Build the UI

Task 1: Run everything locally

Start the full local stack — the game-ui dev server together with a local Game API and a local AG-UI Story Agent (which in turn boots the Inventory MCP server) — with one command:

pnpm

pnpm nx serve-local game-ui

yarn

yarn nx serve-local game-ui

npm

npx nx serve-local game-ui

bun

bunx nx serve-local game-ui

game-ui:serve-local has dependsOn on game-api:serve-local and dungeon_adventure.story:agent-serve-local, so Nx spins up every project’s local server in parallel. Open the dev server in a browser and follow the prompts to create a new user.

Keep Dev Server Running

Leave the dev server running for the rest of this module — it hot-reloads every change below.

Pointing at the deployed backend instead

If you’d prefer your local dev server to talk to the already-deployed APIs + agent, pull the deployed runtime config once and then use the plain serve target:

pnpm

pnpm nx run game-ui:load:runtime-config

yarn

yarn nx run game-ui:load:runtime-config

npm

npx nx run game-ui:load:runtime-config

bun

bunx nx run game-ui:load:runtime-config

pnpm

pnpm nx serve game-ui

yarn

yarn nx serve game-ui

npm

npx nx serve game-ui

bun

bunx nx serve game-ui

This is handy when you’re only iterating on UI code and want to test against the real backend.

Task 2: Where CopilotKit is already wired up

When you ran the connection generator for game-ui → story in Module 1, the Shadcn website’s AG-UI integration was generated for you. It’s worth a quick look:

• Directorypackages/game-ui/src/

  • Directorycomponents/

    • AguiProvider.tsx Single CopilotKitProvider registered with every AG-UI agent.
    • Directorycopilot/

      • index.tsx Re-exports themed CopilotChat / CopilotSidebar / CopilotPopup.
      • ShadcnAssistantMessage.tsx, ShadcnUserMessage.tsx, ShadcnChatInput.tsx, ShadcnCursor.tsx, copilot.css
  • Directoryhooks/

    • useAguiStoryAgent.tsx Instantiates an @ag-ui/client HttpAgent pointing at the deployed Story Agent and pads threadId to AgentCore’s 33-character minimum session id.
  • main.tsx Wraps <App /> in <AguiProvider>

All we need to do is drop a <CopilotChat agentId="agent" threadId={...} /> into a route. For more detail on how the integration is put together, see the React → AG-UI connection guide.

Task 3: Restyle for the dungeon

Replace packages/game-ui/src/styles.css — this is the only file we change for styling. It imports the shared Shadcn globals, overrides the palette to a torch-lit dungeon theme, and makes CopilotKit inherit those colours:

@import '../../common/shadcn/src/styles/globals.css';
@source './**/*.{ts,tsx}';

/* Dungeon theme — torch-lit parchment on stone. Applied to `:root` for the
 * page and to `[data-copilotkit][data-copilotkit]` for CopilotKit's chat
 * surface; CopilotKit ships a same-specificity `[data-copilotkit]` rule that
 * resets `--background` back to white, so we bump specificity with the
 * doubled selector. */
:root,
[data-copilotkit][data-copilotkit] {
  --background: oklch(0.18 0.02 60);
  --foreground: oklch(0.92 0.04 85);
  --card: oklch(0.22 0.03 60);
  --card-foreground: oklch(0.92 0.04 85);
  --popover: oklch(0.2 0.02 60);
  --popover-foreground: oklch(0.92 0.04 85);
  --primary: oklch(0.75 0.15 75);
  --primary-foreground: oklch(0.15 0.02 60);
  --secondary: oklch(0.28 0.04 60);
  --secondary-foreground: oklch(0.92 0.04 85);
  --muted: oklch(0.25 0.02 60);
  --muted-foreground: oklch(0.7 0.04 85);
  --accent: oklch(0.4 0.12 30);
  --accent-foreground: oklch(0.95 0.04 85);
  --destructive: oklch(0.55 0.22 25);
  --border: oklch(0.35 0.03 60);
  --input: oklch(0.3 0.03 60);
  --ring: oklch(0.75 0.15 75);
  --sidebar: oklch(0.15 0.02 60);
  --sidebar-foreground: oklch(0.88 0.04 85);
  --sidebar-primary: oklch(0.75 0.15 75);
  --sidebar-primary-foreground: oklch(0.15 0.02 60);
  --sidebar-accent: oklch(0.28 0.04 60);
  --sidebar-accent-foreground: oklch(0.92 0.04 85);
  --sidebar-border: oklch(0.3 0.03 60);
  --sidebar-ring: oklch(0.75 0.15 75);
}

body {
  font-family: 'Georgia', 'Cambria', serif;
  background:
    radial-gradient(circle at 20% 10%, oklch(0.25 0.05 70 / 0.4), transparent 40%),
    radial-gradient(circle at 80% 90%, oklch(0.25 0.1 30 / 0.3), transparent 40%),
    var(--background);
}

h1, h2, h3 {
  letter-spacing: 0.05em;
}

Task 4: Create the game routes

We need two routes — one to pick a hero, one to play. Both use shadcn components and the CopilotKit chat; there is no hand-rolled chat UI.

routes/index.tsx

+

import { useInfiniteQuery, useMutation } from '@tanstack/react-query';
import { createFileRoute, useNavigate } from '@tanstack/react-router';
import { useEffect, useMemo, useRef, useState } from 'react';
import { Button } from ':dungeon-adventure/common-shadcn/components/ui/button';
import { Input } from ':dungeon-adventure/common-shadcn/components/ui/input';
import {
  Card,
  CardContent,
} from ':dungeon-adventure/common-shadcn/components/ui/card';
import { Spinner } from ':dungeon-adventure/common-shadcn/components/ui/spinner';
import { useGameApi } from '../hooks/useGameApi';
import type { IGame } from ':dungeon-adventure/game-api';

const GENRES = ['medieval', 'zombie', 'superhero'] as const;

export const Route = createFileRoute('/')({ component: RouteComponent });

function RouteComponent() {
  const [playerName, setPlayerName] = useState('');
  const [pending, setPending] = useState<IGame['genre'] | null>(null);
  const navigate = useNavigate();
  const gameApi = useGameApi();
  const saveGame = useMutation(gameApi.games.save.mutationOptions());
  const games = useInfiniteQuery(
    gameApi.games.query.infiniteQueryOptions(
      { limit: 10 },
      { getNextPageParam: ({ cursor }) => cursor ?? undefined },
    ),
  );
  const savedGames = useMemo(
    () => games.data?.pages.flatMap((p) => p.items) ?? [],
    [games.data],
  );

  // Auto-fetch subsequent pages when the sentinel at the bottom of the list
  // scrolls into view — keeps the homepage a simple infinite scroll without
  // a "Load more" button.
  const sentinel = useRef<HTMLDivElement | null>(null);
  useEffect(() => {
    const el = sentinel.current;
    if (!el || !games.hasNextPage) return;
    const io = new IntersectionObserver(
      (entries) => {
        if (
          entries.some((e) => e.isIntersecting) &&
          !games.isFetchingNextPage
        ) {
          void games.fetchNextPage();
        }
      },
      { rootMargin: '120px' },
    );
    io.observe(el);
    return () => io.disconnect();
  }, [games.hasNextPage, games.isFetchingNextPage, games.fetchNextPage]);

  const startGame = async (player: string, genre: IGame['genre']) => {
    if (!player.trim()) return;
    setPending(genre);
    try {
      if (!savedGames.find((g) => g.playerName === player)) {
        await saveGame.mutateAsync({ playerName: player, genre });
      }
      await navigate({
        to: '/game/$playerName',
        params: { playerName: player },
        search: { genre },
      });
    } finally {
      setPending(null);
    }
  };

  const busy = pending !== null;
  const firstLoad = games.isLoading;

  return (
    <div className="mx-auto flex w-full max-w-2xl flex-col gap-8">
      <div className="text-center">
        <h1 className="bg-gradient-to-r from-amber-300 to-rose-400 bg-clip-text text-5xl font-bold text-transparent">
          AI Dungeon Adventure
        </h1>
        <p className="text-muted-foreground mt-2">
          Pick a hero name, choose a genre, begin.
        </p>
      </div>

      <Card>
        <CardContent className="flex flex-col gap-4 pt-6">
          <Input
            placeholder="Your hero's name"
            value={playerName}
            disabled={busy}
            onChange={(e) => setPlayerName(e.target.value)}
          />
          <div className="grid grid-cols-3 gap-3">
            {GENRES.map((genre) => (
              <Button
                key={genre}
                variant="secondary"
                disabled={!playerName.trim() || busy}
                onClick={() => startGame(playerName, genre)}
              >
                {pending === genre && <Spinner />}
                {genre[0].toUpperCase() + genre.slice(1)}
              </Button>
            ))}
          </div>
        </CardContent>
      </Card>

      <div className="flex flex-col gap-2">
        <h2 className="flex items-center gap-2 text-xl font-semibold">
          Continue
          {(firstLoad || games.isFetching) && <Spinner className="size-4" />}
        </h2>
        {!firstLoad && savedGames.length === 0 && (
          <p className="text-muted-foreground text-sm">
            No saved games yet — start a new adventure above.
          </p>
        )}
        {savedGames.map((g) => (
          <Button
            key={g.playerName}
            variant="outline"
            className="justify-between"
            disabled={busy}
            onClick={() => startGame(g.playerName, g.genre)}
          >
            <span>{g.playerName}</span>
            <span className="text-muted-foreground text-sm">
              {g.genre[0].toUpperCase() + g.genre.slice(1)}
            </span>
          </Button>
        ))}
        <div ref={sentinel} aria-hidden className="h-1" />
        {games.isFetchingNextPage && (
          <div className="flex justify-center py-2">
            <Spinner />
          </div>
        )}
      </div>
    </div>
  );
}

+-

import { createFileRoute } from '@tanstack/react-router';
import { useInfiniteQuery, useMutation } from '@tanstack/react-query';
import { createFileRoute, useNavigate } from '@tanstack/react-router';
import { useEffect, useMemo, useRef, useState } from 'react';
import { Button } from ':dungeon-adventure/common-shadcn/components/ui/button';
import { Input } from ':dungeon-adventure/common-shadcn/components/ui/input';
import {
  Card,
  CardContent,
} from ':dungeon-adventure/common-shadcn/components/ui/card';
import { Spinner } from ':dungeon-adventure/common-shadcn/components/ui/spinner';
import { useGameApi } from '../hooks/useGameApi';
import type { IGame } from ':dungeon-adventure/game-api';

export const Route = createFileRoute('/')({
  component: RouteComponent,
});
const GENRES = ['medieval', 'zombie', 'superhero'] as const;

export const Route = createFileRoute('/')({ component: RouteComponent });

function RouteComponent() {
  const [playerName, setPlayerName] = useState('');
  const [pending, setPending] = useState<IGame['genre'] | null>(null);
  const navigate = useNavigate();
  const gameApi = useGameApi();
  const saveGame = useMutation(gameApi.games.save.mutationOptions());
  const games = useInfiniteQuery(
    gameApi.games.query.infiniteQueryOptions(
      { limit: 10 },
      { getNextPageParam: ({ cursor }) => cursor ?? undefined },
    ),
  );
  const savedGames = useMemo(
    () => games.data?.pages.flatMap((p) => p.items) ?? [],
    [games.data],
  );

  // Auto-fetch subsequent pages when the sentinel at the bottom of the list
  // scrolls into view — keeps the homepage a simple infinite scroll without
  // a "Load more" button.
  const sentinel = useRef<HTMLDivElement | null>(null);
  useEffect(() => {
    const el = sentinel.current;
    if (!el || !games.hasNextPage) return;
    const io = new IntersectionObserver(
      (entries) => {
        if (
          entries.some((e) => e.isIntersecting) &&
          !games.isFetchingNextPage
        ) {
          void games.fetchNextPage();
        }
      },
      { rootMargin: '120px' },
    );
    io.observe(el);
    return () => io.disconnect();
  }, [games.hasNextPage, games.isFetchingNextPage, games.fetchNextPage]);

  const startGame = async (player: string, genre: IGame['genre']) => {
    if (!player.trim()) return;
    setPending(genre);
    try {
      if (!savedGames.find((g) => g.playerName === player)) {
        await saveGame.mutateAsync({ playerName: player, genre });
      }
      await navigate({
        to: '/game/$playerName',
        params: { playerName: player },
        search: { genre },
      });
    } finally {
      setPending(null);
    }
  };

  const busy = pending !== null;
  const firstLoad = games.isLoading;

  return (
    <div className="text-center">
      <header>
        <h1>Welcome</h1>
        <p>Welcome to your new React website!</p>
      </header>
    <div className="mx-auto flex w-full max-w-2xl flex-col gap-8">
      <div className="text-center">
        <h1 className="bg-gradient-to-r from-amber-300 to-rose-400 bg-clip-text text-5xl font-bold text-transparent">
          AI Dungeon Adventure
        </h1>
        <p className="text-muted-foreground mt-2">
          Pick a hero name, choose a genre, begin.
        </p>
      </div>

      <Card>
        <CardContent className="flex flex-col gap-4 pt-6">
          <Input
            placeholder="Your hero's name"
            value={playerName}
            disabled={busy}
            onChange={(e) => setPlayerName(e.target.value)}
          />
          <div className="grid grid-cols-3 gap-3">
            {GENRES.map((genre) => (
              <Button
                key={genre}
                variant="secondary"
                disabled={!playerName.trim() || busy}
                onClick={() => startGame(playerName, genre)}
              >
                {pending === genre && <Spinner />}
                {genre[0].toUpperCase() + genre.slice(1)}
              </Button>
            ))}
          </div>
        </CardContent>
      </Card>

      <div className="flex flex-col gap-2">
        <h2 className="flex items-center gap-2 text-xl font-semibold">
          Continue
          {(firstLoad || games.isFetching) && <Spinner className="size-4" />}
        </h2>
        {!firstLoad && savedGames.length === 0 && (
          <p className="text-muted-foreground text-sm">
            No saved games yet — start a new adventure above.
          </p>
        )}
        {savedGames.map((g) => (
          <Button
            key={g.playerName}
            variant="outline"
            className="justify-between"
            disabled={busy}
            onClick={() => startGame(g.playerName, g.genre)}
          >
            <span>{g.playerName}</span>
            <span className="text-muted-foreground text-sm">
              {g.genre[0].toUpperCase() + g.genre.slice(1)}
            </span>
          </Button>
        ))}
        <div ref={sentinel} aria-hidden className="h-1" />
        {games.isFetchingNextPage && (
          <div className="flex justify-center py-2">
            <Spinner />
          </div>
        )}
      </div>
    </div>
  );
}

This is the game picker: new-game form (shadcn Input + Button + Card) plus a “Continue” list fed by useGameApi().games.query with useInfiniteQuery — a bottom sentinel <div> watched by an IntersectionObserver auto-calls fetchNextPage() when scrolled into view, and spinners next to the heading and below the list surface the loading state. Starting a game saveGames the (playerName, genre) pair (so it shows up next time) and navigates to the play route.

routes/game/$playerName.tsx

import { UseAgentUpdate, useAgent } from '@copilotkit/react-core/v2';
import { useQuery } from '@tanstack/react-query';
import { createFileRoute } from '@tanstack/react-router';
import { useEffect, useMemo, useRef } from 'react';
import { CopilotChat } from '../../components/copilot';
import { useGameApi } from '../../hooks/useGameApi';
import type { IGame } from ':dungeon-adventure/game-api';

// AgentCore session ids must be at least 33 characters. The AG-UI hook pads
// the threadId to this length before sending, so the thread id is stable for
// a given (player, genre) pair — revisiting the URL continues the same story.
const buildThreadId = (playerName: string, genre: string) =>
  `${playerName}-${genre}`.padEnd(33, '0');

export const Route = createFileRoute('/game/$playerName')({
  component: RouteComponent,
  validateSearch: (search: Record<string, unknown>) => ({
    genre: search.genre as IGame['genre'],
  }),
});

function RouteComponent() {
  const { playerName } = Route.useParams();
  const { genre } = Route.useSearch();
  const threadId = useMemo(
    () => buildThreadId(playerName, genre),
    [playerName, genre],
  );

  const gameApi = useGameApi();
  const inventory = useQuery(
    gameApi.inventory.query.queryOptions({ playerName, limit: 100 }),
  );
  // Conversation history persisted by the agent's ``S3SessionManager``. Each
  // turn is stored as ``session_<threadId>/agents/agent_default/messages/…``.
  //
  // `staleTime: 0` + `refetchOnMount: 'always'` together force a fresh read
  // on every visit — the cached snapshot from the *first* time we loaded
  // this route (before the agent had written any turns back to S3) would
  // otherwise look like an empty thread on revisit and trigger re-priming.
  const pastActions = useQuery({
    ...gameApi.actions.query.queryOptions({ sessionId: threadId }),
    staleTime: 0,
    refetchOnMount: 'always',
  });

  const { agent } = useAgent({
    agentId: 'agent',
    updates: [UseAgentUpdate.OnMessagesChanged],
  });

  // Hydrate the chat once the history query resolves. For a fresh thread
  // (no stored messages) the agent's system prompt expects the player's
  // name and genre in the first user message, so send that priming line.
  //
  // We wait for `isFetching` to go false (rather than just `isLoading`) so
  // that revisits with a cached empty result from the first visit aren't
  // mistaken for a fresh thread — the background refetch is what sees the
  // turns the agent wrote since.
  const primedRef = useRef(false);
  useEffect(() => {
    if (!agent || primedRef.current) return;
    if (pastActions.isFetching || !pastActions.isSuccess) return;
    primedRef.current = true;
    const items = pastActions.data.items;
    if (items.length > 0) {
      agent.setMessages(
        items.map((a) => ({
          id: `m-${a.messageId}`,
          role: a.role,
          content: a.content,
        })),
      );
      return;
    }
    agent.addMessage({
      id: crypto.randomUUID(),
      role: 'user',
      content: `My name is ${playerName}. Start my ${genre} adventure.`,
    });
    void agent.runAgent();
  }, [
    agent,
    pastActions.data,
    pastActions.isFetching,
    pastActions.isSuccess,
    playerName,
    genre,
  ]);

  // The agent's ``add-to-inventory`` tool calls mutate DynamoDB directly, so
  // the inventory query needs a nudge to refetch as turns complete. The
  // ``useAgent({ updates: [OnMessagesChanged] })`` subscription re-renders
  // this route on each message event — refetch whenever the message count
  // changes, which covers both the initial populate and every subsequent
  // turn.
  const seenMessages = useRef(0);
  useEffect(() => {
    if (!agent) return;
    if (agent.messages.length !== seenMessages.current) {
      seenMessages.current = agent.messages.length;
      void inventory.refetch();
    }
  });

  return (
    <div className="relative flex h-[calc(100vh-10rem)] min-h-0 flex-col">
      {!!inventory.data?.items.length && (
        <aside className="bg-accent text-accent-foreground pointer-events-none absolute right-4 top-4 z-10 w-56 rounded-lg border p-3 shadow-lg">
          <div className="mb-1 font-semibold">📦 Inventory</div>
          <ul className="flex flex-col gap-0.5 text-sm">
            {inventory.data.items.map((item) => (
              <li key={item.itemName}>
                {item.emoji ?? '•'} {item.itemName}
                {item.quantity > 1 ? ` (x${item.quantity})` : ''}
              </li>
            ))}
          </ul>
        </aside>
      )}
      <CopilotChat
        agentId="agent"
        threadId={threadId}
        labels={{
          chatInputPlaceholder: 'What do you do?',
          welcomeMessageText: `${playerName}'s ${genre} adventure`,
        }}
      />
    </div>
  );
}

This is the play route. It builds the deterministic threadId ({player}-{genre} padded to 33 chars — the AG-UI hook will send it verbatim as the AgentCore session id), renders <CopilotChat agentId="agent" threadId={threadId} />, and overlays the inventory from useGameApi().inventory.query on top. On mount, useGameApi().actions.query({ sessionId: threadId }) reads the conversation history the agent has stored in S3 and — if there is any — calls agent.setMessages(...) to rehydrate the chat; otherwise it sends one priming user message to kick the story off. agent.messages is subscribed via useAgent({ updates: [OnMessagesChanged] }) so every new turn also refetches the inventory query (the MCP tool calls mutate DynamoDB directly).

Wait for `isFetching`, not `isLoading`

React Query’s default cache retains the first result for 5 minutes, so a return visit initially sees the stale empty list from the very first load. We set staleTime: 0 + refetchOnMount: 'always' and guard the hydration useEffect on !isFetching && isSuccess so the re-prime path only fires on a genuinely empty thread.

Deterministic threadIds make /game/$playerName?genre=... sharable

Revisiting the same URL — whether after a reload, a redeploy, or on another device — resolves to the same threadId, so the agent keeps telling the same story.

Path Parameters

The $playerName syntax tells @tanstack/react-router to treat playerName as a path param. validateSearch makes genre strongly typed against our enum.

Once saved, the dev server at http://localhost:4200/ should now let you start an adventure and chat with the Story Agent.

You can also build & deploy your code to CloudFront if you prefer.

Congratulations. You have built and deployed your Agentic Dungeon Adventure Game! 🎉🎉🎉