SeismicGasFiller

Gas estimation filler with deferred support for seismic transactions

SeismicGasFiller handles gas estimation for both Seismic and standard transactions. For Seismic transactions with a wallet, it defers gas estimation to the fill phase and signs the transaction before calling eth_estimateGas, so the node can authenticate the sender and execute gas estimation against msg.sender-gated private state.

Overview

Gas estimation for shielded transactions presents two challenges:

The node needs to estimate gas on the encrypted calldata (because that is what will actually be executed), but the calldata is not encrypted until SeismicElementsFiller runs.
When the contract's gas cost depends on private state gated by msg.sender, the node must be able to authenticate the sender during estimation — an anonymous eth_estimateGas would execute against a zero-address caller and produce an incorrect estimate.

SeismicGasFiller addresses both:

For Seismic transactions with a wallet — Defers gas estimation to the fill() phase, signs the transaction, and submits the signed envelope to eth_estimateGas over a fresh RPC client using the stored URL.
For Seismic transactions without a wallet — Falls back to Alloy's standard unsigned GasFiller. This is the default RecommendedFillers path for unsigned providers.
For standard (non-Seismic) transactions — Always delegates to the inner GasFiller for normal prepare-phase estimation.

Additionally, SeismicGasFiller rejects Seismic CREATE transactions (no to address), which are not supported for the Seismic transaction type.

Definition

pub struct SeismicGasFiller<N: SeismicNetwork>
where
    N::UnsignedTx: Send + Sync,
{
    inner: GasFiller,
    rpc_url: Option<reqwest::Url>,
    wallet: Option<SeismicWallet<N>>,
}

Field

Type

Description

inner

GasFiller

Standard Alloy gas filler for non-seismic and unsigned fallback paths

rpc_url

Option<reqwest::Url>

RPC URL used for signed eth_estimateGas on seismic transactions

wallet

Option<SeismicWallet<N>>

Wallet used to sign the tx before submitting to eth_estimateGas

Constructors

`new`

Create a SeismicGasFiller with both an RPC URL and a wallet for signed gas estimation.

pub fn new(rpc_url: reqwest::Url, wallet: SeismicWallet<N>) -> Self

Parameter

Type

Required

Description

rpc_url

reqwest::Url

Yes

RPC endpoint for the eth_estimateGas call

wallet

SeismicWallet<N>

Yes

Wallet used to sign the transaction before sending

Returns: A new SeismicGasFiller configured for signed gas estimation on Seismic transactions.

`default`

Create a SeismicGasFiller with no RPC URL and no wallet. Gas estimation falls back to the standard unsigned GasFiller path.

impl<N: SeismicNetwork> Default for SeismicGasFiller<N> { ... }

This is the variant used by the unsigned provider's RecommendedFillers default.

Two-Phase Design

Like all Alloy fillers, SeismicGasFiller implements TxFiller<N> with prepare and fill phases.

Prepare Phase

Seismic tx + wallet present: Returns immediately without estimating gas (deferred to fill phase so the tx can be signed after SeismicElementsFiller runs)
Seismic tx without a wallet or non-Seismic tx: Delegates to the inner GasFiller, which calls eth_estimateGas as normal

Fill Phase

Seismic tx + wallet present: The calldata is now encrypted (by SeismicElementsFiller). The filler signs the transaction with the wallet and submits the signed envelope to eth_estimateGas via the stored rpc_url, then fills in the gas limit.
Seismic tx without a wallet or non-Seismic tx: Delegates to the inner GasFiller to apply the prepared gas estimate.

Validation

SeismicGasFiller enforces that Seismic transactions cannot be CREATE transactions (i.e., transactions without a to address that deploy new contracts). If a Seismic transaction request has no to field, the filler returns an error.

This restriction exists because the Seismic transaction type (0x4A) is designed for calling existing contracts with encrypted calldata, not for deploying new contracts.

Usage

Default (Automatic)

In most cases, SeismicGasFiller is configured automatically by the provider:

use seismic_prelude::client::*;
use seismic_alloy_network::reth::SeismicReth;

let signer: PrivateKeySigner = "0xYOUR_PRIVATE_KEY".parse()?;
let wallet = SeismicWallet::<SeismicReth>::from(signer);
let url = "https://testnet-1.seismictest.net/rpc".parse()?;

// SeismicGasFiller is set up automatically with the same URL and wallet
let provider = SeismicProviderBuilder::new()
    .wallet(wallet)
    .connect_http(url)
    .await?;

Manual Construction

If building a custom provider stack:

use seismic_alloy_provider::fillers::SeismicGasFiller;
use seismic_alloy_network::reth::SeismicReth;

let rpc_url: reqwest::Url = "https://testnet-1.seismictest.net/rpc".parse()?;
let gas_filler = SeismicGasFiller::<SeismicReth>::new(rpc_url, wallet);

Pipeline Position

SeismicGasFiller is the last filler in the signed provider chain, running after SeismicElementsFiller:

WalletFiller
  -> NonceFiller + ChainIdFiller
  -> SeismicElementsFiller  (encrypts calldata)
  -> SeismicGasFiller       (signs encrypted tx and estimates gas)

If SeismicGasFiller ran before SeismicElementsFiller, it would estimate gas on the plaintext calldata, which would produce an incorrect gas estimate.

Notes

For Seismic transactions, gas estimation happens on the encrypted, signed calldata, which may differ from the plaintext gas cost.
The signed gas-estimation path authenticates msg.sender to the node, so contracts that gate state on msg.sender return correct estimates.
The GasFiller inner field handles all non-Seismic gas estimation logic and the unsigned Seismic fallback.
Seismic CREATE transactions are explicitly rejected with an error.
rpc_url and wallet are both Option to support the default / unsigned paths.