small fixes

Signed-off-by: Fredrik Adelöw <freben@gmail.com>

.changeset/rich-ducks-ring.md

@@ -5,6 +5,6 @@
 
 Added predicate-based entity filtering via POST /entities/by-query endpoint.
 
-Supports `$all`, `$any`, `$not`, `$exists`, and `$in` operators for expressive entity queries. Integrated into the existing `queryEntities` flow with full cursor-based pagination, permission enforcement, and `totalItems` support.
+Supports `$all`, `$any`, `$not`, `$exists`, `$in`, and `$hasPrefix` operators for expressive entity queries. Integrated into the existing `queryEntities` flow with full cursor-based pagination, permission enforcement, and `totalItems` support.
 
 The catalog client's `queryEntities()` method automatically routes to the POST endpoint when a `query` predicate is provided.

plugins/catalog-backend/src/service/request/applyPredicateEntityFilterToQuery.ts

@@ -1,5 +1,5 @@
 /*
- * Copyright 2024 The Backstage Authors
+ * Copyright 2026 The Backstage Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -83,7 +83,7 @@ export function applyPredicateEntityFilterToQuery(options: {
   const { filter, targetQuery, onEntityIdField, knex } = options;
 
   // We do not support top-level primitives; all matching happens through objects
-  if (!filter || typeof filter !== 'object' || Array.isArray(filter)) {
+  if (!isObject(filter)) {
     throw new InputError(
       `Invalid filter predicate: top-level primitive values are not supported. ` +
         `Wrap the value in a field expression, e.g. { "kind": ${JSON.stringify(