wire_decode accepts a document only when its MessagePack value equals the
named form wire_encode writes for the decoded value (key order, integer width
and an absent optional field aside), so a positional envelope or invocation, an
integer-array ciphertext, an enum sent as its index and bytes after the
document are refused Encoding through the real carriage. The schema describes
the ciphertext as binary, and a test pins schema and wire agreeing.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>