Show overdue in alerts instead of null

hbd/server/threshold.py

@@ -941,48 +941,50 @@ class ThresholdChecker:
         # Format operator symbol
         op_symbol = threshold.operator.value
         
+        # Use a display-friendly value (inf is the sentinel for "overdue")
+        import math
+        display_value = "overdue" if isinstance(value, float) and math.isinf(value) else value
+
         # Format message
         if new_level == AlertLevel.OK:
             lvl = "RECOVERED"
-            message = f"{metric_path} = {value} ({old_level.name} -> OK)"
+            message = f"{metric_path} = {display_value} ({old_level.name} -> OK)"
         elif new_level == AlertLevel.WARNING:
             lvl = "WARNING"
             if threshold_value is not None:
-                # Use display format string
                 threshold_info = self._format_display(
                     threshold.display,
-                    value=value,
+                    value=display_value,
                     threshold_value=threshold_value,
                     op_symbol=op_symbol,
                     plugin_data=plugin_data
                 )
-                message = f"{metric_path} = {value} {threshold_info}"
+                message = f"{metric_path} = {display_value} {threshold_info}"
             else:
-                message = f"{metric_path} = {value}"
+                message = f"{metric_path} = {display_value}"
         elif new_level == AlertLevel.CRITICAL:
             lvl = "CRITICAL"
             if threshold_value is not None:
-                # Use display format string
                 threshold_info = self._format_display(
                     threshold.display,
-                    value=value,
+                    value=display_value,
                     threshold_value=threshold_value,
                     op_symbol=op_symbol,
                     plugin_data=plugin_data
                 )
-                message = f"{metric_path} = {value} {threshold_info}"
+                message = f"{metric_path} = {display_value} {threshold_info}"
             else:
-                message = f"{metric_path} = {value}"
+                message = f"{metric_path} = {display_value}"
         else:
             lvl = "UNKNOWN"
-            message = f"{metric_path} = {value}"
+            message = f"{metric_path} = {display_value}"
         
         # Return the formatted threshold info for storing in AlertState
         formatted_threshold_msg = None
         if threshold_value is not None and new_level != AlertLevel.OK:
             formatted_threshold_msg = self._format_display(
                 threshold.display,
-                value=value,
+                value=display_value,
                 threshold_value=threshold_value,
                 op_symbol=op_symbol,
                 plugin_data=plugin_data