panels, and 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
--copilot-kit-shadow-sm / -md / -lgElevation shadows for subtle surfaces, cards, and modals

Two token systems

The --copilot-kit-* variables above style the v1 component CSS (@copilotkit/react-ui). The newer v2 components (@copilotkit/react-core/v2) are Tailwind + shadcn-based and use a separate set of design tokens. See v2 design tokens below.

v2 Design Tokens (shadcn)#

The v2 components (@copilotkit/react-core/v2) ship a Tailwind v4 theme built on the standard shadcn/ui token set. Instead of the --copilot-kit-* variables, they read oklch color tokens that are scoped to the [data-copilotkit] root and wired into Tailwind utilities through an @theme inline block. This means you can re-skin the entire v2 UI by overriding a handful of CSS custom properties. Every component picks the change up automatically.

Override them on the [data-copilotkit] element (or any ancestor) the same way you would in a shadcn project:

globals.css
[data-copilotkit] {
  --primary: oklch(0.55 0.22 264); /* accent / action color */
  --primary-foreground: oklch(0.99 0 0); /* text on primary */
  --background: oklch(1 0 0); /* surface background */
  --foreground: oklch(0.145 0 0); /* primary text */
  --muted: oklch(0.97 0 0); /* subtle backgrounds */
  --border: oklch(0.922 0 0); /* dividers, outlines */
  --radius: 0.625rem; /* global corner radius */
}

/* Dark mode is keyed off a `.dark` ancestor */
.dark [data-copilotkit] {
  --background: oklch(0.145 0 0);
  --foreground: oklch(0.985 0 0);
  --border: oklch(0.269 0 0);
}

Reference#

These are the most commonly overridden v2 tokens. Each light value has a matching dark-mode value under .dark [data-copilotkit]. The full set (popover, accent, destructive, chart, and sidebar variants) lives in @copilotkit/react-core/v2/styles.css.

TokenDescription
--background / --foregroundBase surface background and primary text color
--primary / --primary-foregroundAccent/action color and the text rendered on top of it
--secondary / --secondary-foregroundSecondary surfaces (cards, panels) and their text
--muted / --muted-foregroundSubtle backgrounds and de-emphasized text
--accent / --accent-foregroundHover/active states and their text
--border / --input / --ringDivider/outline color, input borders, focus ring
--destructive / --destructive-foregroundError/danger color and its text
--card / --popover (+ -foreground)Elevated surface backgrounds and their text
--sidebar-*The sidebar's own background/foreground/border/ring set
--radiusBase corner radius; --radius-sm/md/lg/xl derive from it

oklch values

v2 tokens use the oklch() color space, which keeps perceived lightness consistent across hues. You can still pass hsl(), rgb(), or hex; any valid CSS color works.

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 message bubble block from that file:

theme.css
/* User message — a "transmission" in JetBrains Mono on a paper card. The * outer wrapper is the right-aligning flex column; we leave it transparent * and style the inner bubble (which uses cpk:bg-muted, hence we also * target the substring class as a stable hook). */.chat-css-demo-scope .copilotKitMessage.copilotKitUserMessage {  background: transparent;  padding: 0;  border: none;  box-shadow: none;}.chat-css-demo-scope  .copilotKitMessage.copilotKitUserMessage  > [class*="bg-muted"] {  font-family: var(--halcyon-mono);  font-size: 0.875rem;  font-weight: 400;  color: var(--halcyon-ink);  background: var(--halcyon-paper-elevated);  border: 1px solid var(--halcyon-rule);  border-left: 2px solid var(--halcyon-ember);  border-radius: 0;  padding: 12px 16px 12px 18px;  letter-spacing: -0.005em;  line-height: 1.55;  box-shadow: 0 1px 0 rgba(26, 23, 20, 0.03);  position: relative;}/* A mono "→" marker before the user's text to read like a CLI prompt. */.chat-css-demo-scope  .copilotKitMessage.copilotKitUserMessage  > [class*="bg-muted"]::before {  content: "→";  display: inline-block;  margin-right: 10px;  color: var(--halcyon-ember);  font-weight: 500;}

Reference#

CSS ClassDescription
.copilotKitMessagesMain container for all chat messages
.copilotKitMessageBase class applied to every message bubble (user and assistant)
.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!",
  }}
/>