Fix: update broken agent OpenAI-Compatible completion due to v0.20.0 changes (#9241)

### What problem does this PR solve?

Update broken agent OpenAI-Compatible completion due to v0.20.0. #9199 

Usage example:

**Referring the input is important, otherwise, will result in empty
output.**

<img width="1273" height="711" alt="Image"
src="https://github.com/user-attachments/assets/30740be8-f4d6-400d-9fda-d2616f89063f"
/>

<img width="622" height="247" alt="Image"
src="https://github.com/user-attachments/assets/0a2ca57a-9600-4cec-9362-0cafd0ab3aee"
/>

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/utils/api_utils.py

@@ -402,8 +402,22 @@ def get_data_openai(
     finish_reason=None,
     object="chat.completion",
     param=None,
+    stream=False
 ):
     total_tokens = prompt_tokens + completion_tokens
+
+    if stream:
+        return {
+            "id": f"{id}",
+            "object": "chat.completion.chunk",
+            "model": model,
+            "choices": [{
+                "delta": {"content": content},
+                "finish_reason": finish_reason,
+                "index": 0,
+            }],
+        }
+
     return {
         "id": f"{id}",
         "object": object,
@@ -414,9 +428,21 @@ def get_data_openai(
             "prompt_tokens": prompt_tokens,
             "completion_tokens": completion_tokens,
             "total_tokens": total_tokens,
-            "completion_tokens_details": {"reasoning_tokens": 0, "accepted_prediction_tokens": 0, "rejected_prediction_tokens": 0},
+            "completion_tokens_details": {
+                "reasoning_tokens": 0,
+                "accepted_prediction_tokens": 0,
+                "rejected_prediction_tokens": 0,
+            },
         },
-        "choices": [{"message": {"role": "assistant", "content": content}, "logprobs": None, "finish_reason": finish_reason, "index": 0}],
+        "choices": [{
+            "message": {
+                "role": "assistant",
+                "content": content
+            },
+            "logprobs": None,
+            "finish_reason": finish_reason,
+            "index": 0,
+        }],
     }