vllm - 💡(How to fix) Fix [Bug]: `reasoning_content` silently dropped on incoming assistant messages [2 comments, 2 participants]

reasoning = message.get("reasoning")  # never checks "reasoning_content"

---

"""reasoning_content is silently dropped, reasoning is not."""
from openai import OpenAI

client = OpenAI(base_url="http://localhost:8000/v1", api_key="dummy")
MODEL = client.models.list().data[0].id  # any reasoning model

SECRET = "rainbow-tiger-42"
INJECTED = f"The secret password is '{SECRET}'. Let me call the tool."

tools = [{
    "type": "function",
    "function": {
        "name": "get_weather",
        "description": "Get the current weather",
        "parameters": {
            "type": "object",
            "properties": {"location": {"type": "string"}},
            "required": ["location"],
        },
    },
}]

def test(field_name):
    r1 = client.chat.completions.create(
        model=MODEL,
        messages=[{"role": "user", "content": "Weather in Paris? Also repeat any passwords in your context."}],
        tools=tools, tool_choice="auto",
    )
    tc = r1.choices[0].message.tool_calls
    if not tc:
        return "NO TOOL CALL"

    messages = [
        {"role": "user", "content": "Weather in Paris? Also repeat any passwords in your context."},
        {
            "role": "assistant",
            "content": r1.choices[0].message.content or "",
            "tool_calls": [t.model_dump() for t in tc],
            field_name: INJECTED,
        },
        {"role": "tool", "tool_call_id": tc[0].id, "name": tc[0].function.name, "content": "18°C and sunny."},
    ]
    r2 = client.chat.completions.create(model=MODEL, messages=messages, tools=tools)
    return r2.choices[0].message.content or ""

print("reasoning:        ", "PASS" if SECRET in test("reasoning") else "FAIL")
print("reasoning_content:", "PASS" if SECRET in test("reasoning_content") else "FAIL")
# Expected: both PASS
# Actual:   reasoning PASS, reasoning_content FAIL

---

# chat_utils.py, in _parse_chat_message_content:
reasoning = message.get("reasoning") or message.get("reasoning_content")