[appkit plugin] [7/x] Add default-ui playground for @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)

---

Summary

Adds a minimal playground app (integrations/appkit-agent/playground/default-ui/) that demonstrates the agent + chat plugin stack with the bundled UI from p6. The playground is a server-only project — it imports @databricks/appkit-agent as a workspace dependency and uses chat.staticAssetsPath to serve the pre-built chat client.

This serves as a development testbed and a reference example for wiring the plugins together.

Playground setup

playground/default-ui/
  server/index.ts    # ~18 lines — the entire app
  package.json
  .env.example
  tsconfig.json

server/index.ts is the complete application:

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

await createApp({
  plugins: [
    server({ autoStart: true, staticPath: chat.staticAssetsPath }),
    agent({
      model: process.env.DATABRICKS_MODEL || "databricks-claude-sonnet-4-5",
      systemPrompt: "You are a helpful assistant.",
      tools: [],
    }),
    chat({
      backend: "agent",
    }),
  ],
});

How to run

cd integrations/appkit-agent/playground/default-ui
cp .env.example .env
# Configure DATABRICKS_CONFIG_PROFILE or DATABRICKS_HOST + DATABRICKS_TOKEN
pnpm install
pnpm run dev   # tsx watch --env-file=.env server/index.ts

Other changes

• .gitignore: added .env and .env.local to prevent committing secrets
• src/chat-plugin/types.ts: duplicate autoMigrate field added during rebase (to be cleaned up)

[bbqiu]

do we need these for the UI?

[bbqiu]

same with the postgres packages

[bbqiu]

i don't 100% understand the plugin ecosystem that well, but when we eventually want to switch the e2e template over to be using this, will we not have to include default startup commands in the app.yaml?

[bbqiu]

lgtm after removing unused dependencies