@@ -1404,7 +1404,7 @@ function loadESMFromCJS(mod, filename) {
 * @param {'commonjs'|undefined} format Intended format of the module.
 */
 function wrapSafe(filename, content, cjsModuleInstance, format) {
-assert(format !== 'module'); // ESM should be handled in loadESMFromCJS().
+assert(format !== 'module', 'ESM should be handled in loadESMFromCJS()');
 const hostDefinedOptionId = vm_dynamic_import_default_internal;
 const importModuleDynamically = vm_dynamic_import_default_internal;
 if (ed) {
@@ -1434,7 +1434,17 @@ function wrapSafe(filename, content, cjsModuleInstance, format) {
 };
 }
 
-const shouldDetectModule = (format !== 'commonjs' && getOptionValue('--experimental-detect-module'));
+let shouldDetectModule = false;
+if (format !== 'commonjs') {
+if (cjsModuleInstance?.[kIsMainSymbol]) {
+// For entry points, format detection is used unless explicitly disabled.
+shouldDetectModule = getOptionValue('--experimental-detect-module');
+} else {
+// For modules being loaded by `require()`, if require(esm) is disabled,
+// don't try to reparse to detect format and just throw for ESM syntax.
+shouldDetectModule = getOptionValue('--experimental-require-module');
+}
+}
 const result = compileFunctionForCJSLoader(content, filename, false /* is_sea_main */, shouldDetectModule);
 
 // Cache the source map for the module if present.
@@ -1471,8 +1481,6 @@ Module.._compile = function(content, filename, format) {
 }
 }
 
-// TODO(joyeecheung): when the module is the entry point, consider allowing TLA.
-// Only modules being require()'d really need to avoid TLA.
 if (format === 'module') {
 // Pass the source into the .mjs extension handler indirectly through the cache.
 this[kModuleSource] = content;

@@ -0,0 +1,19 @@
+// Flags: --no-experimental-require-module
+'use strict';
+
+// Tests that --experimental-require-module is not implied by --experimental-detect-module
+// and is checked independently.
+require('../common');
+const assert = require('assert');
+
+// Check that require() still throws SyntaxError for an ambiguous module that's detected to be ESM.
+// TODO(joyeecheung): now that --experimental-detect-module is unflagged, it makes more sense
+// to either throw ERR_REQUIRE_ESM for require() of detected ESM instead, or add a hint about the
+// use of require(esm) to the SyntaxError.
+
+assert.throws(
+() => require('../fixtures/es-modules/loose.js'),
+{
+name: 'SyntaxError',
+message: /Unexpected token 'export'/
+});

@@ -1,3 +1,5 @@
-// This file can be run or imported only if `--experimental-default-type=module` is set.
+// This file can be run or imported only if `--experimental-default-type=module` is set
+// or `--experimental-detect-module` is not disabled. If it's loaded by
+// require(), then `--experimental-require-module` must not be disabled.
 export default 'module';
 console.log('executed');