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Fee-bump transactions (introduced in CAP-0015) are a native feature of the Stellar network that allow one account to pay the transaction fee for another. This is the foundational technology that enables Grat to provide gasless experiences.

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How they work

A fee-bump transaction is a special envelope that contains an “inner” transaction. The inner transaction contains the user’s intended logic (e.g., a payment or contract call) and is signed by the user. The outer fee-bump envelope is signed by a “sponsor” account, which agrees to pay the network fee.

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Native Security

Because fee-bumps are a native protocol feature, they are extremely secure. The sponsor only authorizes the payment of the fee and has no power to modify the inner transaction or access the user’s private keys. If the inner transaction is invalid or its signatures are missing, the entire fee-bump is rejected.

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Grat’s Role

Grat automates the creation and submission of these envelopes. When your app sends an XDR to Grat, the relay handles the wrapping, signing with its own channel accounts, and submission to the network in a single atomic step. View on GitHub