Order Book

Complete reference for HyperLiquid’s order book mechanics, covering order structure, all supported order types, trigger orders (TP/SL), order relationships, and every known cancel and rejection reason.

Order Types

HyperLiquid supports the following order types:

Order Type	Description
`Limit`	Standard limit order at a specified price
`Market`	Executes immediately at the best available price
`StopMarket`	Triggers a market order when the trigger price is hit
`StopLimit`	Triggers a limit order when the trigger price is hit
`TakeProfitLimit`	Triggers a limit order at take-profit price

Two additional internal order types exist: CloseForVaultWithdrawal (used when vaults process withdrawals) and SpotDustConversion (converts small residual spot balances).

Time-in-Force

Every order carries a time-in-force (TIF) setting that determines its lifecycle:

TIF	Name	Behavior
`Gtc`	Good Till Cancel	Rests on the book until filled or cancelled
`Ioc`	Immediate or Cancel	Fills what it can immediately, cancels the rest
`Alo`	Add Liquidity Only	Post-only. Rejected if it would cross the spread and take liquidity
`FrontendMarket`	Frontend Market	Market order variant used by the frontend UI

BookOrder Structure

Each resting order on the book contains:

BookOrder {
  timestamp       — order creation time
  sz              — size (quantity)
  reduce_only     — reduce-only flag
  relationships   — parent/sibling/child order links
  cloid           — client order ID
  builder         — builder attribution
  description     — order description
}

OrderCore holds the shared core fields (price, side, asset) that are common across all order types.

Trigger Orders (TP/SL)

Trigger orders sit in a separate untriggered_orders pool until their trigger condition is met.

TriggerOrder {
  triggerPx       — trigger price threshold
  isTrigger       — identifies this as a trigger order
  isPositionTpsl  — whether this is a TP/SL attached to a position
  origSz          — original size before any partial fills
  triggered       — whether the trigger has fired
}

When the mark price crosses triggerPx, the trigger fires and the order enters the active book as its underlying type (market or limit). Position-level TP/SL orders (isPositionTpsl: true) are tied to the position itself rather than being standalone orders. They automatically cancel if the position is closed by other means.

Order Relationships

Orders can be linked through parent, sibling, and child relationships via the relationships field on BookOrder.

Relationship	Description
Parent	The originating order that spawned this one
Sibling	Linked orders where filling one cancels the other (OCO)
Child	Orders spawned by a parent (e.g., TP/SL attached to a limit fill)

One-Cancels-Other (OCO)

Sibling relationships implement OCO behavior. When one sibling order fills, all other siblings are automatically cancelled with reason siblingFilledCanceled. A common pattern: a take-profit limit and a stop-loss market order are placed as siblings. Whichever triggers first cancels the other.

Cancel and Rejection Taxonomy

HyperLiquid distinguishes between cancellations (order was on the book and removed) and rejections (order never made it onto the book).

User-Initiated Cancellations

Reason	Description
`marginCanceled`	Insufficient margin to maintain the order
`scheduledCancel`	A scheduled cancellation was triggered
`internalCancel`	Internal system cancel

System-Enforced Cancellations

Reason	Description
`perpMaxPositionCanceled`	Order would exceed maximum position size
`vaultWithdrawalCanceled`	Cancelled due to vault withdrawal processing
`openInterestCapCanceled`	Open interest cap for the asset was reached
`selfTradeCanceled`	Self-trade prevention triggered
`reduceOnlyCanceled`	Reduce-only constraint violated (position already closed or flipped)
`siblingFilledCanceled`	A sibling order filled, triggering OCO cancellation
`liquidatedCanceled`	The position was liquidated, cancelling all related orders
`outcomeSettledCanceled`	HIP-4 prediction market outcome settled

Order Rejections

Reason	Description
`tickRejected`	Price is not on a valid tick increment
`minTradeNtlRejected`	Order is below the minimum notional value
`perpMarginRejected`	Insufficient margin to place the perp order
`perpMaxPositionRejected`	Order would exceed the maximum position size
`reduceOnlyRejected`	Reduce-only order is invalid (no position to reduce)
`iocCancelRejected`	IOC order could not be filled at all
`badTriggerPxRejected`	Trigger price is invalid for the current market state
`marketOrderNoLiquidityRejected`	No liquidity available to fill the market order
`positionIncreaseAtOpenInterestCapRejected`	OI cap prevents position increase
`positionFlipAtOpenInterestCapRejected`	OI cap prevents position flip
`tooAggressiveAtOpenInterestCapRejected`	Order too aggressive near OI cap
`openInterestIncreaseRejected`	General OI increase rejected
`insufficientSpotBalanceRejected`	Not enough spot balance for the order
`oracleRejected`	Oracle price check failed
`outcomeSettledRejected`	Prediction market outcome already settled

Order Book State

The exchange maintains order book state within each perp DEX:

perp_dexs[]:
  books                 — order books per asset
  funding_tracker       — funding rate tracking
  user_balances         — per-user balance state
  book_order_keys       — index of active orders
  untriggered_orders    — trigger orders waiting for price conditions

spot_books              — separate order books for spot trading
allowed_liquidators     — addresses authorized to liquidate

Each block produces execution data including:

Output	Description
`node_trades`	Executed trades
`node_fills`	Fill events
`node_raw_book_diffs`	Raw order book changes
`node_order_statuses`	Order status updates

These outputs are available through the streaming API for real-time order book reconstruction.

TWAP Engine

HyperLiquid includes a native TWAP (Time-Weighted Average Price) engine for executing large orders over time. TWAP is used both by users directly (twapOrder/twapCancel actions) and internally by the liquidation system.

TWAP State

TwapState:
  asset           — asset being traded
  isBuy           — direction
  params          — execution parameters
  slices          — individual execution slices

TwapSchedule:
  start_time      — execution start
  duration        — total duration (max 1,440 minutes / 24 hours)
  randomize       — add jitter to slice timing (reduces predictability)

Execution

Each TWAP order is split into time-weighted slices. The WindowUpdate tracks progress:

WindowUpdate:
  size_increment  — amount to execute in current window

Slices execute as regular limit or market orders. If a slice cannot fill within its window, it carries forward to the next window.

Constraints

Parameter	Value
Maximum duration	1,440 minutes (24 hours)
Randomization	Optional jitter on slice timing
Reduce-only	Supported

TWAP orders produce node_twap_statuses in each block’s execution data, and fills appear as UserTwapSliceFills in the indexer.

TWAP is also used by the BOLE lending system for liquidations, where large positions are unwound gradually to minimize market impact. See Lending and Liquidation for details.

Signal Research

Protocol Research

DeFi Infrastructure

Infrastructure

Order Types

Time-in-Force

BookOrder Structure

Trigger Orders (TP/SL)

Order Relationships

One-Cancels-Other (OCO)

Cancel and Rejection Taxonomy

User-Initiated Cancellations

System-Enforced Cancellations

Order Rejections

Order Book State

TWAP Engine

TWAP State

Execution

Constraints

​Order Types

​Time-in-Force

​BookOrder Structure

​Trigger Orders (TP/SL)

​Order Relationships

​One-Cancels-Other (OCO)

​Cancel and Rejection Taxonomy

​User-Initiated Cancellations

​System-Enforced Cancellations

​Order Rejections

​Order Book State

​TWAP Engine

​TWAP State

​Execution

​Constraints

Order Types

Time-in-Force

BookOrder Structure

Trigger Orders (TP/SL)

Order Relationships

One-Cancels-Other (OCO)

Cancel and Rejection Taxonomy

User-Initiated Cancellations

System-Enforced Cancellations

Order Rejections

Order Book State

TWAP Engine

TWAP State

Execution

Constraints