Adding exchange features to a wallet starts with one API and the screens built around it. Swaps come first, almost always. Cross-chain conversion and fiat buys can wait until that base is steady. Wiring up the connection is quick, a few hours of work. The weeks go into everything after: the wording, the edge cases, the parts that decide whether people trust the screen.

Hardly any wallet team builds its own matching engine now. An efficient exchange API for crypto wallets already carries liquidity and settlement, delivered as a service. The wallet holds the interface and the customer. The user holds the keys. Split that way, even a three-person team can pull it off.

Start With the Swap Screen

Most wallets open with a plain swap,…