fix: prevent crashes due to logit bias dimension mismatch (#7685)

python/sglang/srt/sampling/sampling_batch_info.py

@@ -322,6 +322,12 @@ class SamplingBatchInfo:
             # Set the flag to True if any of the two has custom logit processor
             self.has_custom_logit_processor = True
 
+        # Merge logit bias - note this has to come before the temperatures tensor update! Otherwise will cause crashes.
+        # See note below on len(self) and len(other).
+        self.logit_bias = merge_bias_tensor(
+            self.logit_bias, other.logit_bias, len(self), len(other), self.device, 0.0
+        )
+
         # Note: because the __len()__ operator is defined on the temperatures tensor,
         # please make sure any merge operation with len(self) or len(other) is done before
         # the merge operation of the temperatures tensor below.
@@ -340,11 +346,6 @@ class SamplingBatchInfo:
         self.need_top_k_sampling |= other.need_top_k_sampling
         self.need_min_p_sampling |= other.need_min_p_sampling
 
-        # Merge logit bias
-        self.logit_bias = merge_bias_tensor(
-            self.logit_bias, other.logit_bias, len(self), len(other), self.device, 0.0
-        )
-
 
 def merge_bias_tensor(
     lhs: Optional[torch.Tensor],