The spec's domain-tag registry reserves a non-canonical MUSCLOID layout tag for
LayoutObjectId derivation (req:layoutir:object-id-derivation, Pass-11 item 2.6),
but it was never realized in code: layout-ir minted provisional, untagged ids and
synthesized objects borrowed MUSCCONF. This wires the ratified derivation.
- epiphany-determinism: add the reserved built-in DomainTag::LAYOUT_OBJECT_ID
(`MUSCLOID`), non-canonical/layout-namespace like FONT_METRICS (following the
SYSTEM_ANOMALY Pass-11 precedent of adding a reserved tag). The tag-enumeration
tests now derive from BUILTINS so they cannot drift; the spelling is locked and
from_bytes resolves it as a non-system builtin.
- layout-ir provenance.rs: all three LayoutObjectId derivations route through
MUSCLOID exactly per the requirement -- single keyed on source.canonical_bytes(),
multiply-manifested on (source, region), synthesized on (source, synthesis_kind,
instance_key); synthesized no longer borrows MUSCCONF. A reference-lock test
pins the derivation and proves it is genuinely domain-separated; another asserts
the three keying schemes do not collide (safe by the discriminant-led,
fixed-width canonical_bytes).
- layout-ir engraving.rs: EngravingDecisionId borrowed MUSCCONF for the same
reason; moved it onto MUSCLOID too, keeping its `engraving-decision` prefix so it
cannot alias a layout-object id within the namespace.
Layout ids are non-canonical (never document state, in no content hash), so this
changed id *values* but no durable or interchanged artifact: the only golden churn
is the data-prov hex in the four render goldens (every changed line is a data-prov;
geometry/structure byte-identical).
Spec/status sync: core_spec.tex descriptive notes (the requirement tail, the
domain-tag registry row, the registry intro, and the revision-history entry) now
say the reference implementation wires MUSCLOID as of P12-I2; MUSCLOID is moved out
of the "deferred to the companions" (not-ratified/provisional) list and given a
non-canonical anchor paragraph after the reference-implementation-locks table.
PASS12_BATCH.md marks P12-I2 resolved; PASS11_RATIFICATION_LOG.md keeps the
historical row with a "superseded by P12-I2" note; layout-ir/DECISIONS.md updates
the ratified-block note, the id bullet, and the open candidate (now RESOLVED).
Full gate green: build, fmt, clippy, 587 tests, conformance scale 1.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Levi Neuwirth
e2d389330d