The last fail-closed entry in the built-in tuning catalog now resolves, leaving
only the compatibility-mapping registry open in Push 4b.
The recorded blocker was wrong. Five places in tuning.rs claimed adaptive
"needs HarmonicContext, which does not exist in Rust". But
req:tuning:adaptive-default-version makes version 1 a pure function of
(position, anchor pitch class) — it ignores concurrent, recent, hints,
parameters, and mode. And two of HarmonicContext's four specified fields are
UNIMPLEMENTABLE: key_context and hints are typed on KeyContext / ContextHint,
which core_spec.tex:4111 leaves undefined deliberately, "so defining them now
would freeze a type surface on a chapter with no consumer". The minimal
one-field shape was not a preference; it was the only implementable one. Each
remaining field arrives with the first function that consumes it.
The real blocker was structural and small: locate_voice returned
(RegionId, StaffId) while key_sequence lives on StaffInstance, so the resolver
threw away the only object that could answer "what key is prevailing here".
No new pitch math. ji_static_5limit_ratios already took a runtime anchor — the
three ji-static-5limit-{C,G,D} built-ins are that one function at anchors
0, 7, 2 — so adaptive v1 is that same call with a derived anchor. Verified as
an identity: adaptive at anchor 0 is bit-identical to ji-static-5limit-C and at
anchor 7 to ji-static-5limit-G, across all seven naturals.
A missing tonal centre is NOT an error. core_spec.tex:3452 mandates C
(chromatic position 0) when none is supplied, so that is a defined default, not
a fail-closed case; a test pins it against a future "fail closed" refactor.
Fail-closed applies to exactly two things: an unregistered
AdaptiveTuningFunctionId (hard error, no fallback) and a TimeAnchor that cannot
be unambiguously ordered against the onset (AnchorNotOrderable, naming the kind
that defeated it). If any KeySignatureChange in a sequence is unorderable the
whole derivation fails, rather than risk skipping the true prevailing signature.
Anchor arithmetic is (7 * fifths).rem_euclid(12), never %: fifths reaches -7 and
% yields a negative pitch class. ChromaticPitchClass is a checked 0..=11 newtype,
so the sign bug cannot degrade into a silently wrong anchor — under mutation it
panics outright. Verified by hand across the whole -7..=7 range, including the
enharmonic collisions (6 and -6 both F#/Gb = 6).
Nothing reaches the wire: TuningResolution is catalog-computed and appears in
neither codec.rs nor textvalue_graph.rs, so TuningResolution::Adaptive and
HarmonicContext are in-memory only and schema major 3 is untouched. Zero Codec
impls added; no vector or golden moved.
Gate: fmt clean, clippy 0, 1311 passed / 0 failed, doc 0, conformance 8/8,
requirement labels 6/6 at 212/282/282. Independently verified: the C default,
static systems ignoring context, statelessness across reordered resolution, and
the 0..=11 invariant. Two mutations killed — rem_euclid -> % and a silent
fallback for an unregistered id.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Levi Neuwirth
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