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Was it a bad idea to stream the text generation process using Context.report_progress()? #2501

@lottopotato

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@lottopotato

Question

I built a chatbot server using VLLM's AsyncLLMEngine and an MCP Streamable HTTP server via its Python SDK.

To stream the token generation process from the AsyncLLMEngine generator to the MCP client, I used context.report_progress as shown below.

...
foundation_model = AsyncLLMEngine.from_engine_args(
    AsyncEngineArgs(
        ...
    )
)


...

@server.tool()
async def chat(q:str, ctx: Context):

    messages = get_messages(q)
    generator = foundation_model.generate(messages, ...)
    
    async for request_output in generator:
        current_text = request_output.outputs[0].text
        next_text = current_text[len(answer):]
        if ctx is not None and isinstance(ctx, Context):
            await ctx.report_progress(i, None, next_text)
        answer = current_text
        i += 1
    

Is this usage appropriate for streaming the token generation process?

Is there another way?

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