The Blueprint artifact (base §6): an immutable, portable, inert statement of intent, decoded and validated through the ONE generic field-registry engine (AgentBlueprintProtocol.Registry) parameterized by this module's 18-member table.

The decode pipeline, in order, each stage fail-closed:

1. Canonicalization.verify/2 on the received bytes — a non-canonical spelling of a byte-identical value denies :non_canonical_bytes BEFORE any semantic read or digest comparison (the canonicality obligation: digests are computed only over exact received bytes, and a re-encode-then-digest shortcut must fail this gate, never verify_content).
2. AgentBlueprintProtocol.Registry.validate/2 against table/0 — closed world (:unknown_member), required members, tag-strict integer typing (the The window-float deny: {:float, f} in an integer-typed core field is :invalid_type here, because only this layer sees the decoder tag the wire cannot carry), enums, cardinalities, and the per-member custom checks (bounded schemas via Schema, signature envelopes via Signature, the extension envelope, the assertion operands).
3. The portability scan (Portability) — full scan over the open regions (extension bodies, bounded-schema documents), value-shape scan over every other string including signature key_id, :forbidden_portable_value.
4. The content-digest comparison — Digest.verify_content/3 over the canonical bytes of the covered members (everything except content_digest, signatures, attestations), :digest_mismatch on divergence.

from_value/1 runs stages 2-3 without canonicality (there are no bytes): structure only, for values that came from verify-ed bytes or for producer-side composition — verify_content_digest/1 is the integrity half and must be called separately for the compose-then-verify flow.

to_value/1 is the identity on the held tagged value, so decode → to_value → encode is a byte-exact fixed point (the quarantine round-trip depends on it). A Blueprint is an inert description: decoding one never authorizes an operation.