diff --git a/.env.example b/.env.example
index 48dd0429..cc12b4d5 100644
--- a/.env.example
+++ b/.env.example
@@ -26,4 +26,4 @@ BRAVE_API_KEY=""
 SPOONACULAR_KEY=""
 HF_API_KEY="Huggingface api key"
 
-MODEL_NAME=""
\ No newline at end of file
+MODEL_NAME="gpt-4"
\ No newline at end of file
diff --git a/swarms/agents/utils/manager.py b/swarms/agents/utils/manager.py
index 0c73ee9e..72f2f978 100644
--- a/swarms/agents/utils/manager.py
+++ b/swarms/agents/utils/manager.py
@@ -13,7 +13,7 @@ from .builder import AgentBuilder
 from .callback import EVALCallbackHandler, ExecutionTracingCallbackHandler
 
 
-CallbackManager.set_handler(EVALCallbackHandler())
+CallbackManager.set_handler(handler=EVALCallbackHandler())
 
 
 class AgentManager:
diff --git a/swarms/agents/workers/metaprompt_worker.py b/swarms/agents/workers/PromptWorker.py
similarity index 100%
rename from swarms/agents/workers/metaprompt_worker.py
rename to swarms/agents/workers/PromptWorker.py