Unable to trade BTC to ETH when connected to phantom btc wallet

[linear]

When connected to BCT wallet in phantom, a trade of btc to eth just says transaction failed

[Hobie1Kenobi]

Bounty Approach

Root Cause Analysis: The BTC→ETH trade fails when connected via Phantom's BTC wallet because the swap flow likely expects an EVM-compatible signer for the ETH receipt side, but Phantom's BTC wallet context provides a Bitcoin signer instead. The transaction builder needs to handle the cross-chain wallet disconnect — specifically, requesting a separate EVM connection for the ETH output or routing through a trustless swap contract that doesn't require an EVM signature at trade time.

Approach:

1. Reproduce the bug by connecting Phantom BTC wallet and attempting a BTC→ETH swap
2. Trace the transaction flow — identify where the EVM signer assumption breaks (likely in buildTransaction or executeSwap when it tries to sign for the ETH destination)
3. Implement a fix: either prompt the user to connect an EVM wallet for the output, or use a swap path (e.g., THORChain/LiFi) where the destination address is passed as a memo parameter rather than requiring an EVM signature
4. Add proper error handling with a descriptive message instead of a generic "transaction failed"
5. Add E2E/integration tests for cross-chain Phantom BTC wallet trades

Deliverables:

• Bug fix with proper cross-chain wallet handling for Phantom BTC wallet
• Descriptive error messaging for unsupported wallet combinations
• Unit + integration tests covering the BTC→ETH Phantom wallet path
• PR with clear description referencing this issue

ETA: 3–4 days

Payout Address (Base): 0x408f39B19266022FeC03076091e59D1f4f163658