From b96fd6fcfb6934a4cbdfe4375f24593d37907e73 Mon Sep 17 00:00:00 2001
From: RulaKhaled <rola.abuhasna@sentry.io>
Date: Wed, 28 May 2025 12:48:46 +0200
Subject: [PATCH 1/2] fix(nextjs): Skip re instrumentating on generate phase of
 experimental build mode

---
 .../nextjs/src/config/withSentryConfig.ts     | 22 ++++++++++++++++
 .../test/config/withSentryConfig.test.ts      | 25 +++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/packages/nextjs/src/config/withSentryConfig.ts b/packages/nextjs/src/config/withSentryConfig.ts
index 7eedcc763e9b..9489554f2ed1 100644
--- a/packages/nextjs/src/config/withSentryConfig.ts
+++ b/packages/nextjs/src/config/withSentryConfig.ts
@@ -15,6 +15,7 @@ import { getNextjsVersion } from './util';
 import { constructWebpackConfigFunction } from './webpack';
 
 let showedExportModeTunnelWarning = false;
+let showedExperimentalBuildModeWarning = false;
 
 /**
  * Modifies the passed in Next.js configuration with automatic build-time instrumentation and source map upload.
@@ -67,6 +68,27 @@ function getFinalConfigObject(
     }
   }
 
+  if (process.argv.includes('--experimental-build-mode')) {
+    if (!showedExperimentalBuildModeWarning) {
+      showedExperimentalBuildModeWarning = true;
+      // eslint-disable-next-line no-console
+      console.warn(
+        '[@sentry/nextjs] The Sentry Next.js SDK does not currently fully support next build --experimental-build-mode',
+      );
+    }
+    if (process.argv.includes('generate')) {
+      // Next.js v15.3.0-canary.1 splits the experimental build into two phases:
+      // 1. compile: Code compilation
+      // 2. generate: Environment variable inlining and prerendering (We don't instrument this phase, we inline in the compile phase)
+      //
+      // We assume a single “full” build and reruns Webpack instrumentation in both phases.
+      // During the generate step it collides with Next.js’s new inliner (they do some bad replacements in the inliner)
+      // producing malformed JS and build failures.
+      // We skip Sentry processing during generate to avoid this issue.
+      return incomingUserNextConfigObject;
+    }
+  }
+
   setUpBuildTimeVariables(incomingUserNextConfigObject, userSentryOptions, releaseName);
 
   const nextJsVersion = getNextjsVersion();
diff --git a/packages/nextjs/test/config/withSentryConfig.test.ts b/packages/nextjs/test/config/withSentryConfig.test.ts
index 6ad9a83e6791..f9db1a68771e 100644
--- a/packages/nextjs/test/config/withSentryConfig.test.ts
+++ b/packages/nextjs/test/config/withSentryConfig.test.ts
@@ -50,4 +50,29 @@ describe('withSentryConfig', () => {
 
     expect(exportedNextConfigFunction).toHaveBeenCalledWith(defaultRuntimePhase, defaultsObject);
   });
+
+  it('handles experimental build mode correctly', () => {
+    const originalArgv = process.argv;
+    const consoleWarnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    try {
+      process.argv = [...originalArgv, '--experimental-build-mode'];
+      materializeFinalNextConfig(exportedNextConfig);
+
+      expect(consoleWarnSpy).toHaveBeenCalledWith(
+        '[@sentry/nextjs] The Sentry Next.js SDK does not currently fully support next build --experimental-build-mode',
+      );
+
+      // Generate phase
+      process.argv = [...process.argv, 'generate'];
+      const generateConfig = materializeFinalNextConfig(exportedNextConfig);
+
+      expect(generateConfig).toEqual(exportedNextConfig);
+
+      expect(consoleWarnSpy).toHaveBeenCalledTimes(1);
+    } finally {
+      process.argv = originalArgv;
+      consoleWarnSpy.mockRestore();
+    }
+  });
 });

From 681247c077a99812dc9e55213495cd4b6995705d Mon Sep 17 00:00:00 2001
From: Rola Abuhasna <rola.abuhasna@sentry.io>
Date: Tue, 3 Jun 2025 15:24:02 +0200
Subject: [PATCH 2/2] Update packages/nextjs/src/config/withSentryConfig.ts

Co-authored-by: Charly Gomez <charly.gomez@sentry.io>
---
 packages/nextjs/src/config/withSentryConfig.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/nextjs/src/config/withSentryConfig.ts b/packages/nextjs/src/config/withSentryConfig.ts
index 9489554f2ed1..543f271c1999 100644
--- a/packages/nextjs/src/config/withSentryConfig.ts
+++ b/packages/nextjs/src/config/withSentryConfig.ts
@@ -82,7 +82,7 @@ function getFinalConfigObject(
       // 2. generate: Environment variable inlining and prerendering (We don't instrument this phase, we inline in the compile phase)
       //
       // We assume a single “full” build and reruns Webpack instrumentation in both phases.
-      // During the generate step it collides with Next.js’s new inliner (they do some bad replacements in the inliner)
+      // During the generate step it collides with Next.js’s inliner
       // producing malformed JS and build failures.
       // We skip Sentry processing during generate to avoid this issue.
       return incomingUserNextConfigObject;