

============================================================================================
PART 1 — how much deposit is ACTUALLY required? (drift buffer, NOT principal)
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An unmatched swap of an OWNED asset risks only the FX drift on the swapped notional over the
time until it settles (matched flow / rebalance / close). Required buffer = that drift.

   settle within     worst drift     req. buffer   vs "lock 90%"     vs CDP 150%
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          1 week           2.46%           2.46%        37x less        61x less
        ~1 month           5.75%           5.75%        16x less        26x less
      ~1 quarter          10.51%          10.51%         9x less        14x less
 full 2022 crash          20.45%          20.45%         4x less         7x less

  => "lock 90% of the swapped value" is the wrong mental model. You need the DRIFT (a few %
     for normal settlement), and it is covered IMPLICITLY by the user's own converted balance.
     No explicit lock. The user is never conditioned to deposit extra funds.


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PART 2 — swap ALL of one asset, NO lock, then SPEND. Drift eats the spend proportionally.
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  A holds 100 εUSD + 100 εEUR. A swaps ALL 100 εEUR -> USD @ 1.18 = 118 εUSD.
  A now holds 218 εUSD (nominal), 0 εEUR. NOTHING locked. Open position: 100 EUR of drift.

  A's SPENDABLE balance is marked to live backing = 100 USDC + 100 EURC-worth. As the rate
  moves, the marked (fair) value moves; A can always spend it; the drift is settled from the spend.

           rate now     A nominal εUSDA marked (spendable)      drift settled        A can spend
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        1.18 (flat)                218                218              $0.00            $218.00
      1.16 EUR fell                218                216              $2.00            $216.00
      1.14 EUR fell                218                214              $4.00            $214.00
       1.1 EUR fell                218                210              $8.00            $210.00
      1.22 EUR rose                218                222             -$4.00            $222.00

  Reading: A can SPEND THE WHOLE marked balance smoothly — no lock, no CDP, no conditioning.
  If EUR fell (1.18->1.14), A spends 214 not 218: the $4 drift is eaten proportionally from the
  spend, EXACTLY as you specified. A is FX-neutral (214 = what A's 100USD+100EUR is worth @1.14 —
  same as if A never swapped). If EUR rose, A spends MORE (222). The pool stays flat either way.


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PART 3 — progressive spend: A draws the account to ZERO; drift settles pro-rata each spend.
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  A swapped all EUR->USD @1.18; rate now 1.14. Nominal 218, marked 214, total drift $4.00.
  A spends in 4 equal chunks of the MARKED balance. Each chunk settles its pro-rata drift:

               spend #            marked outdrift settled (pro-rata)      remaining marked
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                     1                $53.50                 $1.00               $160.50
                     2                $53.50                 $1.00               $107.00
                     3                $53.50                 $1.00                $53.50
                     4                $53.50                 $1.00                 $0.00

  A spent $214.00 total (the full fair value). Pool paid out exactly its backing => FLAT.
  The "deposit" that got eaten = the drift, spread proportionally across the spends. A never
  locked anything; A just couldn't spend the phantom $4 that the rate move erased.


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PART 4 — the gap: the ONLY case the pool is exposed (and its bounds).
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  If a position settles fast (matched flow / batch rebalance within ~a month), buffer 5.75%
  covers it and the pool is flat. The gap appears only if the position stays OPEN through a move
  bigger than the buffer before it can be closed:
     buffer (1mo) 5.75%  vs  full-crash drift 20.45%  =>  worst gap 14.70% of notional.
  On 100 EUR that is $16.17 — bounded by THREE backstops:
     1. LIQUIDATION at ~buffer exhaustion (close the position early) => gap ~0 if rate is continuous.
     2. The NET-IMBALANCE BAND (±L% of reserve) => aggregate gap bounded regardless of any position.
     3. RATE SMOOTHING (FIATm controller) => don't liquidate on a wick; multi-oracle median.

  And note: on-BCH SPENDING never triggers this. εUSD/εEUR are fungible bearer tokens on BCH; the
  drift is a POOL inventory position (band-capped), settled in BATCH at the source-chain rebalance —
  the only place currency actually matters. Users spend freely; the desk carries the bounded drift.


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CALCULATION SUMMARY
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 REQUIRED DEPOSIT: the FX drift on the swapped notional over the settle window — ~2.46% (1wk),
   ~5.75% (1mo), ~20.45% (held through the 2022 crash). NOT the principal, NOT 90%,
   NOT a CDP's 150%. It is covered IMPLICITLY by the user's own converted balance => NO explicit lock.

 SPENDING: the user can swap 100% of one asset and spend the whole marked balance smoothly. Each
   spend is marked to live backing, so any rate loss eats the spend PROPORTIONALLY (your rule). The
   user is FX-neutral (spends exactly what their assets are worth); the pool stays flat.

 THE GAP: the only pool exposure = an adverse move exceeding the (implicit) buffer before the
   position closes. Bounded by liquidation + the band + rate-smoothing, and irrelevant to on-BCH
   spending (bearer tokens; drift is a band-capped pool inventory position, batch-settled at the
   source chain). This is what makes "spend your whole balance without locking" both real and safe.

 CAVEAT: marked spend keeps the pool EXACTLY flat but requires the spend to be desk-marked at the
   boundary (withdraw/settle); pure on-BCH bearer spend puts the (small, band-capped) drift on the
   pool. Both avoid any user lock. Real 2021-23 path, seeded; directional, not a forecast.

