diff --git a/README.md b/README.md
index d4d2b25..3449d42 100644
--- a/README.md
+++ b/README.md
@@ -1686,7 +1686,7 @@ import (
 )
 
 func main() {
-    // enable module import
+    // install the default file-based module loader
     rt := quickjs.NewRuntime(quickjs.WithModuleImport(true))
     defer rt.Close()
 
diff --git a/README_zh-cn.md b/README_zh-cn.md
index 296c332..8ae991e 100644
--- a/README_zh-cn.md
+++ b/README_zh-cn.md
@@ -1681,7 +1681,7 @@ import (
 )
 
 func main() {
-    // 启用模块导入
+    // 安装默认的基于文件系统的模块 loader
     rt := quickjs.NewRuntime(quickjs.WithModuleImport(true))
     defer rt.Close()
 
diff --git a/runtime.go b/runtime.go
index 67488f8..215b980 100644
--- a/runtime.go
+++ b/runtime.go
@@ -476,12 +476,17 @@ func WithCanBlock(canBlock bool) Option {
 	}
 }
 
+// WithModuleImport installs or clears the default quickjs-libc file/module loader.
+// When enabled, import/export resolution can load modules via quickjs-ng's default loader.
+// When disabled, module resolution fails closed unless another loader is installed.
 func WithModuleImport(moduleImport bool) Option {
 	return func(o *Options) {
 		o.moduleImport = moduleImport
 	}
 }
 
+// WithStripInfo is retained for backward compatibility only.
+// Deprecated: quickjs-ng does not expose a runtime-level strip-info API, so this option is a no-op.
 func WithStripInfo(strip int) Option {
 	return func(o *Options) {
 		o.strip = strip
@@ -512,7 +517,7 @@ func NewRuntime(opts ...Option) *Runtime {
 		maxStackSize:         0,
 		canBlock:             true,
 		moduleImport:         false,
-		strip:                1,
+		strip:                0,
 		ownerGoroutineCheck:  true,
 		strictThreadAffinity: false,
 	}
@@ -894,7 +899,8 @@ func (r *Runtime) SetExecuteTimeout(timeout uint64) {
 	r.interruptHandlerState.Store(nil)
 }
 
-// SetStripInfo sets the strip info for the runtime.
+// SetStripInfo is retained for backward compatibility only.
+// Deprecated: quickjs-ng does not expose a runtime-level strip-info API, so this method is a no-op.
 func (r *Runtime) SetStripInfo(strip int) {
 	if r == nil {
 		return
@@ -911,7 +917,8 @@ func (r *Runtime) SetStripInfo(strip int) {
 	_ = strip
 }
 
-// SetModuleImport sets whether the runtime supports module import.
+// SetModuleImport installs or clears the default quickjs-libc file/module loader.
+// When disabled, import resolution fails closed unless another loader is installed.
 func (r *Runtime) SetModuleImport(moduleImport bool) {
 	if r == nil {
 		return
@@ -919,12 +926,16 @@ func (r *Runtime) SetModuleImport(moduleImport bool) {
 	if !r.ensureOwnerAccess() {
 		return
 	}
-	r.mu.RLock()
-	defer r.mu.RUnlock()
+	r.mu.Lock()
+	defer r.mu.Unlock()
 	if r.closed.Load() || r.ref == nil {
 		return
 	}
-	C.JS_SetModuleLoaderFunc2(r.ref, (*C.JSModuleNormalizeFunc)(unsafe.Pointer(nil)), (*C.JSModuleLoaderFunc2)(C.js_module_loader), (*C.JSModuleCheckSupportedImportAttributes)(C.js_module_check_attributes), unsafe.Pointer(nil))
+	if moduleImport {
+		C.JS_SetModuleLoaderFunc2(r.ref, (*C.JSModuleNormalizeFunc)(unsafe.Pointer(nil)), (*C.JSModuleLoaderFunc2)(C.js_module_loader), (*C.JSModuleCheckSupportedImportAttributes)(C.js_module_check_attributes), unsafe.Pointer(nil))
+		return
+	}
+	C.JS_SetModuleLoaderFunc2(r.ref, (*C.JSModuleNormalizeFunc)(unsafe.Pointer(nil)), nil, nil, unsafe.Pointer(nil))
 }
 
 // SetInterruptHandler sets a user interrupt handler using simplified approach.
diff --git a/runtime_test.go b/runtime_test.go
index 29027e3..f91b255 100644
--- a/runtime_test.go
+++ b/runtime_test.go
@@ -908,6 +908,76 @@ func TestRuntimeAdvancedOptions(t *testing.T) {
 	require.Equal(t, "GC test", result4.ToString())
 }
 
+func TestRuntimeWithModuleImportOptionInstallsDefaultLoader(t *testing.T) {
+	rt := NewRuntime(WithModuleImport(true))
+	defer rt.Close()
+
+	ctx := rt.NewContext()
+	require.NotNil(t, ctx)
+	defer ctx.Close()
+
+	result := ctx.Eval(`
+		(async function() {
+			const mod = await import("./test/fib_module.js");
+			return mod.fib(6);
+		})()
+	`, EvalAwait(true))
+	defer result.Free()
+
+	require.False(t, result.IsException())
+	require.EqualValues(t, 8, result.ToInt32())
+}
+
+func TestRuntimeSetModuleImportToggle(t *testing.T) {
+	evalFibImport := func(ctx *Context) *Value {
+		return ctx.Eval(`
+			(async function() {
+				const mod = await import("./test/fib_module.js");
+				return mod.fib(6);
+			})()
+		`, EvalAwait(true))
+	}
+
+	requireImportFailure := func(ctx *Context) {
+		result := evalFibImport(ctx)
+		require.NotNil(t, result)
+		defer result.Free()
+		require.True(t, result.IsException())
+
+		err := ctx.Exception()
+		require.Error(t, err)
+		require.Contains(t, strings.ToLower(err.Error()), "could not load module")
+	}
+
+	requireImportSuccess := func(ctx *Context) {
+		result := evalFibImport(ctx)
+		require.NotNil(t, result)
+		defer result.Free()
+		require.False(t, result.IsException())
+		require.EqualValues(t, 8, result.ToInt32())
+	}
+
+	rt := NewRuntime()
+	defer rt.Close()
+
+	ctx := rt.NewContext()
+	require.NotNil(t, ctx)
+	requireImportFailure(ctx)
+	ctx.Close()
+
+	rt.SetModuleImport(true)
+	ctx = rt.NewContext()
+	require.NotNil(t, ctx)
+	requireImportSuccess(ctx)
+	ctx.Close()
+
+	rt.SetModuleImport(false)
+	ctx = rt.NewContext()
+	require.NotNil(t, ctx)
+	defer ctx.Close()
+	requireImportFailure(ctx)
+}
+
 func TestRuntimeTimeoutOpaqueLifecycle(t *testing.T) {
 	base := timeoutOpaqueCount()