[tests] [studio] Fix VLM detection for transformers v5

studio/backend/tests/test_transformers_version.py

@@ -34,6 +34,7 @@
     _tokenizer_class_cache,
     needs_transformers_5,
 )
+from utils.models import model_config
 
 
 # ---------------------------------------------------------------------------
@@ -188,3 +189,50 @@ def test_local_checkpoint_resolved_via_config(self, tmp_path: Path):
         # We test the full resolution chain here:
         resolved = _resolve_base_model(str(tmp_path))
         assert needs_transformers_5(resolved) is True
+
+
+class TestVisionModelDetection:
+    def test_is_vlm_config_accepts_transformers_objects(self):
+        config = _types.SimpleNamespace(
+            model_type = "qwen3_5",
+            architectures = ["Qwen3_5ForConditionalGeneration"],
+            vision_config = {},
+        )
+        assert model_config._is_vlm_config(config) is True
+
+    def test_is_vlm_config_accepts_raw_config_dicts(self):
+        config = {
+            "model_type": "gemma4",
+            "architectures": ["Gemma4ForConditionalGeneration"],
+            "vision_config": {},
+        }
+        assert model_config._is_vlm_config(config) is True
+
+    def test_is_vlm_config_rejects_audio_only_conditional_generation(self):
+        config = {
+            "model_type": "whisper",
+            "architectures": ["WhisperForConditionalGeneration"],
+        }
+        assert model_config._is_vlm_config(config) is False
+
+    def test_is_vision_model_falls_back_to_raw_metadata_for_t5_models(self):
+        with (
+            patch("utils.transformers_version.needs_transformers_5", return_value = True),
+            patch(
+                "utils.models.model_config.load_model_config",
+                side_effect = RuntimeError("direct load failed"),
+            ),
+            patch(
+                "utils.models.model_config._is_vision_model_subprocess",
+                return_value = None,
+            ),
+            patch(
+                "utils.models.model_config._load_model_config_metadata",
+                return_value = {
+                    "model_type": "qwen3_5",
+                    "architectures": ["Qwen3_5ForConditionalGeneration"],
+                    "vision_config": {},
+                },
+            ),
+        ):
+            assert model_config.is_vision_model("unsloth/Qwen3.5-4B") is True