feat: make VAE optional for Qwen-Image, use bundled VAE by default

Qwen-Image models come with their own bundled AutoencoderKLQwenImage VAE
in the /vae subdirectory. This change:

- Makes the VAE field optional in QwenImageModelLoaderInvocation
- Uses the bundled VAE from the main model when no VAE is specified
- Allows overriding with a custom VAE if desired

This solves the issue where users couldn't find a Qwen-specific VAE to select,
since the VAE is bundled with the main model rather than being a separate download.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

invokeai/app/invocations/qwen_image_model_loader.py

@@ -47,22 +47,33 @@ class QwenImageModelLoaderInvocation(BaseInvocation):
         # ui_model_type=ModelType.VL
     )
 
-    vae_model: ModelIdentifierField = InputField(
+    vae_model: ModelIdentifierField | None = InputField(
         description="VAE model for Qwen-Image",
         title="VAE",
         ui_model_base=BaseModelType.QwenImage,
         ui_model_type=ModelType.VAE,
+        default=None,
     )
 
     def invoke(self, context: InvocationContext) -> QwenImageModelLoaderOutput:
-        # Validate that all models exist
-        for key in [self.model.key, self.qwen2_5_vl_model.key, self.vae_model.key]:
+        # Validate that required models exist
+        for key in [self.model.key, self.qwen2_5_vl_model.key]:
             if not context.models.exists(key):
                 raise ValueError(f"Unknown model: {key}")
 
+        # Validate optional VAE model if provided
+        if self.vae_model and not context.models.exists(self.vae_model.key):
+            raise ValueError(f"Unknown model: {self.vae_model.key}")
+
         # Create submodel references
         transformer = self.model.model_copy(update={"submodel_type": SubModelType.Transformer})
-        vae = self.vae_model.model_copy(update={"submodel_type": SubModelType.VAE})
+
+        # Use provided VAE or extract from main model
+        if self.vae_model:
+            vae = self.vae_model.model_copy(update={"submodel_type": SubModelType.VAE})
+        else:
+            # Use the VAE bundled with the Qwen-Image model
+            vae = self.model.model_copy(update={"submodel_type": SubModelType.VAE})
 
         # For Qwen-Image, we use Qwen2.5-VL as the text encoder
         tokenizer = self.qwen2_5_vl_model.model_copy(update={"submodel_type": SubModelType.Tokenizer})

invokeai/frontend/web/src/services/api/schema.ts

@@ -18344,7 +18344,7 @@ export type components = {
             qwen2_5_vl_model: components["schemas"]["ModelIdentifierField"];
             /**
              * VAE
-             * @description VAE model for Qwen-Image
+             * @description VAE model (uses Qwen-Image's bundled VAE if not specified)
              * @default null
              */
             vae_model?: components["schemas"]["ModelIdentifierField"] | null;