Urgent model support: support gemma-3-it (#4424)

python/sglang/srt/conversation.py

@@ -45,6 +45,7 @@ class SeparatorStyle(IntEnum):
     DEEPSEEK_CHAT = auto()
     METAMATH = auto()
     QWEN2_VL_EMBED = auto()
+    GEMMA3 = auto()
 
 
 @dataclasses.dataclass
@@ -285,6 +286,18 @@ class Conversation:
                 else:
                     ret += role + ":"
             return ret
+        elif self.sep_style == SeparatorStyle.GEMMA3:
+            ret = system_prompt
+            for i, (role, message) in enumerate(self.messages):
+                if message:
+                    if i == 0:
+                        ret += message + self.sep
+                    else:
+                        ret += role + message + self.sep
+                else:
+                    ret += role
+            return ret
+
         else:
             raise ValueError(f"Invalid style: {self.sep_style}")
 
@@ -604,6 +617,20 @@ register_conv_template(
     )
 )
 
+# Reference: https://huggingface.co/google/gemma-3-4b-it/blob/main/config.json
+register_conv_template(
+    Conversation(
+        name="gemma-it",
+        system_message="You are a helpful assistant.",
+        system_template="<bos><start_of_turn>user{system_message}\n\n",
+        roles=("<start_of_turn>user\n", "<start_of_turn>model\n"),
+        sep="<end_of_turn>\n",
+        sep_style=SeparatorStyle.GEMMA3,
+        stop_str=["<end_of_turn>"],
+        image_token="<start_of_image>",
+    )
+)
+
 # Reference: https://huggingface.co/Alibaba-NLP/gme-Qwen2-VL-2B-Instruct#usage
 register_conv_template(
     Conversation(