bug: Server-only modules leak into client bundle with Next.js 16.2.0

Describe the bug

When using create-t3-app (v7.40.0, with tRPC + Drizzle + PostgreSQL) as a starter and upgrading Next.js to 16.2.0, next build fails with 6 "Module not found" errors (fs, net, tls, perf_hooks). Next.js 16.1.7 builds successfully — the regression is specific to 16.2.0.

The root cause is that 16.2.0 follows the module graph for type-only imports in "use client" files, pulling server-only code into the client bundle.

The import chain causing the leak:

src/trpc/react.tsx ("use client")
  → import { type AppRouter } from "~/server/api/root"
    → import { createCallerFactory, createTRPCRouter } from "~/server/api/trpc"
      → import { db } from "~/server/db"
        → import postgres from "postgres"   // ← uses fs, net, tls, perf_hooks

How to reproduce

1. pnpm create t3-app@latest (select tRPC + Drizzle + PostgreSQL)
2. In package.json, change "next" to "16.2.0"
3. Run pnpm install && pnpm build
4. Build fails with:
   复制

   Module not found: Can't resolve 'fs'
   Module not found: Can't resolve 'net'
   Module not found: Can't resolve 'tls'
   Module not found: Can't resolve 'perf_hooks'

Note: The same project builds successfully with Next.js 16.1.7.

Expected behavior

The build should succeed. Type-only imports (import { type AppRouter }) should not cause the bundler to follow the server module graph from a client component.

Environment

• create-t3-app: v7.40.0
• Next.js: 16.2.0 (breaks) / 16.1.7 (works)
• Node.js: v22
• Package manager: pnpm

Possible solutions

1. Export the AppRouter type from a separate file that doesn't import any server code (e.g., src/server/api/types.ts that re-exports only the type)
2. Add serverExternalPackages: ['postgres'] to next.config.js
3. Add import "server-only" to server files as a guard
4. Some combination of the above