What does not work

Everything below follows from one fact: BKC accounts have no ECDSA key.

Tools

Tool	Status	Why / what to use
Hardhat 2	✅ with @bkc-network-lib/hardhat	the plugin signs writes as Cosmos messages
ethers v6	✅ with BkcSigner	an ordinary ethers Signer
Blockscout verify / hardhat verify	✅	Verify contracts
Foundry (forge create, cast send)	❌ writes · ✅ reads	signs locally with secp256k1; forge build, cast call and cast calldata work
Remix (Injected / MetaMask)	❌ writes	compile in Remix, deploy with Hardhat or the CLI
viem wallet client	❌ writes · ✅ reads	use createBkcEip1193Provider() from the SDK as a custom transport
MetaMask and other ECDSA wallets	❌	cannot hold an ML-DSA account — use the BKC Wallet
Hardhat 3	❌	the plugin targets the Hardhat 2 line

Foundry, Remix and viem could work through a local proxy that decodes a signed Ethereum transaction and re-signs it as a Cosmos message — the same translation the plugin does, on the wire. Ask the BKC team if you need one.

JSON-RPC methods

Method	Behaviour
eth_sendRawTransaction	refused: no ECDSA-signed transaction can be valid
eth_sendTransaction	not served by the node; the SDK/plugin intercepts it client-side
eth_sign, personal_sign, eth_signTypedData_v4	no key to sign with — use ADR-36 signMessage() and the precompile
eth_subscribe("logs"), eth_newFilter	do not include wrapped-call logs — poll eth_getLogs
eth_getLogs over > 10,000 blocks	rejected — page with getLogsPaged() or a block range
debug_*, txpool_*, personal_*	not enabled on the public endpoint (only eth, net, web3)

Behaviour that differs from Ethereum

• receipt.fee is 0. The fee is paid on the Cosmos side; use getEvmTransactionCost().
• Gas figures are larger. An ML-DSA transaction is ~5.5 KB and gas is per byte; budget from bkcChain.baseGasLimit, not Ethereum intuition.
• Gas cannot be simulated for the Cosmos side (--gas auto fails).
• One write at a time per account. call_nonce is the Cosmos sequence; concurrent writes from one account reject each other. The SDK and plugin queue them.
• signer.signMessage() throws. ethers nests the explanation at error.error.message.