[V1] V1 Enablement Oracle (#13726)

Signed-off-by: rshaw@neuralmagic.com <rshaw@neuralmagic.com>
Co-authored-by: rshaw@neuralmagic.com <rshaw@neuralmagic.com>
Co-authored-by: Nicolò Lucchesi <nlucches@redhat.com>
Co-authored-by: Tyler Michael Smith <tyler@neuralmagic.com>
Co-authored-by: Michael Goin <michael@neuralmagic.com>

tests/entrypoints/llm/test_lazy_outlines.py

@@ -3,12 +3,21 @@
 import sys
 from contextlib import nullcontext
 
+import pytest
 from vllm_test_utils import BlameResult, blame
 
 from vllm import LLM, SamplingParams
 from vllm.distributed import cleanup_dist_env_and_memory
 
 
+@pytest.fixture(scope="function", autouse=True)
+def use_v0_only(monkeypatch):
+    """
+    V1 only supports xgrammar so this is irrelevant.
+    """
+    monkeypatch.setenv('VLLM_USE_V1', '0')
+
+
 def run_normal_opt125m():
     prompts = [
         "Hello, my name is",