[Feat] Return hidden states (experimental) (#3364)

Co-authored-by: Chayenne <zhaochen20@outlook.com>

python/sglang/srt/server_args.py

@@ -160,6 +160,7 @@ class ServerArgs:
     delete_ckpt_after_loading: bool = False
     enable_memory_saver: bool = False
     allow_auto_truncate: bool = False
+    return_hidden_states: bool = False
 
     # Custom logit processor
     enable_custom_logit_processor: bool = False
@@ -896,6 +897,11 @@ class ServerArgs:
             action="store_true",
             help="Enable users to pass custom logit processors to the server (disabled by default for security)",
         )
+        parser.add_argument(
+            "--return-hidden-states",
+            action="store_true",
+            help="Return hidden states in the response.",
+        )
         # Function Calling
         parser.add_argument(
             "--tool-call-parser",