Chains

Pre-configured chain definitions for Seismic networks

seismic-viem provides pre-configured viem Chain objects with Seismic transaction formatters. These chain definitions include the correct chain IDs, RPC endpoints, and custom formatters needed for Seismic's type 0x4A transactions.

Import

import {
  seismicTestnet,
  sanvil,
  localSeismicDevnet,
  createSeismicDevnet,
} from "seismic-viem";

Available Chains

Chain	Export	Chain ID	RPC URL	Description
Seismic Testnet	seismicTestnet	5124	https://gcp-1.seismictest.net/rpc	Public testnet
Sanvil	sanvil	31337	http://127.0.0.1:8545	Local Seismic Anvil
Local Devnet	localSeismicDevnet	5124	http://127.0.0.1:8545	Local seismic-reth --dev

Seismic Testnet

The public testnet for development and testing against a live Seismic network:

import { http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { createShieldedWalletClient, seismicTestnet } from "seismic-viem";

const client = await createShieldedWalletClient({
  chain: seismicTestnet,
  transport: http(),
  account: privateKeyToAccount("0x..."),
});

Sanvil

Local development chain using Sanvil (Seismic's fork of Anvil). Chain ID 31337 matches Anvil/Hardhat defaults:

import { http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { createShieldedWalletClient, sanvil } from "seismic-viem";

const client = await createShieldedWalletClient({
  chain: sanvil,
  transport: http(),
  account: privateKeyToAccount("0x..."),
});

Local Devnet

For running a local seismic-reth --dev node. Uses chain ID 5124 (same as testnet) but connects to localhost:

import { http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { createShieldedWalletClient, localSeismicDevnet } from "seismic-viem";

const client = await createShieldedWalletClient({
  chain: localSeismicDevnet,
  transport: http(),
  account: privateKeyToAccount("0x..."),
});

Choosing a Chain

Are you developing against a live network?
  -> Use seismicTestnet

Are you running Sanvil locally for rapid iteration?
  -> Use sanvil

Are you running seismic-reth --dev locally?
  -> Use localSeismicDevnet

Do you need a custom chain configuration?
  -> Use createSeismicDevnet()

SEISMIC_TX_TYPE

All chain configs use the Seismic transaction type constant:

import { SEISMIC_TX_TYPE } from "seismic-viem";

console.log(SEISMIC_TX_TYPE); // 74 (0x4A)

The value 74 (0x4A) is the EIP-2718 transaction type envelope identifier for Seismic transactions. This constant is used internally by the chain formatters and encryption pipeline to identify and construct Seismic-specific transaction payloads.

Chain Formatters

Each chain config includes seismicChainFormatters -- custom viem chain formatters that handle Seismic transaction fields. These formatters are applied automatically when you use a Seismic chain definition.

The formatters extend viem's standard transaction formatting to support the additional fields required by Seismic's type 0x4A transactions, including encryption metadata and signed read parameters.

You do not need to configure or interact with seismicChainFormatters directly. They are embedded in every pre-configured chain object and in chains created via createSeismicDevnet.

Custom Chain Factory

createSeismicDevnet

Create a custom chain definition for any Seismic-compatible node:

import { createSeismicDevnet } from "seismic-viem";

const myChain = createSeismicDevnet({
  nodeHost: "https://my-seismic-node.example.com",
  explorerUrl: "https://explorer.example.com",
});

Parameters

Parameter	Type	Required	Description
nodeHost	string	Yes	Base URL of the Seismic node (without /rpc)
explorerUrl	string	No	Block explorer URL for the chain

The factory returns a viem Chain object with:

• Chain ID 5124

• RPC URL set to {nodeHost}/rpc

• Seismic chain formatters included

• Optional block explorer configuration

Helper Factories

Convenience factories for common Seismic infrastructure:

import { createSeismicAzTestnet, createSeismicGcpTestnet } from "seismic-viem";

// Azure-hosted testnet instance N
const azChain = createSeismicAzTestnet(1);

// GCP-hosted testnet instance N
const gcpChain = createSeismicGcpTestnet(1);

These generate chain configs pointing to numbered Seismic testnet instances on Azure and GCP infrastructure respectively.

SeismicTransactionRequest

Seismic chain configs use a custom transaction request type that extends viem's standard TransactionRequest with Seismic-specific fields:

interface SeismicTxExtras {
  encryptionPubkey: Hex; // Client's compressed secp256k1 public key
  encryptionNonce: Hex; // AES-GCM nonce for calldata encryption
  messageVersion: number; // Seismic message format version
  recentBlockHash: Hex; // Recent block hash for replay protection
  expiresAtBlock: bigint; // Block number at which the transaction expires
  signedRead: boolean; // Whether this is a signed read request
}

You do not need to populate these fields manually. The shielded wallet client's encryption pipeline fills them automatically when sending transactions. They are documented here for reference and debugging purposes.

Field	Type	Description
encryptionPubkey	Hex	Client's compressed secp256k1 public key
encryptionNonce	Hex	Random nonce for AES-GCM encryption of calldata
messageVersion	number	Version of the Seismic message format
recentBlockHash	Hex	Recent block hash used for transaction replay protection
expiresAtBlock	bigint	Block number after which the transaction becomes invalid
signedRead	boolean	true for signed read requests, false for standard txs

See Also

• Installation -- Install seismic-viem and viem

• Seismic Viem Overview -- Full SDK overview and architecture

• Shielded Wallet Client -- Create a client using a chain config

• Encryption -- How calldata encryption uses chain-level formatters