PLEASE READ before participating in the Minecraft Beta: 

• Joining the beta will replace your game with a work in progress version of Minecraft 
• You will not have access to Realms and will not be able to join non-beta players while you’re previewing the beta
• Any worlds played while in the beta cannot be opened in previous versions of the game so please make copies of worlds to prevent losing them 
• Beta builds can be unstable and are not representative of final version quality 
• The beta is available only on Xbox One, Windows 10, and Android (Google Play). To join or leave the beta, see aka.ms/JoinMCBeta for detailed instructions

Please enjoy this week’s Bedrock Beta update and send us your feedback at aka.ms/CavesCliffsFeedback and report any bugs at bugs.mojang.com.  

Reminder: We are still tweaking world generation and features may change, please remember make regular backup copies of your favourite worlds! 

Experimental Features 

• Fixed shifted sub-chunks on Caves & Cliffs flat worlds (MCPE-140428)
• Flat worlds with the Caves & Cliffs experimental toggle enabled will properly upgrade to use the new dimension heights 

Non-Experimental Features and Bug Fixes 

Gameplay 

• Fixed an issue where Light Blocks would force players to spawn at the surface of the Overworld  
• Tropical Fish no longer lose their colors upon grabbing them with a Water Bucket and then releasing them (MCPE-137158)  
• Trapdoors show up in the Recipe Book again (MCPE-141441)  
• Lily Pads can once again be placed on water deeper than one block (MCPE-141403)  

Mobs 

• Mobs no longer jump continuously on non-full blocks such as Snow layers (MCPE-141411)  

source: https://feedback.minecraft.net/hc/en-us/articles/4410354576781