nextjs: Turbopack applicationKey rule also tags server modules, slowing cold starts #25544

Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/browser

SDK Version

10.64.0 (the same rule ships in 11.8.0 and on develop)

Framework Version

16.4.0

Link to Sentry event

No response

Reproduction Example/SDK Setup

// next.config.ts
export default withSentryConfig(nextConfig, {
  applicationKey: "my-app",
})

// instrumentation-client.ts
Sentry.init({
  dsn: "...",
  integrations: [
    Sentry.thirdPartyErrorFilterIntegration({
      filterKeys: ["my-app"],
      behaviour: "apply-tag-if-exclusively-contains-third-party-frames",
    }),
  ],
})

Steps to Reproduce

1. Set applicationKey in withSentryConfig on a Next 16 app that builds with Turbopack.
2. Run next build.
3. Search the output for _sentryBundlerPluginAppKey:my-app in .next/static and in .next/server.
4. Start next start and time the first request to a route on a fresh process.

Expected Result

Only browser modules carry the metadata snippet. thirdPartyErrorFilterIntegration only runs in the browser, and @sentry/node does not export it, so nothing on the server reads the tags.

Actual Result

constructTurbopackConfig adds a *.{ts,tsx,js,jsx,mjs,cjs} rule whose only condition is { not: { path: /next\/dist\/build\/polyfills/ } }. Turbopack applies it to server and edge modules too. Each snippet evaluates new Error().stack twice when its module loads, so every cold start pays for it.

In our app:

On Vercel's slower CPU the snippets cost 0.4 to 0.5 s per cold start.

Additional Context

Suggested fix, in constructTurbopackConfig:

condition: { all: ["browser", { not: { path: /next\/dist\/build\/polyfills/ } }] },

We ran exactly this as our own turbopack.rules entry pointing at build/cjs/config/loaders/moduleMetadataInjectionLoader.js. The browser output was unchanged.

Related: #19320 (Turbopack applicationKey support), #23402 (same loader, for moduleMetadata), #14041.

Priority

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