Overview

Shell Accumulator is an on-chain exchange system on the GOSH network that lets users trade ECC SHELL for eccUSDC at a fixed rate of 100 SHELL = 1 eccUSDC.

Buying SHELL, step by step: Exchange eccUSDC for SHELL via Accumulator.

The pages below describe how the system is built; that one is how you use it.

What it does

Sellers deposit SHELL into fixed-size lots (denominated in 1, 10, 100, or 1000 eccUSDC). Buyers deposit eccUSDC and receive SHELL — first matched against existing seller lots in FIFO order, then minted if no sellers are available. When a buyer's eccUSDC matches a seller's lot, the seller can claim their eccUSDC payout.

A separate token, NACKL, can be redeemed (burned) against the "free reserve" — the eccUSDC balance not owed to any seller.

Tokens (ECC IDs)

Token	ECC ID	Decimals	Role
NACKL	1	9 (nano)	Value storage and staking
SHELL	2	9 (nano)	Utility token, sold by sellers
eccUSDC	3	6 (micro)	Stablecoin, deposited by buyers

All token amounts in the contracts use their smallest unit: nanoSHELL, nanoNACKL, microeccUSDC.

Contracts

Contract	Source	Role
ShellAccumulatorRootUSDC	contracts/accumulator/ShellAccumulatorRootUSDC.sol	The central Accumulator contract: accepts eccUSDC, SHELL, and NACKL, manages FIFO seller queues, sells SHELL instantly, and handles eccUSDC payouts for claims and burn.
ShellSellOrderLot	contracts/accumulator/ShellSellOrderLot.sol	One per seller position; carries claim metadata
AccumulatorLib	contracts/accumulator/libraries/AccumulatorLib.sol	Deterministic address derivation for lots
Exchange	contracts/exchange/Exchange.sol	TIP-3 USDC bridge and admin mint entry point

Key design decisions

Fixed denominations.

Lots come in exactly 4 sizes: 1, 10, 100, 1000 eccUSDC. There are no partial lots. A 154 eccUSDC buy matches 1×100 + 5×10 + 4×1 lots.

FIFO guarantee.

Each denomination has its own queue. Lots are matched strictly in order of creation — earlier sellers get paid first.

Deterministic lot addresses.

Lot contract addresses are derived from (code, root, denom, orderId) using AccumulatorLib. This means the Root can verify any caller claiming to be a lot by recomputing the expected address, without storing a mapping.

Directed events.

Events are emitted to hardcoded external addresses (610–617) so that off-chain backends can subscribe to specific event streams without parsing all contract messages. See Events for the full list.