Implementing a custom gas model directly in a Sui dApp is not currently possible in the same way it might be on other networks like Substrate or Cosmos. In Sui, gas metering and fees are enforced by the protocol itself, and smart contract developers cannot override or define custom gas pricing for specific modules or functions at the Move level.

However, you can simulate a custom gas model at the application level, by designing your Move modules and off-chain logic to penalize or restrict actions based on resource usage patterns, or by introducing custom fee structures through token burns or transfer mechanisms within your contracts. For example, you could require users to lock or burn a dApp-native token as a form of "fee" before allowing function access.

On the execution side, use sui client dry-run or RPC simulations to analyze actual gas costs for different transaction types. You can then use this data to create tiered service models, reward mechanisms, or discounts based on user holdings or roles.

True protocol-level custom gas models would require modifying the Sui core code and running a custom fork or localnet, which is only feasible for advanced protocol developers or testing experimental mechanics. For dApp builders on Testnet or Mainnet, the best approach is to design smart contract logic and UI behavior around existing gas rules, and optionally introduce off-chain metering logic that mimics a custom gas framework.

Implementing a custom gas model in a Sui dApp can be quite powerful, as it allows you to tailor the gas cost calculations based on the specific operations or features in your decentralized application. However, as of now, Sui doesn't provide native support for custom gas models directly through the Sui network. That said, you can still simulate or approximate a custom gas model in your dApp by implementing custom logic at the application layer or using smart contracts.

Steps to Implement a Custom Gas Model in a Sui dApp

1. Understanding the Gas Model in Sui

• Gas in Sui: In Sui, gas is paid for transactions based on the resources consumed by the transaction, including computation, data storage, and execution. Sui uses a pay-per-use model where the cost is determined by the computational steps taken and the number of resources accessed or modified.
• Gas is Tied to Objects: The amount of gas consumed is typically proportional to the number of objects read or modified during a transaction. For example, if you modify a large number of objects or perform expensive operations, it will consume more gas.

2. Workaround for Custom Gas Model

While Sui doesn’t allow changing the core gas model directly, you can simulate or approximate a custom model using the following techniques:

• Track Gas Usage in Your Application: Implement tracking in your application to monitor how many operations or objects the user is interacting with, and estimate the cost based on your own custom logic. For example, you can assign a cost per transaction or object interaction that the user performs.

  module MyDApp {
      use sui::coin::{self, Coin};
      use sui::transaction::{self, Transaction};
  
      public fun custom_gas_model_operation(
          user: &mut address,
          data: vector<u8>
      ) {
          let operation_cost = calculate_custom_gas_cost(data);
          let coins = Coin::withdraw(user, operation_cost);
          // Perform the main operation
      }
  
      fun calculate_custom_gas_cost(data: vector<u8>): u64 {
          // Example logic: gas cost is based on the length of the data (or size of the operation)
          return 10 * Vector::length(data); // Arbitrary cost calculation
      }
  }
  

• Custom Gas Cost Calculation: You can define your own function to calculate the gas cost. For example, the cost can vary based on the size of the data, number of objects modified, or even the complexity of the logic executed. Then, in the transaction, you can withdraw that amount from the user’s account or another source.

• Estimate Gas in Your Frontend: While interacting with the Sui network from your frontend, you can make an estimation of the gas cost by simulating the transaction in your dApp before submitting it. You can simulate how many objects and operations are involved, and then apply your custom logic to calculate the estimated cost.

• Override Gas in Contract Calls: For specific operations in your smart contracts, you can include gas cost information as part of the transaction’s metadata or inputs and then include logic to ensure that users are aware of the cost before executing the operation.

3. Custom Transaction Fees (Off-Chain Approach)

• Off-Chain Handling: While Sui’s gas system is enforced on-chain, you could also implement custom gas models in your dApp’s frontend and handle the "payment" logic off-chain. For instance, you could charge users a custom fee based on the transaction’s complexity before sending them to the blockchain. This is a way to simulate custom gas handling without directly modifying Sui’s on-chain gas model.

4. Using Sui CLI for Testing Custom Gas Logic

• You can test custom gas models locally using the Sui CLI. This will help you see how your gas usage changes with different types of operations or data sizes.

  Example command for testing:

  sui move run --function custom_gas_model_operation --args "user_address" "data_vector" --network testnet
  

5. Dealing with Gas Limits

• Gas Limitations: Be mindful that any custom gas model should still operate within the standard transaction and block limits that Sui imposes. If your custom model calculates gas to exceed these limits, the transaction will fail.

• Transaction Limits: When building your dApp, ensure that the operations you perform within a transaction do not exceed the gas cap, which is set by the network.

Example of a Basic Custom Gas Model in Move

Here’s an example of a simple Move module that implements a custom gas model based on the size of data:

module CustomGasModel {
    use sui::coin::{Coin, transfer};
    
    // Function to simulate a custom gas model and deduct custom gas cost
    public fun custom_gas_operation(user: &mut address, data: vector<u8>) {
        let gas_cost = calculate_custom_gas_cost(data);
        let coins = Coin::withdraw(user, gas_cost);
        
        // Implement main logic here
        // For example: updating an object, performing a transfer, etc.
    }

    // Custom gas cost based on the length of the input data
    fun calculate_custom_gas_cost(data: vector<u8>): u64 {
        return 10 * Vector::length(data); // Example: cost per byte in the vector
    }
}

6. Deploying and Testing

• Once you have implemented your custom gas model in Move, you can deploy and test it on the Sui Testnet using the CLI:

  sui move publish --package-path /path/to/package --network testnet
  

• Then, use the CLI or SDK to call your contract and simulate transactions to observe the custom gas costs.

Important Considerations

• Security: Be cautious with custom gas models as they might be exploited or result in incorrect gas calculations. Make sure your model is predictable and transparent to users.
• Gas Limits: Ensure your custom gas calculations do not push transactions beyond the network's imposed limits.
• Testing: Extensively test on the Testnet or Localnet to simulate real-world scenarios and avoid running into unexpected costs or failures.

Conclusion

While Sui doesn’t directly support altering the core gas model, you can implement a custom gas model at the application layer by simulating gas costs in Move and calculating custom charges based on the operations in your dApp. This approach provides flexibility, but you should keep in mind the network's native constraints and ensure you’re not violating them. Always test thoroughly on the Testnet before going to production.

Implementing a custom gas model for a Sui dApp is a very interesting and advanced use case, but as of now, Sui's gas model is primarily controlled by the Sui runtime and validator consensus. However, there are some ways you can experiment with different aspects of gas management and optimize your dApp's behavior when interacting with the gas system on Sui.

Key Points:

1. Gas Model in Sui:

   • Sui uses a single global gas pool for all transactions. The gas price is determined by the validators, and users need to pay gas in SUI tokens for executing transactions and interacting with the blockchain.
   • Gas fees in Sui are based on the operations (move calls, object mutations, etc.) and their respective gas cost. However, there is currently no way to directly change the core gas model (e.g., gas rate determination) for the entire network via custom logic in your dApp.

2. Experimenting with Gas Logic for Your dApp: While you can’t directly modify the global gas model, you can optimize gas usage and experiment with different aspects in your dApp's smart contracts, specifically the gas cost of your Move functions and how your dApp interacts with gas fees. Here are a few ways to experiment:

1. Custom Gas Estimation for Move Functions

• Overview: You can estimate gas for specific functions in your dApp and provide feedback to users based on the operations you're performing.

• How:

  • Use Move functions with custom cost optimizations: In your Move modules, ensure that the functions you're writing are optimized for lower gas consumption.
  • Estimate gas upfront: Use Sui’s CLI or SDK to estimate the gas before executing the transaction and provide an estimate to the user.

  const gasBudget = 10000;  // Example gas budget for a transaction
  const txn = new TransactionBlock();
  txn.moveCall({
    target: '0x2::coin::transfer',
    arguments: [txn.pure(sender), txn.pure(receiver), txn.pure(amount)],
  });
  
  // Estimate gas using the `simulateTransaction` function
  const gasEstimate = await suiClient.simulateTransaction(txn);
  console.log(`Estimated gas: ${gasEstimate.gasUsed}`);
  

  You can adjust the gas budget based on the operations within your dApp and monitor the gas consumption.

2. Custom Gas Tracking in Your dApp Logic

• Overview: You can implement custom logic in your dApp to track gas usage and warn users when a transaction might be too expensive or exceeds certain thresholds.

• How:

  • Track gas costs programmatically by estimating the gas before sending transactions.
  • Customize your front-end logic to adjust the gas budget dynamically, providing a better experience for users based on the complexity of the transaction.

  const txn = new TransactionBlock();
  txn.moveCall({
    target: '0x2::coin::transfer',
    arguments: [txn.pure(sender), txn.pure(receiver), txn.pure(amount)],
  });
  
  const gasEstimate = await suiClient.simulateTransaction(txn);
  if (gasEstimate.gasUsed > maxGasLimit) {
    alert('This transaction exceeds the gas budget limit');
  } else {
    // Proceed with the transaction
    const result = await suiClient.submitTransaction(txn);
  }
  

  This allows you to provide a custom gas model by interacting with the gas fee structure dynamically based on your dApp's specific needs.

3. Transaction Fee Subsidization (Custom Logic on Frontend)

• Overview: You can experiment with fee subsidization in your dApp by having your front-end cover the gas fee, or by dynamically adjusting how fees are paid.

• How: You could create a logic where users don't directly pay for gas, and instead, your dApp subsidizes the cost of gas. For instance, if you're building a platform for users to perform transactions, you could cover the gas fees as part of your business model.

  Example: In some use cases, you might want to abstract the gas costs from the users:

  const txn = new TransactionBlock();
  txn.moveCall({
    target: '0x2::coin::transfer',
    arguments: [txn.pure(sender), txn.pure(receiver), txn.pure(amount)],
  });
  
  // Cover the gas fees for the user
  const gasCost = await suiClient.getGasEstimate(txn);
  const totalCost = gasCost + amount; // Add gas cost to the total
  
  // Proceed with the transaction as the dApp covers the gas
  await suiClient.submitTransaction(txn, { feePayer: dAppWallet });
  

  This approach allows you to abstract gas costs for the users, but it doesn’t directly modify the Sui gas model itself.

4. Monitor and Optimize Gas Usage in Your Modules

• Overview: Within your Move modules, reduce gas usage by optimizing your code and minimizing computational overhead. The simpler the contract logic, the lower the gas consumption.

• How:

  • Avoid unnecessary state changes or lookups.
  • Avoid complex loops or recursive calls in Move functions.
  • Optimize smart contract logic to be as efficient as possible.

  Example: Instead of a function with a loop that consumes a lot of gas, optimize it:

  public fun add_to_balance(account: &mut Account, amount: u64) {
      let current_balance = Account::balance(account);
      Account::set_balance(account, current_balance + amount);
  }
  

  By ensuring that each function is as efficient as possible, you reduce the overall gas usage for your dApp.

5. Leverage Custom Gas Estimation Tools

• Overview: You can also create or integrate custom gas estimation tools for your Move contract.
• How: Sui provides simulation functions to estimate gas consumption before submitting the transaction. You can integrate these into your UI to provide more accurate predictions.

Example:

const txn = new TransactionBlock();
txn.moveCall({
  target: '0x2::coin::transfer',
  arguments: [txn.pure(sender), txn.pure(receiver), txn.pure(amount)],
});

// Estimate gas usage with `simulateTransaction`
const simulationResult = await suiClient.simulateTransaction(txn);
console.log(`Estimated gas: ${simulationResult.gasUsed}`);

Summary

While you cannot change Sui's core gas model (as it is governed by the validators and consensus), you can optimize how gas is handled and experiment with custom logic in your dApp. Here are some ways you can implement a custom gas model:

1. Estimate and optimize gas usage within Move functions.
2. Track and warn users about high gas usage in your dApp’s front-end.
3. Implement fee subsidization or abstract gas fees from users.
4. Optimize Move code to reduce gas consumption for frequently called functions.
5. Monitor gas costs dynamically and adjust transaction behavior accordingly.

By leveraging these techniques, you can create a more efficient and user-friendly gas model for your Sui dApp, even though the underlying Sui gas model remains constant.

Sui does not currently allow developers to implement a fully custom gas model at the protocol level. Gas metering and fee computation are handled by the Sui protocol itself and apply uniformly to all smart contracts. However, you can simulate a custom gas model at the application level by introducing your own logic for usage tracking or token-based fees inside Move modules. For example, you can require users to pay with a dApp-specific token, enforce balance checks, or consume units from a custom “usage credit” object. You can also track function call counts or transaction volume per user using internal counters. This logic won’t override actual Sui gas costs but can add a custom pricing layer. Be sure to clearly communicate the model to users since it adds overhead beyond standard gas fees. On the frontend or backend, you can estimate real gas costs using dry run simulations via the Sui SDK. You should avoid designing patterns that rely on refunds or rebate logic since Sui does not support post-execution gas adjustments. For advanced experiments, running a forked localnet with protocol modifications is possible but not recommended for production.

1. Understand Sui's Gas Basics

Sui's gas model has 3 components:

struct GasCostSummary {
    computation_cost: u64,
    storage_cost: u64,
    storage_rebate: u64
}

2. Custom Gas Strategies

Option A: Prepaid Gas (Fixed Cost)

module my_dapp::fixed_gas {
    use sui::tx_context;
    use sui::coin;
    use sui::balance;

    struct FixedGasFee has store {
        amount: u64
    }

    public entry fun execute_with_fee(
        fee: &mut FixedGasFee,
        payment: coin<SUI>,
        ctx: &mut tx_context::TxContext
    ) {
        let gas_balance = coin::into_balance(payment);
        balance::join(&mut fee.amount, gas_balance);
        // Your dApp logic here
    }
}

Option B: Gas Sponsorship

// Frontend implementation
const sponsoredTx = await client.signTransactionBlock({
  transactionBlock: tx,
  sponsor: '0xSPONSOR_ADDRESS'
});

3. Dynamic Pricing Model

module my_dapp::dynamic_gas {
    use sui::math;
    use sui::dynamic_field;

    struct GasOracle has key {
        id: UID,
        base_fee: u64,
        multiplier: u64
    }

    public fun calculate_fee(
        oracle: &GasOracle,
        complexity: u64
    ): u64 {
        math::pow(base_fee, complexity) * multiplier
    }
}

4. Implementation Steps

1. Create a Gas Token Wrapper

module my_dapp::gas_token {
    struct MyGasToken has key, store {
        id: UID,
        // Custom gas fields
    }
}

2. Modify Transaction Flow

// Client-side adjustment
const tx = new TransactionBlock();
tx.setGasPayment([{
  objectId: CUSTOM_GAS_OBJECT_ID,
  version: CUSTOM_GAS_VERSION,
  digest: CUSTOM_GAS_DIGEST
}]);

3. Gas Estimation Endpoint

// Backend service
async fn estimate_gas(tx: Json<TxRequest>) -> Result<GasEstimate> {
    let reference_gas_price = sui_client.reference_gas_price().await?;
    let custom_price = reference_gas_price * config.multiplier;
    Ok(GasEstimate { custom_price })
}

5. Testing Your Model

# Dry-run with custom gas
sui client call --gas-budget CUSTOM_AMOUNT --dry-run

# Monitor with metrics
sui-node --metrics-url 0.0.0.0:9184

Key Considerations

• Storage costs are fixed per Sui's protocol
• Computation costs can be scaled via gas_budget
• For mainnet compliance:
  • Minimum gas must cover storage changes
  • Must use SUI for final settlement

Sui does not allow custom gas models at the dApp level, as gas calculation is a core protocol function handled uniformly across the network. Gas fees are determined by computation, storage, and bandwidth usage, and are paid in SUI. However, you can design economic abstractions in your dApp, such as subsidizing user transactions by paying gas on their behalf using the Sponsorship feature, or implementing a token-based credit system that tracks off-chain usage. These models run on top of Sui’s native gas system but do not replace it. For experimentation, use the Sui SDK to simulate cost models based on transaction complexity and object size.