Uniswap Trading API (Sepolia) - Intermittent 502/404 Errors on ERC20 Swaps

Hi everyone,

I'm encountering persistent issues with the Uniswap Trading API (https://trading-api-labs.interface.gateway.uniswap.org/v1/swap) when attempting ERC20 token swaps (e.g., WETH -> USDC) on the Sepolia testnet. I previously posted about this in the discussions forum (https://github.com/Uniswap/interface/discussions/7862) without a resolution, so I'm hoping someone here can help me out.

Problem:

The API https://trading-api-labs.interface.gateway.uniswap.org/v1/swapis frequently returning HTTP errors. These API errors are completely blocking the swap process, preventing transactions from being completed.

• 502 Bad Gateway
• 404 Not Found

Details:

The errors occur during the SwapTransactionAsync step within a classicSwap execution. (See screenshots below)

I'm unable to locate the source code for this specific API service to investigate further.

The swap process becomes stuck and cannot proceed due to these API errors.

Request:

Could anyone provide guidance on:

• The location of the Uniswap Trading API's source code?
• Potential causes for these intermittent 502/404 errors on the Sepolia testnet?
• Any recommended workarounds or alternative approaches for performing ERC20 swaps on Sepolia?

Thanks in advance for any help!

Start by reviewing discussion 7862 and the reported requests to the Sepolia Trading API endpoint, focusing on the SwapTransactionAsync step within classicSwap and the 502/404 responses. The issue is resolved when the service ownership or source location, cause, and a verified workaround or alternative for ERC20 swaps are documented.