P13-S28 asked for a container property old readers cannot silently
accept and a later commit cannot inherit unchanged. The format major is
that property. FORMAT_MAJOR moves 0 -> 1, FORMAT_MINOR resets to 0, and
the decoder stops being exact-major-only: it classifies three ways
through a named FormatEpoch, deliberately decoding major 0 as legacy.
Old readers already fail closed on an unknown major, so that half needs
no new mechanism — which is why the major is the right carrier and the
header's immutability, fatal to FORMAT_MINOR as a provenance field, is
exactly what makes it sound as an epoch field.
The eight-row matrix carries the rule: a major-0 bundle with no base may
open, one carrying a base is rejected, and one attempting to add a base
is rejected and told to repack. That last row is the non-inheritance
rule. Legacy resolves to hard rejection, never read-only — a
pre-authority base is not a restricted-but-correct view.
Three things the review rounds found, none visible at filing:
It cannot stamp major 1 before S27's writer enforcement exists. Pin 3a
therefore closes both boundaries temporarily — opening a major-1 bundle
already carrying a base, and committing one into it — through a third,
temporary error that names P13-S27 and must not name repack, since a
major-1 container is already the right epoch.
Text projection launders provenance straight through the boundary:
serialize_document stages a carried base into a fresh bundle and
build_manifest writes it. Resolved as symmetric document-level refusal —
projection, parsing, and a new dedicated SerializeError variant. None of
the three existed to be "retained"; an earlier draft claimed otherwise
and was wrong. This forces COMPANION_VERSION to 0.14.0 and rebuilds the
committed corpus to 20 vectors and ten rejection classes, with
canonical_bases reach dropping 2 -> 0. That is a real capability loss
and is stated as one.
Corruption precedence binds in both epochs. A corrupt major-1 base must
still fail as malformed, never as the temporary authority error a user
would reasonably retry on a container that is in fact tampered with.
11 pins, 11 tests, 11 mutations, 15 touch rows, 7 gate items. S27's
contract is a mandatory touch: pin 8 resolves its open pin 2a — legacy
bases are refused by container epoch, never by version arithmetic.
Documentation only. Not implemented, not dispatched. S27 and S16 stay
blocked until this rung lands.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QjsEnYhm1gPpf6ii2iFxFV
Levi Neuwirth
8bb917d7c3