fix: Update nextjs-app-router example for Next.js ^16 and TypeScript compatibility

[amychisholm03]

Description

Bug fix

Resolves the TypeScript type error when using the Turbopack configuration example in a next.config.ts file.

The original example showed:

turbopack: (config) => {
  nrExternals(config)
  return config
}

This mirrors webpack's callable interface, but TurbopackOptions is a plain object — not a function — so TypeScript rejects it with:

Type '(config: any) => any' has no properties in common with type 'TurbopackOptions'. Did you mean to call it? ts(2560)

Changes:

• Renames next.config.js → next.config.ts with proper types (import type { NextConfig }, typed const, export default)
• Documents that nrExternals is webpack-specific and does not apply to Turbopack — newrelic is already automatically excluded from bundling in Next.js 15+
• Shows the correct turbopack: { } object syntax with a comment
• Removes the deprecated experimental.serverComponentsExternalPackages block (superseded by serverExternalPackages in Next.js 15+)
• Updates tsconfig.json to moduleResolution: bundler (the correct setting for Next.js projects, replaces deprecated node)

Hybrid agent (OpenTelemetry bridge)

This example now uses the New Relic hybrid agent instead of native Next.js instrumentation. Requires Next.js >= 16 and newrelic >= 14.1.0.

The hybrid agent routes OpenTelemetry SDK signals through the New Relic pipeline, which is the supported path for Next.js 16+. Native agent support for Next.js 14 and 15 is no longer maintained in this example (though not yet deprecated) — users on those versions should refer to the nextjs-legacy example.

Changes:

• newrelic.js: enables opentelemetry.enabled: true; disables the built-in http, undici, and next instrumentations to prevent duplicate spans when OTel instrumentations are active
• package.json: pins next to ^16.0.0, upgrades newrelic to ^14.1.0 (minimum for Next.js OTel support)- README.md: adds a version requirement callout and links to nextjs-legacy for users on Next.js < 16

Additional fixes

While validating the example against Next.js 16 / Node.js 24 (latest of each at time of writing):

• Build hang: guards all require('newrelic') calls behind process.env.NEXT_PHASE !== 'phase-production-build' — the agent was initializing at build time and waiting indefinitely for a connected event, hanging every static generation worker
• Async params: fixes params.id being undefined in pages and route handlers — in Next.js 15+, params is a Promise and must be awaited (server components) or unwrapped with React.use() (client components)
• Edit page: after saving a user, redirects to the view page and calls router.refresh() to bust the router cache so the updated name is shown
• ESM loader flag: replaces deprecated --loader with --import in the start script; removes --import from dev where Turbopack's own ESM hooks conflict with it on Node.js 24
• Missing dependency: adds react-dom as an explicit dependency
• Linting: migrates from next lint (removed in Next.js 16) to eslint . with a flat eslint.config.mjs and ESLint 9

Related Issues

Closes #345

[bizob2828]

can you update this to use the hybrid agent? you'll have to disable http, next instrumentation in the agent as well?

[bizob2828]

one small issue in the README, otherwise this works