Webpack serialization performance warnings when using @sentry/nextjs

[scobbe]

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/nestjs

SDK Version

8.50.0

Framework Version

React 19.0.0, Next 15.1.4, Node 22.9.0

Link to Sentry event

No response

Reproduction Example/SDK Setup

Description

When adding Sentry configuration to next.config.ts using withSentryConfig, I encounter the following warning during the build process:

<w> [webpack.cache.PackFileCacheStrategy] Serializing big strings (318kiB) impacts deserialization performance (consider using Buffer instead and decode when needed)

Is this a known issue? Are there any recommendations for addressing this warning, such as additional configuration options or workarounds?

Thank you!

Steps to Reproduce

1. Start with a minimal next.config.ts file:

   import type { NextConfig } from "next";
   
   const nextConfig: NextConfig = {};
   
   export default nextConfig;

2. Update the file to include Sentry's configuration using withSentryConfig:

   import type { NextConfig } from "next";
   
   import { withSentryConfig } from "@sentry/nextjs";
   
   const nextConfig: NextConfig = {};
   
   export default withSentryConfig(nextConfig, {
     automaticVercelMonitors: true,
     disableLogger: true,
     hideSourceMaps: true,
     org: "MyOrg",
     project: "javascript-nextjs",
     reactComponentAnnotation: {
       enabled: true,
     },
     silent: !process.env.CI,
     sourcemaps: {
       deleteSourcemapsAfterUpload: true,
       disable: process.env.NODE_ENV === "development",
     },
     tunnelRoute: "/monitoring",
     widenClientFileUpload: true,
   });

3. Run the build process.

Expected Result

The build completes without warnings or errors.

Actual Result

The following warning appears during the build process:

<w> [webpack.cache.PackFileCacheStrategy] Serializing big strings (318kiB) impacts deserialization performance (consider using Buffer instead and decode when needed)

[andreiborza]

Hello @scobbe, thank you for filing this.

Could you please provide a reproduction repo? I tried setting up a new nextjs project using npx create-next-app@latest and setting Sentry up using npx @sentry/wizard@latest -i nextjs but did not run into any such warnings.