[bug] baseAccount connector returns 65-byte signature instead of tx hash from sendTransaction

[remiroyc]

Steps to Reproduce

1. Connect with Coinbase Wallet on a dApp using AppKit v1.8.x
2. The baseAccount connector is used (due to migration in PR feat: base account #5269)
3. User connects with a Smart Wallet (ERC-4337)
4. Call sendTransaction() via wagmi's WalletClient
5. The connector returns a 65-byte ECDSA signature (packed r + s + v) instead of a 32-byte transaction hash
6. Passing this to waitForTransactionReceipt() fails with:

InvalidParamsRpcError: invalid argument 0: hex string has length 130, want 64 for common.Hash

Summary

Related to #5494 — the migration from coinbaseWallet to baseAccount connector (PR #5269) forces all Coinbase users through the Smart Wallet (ERC-4337) path.

Beyond the coinbasePreference option being ignored (as reported in #5494), this also causes a functional regression: sendTransaction() returns a raw signature instead of a transaction hash.

Example response from sendTransaction() (65 bytes / 130 hex chars):

0x03fdfd595361b21b53574b61e8dec99b1840150e1a38440f59b74fef209bb7c1
4e58f33b45a03c90f19685177b6d91cf1a5ad5f5be5408f9f932301f7a4a35b01b

Last byte 0x1b = 27 = v recovery byte, confirming this is a packed ECDSA signature.

Impact on our production dApp: 129 occurrences, 24 users affected over the last 10 days. Transactions are signed on-chain but the dApp cannot track their confirmation — users see an error even though the tx may have succeeded.

List of related npm package versions

@reown/appkit: 1.8.17
@reown/appkit-adapter-wagmi: 1.8.17
wagmi: 2.19.5
viem: 2.45.0

Node.js Version

v22.x

Package Manager

pnpm@10.6.3

[linear]

REOWN-4460

[remiroyc]

Update: root cause traced to @base-org/account SDK

After investigating the Signer.ts source in base/account-sdk, eth_sendTransaction is delegated to the Coinbase wallet popup via sendRequestToPopup(). The popup is supposed to handle the full ERC-4337 flow (create UserOp → submit via bundler → return on-chain tx hash), but it returns a raw 65-byte ECDSA signature instead.

This is not something AppKit can fix at the connector level — the issue is in the response from the @base-org/account SDK / wallet popup.

Opened upstream: base/account-sdk#251

Note: the Preference type in @base-org/account does not have an option to choose between Smart Wallet and EOA (walletUrl, attribution, telemetry, and sub-account settings only). The coinbasePreference option from AppKit's OptionsController is passed as preference.options in the ethers adapter but this field doesn't exist in the SDK type and is likely silently ignored.