Token Approvals

Before settlement, the applicable contract needs permission to move your sell tokens. Call approve() on the ERC-20 token contract for the required amount. This applies to both the RFQ API (router and settlement contracts) and Aggregation API (balance manager).

Which Contract to Approve

Every quote response includes an approvalTarget field - this is the address you approve. Always use this value rather than hardcoding.

Never hardcode the approval address. Always read approvalTarget from the quote response.RFQ API quotes may return the router contract, settlement contract, or Permit2, depending on the flow.The Aggregation API uses a separate balance manager contract for approvals - it is not the same as the settlement contract.For Aggregation API, approving the settlement contract will lead to loss of funds.

Check Existing Allowance

Before approving, check whether the token already has sufficient allowance. This avoids unnecessary gas spend on redundant approval transactions.

from web3 import Web3

ERC20_ABI = [
    {
        "constant": True,
        "inputs": [
            {"name": "_owner", "type": "address"},
            {"name": "_spender", "type": "address"},
        ],
        "name": "allowance",
        "outputs": [{"name": "", "type": "uint256"}],
        "type": "function",
    },
    {
        "constant": False,
        "inputs": [
            {"name": "_spender", "type": "address"},
            {"name": "_value", "type": "uint256"},
        ],
        "name": "approve",
        "outputs": [{"name": "", "type": "bool"}],
        "type": "function",
    },
]

w3 = Web3(Web3.HTTPProvider("https://eth.llamarpc.com"))

def check_allowance(owner: str, token_address: str, spender: str) -> int:
    token = w3.eth.contract(
        address=Web3.to_checksum_address(token_address),
        abi=ERC20_ABI,
    )
    return token.functions.allowance(
        Web3.to_checksum_address(owner),
        Web3.to_checksum_address(spender),
    ).call()

Approve if Needed

If the current allowance is less than the trade amount, submit an approval transaction. Most integrators approve the maximum amount (2^256 - 1) so they only need to do this once per token.

from eth_account import Account

PRIVATE_KEY = "0x<your_private_key>"

def ensure_allowance(account, token_address: str, spender: str, required: int):
    current = check_allowance(account.address, token_address, spender)
    if current >= required:
        return  # already approved

    token = w3.eth.contract(
        address=Web3.to_checksum_address(token_address),
        abi=ERC20_ABI,
    )

    tx = token.functions.approve(
        Web3.to_checksum_address(spender),
        2**256 - 1,  # max approval
    ).build_transaction({
        "from": account.address,
        "nonce": w3.eth.get_transaction_count(account.address),
        "gasPrice": w3.eth.gas_price,
    })

    signed = w3.eth.account.sign_transaction(tx, private_key=PRIVATE_KEY)
    tx_hash = w3.eth.send_raw_transaction(signed.raw_transaction)
    w3.eth.wait_for_transaction_receipt(tx_hash, timeout=120)

Using It with Quotes

After receiving a quote from either API, check and approve before signing and broadcasting:

quote = response.json()

sell_token = list(quote["sellTokens"].keys())[0]
sell_amount = int(quote["sellTokens"][sell_token]["amount"])
approval_target = quote["approvalTarget"]

account = Account.from_key(PRIVATE_KEY)
ensure_allowance(account, sell_token, approval_target, sell_amount)

# Now proceed to sign and broadcast...

Approval Strategies

Max approval (recommended for programmatic integrators): Approve 2^256 - 1 once per token. Saves gas on subsequent trades since you never need to re-approve. This is the standard approach for solvers and aggregators. Exact approval: Approve only the exact trade amount each time. More conservative, but costs gas on every trade. Some compliance-sensitive integrations prefer this.

Approval type

The public RFQ and Aggregation APIs use approval_type=Standard. For BebopRouter trades, see Permit2 for self-execution. Always approve the approvalTarget from the current quote.

Introduction

Core Concepts

RFQ API

BopAMM

Aggregation API

Price API

Trade History API

Which Contract to Approve

Check Existing Allowance

Approve if Needed

Using It with Quotes

Approval Strategies

Approval type

​Which Contract to Approve

​Check Existing Allowance

​Approve if Needed

​Using It with Quotes

​Approval Strategies

​Approval type

Which Contract to Approve

Check Existing Allowance

Approve if Needed

Using It with Quotes

Approval Strategies

Approval type