NextJS Build hungs.. with sourcemap enabled

[softmarshmallow]

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/nextjs

SDK Version

"@sentry/nextjs": "^9.17.0",

Framework Version

"next": "15.3.2", "react": "19.1.0",

Link to Sentry event

No response

Reproduction Example/SDK Setup

I recently added sentry to my nextjs app.

{
      org: process.env.SENTRY_ORG,
      project: process.env.SENTRY_PROJECT,
      silent: !process.env.CI, // Only print logs for uploading source maps in CI
      widenClientFileUpload: false,
      sourcemaps: {
        disable:
          process.env.NODE_ENV === "development" ||
          process.env.VERCEL_ENV === "preview",
      },

      // Route browser requests to Sentry through a Next.js rewrite to circumvent ad-blockers.
      // This can increase your server load as well as your hosting bill.
      // Note: Check that the configured route will not match with your Next.js middleware, otherwise reporting of client-
      // side errors will fail.
      tunnelRoute: "/monitoring",

      // Automatically tree-shake Sentry logger statements to reduce bundle size
      disableLogger: true,

      // Enables automatic instrumentation of Vercel Cron Monitors. (Does not yet work with App Router route handlers.)
      // See the following for more information:
      // https://docs.sentry.io/product/crons/
      // https://vercel.com/docs/cron-jobs
      automaticVercelMonitors: true,
    } satisfies SentryBuildOptions

The build speed is almost unusable, I think it's a bug.
As you can see,

• production -> sourcemap on
• preview -> sourcemap off

I've turned off the widenClientFileUpload for faster build, which does not resolve the issue.

Before sentry, it was about 5min for build on vercel,

After sentry

• preview (sourcemap off) takes up to 7min (resonable)
• production exceeds the max build duration 45min.

The build logs says,.

........
    ~/ff24b331-ad6e-4070-940f-aef956132cf6-274.js.map (debug id ff24b331-ad6e-4070-940f-aef956132cf6)
    ~/fff82f28-0ad6-47e8-8633-da46db4abc42-130.js.map (debug id fff82f28-0ad6-47e8-8633-da46db4abc42)
[@sentry/nextjs - Node.js] Info: Successfully uploaded source maps to Sentry

But after the "[@sentry/nextjs - Node.js] Info: Successfully uploaded source maps to Sentry"

no logs will appear, and hungs for the next 30mins, build fails.

what is happening?

Steps to Reproduce

repo: https://github.com/gridaco/grida (/editor)

pnpm why @sentry/webpack-plugin

pnpm why @sentry/webpack-plugin
Legend: production dependency, optional only, dev only

[email protected] /Users/softmarshmallow/Documents/Apps/grida/grida/editor (PRIVATE)

dependencies:
@sentry/nextjs 9.17.0
└── @sentry/webpack-plugin 3.3.1

[andreiborza]

Hi @softmarshmallow, thanks for writing in.

Could you run npm why @sentry/webpack-plugin and paste the output?

[softmarshmallow]

Hi @softmarshmallow, thanks for writing in.

Could you run npm why @sentry/webpack-plugin and paste the output?

Hi. Updated in original post

[andreiborza]

Thanks!

Hm, I'm not really spotting anything unusual from this. Could you please try to provide a reproduction repo?

[zhyd1997]

Hi 👋

I thought the root cause was that there are some large files in the server bundle files that the Sentry SDK cannot handle.

https://www.zhyd1997.dev/blog/cal-dot-com-sentry-vercel-oom

[andreiborza]

Thanks for helping out @zhyd1997, that's great writeup. This could very well be related to running out of memory, it's a known issue.

Here are some remedies that you could try before going the route of completely removing withSentry. The withSentry wrapper does more than just ensuring source maps upload so I recommend keeping it.

[zhyd1997]

Hi @andreiborza

Yes, I have tried them all when resolving the issue for Cal.com.

Update your @sentry/nextjs package to the latest version.
Yes, I did it, no effect.
Increase Node.js memory limit: You can try increasing the memory limit for Node.js during the build process. Add this to your build command: NODE_OPTIONS="--max-old-space-size=8192" next build. This flag will increase the memory available to the node process to 8 GB. We have found that Next.js consumes around 4 GB in most cases. Decrease the size depending on your memory availability.

The Vercel container only has 8 GB RAM, I added --max-old-space-size=6144(75% of the container RAM). no effect when using withSentry, but make sense for sentry-cli.

Disable source maps entirely: As a last resort, you can disable source map generation completely

The Cal team needs the sourcemap to debug errors. BTW, it works without sourcemaps.

---

The withSentry wrapper does more than just ensuring source maps upload so I recommend keeping it.

Yes, I see, it will change the webpack config in next.config.js|ts, add webpack plugin, module rules, inject debug IDs, and so on, and finally use new SentryCli() to do Sentry release (uploading sourcemaps both for nodejs, edge, and client runtime).