Align incremental streaming logprobs with streamed output tokens (#21583)

test/registered/language/test_srt_backend.py

@@ -15,6 +15,7 @@ from sglang.test.test_programs import (
     test_regex,
     test_select,
     test_stream,
+    test_stream_logprobs,
     test_tool_use,
 )
 from sglang.test.test_utils import DEFAULT_MODEL_NAME_FOR_TEST, CustomTestCase
@@ -32,6 +33,7 @@ class TestSRTBackend(CustomTestCase):
             model_path=DEFAULT_MODEL_NAME_FOR_TEST,
             cuda_graph_max_bs=4,
             mem_fraction_static=0.7,
+            incremental_streaming_output=True,
             log_level="info",
         )
         sgl.set_default_backend(cls.backend)
@@ -68,6 +70,9 @@ class TestSRTBackend(CustomTestCase):
     def test_stream(self):
         test_stream()
 
+    def test_stream_logprobs(self):
+        test_stream_logprobs()
+
     def test_regex(self):
         test_regex()