> For the complete documentation index, see [llms.txt](https://docs.kolibrio.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.kolibrio.xyz/searchers/eth-kolibrio-ofa-searcher-connection.md).

# ETH Kolibrio OFA Searcher Connection

##

**Summary:** The interface is fully compatible with MEV Blocker. Connect to the WebSocket, include the `X-Bev-Signature` header, subscribe to partial pending transactions, and receive notifications via JSON‑RPC. Then, construct your backrun bundle and send it using `eth_sendBundle`.

### Endpoint

`wss://bev-relay.kolibr.io/eth`

**Required HTTP header** when establishing the WebSocket session:

`X-Bev-Signature: <signature>`

> The X-Bev-Signature header is used for authentication/authorization. The signature format and keys are provided by the Kolibrio team.

***

### Subscription

After a successful connection, send the following JSON‑RPC request to subscribe:

```jsx
{"method": "eth_subscribe","params": ["mevblocker_partialPendingTransactions"]}
```

**Expected response:**

```jsx
{"jsonrpc": "2.0", "id": 1, "result": "0xd58bbbc0f5190962eff01b6f0ec17724"}
```

After this, you’ll start receiving `eth_subscription` notifications when new relevant transactions appear.

***

### Incoming Signal Format

Example notification:

```jsx
{
		"jsonrpc": "2.0",
		"method": "eth_subscription",
		"params": {
		"subscription": "0xd58bbbc0f5190962eff01b6f0ec17724",
				"result": {
						"chainId": "0x1",
						"to": "0x..",
						"value": "0x4fefa17b724000",
						"data": "0x",
						"accessList": [],
						"nonce": "0x10",
						"maxPriorityFeePerGas": "0x0",
						"maxFeePerGas": "0x7e1c65b04",
						"gas": "0x5208",
						"type": "0x2",
						"hash": "0xd...4c",
						"from": "0x.."
				}
		}
}
```

**Note:** All numeric fields are hex‑encoded.

***

### Sending a Bundle

Once you’ve built your signed backrun transaction, send it as a bundle via the same WebSocket or simple HTTP POST request:

```jsx
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_sendBundle",
  "params": [
    {
      "txs": [
        "0x02abcd...", // target transaction hash (32 bytes)
        "0x02abcd..." // your signed bacrkun raw transaction
        ...
      ],
      "blockNumber": "0xb63dcd",
      "minTimestamp": 0,
      "maxTimestamp": 1615920932
    }
  ]
}
```

***

### Best Practices & Constraints

* Treat the target transaction `hash` as a 32‑byte hex string (with `0x` prefix).
* Both transaction hashes and raw signed transactions are accepted in `txs`.
* The order of `txs` matters: target transaction first, followed by your backrun txs.

***

### Example Flow

1. Open WS connection → `wss://bev-relay.kolibr.io/eth` with `X-Bev-Signature`.
2. Send `eth_subscribe` to `mevblocker_partialPendingTransactions`.
3. Receive `eth_subscription` messages with `result` → process and build your backrun transaction.
4. Send `eth_sendBundle` containing the target hash and your signed transaction(s).

***

### Security Notes

* Keep your signing keys and `X-Bev-Signature` secrets secure.