fix biased uncertainty problem

app.py

@@ -379,16 +379,35 @@ def predict_captcha(image):
     prediction, confidence = ctc_decode_with_confidence(log_probs, idx_to_char)
     confidence_pct = confidence * 100
     
+    # Get top-k predictions to check uncertainty
+    top_predictions = ctc_decode_top_k(log_probs, idx_to_char, k=3)
+    
+    # Check if alternatives are close (uncertainty margin)
+    show_alternatives = False
+    if len(top_predictions) >= 2:
+        top1_conf = top_predictions[0][1]
+        top2_conf = top_predictions[1][1]
+        margin = top1_conf - top2_conf
+        
+        # Show alternatives if:
+        # 1. Low confidence (< 70%), OR
+        # 2. Top 2 predictions are very close (margin < 0.1)
+        if confidence < 0.70 or margin < 0.1:
+            show_alternatives = True
+    
     # Format output
     output = f"**Primary Prediction:** {prediction}\n\n"
     
-    # Add status indicator
-    if confidence < 0.6:
-        status = "⚠️ Low Confidence"
-        note = "Visual ambiguity detected (e.g., 0/o, i/1/l confusion)"
+    # Add status and alternatives based on confidence and margin
+    if show_alternatives:
+        if confidence < 0.6:
+            status = "⚠️ Low Confidence"
+        elif confidence < 0.70:
+            status = "⚡ Medium Confidence"
+        else:
+            status = "⚠️ Uncertain"  # High confidence but close alternatives
         
-        # Get alternative predictions when confidence is low
-        top_predictions = ctc_decode_top_k(log_probs, idx_to_char, k=3)
+        note = "Visual ambiguity detected (e.g., 0/o, i/1/l confusion)"
         
         output += f"{status} — {confidence_pct:.1f}%\n"
         output += f"{note}\n\n"
@@ -396,7 +415,8 @@ def predict_captcha(image):
         
         for i, (text, conf) in enumerate(top_predictions, 1):
             conf_pct = conf * 100
-            output += f"{i}. `{text}` — {conf_pct:.1f}%\n"
+            marker = "→" if i == 1 else " "
+            output += f"{marker} {i}. `{text}` — {conf_pct:.1f}%\n"
         
         output += "\n💡 *Tip: Check which makes sense in context*"