Add incremental adapter compiler boundary

tests/test_changesets.py

@@ -268,6 +268,46 @@ class DocForgeChangesetTests(unittest.TestCase):
             with self.assertRaisesRegex(DocForgeError, "Canonical project changed"):
                 service.apply("apply-all", str(final["changeset_hash"]))
 
+    def test_relationship_only_update_is_hash_bound_and_does_not_rewrite_node(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = self.copy_fixture(Path(directory))
+            project = Project.open(root)
+            store = ChangesetStore(project, "alpha-editor")
+            workflow = next(
+                node for node in project.load().nodes if node.node_id == "guide.workflow"
+            )
+            created = store.create("relationship-only")
+            proposed = store.propose_relationship_update(
+                changeset_id="relationship-only",
+                expected_changeset_hash=str(created["changeset_hash"]),
+                node_id="guide.workflow",
+                expected_content_hash=workflow.content_hash,
+                relationship_changes=[
+                    {
+                        "action": "remove",
+                        "source_id": "guide.workflow",
+                        "relation": "depends_on",
+                        "target_id": "guide.foundation",
+                    }
+                ],
+                rationale="Queue one relationship correction without changing node content.",
+            )
+
+            change = store.diff("relationship-only")["changes"][0]
+            self.assertEqual("update", change["operation"])
+            self.assertEqual("", change["content_diff"])
+            self.assertEqual({}, change["metadata"])
+            self.assertEqual(1, proposed["projected_edge_count"])
+            with self.assertRaisesRegex(DocForgeError, "at least one"):
+                store.propose_relationship_update(
+                    changeset_id="relationship-only",
+                    expected_changeset_hash=str(proposed["changeset_hash"]),
+                    node_id="guide.foundation",
+                    expected_content_hash=self.node_hash(project, "guide.foundation"),
+                    relationship_changes=[],
+                    rationale="Reject an empty relationship operation.",
+                )
+
     def test_optimistic_and_cross_changeset_conflicts_preserve_both_proposals(self) -> None:
         with tempfile.TemporaryDirectory() as directory:
             root = self.copy_fixture(Path(directory))