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Add fee_payer hint to TempoTransactionRequest so eth_fillTransaction can account for cold storage accesses when a separate fee payer will sponsor the transaction. Amp-Thread-ID: https://ampcode.com/threads/T-019d5130-90ae-75be-8f7d-c311b11c4fba Co-authored-by: Amp <amp@ampcode.com>
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Problem
eth_fillTransactionunderestimates gas for sponsored (fee payer) transactions by ~8k gas, causing the second transaction to fail with an out-of-gas error.When viem sends
feePayer: truein the request, the node silently ignores it becauseTempoTransactionRequesthas no such field. Gas estimation then assumesfee_payer == caller, missing the cold storage accesses needed to load the actual fee payer's balance and fee token preference (which are at a different address).Solution
Add a
feePayer: Option<bool>hint field toTempoTransactionRequest. Whentrue, setfee_payerto a sentinel address (Address::ZERO) duringtry_into_tx_envso estimation incurs the correct cold account/storage access costs for the separate fee payer address.A corresponding viem-side workaround (gas bump in
chainConfig.ts) can be removed once this is deployed.