Callisto Bridge Fee Enhancement

Project Title:

Callisto Bridge Fee Enhancement


This document is a concept proposal. The key takeaway of the recommendation is to support a process to provide fees for cross-chain transactions on Callisto Bridge. Callisto Bridge will provide the needed amount to complete a cross-chain swap and charge a small service fee.

Current Situation:

The Callisto Bridge currently supports transfer from 3 main chain types Ethereum, Binance, and Callisto Network. To make a transaction and exchange currency from one chain to the other, you need to have the base currency in both specific chains to cover fees to complete the transaction. These fees vary based on the chains and the number of coins transacted. An individual may or may not have the required currency available, which adds additional steps to bridge coins from one chain to another.

Project Goal:

The feature intends to simplify the fee process needed to complete a transaction on the Callisto Bridge when the user has at least one of the required fund types to complete the transaction.

Functional Overview:

Fees deducted from the currencies bridged will allow completion of the transaction without sourcing appropriate fee coins outside of the process. Adding this enhancement will simplify and improve the user experience. Allowing Callisto Bridge to provide the fee amount will necessitate a charge for the cost of the fee and an additional processing fee. Transactions that have the available funds would act as they currently do.


  • Simplifies the user experience using Callisto Bridge
  • Promotes increased use of the Callisto Bridge
  • Can result in incremental fees used to fund the fee wallets and the treasury


  • There will be limits to the size of transactions based on available required Bridge fees.
  • There will need to be additional development to support the feature, and there is no guarantee Callisto Bridge usage will cover the development cost.
  • Potential security risks for the Callisto Bridge and the user

Proposed Development:

  • Develop updated UI to provide options for users to select and agree to fees to be charged for a Callisto Bridge transaction.
  • Develop a process for funding of appropriate fee amount/s based on the requested transaction.
  • Create wallets to send and receive fee funds
  • Develop a process to sweep fee fund wallets for excess funds.

Methodology (AKA How does this work):

Functionally the Callisto Bridge interface is the same with the addition of additional steps to determine:

  1. Does the user want the Callisto Bridge to provide native chain fees funds to support transactions? (Callisto, Binance, or Ethereum)
  2. A function that identifies the appropriate fee is not available to complete the transaction redirects to #1 above.
  3. Error message screens that support appropriate error states:
  • Not supported at this time
  • Insufficient funds
  • Cannot exchange the funds for the same funds
  • Transaction fee/s is/are above X limit (Please lower the bridge amount to be exchanged).

Example: Bridge ccBNB to BNB (The user has no BNB token)

  1. The user enters the amount of ccBNB to bridge to BNB.
  2. Callisto Bridge prompts the user to provide funds if no funds are available in the requested bridge pair; there is an added option selection to fund fees (with appropriate disclaimers and fee disclosures)
  3. The user chooses to have the Callisto Bridge provide the needed funds in this case (BNB) and acknowledges the fee and service charge.
  4. The projected fee amount is deposited into their Metamask wallet to cover fees. (Fees funded from the currency submitted for bridging in this case ccBNB)
  5. Callisto Bridge prompts the user to complete the transaction.

Note: Developed support for all Callisto Bridge currency pairings will provide the most options for users. However, not all pairings need to be activated. For example, given the high fee for Ethereum, the Development Team could have a backend setting to turn off/on a specific pairing as needed.


  • Development by the Callisto Development Team


  • Testing funded and conducted by Callisto Security/Callisto Development Team


  • Funded by the Callisto Enterprise CLOE

Created and Submitted By:



I second this motion. I think there should be bith options, either provide your own to cover fees (existing way), or have an option to take a slightly larger fee from your existing chain instead of having to have both. I understand this would likely add extreme complexity to the code and could also be buggy. I hate sounding like a typical end user but I’m just relating some Quality Assurance for you all. The first time I ever used the bridge just to play with it, I had to go to one of my other wallets/exchanges, send to Binance to buy BNB, then send the BNB to my wallet to cover my fees to get to Pancake. Now, once over there obviously you’re likely good for a while, depending on how much you sent. However, had there been the second option to pay a little more on the Callisto Chain for the bridge to cover my fees on the Smart Chain, I totally would have done it. By the time you count the time it took and the other fees I paid just to get BNB to my SC wallet, it would likely cost less just to pay a fee (tax) to Callisto for covering my fees.

Appreciate the comments. I agree I was in the same boat. Areas that do not have easy access to Binance based currency will struggle and vice versa for those that do not have CLO or Eth.

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