diff --git a/scripts/check-community-ban-route-inventory.py b/scripts/check-community-ban-route-inventory.py
index ff1f280841..7c942ee83c 100644
--- a/scripts/check-community-ban-route-inventory.py
+++ b/scripts/check-community-ban-route-inventory.py
@@ -430,6 +430,11 @@ def collect_registered_routes() -> Counter:
                         f"{location}: production .{call} registration is not classified; "
                         "use .route with an HTTP method or allow-list it"
                     )
+                elif call == "merge" and prefixes.get(builder):
+                    errors.append(
+                        f"{location}: allow-listed .merge in a nested builder "
+                        "is not classified; merged routes need the parent's prefix"
+                    )
                 elif registration in unrouted_seen:
                     errors.append(
                         f"{location}: allow-listed .{call} registration appears more than once"
diff --git a/scripts/check-community-ban-route-inventory.test.py b/scripts/check-community-ban-route-inventory.test.py
index d0e4bcc1d4..50ca1430ec 100644
--- a/scripts/check-community-ban-route-inventory.test.py
+++ b/scripts/check-community-ban-route-inventory.test.py
@@ -47,7 +47,7 @@ def build_router(extra: str = "") -> str:
 
 
 class RouteScannerFixtures(unittest.TestCase):
-    def scan(self, router: str, admin: str = ADMIN):
+    def scan(self, router: str, admin: str = ADMIN, extra_sources=None):
         with tempfile.TemporaryDirectory() as tmp:
             root = Path(tmp)
             src = root / "crates/buzz-relay/src"
@@ -57,6 +57,10 @@ class RouteScannerFixtures(unittest.TestCase):
             (src / "api/gifs.rs").write_text(GIFS)
             (src / "api/profiles.rs").write_text(PROFILES)
             (src / "api/admin.rs").write_text(admin)
+            for relative, source in (extra_sources or {}).items():
+                path = src / relative
+                path.parent.mkdir(parents=True, exist_ok=True)
+                path.write_text(source)
             saved = scanner.ROOT, scanner.RELAY_SRC
             scanner.ROOT, scanner.RELAY_SRC = root, src
             try:
@@ -88,6 +92,30 @@ class RouteScannerFixtures(unittest.TestCase):
             build_router(".merge(media_router).merge(media_router)"),
         )
 
+    def test_git_settings_merge_requires_root_parent(self):
+        sources = {
+            "api/git/transport.rs": """
+pub fn git_router(state: State) -> Router {
+    Router::new()
+        .route("/git/{owner}/{repo}/info/refs", get(info))
+        .merge(super::settings::router())
+}
+""",
+            "api/git/settings.rs": """
+pub fn router() -> Router {
+    Router::new().route("/git/{owner}/{repo}/default-branch", get(read).put(write))
+}
+""",
+        }
+        routes = self.scan(build_router(".merge(git_router)"), extra_sources=sources)
+        self.assertIn(("relay", "GET", "/git/{owner}/{repo}/default-branch"), routes)
+        self.assertIn(("relay", "PUT", "/git/{owner}/{repo}/default-branch"), routes)
+        with self.assertRaisesRegex(ValueError, r"allow-listed \.merge in a nested builder"):
+            self.scan(
+                build_router('.nest("/alternate", api::git::transport::git_router(state))'),
+                extra_sources=sources,
+            )
+
     def test_root_merge_alias_moved_inside_nest_is_rejected(self):
         self.assert_rejected(
             r"root \.merge registration inside a \.nest target is not classified",