Magic Bytes & Constants

Magic Bytes

Every Vein binary starts with the magic bytes 0x4C, 0x44 — the ASCII characters "LD" (short for Lode Data).


Offset 0: 0x4C ('L')
Offset 1: 0x44 ('D')

The decoder validates these bytes before attempting to parse. If they don’t match, it throws:


Invalid magic: expected 0x4C44 ("LD"), got 0x<actual>

Constant	Value	Description
`MAGIC[0]`	`0x4C`	First magic byte (`'L'`)
`MAGIC[1]`	`0x44`	Second magic byte (`'D'`)
`HEADER_SIZE`	`4`	Total header size: magic(2) + version(1) + count(1)
`FIELD_HEADER_SIZE`	`4`	Per-field header: field_id(1) + type_tag(1) + length(2)


application/x-vein

Used as the Content-Type when serving Vein binaries over HTTP.


X-Lode-Fingerprint: <64-char hex SHA-256>

Custom HTTP header for transmitting the fingerprint alongside a Vein binary response.

Used in prompt contracts:

Constant	Value	Description
`DEFAULT_TOKEN_LIMIT`	`1,000,000`	Default token budget per request
`MAX_TOKEN_LIMIT`	`10,000,000`	Hard ceiling for any request