diff --git a/backend/igny8_core/ai/tracker.py b/backend/igny8_core/ai/tracker.py
index cab51748..8eb0b5a2 100644
--- a/backend/igny8_core/ai/tracker.py
+++ b/backend/igny8_core/ai/tracker.py
@@ -5,6 +5,7 @@ import time
 import logging
 from typing import List, Dict, Any, Optional, Callable
 from datetime import datetime
+from decimal import Decimal
 from igny8_core.ai.constants import DEBUG_MODE
 
 logger = logging.getLogger(__name__)
@@ -195,24 +196,35 @@ class CostTracker:
     """Tracks API costs and token usage"""
     
     def __init__(self):
-        self.total_cost = 0.0
+        self.total_cost = Decimal('0.0')
         self.total_tokens = 0
         self.operations = []
     
-    def record(self, function_name: str, cost: float, tokens: int, model: str = None):
-        """Record an API call cost"""
+    def record(self, function_name: str, cost, tokens: int, model: str = None):
+        """Record an API call cost
+        
+        Args:
+            function_name: Name of the AI function
+            cost: Cost value (can be float or Decimal)
+            tokens: Number of tokens used
+            model: Model name
+        """
+        # Convert cost to Decimal if it's a float to avoid type mixing
+        if not isinstance(cost, Decimal):
+            cost = Decimal(str(cost))
+        
         self.total_cost += cost
         self.total_tokens += tokens
         self.operations.append({
             'function': function_name,
-            'cost': cost,
+            'cost': float(cost),  # Store as float for JSON serialization
             'tokens': tokens,
             'model': model
         })
     
-    def get_total(self) -> float:
-        """Get total cost"""
-        return self.total_cost
+    def get_total(self):
+        """Get total cost (returns float for JSON serialization)"""
+        return float(self.total_cost)
     
     def get_total_tokens(self) -> int:
         """Get total tokens"""