[Bugfix][HiSparse] Reject cudagraph_mode=FULL at startup (#59688)

Signed-off-by: Matthew Bonanni <mbonanni@redhat.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_config.py

@@ -502,6 +502,17 @@ def test_hisparse_rejects_pipeline_parallelism(monkeypatch):
         )
 
 
+def test_hisparse_rejects_full_cudagraph_mode(monkeypatch):
+    monkeypatch.setattr(current_platform, "is_cuda", lambda: True)
+    monkeypatch.setattr(current_platform, "support_static_graph_mode", lambda: True)
+    monkeypatch.setattr("vllm.config.vllm.HAS_TRITON", True)
+    with pytest.raises(ValueError, match="does not support cudagraph_mode=FULL"):
+        VllmConfig(
+            attention_config=AttentionConfig(hisparse_config=HiSparseConfig()),
+            compilation_config=CompilationConfig(cudagraph_mode=CUDAGraphMode.FULL),
+        )
+
+
 def test_hisparse_rejects_disabled_hybrid_kv_cache_manager(monkeypatch):
     monkeypatch.setattr(current_platform, "is_cuda", lambda: True)
     monkeypatch.setattr("vllm.config.vllm.HAS_TRITON", True)

vllm/config/vllm.py

@@ -1836,6 +1836,12 @@ class VllmConfig:
                 raise ValueError(
                     "HiSparse does not support decode context parallelism."
                 )
+            if self.compilation_config.cudagraph_mode == CUDAGraphMode.FULL:
+                raise ValueError(
+                    "HiSparse does not support cudagraph_mode=FULL; use "
+                    "FULL_AND_PIECEWISE (the default), which captures FULL graphs "
+                    "for decode batches."
+                )
             if not self.scheduler_config.scheduler_reserve_full_isl:
                 # Without it, async loads admitted against free host blocks can
                 # each wait on host pages the others hold, and waiting requests