TokenRegistry

Inherits: Ownable2Step, ITokenRegistry

Title: TokenRegistry

Per-token policy registry for allowlisted execution constraints.

Stores token policies including:

• enabled: whether the token is allowed for payments
• decimals: token decimal places (for display/formatting)
• minPerTx: minimum amount per transaction (0 = no minimum)
• maxPerTx: maximum amount per transaction (0 = no maximum)
• kind: token classification (0 = standard, 1+ = future types)

State Variables

_policies

mapping(address => TokenPolicy) private _policies

Functions

constructor

constructor() Ownable(msg.sender);

isEnabled

function isEnabled(address token) external view override returns (bool);

maxPerTx

function maxPerTx(address token) external view override returns (uint256);

minPerTx

function minPerTx(address token) external view override returns (uint256);

decimals

function decimals(address token) external view override returns (uint8);

setTokenPolicy

Sets the full policy for a token.

function setTokenPolicy(
    address token,
    bool enabled,
    uint8 tokenDecimals,
    uint256 minAmount,
    uint256 maxAmount
)
    external
    onlyOwner;

Parameters

Name	Type	Description
token	address	The token address
enabled	bool	Whether the token is enabled for payments
tokenDecimals	uint8	The token's decimal places (e.g., 18 for most tokens, 6 for USDC)
minAmount	uint256	Minimum amount per transaction (0 = no minimum)
maxAmount	uint256	Maximum amount per transaction (0 = no maximum)

setTokenKind

function setTokenKind(address token, uint8 kind) external onlyOwner;

getTokenPolicy

Returns the full policy for a token.

function getTokenPolicy(address token)
    external
    view
    returns (
        bool enabled,
        uint8 tokenDecimals,
        uint256 minAmount,
        uint256 maxAmount,
        uint8 kind
    );

Parameters

Name	Type	Description
token	address	The token address

Returns

Name	Type	Description
enabled	bool	Whether the token is enabled
tokenDecimals	uint8	The token's decimal places
minAmount	uint256	Minimum amount per transaction
maxAmount	uint256	Maximum amount per transaction
kind	uint8	Token classification

Events

TokenPolicyUpdated

event TokenPolicyUpdated(
    address indexed token, bool enabled, uint8 decimals, uint256 minPerTx, uint256 maxPerTx
);

Errors

InvalidToken

error InvalidToken();

InvalidPolicyBounds

error InvalidPolicyBounds();

Structs

TokenPolicy

UNSUPPORTED TOKEN TYPES The following token behaviours are NOT supported by the amser protocol and must not be registered or used in subscription plans:

• Fee-on-transfer tokens: Permit2 transferFrom uses nominal amounts. Recipients would receive less than the plan price, causing accounting drift and merchant underpayment.
• Rebasing tokens: Balances change between registration and execution, breaking amount assumptions throughout the billing flow. Supported: Standard ERC20 tokens. Recommended: USDC, USDT, DAI, WETH. If adding a new token, verify it does not implement transfer hooks, balance rebasing, or fee deduction mechanisms.

struct TokenPolicy {
    bool enabled;
    uint8 decimals;
    uint8 kind;
    uint256 maxPerTx;
    uint256 minPerTx;
}