[AMD][Fix] AgentX HIP TPOT regression when SGLANG_SIMULATE_ACC_LEN is set (#40598)

python/sglang/srt/arg_groups/speculative_hook.py

@@ -16,6 +16,7 @@ from sglang.srt.arg_groups.overrides import (
     resolving_view,
     run_post_process_pass,
 )
+from sglang.srt.environ import envs
 from sglang.srt.platforms import current_platform
 from sglang.srt.runtime_context import get_platform
 
@@ -35,6 +36,7 @@ def _should_auto_enable_hip_rejection_sampling(
     accept_threshold_single: float,
     accept_threshold_acc: float,
     enable_deterministic_inference: bool,
+    simulate_acc_len: float = -1.0,
 ) -> bool:
     """Whether HIP may default ``speculative_use_rejection_sampling`` on.
 
@@ -43,6 +45,10 @@ def _should_auto_enable_hip_rejection_sampling(
     would crash configs that previously ran greedy on HIP, including EAGLE3
     stage-a ``test_basic_sanity_eagle3`` (draft 32000 vs target 128256). Skip
     EAGLE3 and any EAGLE run that already has a token map.
+
+    Also skip when ``SGLANG_SIMULATE_ACC_LEN`` is on: AgentX throughput still
+    runs the real EAGLE verify then overwrites accept length, so the Triton
+    chain sampler is paid for and thrown away.
     """
     return (
         is_hip
@@ -53,6 +59,7 @@ def _should_auto_enable_hip_rejection_sampling(
         and accept_threshold_single == 1.0
         and accept_threshold_acc == 1.0
         and not enable_deterministic_inference
+        and simulate_acc_len <= 0
     )
 
 
@@ -1025,6 +1032,7 @@ def _handle_eagle_family(server_args: ServerArgs) -> None:
         accept_threshold_single=cfg.speculative_accept_threshold_single,
         accept_threshold_acc=cfg.speculative_accept_threshold_acc,
         enable_deterministic_inference=cfg.enable_deterministic_inference,
+        simulate_acc_len=float(envs.SGLANG_SIMULATE_ACC_LEN.get()),
     ):
         declare_resolution(
             server_args,

test/registered/unit/spec/test_eagle_gate_routing.py

@@ -122,6 +122,12 @@ class TestHipAutoEnableRejectionSampling(CustomTestCase):
     def test_already_on_is_a_no_op(self):
         self.assertFalse(_hip_auto_enable(use_rejection_sampling=True))
 
+    def test_simulate_acc_len_stays_off(self):
+        # AgentX throughput overwrites accept after real verify; skip the
+        # Triton chain sampler so HIP stays on the greedy argmax path.
+        self.assertFalse(_hip_auto_enable(simulate_acc_len=3.39))
+        self.assertTrue(_hip_auto_enable(simulate_acc_len=-1.0))
+
 
 if __name__ == "__main__":
     unittest.main()