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?

Self-hosted/on-premise

Which SDK are you using?

@sentry/sveltekit

SDK Version

11.4.0 (also seen on 10.76.0)

Framework Version

@sveltejs/kit 3.0.0, @sveltejs/adapter-node 6.0.0, Vite 8.3.2

Link to Sentry event

No response

Reproduction Example/SDK Setup

// vite.config.ts
import { sentrySvelteKit } from '@sentry/sveltekit/vite';

sentrySvelteKit({
  autoUploadSourceMaps: true,
  adapter: 'node',
  debug: true,
  org: '...',
  project: '...',
  sentryUrl: '...',
  sourcemaps: { assets: ['./build/**/*'] },
}),
sveltekit({ adapter: nodeAdapter, /* ... */ }),

Steps to Reproduce

1. Set up SvelteKit 3 with adapter-node and sentrySvelteKit() as above, with SENTRY_AUTH_TOKEN set.
2. Run vite build.
3. Look in the build output for the upload logs.

Expected Result

Source maps get uploaded after the adapter runs, like on SvelteKit 2. Our last Kit 2 build logged Bundled 2433 files for upload and Uploaded files to Sentry.

Actual Result

Nothing gets uploaded and nothing about it is logged, so every client error since we upgraded to Kit 3 has minified frames. With debug: true the plugin only logs Enabled source map generation in the build options with build.sourcemap: 'hidden'. The source maps will be deleted after they were uploaded to Sentry. After that there's no upload attempt (an invalid token doesn't even produce a 401), and all .map files are still in build/, so the upload/cleanup step never runs. Chunks get the sentry-dbid-… snippet but never the //# debugId= comment.

Additional Context

I think the cause is the SSR check in sentry-sveltekit-debug-id-upload-plugin (packages/sveltekit/src/vite/sourceMaps.ts):

configResolved: config => {
  // `config.build.ssr` is `true` for that first build and `false` in the other ones.
  if (!config.build.ssr) {
    isSSRBuild = false;
  }
},
closeBundle: async () => {
  if (!isSSRBuild) {
    return;
  }
  // flatten + upload

SvelteKit 3 does a single Vite build with ssr and client environments, rather than a separate SSR build, so config.build.ssr is never true and closeBundle always returns early. #21629 fixed the same thing in autoInstrument by using this.environment.name, but sourceMaps.ts still has the old check. The sveltekit-3 e2e app doesn’t seem to test source maps, which would explain why this wasn’t caught.

Our workaround: set sourcemaps: { disable: 'disable-upload' } (on 10.x, unstable_sentryVitePluginOptions: { sourcemaps: { disable: 'disable-upload' } }) so the plugin stamps debug IDs into the output files (since #23754), then run sentry-cli sourcemaps upload build after the build.

Priority

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