diff --git a/implementations/python/packages/raes_conformance/conformance/target_probes.py b/implementations/python/packages/raes_conformance/conformance/target_probes.py
index 690b6c83..068025b9 100644
--- a/implementations/python/packages/raes_conformance/conformance/target_probes.py
+++ b/implementations/python/packages/raes_conformance/conformance/target_probes.py
@@ -39,7 +39,13 @@
 from raes_conformance.conformance.validators import _validate_payload
 
 # Default reference scenario the target-conformance adapter probe drives when the
-# caller supplies none. Backend-neutral: a single generic linux vm node.
+# caller supplies none. Backend-neutral: a single generic compute node with no
+# authored OS identity — an authored ``os`` becomes an exact SEM-218
+# realization requirement demanding corroboration no hermetic in-process
+# backend declares, which is what regressed this probe when authored OS
+# identity started carrying through realization. Leaving it unset keeps the
+# probe admissible on every declared envelope, mirroring
+# ``examples/scenarios/cross-backend-minimal.sdl.yaml``.
 #
 # Issue #663 makes this a *default*, not a universal assumption. A fixed-topology
 # emulation or bounded simulation backend that cannot realize this generic
@@ -55,7 +61,6 @@
     nodes:
       vm:
         type: compute
-        os: linux
         resources: {ram: 1 gib, cpu: 1}
         conditions: {health: ops}
         roles: {ops: operator}
diff --git a/implementations/python/tests/test_reference_backend_conformance.py b/implementations/python/tests/test_reference_backend_conformance.py
index 510e9d7a..c7eab272 100644
--- a/implementations/python/tests/test_reference_backend_conformance.py
+++ b/implementations/python/tests/test_reference_backend_conformance.py
@@ -20,6 +20,29 @@ def test_reference_target_requires_opacity_probe_for_positive_declaration():
     assert not report.unsupported_capability_gaps
 
 
+def test_adapter_probes_pass_for_every_hermetic_backend():
+    """The provisioning/snapshot adapter probes must stay envelope-neutral.
+
+    An authored ``os`` in the default probe scenario becomes an exact SEM-218
+    realization requirement no hermetic in-process backend can corroborate,
+    which silently failed these probes for every honest backend when authored
+    OS identity started carrying through realization. Pinning them keeps the
+    default probe admissible on every declared envelope (issue #663's runner
+    parameter stays the escape hatch for bounded backends).
+    """
+
+    from raes_backend_stubs.stubs import create_stub_target
+
+    for target in (create_reference_backend_target(), create_stub_target()):
+        report = run_target_conformance(target)
+        cases = {case.name: case for case in report.cases}
+        for name in ("target-provisioning", "target-snapshot"):
+            assert cases[name].passed, (
+                f"{name} must pass for an honest hermetic backend; "
+                f"diagnostics: {[diag.message for diag in cases[name].diagnostics]}"
+            )
+
+
 def test_reference_target_drives_full_participant_probe_case_set():
     report = run_target_conformance(create_reference_backend_target())