ServerBooster v3.5.1

Major stability and security update with 25+ improvements across the entire plugin.

🔧 Bug Fixes

• Block Limiter off-by-one fixed — Limits now work correctly. A limit of 4 allows exactly 4 blocks, not 3. This affected all category limits (hoppers,
  chests, crafting tables, enchanting tables, etc.), custom material limits, and entity placement limits (item frames, paintings).
• Block Limiter cache poisoning fixed — Previously, after a denied placement, the count cache could store incorrect values for up to 5 seconds,
  causing additional false denials. Cache is now properly invalidated on every placement attempt.
• Block Limiter deny message now shows accurate count — The message no longer includes the temporarily placed block in its count.
• Hologram checksum migration — Items stacked before this update are now automatically migrated to the new checksum format without data loss.
  Previously, updating could reset stacked items to 1.

🔒 Security Improvements

• Hologram item checksum hardened — Stack integrity checksums now use a unique per-server salt, preventing PDC manipulation exploits that could allow
  item duplication.
• Hopper ground item pickup race condition patched — Added UUID-based locking to prevent two hoppers from processing the same ground item
  simultaneously.
• Hopper statistics are now thread-safe — Transfer counters migrated to atomic operations.
• Redstone tick limiter no longer holds block references in queue — Queued throttled updates now store coordinates instead of direct block references,
  preventing potential issues with unloaded chunks.

⚡ Performance Optimizations

• NMS NamespacedKey cached — The frozen entity tag key is now created once at startup instead of on every entity check, eliminating thousands of
  unnecessary object allocations per optimization cycle.
• TPS access optimized — The plugin now uses Paper's native TPS API directly instead of falling back to NMS reflection.
• Entity Optimizer dead entity cleanup — Added periodic cleanup of frozen entity IDs for entities that no longer exist, preventing unbounded memory
  growth on long-running servers.
• Hologram clear uses targeted entity lookup — clearHolograms now uses getEntitiesByClass instead of iterating all world entities.

🛡️ Stability Improvements

• Coroutine lifecycle completely reworked — The plugin scope is now properly cancelled with cancelAndJoin() on shutdown, ensuring all async
  operations complete cleanly before the plugin disables. Previously, coroutines could continue running briefly after shutdown.
• Orphan coroutine scope removed from commands — The command handler now shares the plugin's managed scope instead of creating its own untracked
  scope.
• Villager Optimizer main-thread bridge rewritten — Replaced CompletableDeferred pattern with proper suspendCancellableCoroutine, fixing potential
  task leaks on coroutine cancellation.
• Entity Optimizer error handling fixed — Exceptions in coroutines are now properly propagated instead of being silently converted to cancellation
  signals.
• CancellationException properly re-thrown — Fixed multiple catch blocks across Entity Optimizer and Villager Optimizer that were swallowing
  cancellation exceptions, which could break structured concurrency.
• Entity validity checks added — Batch entity processing now verifies entity.isValid alongside isDead checks before applying optimizations.
• Event priorities corrected in Hologram Manager — Item spawn and player drop events changed from MONITOR (observe-only) to HIGH priority,
  following Bukkit event contract.

📦 Other Changes

• Config data classes use immutable lists — World lists in configuration models are now List instead of MutableList, preventing accidental
  modification at runtime.
• Tab completion filtered by permissions — Players now only see commands they have permission to use in tab suggestions.
• Removed dead code — Cleaned up unused ChunkPosition class and redundant entity.remove() call after event cancellation.

Compatibility

• Minecraft: 1.17 - 1.21.x
• Server Software: Paper, Spigot
• Java: 17+

Upgrade Notes

• Drop-in replacement for any 3.x version. No configuration changes required.
• Stacked items from previous versions will be automatically migrated on first load.
• The plugin generates a checksum-salt value in config.yml on first startup — do not modify this value.