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The eth_sendBundle method lets you submit an ordered set of signed transactions directly to BlockRazor’s BSC Block Builder. Because BlockRazor’s Block Builder has achieved a cumulative block production rate of 37% on BSC—ranking first chain-wide—bundles submitted here have a high probability of inclusion without competing through the public mempool. Transactions in a bundle execute atomically in sequence: if any transaction reverts, the entire bundle is excluded from the block unless the reverting transaction is explicitly allowed.
eth_sendBundle is free for all new registered users on BSC with no rate limits. No subscription is required to get started. See Pricing for details on the BSC Package and advanced builder features.

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Endpoint

POST https://builder.blockrazor.io/bsc
Authentication is performed via a Bearer token passed in the Authorization header.

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Request

The request follows the standard JSON-RPC 2.0 envelope. The single element of params is a bundle configuration object.

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Bundle Parameters

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txs
string[]
required
An ordered array of signed raw transactions encoded as hex strings (each prefixed with 0x). Transactions are executed in the order provided. The atomicity guarantee means all transactions land together or none do.
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blockNumber
string
required
The target block number for bundle inclusion, expressed as a hex string (e.g., "0xE4E1C0"). The bundle is only eligible for this exact block and is automatically expired if the block passes.
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minTimestamp
integer
Optional. The minimum Unix timestamp (in seconds) before which the bundle should not be included. If the target block’s timestamp is earlier than this value, the bundle will be skipped.
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maxTimestamp
integer
Optional. The maximum Unix timestamp (in seconds) after which the bundle is no longer valid. If the target block’s timestamp exceeds this value, the bundle will not be included.

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Code Examples

curl -X POST https://builder.blockrazor.io/bsc \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer YOUR_AUTH_TOKEN' \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_sendBundle",
    "params": [
      {
        "txs": ["0xSIGNED_TX1", "0xSIGNED_TX2"],
        "blockNumber": "0xE4E1C0"
      }
    ],
    "id": 1
  }'

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Response

A successful submission returns a bundleHash that uniquely identifies your bundle within the Block Builder. Retain this value to trace bundle execution via eth_traceBundle.
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bundleHash
string
A unique hash identifying the submitted bundle. Use this with eth_traceBundle to retrieve detailed execution traces and confirm inclusion in the target block.
Response Example
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "bundleHash": "0x7f3a9c2e1d4b..."
  }
}

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Block Builder Advantage

BlockRazor’s Block Builder is deployed in multiple regions worldwide with low-latency communication links to BSC validators. Its multi-algorithm block construction maximizes block value, which incentivizes validators to prefer BlockRazor-built blocks. Submitting via the Block Builder endpoint bypasses the public mempool entirely, providing MEV protection and faster finality compared to standard eth_sendRawTransaction.
To simulate your bundle before committing to on-chain submission, use eth_callBundle. Simulation lets you verify gas usage and catch reverts without spending gas or revealing your strategy to the mempool.
Combine minTimestamp and maxTimestamp to create time-bounded bundles. This is useful for strategies that are only profitable within a specific time window, such as those dependent on external oracle updates.

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