release notes 581 (#207)

Author: mostlyken

pages/whats-new.mdx

@@ -8,6 +8,13 @@ import Image from 'next/image';
 
 # What's new in MOSTLY AI
 
+## 5.8.1
+
+### Resolved Issues
+
+- {/* MSD-XXXX */} Fix prompt caching for Anthropic models during MOSTLY AI Assistant Chats.
+- {/* MSD-XXXX */} Fix exception handling for asynchronous LLM completion calls during MOSTLY AI Assistant Chats.
+
 ## 5.8.0
 
 _December 1st, 2025_