think flag has no effect when using qwen3:8b

Passing the think parameter to chat() or AsyncClient.chat() doesn’t appear to change the output or behavior when using the qwen3:8b model.

Environment:

• ollama-python: 0.5.4
• ollama version: 0.11.8

My test code:

import asyncio
from ollama import AsyncClient, ChatResponse, chat


async def async_run_chat(think_flag: bool):
    client = AsyncClient(host="http://localhost:11434")  # change host if remote
    prompt = "Give me a concise explanation of why the sky appears blue."

    print(f"\n🔎 Starting chat with think={think_flag}\n")

    async for chunk in await client.chat(
        model="qwen3:8b",  # or any installed model
        messages=[{"role": "user", "content": prompt}],
        stream=True,
        think=think_flag,  # ✅ direct parameter, no options dict
    ):
        text_piece = chunk.get("message", {}).get("content", "")
        if text_piece:
            print(text_piece, end="", flush=True)

    print("\n✅ Done!\n")
    
def stream_run_chat(think_flag: bool):
    stream = chat(
        model='qwen3:8b',
        messages=[{'role': 'user', 'content': 'Why is the sky blue?'}],
        stream=True,
        think=think_flag
    )
    for chunk in stream:
        print(chunk['message']['content'], end='', flush=True)
        
def non_stream_run_chat(think_flag: bool):
    response: ChatResponse = chat(
        model='qwen3:8b', 
        messages=[
            {
                'role': 'user',
                'content': 'Why is the sky blue?',
            },
        ],
        think=think_flag
    )
    print(response['message']['content'])
    
    
if __name__ == "__main__":
    # asyncio.run(async_run_chat(think_flag=False))
    # stream_run_chat(think_flag=False)
    non_stream_run_chat(think_flag=False)

Start by tracing the think parameter through chat() and AsyncClient.chat() request construction, then compare the supplied streaming and non-streaming examples with qwen3:8b. Check whether the parameter reaches Ollama as intended and verify that think=True and think=False produce observably different behavior.