Aster

Aster is a Decentralized Perpetuals Exchange Designed for Reduce-Only Exit Control

Aster is an order-book perpetual position workflow in Pro mode: choose a market, margin mode, leverage, and side; read the filled position; adjust its size; then submit an opposite-side reduce-only order. The modifier caps execution at the existing position, so an oversized exit does not create new exposure after the original position reaches zero.

The sequence matters because fees, margin, trigger prices, and position mode affect different stages. This brief follows one position from entry through status changes and final closure, with the trade-offs attached to each control.

Entry and exit costs across the position lifecycle

Trading costs on Aster attach to filled notional at entry and exit, while funding belongs only to the period the perpetual position remains open.

Aster sets the maker fee at 0% and the taker fee at 0.04% for USDT perpetual contracts, while USD1 perpetuals use 0% maker and 0.005% taker fees. Paying trading fees with ASTER reduces the fee amount by 5% when the perp wallet holds the token. Both entry and exit fees use filled nominal value, calculated as contracts multiplied by execution price; leverage changes required margin, not fee notional. A post-only limit exit receives maker treatment only when it rests on the order book. Funding uses a separate schedule and never changes the maker or taker classification of a fill.

Worked example. Every changing input is hypothetical: a 0.10 BTC BTCUSDT taker entry at 60,000 USDT, a 0.04 BTC maker reduce-only fill at 63,000, and a 0.06 BTC taker close at 62,500. Entry notional is 6000 USDT, producing a 2.40 USDT fee. The first exit leaves 0.06 BTC and costs 0 USDT at the maker rate. Final-exit notional is 3750 USDT, producing a 1.50 USDT fee. The concrete result is zero position size and 3.90 USDT in trading fees before any 5% token discount or funding transfer. Realized price movement is excluded because it is not a trading fee.

Account settings before the first order

Account configuration on Aster fixes how opposite orders, collateral, and losses interact, so set position mode, collateral mode, margin mode, and leverage before entry.

Pro mode operates across four network contexts: BNB Chain, Ethereum, Arbitrum, and Solana. MetaMask and Trust Wallet provide familiar EVM access, while Phantom and Solflare serve Solana users. The chosen network determines where collateral resides; reduce-only logic stays attached to the trading position rather than the wallet brand.

Two position modes separate one-way net exposure from simultaneous long and short slots. Two collateral modes separate USDT-only single-asset accounting from multi-asset cross accounting, and two margin modes separate cross from isolated risk. Multi-asset mode uses cross margin. Position mode and margin mode must be chosen before the relevant position or open order exists.

Those locks make configuration part of the trade lifecycle, not a cosmetic preference.

Opening a position from one concrete order

Opening an Aster position begins with one buy or sell instruction whose fill establishes direction, size, average entry price, and initial margin consumption.

The order tab exposes six core types: market, limit, stop-limit, stop-market, trailing-stop, and post-only. Market orders consume available book liquidity immediately. Limit orders wait for the selected price or better. Stop orders activate after a trigger, while post-only rejects an instruction which would match immediately. An accepted fill creates or enlarges the position only when the order is not constrained to reduce existing exposure.

Market and limit entries

A market entry prioritizes completion over exact price, so depth and slippage shape the average fill. A limit entry prioritizes price, yet an untouched or partially matched order leaves no position or a smaller position than requested.

Initial margin and order direction

Initial margin equals position size multiplied by mark price, divided by leverage. The platform applies one direction value to a long order and minus one to a short when calculating any open loss.

Cross margin

Cross margin shares available balance across open positions. Gains elsewhere support the account, while one losing position draws on the same pool of collateral.

Isolated margin

Isolated margin assigns collateral to one position. Adding or removing isolated margin changes its buffer without changing contract quantity or average entry price.

What does the position panel show after a fill?

The Aster position panel shows the contract, direction, size, entry price, mark price, leverage, liquidation price, unrealized profit or loss, and attached margin figures.

A filled order moves attention from order status to position status. Used margin shows collateral committed, available balance shows capacity left for orders or transfers, and the mark price drives unrealized profit or loss. Aster expresses auto-deleveraging priority with four bars; the API represents five quantile values from 0 through 4 and refreshes them every 30 seconds. Those fields describe account state, while order history records the executed quantity and average price behind it.

The decisive lifecycle check is position size: a nonzero value means exposure remains, even when another exit order is open.

Changing size without changing direction

Position size on Aster changes through another filled order, while adding or removing isolated margin changes collateral without buying or selling the perpetual contract.

A same-direction fill adds contracts and recalculates average entry price. An opposite-direction fill reduces the net amount in one-way mode; without reduce-only protection, excess quantity proceeds into the other direction. A partial exit should therefore use the opposite side, a quantity no larger than intended, and the reduce-only modifier. This keeps a routine scale-out separate from a directional reversal.

Margin adjustment does not rewrite entry price or position size; it changes the collateral buffer and displayed liquidation price.

Reduce-only orders as the closing control

The reduce-only modifier on Aster limits an opposite-side order to shrinking the existing position, making it the central control for partial and final exits.

A long position closes through sell fills, and a short position closes through buy fills. Reduce-only prevents the instruction from adding contracts or establishing the opposite position after the remaining quantity reaches zero. The order still follows its selected type, price, trigger, and time-in-force rules.

Direction still matters.

A buy marked reduce-only cannot shrink an existing long, because a long requires a sell to unwind. The same rule reverses for a short. Check the side, requested quantity, and reduce-only state together before submission, then read executed quantity rather than original quantity after a partial fill. That sequence leaves the BTCUSDT position aligned with the intended remainder.

Time-in-force choices for partial exits

Time-in-force on Aster determines whether a reduce-only limit order waits, fills partially, or requires immediate full execution after reaching the order book.

Three settings cover the main choices. Good Till Cancelled keeps the order live until filling or cancellation. Immediate or Cancel takes available quantity at the limit and cancels the remainder. Fill or Kill demands the entire quantity immediately and cancels everything when full execution is unavailable. A partial scale-out tolerates IOC behavior; a single all-or-none exit expresses FOK behavior.

Post-only is a separate modifier: it rejects an order which would take liquidity, while reduce-only constrains the position effect. Combining them seeks a maker exit without permitting reversal, but price movement may leave the BTCUSDT order resting and the position open, as documented in Aster withdrawals.

Mark price and last price trigger paths

Trigger selection on Aster chooses between mark price and last price for take-profit and stop-loss instructions, creating two distinct paths into an exit order.

Said differently, Aster derives mark price from the median of three values: a funding-adjusted price index, the index plus a 5-minute moving average, and the contract price. The moving-average component samples once per minute across five minutes. A source deviating by more than 5% from the source median receives zero weight under the documented protection rule. Last price instead records the newest order-book trade, so the two references may reach the same trigger at different moments. This separation keeps trigger behavior distinct from the price used to value the still-open position in the account panel.

Trigger choice controls activation; reduce-only controls what the resulting order may do to the position.

Closing the final remainder and confirming zero

Final closure on Aster requires a filled reduce-only order and a position size of zero, followed by review of any surviving conditional exit instructions.

A market close prioritizes immediate execution and pays taker treatment against available depth. A resting limit close controls price and receives maker treatment when it adds liquidity, but it remains pending until matched. After any fill, compare requested quantity with executed quantity, read the remaining position amount, and check realized profit or loss, trading fee, and funding entries in account history.

Zero size is the operational finish line. Cancel any unneeded take-profit, stop-loss, trailing-stop, or limit instructions still shown under open orders, then confirm the contract no longer appears as an active position.

How does hedge mode change a closing order?

Hedge mode on Aster keeps one long and one short slot for the same contract, so a close must identify the specific position side it reduces.

One-way mode maintains one net position and supports the reduce-only flag directly. Hedge mode preserves two directional slots, and Aster's API requires LONG or SHORT in the positionSide field rather than reduceOnly on a new order. A sell closes the LONG slot, while a buy closes the SHORT slot when submitted as a closing instruction. Mixing those fields produces a different lifecycle than a one-way net exit.

Position mode cannot change while open positions or open orders remain. Close both hedge slots and clear their orders before switching back to one-way mode.

API fields behind an automated close

Automated closure through the Aster API uses symbol, side, quantity, and order type, plus reduceOnly set to true for a one-way position. A new-order request carries weight 1, batch submission accepts at most 5 orders, and a client order identifier permits 1 to 36 valid characters. HMAC SHA-256 authenticates private requests. A WebSocket user stream supplies timely order and account updates; automation should finish by reading the position record and confirming an amount of zero.

Aster: the short answers