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KernelFlowDevelopers v1
Approvals & fees
Swap & Bridge/Integration guides
KERNELFLOW / DEVELOPERS

Approvals & fees

Handle allowances and display the quote’s fee-adjusted amounts correctly.

EVM token approvals

On ETH, BNB, BASE, AVAXC, XLAYER, and ROBINHOOD, returned transactions call ApproveManager.execute. The user approves ApproveManager rather than a provider contract. Always read the spender and amount from the current quote.

ApproveManager · all six EVM contract chains
0xB0E42E806cb213e811A3af3ebbD49A6743712A21
  1. Read allowance(fromAddress, approval.spender) on approval.token.
  2. If allowance is below approval.amount, have the user approve the required amount and wait for confirmation. Any larger approval is a separate product decision.
  3. Recheck quote expiry after the approval transaction. Fetch a new quote if needed, then sign and submit the trade.

Approvals to another router or provider do not carry over. Native input does not require token approval. On TRX direct quotes, the spender is the provider contract.

Protocol fees

For contract-chain execution, the protocol fee is taken from the input on chain. The configured target rates are 30 bps for same-chain trades and 70 bps for cross-chain trades, with activation varying by chain. SOL and TRX have no protocol fee under the current integration contract.

Fee rollout snapshot, November 6, 2026: active on BNB; scheduled on ETH for November 7, 2026 at 13:30 UTC+08:00; zero on the remaining contract chains until scheduled. This is a dated snapshot, not a live fee feed.