Error HH604: Error running JSON-RPC server: Missing mix hash

[atodorov]

Hello folks,
trying out the command npx hardhat node --fork https://rpc.cc3-testnet.creditcoin.network --show-stack-traces and getting the error in subject:

npx hardhat node --fork https://rpc.cc3-testnet.creditcoin.network --show-stack-traces
Error HH604: Error running JSON-RPC server: Missing mix hash

HardhatError: HH604: Error running JSON-RPC server: Missing mix hash
    at SimpleTaskDefinition.action (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/builtin-tasks/node.ts:372:17)
    at async Environment._runTaskDefinition (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/internal/core/runtime-environment.ts:359:14)
    at async Environment.run (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/internal/core/runtime-environment.ts:192:14)
    at async main (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/internal/cli/cli.ts:323:7)

    Caused by: ProviderError: Missing mix hash
        at EdrProviderWrapper.request (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/internal/hardhat-network/provider/provider.ts:438:19)
        at async SimpleTaskDefinition.action (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/builtin-tasks/node.ts:146:9)
        at async Environment._runTaskDefinition (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/internal/core/runtime-environment.ts:359:14)
        at async Environment.run (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/internal/core/runtime-environment.ts:192:14)
        at async SimpleTaskDefinition.action (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/builtin-tasks/node.ts:303:44)
        at async Environment._runTaskDefinition (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/internal/core/runtime-environment.ts:359:14)
        at async Environment.run (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/internal/core/runtime-environment.ts:192:14)
        at async main (/home/gluwa/creditcoin-3.0/creditcoin3/docs/smart-contract-development/with-hardhat/node_modules/hardhat/src/internal/cli/cli.ts:323:7)

Reference docs: https://cc3-docs.creditcoin.network/smart-contract-guides/hardhat-smart-contract-development#forking-cc3-evm

I've tried both the publicly available URL as well as running a local archive node and connecting to it - same result.

Note: the chain in question, Creditcoin, is built with Substrate and incorporates an EVM compatibility layer. I have no issues deploying a smart contract and interacting with it for example.

Does anyone have any hints or tips what this could mean before I start going down the rabbit hole of debugging Hardhat's source code?

[kanej]

We have no experience with creditcoin, however having an EVM compatibility layer does not imply you will be able to fork the chain, only that the chain can use the EVM as a runtime for smart contract execution.

We may take a look at this if it affects multiple chains, but we can't promise any timeline right now.

[atodorov]

We have no experience with creditcoin, however having an EVM compatibility layer does not imply you will be able to fork the chain, only that the chain can use the EVM as a runtime for smart contract execution.

Thanks. I had my suspicion that this could be the case.

From what I was able to find out "mix hash" is a field in the Ethereum block header which is probably missing as part of the EVM compatibility layer available for Substrate based chains.

I understand that you cannot make any time commitment. It would be great if you can post more technical details about this in the future though.

[alex-draginski]

Hi @atodorov
Have you been able to solve this issue?
I have same error while forking Substrate-based chain.
However, I have commits from March 28-29, when I was able to fork the same chain without any issues.
That's weird =)

I found out that Hardhat cache has "mixHash":null field when I fork Substrate, and "mixHash":"SOME HEX" when I fork Sepolia, for example.
This is the issue, I guess.

[atodorov]

Have you been able to solve this issue?

No. It wasn't important to make this work so I've given up on it and moved to other unrelated work.

[alcuadrado]

we'll take a look. Thanks for clarifying that this is a regression

[alex-draginski]

@atodorov Found a workaround: works at Hardhat 2.18.1 without errors.

[alcuadrado]

@fvictorio @Wodann this looks like a regression when moving to EDR. We are probably more strict than before with respect to validating the blocks that we fetch from the JSON-RPC during forking.

[fvictorio]

NomicFoundation/edr#516