fix: return correct shape logits and add streaming test

integration-tests/models/__snapshots__/test_flash_qwen2_vl/test_flash_qwen2_vl_simple_streaming.json

@@ -0,0 +1,20 @@
+{
+  "choices": [
+    {
+      "delta": {
+        "content": "",
+        "role": "assistant",
+        "tool_calls": null
+      },
+      "finish_reason": "stop",
+      "index": 0,
+      "logprobs": null
+    }
+  ],
+  "created": 1730416361,
+  "id": "",
+  "model": "Qwen/Qwen2-VL-7B-Instruct",
+  "object": "chat.completion.chunk",
+  "system_fingerprint": "2.4.1-dev0-native",
+  "usage": null
+}

integration-tests/models/test_flash_qwen2_vl.py

@@ -40,3 +40,45 @@ async def test_flash_qwen2_vl_simple(flash_qwen2, response_snapshot):
     )
 
     assert response == response_snapshot
+
+
+@pytest.mark.private
+async def test_flash_qwen2_vl_simple_streaming(flash_qwen2, response_snapshot):
+    responses = await flash_qwen2.chat(
+        max_tokens=100,
+        seed=42,
+        messages=[
+            {
+                "role": "user",
+                "content": [
+                    {
+                        "type": "image_url",
+                        "image_url": {
+                            "url": "https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/transformers/rabbit.png"
+                        },
+                    },
+                    {"type": "text", "text": "Describe this image."},
+                ],
+            },
+        ],
+        stream=True,
+    )
+
+    count = 0
+    generated = ""
+    last_response = None
+    try:
+        async for response in responses:
+            count += 1
+            generated += response.choices[0].delta.content
+            last_response = response
+    except Exception as e:
+        # handle when the client library raises an exception when it cant parse "[DONE]" as JSON
+        pass
+
+    assert (
+        generated
+        == "The image depicts an anthropomorphic rabbit, wearing a futuristic spacesuit, in an extraterrestrial environment. The setting appears to be a red planet resembling Mars, with rugged terrain and rocky formations in the background. The moon is visible in the distant sky, adding to the lunar landscape."
+    )
+    assert count == 58
+    assert last_response == response_snapshot

server/text_generation_server/models/custom_modeling/qwen2_vl.py

@@ -518,5 +518,5 @@ def forward(
         hidden_states, _ = self.norm(hidden_states)
         if lm_head_indices is not None:
             hidden_states = hidden_states[lm_head_indices]
-        logits = self.lm_head(hidden_states)
-        return logits, None
+        logits, speculative_logits = self.lm_head(hidden_states)
+        return logits, speculative_logits

server/text_generation_server/models/vlm_causal_lm.py

@@ -364,7 +364,7 @@ def forward(
             lm_head_indices = batch.prefill_head_indices
 
         if self.model.config.model_type == "qwen2_vl":
-            if position_ids.dim() == 1:
+            if position_ids.dim() == 1 and batch.prefilling:
                 position_ids = self.model.get_position_ids(
                     input_ids, batch.image_grid_thw
                 )