Enable 1.21 experimental features

core/src/main/java/org/geysermc/geyser/network/UpstreamPacketHandler.java

@@ -232,6 +232,9 @@ public class UpstreamPacketHandler extends LoggingPacketHandler {
                     stackPacket.getExperiments().add(new ExperimentData("data_driven_items", true));
                 }
 
+                // Required for experimental 1.21 features
+                stackPacket.getExperiments().add(new ExperimentData("updateAnnouncedLive2023", true));
+
                 session.sendUpstreamPacket(stackPacket);
                 break;
 

core/src/main/java/org/geysermc/geyser/session/GeyserSession.java

@@ -1544,6 +1544,8 @@ public class GeyserSession implements GeyserConnection, GeyserCommandSource {
         startGamePacket.getExperiments().add(new ExperimentData("upcoming_creator_features", true));
         // Needed for certain molang queries used in blocks and items
         startGamePacket.getExperiments().add(new ExperimentData("experimental_molang_features", true));
+        // Required for experimental 1.21 features
+        startGamePacket.getExperiments().add(new ExperimentData("updateAnnouncedLive2023", true));
 
         startGamePacket.setVanillaVersion("*");
         startGamePacket.setInventoriesServerAuthoritative(true);