From 8c334e22243989ebf6cc9ace41fb598d18624ad4 Mon Sep 17 00:00:00 2001
From: Humphrey <humphreysun98@gmail.com>
Date: Sun, 14 Jun 2026 02:50:38 -0500
Subject: [PATCH] fix(io_struct): index extra_key per sub-request in batched
 GenerateReqInput (#26971)

---
 python/sglang/srt/managers/io_struct.py       | 18 ++++++-
 .../unit/managers/test_io_struct.py           | 51 +++++++++++++++++++
 2 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/python/sglang/srt/managers/io_struct.py b/python/sglang/srt/managers/io_struct.py
index 987ec5121..f24bc2408 100644
--- a/python/sglang/srt/managers/io_struct.py
+++ b/python/sglang/srt/managers/io_struct.py
@@ -428,6 +428,7 @@ class GenerateReqInput(BaseReq):
         self._normalize_sampling_params(num)
         self._normalize_logprob_params(num)
         self._normalize_custom_logit_processor(num)
+        self._normalize_extra_key(num)
         self._normalize_bootstrap_params(num)
 
     def _expand_inputs(self, num):
@@ -597,6 +598,21 @@ class GenerateReqInput(BaseReq):
                 "Cannot use list custom_logit_processor with parallel_sample_num > 1"
             )
 
+    def _normalize_extra_key(self, num):
+        """Normalize extra_key for batch processing."""
+        if self.extra_key is None:
+            return
+        if isinstance(self.extra_key, str):
+            self.extra_key = [self.extra_key] * num
+        elif isinstance(self.extra_key, list):
+            if len(self.extra_key) != self.batch_size:
+                raise ValueError(
+                    "The length of extra_key should be equal to the batch size."
+                )
+            self.extra_key = self.extra_key * self.parallel_sample_num
+        else:
+            raise ValueError("extra_key should be a list or a string.")
+
     def _normalize_bootstrap_params(self, num):
         """Normalize bootstrap parameters for batch processing."""
         # Normalize bootstrap_host
@@ -713,7 +729,7 @@ class GenerateReqInput(BaseReq):
             disagg_prefill_dp_rank=self.disagg_prefill_dp_rank,
             conversation_id=self.conversation_id,
             priority=self.priority,
-            extra_key=self.extra_key,
+            extra_key=self.extra_key[i] if self.extra_key is not None else None,
             no_logs=self.no_logs,
             custom_labels=self.custom_labels,
             return_bytes=self.return_bytes,
diff --git a/test/registered/unit/managers/test_io_struct.py b/test/registered/unit/managers/test_io_struct.py
index 42ed241a1..85496ce8e 100644
--- a/test/registered/unit/managers/test_io_struct.py
+++ b/test/registered/unit/managers/test_io_struct.py
@@ -419,6 +419,57 @@ class TestGenerateReqInputNormalization(CustomTestCase):
         req.normalize_batch_and_arguments()
         self.assertEqual(req.lora_path, expected_lora_paths)
 
+    def test_extra_key_normalization(self):
+        """Test normalization of extra_key."""
+        # Per-request list
+        req = GenerateReqInput(
+            text=["Hello", "World"],
+            extra_key=["tenant-A", "tenant-B"],
+            sampling_params=[{}, {}],
+        )
+        req.normalize_batch_and_arguments()
+        self.assertEqual(req.extra_key, ["tenant-A", "tenant-B"])
+        self.assertEqual(req[0].extra_key, "tenant-A")
+        self.assertEqual(req[1].extra_key, "tenant-B")
+
+        # Scalar broadcast
+        req = GenerateReqInput(
+            text=["Hello", "World"],
+            extra_key="shared",
+            sampling_params=[{}, {}],
+        )
+        req.normalize_batch_and_arguments()
+        self.assertEqual(req.extra_key, ["shared", "shared"])
+
+        # None stays None
+        req = GenerateReqInput(text=["Hello", "World"], sampling_params=[{}, {}])
+        req.normalize_batch_and_arguments()
+        self.assertIsNone(req.extra_key)
+        self.assertIsNone(req[0].extra_key)
+
+        # Parallel sampling expansion
+        req = GenerateReqInput(
+            text=["Hello", "World"],
+            extra_key=["tenant-A", "tenant-B"],
+            sampling_params={"n": 2},
+        )
+        req.normalize_batch_and_arguments()
+        self.assertEqual(req.extra_key, ["tenant-A", "tenant-B"] * 2)
+
+        # Wrong-length list
+        req = GenerateReqInput(
+            text=["Hello", "World"],
+            extra_key=["only-one"],
+            sampling_params=[{}, {}],
+        )
+        with self.assertRaisesRegex(ValueError, "batch size"):
+            req.normalize_batch_and_arguments()
+
+        # Non-batched scalar unchanged
+        req = GenerateReqInput(text="Hello", extra_key="solo")
+        req.normalize_batch_and_arguments()
+        self.assertEqual(req.extra_key, "solo")
+
     def test_logprob_parameters_normalization(self):
         """Test normalization of logprob-related parameters."""
         # Test single example