What Auto Mode does
A trading card trades on two numbers, Upper and Lower. Picking them by hand is the hardest part of setting a card up. Set them too far apart and the spread never reaches them, so the card sits idle. Set them too close together and every trade loses money to fees. Auto Mode is a switch on the card that picks the two numbers for you. It reads where the spread on this pair has really been trading, works out how far apart Upper and Lower have to be for a trade to pay after fees, and moves them along as the market moves.
The rest of this article uses a handful of words that also appear on the card. Here is what each one means.
Spread
The difference between the price of the same coin on two exchanges, as a percentage. Every pair has two spreads, one for each direction of the trade: buy on A and sell on B, or sell on A and buy on B. The charts in this article show both.
Upper, Lower and the band
The two thresholds the card trades on. When the spread reaches Upper, the card opens a position: it buys on one exchange and sells the same amount on the other. When the spread comes back to Lower, the card closes it. A card that trades in both directions also does the reverse, opening at Lower and closing at Upper. Together the two thresholds are called the band.
Level and half-width
The level is where the spread on this pair is trading at the moment, and it sits in the middle of the band. The half-width is the distance from the level to each threshold: Upper is the level plus the half-width, Lower is the level minus it. The distance between Upper and Lower, the width, is therefore twice the half-width. The level moves with the market; the half-width changes only at a refit.
Round trip (the card calls it a cycle)
One open and the close that matches it. The distance between Upper and Lower is what a round trip earns before fees. Auto's whole job is to make that distance worth it.
Fees
Every leg of every trade pays the exchange a fee, so a round trip pays four: two to open and two to close. Auto counts a band as worth having only when a round trip clears those fees with room to spare.
Delay
A card setting. The spread has to stay past a threshold for this long before the card trades. With a delay of 500 ms, a spread that jumps past Upper for 200 ms and drops back does not count. The delay filters out blips the card could never have caught.
Order book
The list of buy and sell orders waiting on an exchange, with the amount available at each price. The price you actually get depends on how much is waiting there, so the spread for a $50 order and for a $5,000 order on the same pair can differ. Auto sizes the band on order-book prices at your order size, not on the headline quote.
Lookback
How far back Auto looks when it measures where the spread has been. Auto picks the lookback itself, between half an hour and four hours, depending on how much has happened on the pair.
Refit
The moment, once every five minutes, when Auto measures the pair again and decides how wide the band should be. Between refits the band keeps its width and only slides along with the spread.
The chart below is the real algorithm, not a drawing. We ran it tick by tick over four hours of a live pair. The band on the chart is the one Auto set, and it moves as the spread moves. Each solid dot is a moment the spread crossed the band and opened a position. Each hollow dot is a crossing that closed one.
One refit, step by step
Every five minutes Auto runs the same six steps and comes out with a band. The stepper below runs them on a sample pair, one tab per step, and each tab adds its own layer to the picture. Read it once to see the shape of the mechanism. The sections after it explain where the numbers come from and why each step is there.
Where the history comes from
Auto needs a record of where the spread has been, and three such records exist. They are not equally good, and a band is never better than the record it was sized on. Five words first, because the rest of this section is built out of them.
Tick
One update from an exchange: a new best price, or a new amount waiting at that price. A busy pair sends several every second, and no record stores them one by one.
Bucket
A fixed slice of time that many ticks are reduced to one value for. A history in five-second buckets holds one number per five seconds instead of thousands of ticks. The number Auto keeps is not an average of the slice: it is the spread that held for the whole of your delay inside it.
Quote feed
The cheapest record we keep, and the roughest: the single best price on each exchange, saved every ten seconds, for every pair on the platform. Ten seconds is long enough for a spread to appear and vanish unseen, and the two exchanges are not saved at the same instant, so the feed also shows spreads that never existed at the same time.
Recorded order books
Order books we record in full, not just the best price, in two-second buckets, for every pair the scanner covers. Because the whole book is there, a trade can be priced at your order size, which is what a card needs while it has no history of its own.
The card's own record
What a running card writes down for itself: the books it is actually trading on, at your order size, in five-second buckets, up to four hours back. It is the best of the three because it is the card's own experience rather than an approximation of it, and it is saved, so restarting the card does not lose it.
Auto reads the best of the three it has, in this order.
- 1
First hour: our recorded order books
A card that has just opened has no history of its own. For that first hour Auto reads the order-book history we record for every pair the scanner covers. Those are real books, recorded at the order size closest to yours and at a hold time that matches your delay, so the very first band is already sized on prices your card could have traded.
- 2
After an hour: the card's own record
From the moment the card opens it watches every tick of the order books it trades on, at your order size, and writes one value per five-second bucket: the spread that held for the whole of your delay, not the best instant inside those five seconds. After sixty minutes that record is the only thing Auto reads, and restarting the card does not lose it.
- 3
If neither exists: the quote feed
Some pairs are not covered by that recording. A card on such a pair spends its first hour on the quote feed. It still gets a band, only a rougher one, until its own record has an hour of data.
Why the delay matters here: a card with a 500 ms delay trades only on a spread that stayed past the threshold for 500 ms. A spike that lasts 200 ms is real on a chart, but that card could never have traded it. Auto builds the band from the spreads that held for your delay, so any threshold it sets is one the card can actually reach.
What Auto reads, hour by hour
Auto reads the order-book history we record: at the order size closest to yours, held for a time that matches your delay.
Auto reads the card's own record: every tick of the order books it trades on, at your order size, keeping only the spread that held for your delay.
Auto falls back to the quote feed: one best price per exchange every 10 seconds. It is the roughest picture there is, so it is the last resort.
Every tick, against what held for the delay
Illustration: 20 s at 50 ms, delay 500 msThree spikes cross the band edge, and none of them lasts the 500 ms delay, so the card could not have traded any of them. The one hold lasts 1.2 s and could be traded. On both order-book sources Auto reads only the blue line, the spread that held, so the band it sets is one the card can reach. The quote feed has no such filter, which is why it is the last resort.
How the band is built
Your card trades on Upper and Lower. Auto does not set those two directly. It sets a centre, called the level, and a distance out from that centre, called the half-width, and Upper and Lower fall out of the pair.
Upper = level + half · Lower = level − half- level
- Where the spread is trading now. Auto takes the midpoint of the two spreads and smooths it, so that recent readings count most and older ones fade out over about 15 minutes, updated every 15 seconds. The level follows a drifting pair without chasing every blip, and on a fast move it lags by about 1%. If it ends up outside the range the market is actually trading in, the next refit moves it back.
- half
- Half the distance a round trip has to cover. Auto chooses it again at every refit: it tries fourteen candidate widths on the lookback, simulates the band each one would give, and keeps the one with the best score. The score is the number of round trips multiplied by what each round trip earns after fees. If two widths score within 10% of each other, the narrower one wins, because it trades more often.
- floor
- The narrowest the band may get. A round trip is never allowed to earn less than 1.6 times the fees it pays, so the half-width never drops below 0.8 times those fees. If you set Min Spread higher than that, Min Spread becomes the floor instead.
While Auto is on, Upper and Lower are shown on the card but cannot be edited. The band line under the Auto switch shows the two numbers they are built from.
Read it the other way round and the band gives the two numbers back: the level sits midway between Upper and Lower, and the gap between them, the width, is twice the half-width. The level and the half-width run on different clocks, which is why the band often slides without changing shape. Every cadence in Auto is listed at the end of this section.
Auto also chooses how far back to look. It tries 30, 60, 120 and 240 minutes, shortest first, and stops at the first lookback where the best band it can find would have completed at least 15 round trips. A busy pair is measured on its last half hour, so the band reacts quickly. A quiet pair is measured on four hours, so a lull does not shrink the band down to noise.
Every 5 seconds
The card adds one value to its own record. Nothing about the band changes: the card is collecting evidence, not deciding anything.
Every 15 seconds
The level is recalculated and the whole band slides to sit around it. Upper and Lower move by the same amount, so the distance between them is untouched.
Every 5 minutes, the refit
Auto measures the pair again and picks the half-width and the lookback. This is the only moment the band changes shape, and the only moment a parked band arms or an armed band parks.
Once, an hour after the card opens
The card's own record takes over from our recorded order books as the only source Auto reads. This happens once per card, not on a repeating schedule.
30 minutes to 4 hours, the lookback
How far back each refit measures. It is not a cadence of its own: the length is chosen again at every refit, from how much has happened on the pair.
The smallest distance between Upper and Lower you are willing to accept. Auto uses whichever is larger, this value or 1.6 times the fees. Leave it at 0 unless you want the card to hold out for more than the pair is offering.
| Setting | Default | Range | What it does |
|---|---|---|---|
| Min Spread | 0 | 0–10% | The smallest distance between Upper and Lower you are willing to accept. Auto uses whichever is larger, this value or 1.6 times the fees. Leave it at 0 unless you want the card to hold out for more than the pair is offering. |
The band, piece by piece
The midpoint of the two spreads, smoothed so that recent readings count most and older ones fade out over about 15 minutes. It follows a drifting pair and lags a fast move by about 1%. If it ends up outside the range the market still trades in, the next refit moves it back.
Auto simulates fourteen candidate widths on the lookback and keeps the one with the best score: round trips multiplied by what each earns after fees. Two widths within 10% of each other go to the narrower one. The round trip a width leaves is never below 1.6 times the fees, or below Min Spread if that is higher.
The shortest of 30, 60, 120 and 240 minutes that holds at least 15 completed round trips.
Three situations, one rule
The same mechanism gives different bands on different pairs, and that difference is the point of Auto. Each of the three replays below shows six hours of a live pair. Switch between them to see how the band reacts.
The level drifts
When the whole spread moves to a new range, the level follows within minutes and the width stays at what round trips pay. A fixed band would have been crossed once on the way out and then never again.
Quiet, then loud
When a pair starts moving more, a short lookback is enough to hold 15 round trips, so Auto measures on recent data and the band widens with the evidence. When the pair calms down again, the lookback stretches and the band settles.
One-sided order book: parked
On some pairs the two spreads never sit at the same distance from the level, because one exchange's order book is far wider than the other's. A position opened on one side could not be closed on the other. Instead of arming such a band, Auto parks it beyond anything the lookback has shown and checks again every five minutes. The card says so under the Auto switch.
What you see on the card
The band line
Shown under the Auto switch as ±half-width at level: the two numbers Upper and Lower are built from. A negative level puts the band below zero. That is normal on a pair where one exchange is consistently priced above the other.
Cycles in the lookback
How many complete round trips this exact band would have made over the history it was sized on. It is a simulation on that history, not a count of trades the card took. It answers a question the chart cannot: a threshold that sits above most of the line can still be crossed dozens of times by short moves, and this number tells you whether it was.
Parked
One exchange's order book is one-sided, and the band is waiting at the edge of what the lookback has seen. Nothing is broken: the card is refusing a position it could not close.
New entries paused
Same verdict as parked, but a position is already open. A threshold beyond the window's range is no exit, so for that position Auto keeps both thresholds on the band around the spread and opens nothing new. Closing works as usual. Entries come back on their own once the market reaches both sides again.
Band held
The band was sized, but the card is not trading on it. There are two possible reasons. Either the order book on one leg keeps flipping between two prices: that settles on its own, and the card arms the band again by itself. Or the exchange has restricted that contract for your key: that does not clear on its own. Open the key settings, find the contract under Venue restrictions and press Clear, or the card keeps holding. Closing a position works either way.
Telegram
When a refit moves a threshold by more than 3%, you get a short Telegram message with the new thresholds and the distance between them. If the band was parked, the message says why. You get at most one such message per card per hour, so the quiet refits every five minutes do not fill your chat. A change you make yourself always sends a message.
Min Spread is the only number left to set in Auto, and it sits behind the advanced link on purpose. The band comes from the pair's own economics, so the lookback and the old Adjustment setting became numbers nobody should have to pick. Min Spread stays for the cases that derivation cannot cover.
On the card
- 1What Auto is doing now and when it last recalculated. The thresholds themselves are the Upper and Lower columns above, read-only while Auto is on.
- 2How many round trips these exact thresholds would have completed over the lookback they were sized on. A low count means a quiet pair, not a broken card.
- 3Thresholds around the current spread would open a position here that never closes, so both wait past the recent range. Auto checks again every five minutes.
The rules that keep it safe
Fees first
A round trip is never allowed to earn less than 1.6 times the fees it pays. Which fee rate? Once your API key has made 50 fills on linear contracts in the last week, Auto uses the rate the exchange actually charged on them rather than the number typed on the key, so an exchange that charges more than it advertises is priced in. Until then, and on inverse contracts, the number on the key stands.
Both thresholds within reach
Before arming a band, Auto checks how far each of the two spreads reached during the lookback, using its 99.5th percentile: the level it reached on all but the rarest half-percent of ticks. It compares that reach with the cheapest band that could still pay. If one spread reaches past that line and the other does not, the band would open and never close, so Auto parks it instead. If both reach past it, or neither does, there is no trap and the band is armed.
Sized on what could have fired
The card's own record keeps the spread that held for your delay, not every flicker. A band sized on flickers would promise trades the delay check would never let through. This one cannot.
Parked, not stuck
A one-sided book gets a parked band instead of an open position with no exit. The next refit, five minutes later, runs the reach test again and arms a real band as soon as both spreads reach their thresholds. A parked band can still trade: a move bigger than anything in the lookback crosses it, and that is the only kind of move it is meant for.
One refit at a time
If a refit takes longer than usual, the next one waits for it, so the band changes in one step and never two at once. The refit also runs off the trading path, so it never delays an order.
Common questions
Upper looks unreachable on my chart. Why?
The chart under the card draws ticker quotes sampled every few seconds. The band is sized on something else: the spread that held for your delay, in the order book, at your order size, over a lookback that may be longer than what the chart shows. The number to check is the cycle count under the Auto switch. Above zero means this exact band was crossed that many times in its lookback.
The band changed about an hour after I opened the card.
That is the switch from our recorded order books to the card's own record. Both are order-book data at your size, but the card's record is exactly what the card can trade, so the band usually tightens a little at that moment.
Can I still set Upper and Lower myself?
Yes. Switch Auto off and the two fields become editable again. They keep the values Auto set last, so you start from a band that was known to work. Min Spread and the other advanced settings stay yours while Auto is on.
Nothing traded for an hour, and the band looks fine.
Check the cycle count first. A band with only a few cycles in a four-hour lookback is on a quiet pair, and a quiet pair stays quiet with Auto on. Auto sizes the band; it does not create spread.