# K1601–K1605: versioned read-only superblock

The on-disk superblock is exactly 64 bytes. It contains `TKFS` magic, version 1, zero feature flags, a 512-byte block size, total block count, root inode 1, and a nonzero generation. Reserved bytes must remain zero. A checksum over the first 60 bytes protects the header.

Decode publishes no metadata until magic, version, features, geometry, root identity, generation, reserved bytes, and checksum all pass. A valid checksum does not make an unknown version acceptable. Total blocks must be at least 16 and no larger than the observed device geometry.

The parser and encoder are bounded in-memory models. Reading a superblock from a real block device, upgrading formats, and product release acceptance require separate evidence.