The ledger stays stricter than the rail
A payments company can move money. It should not become the product.
I keep seeing designs where the wallet, the ledger, and the rail get folded into one sentence. Then a balance becomes whatever the last callback said. A dispute becomes a screenshot. The person holding the phone cannot tell whether the money is held, released, or lost.
On Reton I keep those as three lines. The wallet is what a person sees. The ledger is double-entry, and it is stricter than the partner’s status codes. Interswitch is the payments company underneath: cards, transfers, and bill payments.
That split is also what I look at in a consultation. A useful design review starts by asking which system is allowed to say the balance changed.