Vendor minimal capnproto

test/foo.capnp

@@ -14,7 +14,3 @@ struct Baz{
 struct Qux{
     id @0 :UInt64;
 }
-
-interface Wrapper  {
-    wrapped @0 (object :AnyPointer);
-}

test/test_vendor.py

@@ -0,0 +1,30 @@
+"""Validation of malformed wire data through the trimmed C++ core."""
+
+import struct
+from pathlib import Path
+
+import capnp
+import pytest
+
+
+@pytest.mark.parametrize("pointer", [3, 7, 0xFFFFFFFF00000003])
+def test_capability_and_reserved_pointers_rejected(pointer):
+    schema = capnp.load(str(Path(__file__).with_name("addressbook.capnp")))
+    # Single segment: AddressBook root (zero data words, one pointer) followed
+    # by a capability/reserved pointer where the people list should be.
+    data = struct.pack("<IIQQ", 0, 2, 1 << 48, pointer)
+    with schema.AddressBook.from_bytes(data) as reader:
+        with pytest.raises(capnp.KjException):
+            _ = reader.people
+        with pytest.raises(capnp.KjException):
+            reader.as_builder()
+        if pointer == 7:
+            with pytest.raises(capnp.KjException):
+                _ = reader.total_size
+
+
+def test_interface_schema_is_rejected(tmp_path):
+    schema = tmp_path / "unsupported.capnp"
+    schema.write_text("@0xdeadbeefdeadbeef; interface Unsupported { ping @0 () -> (); }")
+    with pytest.raises(capnp.KjException, match="Interfaces are not supported"):
+        capnp.load(str(schema))