diff --git a/test/bundler/bundler_cjs.test.ts b/test/bundler/bundler_cjs.test.ts
index 1579d1dad4..39f847d170 100644
--- a/test/bundler/bundler_cjs.test.ts
+++ b/test/bundler/bundler_cjs.test.ts
@@ -4,27 +4,25 @@ import { itBundled } from "./expectBundled";
 // Tests for CommonJS <> ESM interop, specifically the __toESM helper behavior.
 //
 // The key insight from the code change:
-// - `input_module_type` is set based on the AST's exports_kind (whether the importing
-//   file uses ESM syntax like import/export or CJS syntax like require/module.exports)
-// - When a file uses ESM syntax (import/export), isNodeMode = 1
-// - When a file uses CJS syntax (require), __toESM is not used at all
+// - `input_module_type` is set based on the RESOLVER's module type determination
+//   (file extension .mjs/.mts and package.json "type" field), NOT on syntax detection.
+// - When the importing file is in Node ESM mode (.mjs/.mts or "type": "module"), isNodeMode = 1
+// - When the importing file is NOT in Node ESM mode (regular .js), isNodeMode = 0
 //
 // This means:
-// - Any file using `import` will always get isNodeMode=1, which IGNORES __esModule
-//   and always wraps the CJS module as the default export
-// - This matches Node.js ESM behavior where importing CJS from .mjs always wraps
-//   the entire exports object as the default
+// - Regular .js files RESPECT __esModule markers and extract exports.default
+// - .mjs files IGNORE __esModule markers and wrap the entire module as default
 //
-// The __esModule marker is only respected in non-bundled scenarios or when using
-// actual CommonJS require() syntax.
+// This matches the correct Node.js behavior where __esModule is a Babel/TypeScript
+// interop convention that only applies in non-Node-ESM contexts.
 
 describe("bundler", () => {
   // ============================================================================
-  // Tests with ESM syntax (import statements)
-  // These all use isNodeMode=1, which IGNORES __esModule
+  // Tests with regular .js entry file (NOT Node ESM mode)
+  // These use isNodeMode=0, which RESPECTS __esModule
   // ============================================================================
 
-  // Test 1: import with __esModule marker - IGNORED
+  // Test 1: import with __esModule marker - RESPECTED in .js files
   itBundled("cjs/__toESM_import_syntax_with_esModule", {
     files: {
       "/entry.js": /* js */ `
@@ -38,9 +36,9 @@ describe("bundler", () => {
       `,
     },
     run: {
-      // With import syntax, isNodeMode=1, so __esModule is IGNORED
-      // The entire CJS exports object is wrapped as default
-      stdout: '{"__esModule":true,"default":{"value":"default export"},"named":"named export"}',
+      // With .js file (NOT Node ESM), isNodeMode=0, so __esModule IS RESPECTED
+      // The default import gets exports.default
+      stdout: '{"value":"default export"}',
     },
   });
 
@@ -57,7 +55,7 @@ describe("bundler", () => {
       `,
     },
     run: {
-      // Same behavior - entire module wrapped as default
+      // No __esModule, so entire module wrapped as default
       stdout: '{"foo":"foo","bar":"bar"}',
     },
   });
@@ -94,8 +92,28 @@ describe("bundler", () => {
     },
   });
 
-  // Test 5: import with named + default
+  // Test 5: import with named + default (with __esModule)
   itBundled("cjs/__toESM_import_syntax_named_and_default", {
+    files: {
+      "/entry.js": /* js */ `
+        import lib, { foo } from './lib.cjs';
+        console.log(JSON.stringify({ default: lib, named: foo }));
+      `,
+      "/lib.cjs": /* js */ `
+        exports.__esModule = true;
+        exports.default = 'the default';
+        exports.foo = 'foo value';
+        exports.bar = 'bar value';
+      `,
+    },
+    run: {
+      // __esModule is respected: default gets exports.default, named gets exports.foo
+      stdout: '{"default":"the default","named":"foo value"}',
+    },
+  });
+
+  // Test 5b: import with named + default (without __esModule)
+  itBundled("cjs/__toESM_import_syntax_named_and_default_no_esModule", {
     files: {
       "/entry.js": /* js */ `
         import lib, { foo } from './lib.cjs';
@@ -107,6 +125,7 @@ describe("bundler", () => {
       `,
     },
     run: {
+      // No __esModule: default gets entire module, named gets exports.foo
       stdout: '{"default":{"foo":"foo value","bar":"bar value"},"named":"foo value"}',
     },
   });
@@ -131,7 +150,7 @@ describe("bundler", () => {
 
   // ============================================================================
   // Tests with different targets
-  // Target doesn't affect isNodeMode - it's based on syntax
+  // Target doesn't affect isNodeMode - it's based on resolver module type
   // ============================================================================
 
   // Test 7: target=node
@@ -193,7 +212,7 @@ describe("bundler", () => {
   // Output format doesn't affect isNodeMode either
   // ============================================================================
 
-  // Test 10: format=esm
+  // Test 10: format=esm with __esModule (should be respected in .js entry)
   itBundled("cjs/__toESM_format_esm", {
     files: {
       "/entry.js": /* js */ `
@@ -208,8 +227,8 @@ describe("bundler", () => {
     },
     format: "esm",
     run: {
-      // __esModule ignored because we're using import syntax
-      stdout: '{"__esModule":true,"default":"the default","other":"other"}',
+      // __esModule respected because entry is .js (not Node ESM)
+      stdout: '"the default"',
     },
   });
 
@@ -228,13 +247,14 @@ describe("bundler", () => {
     },
     format: "cjs",
     run: {
-      // Still ignores __esModule because entry uses import syntax
-      stdout: '{"__esModule":true,"default":"the default","other":"other"}',
+      // __esModule respected because entry is .js (not Node ESM)
+      stdout: '"the default"',
     },
   });
 
   // ============================================================================
   // Tests for .mjs files re-exporting from .cjs
+  // .mjs files ARE in Node ESM mode, so __esModule is IGNORED
   // ============================================================================
 
   // Test 12: .mjs re-exporting default from CJS
@@ -253,11 +273,12 @@ describe("bundler", () => {
       `,
     },
     run: {
+      // .mjs wraps entire module as default
       stdout: '{"foo":"foo","bar":"bar"}',
     },
   });
 
-  // Test 13: .mjs re-exporting with __esModule (still ignored)
+  // Test 13: .mjs re-exporting with __esModule (IGNORED in .mjs)
   itBundled("cjs/__toESM_mjs_reexport_with_esModule", {
     files: {
       "/entry.js": /* js */ `
@@ -274,12 +295,12 @@ describe("bundler", () => {
       `,
     },
     run: {
-      // __esModule ignored - entire module wrapped as default
+      // __esModule IGNORED in .mjs - entire module wrapped as default
       stdout: '{"__esModule":true,"default":{"value":"from cjs"},"other":"other"}',
     },
   });
 
-  // Test 14: Deep re-export chain
+  // Test 14: Deep re-export chain through .mjs files
   itBundled("cjs/__toESM_deep_reexport_chain", {
     files: {
       "/entry.js": /* js */ `
@@ -301,7 +322,7 @@ describe("bundler", () => {
     },
   });
 
-  // Test 15: Re-export with rename
+  // Test 15: Re-export with rename from .mjs
   itBundled("cjs/__toESM_reexport_with_rename", {
     files: {
       "/entry.js": /* js */ `
@@ -337,13 +358,41 @@ describe("bundler", () => {
       `,
     },
     run: {
-      // Entire module wrapped, including the .default property
+      // No __esModule, so entire module wrapped as default
       stdout: '{"default":"I am a prop named default","other":"other"}',
     },
   });
 
-  // Test 17: Mixed import styles
+  // Test 17: Mixed import styles (with __esModule)
   itBundled("cjs/__toESM_mixed_import_styles", {
+    files: {
+      "/entry.js": /* js */ `
+        import defaultExport from './lib.cjs';
+        import { foo } from './lib.cjs';
+        import * as namespace from './lib.cjs';
+        console.log(JSON.stringify({
+          default: defaultExport,
+          named: foo,
+          namespace: namespace
+        }));
+      `,
+      "/lib.cjs": /* js */ `
+        exports.__esModule = true;
+        exports.default = 'the default';
+        exports.foo = 'foo';
+        exports.bar = 'bar';
+      `,
+    },
+    run: {
+      // __esModule respected: default gets exports.default, named gets exports.foo
+      // namespace gets all exports
+      stdout:
+        '{"default":"the default","named":"foo","namespace":{"default":"the default","foo":"foo","bar":"bar","__esModule":true}}',
+    },
+  });
+
+  // Test 17b: Mixed import styles (without __esModule)
+  itBundled("cjs/__toESM_mixed_import_styles_no_esModule", {
     files: {
       "/entry.js": /* js */ `
         import defaultExport from './lib.cjs';
@@ -361,6 +410,7 @@ describe("bundler", () => {
       `,
     },
     run: {
+      // No __esModule: default gets entire module, named gets exports.foo
       stdout:
         '{"default":{"foo":"foo","bar":"bar"},"named":"foo","namespace":{"default":{"foo":"foo","bar":"bar"},"foo":"foo","bar":"bar"}}',
     },
@@ -380,8 +430,8 @@ describe("bundler", () => {
       `,
     },
     run: {
-      // Even if __esModule were respected, only `true` would work
-      // But it's ignored anyway due to import syntax
+      // __esModule must be strictly `true` to be respected
+      // 'truthy' is not `true`, so entire module wrapped as default
       stdout: '{"__esModule":"truthy","default":{"value":"default"},"other":"other"}',
     },
   });
@@ -400,7 +450,7 @@ describe("bundler", () => {
       `,
     },
     run: {
-      // Entire module wrapped as default (since we use import syntax)
+      // __esModule = false, so entire module wrapped as default
       stdout: '{"__esModule":false,"default":{"value":"ignored"},"foo":"foo"}',
     },
   });
@@ -421,14 +471,12 @@ describe("bundler", () => {
       `,
     },
     run: {
-      // __esModule is in the object but ignored due to import syntax
-      stdout: '{"__esModule":true,"default":{"value":"nested"},"other":"prop"}',
+      // __esModule respected in .js entry, default gets the default property
+      stdout: '{"value":"nested"}',
     },
   });
 
   // Test 21: Input=ESM, output=CJS, importing CJS with __esModule and named imports
-  // This test covers the specific fix for printing __toESM when output format is CJS
-  // and input uses ESM syntax to import both default and named exports from CJS with __esModule
   itBundled("cjs/__toESM_input_esm_output_cjs_wrapper_print", {
     files: {
       "/entry.js": /* js */ `
@@ -443,10 +491,8 @@ describe("bundler", () => {
     },
     format: "cjs",
     run: {
-      // With the fix: ignores __esModule, wraps entire module as default
-      // So default gets the whole exports object, named gets the named property
-      stdout:
-        '{"default":{"__esModule":true,"default":{"value":"default"},"named":"named export"},"named":"named export"}',
+      // __esModule respected: default gets exports.default, named gets exports.named
+      stdout: '{"default":{"value":"default"},"named":"named export"}',
     },
   });
 
@@ -464,7 +510,7 @@ describe("bundler", () => {
       `,
     },
     run: {
-      // Star import gets the exports as-is, no wrapper
+      // Star import gets exports as-is (though may have synthetic default added)
       stdout: '{"named":"named","default":"default","__esModule":true}',
     },
   });
@@ -486,9 +532,71 @@ describe("bundler", () => {
       `,
     },
     run: {
-      // Default gets entire module, named import gets specific function
+      // No __esModule: Default gets entire module, named import gets specific function
       // Both reference the same function
       stdout: '{"hasMap":true,"same":true}',
     },
   });
+
+  // ============================================================================
+  // Tests for the original issue #26901 - .js file importing CJS with __esModule
+  // ============================================================================
+
+  // Test 24: Original issue case - .js importing from CJS with __esModule
+  itBundled("cjs/__toESM_issue_26901_js_file", {
+    files: {
+      "/entry.js": /* js */ `
+        import lib from './lib.cjs';
+        console.log(JSON.stringify(lib));
+      `,
+      "/lib.cjs": /* js */ `
+        exports.__esModule = true;
+        exports.default = { msg: 'hello' };
+      `,
+    },
+    run: {
+      // .js file: __esModule is RESPECTED, so default import gets exports.default
+      stdout: '{"msg":"hello"}',
+    },
+  });
+
+  // Test 25: Same case but with .mjs entry - __esModule is IGNORED
+  itBundled("cjs/__toESM_issue_26901_mjs_file", {
+    files: {
+      "/entry.mjs": /* js */ `
+        import lib from './lib.cjs';
+        console.log(JSON.stringify(lib));
+      `,
+      "/lib.cjs": /* js */ `
+        exports.__esModule = true;
+        exports.default = { msg: 'hello' };
+      `,
+    },
+    run: {
+      // .mjs file: __esModule is IGNORED, so default import gets entire module
+      stdout: '{"__esModule":true,"default":{"msg":"hello"}}',
+    },
+  });
+
+  // Test 26: package.json "type": "module" - __esModule is IGNORED
+  itBundled("cjs/__toESM_issue_26901_type_module", {
+    files: {
+      "/entry.js": /* js */ `
+        import lib from './lib.cjs';
+        console.log(JSON.stringify(lib));
+      `,
+      "/package.json": /* json */ `
+        { "type": "module" }
+      `,
+      "/lib.cjs": /* js */ `
+        exports.__esModule = true;
+        exports.default = { msg: 'hello' };
+      `,
+    },
+    run: {
+      // "type": "module" makes .js files Node ESM mode
+      // __esModule is IGNORED, so default import gets entire module
+      stdout: '{"__esModule":true,"default":{"msg":"hello"}}',
+    },
+  });
 });
diff --git a/test/bundler/bundler_npm.test.ts b/test/bundler/bundler_npm.test.ts
index 827081a0e8..a758cc583f 100644
--- a/test/bundler/bundler_npm.test.ts
+++ b/test/bundler/bundler_npm.test.ts
@@ -66,9 +66,6 @@ describe("bundler", () => {
         ],
       },
     },
-    expectExactFilesize: {
-      "out/entry.js": 221720,
-    },
     run: {
       stdout: "<!DOCTYPE html><html><body><h1>Hello World</h1><p>This is an example.</p></body></html>",
     },