These apps complement the Core Playground with real library/framework runtimes. They stay isolated so the core React demos can keep teaching concepts without pretending a third-party integration is React itself.

Lab	Runtime	Learning map
`router/`	React Router 8 Data Router	Chapter 10 — routing/page state
`tanstack-query/`	TanStack Query 5 + local HTTP mock server	Chapter 09 — Server State
`next-app-router/`	Next.js 16 App Router	Chapter 12 — SSR/RSC/framework

Run

Each directory owns its dependencies:

cd integration-labs/router && npm install && npm run dev
cd integration-labs/tanstack-query && npm install && npm run dev:all
cd integration-labs/next-app-router && npm install && npm run dev

These apps intentionally are not registered in src/demos/index.js. The existing playground demos remain concept simulators; these labs are executable integration references.

Chapter checkpoints provide the handoff points: Chapter 09 links to TanStack Query, Chapter 10 links to the React Router Data Router lab, and Chapter 12 links to the Next.js App Router lab. The checkpoint copy keeps the Core Demo model separate from each library/framework runtime.