diff --git a/tests/integration/test_cascade_integrity.py b/tests/integration/test_cascade_integrity.py
new file mode 100644
index 000000000..12ddaf508
--- /dev/null
+++ b/tests/integration/test_cascade_integrity.py
@@ -0,0 +1,157 @@
+"""
+Integration tests for cascade part-integrity paths flagged as untested by the
+post-2.3 audit: the Table.delete() enforce post-check (data-driven, with
+rollback), the empty-materialization sentinel, and the U3 upward-rule arm
+(non-primary master FK).
+"""
+
+import pytest
+
+import datajoint as dj
+from datajoint.errors import DataJointError
+
+
+@pytest.fixture(scope="function")
+def schema_by_backend(connection_by_backend, db_creds_by_backend, request):
+    """Create a fresh schema per test (mirrors test_cascade_delete.py)."""
+    backend = db_creds_by_backend["backend"]
+    import time
+
+    test_id = str(int(time.time() * 1000))[-8:]
+    schema_name = f"djtest_cintegrity_{backend}_{test_id}"[:64]
+
+    if connection_by_backend.is_connected:
+        try:
+            connection_by_backend.query(
+                f"DROP DATABASE IF EXISTS {connection_by_backend.adapter.quote_identifier(schema_name)}"
+            )
+        except Exception:
+            pass
+
+    schema = dj.Schema(schema_name, connection=connection_by_backend)
+    yield schema
+
+    if connection_by_backend.is_connected:
+        try:
+            connection_by_backend.query(
+                f"DROP DATABASE IF EXISTS {connection_by_backend.adapter.quote_identifier(schema_name)}"
+            )
+        except Exception:
+            pass
+
+
+def test_enforce_postcheck_raises_and_rolls_back(schema_by_backend):
+    """The data-driven post-check in Table.delete (part rows deleted without
+    their master reaching the cascade) must raise AND roll the transaction
+    back — previously only the direct Part.delete pre-guard had coverage."""
+
+    @schema_by_backend
+    class Ext(dj.Manual):
+        definition = """
+        ext_id : int32
+        """
+
+    @schema_by_backend
+    class Master(dj.Manual):
+        definition = """
+        master_id : int32
+        """
+
+        class P(dj.Part):
+            definition = """
+            -> master
+            -> Ext
+            """
+
+    Ext.insert([(1,)])
+    Master.insert([(1,)])
+    Master.P.insert([(1, 1)])
+
+    # Cascade from Ext reaches the Part but not the Master -> enforce post-check.
+    with pytest.raises(DataJointError, match="before its master"):
+        (Ext & {"ext_id": 1}).delete(prompt=False)  # part_integrity="enforce" default
+
+    # Rollback: nothing was deleted.
+    assert len(Ext()) == 1, "rollback must restore the seed row"
+    assert len(Master.P()) == 1, "rollback must restore the part row"
+    assert len(Master()) == 1
+
+
+def test_cascade_empty_materialization_sentinel(schema_by_backend):
+    """part_integrity='cascade' with a seed matching ZERO part rows: the
+    upward walk materializes an empty master set (always-false sentinel);
+    preview and delete complete without error and no master row is touched."""
+
+    @schema_by_backend
+    class Ext(dj.Manual):
+        definition = """
+        ext_id : int32
+        """
+
+    @schema_by_backend
+    class Master(dj.Manual):
+        definition = """
+        master_id : int32
+        """
+
+        class P(dj.Part):
+            definition = """
+            -> master
+            -> Ext
+            """
+
+    Ext.insert([(1,), (2,)])
+    Master.insert([(1,)])
+    Master.P.insert([(1, 1)])  # only ext 1 is referenced; ext 2 matches nothing
+
+    counts = dj.Diagram.cascade(Ext & {"ext_id": 2}, part_integrity="cascade").counts()
+    assert (
+        counts.get(Master.full_table_name, 1) == 0
+    ), f"master must appear with zero matches (empty-materialization sentinel); got {counts}"
+
+    (Ext & {"ext_id": 2}).delete(prompt=False, part_integrity="cascade")
+    assert len(Ext & {"ext_id": 2}) == 0
+    assert len(Master()) == 1, "master row must be untouched"
+    assert len(Master.P()) == 1, "part row must be untouched"
+
+
+def test_upward_u3_nonprimary_master_fk(schema_by_backend):
+    """U3 arm of the upward walk: a Part whose `-> master` FK is SECONDARY
+    (below the ---). The part's restriction attrs are not a subset of the
+    master's PK and the edge is non-aliased, so U3 must project the part onto
+    its FK columns (`proj(*attr_map.keys())`) to carry `master_id` upward.
+    A bare `proj()` (the pre-#1468 form) would project to the part's PK
+    (ext_id, part_id), share no attributes with Master, and restrict BOTH
+    masters instead of the correct one — the assertion below distinguishes."""
+
+    @schema_by_backend
+    class Ext(dj.Manual):
+        definition = """
+        ext_id : int32
+        """
+
+    @schema_by_backend
+    class Master(dj.Manual):
+        definition = """
+        master_id : int32
+        """
+
+        class P(dj.Part):
+            definition = """
+            -> Ext
+            part_id : int32
+            ---
+            -> master
+            """
+
+    Ext.insert([(1,), (2,)])
+    Master.insert([(1,), (2,)])
+    # part under master 1 references ext 1; part under master 2 references ext 2
+    Master.P.insert([(1, 10, 1), (2, 20, 2)])
+
+    counts = dj.Diagram.cascade(Ext & {"ext_id": 1}, part_integrity="cascade").counts()
+
+    assert counts.get(Master.full_table_name, 0) == 1, (
+        f"only master 1 (via the secondary-FK part row) must be restricted; got {counts} — "
+        "a bare proj() on the U3 arm would have restricted both masters."
+    )