Question: Is the missing opening <think> tag expected behavior or an issue in the OpenAI-compatible API?

[handsomelcx]

Hi,

First of all, thank you for maintaining this excellent fork. I really appreciate all the work you've put into it.

I have a question regarding the reasoning output format when using the OpenAI-compatible server.

I'm testing with Qwen3.6 using the latest JamePeng fork through the OpenAI API. During reasoning, the response looks something like this:

Thinking Process:
...

Instead of:

...

or returning the reasoning separately.

Because the opening tag is missing while the closing tag is still present, clients such as Cherry Studio cannot recognize the reasoning block and therefore cannot fold or collapse it.

I've confirmed that this behavior is the same when using both:

Cherry Studio (latest version)
Open WebUI (latest version)

So it doesn't appear to be a client-specific issue.

My question is:

Is this the expected behavior of the OpenAI-compatible server?
Is the opening intentionally removed by llama-cpp-python?
Or is this simply how Qwen3.6's chat template works?
If it's configurable, is there any option to preserve the original ... tags in the API response?

I'm mainly trying to understand where this behavior originates before investigating it further.

Thank you!