Ethereum

This API provides protected pending transactions and bundles on Ethereum mainnet and accepts backrun bundles over the same WebSocket connection. The model is similar to Base but without flashblocks; latency still matters, but auctions are not sub-200ms.

An API key is required for access.

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WebSocket Connection

Connect using your API key:

wss://eth.novarpc.xyz/ws/v1/<API_KEY>

The protocol is JSON-RPC 2.0 over WebSocket. Clients must reconnect and resubscribe if the connection drops. Subscriptions are not persisted.

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Subscribing to Flow

After connecting, send eth_subscribe to receive qualifying flow. You may subscribe to transactions, bundles, or both.

Pending transactions:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_subscribe",
  "params": ["nova_partialPendingTransactions"]
}

Pending bundles:

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "eth_subscribe",
  "params": ["nova_partialPendingBundles"]
}

Each subscription returns a subscription ID:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0xa04fcb2de702f3bcd205ce666b7d5232"
}

This ID is used client-side to match incoming messages to the corresponding subscription.

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Receiving Data

Subscribed data is delivered via eth_subscription messages.

For individual transactions, the result field contains a single transaction object:

{
  "jsonrpc": "2.0",
  "method": "eth_subscription",
  "params": {
    "subscription": "0xa04fcb2de702f3bcd205ce666b7d5232",
    "result": {
      "chainId": "0x1",
      "from": "0xcba40bd88d70ec7b31a898e1a5d1cffde91069f2",
      "to": "0xa44f26477bd3460103310395f4e3b713d4c9e5d6",
      "hash": "0x04f2103bed46aef0edf4ece05c5a43a72df127315b097e6bc1615ac8d8cd59f9",
      "value": "0x18fae27693b40000",
      "gas": "0x5a3c",
      "maxPriorityFeePerGas": "0x216744fd",
      "maxFeePerGas": "0x4b04cc44a",
      "nonce": "0x1ca",
      "type": "0x2",
      "data": "0x",
      "accessList": []
    }
  }
}

For bundles, the result field is an array of one or more transactions:

{
  "jsonrpc": "2.0",
  "method": "eth_subscription",
  "params": {
    "subscription": "0xc06fe452246374c64932164bbc045530",
    "result": [
      { "...tx1 fields..." },
      { "...tx2 fields..." }
    ]
  }
}

The only structural difference between transactions and bundles is that bundles return an array. In both cases, the hash field identifies the originator transaction or bundle that must be referenced when backrunning.

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Sending Bundles

Backrun bundles must be submitted over this WebSocket connection. Sending them to a standard HTTP eth_sendBundle endpoint will not work.

{
  "jsonrpc": "2.0",
  "id": 3,
  "method": "eth_sendBundle",
  "params": [
    {
      "txs": [
        "0xOriginatorHash",
        "0xRawSignedTransaction"
      ]
    }
  ]
}

The txs array must be ordered. The first element is always the hash of the pending transaction or bundle you are backrunning. Subsequent elements are your signed transactions in raw hex form.

When backrunning a received bundle, each transaction will appear with a generated bundle hash. Include that generated hash only once as the first element in txs.