Renders a 500-message thread with @tanstack/react-virtual so only the turns near the viewport are mounted. The runtime is a self-contained external store with a fake streaming reply, so the example runs fully offline with no environment variables.

Quick start

pnpm install
pnpm --filter with-virtualized-thread dev

What the example demonstrates

Concern	File
Virtualizer over user turns, padding spacers, `measureElement`	`app/VirtualizedThread.tsx`
Id-keyed per-message rendering through `ThreadPrimitive.Unstable_MessageById`	`app/VirtualizedThread.tsx`
Sticky-bottom auto-follow with a user-scroll disarm guard	`app/VirtualizedThread.tsx`
External store runtime with seeded messages and a streaming tail	`app/MyRuntimeProvider.tsx`
Deterministic synthetic thread content	`app/seed-messages.ts`

See the thread virtualization guide for the full walkthrough.