Anders Elowsson on Warpcast

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Anders Elowsson

@anderselowsson

Q&A 🧵 on EIP-7918 This thread summarizes my responses on Ethereum Magicians to four questions from @dataalways concerning: the coupling of fee markets, alternative designs, a comparison with EIP-7762, and the empirical impact of a price floor for blobs. Let’s dig in 👇

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Anders Elowsson

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Question 1: concerns the coupling of fee markets that EIP-7918 introduces. Is this something we want? The answer is yes! The price of blobspace depends on the price of execution gas, and this should be reflected in the fee market. https://ethereum-magicians.org/t/eip-7918-blob-base-fee-bounded-by-execution-cost/23271/4#p-56700-question-1-coupling-of-fee-markets-1

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Currently, the mechanism behaves as follows: * Users purchase blobspace by spending execution gas and blob gas. * The blob gas fee update mechanism is unaware of the cost of execution gas, and thus unaware of the total cost of blobspace. * A relatively high cost of execution gas renders changes to the blob gas fee subordinate in determining quantity demanded. * The mechanism fails to timely converge on equilibrium whenever the cost of execution gas dominates the cost of blob gas.

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In essence: the current mechanism behaves as if it controlled the price of blobspace, when it only controls the price of blob gas. It increases the price of blobspace in minuscule 0.00001% steps to attain equilibrium—because that’s a 10% increase in the blob base fee.

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EIP-7918 resolves this by adjusting the fee mechanism when execution gas costs dominate. The two fee markets remain fully independent within the operational range where the blob base fee carries the price signal.

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Question 2: asks if there are alternative parameter settings and designs? A nice thing about EIP-7918 is its minimalist nature. It activates once the cost of the cheapest tx exceeds the cost of target blobs.

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That’s when execution costs dominate for all blob consumers. It would be possible to alternatively amortize across max blobs, or across the square root of target/max blobs, but target blobs is a neutral and viable solution.

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There is also one other option on the same theme, which I call a composite fee market. It is a larger conceptual change and would have to be part of a potential future harmonization of fee markets. It can however be interesting to review to also understand EIP-7918.

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Composite fee market The composite fee market updates the blob base fee based on the *real* demand function for blobspace: Q(b + c), where Q is quantity demanded, b is the blob base fee, and c is the amortized tx cost expressed per blob gas. Say the desired shift q to the price of blobspace is ±12.5%. The blob base fee is then updated from block 0 to 1 by: b₁ = b₀ + q(b₀ + c₀) To the user who employs the same execution gas per blob gas as in c₀, the maximal change in the cost of blobspace per slot would still be 12.5%. The proportional change in b can however be dramatic whenever b << c. This is as intended—it allows the composite fee auction to quickly converge on equilibrium, no longer “getting stuck” at lower blob base fees.

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Question 3: is a request for a comparison with EIP-7762. Both EIPs reference the cost of execution gas. EIP-7762 hard-codes a price floor to work under current circumstances. EIP-7918 makes the floor dynamically vary with the cost of execution gas. https://ethereum-magicians.org/t/eip-7918-blob-base-fee-bounded-by-execution-cost/23271/4#p-56700-question-3-comparison-with-eip-7762-4

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While the fixed floor of EIP-7762 might make it easier to justify tuning the floor to achieve desired outcomes going forward, it is possible to argue that this is rather a drawback. A self-adjusting dynamic floor is a neat ideal to strive towards.

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EIP-7918 also accounts for future scaling. The cost of (providing) 128 kB of DA will fall drastically over the next 50 years due to improvements in hardware and software. EIP-7918 reduces the price floor when target blobs increases to reflect this.

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The figure shows that the floor under EIP-7762 remains fixed at 2**25 wei (blue). The floor under EIP-7918 varies with the execution base fee; under Pectra settings along the black arrow. If the blob target increases to 12, the floor adjusts down to the grey arrows, etc.

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Concerning implementation complexity: * EIP-7762 changes one constant and adds block_timestamp as an input variable to calc_excess_blob_gas(). This input is included in an if statement evaluating timestamps, returning 0 if TRUE. * EIP-7918 adds one if statement to calc_excess_blob_gas() evaluating computed gas prices, altering the return to be parent.excess_blob_gas + parent.blob_gas_used // 3 if TRUE. Whether one change brings more complexity than the other is hard for me to tell. They should both be fairly similar and both be straightforward.

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Question 4: what is the historical empirical impact? Here are three weeks in November 2024 when the average execution base fee was 16 gwei. EIP-7918 would then have set a higher floor than EIP-7762. The Pectra target of 6 blobs was used for amortization.

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For three weeks in March 2025 the average execution base fee was instead 1.3 gwei. Under such conditions, EIP-7918 instead sets a lower floor than EIP-7762. Thanks to @soispoke for providing the data.

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