D004 - One import hash, pinned by an external fixture

Status: decided Date: 2026-09-26

The import hash has one implementation, selfish-nid, used by the probe and the emulator alike. tests/known-pairs.txt pins it with name and encoding pairs taken from the resolution logs of independent open-source implementations, checked in both directions with the count asserted.

Why: a probe sharing the loader's hash cannot detect a wrong hash by agreement, which is the argument for two implementations. A fixture produced elsewhere answers it better: it constrains the suffix, byte order, alphabet and packing against implementations nobody here wrote.

Rejected:

• Two independent implementations: they can agree with each other and both be wrong.
• One implementation with no external fixture: nothing outside the repository checks it.