diff --git a/plugins/memory/hindsight/__init__.py b/plugins/memory/hindsight/__init__.py
index c35b18949358c..23a7621aeef8f 100644
--- a/plugins/memory/hindsight/__init__.py
+++ b/plugins/memory/hindsight/__init__.py
@@ -1060,7 +1060,11 @@ def _tool_retain(self, args: dict) -> str:
                                          occurred_at=args.get("occurred_at"))
         logger.debug("Tool hindsight_retain: bank=%s, content_len=%d, context=%s",
                      self._bank_id, len(content), context)
-        self._retain_batch(item, bank_id=self._bank_id)
+        # Forward the configured retain_async mode: the tool handler must not
+        # silently drop the async/sync choice (defaults differ — aretain_batch
+        # itself defaults retain_async to its own server default, ignoring
+        # the provider config).
+        self._retain_batch(item, bank_id=self._bank_id, retain_async=self._retain_async)
         logger.debug("Tool hindsight_retain: success")
         return "Memory stored successfully."
 
diff --git a/tests/plugins/memory/test_hindsight_provider.py b/tests/plugins/memory/test_hindsight_provider.py
index e5239866be4ad..e4e9fe06f986c 100644
--- a/tests/plugins/memory/test_hindsight_provider.py
+++ b/tests/plugins/memory/test_hindsight_provider.py
@@ -458,6 +458,16 @@ def test_retain_success(self, provider):
         assert "bank_id" not in item
         assert "retain_async" not in item
 
+    @pytest.mark.parametrize("retain_async", [True, False])
+    def test_retain_forwards_configured_async_mode(
+        self, provider_with_config, retain_async
+    ):
+        p = provider_with_config(retain_async=retain_async)
+        p.handle_tool_call("hindsight_retain", {"content": "remember this"})
+
+        call_kwargs = p._client.aretain_batch.call_args.kwargs
+        assert call_kwargs["retain_async"] is retain_async
+
     def test_retain_defaults_item_timestamp_when_no_occurred_at(self, provider, monkeypatch):
         event_time = datetime(2026, 8, 24, 9, 30, tzinfo=ZoneInfo("America/Los_Angeles"))
         monkeypatch.setattr("plugins.memory.hindsight._hermes_now", lambda: event_time)