assembleTag()

function assembleTag(fields, userInputs, delimiter?): `0x${string}`;

Assembles tag fields into a raw dynamic-bytes hex value.

Each field contributes either its hardcoded value or the corresponding entry from userInputs. Fields are joined with delimiter and UTF-8 encoded. The unpadded result is returned as a 0x-prefixed hex string.

Parameters

Parameter	Type	Default value	Description
fields	TagField[]	undefined	Ordered list of tag field descriptors.
userInputs	Record<string, string>	undefined	Map from field name to user-provided value.
delimiter	string	TAG_DELIMITER	Separator between segments. Set to '' to concatenate fields without any separator. Defaults to TAG_DELIMITER (`’

Returns

`0x${string}`

Throws

If any segment contains non-ASCII characters.

Throws

If any segment contains the delimiter (when delimiter is non-empty).

Throws

If the assembled tag exceeds TAG_MAX_BYTES.

Remarks

The tag is the LOC’s free-form bytes field (max TAG_MAX_BYTES) that associates it with an off-chain purpose — an order id, a campaign — and is read back from the subgraph as LetterOfCreditOrigin.tag. Pass the result as tag on CreateStaticLOCParams or CreateDynamicLOCParams. Values over 32 bytes require a profile bound to LetterOfCredit V3; builders keep legacy formatting for V2-bound deployments during the rollout.

Example

// A partner pins the first segment; the customer fills in the rest.
const fields: TagField[] = [
  { name: 'campaign', value: 'SPRING24' },
  { name: 'orderId' },
];

// Bytes left for user-entered segments: 512 minus fixed values and
// delimiters.
const remaining = TAG_MAX_BYTES - getFixedTagBytes(fields);
if (remaining < 0) {
  throw new Error('fixed segments alone exceed 512 bytes');
}

// "SPRING24|ORD-88213" -> raw dynamic bytes; pass as `tag` on V3
// CreateStaticLOCParams / CreateDynamicLOCParams.
const tag = assembleTag(fields, { orderId: 'ORD-88213' });