[scheduler] fix: correcting extend_logprob_start_len calculation (#15922)

test/manual/test_forward_split_prefill.py

@@ -93,7 +93,7 @@ class TestForwardSplitPrefill(CustomTestCase):
             )
             req.fill_ids = req.origin_input_ids
             req.extend_input_len = len(req.fill_ids) - len(req.prefix_indices)
-            req.logprob_start_len = len(req.origin_input_ids) - 1
+            req.logprob_start_len = -1
             reqs.append(req)
 
         # Create dummy tree_cache for tests (no prefix caching, just allocation)

test/srt/test_dp_attention.py

@@ -3,8 +3,10 @@ from types import SimpleNamespace
 
 import requests
 
+from sglang.srt.environ import envs
 from sglang.srt.utils import kill_process_tree
 from sglang.test.few_shot_gsm8k import run_eval as run_eval_few_shot_gsm8k
+from sglang.test.kits.radix_cache_server_kit import run_radix_attention_test
 from sglang.test.run_eval import run_eval
 from sglang.test.test_utils import (
     DEFAULT_MLA_MODEL_NAME_FOR_TEST,
@@ -58,6 +60,41 @@ class TestDPAttentionDP2TP2(CustomTestCase):
         self.assertGreater(metrics["score"], 0.8)
 
 
+class TestDPRetract(CustomTestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.model = DEFAULT_MLA_MODEL_NAME_FOR_TEST
+        cls.base_url = DEFAULT_URL_FOR_TEST
+        cls.process = popen_launch_server(
+            cls.model,
+            cls.base_url,
+            timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+            other_args=[
+                "--trust-remote-code",
+                "--tp",
+                "2",
+                "--enable-dp-attention",
+                "--dp",
+                "2",
+                "--max-total-tokens",
+                "4500",
+                "--max-running-requests",
+                "128",
+                "--chunked-prefill-size",
+                "256",
+            ],
+        )
+
+    @classmethod
+    def tearDownClass(cls):
+        kill_process_tree(cls.process.pid)
+
+    def test_radix_attention(self):
+        with envs.SGLANG_TEST_RETRACT.override(True):
+            run_radix_attention_test(self.base_url)
+            self.assertIsNone(self.process.poll())
+
+
 class TestDPAttentionDP2TP2DeepseekV3MTP(CustomTestCase):
     @classmethod
     def setUpClass(cls):