Universal Trader

Universal Trader
A configurable, server-authoritative trading system for Minecraft Forge.
Universal Trader adds a powerful trading block that lets players sell eligible
items, earn copper/silver/gold coins, permanently unlock goods, and buy them
back through a searchable catalog. It is designed for survival and multiplayer
servers that want a controlled economy without relying on villagers, command
blocks, or client-trusted prices.
Features
Universal trading block
Place the Universal Trader and sell eligible items from your inventory. After an
item is successfully sold for the first time, it becomes permanently unlocked
for that world and can be purchased from the trader.
Buy prices are calculated server-side at 3× the configured sell price. The
client never supplies or controls the price.
Three-tier currency
Transactions use three denominations:
Copper coins
Silver coins
Gold coins
The wallet automatically carries currency upward at a 64:1 ratio:

64 copper = 1 silver
64 silver = 1 gold

Existing coins and new payouts are consolidated during trading. The system
also handles full inventories and offhand currency without silently deleting
value.
Search and bulk buying
The trader catalog supports case-insensitive searches by English item name or
registry ID. Search terms can contain multiple words and automatically return
the catalog to page one.
Bulk purchase buttons support:
Buy 1
Buy 8
Buy 32
Buy 64
Unavailable quantities are disabled when they exceed the item's maximum stack
size or the player's available funds. Every purchase is validated again on the
server.
Ultimate Trader
Upgrade through the normal trader by purchasing the Ultimate Trader Block
for exactly 576 gold coins. The Ultimate Trader begins with every eligible
item unlocked, while still using the same prices, safety checks, and server-side
validation.
Trader blocks cannot be sold or recursively purchased, preventing an infinite
money loop.
Configurable economy
Prices are controlled through the server's spreadsheet-compatible CSV:

config/universaltrader/prices.csv

Administrators can edit item prices, enable or disable entries, and add notes.
Explicit CSV prices take priority over generated defaults. The mod also
provides recipe-aware defaults for supported vanilla crafting, smelting,
stonecutting, and smithing chains.
Persistent multiplayer progression
Unlocks are stored per world. Transactions, balances, item IDs, prices, stack
limits, and unlock permissions are validated on the server, making the mod
suitable for dedicated servers and cooperative survival worlds.
Safety and anti-exploit protections
Universal Trader uses a conservative item policy by default. It blocks or
rejects unsafe entries such as command/debug items, technical placeholders,
trader blocks, coin items, arbitrary serialized data, and container items with
inventories when they cannot be safely normalized.
The server also protects against:
Client-supplied prices
Invalid item IDs and stack counts
Selling items that are not actually present
Buying without sufficient funds
Double-submit transaction packets
Recursive trader and currency valuation
Unsafe or unbounded item NBT
Overflow and full-inventory payout errors
Administrators can explicitly configure safe exceptions through the pricing and
server configuration files.
Compatibility
Minecraft: 26.2
Mod loader: Forge 65.1.3
Universal Trader: 0.1.3
License: MIT
Required on multiplayer: Install the same mod version on both the client
and the server.
This release is version-pinned to Minecraft 26.2 and Forge 65.1.3. It is not
intended for older Minecraft or Forge versions without a dedicated port.
Installation
Install Minecraft 26.2 with Forge 65.1.3.
Close Minecraft or stop the server.
Place universaltrader-0.1.3.jar in the mods folder.
On multiplayer, install the same JAR on both the dedicated server and each
connecting client.
Remove older Universal Trader JARs before launching.
Start the game or server and join the world.
Existing worlds, unlocks, and custom CSV prices are preserved. The mod does not
require a world reset.
Finding the recipe
The Universal Trader is crafted at a crafting table with iron blocks in the
four corners, gold blocks on the four sides, and a diamond block in the center:

Iron Block   | Gold Block   | Iron Block
Gold Block   | Diamond Block| Gold Block
Iron Block   | Gold Block   | Iron Block

Because this is a 3×3 recipe, it appears in the crafting table's recipe book,
not the 2×2 inventory crafting grid. Search the recipe book for Universal Trader.
Version 0.1.3 highlights
Added recipe-book discovery through login and ingredient advancements.
Added translated item names so the recipe is searchable.
Rebuilt wallet carry and payout handling for full inventories and offhand
currency.
Added Buy 1/8/32/64 controls with price and availability tooltips.
Added server-side validation for all bulk purchase quantities.
Added recipe-aware vanilla pricing audits and safer item filtering.
Bumped the network protocol; clients and servers must be updated together.
Support and configuration notes
The runtime reads config/universaltrader/prices.csv. Changes take effect after
the server or game is restarted, or after the supported explicit reload flow.
Keep a backup before replacing a custom price table.
For multiplayer, always update the server first and then distribute the same
JAR to clients. Do not keep multiple Universal Trader versions in the mods
folder.