Module prefix 

Schema-version prefix (CACHE-003).

Every cache key incorporates a two-byte prefix before its other components: a chapter_revision byte and a hash_function_id byte. The two bytes are kept distinct so the cross-product of chapter revisions and hash functions yields a unique prefix for every pair. Combining them via XOR or addition before hashing is a normative violation (CACHE-003).

Constants

CHAPTER_REVISION

Revision of the cache-key composition rules in docs/spec/09-caching.md.

Functions

hash_function_id

The single byte identifying algo in the cache-key prefix, matching the registry in CACHE-002.

schema_version_prefix

The two-byte schema-version prefix for algo.