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Oct 20, 2025
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fix(nextjs): Update bundler detection #17976

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2 changes: 1 addition & 1 deletion dev-packages/e2e-tests/test-applications/nextjs-16/package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@
"test:build-canary": "pnpm install && pnpm add next@canary && pnpm build",
"test:build-canary-webpack": "pnpm install && pnpm add next@canary && pnpm build-webpack",
"test:assert": "pnpm test:prod && pnpm test:dev",
"test:assert-webpack": "pnpm test:prod"
"test:assert-webpack": "pnpm test:prod && pnpm test:dev-webpack"
},
"dependencies": {
"@sentry/nextjs": "latest || *",
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64 changes: 9 additions & 55 deletions packages/nextjs/src/config/util.ts
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Expand Up @@ -109,66 +109,20 @@ export function supportsNativeDebugIds(version: string): boolean {
}

/**
* Checks if the current Next.js version uses Turbopack as the default bundler.
* Starting from Next.js 15.6.0-canary.38, turbopack became the default for `next build`.
* Determines which bundler is actually being used based on environment variables,
* and CLI flags.
*
* @param version - Next.js version string to check.
* @returns true if the version uses Turbopack by default
* @returns 'turbopack' or 'webpack'
*/
export function isTurbopackDefaultForVersion(version: string): boolean {
if (!version) {
return false;
}

const { major, minor, prerelease } = parseSemver(version);

if (major === undefined || minor === undefined) {
return false;
}
export function detectActiveBundler(): 'turbopack' | 'webpack' {
const turbopackEnv = process.env.TURBOPACK;

// Next.js 16+ uses turbopack by default
if (major >= 16) {
return true;
}
// Check if TURBOPACK env var is set to a truthy value (excluding falsy strings like 'false', '0', '')
const isTurbopackEnabled = turbopackEnv && turbopackEnv !== 'false' && turbopackEnv !== '0';

// For Next.js 15, only canary versions 15.6.0-canary.40+ use turbopack by default
// Stable 15.x releases still use webpack by default
if (major === 15 && minor >= 6 && prerelease && prerelease.startsWith('canary.')) {
if (minor >= 7) {
return true;
}
const canaryNumber = parseInt(prerelease.split('.')[1] || '0', 10);
if (canaryNumber >= 40) {
return true;
}
}

return false;
}

/**
* Determines which bundler is actually being used based on environment variables,
* CLI flags, and Next.js version.
*
* @param nextJsVersion - The Next.js version string
* @returns 'turbopack', 'webpack', or undefined if it cannot be determined
*/
export function detectActiveBundler(nextJsVersion: string | undefined): 'turbopack' | 'webpack' | undefined {
if (process.env.TURBOPACK || process.argv.includes('--turbo')) {
if (isTurbopackEnabled || process.argv.includes('--turbo')) {
return 'turbopack';
}

// Explicit opt-in to webpack via --webpack flag
if (process.argv.includes('--webpack')) {
} else {
return 'webpack';
}

// Fallback to version-based default behavior
if (nextJsVersion) {
const turbopackIsDefault = isTurbopackDefaultForVersion(nextJsVersion);
return turbopackIsDefault ? 'turbopack' : 'webpack';
}

// Unlikely but at this point, we just assume webpack for older behavior
return 'webpack';
}
2 changes: 1 addition & 1 deletion packages/nextjs/src/config/withSentryConfig.ts
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Expand Up @@ -261,7 +261,7 @@ function getFinalConfigObject(
nextMajor = major;
}

const activeBundler = detectActiveBundler(nextJsVersion);
const activeBundler = detectActiveBundler();
const isTurbopack = activeBundler === 'turbopack';
const isWebpack = activeBundler === 'webpack';
const isTurbopackSupported = supportsProductionCompileHook(nextJsVersion ?? '');
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161 changes: 12 additions & 149 deletions packages/nextjs/test/config/util.test.ts
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Expand Up @@ -213,117 +213,6 @@ describe('util', () => {
});
});

describe('isTurbopackDefaultForVersion', () => {
describe('returns true for versions where turbopack is default', () => {
it.each([
// Next.js 16+ stable versions
['16.0.0', 'Next.js 16.0.0 stable'],
['16.0.1', 'Next.js 16.0.1 stable'],
['16.1.0', 'Next.js 16.1.0 stable'],
['16.2.5', 'Next.js 16.2.5 stable'],

// Next.js 16+ pre-release versions
['16.0.0-rc.1', 'Next.js 16.0.0-rc.1'],
['16.0.0-canary.1', 'Next.js 16.0.0-canary.1'],
['16.1.0-beta.2', 'Next.js 16.1.0-beta.2'],

// Next.js 17+
['17.0.0', 'Next.js 17.0.0'],
['18.0.0', 'Next.js 18.0.0'],
['20.0.0', 'Next.js 20.0.0'],

// Next.js 15.6.0-canary.40+ (boundary case)
['15.6.0-canary.40', 'Next.js 15.6.0-canary.40 (exact threshold)'],
['15.6.0-canary.41', 'Next.js 15.6.0-canary.41'],
['15.6.0-canary.42', 'Next.js 15.6.0-canary.42'],
['15.6.0-canary.100', 'Next.js 15.6.0-canary.100'],

// Next.js 15.7+ canary versions
['15.7.0-canary.1', 'Next.js 15.7.0-canary.1'],
['15.7.0-canary.50', 'Next.js 15.7.0-canary.50'],
['15.8.0-canary.1', 'Next.js 15.8.0-canary.1'],
['15.10.0-canary.1', 'Next.js 15.10.0-canary.1'],
])('returns true for %s (%s)', version => {
expect(util.isTurbopackDefaultForVersion(version)).toBe(true);
});
});

describe('returns false for versions where webpack is still default', () => {
it.each([
// Next.js 15.6.0-canary.39 and below
['15.6.0-canary.39', 'Next.js 15.6.0-canary.39 (just below threshold)'],
['15.6.0-canary.36', 'Next.js 15.6.0-canary.36'],
['15.6.0-canary.38', 'Next.js 15.6.0-canary.38'],
['15.6.0-canary.0', 'Next.js 15.6.0-canary.0'],

// Next.js 15.6.x stable releases (NOT canary)
['15.6.0', 'Next.js 15.6.0 stable'],
['15.6.1', 'Next.js 15.6.1 stable'],
['15.6.2', 'Next.js 15.6.2 stable'],
['15.6.10', 'Next.js 15.6.10 stable'],

// Next.js 15.6.x rc releases (NOT canary)
['15.6.0-rc.1', 'Next.js 15.6.0-rc.1'],
['15.6.0-rc.2', 'Next.js 15.6.0-rc.2'],

// Next.js 15.7+ stable releases (NOT canary)
['15.7.0', 'Next.js 15.7.0 stable'],
['15.8.0', 'Next.js 15.8.0 stable'],
['15.10.0', 'Next.js 15.10.0 stable'],

// Next.js 15.5 and below (all versions)
['15.5.0', 'Next.js 15.5.0'],
['15.5.0-canary.100', 'Next.js 15.5.0-canary.100'],
['15.4.1', 'Next.js 15.4.1'],
['15.0.0', 'Next.js 15.0.0'],
['15.0.0-canary.1', 'Next.js 15.0.0-canary.1'],

// Next.js 14.x and below
['14.2.0', 'Next.js 14.2.0'],
['14.0.0', 'Next.js 14.0.0'],
['14.0.0-canary.50', 'Next.js 14.0.0-canary.50'],
['13.5.0', 'Next.js 13.5.0'],
['13.0.0', 'Next.js 13.0.0'],
['12.0.0', 'Next.js 12.0.0'],
])('returns false for %s (%s)', version => {
expect(util.isTurbopackDefaultForVersion(version)).toBe(false);
});
});

describe('edge cases', () => {
it.each([
['', 'empty string'],
['invalid', 'invalid version string'],
['15', 'missing minor and patch'],
['15.6', 'missing patch'],
['not.a.version', 'completely invalid'],
['15.6.0-alpha.1', 'alpha prerelease (not canary)'],
['15.6.0-beta.1', 'beta prerelease (not canary)'],
])('returns false for %s (%s)', version => {
expect(util.isTurbopackDefaultForVersion(version)).toBe(false);
});
});

describe('canary number parsing edge cases', () => {
it.each([
['15.6.0-canary.', 'canary with no number'],
['15.6.0-canary.abc', 'canary with non-numeric value'],
['15.6.0-canary.38.extra', 'canary with extra segments'],
])('handles malformed canary versions: %s (%s)', version => {
// Should not throw, just return appropriate boolean
expect(() => util.isTurbopackDefaultForVersion(version)).not.toThrow();
});

it('handles canary.40 exactly (boundary)', () => {
expect(util.isTurbopackDefaultForVersion('15.6.0-canary.40')).toBe(true);
});

it('handles canary.39 exactly (boundary)', () => {
expect(util.isTurbopackDefaultForVersion('15.6.0-canary.39')).toBe(false);
});
});
});

describe('detectActiveBundler', () => {
const originalArgv = process.argv;
const originalEnv = process.env;
Expand All @@ -341,52 +230,26 @@ describe('util', () => {

it('returns turbopack when TURBOPACK env var is set', () => {
process.env.TURBOPACK = '1';
expect(util.detectActiveBundler('15.5.0')).toBe('turbopack');
});

it('returns webpack when --webpack flag is present', () => {
process.argv.push('--webpack');
expect(util.detectActiveBundler('16.0.0')).toBe('webpack');
});

it('returns turbopack for Next.js 16+ by default', () => {
expect(util.detectActiveBundler('16.0.0')).toBe('turbopack');
expect(util.detectActiveBundler('17.0.0')).toBe('turbopack');
});

it('returns turbopack for Next.js 15.6.0-canary.40+', () => {
expect(util.detectActiveBundler('15.6.0-canary.40')).toBe('turbopack');
expect(util.detectActiveBundler('15.6.0-canary.50')).toBe('turbopack');
expect(util.detectActiveBundler()).toBe('turbopack');
});

it('returns webpack for Next.js 15.6.0 stable', () => {
expect(util.detectActiveBundler('15.6.0')).toBe('webpack');
it('returns turbopack when TURBOPACK env var is set to auto', () => {
process.env.TURBOPACK = 'auto';
expect(util.detectActiveBundler()).toBe('turbopack');
});

it('returns webpack for Next.js 15.5.x and below', () => {
expect(util.detectActiveBundler('15.5.0')).toBe('webpack');
expect(util.detectActiveBundler('15.0.0')).toBe('webpack');
expect(util.detectActiveBundler('14.2.0')).toBe('webpack');
it('returns webpack when TURBOPACK env var is undefined', () => {
process.env.TURBOPACK = undefined;
expect(util.detectActiveBundler()).toBe('webpack');
});

it('returns webpack when version is undefined', () => {
expect(util.detectActiveBundler(undefined)).toBe('webpack');
it('returns webpack when TURBOPACK env var is false', () => {
process.env.TURBOPACK = 'false';
expect(util.detectActiveBundler()).toBe('webpack');
});

it('prioritizes TURBOPACK env var over version detection', () => {
process.env.TURBOPACK = '1';
expect(util.detectActiveBundler('14.0.0')).toBe('turbopack');
});

it('prioritizes --webpack flag over version detection', () => {
process.argv.push('--webpack');
expect(util.detectActiveBundler('16.0.0')).toBe('webpack');
});

it('prioritizes TURBOPACK env var over --webpack flag', () => {
process.env.TURBOPACK = '1';
process.argv.push('--webpack');
expect(util.detectActiveBundler('15.5.0')).toBe('turbopack');
it('returns webpack when TURBOPACK env var is not set', () => {
expect(util.detectActiveBundler()).toBe('webpack');
});
});
});
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