From 95c67329e487bae97cdf370daaca0bc218a004d0 Mon Sep 17 00:00:00 2001
From: Charly Gomez <charly.gomez1310@gmail.com>
Date: Thu, 18 Jun 2026 12:53:10 +0200
Subject: [PATCH] .

---
 .../sveltekit-3/tests/errors.server.test.ts   |  7 +--
 packages/sveltekit/src/vite/autoInstrument.ts |  8 +++-
 .../test/vite/autoInstrument.test.ts          | 45 +++++++++++++++++++
 3 files changed, 53 insertions(+), 7 deletions(-)

diff --git a/dev-packages/e2e-tests/test-applications/sveltekit-3/tests/errors.server.test.ts b/dev-packages/e2e-tests/test-applications/sveltekit-3/tests/errors.server.test.ts
index ee17fde7c048..d660cb6198d1 100644
--- a/dev-packages/e2e-tests/test-applications/sveltekit-3/tests/errors.server.test.ts
+++ b/dev-packages/e2e-tests/test-applications/sveltekit-3/tests/errors.server.test.ts
@@ -2,12 +2,7 @@ import { expect, test } from '@playwright/test';
 import { waitForError } from '@sentry-internal/test-utils';
 
 test.describe('server-side errors', () => {
-  // FIXME(sveltekit-3): the universal load function's frame is reported as `load$1` (not `load`)
-  // because the SDK still wraps universal `+page.ts` load in the server build. Unlike server-only
-  // load, this isn't suppressed by native-tracing detection: the wrapper is skipped via
-  // `config.build.ssr`, which is unreliable under Vite 8's Environment API. Unskip once the SDK
-  // detects the server environment via the Vite Environment API.
-  test.skip('captures universal load error', async ({ page }) => {
+  test('captures universal load error', async ({ page }) => {
     const errorEventPromise = waitForError('sveltekit-3', errorEvent => {
       return errorEvent?.exception?.values?.[0]?.value === 'Universal Load Error (server)';
     });
diff --git a/packages/sveltekit/src/vite/autoInstrument.ts b/packages/sveltekit/src/vite/autoInstrument.ts
index a142d74f01cc..6b2f50928ee3 100644
--- a/packages/sveltekit/src/vite/autoInstrument.ts
+++ b/packages/sveltekit/src/vite/autoInstrument.ts
@@ -75,7 +75,13 @@ export function makeAutoInstrumentationPlugin(options: AutoInstrumentPluginOptio
     },
 
     async load(id) {
-      if (onlyInstrumentClient && isServerBuild) {
+      // On Vite 6+ `config.build.ssr` captured in `configResolved` no longer reliably reflects the per-environment build.
+      // Prefer the environment of the current build (`this.environment.name === 'ssr'`) and fall back to
+      // `isServerBuild` for older Vite versions that don't expose environments.
+      const environmentName = (this as { environment?: { name?: string } }).environment?.name;
+      const isServerEnvironment = environmentName != null ? environmentName === 'ssr' : !!isServerBuild;
+
+      if (onlyInstrumentClient && isServerEnvironment) {
         return null;
       }
 
diff --git a/packages/sveltekit/test/vite/autoInstrument.test.ts b/packages/sveltekit/test/vite/autoInstrument.test.ts
index 54f6ccb6c425..4a3d3cce4476 100644
--- a/packages/sveltekit/test/vite/autoInstrument.test.ts
+++ b/packages/sveltekit/test/vite/autoInstrument.test.ts
@@ -280,6 +280,51 @@ describe('makeAutoInstrumentationPlugin()', () => {
       );
     });
   });
+
+  describe('when the server build is detected via the Vite Environment API', () => {
+    // On Vite 6+ `config.build.ssr` no longer reliably reflects the per-environment
+    // build, so the plugin relies on the current environment (`this.environment.name`). When
+    // `onlyInstrumentClient` is `true`, universal load must not be wrapped in the `ssr` environment
+    // (but should still be wrapped in `client`), even when `config.build.ssr`/`configResolved`
+    // didn't flag a server build.
+    it.each(['path/to/+page.ts', 'path/to/+layout.js', 'path/to/+page.server.ts'])(
+      "doesn't wrap %s in the `ssr` environment",
+      async (path: string) => {
+        const plugin = makeAutoInstrumentationPlugin({
+          debug: false,
+          load: true,
+          serverLoad: true,
+          onlyInstrumentClient: true,
+        });
+
+        // `configResolved` is intentionally not called - `isServerBuild` stays `undefined`
+        // @ts-expect-error this exists and is callable; bind `this.environment` like Vite does
+        const loadResult = await plugin.load.call({ environment: { name: 'ssr' } }, path);
+
+        expect(loadResult).toEqual(null);
+      },
+    );
+
+    it('still wraps universal load in the `client` environment', async () => {
+      const plugin = makeAutoInstrumentationPlugin({
+        debug: false,
+        load: true,
+        serverLoad: true,
+        onlyInstrumentClient: true,
+      });
+
+      const path = 'path/to/+page.ts';
+      // @ts-expect-error this exists and is callable; bind `this.environment` like Vite does
+      const loadResult = await plugin.load.call({ environment: { name: 'client' } }, path);
+
+      expect(loadResult).toBe(
+        'import { wrapLoadWithSentry } from "@sentry/sveltekit";' +
+          `import * as userModule from "${path}?sentry-auto-wrap";` +
+          'export const load = userModule.load ? wrapLoadWithSentry(userModule.load) : undefined;' +
+          `export * from "${path}?sentry-auto-wrap";`,
+      );
+    });
+  });
 });
 
 describe('canWrapLoad', () => {