Pin Arena environments to stable Verifiers

tests/test_probe.py

@@ -74,6 +74,30 @@ def discovered_tasksets() -> set[str]:
 
 
 class RootProbeIntegrationTests(unittest.TestCase):
+    def test_prime_verifiers_boundary_is_pinned_and_upstream_owned(self) -> None:
+        manifests = sorted((ROOT / "environments").glob("*/pyproject.toml"))
+        configs = sorted((ROOT / "configs").glob("*.toml"))
+        self.assertTrue(manifests)
+        self.assertTrue(configs)
+
+        for manifest in manifests:
+            with self.subTest(manifest=manifest.parent.name):
+                data = tomllib.loads(manifest.read_text(encoding="utf-8"))
+                self.assertIn("verifiers==0.3.1", data["project"]["dependencies"])
+
+        for config in configs:
+            with self.subTest(config=config.stem):
+                data = tomllib.loads(config.read_text(encoding="utf-8"))
+                agent = data["env"]["agent"]
+                self.assertEqual(agent["harness"]["id"], "null")
+                self.assertEqual(agent["runtime"]["type"], "subprocess")
+
+        self.assertEqual(
+            list((ROOT / "environments").glob("**/harness.py")),
+            [],
+            msg="Arena environments must use Verifiers harnesses, not ship a parallel one",
+        )
+
     def test_public_root_probe_gates_every_environment(self) -> None:
         completed = subprocess.run(
             [sys.executable, "probe.py"],