7 Mistakes Developers Make When Integrating DEX Swaps

DEX swap volume crossed $250 billion per month in early 2026, and more of that volume is being routed programmatically through aggregator APIs. But integrating a swap API is not the same as calling a REST endpoint that returns JSON. The response contains raw transaction calldata destined for an on-chain router contract, and every field matters. Mishandle one and your transaction reverts, your user loses gas, or worse — they get a terrible price. These 7 mistakes show up repeatedly in production codebases. Each one has caused real on-chain losses, and each one is straightforward to fix. 1. Not Checking priceImpact Before Executing The swap API returns a priceImpact field as a decimal. A value of -0.0012 means -0.12% — a normal cost of trading. A value of -0.15 means -15% — your user is about to lose 15% of their trade to thin liquidity. Chainalysis estimated that price impact losses exceeded $900 million across DeFi in 2025, largely from automated systems executing swaps without checkin