release notes 5.6.0 (#203)

Author: mostlyken

pages/whats-new.mdx

@@ -8,6 +8,26 @@ import Image from 'next/image';
 
 # What's new in MOSTLY AI
 
+## 5.6.0
+
+_November 14th, 2025_
+
+### Cardinality Retention for Non-context Foreign Key Models
+
+- {/* MSD-xxxx */} We've increased the accouracy of Non-context Foreign Key Models by preserving more unique values when generating realistic values for non-context foreign keys.
+
+### Enhanced Context Compaction Behavior
+
+- {/* MSD-xxxx */} The MOSTLY AI Assistant now only triggers context compaction after finishing a user request, ensuring that the context is only compacted when it's actually needed.
+
+### Assistant Settings Validation
+
+- {/* MSD-2294 */} At save time, the MOSTLY AI platform now better validates the contents of submitted Assistant settings to ensure expected behavior.
+
+### Upstream dependencies
+
+- Upgraded [Synthetic Data SDK](https://github.com/mostly-ai/mostlyai) to `5.6.0`, [Synthetic Data Engine](https://github.com/mostly-ai/mostlyai-engine) to `2.0.0`.
+
 ## 5.5.0
 
 _November 4th, 2025_