Charm and the CHEX lens

Start with the one idea

Gamma tells you what dealers do when price moves.

Vanna tells you what dealers do when volatility moves.

Charm tells you what dealers do when nothing moves and time simply passes.

That is the whole distinction. The first two lenses react to the market. Charm reacts to the calendar. It is the only one that keeps working while you are asleep.

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What delta drift actually means

Every option has a delta, which is just how much it behaves like the stock. A call with a 0.50 delta gains about fifty cents when the stock gains a dollar. A call with a 0.05 delta barely notices.

Here is the part most people never think about. Delta drifts, even while the stock stands still.

Picture a call struck ten dollars above the current price with three weeks left. It has a real chance of finishing in the money, so it carries some delta. Now let two weeks pass with the stock going absolutely nowhere. That same call is now ten dollars out of the money with three days left. Its chance of finishing in the money has collapsed, so its delta has collapsed with it.

Nothing happened. The stock stood still. But the option is a different instrument than it was, because the clock ran.

Charm is the measurement of that drift. It is how much delta changes per day, from the passage of time alone.

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Why that becomes a flow

Dealers want a flat book. When they sell you an option, they hedge it, and the size of that hedge is set by the delta.

So when delta drifts, the hedge is wrong. Nobody traded and the market stood still; yesterday's hedge was simply sized for yesterday's delta.

They have to correct it. That correction is a real order, hitting a real market, and it happens on the quietest day of the year. Multiply it across an entire options chain and you have a flow that exists purely because time passed.

CHEX is our attempt to measure the size and direction of that flow.

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The three things that make charm different

It is largest near expiry. A thirty day option has modest charm. A same-day option has enormous charm. An at-the-money call can go from fifty delta to almost nothing between lunch and the close, and every step of that has to be hedged. This is why charm matters most in the afternoon of an expiration day and barely registers on a six month contract.

It accrues while the market is closed. Gamma needs price to move, and the tape is shut overnight. Charm carries on regardless. Friday afternoon to Monday morning is three days of decay, and dealers arrive on Monday already needing to adjust. If you hold positions overnight or over a weekend, this is happening to you whether you watch it or not.

It intensifies into monthly expiration. The week into a monthly is when charm and gamma start working on the same strikes at the same time, which is a large part of why price so often gets sticky near heavy open interest in that window.

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How to read the CHEX board

Switch the lens to CHEX and the ladder redraws. Same strikes, different sizes, because it is now measuring a different thing.

Size tells you where time is doing the most work. The largest values mark the strikes where delta is draining fastest, which is where the hedging correction is biggest.

Sign tells you which way that correction leans. Positive means the decay produces net selling pressure as deltas fade. Negative means it produces buying.

Distance from expiry sets the whole scale. On a same-day chain the numbers will be large. On anything past a month they will be small, and that is correct rather than a fault. If CHEX looks quiet on a long-dated expiry, it is quiet.

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What it adds to a read you already have

This is the part worth sitting with, because charm sits alongside the other two rather than replacing either. It answers a question they leave open, and it is a question most traders think to ask only afterwards.

Gamma answers: what happens if price moves. Vanna answers: what happens if volatility moves. Charm answers: what happens if nothing moves.

Now consider how much of your time is spent in that third situation. Most sessions drift. Most hours go sideways. A great deal of trading is sitting in stillness, waiting, wondering whether the quiet means something is building or the board is simply empty. Every tool you own is built to describe movement. Charm describes the stillness itself, and stillness is where you spend most of your life as a trader.

Five specific things it puts on the board that were absent before.

It gives the afternoon a reason. You have watched price go magnetic near a big strike in the last two hours of an expiration day. You have probably called it pinning. Charm is a large part of the mechanism, and now you can see its size rather than infer it from behaviour. Naming the force tells you whether the condition that produces that behaviour is actually present today, or whether you are pattern-matching on a memory. Where price goes stays a separate question.

It turns overnight from a blank into a description. Right now, when you hold something through the night, the hours between the close and the open are simply unknown. Charm runs through all of them. Where you open stays anyone's guess, and anyone who says otherwise is selling something. What it does tell you is which direction the hedging pressure has been accumulating while the screen was dark, which is a description where today you have a blank.

It separates two kinds of patience. Waiting through a quiet tape with heavy charm is a different situation from waiting through a quiet tape with light charm. In the first, forces are actively reshaping positioning while price stands still. In the second, the board is genuinely idle. They look identical on a chart, and knowing which one you are in is exactly the sort of context that changes how long you are willing to sit.

It gives you a second opinion on the same board. When gamma says the book leans absorbing and charm says decay leans to selling, those are two real forces pointing different ways on the same strikes. That disagreement is information. It is the same instinct you already use when you want your fibs, your moving average and your structure to agree before you act. This gives the options half of that stack a third voice instead of two.

And it makes the calendar visible. You already know that the week into a monthly expiration feels different from the week after. Charm is part of why. It grows as expiry approaches and then vanishes with the contracts, so where you are in the cycle is a real, measurable condition rather than a vague sense that "it is OPEX week."

The layer it adds, in one sentence: you stop reading only what the market is doing, and start also reading what the clock is doing to it.

All of it is one more thing you can see before you decide, which is the whole of Compass's job.

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Three things to hold straight

It is a current rather than a level. This is the most important thing to understand, and the easiest to get wrong because the ladder looks the same.

Gamma creates something that behaves like a wall. Price approaches, dealer hedging pushes back, and you get a zone worth watching. Charm works differently: it produces a drift. A large CHEX value at a strike means the hedging around that strike is being reshaped by the clock, and price runs through it as easily as through anywhere else.

So read CHEX differently from GEX. A big charm number belongs in your read as weather rather than as support or resistance: a background current rather than a rock in the river.

It is context rather than a signal. Direction sits outside it, as it sits outside everything in Compass.

It rests on the same assumption everything else does. Charm exposure, like gamma and vanna exposure, requires assuming which side of each contract the dealer is on. Open interest leaves that off the record. We apply the conventional reading once and publish the arithmetic, and it remains an assumption.

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When it is worth looking

Late on an expiration day. Charm is at its largest and it is competing with gamma around the strikes with the most open interest. If price feels magnetically stuck in the last two hours, this is part of the reason.

Before you hold something overnight. The decay runs while you sleep. Knowing whether it leans toward buying or selling is context, and context you have been going without.

Going into a Friday, and especially into a monthly. Three days of weekend decay lands at once. The monthly is where it is largest.

When you are trying to work out why nothing is happening. A quiet tape with heavy charm is a different situation from a quiet tape with light charm.

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A session, walked through

Numbers below are illustrative. The point is the shape of the reading, not the figures.

SPY, an expiration Friday. Spot opens around 771. The heaviest strike on the board is 770.

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9:45. You look at GEX first, as you should.

The map says what it always says: 770 is the largest concentration near price, the book leans absorbing, price is sitting just above it. That is your read for the session and nothing here changes it.

Out of habit you flick to CHEX. It is small. A few hundred thousand at the biggest strikes, noise compared to the gamma board.

What that tells you: the clock is driving very little yet. There are six and a half hours left, delta is draining slowly, and the hedging corrections it causes are trivial next to everything else happening. If price moves this morning, something will have moved it. Charm joins this story later, and knowing that is worth the two seconds it took to check.

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12:30. Price has drifted down to 770.4 and gone quiet.

Volume has thinned. The range for the last hour is about forty cents. This is the part of the day where you start asking whether anything is left in it.

GEX is unchanged in shape. Still absorbing, still centred on 770.

CHEX has grown noticeably. The 770 strike is now several times the size it was at the open, and the card reads Time decay leans to selling.

What that tells you: the quiet now has a mechanism behind it. Delta is draining fast enough at that strike that dealers are having to adjust continuously, and those adjustments are themselves part of why price is holding where it is. The stillness is two forces holding each other, rather than an empty board.

That is a genuinely different situation from a quiet tape with a small charm reading, and until now the two looked the same.

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2:15. Still near 770. Charm is now the largest thing on any of the three lenses.

This is the window where CHEX earns its place. Delta decay per hour is accelerating, because that is what charm does as expiry approaches, and the hedging it forces has grown from a footnote into a peer of gamma. The two are working on the same strikes at the same time.

What that tells you: the pinning behaviour you might be seeing is a described condition, with a size you can read. You can see its size. You can see whether it is actually present today or whether you are reaching for a memory of a different Friday.

And what it still leaves open: whether price stays. A large enough order or a piece of news goes straight through all of it. Charm is a current rather than a wall.

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3:10. Fifty minutes left.

Charm is at its maximum for the session and will collapse to nothing at the bell along with the contracts. Gamma is doing the same. Everything the board has been telling you about 770 for six hours stops being true at 4pm, and Monday's board is a different board built from different open interest.

What that tells you: the expiry of this map is now measured in minutes. Whatever you make of the last hour, the structure expires with it.

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The same afternoon, without charm

Run the identical chart back with one difference: it is a Tuesday, the front expiry is Friday, and CHEX is small all day.

Price is still quiet. The range is still forty cents. GEX still says absorbing, still centred on 770. On a chart the two afternoons are indistinguishable.

But now the quiet has no clock behind it. Decay is too small to hold anything in place, so if price is sitting still it is sitting still for want of interest, which is a far more fragile condition than two forces in balance.

Those are different afternoons. Same chart, same gamma read, different situation. Telling them apart is the whole reason the third lens exists.

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What that afternoon handed you

One fact: what the clock is doing to the board. The entry, the direction, and the decision to hold or close or size up all stayed exactly where they were, which is with you.

The other new readings

Charm is the biggest of the additions, and four more came with it, each answering a question the map used to leave open.

Skew: what people are paying up for

Every lens above describes what dealers are forced to do. Skew describes what somebody was willing to pay for, which is a completely different kind of information.

It is one number: the implied volatility of the call twenty five percent likely to finish in the money, minus the put with the same odds. Both sit roughly the same distance from price, one above and one below. If the put is more expensive, people are paying more for protection than for upside.

Negative is normal for stocks and indices. Downside insurance almost always costs more than upside speculation, because falls are faster than rises and everyone knows it. So a negative number is Tuesday, rather than a warning.

The level tells you very little. The change is the reading. A name that habitually sits at minus eight is saying only that it is Tuesday again. The same name moving from minus three to minus ten in a week is telling you something, because somebody has started paying up for protection.

Compass shows you the level today. Tracking the change across days comes later, and the page says so rather than implying more than it has.

The expiry cycle

A line that appears only in the fortnight around a monthly expiration and stays quiet the rest of the time.

Options expire on a schedule, and the third Friday of each month is by far the largest. March, June, September and December are larger still, when index and single-stock contracts go together. In the week into one of those, positioning concentrates. On the day, it expires. And then a large block of open interest simply stops existing, and every hedge built on it stops with it.

It is a diary entry rather than a forecast: the one condition on the whole board that is known in advance, which earns it a line of its own.

The card names the phase, the date and how many sessions away it is. Outside that window it stays quiet, because "twelve sessions past the expiry" on an ordinary Tuesday is a fact nobody needs.

What changed overnight

Open interest settles once a day, after the close. That makes the change from yesterday the slow-timeframe equivalent of watching the tape: it is the difference between a wall that has stood for a month and one that was built last night.

The Telescope lists the strikes that moved most, with calls and puts separately, and whether each was built or drained as a share of itself.

It counts contracts, and leaves the meaning of the count to you.

One thing to know: Compass compares the days it recorded. It starts recording a symbol and expiration the first time you look at it, so the first comparison appears a session later. Watching begins when you open something.

Vanna sitting below price

A list of the large vanna concentrations beneath current price on the near-dated expirations, with how far below and how large relative to the biggest level on that date.

It exists because vanna behaves differently from gamma. Gamma responds to price moving; vanna responds to volatility moving, and volatility tends to move when price falls. So a heavy vanna level below price is a place where dealer hedging would change character if the market got there.

Compass reports what is sitting there, and stops there deliberately. Saying whether price has already been down to it would need a record of how low price has traded since the level appeared, and Compass keeps price history for the current session only. Calling a level "unresolved" on that basis would be an assertion we have no way to check.

It stays quiet about waiting, too. Some traders use exactly that rule. It is a reasonable rule, and testing it is the next section.

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What scoring these will take

Everything in this document is new, and grading comes next.

That word means something specific here. Compass records every level the standard map flags and checks it against what price actually did next, in public, including the sessions where the answer is unflattering. Until a reading has been through that, it is context, and we label it as such rather than let it arrive looking as settled as the rest.

Grading a rule that says wait is harder than grading one that says look here, and the reason is worth understanding, because it applies to your own rules too.

A rule that stops you trading leaves no losses to count. Wait, and price comes down to the level, and you remember it: the rule worked. Wait, and it runs twelve percent without you, and that lands in your results as a shrug. So a filter that costs you real money can feel correct for years, and the better it feels the less anyone examines it.

Testing one properly means measuring the trade you skipped. For every occasion the condition appeared: did price ever come back to that level, and how long did it take. What happened if you entered anyway. What happened if you waited. And, the column that can kill the rule, what did price do in the cases where it never came back at all.

Then the same three disciplines every claim in Compass has to pass. The thresholds and the definition of success written down before the test runs, so nobody goes fishing. The measurement itself fed a known answer and a known non-answer first, because an instrument that always passes is measuring nothing. And a shuffle test at the end: scramble which sessions had the condition while leaving every price path untouched, thousands of times, and see whether the real ones can still be told apart.

If it passes, it earns plainer language. If it fails, we will say so here, in this document, the way we said it about the sign of a node.

The honest part

CHEX is new, it is labelled beta, and its grading is still ahead of it. Every level the standard map flags gets scored against what price actually did next, and in time charm will get the same treatment. Until it does, treat it as an extra piece of context.

We would rather ship it with that said out loud than let the third lens arrive looking as settled as the first.

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Compass describes terrain. What you do with it is yours.