[Feature] support auto chat template (#4949)

python/sglang/srt/conversation.py

@@ -17,7 +17,7 @@
 # https://github.com/lm-sys/FastChat/blob/main/fastchat/conversation.py
 import dataclasses
 from enum import IntEnum, auto
-from typing import Dict, List, Optional, Tuple, Union
+from typing import Callable, Dict, List, Optional, Tuple, Union
 
 from sglang.srt.openai_api.protocol import ChatCompletionRequest
 
@@ -407,6 +407,7 @@ class Conversation:
 
 # A global registry for all conversation templates
 chat_templates: Dict[str, Conversation] = {}
+matching_function_registry: List[Callable] = []
 
 
 def register_conv_template(template: Conversation, override: bool = False):
@@ -419,6 +420,18 @@ def register_conv_template(template: Conversation, override: bool = False):
     chat_templates[template.name] = template
 
 
+def register_conv_template_matching_function(func):
+    matching_function_registry.append(func)
+
+
+def get_conv_template_by_model_path(model_path):
+    for matching_func in matching_function_registry:
+        conv_name = matching_func(model_path)
+        if conv_name is not None:
+            return conv_name
+    return None
+
+
 def chat_template_exists(template_name: str) -> bool:
     return template_name in chat_templates
 
@@ -792,3 +805,86 @@ register_conv_template(
         audio_token="(<audio>./</audio>)",
     )
 )
+
+
+@register_conv_template_matching_function
+def match_deepseek_janus_pro(model_path: str):
+    if (
+        "llama" in model_path.lower()
+        and "3.2" in model_path.lower()
+        and "vision" in model_path.lower()
+    ):
+        return "llama_3_vision"
+
+
+@register_conv_template_matching_function
+def match_deepseek_janus_pro(model_path: str):
+    if "janus" in model_path.lower():
+        return "janus-pro"
+
+
+@register_conv_template_matching_function
+def match_vicuna(model_path: str):
+    if "vicuna" in model_path.lower():
+        return "vicuna_v1.1"
+    if "llava-v1.5" in model_path.lower():
+        return "vicuna_v1.1"
+    if "llava-next-video-7b" in model_path.lower():
+        return "vicuna_v1.1"
+
+
+@register_conv_template_matching_function
+def match_llama2_chat(model_path: str):
+    model_path = model_path.lower()
+    if "llama-2" in model_path and "chat" in model_path:
+        return "llama-2"
+    if (
+        "mistral" in model_path or "mixtral" in model_path
+    ) and "instruct" in model_path:
+        return "llama-2"
+    if "codellama" in model_path and "instruct" in model_path:
+        return "llama-2"
+
+
+@register_conv_template_matching_function
+def match_deepseek_vl(model_path: str):
+    model_path = model_path.lower()
+    if "deepseek" in model_path and "vl2" in model_path:
+        return "deepseek-vl2"
+
+
+@register_conv_template_matching_function
+def match_chat_ml(model_path: str):
+    # import pdb;pdb.set_trace()
+    model_path = model_path.lower()
+    # Now the suffix for qwen2 chat model is "instruct"
+    if "gme" in model_path and "qwen" in model_path and "vl" in model_path:
+        return "gme-qwen2-vl"
+    if "qwen" in model_path and "vl" in model_path:
+        return "qwen2-vl"
+    if (
+        "llava-v1.6-34b" in model_path
+        or "llava-v1.6-yi-34b" in model_path
+        or "llava-next-video-34b" in model_path
+        or "llava-onevision-qwen2" in model_path
+    ):
+        return "chatml-llava"
+
+
+@register_conv_template_matching_function
+def match_gemma_it(model_path: str):
+    model_path = model_path.lower()
+    if "gemma" in model_path and "it" in model_path:
+        return "gemma-it"
+    if "gemma-3" in model_path and "1b" not in model_path:
+        # gemma-3-1b-it is completion model
+        return "gemma-it"
+
+
+@register_conv_template_matching_function
+def match_openbmb_minicpm(model_path: str):
+    model_path = model_path.lower()
+    if "minicpm-v" in model_path:
+        return "minicpmv"
+    elif "minicpm-o" in model_path:
+        return "minicpmo"

python/sglang/srt/entrypoints/engine.py

@@ -58,7 +58,10 @@ from sglang.srt.managers.io_struct import (
 )
 from sglang.srt.managers.scheduler import run_scheduler_process
 from sglang.srt.managers.tokenizer_manager import TokenizerManager
-from sglang.srt.openai_api.adapter import load_chat_template_for_openai_api
+from sglang.srt.openai_api.adapter import (
+    guess_chat_template_name_from_model_path,
+    load_chat_template_for_openai_api,
+)
 from sglang.srt.server_args import PortArgs, ServerArgs
 from sglang.srt.torch_memory_saver_adapter import TorchMemorySaverAdapter
 from sglang.srt.utils import (
@@ -584,6 +587,8 @@ def _launch_subprocesses(
         load_chat_template_for_openai_api(
             tokenizer_manager, server_args.chat_template, server_args.model_path
         )
+    else:
+        guess_chat_template_name_from_model_path(server_args.model_path)
 
     if server_args.completion_template:
         load_completion_template_for_openai_api(server_args.completion_template)

python/sglang/srt/openai_api/adapter.py

@@ -36,6 +36,7 @@ from sglang.srt.conversation import (
     chat_template_exists,
     generate_chat_conv,
     generate_embedding_convs,
+    get_conv_template_by_model_path,
     register_conv_template,
 )
 from sglang.srt.function_call_parser import FunctionCallParser
@@ -163,10 +164,14 @@ def load_chat_template_for_openai_api(tokenizer_manager, chat_template_arg, mode
     else:
         chat_template_name = chat_template_arg
 
-    # Check chat-template
-    # TODO:
-    # 1. Do not import any code from sglang.lang
-    # 2. For VLM, when chat_template_arg is None, set it automatically by guessing from model_path.
+
+def guess_chat_template_name_from_model_path(model_path):
+    global chat_template_name
+    chat_template_name = get_conv_template_by_model_path(model_path)
+    if chat_template_name is not None:
+        logger.info(
+            f"Infer the chat template name from the model path and obtain the result: {chat_template_name}."
+        )
 
 
 async def v1_files_create(