[Fix] Fix split prefill with fa3. (#11428)

python/sglang/srt/layers/logits_processor.py

@@ -137,7 +137,10 @@ class LogitsMetadata:
     @classmethod
     def from_forward_batch(cls, forward_batch: ForwardBatch):
         if (
-            forward_batch.forward_mode.is_extend()
+            (
+                forward_batch.forward_mode.is_extend()
+                or forward_batch.forward_mode.is_split_prefill()
+            )
             and forward_batch.return_logprob
             and not forward_batch.forward_mode.is_target_verify()
         ):
@@ -389,8 +392,8 @@ class LogitsProcessor(nn.Module):
             input_logprob_indices = None
         elif (
             logits_metadata.forward_mode.is_extend()
-            and not logits_metadata.extend_return_logprob
-        ):
+            or logits_metadata.forward_mode.is_split_prefill()
+        ) and not logits_metadata.extend_return_logprob:
             # Prefill without input logprobs.
             if logits_metadata.padded_static_len < 0:
                 last_index = torch.cumsum(logits_metadata.extend_seq_lens, dim=0) - 1

python/sglang/srt/model_executor/forward_batch_info.py

@@ -112,6 +112,7 @@ class ForwardMode(IntEnum):
             self == ForwardMode.EXTEND
             or self == ForwardMode.DRAFT_EXTEND
             or self == ForwardMode.MIXED
+            or self == ForwardMode.SPLIT_PREFILL
         )
 
     def is_cuda_graph(self):