diff --git a/scripts/backfill_customer_hints.py b/scripts/backfill_customer_hints.py
index a5f6f4d40..22a39b0f5 100644
--- a/scripts/backfill_customer_hints.py
+++ b/scripts/backfill_customer_hints.py
@@ -161,6 +161,8 @@ async def _resolve_batch(
 async def _run(args: argparse.Namespace) -> dict[str, object]:
     if args.hint_code and args.all:
         raise ValueError("--hint-code and --all cannot be combined")
+    if not args.hint_code and not args.all:
+        raise ValueError("one of --hint-code or --all is required")
     # The resolution channel itself must be configured; hierarchy inference
     # and verification are separately optional -- resolve_customer_hint
     # falls back to a flat entity when they decline, same as its own
@@ -170,7 +172,7 @@ async def _run(args: argparse.Namespace) -> dict[str, object]:
     resolution_client = _customer_hint_resolution_client()
     verification_client = _relation_verification_client()
     hierarchy_client = _corporate_hierarchy_inference_client()
-    limit = 1 if args.hint_code or not args.all else args.limit
+    limit = 1 if args.hint_code else args.limit
 
     pool = await asyncpg.create_pool(settings.database_url, min_size=1, max_size=1)
     try:
diff --git a/tests/test_backfill_customer_hints.py b/tests/test_backfill_customer_hints.py
index b895665fa..1581c332f 100644
--- a/tests/test_backfill_customer_hints.py
+++ b/tests/test_backfill_customer_hints.py
@@ -27,6 +27,19 @@ def test_run_rejects_hint_code_and_all_combined() -> None:
         raise AssertionError("expected ValueError")
 
 
+def test_run_rejects_neither_hint_code_nor_all() -> None:
+    # A bare invocation must not silently resolve one real hint via a live
+    # orchestrator call -- an operator running this with no flags almost
+    # certainly expected a no-op, not a real provider call.
+    args = argparse.Namespace(hint_code=None, all=False, limit=25, hint_timeout=120.0)
+    try:
+        asyncio.run(backfill._run(args))
+    except ValueError as exc:
+        assert "one of --hint-code or --all is required" in str(exc)
+    else:
+        raise AssertionError("expected ValueError")
+
+
 def test_resolve_batch_counts_resolved_declined_and_failed(monkeypatch) -> None:
     outcomes = {
         "CUST-1": {"corporate_entity_id": "e-1", "entity_name": "Acme", "linked_post_count": 3,