[Feature] support stop_token_ids

[lizexu123]

This PR supports stop_token_ids, which allows specifying individual token IDs that signal the model to terminate the current generation process.

Related environment variables

• FD_STOP_TOKEN_IDS_MAX_LEN : Maximum number of stop token, default is 8

Usage

online serving

• launch the serving
• request with stop_token_ids parameter， it can be '[List[int]]'

# create a chat request with "stop_token_ids" parameter
curl -X POST "http://0.0.0.0:13312/v1/chat/completions" \
-H "Content-Type: application/json" \
-d '{
    "model": "default",
    "messages": [
        {
            "role": "user",
            "content": "北京天安门在哪里?"
        }
    ],
    "temperature": 0.7,
    "stream": false,
    "seed": 1,
    "stop_token_ids":[104208]
}'

# the original output without `stop_token_ids` is: 
# {"id":"chatcmpl-33610f95-7d01-47a6-b040-39b18316f727","object":"chat.completion","created":1760692757,"model":"/root/paddlejob/workspace/env_run/output/models/paddle/Qwen/Qwen3-0.6B","choices":[{"index":0,"message":{"role":"assistant","content":"<think>\n好的，用户问的是“北京天安门在哪里？”。首先，我需要确认用户的需求是什么。可能他们想知道天安门的具体位置，或者想了解它的重要性。接下来，我得回忆一下北京天安门广场的地理位置。天安门广场位于北京市中心，周围环绕着著名的胡同，比如大栅栏、小街等。用户可能对城市规划和地标建筑感兴趣，也可能是想了解天安门的历史和功能。\n\n用户可能没有明确说明他们的需求，但作为回答者，我需要确保信息准确且易于理解。天安门广场是北京的标志性建筑之一，周围有丰富的历史和文化元素。此外，用户可能还想知道天安门与周围其他景点的关系，比如人民广场、故宫等，这有助于提供更全面的回答。\n\n需要注意的是，用户可能对“哪里”这个词语有歧义，可能需要进一步澄清。但根据问题本身，直接回答地理位置是合适的。同时，保持回答简洁明了，避免使用过于专业的术语，让用户容易理解。\n</think>\n\n北京天安门广场位于中国北京市中心，是中华人民共和国的象征性建筑之一。广场周围环绕着著名的胡同，如大栅栏、小街等，是北京的城市地标和历史文化中心。","multimodal_content":null,"reasoning_content":null,"tool_calls":null,"prompt_token_ids":null,"completion_token_ids":null,"prompt_tokens":null,"completion_tokens":null},"logprobs":null,"finish_reason":"stop"}],"usage":{"prompt_tokens":14,"total_tokens":276,"completion_tokens":262,"prompt_tokens_details":{"cached_tokens":0}}}

# the output with `stop_token_ids` is:
# {"id":"chatcmpl-51f772d0-e0d8-48da-9b5f-a3690849ffca","object":"chat.completion","created":1760692873,"model":"/root/paddlejob/workspace/env_run/output/models/paddle/Qwen/Qwen3-0.6B","choices":[{"index":0,"message":{"role":"assistant","content":"<think>\n好的，用户问的是“北京天安门在哪里？”。首先，我需要确认用户的需求是什么。可能他们想知道天安门的具体位置，或者想了解它的重要性。接下来，我得回忆一下北京天安门","multimodal_content":null,"reasoning_content":null,"tool_calls":null,"prompt_token_ids":null,"completion_token_ids":null,"prompt_tokens":null,"completion_tokens":null},"logprobs":null,"finish_reason":"stop"}],"usage":{"prompt_tokens":14,"total_tokens":64,"completion_tokens":50,"prompt_tokens_details":{"cached_tokens":0}}}```

offline demo

from fastdeploy.engine.sampling_params import SamplingParams
from fastdeploy.entrypoints.llm import LLM

model_name_or_path = "/root/paddlejob/workspace/env_run/output/models/paddle/Qwen/Qwen3-0.6B"

# 超参设置
sampling_params = SamplingParams(temperature=1, seed=1,stop_token_ids=[104208])
llm = LLM(model=model_name_or_path, tensor_parallel_size=1)
output = llm.chat(messages=[{"role": "user", "content": "北京天安门在哪里?"}], use_tqdm=True, sampling_params=sampling_params)

print(output)```

PR Summary

This PR addresses three main improvements:

1. Clarified the ambiguous usage of stop_seqs and stop_token_ids:Previously, stop_seqs was incorrectly passed to request.stop_token_ids Now corrected to pass it to request.stop_seqs instead.
2. Added support for stop_token_ids.
3. Enhanced stopping checks with min_tokens and max_tokens validation:If a stop_token_ids is encountered before reaching min_tokens, generation continues until min_tokens is reached
   If a stop_token_ids would trigger after max_tokens, generation stops at max_tokens instead.

[paddle-bot]

Thanks for your contribution!

[zoooo0820]

https://github.com/PaddlePaddle/FastDeploy/blob/develop/docs/features/early_stop.md 也分别在这个中英文文档中补充下用法吧

[zoooo0820]

这里stop到stop_seqs的修改，会改变对外暴露的接口名吗

[zoooo0820]

这里max_tokens的限制是否必要，目前应该已经有针对max_tokens的限制了？

[zoooo0820]

不足min_tokens的条件是不是所有情况都应该直接return

[zoooo0820]

需要看下max_tokens是否是必要参数