Multiswap is a discrete financial system. A transaction begins at one ledger state and ends at another. Reserves, scales, and prices are defined at the states; value flow occurs along the directed transition between them.
That description is not an approximation. It is the native geometry of a blockchain.
Discrete stochastic calculus gives this geometry an exact financial accounting rule. It distinguishes quantities defined at states from flows defined on transitions, preserves the order between previsible inventory and nonprevisible price, and recovers Itô calculus in the stochastic continuum limit. Applied to Multiswap, it produces post-trade value flow directly:
dsi=(dai)Pi+aidPi.
The first term evaluates price at the destination state. The second revalues the opening reserve. Post-trade execution is therefore not an arbitrary conservative quote convention. It is the finite execution rule compatible with Itô accounting.
The same calculus gives an exact coefficient 1-form
dci=[G,ci]
whose edge coefficients determine whether an operation moves each Reserve Asset and the LP Token in the permitted direction. This coefficient order contains the familiar swap and liquidity actions, but it also identifies a wider endpoint region containing direct permanent-reserve contributions, LP Token under-minting, general withdrawals, and heterogeneous multi-asset liquidity.
On the binary tree, exact coefficient order must hold on both outgoing branches. In the stochastic continuum limit, this removes the coefficient's Brownian component and leaves a one-sided generator condition. The boundary between safe and unsafe coefficient production is the backward diffusion equation
(∂t+21∂x2)ci=0.
Surplus settlement provides the central application. A direct price-preserving state edit leaves this region by expanding the receive-asset coefficient. An ordinary counter-swap remains inside it because every step is an exact supported transition.
This article develops the complete argument from first principles. No prior knowledge of discrete calculus is assumed.
The results assume exact arithmetic, positive reserves and scales, homogeneous elasticities, and
0<es<1,eP=1−es.
Coefficient order establishes state admissibility. A complete protocol operation must additionally specify funded token movements, valid consideration, account ownership, rounding, user limits, atomicity, and MEV policy.