DarkBook

An OTC block-trading venue on Sui.

Off-chain intent matching · on-chain atomic settlement · DeepBook V3 liquidity fallback.

Live app →

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Overview

DarkBook is an on-chain OTC venue on Sui for executing large-block trades without market impact. Traders submit intents specifying side, amount, and a minimum acceptable price. A matching engine pairs opposing intents and settles them atomically through a Move vault — both sides clear in a single transaction at a fair mid-price, with no slippage.

When no counterparty match is found within 120 seconds, the unmatched intent is routed automatically to DeepBook V3, Sui's native central limit order book, so every order has a path to execution.

No market impact: large blocks clear in a single atomic settlement at a fair mid-price, rather than resting on a public book where they move the market. Unmatched size routes to DeepBook V3 instead of splitting the trade.

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How it works

DarkBook has three layers: a Move settlement vault, an off-chain matching engine, and a DeepBook V3 fallback.

1 · Settlement vault (Move)

A shared Sui object that custodies SUI in a single pooled balance and tracks each participant's claim in a table. Settlement moves balances between counterparties as bookkeeping; participants withdraw their settled balance from the shared pool. This pooled design is what allows a settled counterparty to withdraw value that originated from the other side of the trade.

Function	Description
deposit_and_intent	Locks SUI into the pool, records the depositor's balance, creates a shared Intent object, emits Deposited
settle	Matcher-only. Adjusts buyer/seller balances atomically at the agreed price. Emits Settled
cancel	Returns an unmatched depositor's balance from the pool
withdraw	Withdraws a settled balance from the pool to the owner. Emits Withdrawn

Intent objects are shared, so the matcher can reference them inside a programmable transaction block (PTB) without owning them.

2 · Intent matching engine (Node.js / Express)

A stateless service that pairs opposing intents.

1. Validates the request and creates an intent record.
2. Scans pending intents for a price overlap (buyer.min_price >= seller.min_price).
3. On a match: builds a PTB calling vault::settle, signs as the matcher, executes, and returns the digest.
4. On no match: queues the intent with a 120-second fallback timer. If it stays unmatched, it routes to DeepBook V3.

3 · DeepBook V3 fallback

Unmatched intents are filled on DeepBook V3 through the matcher's BalanceManager. The route is side-aware:

• Sell — deposits SUI (plus a small fee buffer), places a market sell, and sweeps both resulting coins back to the trader.
• Buy — deposits DBUSDC sized to the order with a slippage buffer, places a market buy, and sweeps the filled SUI plus any unused buffer back to the trader.

Buffers exist because DeepBook charges the taker fee from the input asset when not paying in DEEP; any unused remainder is always returned, so the trader never overpays. The BalanceManager is fully swept after each route, so no residual balance is left between trades.

The engine also serves live DeepBook market data — prices, order book, and recent trades — sourced from the DeepBook V3 Indexer across active pairs including SUI/DBUSDC, DEEP/SUI, DEEP/DBUSDC, WAL/SUI, WAL/DBUSDC, and DBUSDT/DBUSDC. On-chain execution is currently verified on SUI/DBUSDC.

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Trade lifecycle

1. Buyer calls deposit_and_intent (side = 0). The vault pools their SUI and records their balance.
2. Seller calls deposit_and_intent (side = 1). Same.
3. Both submit their on-chain Intent IDs to POST /intent. The engine detects the price overlap and computes the agreed mid price.
4. The matcher calls settle; balances adjust atomically and a Settled event is emitted.
5. Each party withdraws their settled balance from the pool.
6. If no peer match appears within 120 seconds, the intent routes to DeepBook V3 and fills on-chain.

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Deployment (Sui Testnet)

Object	Address
Package ID	0xd2ceb60740725ec1b962511378c8701b54173354a133175ec7663160af925eb5
Vault (shared)	0xadddb5525c4583602945353a143e7a19ce687b22cede1563b32f8cdfb45df160
Vault initial version	909793926
BalanceManager	0xe36aafc2602269e5641833c7261acaf3a655b8f98d535d446adcfffb09809ebd

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API reference

Intent endpoints

Endpoint	Method	Description
/intent	POST	Submit an intent. Returns matched with a digest, or pending with a fallback timer
/intents	GET	All pending intents with their DeepBook fallback countdown
/intent/:id	GET	Status and time remaining for one intent
/routing/:id	GET	DeepBook routing result for an intent (by UUID or on-chain ID)
/health	GET	Service status and matcher address

DeepBook endpoints

Endpoint	Method	Description
/deepbook/pairs	GET	Active pairs with live price, bid, ask, and volume
/deepbook/price?pool=	GET	Live price (default SUI_DBUSDC)
/deepbook/orderbook?pool=&depth=	GET	Bid/ask levels (default depth 10)
/deepbook/trades?pool=	GET	Recent trades

POST /intent body

Field	Description
owner	Sui wallet address
side	0 = buy, 1 = sell
amount	MIST (1 SUI = 1,000,000,000)
min_price	scaled by 1e6 (3500000 = $3.50)
onChainId	Intent shared object ID from the deposit transaction
initialSharedVersion	from the deposit transaction output

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Local setup

Prerequisites: Sui CLI, Node.js 20+, and a funded Sui testnet wallet.

Clone and install the backend:

git clone https://github.com/addnad/darkbook
cd darkbook/backend
npm install

Create backend/.env:

PORT=3001
SUI_NETWORK=testnet
PACKAGE_ID=0xd2ceb60740725ec1b962511378c8701b54173354a133175ec7663160af925eb5
VAULT_ID=0xadddb5525c4583602945353a143e7a19ce687b22cede1563b32f8cdfb45df160
VAULT_INITIAL_VERSION=909793926
BALANCE_MANAGER_ID=0xe36aafc2602269e5641833c7261acaf3a655b8f98d535d446adcfffb09809ebd
BALANCE_MANAGER_VERSION=885018947
MATCHER_PRIVATE_KEY=suiprivkey1...

Run the engine:

node index.js

Run the frontend:

cd ../frontend
npm install
npm run dev

Deploying your own vault

cd contracts
sui client switch --env testnet
sui client publish --gas-budget 50000000

Update PACKAGE_ID, VAULT_ID, and VAULT_INITIAL_VERSION in .env with the published output. The matcher wallet also needs a DeepBook BalanceManager; set BALANCE_MANAGER_ID and BALANCE_MANAGER_VERSION accordingly.

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Tech stack

Layer	Technology
Smart contract	Move (Sui 2024 edition)
Intent engine	Node.js + Express
Sui SDK	@mysten/sui (engine 1.45 · frontend 2.18)
DeepBook	@mysten/deepbook-v3 1.5 + DeepBook V3 Indexer
Frontend	Next.js 14 · React 18 · TypeScript · @mysten/dapp-kit 1.0
Deployment	Render (engine) · Vercel (frontend)

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License

MIT