Overview

End-of-block bundles are guaranteed to execute at the tail of the transaction list, after all regular orderflow — regardless of how many other bundles are included.

How It Works

1. The searcher submits a bundle via eth_sendEndOfBlockBundle targeting a specific block.

2. The builder segregates end-of-block bundles into a separate ordered group.

3. When building the block, regular bundles and mempool transactions are placed first.

4. End-of-block bundles are appended at the tail.

5. If the builder wins the slot, the bundle is guaranteed to appear last (or among the last transactions) in the final block.

Use Cases

• Settlement protocols — execute finalization logic after all other activity in the block

• Residual arbitrage — capture price discrepancies left by the rest of the block

• Oracle updates — push state updates as the last action before the slot closes

• MEV protection — execute after the main block is built to avoid being sandwiched

Compatibility

End-of-block bundles use the same parameter format as eth_sendBundle — including replacementUuid, revertingTxHashes, and refund parameters. Cancel with eth_cancelBundle.

Rate Limits

Standard order flow rate limits apply. Contact the Eureka team to request higher limits for production integrations.

API Methods

Method	Description
eth_sendEndOfBlockBundle	Submit a bundle for guaranteed end-of-block placement

All requests are sent as JSON-RPC 2.0 POST to:

https://rpc.eurekabuilder.xyz