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Searcher Docs

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⚑ Searchers can use Skip Select endpoints to risklessly capture arbitrage, liquidation, and other MEV opportunities in the Cosmos ecosystem.

β†’ Skip maintains easy-to-use packages (javascript, python) for signing and sending bundles of transactions to the Skip Relay. Example usage can be found in each package’s documentation.

πŸ†“ Skip currently charges no fees to anyone for its auctions, services, or endpoints πŸŽ‰

πŸ₯ͺ Skip allows validators to choose preferences for what kinds of MEV they allow. This means atomic frontrunning and/or sandwich-type bundles may be rejected upon submission, depending on the validator’s and chain’s preferences.

🏦 Auction​

⭐ Overview​

The Skip Select Auction is an auction for top-of-block, non-reverting, bundle inclusion.

  • ☝️ Top-of-block: The bundle submitted will be executed at the top of the block for the block height desired by the searcher.
  • πŸ›‘οΈ Non-reverting: No transaction in the bundle will ever fail on chain, protecting searchers from wasting bid payments and gas fees on failed MEV extraction attempts.
    • Stated in another way, only auction winners pay the auction bid and spend gas fees, there is no cost or downside to participating and losing in the Skip auction!
  • 🎁 Bundle Inclusion: Searchers submit a set of transactions, denoted as a bundle, to the auction for top-of-block, non-reverting inclusion.

🫡 Participation​

In order to compete in the auction, a searcher must sign and submit a bundle to the Skip Relay (more details on how to do this in the sections below). A payment to the AuctionHouseAddress must exist in one of the searcher's transactions in their submitted bundle.

  • Currently, this payment must be a Cosmos MsgSend message, but we are actively exploring contract-based payments for CosmWasm and EVM chains.

  • πŸ‘‰ You can find the AuctionHouseAddress per chain here: Chain Configuration (or in

πŸ₯‡ Winning​

The winner of an auction for any given block height is the non-reverting bundle submitted to the auction that has the largest payment to the AuctionHouseAddress and respects validator preferences (currently only front-running protection, more details in the preferences section below).

The greater your bundle’s payment to the AuctionHouseAddress, the greater the likelihood that it will be included on-chain. If you lose the auction, you can explore Skip's activity dashboard ( or the chain afterwards to discover bundles with higher payments to the AuctionHouseAddress that outbid you.

  • πŸ’Έ The entirety of your Auction House payment is sent to the proposing validator and network stakers. You do not need to worry about this split, Skip handles it automatically on-chain.

✍️ Signing Bundles​

Skip requires searchers to sign bundles with the private key they also used to sign their transactions with in their submitted bundles.

  • Note, this still allows you to bundle with transactions that aren’t your own (i.e. that you did not sign).
🀝 With our Helper Libraries

✍️ You can sign bundles with:

  • skipjs via the signBundle method on the SkipBundleClient
  • skip-python via the sign_bundle method or the combined sign_and_send_bundle method
🧠 Without our Helper Libraries

To start, you’ll need two things (python will be used for this example):

  • list_of_tx_bytes: This is a list (or array, depending on programming language) of tx_bytes (note: if you get a tx from a mempool, they are in base64-encoded string format, to obtain tx_bytes, simply base64-decode the string).

    list_of_tx_bytes: list[bytes] = [b'<tx_bytes>', b'<tx_bytes']
  • priv_key: This is an object in your respective programming language that allows for signing with the private key for the secp256k1 digital key scheme (the same private key you’re used to signing transactions with in the Cosmos ecosystem).

    from cosmpy.crypto.keypairs import PrivateKey

    priv_key = PrivateKey(b'<private key bytes>')

    Now, to obtain the correct signature to be sent with your bundle to Skip, you will:

  1. Append the list of tx_bytes together into a single flat bytes array

  2. Hash the flat bytes array with sha256 to obtain a bundle_digest

  3. Sign the bundle_digest with your private key

    from hashlib import sha256

    # Append all the tx_bytes of your bundle into a single array of bytes
    flattened_bundle: bytes = b''.join(list_of_tx_bytes)

    # Create digest of flattened bundle
    bundle_digest = sha256(flattened_bundle).digest()

    # Sign digest of bundle
    bundle_signature = priv_key.sign_digest(bundle_digest)

πŸ“¨ Sending Bundles​

Skip exposes an RPC method for submitting bundles: broadcast_bundle_sync.

🀝 With our Helper Libraries

✍️ You can send bundles with:

  • skipjs via the sendBundle method on the SkipBundleClient
  • skip-python via the send_bundle method or the combined sign_and_send_bundle method
🧠 Without our Helper Libraries
  • For those wanting to learn how to send bundles without using our helper libraries, see below for instructions (note: go and rust helper libraries will be released shortly)πŸ‘‡

    Searchers need to send an http post request to Skip’s RPC URL, which can be found here: β€£, with the follow parameters (txs, desiredHeight, pubkey, signature)

    • txs is a list of individual base64-encoded txs, ordered by how transactions should be ordered in the bundle.
    • desiredHeight is the chain height that of the auction that this bundle will be considered for.
      • πŸš€Β Note, if you set this as 0, Skip will automatically try to include your bundle in the soonest possible auction πŸš€
        • This is a good option if you are bundling with another transaction, which may be committed before your bundle otherwise
      • Also note, you can submit transactions for auctions up to 5 blocks in advance
    • pubkey is the base64-encoded public key associated with the private key that your bundle was signed with (this will be checked by the Skip sentinel).
    • signature is the base64-encoded signature obtained from signing the bundle digest with your private key that corresponds to the pubkey.
      • See Signing Bundles section above for more information on how to generate this signature.
    import httpx

    skip_rpc_url = ""

    txs = ['<b64-encoded-tx>', '<b64-encoded-tx>']
    desired_height = str(0)
    pubkey = '<b64-encoded public key>'
    signature = '<b64-encoded bundle signature>'

    # Create data params
    data = {'jsonrpc': '2.0',
    'method': 'broadcast_bundle_sync',
    'params': [txs,
    'id': 1}

    # Send post request to SKIP RPC with data, get response
    response =, json=data)

πŸ“£ Bundle Submission Responses​

Submitting bundles to the Skip Relay results in a response back from the Relay that informs the searcher about the structure of their bundle and the results from attempting to include the bundle in an auction for a given block height.

πŸ“œ Response Format and Meaning​

{'jsonrpc': '2.0', 'id': 1, 'result':
{'code': <Int: Code for the bundle response, see codes section below for more details>,
'txs': '[<Array of tx hashes of the txs in the bundle>]',
'auction_fee': <Int as String: Fee paid to the auction in the auction denom>,
'bundle_size': <Int as String: Number of Txs in the bundle submitted>,
'desired_height': <Int as String: Block height the bundle attempted inclusion in>,
'waited_for_simulation_results': <Bool: If the bundle waited for simulation results>,
'simulation_success': <Bool: Indicates whether all txs in the bundle succeeded in an on-chain simulation>,
'result_check_txs': '[<ABCI result of calling CheckTx on each transaction, in the same order they were passed in>]',
'result_deliver_txs': '[<ABCI result of simulating each transaction, in the same order they were passed in>]',
'error': '<Error response if an error occured, see codes section below for more details>'}
  • 🚨 Bundle submissions for blocks over two in advance do not simulate immediately, and this response will come before the simulation occurs, therefore simulation_success will be false in the jsonrpc response regardless of whether the simulation succeeded or not.

🚩 Codes and Meaning​

0: The bundle won the auction
1: The pubkey provided could not be translated into an address
2: The bundle signature failed verification
3: The bundle failed in a precheck (tx metadata or the auction for desiredHeight was closed)
4: The desiredHeight proposer is not a Skip validator, therefore there is no auction
5: The bundle failed in CheckTx
6: Deprecated Error Code
7: The bundle was not simulated (this means it arrived too late for a given auction height)
8: The bundle was simulated and some transaction failed in simulation
9: The bundle lost the auction due to being outbid
10: The bundle response did not wait for auction simulation (this means the desired height is too early for auction simulation)
  • πŸ‡ Bundle submission responses are immediate for codes: 1, 2, 3, 4, 5, 7, and 10
  • 🐒 Bundle submission responses are returned after the auction for a desired height concludes if a bundle is valid and is simulated / considered for the auction. This encapsulates error codes: 0, 8, and 9.

πŸ‘ Example Responses​

πŸ‘‘ Code 0: The bundle won the auction
{'jsonrpc': '2.0', 'id': 1, 'result': {'code': 0, 'txs': ['eeb49d472e663571cb809227b5f6cb01dcdc15dc9b06677d39c3c08bdfb87b99'], 'auction_fee': '600', 'bundle_size': '1', 'desired_height': '7333573', 'waited_for_simulation_results': True, 'simulation_success': True, 'result_check_txs': [{'code': 0, 'data': '', 'log': '[]', 'info': '', 'gas_wanted': '100000', 'gas_used': '57035', 'events': [], 'codespace': ''}, {'code': 0, 'data': None, 'log': '', 'info': '', 'gas_wanted': '100000', 'gas_used': '0', 'events': [], 'codespace': ''}], 'result_deliver_txs': [{'code': 0, 'data': 'Ch4KHC9jb3Ntb3MuYmFuay52MWJldGExLk1zZ1NlbmQ=', 'log': '[{"events":[{"type":"coin_received","attributes":[{"key":"receiver","value":"juno10g0l3hd9sau3vnjrayjhergcpxemucxcspgnn4"},{"key":"amount","value":"600ujuno"}]},{"type":"coin_spent","attributes":[{"key":"spender","value":"juno1zhqrfu9w3sugwykef3rq8t0vlxkz72vwnnptts"},{"key":"amount","value":"600ujuno"}]},{"type":"message","attributes":[{"key":"action","value":"/"},{"key":"sender","value":"juno1zhqrfu9w3sugwykef3rq8t0vlxkz72vwnnptts"},{"key":"module","value":"bank"}]},{"type":"transfer","attributes":[{"key":"recipient","value":"juno10g0l3hd9sau3vnjrayjhergcpxemucxcspgnn4"},{"key":"sender","value":"juno1zhqrfu9w3sugwykef3rq8t0vlxkz72vwnnptts"},{"key":"amount","value":"600ujuno"}]}]}]', 'info': '', 'gas_wanted': '100000', 'gas_used': '70548', 'events': [], 'codespace': ''}, {'code': 0, 'data': 'Ch4KHC9jb3Ntb3MuYmFuay52MWJldGExLk1zZ1NlbmQ=', 'log': '[{"events":[{"type":"coin_received","attributes":[{"key":"receiver","value":"juno1lzhlnpahvznwfv4jmay2tgaha5kmz5qx292dgs"},{"key":"amount","value":"50ujuno"}]},{"type":"coin_spent","attributes":[{"key":"spender","value":"juno10g0l3hd9sau3vnjrayjhergcpxemucxcspgnn4"},{"key":"amount","value":"50ujuno"}]},{"type":"message","attributes":[{"key":"action","value":"/"},{"key":"sender","value":"juno10g0l3hd9sau3vnjrayjhergcpxemucxcspgnn4"},{"key":"module","value":"bank"}]},{"type":"transfer","attributes":[{"key":"recipient","value":"juno1lzhlnpahvznwfv4jmay2tgaha5kmz5qx292dgs"},{"key":"sender","value":"juno10g0l3hd9sau3vnjrayjhergcpxemucxcspgnn4"},{"key":"amount","value":"50ujuno"}]}]}]', 'info': '', 'gas_wanted': '100000', 'gas_used': '70536', 'events': [], 'codespace': ''}], 'error': ''}}
⏭️ Code 4: The desiredHeight proposer is not a Skip validator, therefore there is no auction
{'jsonrpc': '2.0', 'id': 1, 'result': {'code': 4, 'txs': None, 'auction_fee': '0', 'bundle_size': '1', 'desired_height': '7333048', 'waited_for_simulation_results': False, 'simulation_success': False, 'result_check_txs': None, 'result_deliver_txs': None, 'error': "Don't have skip validator up next"}}
πŸ€·β€β™€οΈ Code 9: The bundle lost the auction due to being outbid
{'jsonrpc': '2.0', 'id': 1, 'result': {'code': 9, 'txs': ['a6e23c8b8224deee168ff06331e67abaaa47dea10a4a0b75610a66987b45be3d'], 'auction_fee': '600', 'bundle_size': '1', 'desired_height': '473605', 'waited_for_simulation_results': True, 'simulation_success': False, 'result_check_txs': [{'code': 0, 'data': '', 'log': '[]', 'info': '', 'gas_wanted': '100000', 'gas_used': '60388', 'events': [], 'codespace': '', 'sender': '', 'priority': '0', 'mempoolError': ''}, {'code': 0, 'data': None, 'log': '', 'info': '', 'gas_wanted': '0', 'gas_used': '0', 'events': [], 'codespace': '', 'sender': '', 'priority': '0', 'mempoolError': ''}], 'result_deliver_txs': [], 'error': 'bundle did not win auction'}}

πŸ‘©β€βš–οΈ Validator Preferences​

Skip Select allows validators running mev-tendermint to have preferences over the bundles that are included in the blocks they propose.

πŸ›‘ πŸƒβ€β™‚οΈ Frontrun-Protect​

  • Currently, the only preference that impacts searchers is the Frontrun-Protect preference, which disallows bundles that may frontrun or sandwich a transaction not signed by the searcher.
  • Frontrun-Protect is turned on on all validators running mev-tendermint at the moment. Sorry sandwichers.
βœ… Allowed Bundles (with frontrun-protect)

Allowed Bundles

❌ Disallowed Bundles (with frontrun-protect)

Anything not in allowed bundles above is disallowed by validators with frontrunning protection on. See examples of disallowed bundles below.

Disallowed Bundles