Registries and plugin discovery

Capability modules extend httk₂ by shipping small registration packages under the reserved httk.registry.<tier>.<module> namespaces (cli, entries, io, schemas). Discovery imports them eagerly at import httk.core; they record lazy references ("module:callable"), so nothing heavy loads until first use.

The registry you will meet first is the reader registry behind httk.core.load, which dispatches on file extension or exact basename (case-insensitively, with transparent decompression):

from httk.core import load, register_reader

register_reader(
    name="demo",
    reader="example_package.readers:read_demo",
    extensions=(".demo",),
    filenames=("DEMOCAR",),
)
load("sample.demo.gz")   # decompressed, then dispatched to read_demo

The same shape repeats across the system — register with a lazy reference, consume through a neutral entry point:

• readers / writers and format adapters/serializers (load, save);

• entry providers, records, and families — described, queryable data for storage and serving;

• schema definition resources — vendored OPTIMADE definition documents;

• CLI commands, definition prefixes, compression codecs, leaf codecs, coercers, and canonical encoders (content addressing, including canonical format v2).

For each registry’s exact API, matching rules, save semantics, and the discovery contract, see Registries and plugin discovery in detail.