Better Anti Dupe
Stops item Duplication and tells you who tried.
Автор: darkstarworks3,4 тыс.10обновлён 16 окт. 2026 г.
ЭкономикаУправлениеТехнологии
Описание
Stops item duplication on your Minecraft server, and tells you who tried.
Better Anti-Dupe watches the items themselves.
It keeps a record of every valuable item a player gains and loses.
Get notified with a [click to teleport] when something's up.
Actively protecting over 350 servers.
Comes with sensible defaults, great documentation and fast support.
Will it work on my server?
| Server software | Paper, Folia, Spigot, or a Paper fork |
| Minecraft | Everything from 1.21.x to 26.3 |
| Java | 21+ for 1.21.x or 25+ for 26.x |
| Anything else | Nothing. Redis is optional. |
Which download do I need?
Minecraft 1.21.x: the plain jar.
Minecraft 26.0 to 26.2: the jar ending in -mc26.
Minecraft 26.3: the jar ending in -mc263.
More info? Read about it in the docs
What it blocks
The classic dupe machines stop working the moment you install the plugin.
Each one has its own switch, in case you want to allow it.
Rail and carpet dupers
One of the oldest dupes in the game.
All it needs is a piston and a rail or carpet.
With Better Anti-Dupe, these dupe-machines are disabled by default.
More info? Read about it in the docs
TNT dupers
TNT dupers power world eaters and flying machines.
They stop working from day one.
Running an anarchy or tech server? One switch turns them back on.
More info? Read about it in the docs
Sand and gravel portal dupers
Sand and gravel can no longer be copied through a portal.
Farms and flying machines that push sand keep working.
More info? Read about it in the docs
Ghost chest windows
A player can't keep taking items from a chest that's already gone.
The window simply closes.
Nobody playing normally will ever notice.
More info? Read about it in the docs
Restart dupes
No machine needed, just good timing during a restart.
Every open window closes as the server shuts down.
Nothing is left to copy.
More info? Read about it in the docs
What it catches
Everything else. It notices when a player holds more than possible.
Carrying more than they earned
The heart of the plugin.
It knows what each player earned, and counts what they hold.
Shulker boxes and bundles included. Holding more? You'll know.
More info? Read about it in the docs
The same dropped item picked up twice
Every dropped item is one of a kind.
If the same one is picked up twice, it was copied.
This is the most certain alert there is.
More info? Read about it in the docs
More drops than a block or item frame gave
Breaking a block or a frame drops a known amount.
Picking up more than that nearby means something was copied.
More info? Read about it in the docs
Small dupes hidden by storing them away
Dupe a few items, hide them in a chest, and hope nobody notices.
It's an old trick.
Small amounts are remembered for a day, and they add up to an alert.
More info? Read about it in the docs
Copies made inside a chest
Some dupes never touch a player's inventory.
The copies simply appear in a chest.
You're told whose items they were, who took them, and where.
More info? Read about it in the docs
Items washed through hoppers
Dupers pass items through hoppers to make them look clean.
The route is written down, so you can follow it.
Or block hoppers from moving watched items at all.
More info? Read about it in the docs
Gaining things impossibly fast
You decide how many of an item anyone could honestly get in a minute.
Going past it makes a player worth a closer look.
More info? Read about it in the docs
Nobody ever seeing them get anything
Duping usually happens alone.
A player whose gains nobody ever sees becomes a little more suspicious.
It never accuses anyone on its own.
More info? Read about it in the docs
Someone editing the records
Every record is sealed to the one before it.
Even an admin can't quietly change history.
One command shows exactly where it was touched.
More info? Read about it in the docs
Crafting, anvils, smithing tables, furnaces, villager trades, enchanting, chests, barrels, ender chests, item frames and animal chests. Everything is monitored and monitored well.
Made for staff, not just for detection
Find the stash
Knowing someone duped is only half the job.
One command lists where they put the items.
Click the coordinates and you're there, even in another world.
More info? Read about it in the docs
Decide in five minutes
Every alert has [History] and [Stash] buttons.
Look, decide, done.
Confirm a duper, clear a false alarm, or take the extras back.
More info? Read about it in the docs
Alerts on your phone
You don't have to be online to know.
Discord, Telegram, Slack, or your own webhook.
Only the serious alerts, and no spam. One command tests your setup.
More info? Read about it in the docs
Watch first, act later
Nothing is taken from anyone until you say so.
Watch the alerts for a while. Once you trust them, turn on automatic removal.
It only ever takes the extras, never a whole stack.
More info? Read about it in the docs
Items stack normally
Your players won't notice a thing.
Watched items stack and trade like any other item.
More info? Read about it in the docs
Hidden from players
Mods that show hidden item data see nothing.
A duper testing on two accounts can't tell which items are watched.
More info? Read about it in the docs
Available in your language
English, Português do Brasil, Español, Deutsch, Русский and Polski are built in.
Every message can be changed to your liking.
More info? Read about it in the docs
Several servers?
Items travel between servers on a network.
Share records through Redis, and a dupe on one server is spotted on another.
More info? Read about it in the docs
Installation
- Download the jar (
-mc26for Minecraft 26.0 to 26.2,-mc263for 26.3). - Drop it into
plugins/and restart the server. - That's it. Testing in-game shows you it working.
More info? Read about it in the docs
Commands
Every command starts with /adp.
| Command | What it does |
|---|---|
/adp ledger suspects | Everyone currently suspected, worst first |
/adp ledger reconcile <player> | Check what an online player carries right now |
/adp ledger history <player> | Their last 15 records |
/adp ledger stash <player> | Where they put the items, with click-to-teleport |
/adp ledger remove <player> | Take back only the extras, after you confirm |
/adp ledger confirm <player> | Mark a real duper |
/adp ledger clear <player> | Mark a false alarm |
/adp ledger verify | Check nobody has edited the records |
antidupe.alerts only sees alerts.
antidupe.ledger can use the commands.
antidupe.admin gets both.
More info? Read about it in the docs
Free and source available
No licence key. Nothing locked behind a premium version.
The source is on GitHub, and issues and pull requests are welcome.
Anonymous statistics
Almost nobody opens a ticket, so I cannot tell which Minecraft versions run it.
Knowing that helps me fight dupes on those versions first.
- Sent: your settings, versions, and counts of dupes caught, removed and blocked.
- Never sent: addresses, server names, player names, or anything from your records.
- Kept private. Public numbers would help dupers pick unprotected servers.
- Error reports are cleaned of passwords, tokens and ids before they leave your server.
Set metrics.enabled: false to send nothing at all.
Nothing is ever shared, sold, or made public.
More info? Read about it in the docs
I take your privacy very seriously -> company privacy policy
Links
- Guide: esmp-fun.gitbook.io/plugins/better-anti-dupe
- Troubleshooting: common problems
- Source and issues: github.com/ESMP-FUN/BetterAntiDupe
- Changelog: CHANGELOG.md
Последние версии
Все версии →release
Better Anti Dupe 4.7.1-mc263
4.7.1-mc26316 окт. 2026 г.207Minecraft: 26.3bukkit, folia, paper, purpur, spigot
Что нового
## [4.7.1] - 2026-10-17
### Added
- **Owner marks are signed.** Every mark is signed with a secret only your server knows, kept in `plugins/BetterAntiDupe/mark-signing.key`. A mark made by hand, in creative mode, with an item editor or a `/give` command, does not match, so it is ignored and can no longer be used to frame another player. Staff get an alert when someone holds an item with a faked mark. Servers sharing a Redis database share the secret by themselves; servers sharing items another way need the same file. New settings `ownership.signed_marks` and `ownership.unsigned_marks`.
- **Marks from before the upgrade are signed as players carry them.** On a server that used the plugin before, older marks stay trusted and get signed during the normal checks. Once `/adp marks` shows hardly any being signed, set `ownership.unsigned_marks: IGNORE`. A brand-new server never trusts unsigned marks.
- **`/adp marks`** shows the key in use, whether older marks are trusted, and how many were signed or found faked since the last start.
- **`/adp fixstacks [player]`** fixes items that look the same but will not stack, by giving that player's mark to their unmarked items and updating their older marks. Items marked to someone else are left alone.
- **API level 2.** `ownership().state(stack)` tells signed, older, faked and other-server marks apart, and alerts have a new kind, `FORGED_MARK`.
### Fixed
- **Shift-click crafting gave items that would not stack.** Only the first item of a shift-click craft got the crafter's mark, so crafting a stack of diamonds into blocks gave one marked block and the rest unmarked, and the two would not stack. Every crafted item is now marked.
release
Better Anti Dupe 4.7.1-mc26
4.7.1-mc2616 окт. 2026 г.138Minecraft: 26.1, 26.1.1, 26.1.2, 26.2bukkit, folia, paper, purpur, spigot
Что нового
## [4.7.1] - 2026-10-17
### Added
- **Owner marks are signed.** Every mark is signed with a secret only your server knows, kept in `plugins/BetterAntiDupe/mark-signing.key`. A mark made by hand, in creative mode, with an item editor or a `/give` command, does not match, so it is ignored and can no longer be used to frame another player. Staff get an alert when someone holds an item with a faked mark. Servers sharing a Redis database share the secret by themselves; servers sharing items another way need the same file. New settings `ownership.signed_marks` and `ownership.unsigned_marks`.
- **Marks from before the upgrade are signed as players carry them.** On a server that used the plugin before, older marks stay trusted and get signed during the normal checks. Once `/adp marks` shows hardly any being signed, set `ownership.unsigned_marks: IGNORE`. A brand-new server never trusts unsigned marks.
- **`/adp marks`** shows the key in use, whether older marks are trusted, and how many were signed or found faked since the last start.
- **`/adp fixstacks [player]`** fixes items that look the same but will not stack, by giving that player's mark to their unmarked items and updating their older marks. Items marked to someone else are left alone.
- **API level 2.** `ownership().state(stack)` tells signed, older, faked and other-server marks apart, and alerts have a new kind, `FORGED_MARK`.
### Fixed
- **Shift-click crafting gave items that would not stack.** Only the first item of a shift-click craft got the crafter's mark, so crafting a stack of diamonds into blocks gave one marked block and the rest unmarked, and the two would not stack. Every crafted item is now marked.
release
Better Anti Dupe 4.7.1
4.7.116 окт. 2026 г.148Minecraft: 1.21, 1.21.1, 1.21.2, 1.21.3, 1.21.4, 1.21.5, 1.21.6, 1.21.7, 1.21.8, 1.21.9, 1.21.10, 1.21.11bukkit, folia, paper, purpur, spigot
Что нового
## [4.7.1] - 2026-10-17
### Added
- **Owner marks are signed.** Every mark is signed with a secret only your server knows, kept in `plugins/BetterAntiDupe/mark-signing.key`. A mark made by hand, in creative mode, with an item editor or a `/give` command, does not match, so it is ignored and can no longer be used to frame another player. Staff get an alert when someone holds an item with a faked mark. Servers sharing a Redis database share the secret by themselves; servers sharing items another way need the same file. New settings `ownership.signed_marks` and `ownership.unsigned_marks`.
- **Marks from before the upgrade are signed as players carry them.** On a server that used the plugin before, older marks stay trusted and get signed during the normal checks. Once `/adp marks` shows hardly any being signed, set `ownership.unsigned_marks: IGNORE`. A brand-new server never trusts unsigned marks.
- **`/adp marks`** shows the key in use, whether older marks are trusted, and how many were signed or found faked since the last start.
- **`/adp fixstacks [player]`** fixes items that look the same but will not stack, by giving that player's mark to their unmarked items and updating their older marks. Items marked to someone else are left alone.
- **API level 2.** `ownership().state(stack)` tells signed, older, faked and other-server marks apart, and alerts have a new kind, `FORGED_MARK`.
### Fixed
- **Shift-click crafting gave items that would not stack.** Only the first item of a shift-click craft got the crafter's mark, so crafting a stack of diamonds into blocks gave one marked block and the rest unmarked, and the two would not stack. Every crafted item is now marked.
release
Better Anti Dupe 4.7.0-mc263
4.7.0-mc26312 окт. 2026 г.74Minecraft: 26.3bukkit, folia, paper, purpur, spigot
Что нового
## [4.7.0] - 2026-10-13
### Added
- **An API for other plugins.** Shops, crates, kits and reward plugins can now tell Better Anti-Dupe when they hand out or take away items, strip the owner mark from template copies, read a player's record, and listen to alerts, protections and automatic removal through normal Bukkit events. It works on Spigot, Paper and Folia from 1.21 up. See "Use it from your plugin" in the docs. The old `recordGrant` hook still works.
- **Stops hidden menu dupes.** Most dupes found in other plugins' menus (backpacks, ender chest plugins, shulker preview plugins, storage menus) start with a cheat client hiding the menu on the player's screen without telling the server it closed. A normal game always closes a menu before the player can mine, build, hit, drop an item, switch hotbar slot or type a command, so doing any of those with a menu still open is now stopped, the menu is closed, and staff get an alert. Normal players are not affected. Works on Paper, Folia and Spigot. New setting `prevent-hidden-menu-dupers`, on by default.
- **Stops the end portal chest dupe.** When the last eye of ender goes into a portal frame with a chest or shulker box where the portal appears, and a land claim, region or "the End is locked" plugin blocks it, the container came back while a copy of it dropped on the ground. On Paper a chest's items dropped too while the chest stayed full, and a shulker box dropped with everything still inside it, so the whole box was doubled. On Spigot the container came back empty next to the copy. The plugin now puts it all back: the container keeps its items and nothing extra is left on the ground. This is an open Paper bug on 26.3. New setting `prevent-reverted-placement-dupers`, on by default.
- **Players are checked a few seconds after they join.** This catches players who come back holding items the server should not have handed back, for example after a crash or a lag machine stopped their data from saving while the items they put away stayed in a chest. New setting `ledger.reconciliation.on_join`, on by default.
- **The console lists Paper's duping settings at startup.** If any duping glitch is switched back on in `config/paper-global.yml` (TNT, rail and carpet machines, sand through end portals, tripwire hooks), the console says so and which of them the plugin still blocks.
### Fixed
- **The owner mark is now hidden on Spigot 1.21.** Spigot before 26.1 uses different internal names, so the part that hides the mark from players' games switched itself off at startup there. It now works on Paper, Folia and Spigot alike, checked by watching what players' games actually receive.
- **A Spigot error on lecterns is guarded.** Spigot can report an empty hand differently from Paper, which could make putting a book on a lectern throw an error there.
- **Memory use on servers that run for weeks.** The plugin kept every player's balances in memory after they left. They are now released five minutes after the player logs off.
### Security
- **Alerts can no longer ping everyone in Discord.** Alert messages are sent with mentions switched off, so nothing in them can ping @everyone, @here or a role.
- **The confirm command uses the player's real name.** `on_confirm_command` now fills in the name the server has on record instead of the text typed after `/adp ledger confirm`.
### Changed
- **Built against Paper 26.3 stable.** Paper now marks 26.3 as stable, and the 26.3 download is built against it. Nothing else changes.
- **No items are taken away right after a crash.** For 30 minutes after a start that follows a crash, "Has X but ledger shows Y" alerts now also say the crash may be the cause, and the plugin does not remove items for any alert that carries that note, even with `auto_delete_dupes` on. A crash can hand a player back their own items, and those should not be deleted.
release
Better Anti Dupe 4.7.0-mc26
4.7.0-mc2612 окт. 2026 г.72Minecraft: 26.1, 26.1.1, 26.1.2, 26.2bukkit, folia, paper, purpur, spigot
Что нового
## [4.7.0] - 2026-10-13
### Added
- **An API for other plugins.** Shops, crates, kits and reward plugins can now tell Better Anti-Dupe when they hand out or take away items, strip the owner mark from template copies, read a player's record, and listen to alerts, protections and automatic removal through normal Bukkit events. It works on Spigot, Paper and Folia from 1.21 up. See "Use it from your plugin" in the docs. The old `recordGrant` hook still works.
- **Stops hidden menu dupes.** Most dupes found in other plugins' menus (backpacks, ender chest plugins, shulker preview plugins, storage menus) start with a cheat client hiding the menu on the player's screen without telling the server it closed. A normal game always closes a menu before the player can mine, build, hit, drop an item, switch hotbar slot or type a command, so doing any of those with a menu still open is now stopped, the menu is closed, and staff get an alert. Normal players are not affected. Works on Paper, Folia and Spigot. New setting `prevent-hidden-menu-dupers`, on by default.
- **Stops the end portal chest dupe.** When the last eye of ender goes into a portal frame with a chest or shulker box where the portal appears, and a land claim, region or "the End is locked" plugin blocks it, the container came back while a copy of it dropped on the ground. On Paper a chest's items dropped too while the chest stayed full, and a shulker box dropped with everything still inside it, so the whole box was doubled. On Spigot the container came back empty next to the copy. The plugin now puts it all back: the container keeps its items and nothing extra is left on the ground. This is an open Paper bug on 26.3. New setting `prevent-reverted-placement-dupers`, on by default.
- **Players are checked a few seconds after they join.** This catches players who come back holding items the server should not have handed back, for example after a crash or a lag machine stopped their data from saving while the items they put away stayed in a chest. New setting `ledger.reconciliation.on_join`, on by default.
- **The console lists Paper's duping settings at startup.** If any duping glitch is switched back on in `config/paper-global.yml` (TNT, rail and carpet machines, sand through end portals, tripwire hooks), the console says so and which of them the plugin still blocks.
### Fixed
- **The owner mark is now hidden on Spigot 1.21.** Spigot before 26.1 uses different internal names, so the part that hides the mark from players' games switched itself off at startup there. It now works on Paper, Folia and Spigot alike, checked by watching what players' games actually receive.
- **A Spigot error on lecterns is guarded.** Spigot can report an empty hand differently from Paper, which could make putting a book on a lectern throw an error there.
- **Memory use on servers that run for weeks.** The plugin kept every player's balances in memory after they left. They are now released five minutes after the player logs off.
### Security
- **Alerts can no longer ping everyone in Discord.** Alert messages are sent with mentions switched off, so nothing in them can ping @everyone, @here or a role.
- **The confirm command uses the player's real name.** `on_confirm_command` now fills in the name the server has on record instead of the text typed after `/adp ledger confirm`.
### Changed
- **Built against Paper 26.3 stable.** Paper now marks 26.3 as stable, and the 26.3 download is built against it. Nothing else changes.
- **No items are taken away right after a crash.** For 30 minutes after a start that follows a crash, "Has X but ledger shows Y" alerts now also say the crash may be the cause, and the plugin does not remove items for any alert that carries that note, even with `auto_delete_dupes` on. A crash can hand a player back their own items, and those should not be deleted.
release
Better Anti Dupe 4.7.0
4.7.012 окт. 2026 г.74Minecraft: 1.21, 1.21.1, 1.21.2, 1.21.3, 1.21.4, 1.21.5, 1.21.6, 1.21.7, 1.21.8, 1.21.9, 1.21.10, 1.21.11bukkit, folia, paper, purpur, spigot
Что нового
## [4.7.0] - 2026-10-13
### Added
- **An API for other plugins.** Shops, crates, kits and reward plugins can now tell Better Anti-Dupe when they hand out or take away items, strip the owner mark from template copies, read a player's record, and listen to alerts, protections and automatic removal through normal Bukkit events. It works on Spigot, Paper and Folia from 1.21 up. See "Use it from your plugin" in the docs. The old `recordGrant` hook still works.
- **Stops hidden menu dupes.** Most dupes found in other plugins' menus (backpacks, ender chest plugins, shulker preview plugins, storage menus) start with a cheat client hiding the menu on the player's screen without telling the server it closed. A normal game always closes a menu before the player can mine, build, hit, drop an item, switch hotbar slot or type a command, so doing any of those with a menu still open is now stopped, the menu is closed, and staff get an alert. Normal players are not affected. Works on Paper, Folia and Spigot. New setting `prevent-hidden-menu-dupers`, on by default.
- **Stops the end portal chest dupe.** When the last eye of ender goes into a portal frame with a chest or shulker box where the portal appears, and a land claim, region or "the End is locked" plugin blocks it, the container came back while a copy of it dropped on the ground. On Paper a chest's items dropped too while the chest stayed full, and a shulker box dropped with everything still inside it, so the whole box was doubled. On Spigot the container came back empty next to the copy. The plugin now puts it all back: the container keeps its items and nothing extra is left on the ground. This is an open Paper bug on 26.3. New setting `prevent-reverted-placement-dupers`, on by default.
- **Players are checked a few seconds after they join.** This catches players who come back holding items the server should not have handed back, for example after a crash or a lag machine stopped their data from saving while the items they put away stayed in a chest. New setting `ledger.reconciliation.on_join`, on by default.
- **The console lists Paper's duping settings at startup.** If any duping glitch is switched back on in `config/paper-global.yml` (TNT, rail and carpet machines, sand through end portals, tripwire hooks), the console says so and which of them the plugin still blocks.
### Fixed
- **The owner mark is now hidden on Spigot 1.21.** Spigot before 26.1 uses different internal names, so the part that hides the mark from players' games switched itself off at startup there. It now works on Paper, Folia and Spigot alike, checked by watching what players' games actually receive.
- **A Spigot error on lecterns is guarded.** Spigot can report an empty hand differently from Paper, which could make putting a book on a lectern throw an error there.
- **Memory use on servers that run for weeks.** The plugin kept every player's balances in memory after they left. They are now released five minutes after the player logs off.
### Security
- **Alerts can no longer ping everyone in Discord.** Alert messages are sent with mentions switched off, so nothing in them can ping @everyone, @here or a role.
- **The confirm command uses the player's real name.** `on_confirm_command` now fills in the name the server has on record instead of the text typed after `/adp ledger confirm`.
### Changed
- **Built against Paper 26.3 stable.** Paper now marks 26.3 as stable, and the 26.3 download is built against it. Nothing else changes.
- **No items are taken away right after a crash.** For 30 minutes after a start that follows a crash, "Has X but ledger shows Y" alerts now also say the crash may be the cause, and the plugin does not remove items for any alert that carries that note, even with `auto_delete_dupes` on. A crash can hand a player back their own items, and those should not be deleted.
release
Better Anti Dupe 4.5.3-mc263
4.5.3-mc26312 окт. 2026 г.14Minecraft: 26.3bukkit, folia, paper, purpur, spigot
Что нового
## [4.5.3] - 2026-10-12
### Added
- **`/adp ledger accept <player> <item> [amount]`.** Records items a player got legitimately (a reward or a shop) so they stop being flagged, and clears the alert.
- **A hook for other plugins.** `BetterAntiDupe.recordGrant(player, material, amount, source)` declares items handed out outside normal play; Better End Cities uses it for elytras bought from frames.
### Changed
- **Smaller download.** The plugin carried its own copy of the database driver and the networking library, but every Paper and Spigot server already includes both, and the server's copy is always the one used. They are no longer included, so the file is about 7 MB smaller. Nothing changes in how the plugin works.
release
Better Anti Dupe 4.5.3-mc26
4.5.3-mc2612 окт. 2026 г.25Minecraft: 26.1, 26.1.1, 26.1.2, 26.2bukkit, folia, paper, purpur, spigot
Что нового
## [4.5.3] - 2026-10-12
### Added
- **`/adp ledger accept <player> <item> [amount]`.** Records items a player got legitimately (a reward or a shop) so they stop being flagged, and clears the alert.
- **A hook for other plugins.** `BetterAntiDupe.recordGrant(player, material, amount, source)` declares items handed out outside normal play; Better End Cities uses it for elytras bought from frames.
### Changed
- **Smaller download.** The plugin carried its own copy of the database driver and the networking library, but every Paper and Spigot server already includes both, and the server's copy is always the one used. They are no longer included, so the file is about 7 MB smaller. Nothing changes in how the plugin works.
release
Better Anti Dupe 4.5.3
4.5.312 окт. 2026 г.20Minecraft: 1.21, 1.21.1, 1.21.2, 1.21.3, 1.21.4, 1.21.5, 1.21.6, 1.21.7, 1.21.8, 1.21.9, 1.21.10, 1.21.11bukkit, folia, paper, purpur, spigot
Что нового
## [4.5.3] - 2026-10-12
### Added
- **`/adp ledger accept <player> <item> [amount]`.** Records items a player got legitimately (a reward or a shop) so they stop being flagged, and clears the alert.
- **A hook for other plugins.** `BetterAntiDupe.recordGrant(player, material, amount, source)` declares items handed out outside normal play; Better End Cities uses it for elytras bought from frames.
### Changed
- **Smaller download.** The plugin carried its own copy of the database driver and the networking library, but every Paper and Spigot server already includes both, and the server's copy is always the one used. They are no longer included, so the file is about 7 MB smaller. Nothing changes in how the plugin works.
beta
Better Anti Dupe 4.5.2-mc263
4.5.2-mc26320 сент. 2026 г.167Minecraft: 26.3bukkit, folia, paper, purpur, spigot
Что нового
## [4.5.2] - 2026-09-20
### Fixed
- **Rail dupers no longer work when TNT dupers are allowed.** With `prevent-tnt-dupers` off, detector rails were skipped by the rail check entirely, so anyone could dupe detector rails on purpose. Now the piston is left alone so TNT duper world eaters keep running, and the duplicated rail or carpet is removed the moment it pops out instead. TNT duper world eaters are unaffected, they just stop handing out free rails. Every kind of rail is covered, including detector rails.