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Case Study: WAGMI Upgrade

This case study uses WAGMI Subnet upgrade to show how a network upgrade on an EVM-based (Ethereum Virtual Machine) Subnet can be done simply, and how the resulting upgrade can be used to dynamically control fee structure on the Subnet.


Subnet-EVM aims to provide an easy to use toolbox to customize the EVM for your blockchain. It is meant to run out of the box for many subnets without any modification. But what happens when you want to add a new feature updating the rules of your EVM?

Instead of hardcoding the timing of network upgrades in client code like most EVM chains, requiring coordinated deployments of new code, Subnet-EVM v0.2.8 introduces the long awaited feature to perform network upgrades by just using a few lines of JSON in a configuration file.


The WAGMI ("We're All Going to Make It") Subnet Demo is a high throughput testbed for EVM optimizations. It is parameterized to run at a factor more capacity than Fuji/Mainnet C-Chain and will be used to experiment with release candidates before they make it into an official coreth release.

Network Parameters

  • Network ID: 11111
  • Chain ID: 11111
  • Block Gas Limit: 20,000,000 (2.5x C-Chain)
  • 10s Gas Target: 100,000,000 (~6.67x C-Chain)
  • Min Fee: 1 GWei (4% of C-Chain)
  • Target Block Rate: 2s (Same as C-Chain)

You can check out the Genesis file of WAGMI Subnet to see the initial configuration.

Network Upgrades: Enable/Disable Precompiles

Detailed description of how to do this can be found in Customize a Subnet tutorial. Here's a summary:

  • Network Upgrade utilizes existing precompiles on the Subnet-EVM:
    • ContractDeployerAllowList, for restricting smart contract deployers
    • TransactionAllowList, for restricting who can submit transactions
    • NativeMinter, for minting native coins
    • FeeManager, for configuring dynamic fees
  • Each of these precompiles can be individually enabled or disabled at a given timestamp as a network upgrade, or any of the parameters governing its behavior changed.
  • These upgrades must be specified in a file named upgrade.json placed in the same directory where config.json resides: {chain-config-dir}/{blockchainID}/upgrade.json.


To prepare for the WAGMI network upgrade, on 08/15/2022, we had announced on Twitter and shared on other social media such as Discord, with the following information:

With subnet-evm v0.2.8 It's time for a whole new Subnet Season: Network Upgrade Edition.

Like every great show, we're kicking this season off with a pilot episode: WAGMI Network Upgrade.

Stay tuned because this pilot is literally a can't miss for every WAGMI node 😉

The upgrade will activate the fee config manager, and enable smooth fee config updates in the future

This upgrade changes how blocks are processed on WAGMI, so every WAGMI node needs to upgrade to continue to validate WAGMI correctly.

In order to update your node, you need to update to subnet-evm v0.2.8 and follow the instructions to enable a stateful precompile on subnet-evm here:

You can find the JSON to configure the network upgrade in this gist:

TLDR; you will need to place the JSON file into your node's file directory within chain-config-dir/wagmi blockchainID/upgrade.json and restart your node.

Note: the WAGMI blockchainID is 2ebCneCbwthjQ1rYT41nhd7M76Hc6YmosMAQrTFhBq8qeqh6tt.

Deploying upgrade.json

The content of the upgrade.json is:

"precompileUpgrades": [
"feeManagerConfig": {
"adminAddresses": ["0x6f0f6DA1852857d7789f68a28bba866671f3880D"],
"blockTimestamp": 1660658400

Detailed explanation of feeManagerConfig can be found in the precompiles documentation.

With the above upgrade.json, we intend to change the adminAddresses at timestamp 1660658400:

  • 0x6f0f6DA1852857d7789f68a28bba866671f3880D is named as the new Admin of the FeeManager
  • 1660658400 is the Unix timestamp for 10:00 AM EDT 08/16/2022 (future time when we made the announcement) when the new FeeManager change would take effect.

We place the upgrade.json file in the chain config directory, which in our case is ~/.avalanchego/configs/chains/2ebCneCbwthjQ1rYT41nhd7M76Hc6YmosMAQrTFhBq8qeqh6tt/. After that, we restart the node so the upgrade file is loaded.

When the node restarts, AvalancheGo reads the contents of the JSON file and passes it into Subnet-EVM. We see a log of the chain configuration that includes the updated precompile upgrade. It looks like this:

INFO [08-15|15:09:36.772] <2ebCneCbwthjQ1rYT41nhd7M76Hc6YmosMAQrTFhBq8qeqh6tt Chain> Initialised chain configuration
config=“{ChainID: 11111 Homestead: 0 EIP150: 0 EIP155: 0 EIP158: 0 Byzantium: 0
Constantinople: 0 Petersburg: 0 Istanbul: 0, Muir Glacier: 0, Subnet EVM: 0, FeeConfig:
“:10000000,\“blockGasCostStep\“:500000}, AllowFeeRecipients: false, NetworkUpgrades: {\
“subnetEVMTimestamp\“:0}, PrecompileUpgrade: {}, UpgradeConfig: {\“precompileUpgrades\“:
Engine: Dummy Consensus Engine}”

We note that precompileUpgrades correctly shows the upcoming precompile upgrade. Upgrade is locked in and ready.


When the time passed 10:00 AM EDT 08/16/2022 (unix timestamp 1660658400), the upgrade.json had been executed as planned and the new FeeManager admin address has been activated. From now on, we don't need to issue any new code or deploy anything on the WAGMI nodes to change the fee structure. Let's see how it works in practice!

Using Fee Manager

The owner 0x6f0f6DA1852857d7789f68a28bba866671f3880D can now configure the fees on the Subnet as they see fit. To do that, all that's needed is access to the network, the private key for the newly set manager address and making calls on the precompiled contract.

We will use Remix online Solidity IDE and the Core Browser Extension. Core comes with WAGMI network built-in. Metamask will do as well but you will need to add WAGMI yourself.

First using Core, we open the account as the owner 0x6f0f6DA1852857d7789f68a28bba866671f3880D.

Then we connect Core to WAGMI, Switch on the Testnet Mode in Advanced page in the hamburger menu:

Core testnet mode

And then open the Manage Networks menu in the networks dropdown. Select WAGMI there by clicking the star icon:

Core network selection

We then switch to WAGMI in the networks dropdown. We are ready to move on to Remix now, so we open it in the browser. First, we check that Remix sees the extension and correctly talks to it. We select Deploy & run transactions icon on the left edge, and on the Environment dropdown, select Injected Provider. We need to approve the Remix network access in the Core browser extension. When that is done, Custom (11111) network is shown:

Injected provider

Good, we're talking to WAGMI Subnet. Next we need to load the contracts into Remix. Using 'load from Github' option from the Remix homescreen we load two contracts:

IFeeManager is our precompile, but it references the IAllowList, so we need that one as well. We compile IFeeManager.sol and deploy at the precompile address 0x0200000000000000000000000000000000000003 used on the Subnet.

Deployed contract

Now we can interact with the FeeManager precompile from within Remix via Core. For example, we can use the getFeeConfig method to check the current fee configuration. This action can be performed by anyone as it is just a read operation.

Once we have the new desired configuration for the fees on the Subnet, we can use the setFeeConfig to change the parameters. This action can only be performed by the owner 0x6f0f6DA1852857d7789f68a28bba866671f3880D as the adminAddress specified in the upgrade.json above.


When we call that method by pressing the transact button, a new transaction is posted to the Subnet, and we can see it on the explorer:


Immediately after the transaction is accepted, the new fee config takes effect. We can check with the getFeeCofig that the values are reflected in the active fee config (again this action can be performed by anyone):


That's it, fees changed! No network upgrades, no complex and risky deployments, just making a simple contract call and the new fee configuration is in place!


Network upgrades can be complex and perilous procedures to carry out safely. Our continuing efforts with Subnets is to make upgrades as painless and simple as possible. With the powerful combination of stateful precompiles and network upgrades via the upgrade configuration files we have managed to greatly simplify both the network upgrades and network parameter changes. This in turn enables much safer experimentation and many new use cases that were too risky and complex to carry out with high-coordination efforts required with the traditional network upgrade mechanisms.

We hope this case study will help spark ideas for new things you may try on your own. We're looking forward to seeing what you have built and how easy upgrades help you in managing your Subnets! If you have any questions or issues, feel free to contact us on our Discord. Or just reach out to tell us what exciting new things you have built!