eth_sendEndOfBlockBundle

Submit a bundle for guaranteed end-of-block placement. The builder places end-of-block bundles at the tail of the transaction list, after all regular orderflow has been included.

This is useful for protocols that need to execute after all other transactions in a block — for example, settling state at the end of a slot, capturing residual arbitrage, or appending cleanup transactions.

Requires the X-Flashbots-Signature header.

Parameters

Identical to eth_sendBundle:

Field	Type	Required	Description
txs	string[]	Yes	Array of signed transactions as 0x-prefixed RLP-encoded hex strings
blockNumber	string	Yes	Target block number as a hex string (e.g. "0x1234567")
minTimestamp	number	No	Minimum block timestamp (Unix seconds) for inclusion
maxTimestamp	number	No	Maximum block timestamp (Unix seconds) for inclusion
revertingTxHashes	string[]	No	Tx hashes allowed to revert without invalidating the bundle
droppingTxHashes	string[]	No	Tx hashes that, if already included on-chain, cause the bundle to be dropped
replacementUuid	string	No	UUID to enable bundle replacement
replacementNonce	number	No	Monotonically increasing nonce for replacement ordering
refundPercent	number	No	Percentage (0–100) of builder profit to refund to refundRecipient
refundRecipient	string	No	Address that receives the refund payment

Request

{
  "jsonrpc": "2.0",
  "method": "eth_sendEndOfBlockBundle",
  "params": [{
    "txs": ["0x02f8..."],
    "blockNumber": "0x137f8a0"
  }],
  "id": 1
}

Response

{
  "jsonrpc": "2.0",
  "result": {
    "bundleHash": "0xabcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890"
  },
  "id": 1
}

Field	Type	Description
bundleHash	string	0x-prefixed bundle hash. Use with eureka_getBundleStats to track inclusion.

Placement Guarantee

The bundle is appended after all regular bundles and mempool transactions in the block. If the builder wins the slot, the end-of-block bundle will appear last (or among the last transactions) in the final block.

Notes

• Bundle replacement and cancellation work the same as with eth_sendBundle — use replacementUuid to replace or call eth_cancelBundle to cancel.

• The bundle is only eligible for the specified blockNumber and is discarded after that block is built.