Searchers — Submit Bundles

A searcher watches the mempool for profitable opportunities (arbitrage, back-runs, liquidations) and packages them into atomic bundles. Submitting those bundles is how searcher order flow reaches a builder.

On Vouch, bundles are submitted to the Vouch Builder — the builder behind builder.vouch.run. It assembles blocks from those bundles and bids through the MEV-Relay.

This is the Vouch Builder — not BlockFerret

Bundle submission goes to the Vouch Builder. BlockFerret is the separate Switch.win × Vouch alliance builder. (Bundle submission to BlockFerret is not currently available.)

How it fits the stack

Endpoint and method

• Endpoint: POST https://builder.vouch.run
• Method: eth_sendBundle (JSON-RPC 2.0) — this is the only method the edge accepts.

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_sendBundle",
  "params": [{
    "txs": ["0x..."],
    "blockNumber": "0x1A2B3C",
    "minTimestamp": 0,
    "maxTimestamp": 0,
    "revertingTxHashes": []
  }]
}

Authentication

Requests are authenticated with the standard Flashbots signature scheme:

• Header: X-Flashbots-Signature: <0x-address>:<0x-signature>
• The signature is over keccak256 of the raw request body, rendered as a 0x-hex string, signed with the EIP-191 personal_sign envelope.
• The recovered address must match the header address and be on the allowlist.

import json, requests
from eth_account import Account
from eth_account.messages import encode_defunct
from web3 import Web3

body = json.dumps(payload, separators=(',', ':'))      # the exact bytes you send
body_hash = Web3.keccak(text=body).hex()               # 0x-hex string
signature = Account.sign_message(
    encode_defunct(text=body_hash), private_key=key
).signature.hex()

requests.post(
    "https://builder.vouch.run",
    data=body,
    headers={
        "Content-Type": "application/json",
        "X-Flashbots-Signature": f"{address}:{signature}",
    },
)

Failed authentication returns a generic 401 — the proxy never reveals which check failed.

Onboarding

Bundle submission is allowlisted:

1. Send your signing address to the Vouch team (see Support).
2. Vouch adds it to the allowlist.
3. Once allowlisted, your signed bundles are accepted immediately.

Bundle fields

Field	Notes
txs	The signed transactions in the bundle.
blockNumber	Required. An absolute target block (0x-hex or decimal). latest, pending, and 0 are rejected.
replacementUuid	Optional. Replaces an earlier bundle targeting the same block.
minTimestamp / maxTimestamp	Optional validity window (0 = no bound).
revertingTxHashes	Optional. Transactions allowed to revert without invalidating the bundle.

Limits

• Up to 64 transactions per bundle.
• Combined transaction bytes ≤ 192 KiB; request body ≤ 256 KiB.
• 120-second replay window — an exact duplicate body within 120s is rejected (409).
• Only eth_sendBundle is accepted.

PulseChain notes

• Searcher bundles pay block.coinbase (the standard Flashbots coinbase-transfer pattern). The Vouch Builder sweeps the full coinbase delta to the proposing validator's fee recipient as the block's payment transaction.
• PulseChain's base fee is high (roughly 500k–700k gwei), so the payment transaction's base-fee burn is ~10–15 PLS. Dust bundles whose payment is below the base-fee burn are rejected by validation.

Support

• Telegram