diff --git a/nexus/adaptive_calibrator.py b/nexus/adaptive_calibrator.py
new file mode 100644
index 0000000..16ff42c
--- /dev/null
+++ b/nexus/adaptive_calibrator.py
@@ -0,0 +1,97 @@
+import json
+import os
+import time
+from typing import Dict, List, Optional
+
+class AdaptiveCalibrator:
+    """
+    Provides online learning for cost estimation accuracy in the sovereign AI stack.
+    Tracks predicted vs actual metrics (latency, tokens, etc.) and adjusts a 
+    calibration factor to improve future estimates.
+    """
+    
+    def __init__(self, storage_path: str = "nexus/calibration_state.json"):
+        self.storage_path = storage_path
+        self.state = {
+            "factor": 1.0,
+            "history": [],
+            "last_updated": 0,
+            "total_samples": 0,
+            "learning_rate": 0.1
+        }
+        self.load()
+
+    def load(self):
+        if os.path.exists(self.storage_path):
+            try:
+                with open(self.storage_path, 'r') as f:
+                    self.state.update(json.load(f))
+            except Exception as e:
+                print(f"Error loading calibration state: {e}")
+
+    def save(self):
+        try:
+            with open(self.storage_path, 'w') as f:
+                json.dump(self.state, f, indent=2)
+        except Exception as e:
+            print(f"Error saving calibration state: {e}")
+
+    def predict(self, base_estimate: float) -> float:
+        """Apply the current calibration factor to a base estimate."""
+        return base_estimate * self.state["factor"]
+
+    def update(self, predicted: float, actual: float):
+        """
+        Update the calibration factor based on a new sample.
+        Uses a simple moving average approach for the factor.
+        """
+        if predicted <= 0 or actual <= 0:
+            return
+
+        # Ratio of actual to predicted
+        # If actual > predicted, ratio > 1 (we underestimated, factor should increase)
+        # If actual < predicted, ratio < 1 (we overestimated, factor should decrease)
+        ratio = actual / predicted
+        
+        # Update factor using learning rate
+        lr = self.state["learning_rate"]
+        self.state["factor"] = (1 - lr) * self.state["factor"] + lr * (self.state["factor"] * ratio)
+        
+        # Record history (keep last 50 samples)
+        self.state["history"].append({
+            "timestamp": time.time(),
+            "predicted": predicted,
+            "actual": actual,
+            "ratio": ratio
+        })
+        if len(self.state["history"]) > 50:
+            self.state["history"].pop(0)
+            
+        self.state["total_samples"] += 1
+        self.state["last_updated"] = time.time()
+        self.save()
+
+    def get_metrics(self) -> Dict:
+        """Return current calibration metrics."""
+        return {
+            "current_factor": self.state["factor"],
+            "total_samples": self.state["total_samples"],
+            "average_ratio": sum(h["ratio"] for h in self.state["history"]) / len(self.state["history"]) if self.state["history"] else 1.0
+        }
+
+if __name__ == "__main__":
+    # Simple test/demo
+    calibrator = AdaptiveCalibrator("nexus/test_calibration.json")
+    
+    print(f"Initial factor: {calibrator.state['factor']}")
+    
+    # Simulate some samples where we consistently underestimate by 20%
+    for _ in range(10):
+        base = 100.0
+        pred = calibrator.predict(base)
+        actual = 120.0 # Reality is 20% higher
+        calibrator.update(pred, actual)
+        print(f"Pred: {pred:.2f}, Actual: {actual:.2f}, New Factor: {calibrator.state['factor']:.4f}")
+    
+    print("Final metrics:", calibrator.get_metrics())
+    os.remove("nexus/test_calibration.json")