diff --git a/app/api/admin.py b/app/api/admin.py
index 0514f51..947a712 100644
--- a/app/api/admin.py
+++ b/app/api/admin.py
@@ -242,6 +242,16 @@ _KNOWN_FIELDS: dict[str, dict[str, dict]] = {
                         "or sync rejected. 0 disables the gate. Default 10737418240 = 10 GiB."
                     ),
                 },
+                "bq_max_scan_bytes": {
+                    "kind": "int",
+                    "default": 5368709120,
+                    "hint": (
+                        "Cost guardrail for `da query --remote` against query_mode='remote' "
+                        "BQ rows (dry-run check on the underlying SELECT before execute). "
+                        "Bytes processed; exceeds → 400 remote_scan_too_large with a "
+                        "`da fetch` suggestion. 0 disables the gate. Default 5368709120 = 5 GiB."
+                    ),
+                },
             },
         },
         "keboola": {
@@ -795,6 +805,7 @@ class ServerConfigUpdateRequest(BaseModel):
 _BQ_OPTIONAL_FIELD_DEFAULTS: Dict[str, Any] = {
     "billing_project": "",
     "max_bytes_per_materialize": 10737418240,
+    "bq_max_scan_bytes": 5368709120,
 }
 
 
diff --git a/app/api/query.py b/app/api/query.py
index 7c56016..ce80abd 100644
--- a/app/api/query.py
+++ b/app/api/query.py
@@ -47,9 +47,10 @@ BQ_PATH = re.compile(
 
 def _default_remote_query_cap_bytes() -> int:
     """5 GiB default cap on /api/query BQ-touching scans. Configurable via
-    `api.query.bq_max_scan_bytes` in /admin/server-config.
+    `data_source.bigquery.bq_max_scan_bytes` in /admin/server-config —
+    sits next to `max_bytes_per_materialize` for visual symmetry.
     """
-    raw = get_value("api", "query", "bq_max_scan_bytes", default=5_368_709_120)
+    raw = get_value("data_source", "bigquery", "bq_max_scan_bytes", default=5_368_709_120)
     try:
         return int(raw) if raw is not None else 5_368_709_120
     except (TypeError, ValueError):