The Chapter 4 pitch-space vocabulary lands in epiphany-core as in-memory types
with a real consumer, the built-in catalog as PitchSpaceId -> PositionStructure
data, and the P13-S2 "cmn-12" string guard is replaced -- not preserved beside --
by structural resolution over that catalog. Dispatched as one vertical slice
rather than the plan's three steps, because a Chapter 4 type surface with no
consumer is the shape that produced Staff::default_clef and NOTEHEAD_ANCHORS.
No Codec impls, no struct_codec! additions, no Score/ScoreTuningContext field:
these types stay in memory so Ruling C keeps them free to change. Canonical
bytes are byte-identical -- no golden or fuzz digest moved.
Six of the thirteen built-in pitch spaces are underdetermined by the spec (the
three ji-* generators, and all of maqam-base/gamelan-slendro/gamelan-pelog);
they resolve to None and fail closed at every consumer rather than being
invented. SpellingParameters, whose shape the spec calls an open question, is a
documented zero-field marker for the same reason.
The plan's proof of life -- cmn-24 transposing end-to-end -- held at the core
layer and FAILED one layer up, invisibly to the tranche's own tests.
resolve_transposed_spellings took the transposed 12-TET semitone with a ? before
checking whether any spelling needed it, so the 12-chromatic-only gate refused
every cmn-24 transpose, even one with nothing to spell (measured: NoOp
TranspositionOutOfRange, value untouched). P13-S3-shaped: latent in code, made
reachable the moment the space resolved. Moved the ? to point of use; a
spelling-less cmn-24 now transposes, one with an authored spelling still refuses
(the pre-pass cannot write a 24-chromatic accidental). Two tests, each killed by
a different mutation.
Verified independently of the agent that wrote the core half: the "cmn-12"
string survives only in doc comments and fixtures, not control flow; the
proof-of-life arithmetic (B4 -> natural C5 in cmn-24, chromatic 22, 118 - 120
carrying to octave 5) recomputed by hand; the strictly-increasing third clause
of req:tuning:diatonic-chromatic-mapping mutation-killed; full gate green (fmt,
clippy 0, workspace 0 failed, rustdoc 0, conformance 8/8, requirement counts
unmoved at 212/282/282).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Levi Neuwirth
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