aleclarson · Nov 10, 2026
diff --git a/packages/vite/hmr/server/websocket-import-records-fallback.spec.ts b/packages/vite/hmr/server/websocket-import-records-fallback.spec.ts
@@ -0,0 +1,52 @@
+import { describe, expect, it, vi } from 'vitest';
+
+// parseAst (Oxc) rejected → the Babel fallback must produce identical records.
+vi.mock('vite', async (importOriginal) => {
+	const original = await importOriginal<typeof import('vite')>();
+	return {
+		...original,
+		parseAst: () => {
+			throw new Error('simulated Oxc parse failure');
+		},
+	};
+});
+
+const { collectTopLevelImportRecords } = await import('./websocket-served-module-helpers.js');
+const { ensureNativeScriptModuleBindings } = await import('./websocket-module-bindings.js');
+
+describe('collectTopLevelImportRecords (Babel fallback)', () => {
+	it('produces the same records when parseAst throws', () => {
+		const code = `const s = "héllo→";\nimport def, { a, b as c, "d-e" as f } from "pkg";\nimport type { T } from "./t";`;
+		const records = collectTopLevelImportRecords(code);
+		expect(records).toHaveLength(2);
+		expect(records[0].source).toBe('pkg');
+		expect(records[0].text).toBe(`import def, { a, b as c, "d-e" as f } from "pkg";`);
+		expect(records[0].hasOnlyNamedSpecifiers).toBe(false);
+		expect(records[0].namedBindings).toEqual([
+			{ importedName: 'a', text: 'a' },
+			{ importedName: 'b', text: 'b as c' },
+			{ importedName: 'd-e', text: '"d-e" as f' },
+		]);
+		expect(records[1].source).toBe('./t');
+	});
+
+	it('still rewrites a vendor plugin import through the Babel fallback', () => {
+		const input = `import { defineStore } from "pinia";\nexport const useServices = defineStore('services', () => ({}));\n`;
+		const out = ensureNativeScriptModuleBindings(input);
+		expect(out).not.toMatch(/from\s+["']pinia["']/);
+		expect(out).toContain('globalThis.__nsVendorRegistry');
+	});
+});
+
+const { collectStaticImportDefaultIntents } = await import('./websocket-served-module-helpers.js');
+
+describe('collectStaticImportDefaultIntents (Babel fallback)', () => {
+	it('produces the same intents when parseAst throws', () => {
+		const code = `import def, { a } from "x";\nimport { b } from "y";\nimport type { T } from "./t";`;
+		expect(collectStaticImportDefaultIntents(code)).toEqual([
+			{ src: 'x', wantsDefault: true },
+			{ src: 'y', wantsDefault: false },
+			{ src: './t', wantsDefault: false },
+		]);
+	});
+});
diff --git a/packages/vite/hmr/server/websocket-module-bindings.ts b/packages/vite/hmr/server/websocket-module-bindings.ts
@@ -7,7 +7,7 @@ import { astExtractImportsAndStripTypes } from '../helpers/ast-extract.js';
 import { getProjectRootPath } from '../../helpers/project.js';
 import { extractRootPackageName } from '../shared/package-classifier.js';
 import { isEsmFrameworkPackageSpecifier, isLikelyNativeScriptPluginSpecifier, isLikelyNativeScriptRuntimePluginSpecifier, normalizeNodeModulesSpecifier, resolveInternalRuntimePluginBareSpecifier, resolveNodeModulesPackageBoundary, resolveVendorFromCandidate, shouldPreserveBareRuntimePluginSubpathImport } from './websocket-module-specifiers.js';
-import { MODULE_IMPORT_ANALYSIS_PLUGINS } from './websocket-served-module-helpers.js';
+import { MODULE_IMPORT_ANALYSIS_PLUGINS, parseTopLevelStatements } from './websocket-served-module-helpers.js';
 import { getVendorManifest } from '../shared/vendor/registry.js';
 import { isBuiltinModuleId } from '../../helpers/builtin-modules.js';
 
@@ -76,33 +76,36 @@ function hasExplicitRuntimePluginScriptExtension(segment: string): boolean {
 }
 
 function collectTopLevelImportRecords(code: string): TopLevelImportRecord[] {
-	try {
-		const ast = babelParse(code, {
-			sourceType: 'module',
-			plugins: [...MODULE_IMPORT_ANALYSIS_PLUGINS],
-		}) as any;
-		const body = ast?.program?.body;
-		if (!Array.isArray(body)) {
-			return [];
-		}
-
-		return body
-			.filter((node: any) => node?.type === 'ImportDeclaration' && typeof node.start === 'number' && typeof node.end === 'number' && typeof node.source?.value === 'string')
-			.map((node: any) => {
-				const text = code.slice(node.start as number, node.end as number);
-				const clause = Array.isArray(node.specifiers) && node.specifiers.length > 0 ? text.match(/^\s*import\s+([\s\S]*?)\s+from\s+["'][^"']+["'];?\s*$/)?.[1]?.trim() || null : null;
-				return {
-					start: node.start as number,
-					end: node.end as number,
-					text,
-					source: node.source.value as string,
-					clause,
-					isTypeOnly: node.importKind === 'type',
-				};
-			});
-	} catch {
+	let body = parseTopLevelStatements(code);
+	if (!body) {
+		try {
+			body =
+				(
+					babelParse(code, {
+						sourceType: 'module',
+						plugins: [...MODULE_IMPORT_ANALYSIS_PLUGINS],
+					}) as any
+				)?.program?.body ?? null;
+		} catch {}
+	}
+	if (!Array.isArray(body)) {
 		return [];
 	}
+
+	return body
+		.filter((node: any) => node?.type === 'ImportDeclaration' && typeof node.start === 'number' && typeof node.end === 'number' && typeof node.source?.value === 'string')
+		.map((node: any) => {
+			const text = code.slice(node.start as number, node.end as number);
+			const clause = Array.isArray(node.specifiers) && node.specifiers.length > 0 ? text.match(/^\s*import\s+([\s\S]*?)\s+from\s+["'][^"']+["'];?\s*$/)?.[1]?.trim() || null : null;
+			return {
+				start: node.start as number,
+				end: node.end as number,
+				text,
+				source: node.source.value as string,
+				clause,
+				isTypeOnly: node.importKind === 'type',
+			};
+		});
 }
 
 /** Value re-exports (`export * from 'x'`, `export { a } from 'x'`), as the positions of their source literals. */

diff --git a/packages/vite/hmr/server/websocket-ns-m.ts b/packages/vite/hmr/server/websocket-ns-m.ts
@@ -1,8 +1,5 @@
 import type { TransformResult, ViteDevServer } from 'vite';
 
-import { parse as babelParse } from '@babel/parser';
-import traverse from '@babel/traverse';
-
 import { sanitizeStrayCoreReferences } from './core-sanitize.js';
 import { getMonorepoWorkspaceRoot } from '../../helpers/project.js';
 import { isRuntimeGraphExcludedPath } from './runtime-graph-filter.js';
@@ -12,7 +9,7 @@ import { createNsMRequestContext, resolveFsAnchoredSpec, resolveNsMTransformedMo
 import { setDeviceModuleHeaders } from './route-helpers.js';
 import { RAW_QUERY_PATTERN } from './constants.js';
 import { CSS_MODULE_RE, buildCssRegisterSnippetFromVar, normalizeCssForDevice } from './css-device-module.js';
-import { assertNoOptimizedArtifacts, buildBootProgressSnippet, canonicalizeRtImports, dedupeRtNamedImportsAgainstDestructures, deduplicateLinkerImports, ensureDestructureCoreImports, ensureGuardPlainDynamicImports, ensureVariableDynamicImportHelper, expandStarExports, hasEsmDefaultExport, hoistTopLevelStaticImports, MODULE_IMPORT_ANALYSIS_PLUGINS, wrapCommonJsModuleForDevice, ensureWorkerEntryGlobalsImport, classifyServedRequest } from './websocket-served-module-helpers.js';
+import { assertNoOptimizedArtifacts, buildBootProgressSnippet, canonicalizeRtImports, dedupeRtNamedImportsAgainstDestructures, deduplicateLinkerImports, ensureDestructureCoreImports, ensureGuardPlainDynamicImports, ensureVariableDynamicImportHelper, expandStarExports, hasEsmDefaultExport, hoistTopLevelStaticImports, wrapCommonJsModuleForDevice, ensureWorkerEntryGlobalsImport, classifyServedRequest, collectStaticImportDefaultIntents } from './websocket-served-module-helpers.js';
 import { cleanCode, collectImportDependencies, isWorkerEntryModuleId, processCodeForDevice, rewriteImports } from './websocket-device-transform.js';
 import { REQUIRE_GUARD_SNIPPET } from './require-guard.js';
 import { getServerOrigin } from './server-origin.js';
@@ -21,8 +18,6 @@ import { appendInlineSourceMap, buildServedModuleSourceMap, type InputSourceMap
 import { getSharedDepsBundleService, registerDepsBundleRoute, type DepsBundleService } from './deps-bundle.js';
 import type { FrameworkServedModuleContext, FrameworkServerStrategy } from './framework-strategy.js';
 
-const babelTraverse: any = (traverse as any)?.default || (traverse as any);
-
 type SharedTransformRequestFn = (url: string, timeoutMs?: number) => Promise<TransformResult | null>;
 type UpsertGraphModuleFn = (rawId: string, code: string, deps: string[], options?: { bumpVersion?: boolean; emitDeltaOnInsert?: boolean; broadcastDelta?: boolean }) => void;
 
@@ -508,19 +503,7 @@ export function registerNsModuleServerRoute(server: ViteDevServer, options: Regi
 			try {
 				const devCheck = process.env.NODE_ENV !== 'production';
 				if (devCheck) {
-					const ast = babelParse(code, {
-						sourceType: 'module',
-						plugins: MODULE_IMPORT_ANALYSIS_PLUGINS,
-					}) as any;
-					const imports: Array<{ src: string; wantsDefault: boolean }> = [];
-					babelTraverse(ast, {
-						ImportDeclaration(p: any) {
-							const src = p.node.source.value;
-							if (typeof src !== 'string') return;
-							const wantsDefault = p.node.specifiers.some((s: any) => s.type === 'ImportDefaultSpecifier');
-							imports.push({ src, wantsDefault });
-						},
-					});
+					const imports = collectStaticImportDefaultIntents(code);
 					// Resolve and verify each static import that asks for default
 					for (const imp of imports) {
 						if (!imp.wantsDefault) continue;

diff --git a/packages/vite/hmr/server/websocket-served-module-helpers.spec.ts b/packages/vite/hmr/server/websocket-served-module-helpers.spec.ts
@@ -44,3 +44,92 @@ describe('hasEsmDefaultExport', () => {
 		expect(hasEsmDefaultExport('export default (;')).toBeNull();
 	});
 });
+
+import { collectTopLevelImportRecords } from './websocket-served-module-helpers.js';
+import { ensureNativeScriptModuleBindings } from './websocket-module-bindings.js';
+
+describe('collectTopLevelImportRecords (Oxc parseAst path)', () => {
+	it('collects default, named, and string-named specifiers', () => {
+		const code = `import def, { a, b as c, "d-e" as f } from "pkg";`;
+		const records = collectTopLevelImportRecords(code);
+		expect(records).toHaveLength(1);
+		expect(records[0].source).toBe('pkg');
+		expect(records[0].text).toBe(code);
+		expect(records[0].start).toBe(0);
+		expect(records[0].end).toBe(code.length);
+		expect(records[0].hasOnlyNamedSpecifiers).toBe(false);
+		expect(records[0].namedBindings).toEqual([
+			{ importedName: 'a', text: 'a' },
+			{ importedName: 'b', text: 'b as c' },
+			{ importedName: 'd-e', text: '"d-e" as f' },
+		]);
+	});
+
+	it('marks named-only specifier lists and exact text after non-ASCII content', () => {
+		const code = `const s = "héllo→";\nimport { x } from "m";`;
+		const records = collectTopLevelImportRecords(code);
+		expect(records).toHaveLength(1);
+		expect(records[0].text).toBe(`import { x } from "m";`);
+		expect(records[0].hasOnlyNamedSpecifiers).toBe(true);
+	});
+
+	it('collects import type declarations', () => {
+		const records = collectTopLevelImportRecords(`import type { T } from "./t";`);
+		expect(records).toHaveLength(1);
+		expect(records[0].source).toBe('./t');
+	});
+
+	it('handles TS+JSX input', () => {
+		const code = `import { render } from "x";\ninterface P { a: number }\nconst el = <div a={1} />;\nrender(el);\n`;
+		const records = collectTopLevelImportRecords(code);
+		expect(records).toHaveLength(1);
+		expect(records[0].source).toBe('x');
+	});
+
+	it('returns [] for code with no imports', () => {
+		expect(collectTopLevelImportRecords(`const a = 1;\nexport { a };`)).toEqual([]);
+	});
+
+	it('parses a long minified line full of block comments without Babel quadratic scan', () => {
+		// Babel's skipBlockComment rescans to the next line break per comment;
+		// 12000 comments over a ~20MB single line is ~10s through the old path.
+		// Measured on this machine: Babel 10.32s, Oxc 0.047s.
+		const code = `import {a} from "m";\n` + '/*#__PURE__*/'.repeat(12000) + 'const s="' + 'x'.repeat(20 * 1000 * 1000) + '";';
+		const t0 = performance.now();
+		const records = collectTopLevelImportRecords(code);
+		const ms = performance.now() - t0;
+		expect(records).toHaveLength(1);
+		expect(records[0].source).toBe('m');
+		expect(ms).toBeLessThan(2000);
+	}, 30000);
+});
+
+describe('ensureNativeScriptModuleBindings via Oxc import records', () => {
+	it('still rewrites a vendor plugin import', () => {
+		const input = `import { defineStore } from "pinia";\nexport const useServices = defineStore('services', () => ({}));\n`;
+		const out = ensureNativeScriptModuleBindings(input);
+		expect(out).not.toMatch(/from\s+["']pinia["']/);
+		expect(out).toContain('globalThis.__nsVendorRegistry');
+	});
+});
+
+import { collectStaticImportDefaultIntents } from './websocket-served-module-helpers.js';
+
+describe('collectStaticImportDefaultIntents (Oxc parseAst path)', () => {
+	it('reports default/named/namespace mixes', () => {
+		const code = `import def, { a } from "x";\nimport { b } from "y";\nimport * as ns from "z";\nimport type { T } from "./t";`;
+		expect(collectStaticImportDefaultIntents(code)).toEqual([
+			{ src: 'x', wantsDefault: true },
+			{ src: 'y', wantsDefault: false },
+			{ src: 'z', wantsDefault: false },
+			{ src: './t', wantsDefault: false },
+		]);
+	});
+
+	it('handles the long-line comment payload fast', () => {
+		const code = `import {a} from "m";\n` + '/*#__PURE__*/'.repeat(12000) + 'const s="' + 'x'.repeat(20 * 1000 * 1000) + '";';
+		const t0 = performance.now();
+		expect(collectStaticImportDefaultIntents(code)).toEqual([{ src: 'm', wantsDefault: false }]);
+		expect(performance.now() - t0).toBeLessThan(2000);
+	}, 30000);
+});
diff --git a/packages/vite/hmr/server/websocket-served-module-helpers.ts b/packages/vite/hmr/server/websocket-served-module-helpers.ts
@@ -1,7 +1,11 @@
 import { parse as babelParse } from '@babel/parser';
+import traverse from '@babel/traverse';
 import * as t from '@babel/types';
 import { existsSync, readFileSync } from 'fs';
 import * as path from 'path';
+import { parseAst } from 'vite';
+
+const babelTraverse: any = (traverse as any)?.default || (traverse as any);
 
 import * as PAT from './constants.js';
 import { isDeepCoreSubpath } from './core-sanitize.js';
@@ -130,41 +134,90 @@ export type TopLevelImportRecord = {
 	namedBindings: Array<{ importedName: string; text: string }>;
 };
 
+/**
+ * Top-level statements via Vite's native (Oxc) parser. Babel's block-comment
+ * line tracking rescans to the next line break for every comment, so long
+ * minified lines with many comments parse quadratically. Returns null when
+ * Oxc rejects the code so callers can fall back to Babel.
+ */
+export function parseTopLevelStatements(code: string): any[] | null {
+	try {
+		const ast = parseAst(code, { lang: 'tsx' }) as any;
+		return Array.isArray(ast?.body) ? ast.body : null;
+	} catch {
+		return null;
+	}
+}
+
+/**
+ * Static import sources and whether each asks for a default binding.
+ */
+export function collectStaticImportDefaultIntents(code: string): Array<{ src: string; wantsDefault: boolean }> {
+	const body = parseTopLevelStatements(code);
+	if (body) {
+		const imports: Array<{ src: string; wantsDefault: boolean }> = [];
+		for (const node of body) {
+			if (node?.type !== 'ImportDeclaration' || typeof node.source?.value !== 'string') continue;
+			imports.push({
+				src: node.source.value,
+				wantsDefault: Array.isArray(node.specifiers) && node.specifiers.some((s: any) => s?.type === 'ImportDefaultSpecifier'),
+			});
+		}
+		return imports;
+	}
+	const ast = babelParse(code, {
+		sourceType: 'module',
+		plugins: MODULE_IMPORT_ANALYSIS_PLUGINS,
+	}) as any;
+	const imports: Array<{ src: string; wantsDefault: boolean }> = [];
+	babelTraverse(ast, {
+		ImportDeclaration(p: any) {
+			const src = p.node.source.value;
+			if (typeof src !== 'string') return;
+			imports.push({ src, wantsDefault: p.node.specifiers.some((s: any) => s.type === 'ImportDefaultSpecifier') });
+		},
+	});
+	return imports;
+}
+
 export function collectTopLevelImportRecords(code: string): TopLevelImportRecord[] {
 	if (!code || typeof code !== 'string' || !/\bimport\b/.test(code)) {
 		return [];
 	}
 
-	try {
-		const ast = babelParse(code, {
-			sourceType: 'module',
-			plugins: MODULE_IMPORT_ANALYSIS_PLUGINS,
-		}) as any;
-		const body = ast?.program?.body;
-		if (!Array.isArray(body)) {
-			return [];
-		}
-
-		return body
-			.filter((node: any) => t.isImportDeclaration(node) && typeof node.start === 'number' && typeof node.end === 'number' && typeof node.source?.value === 'string')
-			.map((node: any) => ({
-				start: node.start as number,
-				end: node.end as number,
-				text: code.slice(node.start as number, node.end as number),
-				source: node.source.value as string,
-				hasOnlyNamedSpecifiers: Array.isArray(node.specifiers) && node.specifiers.length > 0 && node.specifiers.every((spec: any) => t.isImportSpecifier(spec)),
-				namedBindings: Array.isArray(node.specifiers)
-					? node.specifiers
-							.filter((spec: any) => t.isImportSpecifier(spec) && typeof spec.start === 'number' && typeof spec.end === 'number')
-							.map((spec: any) => ({
-								importedName: t.isIdentifier(spec.imported) ? spec.imported.name : String(spec.imported?.value || ''),
-								text: code.slice(spec.start as number, spec.end as number),
-							}))
-					: [],
-			}));
-	} catch {
+	let body = parseTopLevelStatements(code);
+	if (!body) {
+		try {
+			body =
+				(
+					babelParse(code, {
+						sourceType: 'module',
+						plugins: MODULE_IMPORT_ANALYSIS_PLUGINS,
+					}) as any
+				)?.program?.body ?? null;
+		} catch {}
+	}
+	if (!Array.isArray(body)) {
 		return [];
 	}
+
+	return body
+		.filter((node: any) => node?.type === 'ImportDeclaration' && typeof node.start === 'number' && typeof node.end === 'number' && typeof node.source?.value === 'string')
+		.map((node: any) => ({
+			start: node.start as number,
+			end: node.end as number,
+			text: code.slice(node.start as number, node.end as number),
+			source: node.source.value as string,
+			hasOnlyNamedSpecifiers: Array.isArray(node.specifiers) && node.specifiers.length > 0 && node.specifiers.every((spec: any) => spec?.type === 'ImportSpecifier'),
+			namedBindings: Array.isArray(node.specifiers)
+				? node.specifiers
+						.filter((spec: any) => spec?.type === 'ImportSpecifier' && typeof spec.start === 'number' && typeof spec.end === 'number')
+						.map((spec: any) => ({
+							importedName: spec.imported?.type === 'Identifier' ? spec.imported.name : String(spec.imported?.value || ''),
+							text: code.slice(spec.start as number, spec.end as number),
+						}))
+				: [],
+		}));
 }
 
 export function hoistTopLevelStaticImports(code: string): string {