diff --git a/agent/relay_tools.py b/agent/relay_tools.py
index 9f82483edb2..9fb3b487e7e 100644
--- a/agent/relay_tools.py
+++ b/agent/relay_tools.py
@@ -72,7 +72,9 @@ def execute(
 
     if "value" in raw_result and _json_equal(managed, raw_result["json"]):
         return raw_result["value"], observed_args
-    return managed, observed_args
+    if isinstance(managed, str):
+        return managed, observed_args
+    return json.dumps(_jsonable(managed), ensure_ascii=False), observed_args
 
 
 def _jsonable(value: Any) -> Any:
diff --git a/tests/agent/test_relay_tools.py b/tests/agent/test_relay_tools.py
index fb0caff6c04..785dddf2c45 100644
--- a/tests/agent/test_relay_tools.py
+++ b/tests/agent/test_relay_tools.py
@@ -2,6 +2,8 @@
 
 from __future__ import annotations
 
+import json
+
 import pytest
 
 pytest.importorskip("nemo_relay")
@@ -118,7 +120,8 @@ def test_request_rewrite_reaches_authorized_callback_once(relay_turn):
 
     assert callback_args == [{"path": "/approved/path"}]
     assert observed_args == {"path": "/approved/path"}
-    assert result == {"ok": True, "wrapped": True}
+    assert isinstance(result, str)
+    assert json.loads(result) == {"ok": True, "wrapped": True}
 
 
 def test_provider_error_identity_is_preserved(relay_turn):