diff --git a/xtest/sdk/java/cli.sh b/xtest/sdk/java/cli.sh
index cece9630..0a8725e0 100755
--- a/xtest/sdk/java/cli.sh
+++ b/xtest/sdk/java/cli.sh
@@ -96,6 +96,11 @@ if [ "$1" == "supports" ]; then
       exit 1
       ;;
 
+    mechanism-mlkem)
+      set -o pipefail
+      java -jar "$SCRIPT_DIR"/cmdline.jar help encrypt | grep -i "mlkem:768"
+      exit $?
+      ;;
     mechanism-rsa-4096 | mechanism-ec-curves-384-521)
       # rsa4096 support in >= 0.13.0
       set -o pipefail
diff --git a/xtest/tdfs.py b/xtest/tdfs.py
index 50f6e459..d09ca470 100644
--- a/xtest/tdfs.py
+++ b/xtest/tdfs.py
@@ -700,6 +700,64 @@ def skip_connectrpc_skew(encrypt_sdk: SDK, decrypt_sdk: SDK, pfs: PlatformFeatur
     return False
 
 
+def _parse_semver(version: str) -> tuple[int, int, int] | None:
+    """Parse a version string (with optional 'v' prefix) into (major, minor, patch)."""
+    m = _version_re.match(version.lstrip("v"))
+    if not m:
+        return None
+    return (int(m.group(1)), int(m.group(2)), int(m.group(3)))
+
+
+def _otdfctl_semver() -> tuple[int, int, int] | None:
+    """Parse otdfctl version from OTDFCTL_HEADS; None if unresolvable (main, dev, etc.)."""
+    oh = os.environ.get("OTDFCTL_HEADS", "[]")
+    try:
+        heads = json.loads(oh)
+    except json.JSONDecodeError:
+        return None
+    if not heads:
+        return None
+    return _parse_semver(str(heads[0]))
+
+
+# go SDK ≤ this version used pre-ocrypto-0.13.0 hybrid KEM format (non-conformant).
+_PQC_HYBRID_FORMAT_CUTOFF = (0, 33, 0)
+
+
+def skip_pqc_hybrid_format_skew(encrypt_sdk: SDK | None = None) -> None:
+    """Skip if the encrypt SDK or otdfctl predates the lib/ocrypto v0.13.0 hybrid-KEM format.
+
+    Two independent sources of format incompatibility:
+    - otdfctl ≤ 0.33.0: registers hybrid KAS keys in old non-conformant format.
+    - go encrypt SDK ≤ 0.33.0: produces hybrid KEM ciphertexts (wrappedKey) in old format.
+    Either causes opaque crypto failures when paired with a platform that has hybrid PQC
+    support enabled (new-format KAS); skip early with a clear message instead.
+    """
+    pfs = get_platform_features()
+    if (
+        "mechanism-xwing" not in pfs.features
+        and "mechanism-secpmlkem" not in pfs.features
+    ):
+        return
+    otdfctl_ver = _otdfctl_semver()
+    if otdfctl_ver is not None and otdfctl_ver <= _PQC_HYBRID_FORMAT_CUTOFF:
+        pytest.skip(
+            f"otdfctl v{'.'.join(map(str, otdfctl_ver))} predates lib/ocrypto v0.13.0; "
+            "hybrid key material format is incompatible with this platform"
+        )
+    if (
+        encrypt_sdk is not None
+        and encrypt_sdk.sdk == "go"
+        and encrypt_sdk.is_released()
+    ):
+        sdk_ver = _parse_semver(encrypt_sdk.version)
+        if sdk_ver is not None and sdk_ver <= _PQC_HYBRID_FORMAT_CUTOFF:
+            pytest.skip(
+                f"{encrypt_sdk} predates lib/ocrypto v0.13.0; "
+                "hybrid KEM ciphertext format is incompatible with this platform"
+            )
+
+
 def select_target_version(
     encrypt_sdk: SDK, decrypt_sdk: SDK
 ) -> container_version | None:
diff --git a/xtest/test_pqc.py b/xtest/test_pqc.py
index b2fe7d6d..9ad25998 100644
--- a/xtest/test_pqc.py
+++ b/xtest/test_pqc.py
@@ -83,6 +83,7 @@ def test_xwing_roundtrip(
     )
     tdfs.skip_connectrpc_skew(encrypt_sdk, decrypt_sdk, pfs)
     tdfs.skip_hexless_skew(encrypt_sdk, decrypt_sdk)
+    tdfs.skip_pqc_hybrid_format_skew(encrypt_sdk)
 
     attr, key_ids = attribute_with_xwing_key
 
@@ -135,6 +136,7 @@ def test_xwing_with_ec_roundtrip(
     )
     tdfs.skip_connectrpc_skew(encrypt_sdk, decrypt_sdk, pfs)
     tdfs.skip_hexless_skew(encrypt_sdk, decrypt_sdk)
+    tdfs.skip_pqc_hybrid_format_skew(encrypt_sdk)
 
     attr, key_ids = attribute_with_xwing_and_ec_keys
 
@@ -199,6 +201,7 @@ def test_secpmlkem_3_roundtrip(
     )
     tdfs.skip_connectrpc_skew(encrypt_sdk, decrypt_sdk, pfs)
     tdfs.skip_hexless_skew(encrypt_sdk, decrypt_sdk)
+    tdfs.skip_pqc_hybrid_format_skew(encrypt_sdk)
 
     attr, key_ids = attribute_with_secpmlkem_3_key
 
@@ -277,6 +280,7 @@ def test_secpmlkem_5_roundtrip(
     )
     tdfs.skip_connectrpc_skew(encrypt_sdk, decrypt_sdk, pfs)
     tdfs.skip_hexless_skew(encrypt_sdk, decrypt_sdk)
+    tdfs.skip_pqc_hybrid_format_skew(encrypt_sdk)
 
     attr, key_ids = attribute_with_secpmlkem_5_key