[MoE Refactor] Mxfp4 oracle rebased (#37128)

Signed-off-by: Yongye Zhu <zyy1102000@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/compile/fusions_e2e/conftest.py

@@ -84,7 +84,10 @@ def run_e2e_fusion_test(monkeypatch, caplog_mp_spawn):
 
         # TODO: remove this after finishing migration from envs to model kwargs
         if model_name == "openai/gpt-oss-20b":
-            monkeypatch.setenv("VLLM_USE_FLASHINFER_MOE_MXFP4_MXFP8", "1")
+            from .common import is_blackwell
+
+            if is_blackwell():
+                monkeypatch.setenv("VLLM_USE_FLASHINFER_MOE_MXFP4_MXFP8", "1")
 
         # Disable, compile cache to make sure custom passes run.
         # Otherwise, we can't verify fusion happened through the logs.