diff --git a/lib/detector.ts b/lib/detector.ts
index 35fbf11c..e6efaae4 100644
--- a/lib/detector.ts
+++ b/lib/detector.ts
@@ -1,49 +1,43 @@
-import * as babelTypes from '@babel/types';
-import * as babel from '@babel/parser';
-import generate from '@babel/generator';
+import * as acorn from 'acorn';
 import { log } from './log';
 
 import { ALIAS_AS_RELATIVE, ALIAS_AS_RESOLVABLE } from './common';
 
-function isLiteral(node: babelTypes.Node): node is babelTypes.Literal {
+// Minimal ESTree node types used by the detector
+interface AcornNode {
+  type: string;
+  start: number;
+  end: number;
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  [key: string]: any;
+}
+
+function isLiteral(node: AcornNode): boolean {
   if (node == null) {
     return false;
   }
 
-  if (!node.type.endsWith('Literal')) {
-    return false;
+  if (node.type === 'Literal') {
+    // Exclude null, regex
+    return node.value !== null && !(node.value instanceof RegExp);
   }
 
-  if (node.type === 'TemplateLiteral' && node.expressions.length !== 0) {
-    return false;
+  if (node.type === 'TemplateLiteral') {
+    return node.expressions.length === 0;
   }
 
-  return true;
+  return false;
 }
 
-function getLiteralValue(node: babelTypes.Literal) {
+function getLiteralValue(node: AcornNode) {
   if (node.type === 'TemplateLiteral') {
     return node.quasis[0].value.raw;
   }
 
-  if (node.type === 'NullLiteral') {
-    throw new Error('Unexpected null in require expression');
-  }
-
-  if (node.type === 'RegExpLiteral') {
-    throw new Error('Unexpected regexp in require expression');
-  }
-
   return node.value;
 }
 
-function reconstructSpecifiers(
-  specs: (
-    | babelTypes.ImportDefaultSpecifier
-    | babelTypes.ImportNamespaceSpecifier
-    | babelTypes.ImportSpecifier
-  )[],
-) {
+function reconstructSpecifiers(specs: AcornNode[]) {
   if (!specs || !specs.length) {
     return '';
   }
@@ -51,7 +45,7 @@ function reconstructSpecifiers(
   const defaults = [];
 
   for (const spec of specs) {
-    if (babelTypes.isImportDefaultSpecifier(spec)) {
+    if (spec.type === 'ImportDefaultSpecifier') {
       defaults.push(spec.local.name);
     }
   }
@@ -59,10 +53,8 @@ function reconstructSpecifiers(
   const nonDefaults = [];
 
   for (const spec of specs) {
-    if (babelTypes.isImportSpecifier(spec)) {
-      const importedName = babelTypes.isIdentifier(spec.imported)
-        ? spec.imported.name
-        : spec.imported.value;
+    if (spec.type === 'ImportSpecifier') {
+      const importedName = spec.imported.name;
 
       if (spec.local.name === importedName) {
         nonDefaults.push(spec.local.name);
@@ -79,8 +71,8 @@ function reconstructSpecifiers(
   return defaults.join(', ');
 }
 
-function reconstruct(node: babelTypes.Node) {
-  let v = generate(node, { comments: false }).code.replace(/\n/g, '');
+function reconstruct(node: AcornNode, source: string) {
+  let v = source.slice(node.start, node.end).replace(/\n/g, '');
   let v2;
 
   while (true) {
@@ -121,12 +113,12 @@ function valid2(v2?: Was['v2']) {
   );
 }
 
-function visitorRequireResolve(n: babelTypes.Node) {
-  if (!babelTypes.isCallExpression(n)) {
+function visitorRequireResolve(n: AcornNode) {
+  if (n.type !== 'CallExpression') {
     return null;
   }
 
-  if (!babelTypes.isMemberExpression(n.callee)) {
+  if (n.callee.type !== 'MemberExpression') {
     return null;
   }
 
@@ -150,12 +142,12 @@ function visitorRequireResolve(n: babelTypes.Node) {
   };
 }
 
-function visitorRequire(n: babelTypes.Node) {
-  if (!babelTypes.isCallExpression(n)) {
+function visitorRequire(n: AcornNode) {
+  if (n.type !== 'CallExpression') {
     return null;
   }
 
-  if (!babelTypes.isIdentifier(n.callee)) {
+  if (n.callee.type !== 'Identifier') {
     return null;
   }
 
@@ -173,20 +165,20 @@ function visitorRequire(n: babelTypes.Node) {
   };
 }
 
-function visitorImport(n: babelTypes.Node) {
-  if (!babelTypes.isImportDeclaration(n)) {
+function visitorImport(n: AcornNode) {
+  if (n.type !== 'ImportDeclaration') {
     return null;
   }
 
   return { v1: n.source.value, v3: reconstructSpecifiers(n.specifiers) };
 }
 
-function visitorPathJoin(n: babelTypes.Node) {
-  if (!babelTypes.isCallExpression(n)) {
+function visitorPathJoin(n: AcornNode) {
+  if (n.type !== 'CallExpression') {
     return null;
   }
 
-  if (!babelTypes.isMemberExpression(n.callee)) {
+  if (n.callee.type !== 'MemberExpression') {
     return null;
   }
 
@@ -218,10 +210,10 @@ function visitorPathJoin(n: babelTypes.Node) {
     return null;
   }
 
-  return { v1: getLiteralValue(n.arguments[1] as babelTypes.StringLiteral) };
+  return { v1: getLiteralValue(n.arguments[1]) };
 }
 
-export function visitorSuccessful(node: babelTypes.Node, test = false) {
+export function visitorSuccessful(node: AcornNode, test = false) {
   let was: Was | null = visitorRequireResolve(node);
 
   if (was) {
@@ -283,12 +275,12 @@ export function visitorSuccessful(node: babelTypes.Node, test = false) {
   return null;
 }
 
-function nonLiteralRequireResolve(n: babelTypes.Node) {
-  if (!babelTypes.isCallExpression(n)) {
+function nonLiteralRequireResolve(n: AcornNode, source: string) {
+  if (n.type !== 'CallExpression') {
     return null;
   }
 
-  if (!babelTypes.isMemberExpression(n.callee)) {
+  if (n.callee.type !== 'MemberExpression') {
     return null;
   }
 
@@ -309,7 +301,7 @@ function nonLiteralRequireResolve(n: babelTypes.Node) {
   const m = n.arguments[1];
 
   if (!m) {
-    return { v1: reconstruct(n.arguments[0]) };
+    return { v1: reconstruct(n.arguments[0], source) };
   }
 
   if (!isLiteral(n.arguments[1])) {
@@ -317,17 +309,17 @@ function nonLiteralRequireResolve(n: babelTypes.Node) {
   }
 
   return {
-    v1: reconstruct(n.arguments[0]),
+    v1: reconstruct(n.arguments[0], source),
     v2: getLiteralValue(n.arguments[1]),
   };
 }
 
-function nonLiteralRequire(n: babelTypes.Node) {
-  if (!babelTypes.isCallExpression(n)) {
+function nonLiteralRequire(n: AcornNode, source: string) {
+  if (n.type !== 'CallExpression') {
     return null;
   }
 
-  if (!babelTypes.isIdentifier(n.callee)) {
+  if (n.callee.type !== 'Identifier') {
     return null;
   }
 
@@ -342,7 +334,7 @@ function nonLiteralRequire(n: babelTypes.Node) {
   const m = n.arguments[1];
 
   if (!m) {
-    return { v1: reconstruct(n.arguments[0]) };
+    return { v1: reconstruct(n.arguments[0], source) };
   }
 
   if (!isLiteral(n.arguments[1])) {
@@ -350,13 +342,14 @@ function nonLiteralRequire(n: babelTypes.Node) {
   }
 
   return {
-    v1: reconstruct(n.arguments[0]),
+    v1: reconstruct(n.arguments[0], source),
     v2: getLiteralValue(n.arguments[1]),
   };
 }
 
-export function visitorNonLiteral(n: babelTypes.Node) {
-  const was = nonLiteralRequireResolve(n) || nonLiteralRequire(n);
+export function visitorNonLiteral(n: AcornNode, source: string) {
+  const was =
+    nonLiteralRequireResolve(n, source) || nonLiteralRequire(n, source);
 
   if (was) {
     if (!valid2(was.v2)) {
@@ -373,12 +366,12 @@ export function visitorNonLiteral(n: babelTypes.Node) {
   return null;
 }
 
-function isRequire(n: babelTypes.Node) {
-  if (!babelTypes.isCallExpression(n)) {
+function isRequire(n: AcornNode, source: string) {
+  if (n.type !== 'CallExpression') {
     return null;
   }
 
-  if (!babelTypes.isIdentifier(n.callee)) {
+  if (n.callee.type !== 'Identifier') {
     return null;
   }
 
@@ -392,15 +385,15 @@ function isRequire(n: babelTypes.Node) {
     return null;
   }
 
-  return { v1: reconstruct(n.arguments[0]) };
+  return { v1: reconstruct(n.arguments[0], source) };
 }
 
-function isRequireResolve(n: babelTypes.Node) {
-  if (!babelTypes.isCallExpression(n)) {
+function isRequireResolve(n: AcornNode, source: string) {
+  if (n.type !== 'CallExpression') {
     return null;
   }
 
-  if (!babelTypes.isMemberExpression(n.callee)) {
+  if (n.callee.type !== 'MemberExpression') {
     return null;
   }
 
@@ -420,11 +413,11 @@ function isRequireResolve(n: babelTypes.Node) {
     return null;
   }
 
-  return { v1: reconstruct(n.arguments[0]) };
+  return { v1: reconstruct(n.arguments[0], source) };
 }
 
-export function visitorMalformed(n: babelTypes.Node) {
-  const was = isRequireResolve(n) || isRequire(n);
+export function visitorMalformed(n: AcornNode, source: string) {
+  const was = isRequireResolve(n, source) || isRequire(n, source);
 
   if (was) {
     return { alias: was.v1 };
@@ -433,12 +426,12 @@ export function visitorMalformed(n: babelTypes.Node) {
   return null;
 }
 
-export function visitorUseSCWD(n: babelTypes.Node) {
-  if (!babelTypes.isCallExpression(n)) {
+export function visitorUseSCWD(n: AcornNode, source: string) {
+  if (n.type !== 'CallExpression') {
     return null;
   }
 
-  if (!babelTypes.isMemberExpression(n.callee)) {
+  if (n.callee.type !== 'MemberExpression') {
     return null;
   }
 
@@ -452,7 +445,9 @@ export function visitorUseSCWD(n: babelTypes.Node) {
     return null;
   }
 
-  const was = { v1: n.arguments.map(reconstruct).join(', ') };
+  const was = {
+    v1: n.arguments.map((a: AcornNode) => reconstruct(a, source)).join(', '),
+  };
 
   if (was) {
     return { alias: was.v1 };
@@ -461,25 +456,24 @@ export function visitorUseSCWD(n: babelTypes.Node) {
   return null;
 }
 
-type VisitorFunction = (node: babelTypes.Node, trying?: boolean) => boolean;
+type VisitorFunction = (node: AcornNode, trying?: boolean) => boolean;
 
-function traverse(ast: babelTypes.File, visitor: VisitorFunction) {
+function traverse(ast: AcornNode, visitor: VisitorFunction) {
   // modified esprima-walk to support
   // visitor return value and "trying" flag
-  // eslint-disable-next-line @typescript-eslint/no-explicit-any
-  const stack: Array<[any, boolean]> = [[ast, false]];
+  const stack: Array<[AcornNode, boolean]> = [[ast, false]];
 
   for (let i = 0; i < stack.length; i += 1) {
     const item = stack[i];
     const [node] = item;
 
     if (node) {
-      const trying = item[1] || babelTypes.isTryStatement(node);
+      const trying = item[1] || node.type === 'TryStatement';
 
       if (visitor(node, trying)) {
         for (const key in node) {
-          if (node[key as keyof babelTypes.File]) {
-            const child = node[key as keyof babelTypes.File];
+          if (node[key]) {
+            const child = node[key];
 
             if (child instanceof Array) {
               for (let j = 0; j < child.length; j += 1) {
@@ -496,25 +490,40 @@ function traverse(ast: babelTypes.File, visitor: VisitorFunction) {
 }
 
 export function parse(body: string) {
-  return babel.parse(body, {
-    allowImportExportEverywhere: true,
-    allowReturnOutsideFunction: true,
-  });
+  // Try module mode first (handles import/export), fall back to script mode
+  // for legacy code that uses strict-mode-incompatible syntax (e.g. `with`
+  // statements, octal escapes). This matches Babel's permissive behavior.
+  try {
+    return acorn.parse(body, {
+      ecmaVersion: 'latest',
+      sourceType: 'module',
+      allowReturnOutsideFunction: true,
+      allowImportExportEverywhere: true,
+      allowHashBang: true,
+    }) as unknown as AcornNode;
+  } catch (_) {
+    return acorn.parse(body, {
+      ecmaVersion: 'latest',
+      sourceType: 'script',
+      allowReturnOutsideFunction: true,
+      allowHashBang: true,
+    }) as unknown as AcornNode;
+  }
 }
 
 export function detect(body: string, visitor: VisitorFunction, file?: string) {
-  let json;
+  let ast: AcornNode | undefined;
 
   try {
-    json = parse(body);
+    ast = parse(body);
   } catch (error) {
     const fileInfo = file ? ` in ${file}` : '';
-    log.warn(`Babel parse has failed: ${(error as Error).message}${fileInfo}`);
+    log.warn(`Acorn parse has failed: ${(error as Error).message}${fileInfo}`);
   }
 
-  if (!json) {
+  if (!ast) {
     return;
   }
 
-  traverse(json, visitor);
+  traverse(ast, visitor);
 }
diff --git a/lib/walker.ts b/lib/walker.ts
index 4f68def1..92acd403 100644
--- a/lib/walker.ts
+++ b/lib/walker.ts
@@ -261,9 +261,11 @@ function stepDetect(
     body = body.toString();
   }
 
+  const source = body as string;
+
   try {
     detector.detect(
-      body,
+      source,
       (node, trying) => {
         const { toplevel } = marker;
         let d = detector.visitorSuccessful(node) as unknown as Derivative;
@@ -279,7 +281,7 @@ function stepDetect(
           return false;
         }
 
-        d = detector.visitorNonLiteral(node) as unknown as Derivative;
+        d = detector.visitorNonLiteral(node, source) as unknown as Derivative;
 
         if (d) {
           if (typeof d === 'object' && d.mustExclude) {
@@ -298,7 +300,7 @@ function stepDetect(
           return false;
         }
 
-        d = detector.visitorMalformed(node) as unknown as Derivative;
+        d = detector.visitorMalformed(node, source) as unknown as Derivative;
 
         if (d) {
           // there is no 'mustExclude'
@@ -308,7 +310,7 @@ function stepDetect(
           return false;
         }
 
-        d = detector.visitorUseSCWD(node) as unknown as Derivative;
+        d = detector.visitorUseSCWD(node, source) as unknown as Derivative;
 
         if (d) {
           // there is no 'mustExclude'
@@ -378,6 +380,37 @@ class Walker {
 
   private dictionary: ConfigDictionary;
 
+  // Module resolution cache: avoids redundant follow() calls for the same
+  // specifier resolved from the same directory.
+  private resolveCache = new Map<
+    string,
+    {
+      newFile: string;
+      newPackages: { packageJson: string; marker?: Marker }[];
+      newPackageForNewRecords?: { packageJson: string; marker?: Marker };
+    }
+  >();
+
+  // Performance timing accumulators (milliseconds)
+  private timings = {
+    read: 0,
+    strip: 0,
+    detect: 0,
+    patch: 0,
+    derivatives: 0,
+    esmTransform: 0,
+    stat: 0,
+    total: 0,
+  };
+
+  private fileCounts = {
+    jsParsed: 0,
+    json: 0,
+    nativeAddon: 0,
+    other: 0,
+    total: 0,
+  };
+
   constructor() {
     this.tasks = [];
     this.records = {};
@@ -541,9 +574,11 @@ class Walker {
       if (scripts) {
         scripts = expandFiles(scripts, base);
 
-        for (const script of scripts) {
-          const stat = await fs.stat(script);
+        const scriptStats = await Promise.all(
+          scripts.map((s) => fs.stat(s).then((stat) => ({ path: s, stat }))),
+        );
 
+        for (const { path: script, stat } of scriptStats) {
           if (stat.isFile()) {
             if (!isDotJS(script) && !isDotJSON(script) && !isDotNODE(script)) {
               log.warn("Non-javascript file is specified in 'scripts'.", [
@@ -567,9 +602,12 @@ class Walker {
       if (assets) {
         assets = expandFiles(assets, base);
 
-        for (const asset of assets) {
+        const assetStats = await Promise.all(
+          assets.map((a) => fs.stat(a).then((stat) => ({ path: a, stat }))),
+        );
+
+        for (const { path: asset, stat } of assetStats) {
           log.debug(' Adding asset : .... ', asset);
-          const stat = await fs.stat(asset);
 
           if (stat.isFile()) {
             await this.appendBlobOrContent({
@@ -587,10 +625,14 @@ class Walker {
       if (files) {
         files = expandFiles(files, base);
 
-        for (let file of files) {
-          file = normalizePath(file);
-          const stat = await fs.stat(file);
+        const normalizedFiles = files.map((f) => normalizePath(f));
+        const fileStats = await Promise.all(
+          normalizedFiles.map((f) =>
+            fs.stat(f).then((stat) => ({ path: f, stat })),
+          ),
+        );
 
+        for (const { path: file, stat } of fileStats) {
           if (stat.isFile()) {
             // 1) remove sources of top-level(!) package 'files' i.e. ship as BLOB
             // 2) non-source (non-js) files of top-level package are shipped as CONTENT
@@ -812,87 +854,130 @@ class Walker {
     marker: Marker,
     derivative: Derivative,
   ) {
-    const newPackages: { packageJson: string; marker?: Marker }[] = [];
+    const basedir = path.dirname(record.file);
+    const cacheKey = `${derivative.alias}\0${basedir}`;
+    const cached = this.resolveCache.get(cacheKey);
+
+    let newFile: string;
+    let newPackages: { packageJson: string; marker?: Marker }[];
+    let newPackageForNewRecords:
+      | { packageJson: string; marker?: Marker }
+      | undefined;
+
+    if (cached) {
+      // Cache hit — reuse prior resolution. Deep-clone marker objects to
+      // prevent shared mutation (stepActivate modifies marker.config).
+      // The appendBlobOrContent calls below are no-ops for already-seen
+      // files (deduped by appendRecord).
+      newFile = cached.newFile;
+      newPackages = cached.newPackages.map((p) => ({
+        packageJson: p.packageJson,
+        marker: p.marker
+          ? {
+              config: p.marker.config
+                ? JSON.parse(JSON.stringify(p.marker.config))
+                : undefined,
+              configPath: p.marker.configPath,
+              base: p.marker.base,
+            }
+          : undefined,
+      }));
+      newPackageForNewRecords = cached.newPackageForNewRecords
+        ? newPackages.find(
+            (p) =>
+              p.packageJson === cached.newPackageForNewRecords!.packageJson,
+          )
+        : undefined;
+    } else {
+      // Cache miss — perform full resolution
+      newPackages = [];
 
-    const catchReadFile = (file: string) => {
-      assert(isPackageJson(file), `walker: ${file} must be package.json`);
-      newPackages.push({ packageJson: file });
-    };
+      const catchReadFile = (file: string) => {
+        assert(isPackageJson(file), `walker: ${file} must be package.json`);
+        newPackages.push({ packageJson: file });
+      };
 
-    const catchPackageFilter = (config: PackageJson, base: string) => {
-      const newPackage = newPackages[newPackages.length - 1];
-      newPackage.marker = {
-        config,
-        configPath: newPackage.packageJson,
-        base,
+      const catchPackageFilter = (config: PackageJson, base: string) => {
+        const newPackage = newPackages[newPackages.length - 1];
+        newPackage.marker = {
+          config,
+          configPath: newPackage.packageJson,
+          base,
+        };
       };
-    };
 
-    let newFile = '';
-    let failure: Error | undefined;
+      newFile = '';
+      let failure: Error | undefined;
 
-    const basedir = path.dirname(record.file);
-    try {
-      newFile = await follow(derivative.alias, {
-        basedir,
-        // default is extensions: ['.js'], but
-        // it is not enough because 'typos.json'
-        // is not taken in require('./typos')
-        // in 'normalize-package-data/lib/fixer.js'
-        // Also include .mjs to support ESM files that get transformed to .js
-        extensions: MODULE_RESOLVE_EXTENSIONS,
-        catchReadFile,
-        catchPackageFilter,
-      });
-    } catch (error) {
-      failure = error as Error;
-    }
+      try {
+        newFile = await follow(derivative.alias, {
+          basedir,
+          // default is extensions: ['.js'], but
+          // it is not enough because 'typos.json'
+          // is not taken in require('./typos')
+          // in 'normalize-package-data/lib/fixer.js'
+          // Also include .mjs to support ESM files that get transformed to .js
+          extensions: MODULE_RESOLVE_EXTENSIONS,
+          catchReadFile,
+          catchPackageFilter,
+        });
+      } catch (error) {
+        failure = error as Error;
+      }
 
-    if (failure) {
-      const { toplevel } = marker;
-      const mainNotFound =
-        newPackages.length > 0 && !newPackages[0].marker?.config?.main;
-      const debug =
-        !toplevel ||
-        derivative.mayExclude ||
-        (mainNotFound && derivative.fromDependencies);
-      const level = debug ? 'debug' : 'warn';
+      if (failure) {
+        const { toplevel } = marker;
+        const mainNotFound =
+          newPackages.length > 0 && !newPackages[0].marker?.config?.main;
+        const debug =
+          !toplevel ||
+          derivative.mayExclude ||
+          (mainNotFound && derivative.fromDependencies);
+        const level = debug ? 'debug' : 'warn';
+
+        if (mainNotFound) {
+          const message = "Entry 'main' not found in %1";
+          log[level](message, [
+            `%1: ${newPackages[0].packageJson}`,
+            `%2: ${record.file}`,
+          ]);
+        } else {
+          log[level](`${pc.yellow(failure.message)}  in ${record.file}`);
+        }
 
-      if (mainNotFound) {
-        const message = "Entry 'main' not found in %1";
-        log[level](message, [
-          `%1: ${newPackages[0].packageJson}`,
-          `%2: ${record.file}`,
-        ]);
-      } else {
-        log[level](`${pc.yellow(failure.message)}  in ${record.file}`);
+        return;
       }
 
-      return;
-    }
+      newPackageForNewRecords = undefined;
 
-    let newPackageForNewRecords;
+      for (const newPackage of newPackages) {
+        let newFile2;
 
-    for (const newPackage of newPackages) {
-      let newFile2;
+        try {
+          newFile2 = await follow(derivative.alias, {
+            basedir,
+            extensions: MODULE_RESOLVE_EXTENSIONS,
+            ignoreFile: newPackage.packageJson,
+          });
+          if (strictVerify) {
+            assert(newFile2 === normalizePath(newFile2));
+          }
+        } catch (_) {
+          // not setting is enough
+        }
 
-      try {
-        newFile2 = await follow(derivative.alias, {
-          basedir: path.dirname(record.file),
-          extensions: MODULE_RESOLVE_EXTENSIONS,
-          ignoreFile: newPackage.packageJson,
-        });
-        if (strictVerify) {
-          assert(newFile2 === normalizePath(newFile2));
+        if (newFile2 !== newFile) {
+          newPackageForNewRecords = newPackage;
+          break;
         }
-      } catch (_) {
-        // not setting is enough
       }
 
-      if (newFile2 !== newFile) {
-        newPackageForNewRecords = newPackage;
-        break;
-      }
+      // Store in cache for future lookups from the same directory
+      this.resolveCache.set(cacheKey, {
+        newFile,
+        newPackages,
+        newPackageForNewRecords,
+      });
     }
 
     // Add all discovered package.json files, not just the one determined by the double-resolution logic
@@ -975,6 +1060,17 @@ class Walker {
     if (record[store] !== undefined) return;
     record[store] = false; // default is discard
 
+    this.fileCounts.total += 1;
+    if (isDotJSON(record.file)) {
+      this.fileCounts.json += 1;
+    } else if (isDotNODE(record.file)) {
+      this.fileCounts.nativeAddon += 1;
+    } else if (isDotJS(record.file) || record.file.endsWith('.mjs')) {
+      this.fileCounts.jsParsed += 1;
+    } else {
+      this.fileCounts.other += 1;
+    }
+
     this.appendStat({
       file: record.file,
       store: STORE_STAT,
@@ -1012,11 +1108,18 @@ class Walker {
       this.hasPatch(record)
     ) {
       if (!record.body) {
+        let t0 = performance.now();
         await stepRead(record);
+        this.timings.read += performance.now() - t0;
+
+        t0 = performance.now();
         this.stepPatch(record);
+        this.timings.patch += performance.now() - t0;
 
         if (store === STORE_BLOB || needsSeaRead) {
+          t0 = performance.now();
           stepStrip(record);
+          this.timings.strip += performance.now() - t0;
         }
       }
 
@@ -1108,6 +1211,7 @@ class Walker {
         (isDotJS(record.file) || record.file.endsWith('.mjs'))
       ) {
         if (isESMFile(record.file)) {
+          const t0 = performance.now();
           try {
             const result = transformESMtoCJS(
               record.body.toString('utf8'),
@@ -1127,13 +1231,19 @@ class Walker {
               `Failed to transform ESM module to CJS for file "${record.file}": ${message}`,
             );
           }
+          this.timings.esmTransform += performance.now() - t0;
         }
       }
 
       if (store === STORE_BLOB || needsSeaRead) {
         const derivatives2: Derivative[] = [];
+        let t0 = performance.now();
         stepDetect(record, marker, derivatives2);
+        this.timings.detect += performance.now() - t0;
+
+        t0 = performance.now();
         await this.stepDerivatives(record, marker, derivatives2);
+        this.timings.derivatives += performance.now() - t0;
 
         // After dependencies are resolved, rewrite .mjs require paths to .js
         // since the packer renames .mjs files to .js in the snapshot.
@@ -1185,6 +1295,7 @@ class Walker {
       });
     }
 
+    const t0 = performance.now();
     try {
       const valueStat = await fs.stat(record.file);
 
@@ -1202,6 +1313,7 @@ class Walker {
       log.error(`Cannot stat, ${exception.code}`, record.file);
       throw wasReported(exception.message);
     }
+    this.timings.stat += performance.now() - t0;
 
     if (path.dirname(record.file) !== record.file) {
       // root directory
@@ -1298,12 +1410,30 @@ class Walker {
 
     const { tasks } = this;
 
+    const walkerStart = performance.now();
+
     for (let i = 0; i < tasks.length; i += 1) {
       // NO MULTIPLE WORKERS! THIS WILL LEAD TO NON-DETERMINISTIC
       // ORDER. one-by-one fifo is the only way to iterate tasks
       await this.step(tasks[i]);
     }
 
+    this.timings.total = performance.now() - walkerStart;
+
+    const t = this.timings;
+    const c = this.fileCounts;
+    log.debug('Walker performance summary:');
+    log.debug(
+      `  Files: ${c.total} total (${c.jsParsed} JS, ${c.json} JSON, ${c.nativeAddon} native, ${c.other} other)`,
+    );
+    log.debug(
+      `  Timings: read=${t.read.toFixed(0)}ms detect=${t.detect.toFixed(0)}ms derivatives=${t.derivatives.toFixed(0)}ms`,
+    );
+    log.debug(
+      `  esmTransform=${t.esmTransform.toFixed(0)}ms patch=${t.patch.toFixed(0)}ms strip=${t.strip.toFixed(0)}ms stat=${t.stat.toFixed(0)}ms`,
+    );
+    log.debug(`  Total walker time: ${t.total.toFixed(0)}ms`);
+
     return {
       symLinks: this.symLinks,
       records: this.records,
diff --git a/package.json b/package.json
index 8ea997ac..c12685ca 100644
--- a/package.json
+++ b/package.json
@@ -28,6 +28,7 @@
     "@babel/types": "^7.23.0",
     "@roberts_lando/vfs": "^0.3.2",
     "@yao-pkg/pkg-fetch": "3.5.33",
+    "acorn": "^8.16.0",
     "esbuild": "^0.27.3",
     "into-stream": "^9.1.0",
     "minimist": "^1.2.6",
diff --git a/yarn.lock b/yarn.lock
index 77e8a894..1eca3386 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -874,6 +874,11 @@ acorn@^8.15.0:
   resolved "https://registry.npmjs.org/acorn/-/acorn-8.15.0.tgz"
   integrity sha512-NZyJarBfL7nWwIq+FDL6Zp/yHEhePMNnnJ0y3qfieCrmNvYct8uvtiV41UvlSe6apAfk0fY1FbWx+NwfmpvtTg==
 
+acorn@^8.16.0:
+  version "8.16.0"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-8.16.0.tgz#4ce79c89be40afe7afe8f3adb902a1f1ce9ac08a"
+  integrity sha512-UVJyE9MttOsBQIDKw1skb9nAwQuR5wuGD3+82K6JgJlm/Y+KI92oNsMNGZCYdDsVtRHSak0pcV5Dno5+4jh9sw==
+
 agent-base@6:
   version "6.0.2"
   resolved "https://registry.npmjs.org/agent-base/-/agent-base-6.0.2.tgz"