# Card package format

`.bpcard` is a reproducible ZIP archive containing:

- `manifest.json`
- `config.json`
- `checksums.json`
- `signature.json`

The manifest declares identity, version, publisher, kind, lanes, phases,
capabilities, compatible model patterns, state scope, priority, and resource
budgets.

The config contains kind-specific JSON. It cannot name an import path or embed
code. The runtime maps the kind to an audited built-in implementation.

`checksums.json` commits to the exact manifest and config. `signature.json`
contains the Ed25519 public key and signature over the canonical checksum map.
Production deployments can require the signer fingerprint to exist in a local
trust set.

This format is intentionally narrower than a Python plugin system. A small
format that can be enforced is more useful than a broad manifest whose
permissions are ceremonial.

