[appkit plugin] [6/x] Add bundled chat UI to @databricks/appkit-agent

[hubertzub-db]

🥞 Stacked PR

• stack/agent-plugin-p2
• stack/agent-plugin-p3 (diff)
• stack/agent-plugin-p4 (diff)
• stack/agent-plugin-p5 (diff)
• stack/agent-plugin-p6 (diff)
• stack/agent-plugin-p7 (diff)
• stack/agent-plugin-p8 (diff)

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Signed-off-by: Hubert Zub hubert.zub@databricks.com

Summary

Adds a pre-built React chat client to @databricks/appkit-agent, bundled into dist/chat-client/ during pnpm run build. The UI is served as static assets via the chat plugin — not exported as importable React components.

Important

This PR introduces UI pieces copied from e2e-chatbot-app-next that are used only for building a full bundle meant to be served by the appkit. Separate UI building blocks will be exported in latter PRs.

The client source is adapted from databricks/app-templates/e2e-chatbot-app-next/client, moved into integrations/appkit-agent/client/ as a self-contained Vite + React app with its own package.json and pnpm-lock.yaml.

How it works

The chat plugin exposes chat.staticAssetsPath which resolves to the dist/chat-client/ directory containing the built SPA. Pass it to AppKit's server plugin to serve the UI:

import { createApp } from "@databricks/appkit";
import { chat, agent } from "@databricks/appkit-agent";

const app = createApp({
  plugins: [
    server({ staticPath: chat.staticAssetsPath }),
    agent({}),
    chat({ backend: "agent" }),
  ],
});

Full demo (running as appkit app)

Screen.Recording.2026-03-25.at.11.36.45.mov