fix: drop past-memory directive and placeholder from agent prompts when memory is empty (#572)

tradingagents/agents/trader/trader.py

@@ -20,8 +20,12 @@ def create_trader(llm, memory):
         if past_memories:
             for i, rec in enumerate(past_memories, 1):
                 past_memory_str += rec["recommendation"] + "\n\n"
-        else:
-            past_memory_str = "No past memories found."
+
+        memory_instruction = (
+            f" Apply lessons from past decisions to strengthen your analysis. Here are reflections from similar situations you traded in and the lessons learned: {past_memory_str.strip()}"
+            if past_memories
+            else ""
+        )
 
         context = {
             "role": "user",
@@ -31,7 +35,7 @@ def create_trader(llm, memory):
         messages = [
             {
                 "role": "system",
-                "content": f"""You are a trading agent analyzing market data to make investment decisions. Based on your analysis, provide a specific recommendation to buy, sell, or hold. End with a firm decision and always conclude your response with 'FINAL TRANSACTION PROPOSAL: **BUY/HOLD/SELL**' to confirm your recommendation. Apply lessons from past decisions to strengthen your analysis. Here are reflections from similar situations you traded in and the lessons learned: {past_memory_str}""",
+                "content": f"You are a trading agent analyzing market data to make investment decisions. Based on your analysis, provide a specific recommendation to buy, sell, or hold. End with a firm decision and always conclude your response with 'FINAL TRANSACTION PROPOSAL: **BUY/HOLD/SELL**' to confirm your recommendation.{memory_instruction}",
             },
             context,
         ]