diff --git a/packages/emitter/lib/decorators.tsp b/packages/emitter/lib/decorators.tsp
index 8354b5a..6b711c4 100644
--- a/packages/emitter/lib/decorators.tsp
+++ b/packages/emitter/lib/decorators.tsp
@@ -1,7 +1,5 @@
 import "../dist/tsp-index.js";
 
-using TypeSpec.Reflection;
-
 /**
  * Specifies the maximum number of graphemes (user-perceived characters) allowed.
  * Used alongside maxLength for proper Unicode text handling.
diff --git a/packages/emitter/src/decorators.ts b/packages/emitter/src/decorators.ts
index 41aa54a..8d15668 100644
--- a/packages/emitter/src/decorators.ts
+++ b/packages/emitter/src/decorators.ts
@@ -310,6 +310,7 @@ export function $external(context: DecoratorContext, target: Type) {
     });
     return;
   }
+
   context.program.stateSet(externalKey).add(target);
 }
 
diff --git a/packages/emitter/src/emitter.ts b/packages/emitter/src/emitter.ts
index 2f72574..8b74710 100644
--- a/packages/emitter/src/emitter.ts
+++ b/packages/emitter/src/emitter.ts
@@ -124,6 +124,17 @@ export class TypelexEmitter {
 
     // Skip external namespaces - they don't emit JSON files
     if (isExternal(this.program, ns)) {
+      // Validate that all models in external namespaces are empty (stub-only)
+      for (const [_, model] of ns.models) {
+        if (model.properties && model.properties.size > 0) {
+          this.program.reportDiagnostic({
+            code: "external-model-not-empty",
+            severity: "error",
+            message: `Models in @external namespaces must be empty stubs. Model '${model.name}' in namespace '${fullName}' has properties.`,
+            target: model,
+          });
+        }
+      }
       return;
     }
 
diff --git a/packages/emitter/test/spec/external/input/test/external.tsp b/packages/emitter/test/spec/external/input/test/external.tsp
index 9a7115a..22d73b7 100644
--- a/packages/emitter/test/spec/external/input/test/external.tsp
+++ b/packages/emitter/test/spec/external/input/test/external.tsp
@@ -2,12 +2,7 @@ import "@typelex/emitter";
 
 @external
 namespace test.external {
-  model Main {
-    shouldNotEmit: string;
-  }
+  model Main { }
 
-  model AlsoNotEmitted {
-    @required
-    value: boolean;
-  }
+  model AlsoNotEmitted { }
 }