From aadb9720fe6c56395bfcebb88a4dbe8148531f78 Mon Sep 17 00:00:00 2001
From: Jeremy Zhang <jeremy.zhang866@gmail.com>
Date: Wed, 12 Aug 2026 02:15:16 +0800
Subject: [PATCH] fix: route scheduler aborts to multi-tokenizer workers
 (#33940)

---
 .../scheduler_components/output_sender.py     | 11 ++--
 .../test_output_sender.py                     | 63 +++++++++++++++++++
 2 files changed, 69 insertions(+), 5 deletions(-)
 create mode 100644 test/registered/unit/managers/scheduler_components/test_output_sender.py

diff --git a/python/sglang/srt/managers/scheduler_components/output_sender.py b/python/sglang/srt/managers/scheduler_components/output_sender.py
index d4be68081..7ec53f696 100644
--- a/python/sglang/srt/managers/scheduler_components/output_sender.py
+++ b/python/sglang/srt/managers/scheduler_components/output_sender.py
@@ -12,17 +12,18 @@ class SenderWrapper:
     def send_output(
         self,
         output: Union[BaseReq, BaseBatchReq],
-        recv_obj: Optional[Union[BaseReq, BaseBatchReq]] = None,
+        recv_obj: Optional[object] = None,
     ):
         if self.socket is None:
             return
 
+        http_worker_ipc = getattr(recv_obj, "http_worker_ipc", None)
         if (
-            isinstance(recv_obj, BaseReq)
-            and recv_obj.http_worker_ipc is not None
+            isinstance(output, BaseReq)
+            and http_worker_ipc is not None
             and output.http_worker_ipc is None
         ):
-            # handle communicator reqs for multi-http worker case
-            output.http_worker_ipc = recv_obj.http_worker_ipc
+            # Scheduler Req is not a BaseReq but carries the same return route.
+            output.http_worker_ipc = http_worker_ipc
 
         sock_send(self.socket, output)
diff --git a/test/registered/unit/managers/scheduler_components/test_output_sender.py b/test/registered/unit/managers/scheduler_components/test_output_sender.py
new file mode 100644
index 000000000..2a1cc3725
--- /dev/null
+++ b/test/registered/unit/managers/scheduler_components/test_output_sender.py
@@ -0,0 +1,63 @@
+import asyncio
+import unittest
+from unittest.mock import MagicMock, patch
+
+from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.test_utils import CustomTestCase, maybe_stub_sgl_kernel
+
+maybe_stub_sgl_kernel()
+
+from sglang.srt.managers.io_struct import AbortReq
+from sglang.srt.managers.multi_tokenizer_mixin import MultiTokenizerRouter
+from sglang.srt.managers.schedule_batch import Req
+from sglang.srt.managers.scheduler_components.output_sender import SenderWrapper
+from sglang.srt.sampling.sampling_params import SamplingParams
+
+register_cpu_ci(est_time=8, suite="base-a-test-cpu")
+
+
+def _make_scheduler_req(http_worker_ipc: str) -> Req:
+    return Req(
+        rid="scheduler-request",
+        origin_input_text="prompt",
+        origin_input_ids=[1],
+        sampling_params=SamplingParams(),
+        http_worker_ipc=http_worker_ipc,
+    )
+
+
+class TestSenderWrapper(CustomTestCase):
+    @patch("sglang.srt.managers.scheduler_components.output_sender.sock_send")
+    def test_preserves_existing_output_route(self, mock_sock_send):
+        socket = MagicMock()
+        scheduler_req = _make_scheduler_req("ipc:///source-worker")
+        output = AbortReq(
+            rid="already-routed",
+            http_worker_ipc="ipc:///destination-worker",
+        )
+
+        SenderWrapper(socket).send_output(output, scheduler_req)
+
+        self.assertEqual(output.http_worker_ipc, "ipc:///destination-worker")
+        mock_sock_send.assert_called_once_with(socket, output)
+
+    @patch("sglang.srt.managers.scheduler_components.output_sender.sock_send")
+    def test_scheduler_abort_routes_to_origin_worker(self, mock_sock_send):
+        socket = MagicMock()
+        worker_ipc = "ipc:///tokenizer-worker-2"
+        output = AbortReq(rid="overflow-request")
+
+        SenderWrapper(socket).send_output(output, _make_scheduler_req(worker_ipc))
+
+        routed_output = mock_sock_send.call_args.args[1]
+        router = MultiTokenizerRouter.__new__(MultiTokenizerRouter)
+        router.socket_mapping = MagicMock()
+        asyncio.run(router._distribute_result_to_workers(routed_output))
+
+        router.socket_mapping.send_output.assert_called_once_with(
+            worker_ipc, routed_output
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()