diff --git a/python/sglang/srt/server_args.py b/python/sglang/srt/server_args.py
index 757ae295a..9ed2b5177 100644
--- a/python/sglang/srt/server_args.py
+++ b/python/sglang/srt/server_args.py
@@ -48,6 +48,80 @@ from sglang.srt.utils import (
 logger = logging.getLogger(__name__)
 
 
+# Define constants
+LOAD_FORMAT_CHOICES = [
+    "auto",
+    "pt",
+    "safetensors",
+    "npcache",
+    "dummy",
+    "sharded_state",
+    "gguf",
+    "bitsandbytes",
+    "layered",
+    "remote",
+]
+
+QUANTIZATION_CHOICES = [
+    "awq",
+    "fp8",
+    "gptq",
+    "marlin",
+    "gptq_marlin",
+    "awq_marlin",
+    "bitsandbytes",
+    "gguf",
+    "modelopt",
+    "modelopt_fp4",
+    "petit_nvfp4",
+    "w8a8_int8",
+    "w8a8_fp8",
+    "moe_wna16",
+    "qoq",
+    "w4afp8",
+    "mxfp4",
+]
+
+ATTENTION_BACKEND_CHOICES = [
+    # Common
+    "triton",
+    "torch_native",
+    # NVIDIA specific
+    "cutlass_mla",
+    "fa3",
+    "flashinfer",
+    "flashmla",
+    "trtllm_mla",
+    "trtllm_mha",
+    "dual_chunk_flash_attn",
+    # AMD specific
+    "aiter",
+    "wave",
+    # Other platforms
+    "intel_amx",
+    "ascend",
+]
+
+DISAGG_TRANSFER_BACKEND_CHOICES = ["mooncake", "nixl", "ascend", "fake"]
+
+
+# Allow external code to add more choices
+def add_load_format_choices(choices):
+    LOAD_FORMAT_CHOICES.extend(choices)
+
+
+def add_quantization_method_choices(choices):
+    QUANTIZATION_CHOICES.extend(choices)
+
+
+def add_attention_backend_choices(choices):
+    ATTENTION_BACKEND_CHOICES.extend(choices)
+
+
+def add_disagg_transfer_backend_choices(choices):
+    DISAGG_TRANSFER_BACKEND_CHOICES.extend(choices)
+
+
 @dataclasses.dataclass
 class ServerArgs:
     # Model and tokenizer
@@ -761,18 +835,7 @@ class ServerArgs:
             "--load-format",
             type=str,
             default=ServerArgs.load_format,
-            choices=[
-                "auto",
-                "pt",
-                "safetensors",
-                "npcache",
-                "dummy",
-                "sharded_state",
-                "gguf",
-                "bitsandbytes",
-                "layered",
-                "remote",
-            ],
+            choices=LOAD_FORMAT_CHOICES,
             help="The format of the model weights to load. "
             '"auto" will try to load the weights in the safetensors format '
             "and fall back to the pytorch bin format if safetensors format "
@@ -891,25 +954,7 @@ class ServerArgs:
             "--quantization",
             type=str,
             default=ServerArgs.quantization,
-            choices=[
-                "awq",
-                "fp8",
-                "gptq",
-                "marlin",
-                "gptq_marlin",
-                "awq_marlin",
-                "bitsandbytes",
-                "gguf",
-                "modelopt",
-                "modelopt_fp4",
-                "petit_nvfp4",
-                "w8a8_int8",
-                "w8a8_fp8",
-                "moe_wna16",
-                "qoq",
-                "w4afp8",
-                "mxfp4",
-            ],
+            choices=QUANTIZATION_CHOICES,
             help="The quantization method.",
         )
         parser.add_argument(
@@ -1359,43 +1404,24 @@ class ServerArgs:
         )
 
         # Kernel backend
-        ATTN_BACKENDS = [
-            # Common
-            "triton",
-            "torch_native",
-            # NVIDIA specific
-            "cutlass_mla",
-            "fa3",
-            "flashinfer",
-            "flashmla",
-            "trtllm_mla",
-            "trtllm_mha",
-            "dual_chunk_flash_attn",
-            # AMD specific
-            "aiter",
-            "wave",
-            # Other platforms
-            "intel_amx",
-            "ascend",
-        ]
         parser.add_argument(
             "--attention-backend",
             type=str,
-            choices=ATTN_BACKENDS,
+            choices=ATTENTION_BACKEND_CHOICES,
             default=ServerArgs.attention_backend,
             help="Choose the kernels for attention layers.",
         )
         parser.add_argument(
             "--prefill-attention-backend",
             type=str,
-            choices=ATTN_BACKENDS,
+            choices=ATTENTION_BACKEND_CHOICES,
             default=ServerArgs.prefill_attention_backend,
             help="Choose the kernels for prefill attention layers (have priority over --attention-backend).",
         )
         parser.add_argument(
             "--decode-attention-backend",
             type=str,
-            choices=ATTN_BACKENDS,
+            choices=ATTENTION_BACKEND_CHOICES,
             default=ServerArgs.decode_attention_backend,
             help="Choose the kernels for decode attention layers (have priority over --attention-backend).",
         )
@@ -1959,7 +1985,7 @@ class ServerArgs:
             "--disaggregation-transfer-backend",
             type=str,
             default=ServerArgs.disaggregation_transfer_backend,
-            choices=["mooncake", "nixl", "ascend"],
+            choices=DISAGG_TRANSFER_BACKEND_CHOICES,
             help="The backend for disaggregation transfer. Default is mooncake.",
         )
         parser.add_argument(