diff --git a/android/src/services/brainApi.ts b/android/src/services/brainApi.ts
index 5069b6f..e051594 100644
--- a/android/src/services/brainApi.ts
+++ b/android/src/services/brainApi.ts
@@ -54,6 +54,18 @@ function _newRequestId(): string {
   return `brain_${Date.now().toString(36)}_${_nextId}`;
 }
 
+/** Mini-Query-String-Builder ohne URLSearchParams (Hermes-Polyfill kennt
+ *  kein URLSearchParams.set, crasht). Akzeptiert object mit string/number/
+ *  bool-Values; undefined/null/leere Strings werden ausgelassen. */
+function _qs(params: Record<string, unknown>): string {
+  const parts: string[] = [];
+  for (const [k, v] of Object.entries(params)) {
+    if (v === undefined || v === null || v === '') continue;
+    parts.push(`${encodeURIComponent(k)}=${encodeURIComponent(String(v))}`);
+  }
+  return parts.length ? `?${parts.join('&')}` : '';
+}
+
 interface SendOpts {
   method?: 'GET' | 'POST' | 'PATCH' | 'DELETE';
   body?: AnyJson;
@@ -119,29 +131,31 @@ export const brainApi = {
 
   /** Liste aller Memories, optional nach Type gefiltert. */
   listMemories(opts: { type?: string; limit?: number } = {}): Promise<Memory[]> {
-    const qs = new URLSearchParams();
-    if (opts.type) qs.set('type', opts.type);
-    qs.set('limit', String(opts.limit || 500));
-    return _send(`/memory/list?${qs.toString()}`);
+    const qs = _qs({ type: opts.type, limit: opts.limit || 500 });
+    return _send(`/memory/list${qs}`);
   },
 
   /** Volltext-Substring-Suche. */
   searchText(q: string, opts: { type?: string; includePinned?: boolean; k?: number } = {}): Promise<Memory[]> {
-    const qs = new URLSearchParams({ q });
-    if (opts.type) qs.set('type', opts.type);
-    qs.set('include_pinned', String(opts.includePinned !== false));
-    qs.set('k', String(opts.k || 50));
-    return _send(`/memory/search-text?${qs.toString()}`);
+    const qs = _qs({
+      q,
+      type: opts.type,
+      include_pinned: opts.includePinned !== false,
+      k: opts.k || 50,
+    });
+    return _send(`/memory/search-text${qs}`);
   },
 
   /** Semantische Suche (Embedder). */
   searchSemantic(q: string, opts: { type?: string; includePinned?: boolean; k?: number; threshold?: number } = {}): Promise<Memory[]> {
-    const qs = new URLSearchParams({ q });
-    if (opts.type) qs.set('type', opts.type);
-    qs.set('include_pinned', String(opts.includePinned !== false));
-    qs.set('k', String(opts.k || 10));
-    qs.set('score_threshold', String(opts.threshold ?? 0.30));
-    return _send(`/memory/search?${qs.toString()}`);
+    const qs = _qs({
+      q,
+      type: opts.type,
+      include_pinned: opts.includePinned !== false,
+      k: opts.k || 10,
+      score_threshold: opts.threshold ?? 0.30,
+    });
+    return _send(`/memory/search${qs}`);
   },
 
   /** Memory anlegen. */