From dd6ec02965254291b7bf2c1a90f5eb9a5a5051d4 Mon Sep 17 00:00:00 2001
From: Beichen Ma <mabeichen12@gmail.com>
Date: Sun, 24 Aug 2025 20:24:50 -0700
Subject: [PATCH] Add target module validation for init adapters (#9429)

---
 python/sglang/srt/lora/lora_manager.py | 41 ++++++++++++++++++--------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/python/sglang/srt/lora/lora_manager.py b/python/sglang/srt/lora/lora_manager.py
index ef1120d1e..e3560e05d 100644
--- a/python/sglang/srt/lora/lora_manager.py
+++ b/python/sglang/srt/lora/lora_manager.py
@@ -420,20 +420,37 @@ class LoRAManager:
     ):
         """Infer LoRA target modules and max_lora_rank from loaded adapters if not provided."""
 
-        if target_modules is not None:
-            self.target_modules = set(target_modules)
-        else:
-            self.target_modules = set()
-            for config in self.configs.values():
-                if not isinstance(config.target_modules, list):
+        self.target_modules = (
+            get_normalized_target_modules(target_modules) if target_modules else set()
+        )
+
+        for lora_id, config in self.configs.items():
+            if not isinstance(config.target_modules, list):
+                raise ValueError(
+                    f"SGLang currently only supports inferring LoRA target modules when a list of "
+                    "suffixes is provided in `target_modules` field of PEFT config. Please explicitly "
+                    "specify `--lora-target-modules` during server startup. You can specify `all` to "
+                    "enable all support modules types. "
+                )
+
+            adapter_target_modules = get_normalized_target_modules(
+                config.target_modules
+            )
+
+            if target_modules is not None:
+                # When `--lora-target-modules` is provided, validate adapter target modules is a subset of the specified target modules.
+                if not adapter_target_modules.issubset(self.target_modules):
+                    unsupported_modules = adapter_target_modules - self.target_modules
+                    lora_name = self.lora_refs[lora_id].lora_name
                     raise ValueError(
-                        f"SGLang currently only supports inferring LoRA target modules when a list of "
-                        "suffixes is provided in `target_modules` field of PEFT config. Please explicitly "
-                        "specify `--lora-target-modules` during server startup. You can specify `all` to "
-                        "enable all support modules types. "
+                        f"LoRA adapter '{lora_name}' contains target modules {sorted(unsupported_modules)} "
+                        f"that are not included in the specified --lora-target-modules {sorted(self.target_modules)}. "
+                        f"Please update --lora-target-modules to include all required modules: "
+                        f"{sorted(self.target_modules | adapter_target_modules)}, or use 'all' to enable all supported modules."
                     )
-                self.target_modules.update(config.target_modules)
-        self.target_modules = get_normalized_target_modules(self.target_modules)
+            else:
+                # Otherwise, infer target_modules from adapter configs.
+                self.target_modules.update(adapter_target_modules)
 
         if max_lora_rank is not None:
             self.max_lora_rank = max_lora_rank