CrossplayShield

Geyser turns some Bedrock actions into bursts of Java packets: moving a stack is several clicks, and sleeping in a bed can send hundreds of packets per second ( Geyser #6775). Packet limiters tuned for Java clients see an attack and kick the Bedrock player.

CrossplayShield limits packets per type, gives Bedrock players (detected by Floodgate) a wider margin, and only adds what Paper does not already do. It works out of the box.

Measured, not guessed
Peak rates over one second, measured with test bots on Paper 26.3, Folia 26.3 and Paper 1.21.11:

• Inventory clicks: Bedrock player emptying an inventory into a chest 54/s, Java player with an inventory sorting mod 108/s. Limit: 162 (Java), 486 (Bedrock)
• Block breaking: 6/s. Limit: 60 (Java), 180 (Bedrock)
• Block placing: 5/s. Limit: 40 (Java), 120 (Bedrock)

Walking, sleeping, chests, building and mining: no packet blocked, no kick, on all three servers.

Free edition

• Packet limits per type (inventory clicks, creative inventory, books, signs, anvil renames, plugin messages, bundles, block breaking and placing), with a wider margin for Bedrock players
• Packets up to the limit always go through; only the extra ones are dropped. A player is kicked only after 5 seconds at more than twice the limit
• /cs audit: checks your Paper settings (packet limiter, spam limiter, item validation, duplication settings), ViaVersion's packet limiter (which can kick sleeping Bedrock players) and Floodgate, with the line to change for each problem
• Dry-run mode: see what would be blocked without blocking anything
• /cs info: Java or Bedrock, device, packets per second and last blocks of a player
• /cs exempt: exempt a player for a while
• English and French, editable texts, add your own language
• Lightweight: about 2 microseconds per packet with 10 Bedrock players in our benchmark

Full edition (9.99 USD)

• Creative item cleanup: enchantments above vanilla, huge names and lore, attribute modifiers, containers nested in containers, oversized items
• Chunk limits: items on the ground, written books and heavy shulker boxes stored in the containers of a chunk
• Command filter: /plugin:command forms (hidden from autocompletion), regular expressions, maximum length
• Alerts in game and on Discord
• Developer API: a cancellable event before each block

Get it on Payhip: https://payhip.com/b/vG04p

Requirements

• Paper or Folia 1.21.4 to 26.x, Java 21+ (tested on Paper 1.21.11, Paper 26.3 and Folia 26.3)
• PacketEvents 2.14+
• Optional: Floodgate, to give Bedrock players their wider margin

Commands and permissions

• /cs audit, /cs info <player>, /cs exempt <player> [seconds], /cs reload: permission crossplayshield.admin, op by default

Documentation and support
Configuration, commands and API: https://github.com/TheMax98000/CrossplayShield
Bug reports and false positives: https://github.com/TheMax98000/CrossplayShield/issues

Also by the author
BedrockGuard: anti-cheat built for Bedrock players on Geyser servers.
BedrockAssist (free): native Bedrock menus for what Geyser cannot translate.