diff --git a/apps/api/src/services/openclaw.py b/apps/api/src/services/openclaw.py
index b29a68f0..6a07282c 100644
--- a/apps/api/src/services/openclaw.py
+++ b/apps/api/src/services/openclaw.py
@@ -816,8 +816,12 @@ class OpenClawService:
 
         Returns:
             (response, provider, success)
+
+        2026-04-16 ogt + Claude Sonnet 4.6: 修復 — _call_with_fallback 回傳 5 值，
+            call() 回傳 3 值，避免呼叫端 (diagnostician_agent:107) ValueError
         """
-        return await self._call_with_fallback(prompt)
+        response, provider, success, _tokens, _cost = await self._call_with_fallback(prompt)
+        return response, provider, success
 
     # =========================================================================
     # Fallback Chain