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Ruling: the operation set absorbs genesis

Ratified 2026-07-24. Resolves spec/PLAN_EDITOR_APP.md §Ruling B blocker (i) — canonical graph-state persistence across genesis and pruning. The evidence is spec/ANALYSIS_GENESIS_PERSISTENCE.md, which stays as analysis; this document is the decision and its constraints.

Execution belongs to the Push-4b-class coordinated spec+core+ops track, not to the editor track. The editor track consumes it and does not block on it (§3.7's standing posture).

1. The decision

Every mutable field of Score becomes operation-authored. The Pass-12 K8 ratification — "genesis is outside the operation set", binary_format.tex:2420 — is reversed. A document is Score::empty(identity) plus its envelope log; the instrument → staff → staff instance → voice → event chain is authorable end to end.

There is no genesis block. No new chunk role, no manifest field, no write-once payload, no immutability rule, and no merge or fail-closed rule for a non-CRDT canonical blob. That machinery was the price of leaving genesis outside the operation set, and this ruling declines to pay it. Genesis becomes the first few operations of an ordinary log, converging under the rules already in force.

Rationale, in one line: genesis state is edited — instruments are added, page geometry is changed, temperaments are chosen — and every alternative made those edits either single-writer, unmergeable, or impossible. Concurrency is a first-order product commitment (§3.4), so the exception was not worth institutionalising in the format.

What was considered and rejected

A — a canonical genesis block. Rejected: it fixes genesis but leaves the music unreconstructable after a prune, and a non-op canonical payload has no merge rule, forcing either single-writer genesis or a fail-closed sync rule. Considered in a staged form (immutable block + settings ops) and rejected once it became clear the block buys nothing that B does not.
C — the canonical base carries graph values. Not rejected — deferred, and still required. See §4.
D — scope-limit T1b. Rejected as a destination; unnecessary as a sequencing device once B is committed to.

2. Scope

Two existing reduction patterns cover the whole tranche. Neither is new semantics; both are templates already proven in reduce.rs.

Settings — LWW field-overwrite, the SetMetadata pattern (reduce.rs:2713, seeded for value-restoring undo at :1357):

Field	Operation
`canvas.layout_defaults`	`SetCanvasLayoutDefaults`
`tuning_context`	`SetTuningContext`
`spelling_precedence`	`SetSpellingPrecedence`

Entities — set-union mint with byte-identical re-carry idempotence, the CreateStaff pattern (reduce.rs:3850, graph-aware preconditions at :3824):

Field	Family
`instruments`	`CreateInstrument` …
`staff_groups`	`CreateStaffGroup` …
`parts`	`CreatePartDefinition` …
`analysis_layers`	`CreateAnalysisLayer` …
`views`	`CreateView` …
`StaffInstance.measures`	`CreateMeasure` …

Delete and modify coverage per family is the tranche contract's design work, guided by the existing precedent (Group 3's "mint + empty-only delete" for containers; CreateStaff lands today with no DeleteStaff, so full CRUD is not automatically owed). What is owed is that every family's referential preconditions are graph-aware, in the shape CreateStaff already uses:

CreateStaffGroup.members, CreatePartDefinition.staves → live Staffs;
CreateView.active_layers → live AnalysisLayers;
CreateMeasure → a live StaffInstance;
deleting an entity with live dependents → refuse (container-not-empty).

Measures: authored, not derived

Ruled 2026-07-24. TimeAnchor::Measure { id, .. } means cross-cutting structures anchor to measure ids; deriving measures from the metric grid would make their identity a function of the meter, so every time-signature change would re-derive a different measure set and orphan the anchors pointing into it. Authored ids survive a meter change.

Accepted cost: measure/meter consistency becomes an authoring obligation backed by a graph invariant, not a model guarantee. The invariant belongs in the tranche.

Out of scope, with reasons

identity — not an authored field; ruled in §3. It stays on Score and on the wire, and reduction derives its counter. Nothing to author.
decomposition_attachments — derived, not authored. The prepass creates it (core/src/prepass.rs:382); reduction only ever retains (reduce.rs:2342). It leaves the table rather than gaining operations. Flagged for ratification with the tranche.

3. The `identity` sub-decision — RULED 2026-07-24

IdentityContext { replica_id, next_counter } is replica-scoped by construction (ids.rs:711-717) yet lives on Score, which the codec encodes (codec.rs:2766, :3223). Today the value is inherited from a shared base, which masks the tension. Under this ruling reduction runs onto Score::empty(identity), so whoever opens the document chooses it — and two replicas reducing an identical log then produce Scores differing in an encoded field while the music is identical.

The framing above understates it

Verified against the working tree while scoping the tranche:

epiphany-ops contains no .identity reference at all. Reduction never reads or writes it. next_counter advances only through IdentityContext::take_counter (ids.rs:766), reached from mint / mint_operation, which reduction never calls.
Invariant 11 does not bound the counter. invariants.rs:1746-1752 rejects only the reserved SYSTEM_DERIVED replica; nothing checks next_counter against the ids actually present in the score.
No production code mints from score.identity yet — every such site is under #[cfg(test)] (editor-core/src/lib.rs:4124). The hazard is latent, and this tranche is what activates it.

So Score::identity is an authoring cursor that reduction never advances. Divergent bytes are the lesser problem. The real one: this tranche is precisely when production code begins minting genesis-entity ids. Under from-empty the cursor holds whatever seeded Score::empty(identity) — 0 for a fresh context — while the log already carries that replica's ids at counters 0..N. Minting from it re-issues used counters, silently: no invariant, no reduction step, and no wire check catches it. Every option originally listed relocates or accepts the field; none makes the cursor correct.

The ruling

Accept replica-dependent Score bytes, and derive the cursor under from-empty reduction.

identity stays on Score and stays canonically encoded. No wire change, and in particular no schema major 4 on the Score/Snapshot role that tranche 3b-i froze at 3.
Byte-equality claims are confined to MaterializedState, which carries no identity field and whose canonical_bytes is already the asserted convergence surface (reduce.rs:10031). §5's acceptance criterion is already written against MaterializedState, so this costs no restatement.
From-empty reduction sets next_counter to 1 + max(counter) over ids authored by the reducing replica in the log, or leaves the seed untouched when that replica authored none. A function of the log and the chosen replica_id, hence convergent for a given replica and correct by construction.

Point 3 makes reduction write identity for the first time. Name that in the tranche: it is a deliberate new behaviour, not an oversight, and it wants a test that mints from a reduced score and asserts no collision with the log.

Why not the alternatives

Manifest (previously recommended here). Rejected. req:format:manifest-id (core_spec.tex:11177) promises normatively that "two conforming writers committing the same manifest body at the same generation of the same document derive identical ManifestIds". A replica-scoped field in a shipped, content-addressed manifest either breaks that promise or must be excluded from the preimage — at which point it is one replica's counter riding to another in a field no reader may trust. It also grows the one structure bundle.rs:63 records as never growing a versioned layout.
Exclude from the Score encoding. A layout change under req:binfmt:frozen-layout — schema major 4, a second wire raise on a different role from §4's "one accept-set raise, spent once". And it leaves the stale cursor standing.
Remove from Score entirely (session state the editor owns). The cleanest end state, and worth revisiting later; priced here at major 4 plus an API break across Score::empty and every construction site, which this tranche does not need to buy in order to be correct.

4. Standing constraints

Pruning MUST NOT be implemented until disposition C lands. This ruling makes documents openable, editable, and collaborative; it does not make them prunable. A prune deletes the covered envelopes and installs a MaterializedState base carrying no graph values, so the score is unreconstructable afterward — and MaterializedState.effects are outcomes, not payloads, so nothing rebuilds it. Pruning is unimplemented today (no fn prune; opset.rs:7 calls it out-of-scope-for-v0), which is why this costs nothing now and would cost everything later. C — the canonical base carrying graph values, the same checkpoint T4b needs for incremental materialization — remains required before any pruning implementation.

The from-empty path must reduce with a graph, not base-free. Reduction has two modes, and graph-aware preconditions are skipped in the base-free one because it has no universe to check against (reduce.rs:3822, :3721). Score::empty(identity) is a graph, so new_onto with an empty score enforces every precondition from the first operation; the base-free mode does not. A from-empty document reduced through the wrong entry point silently loses referential enforcement. Name this in the tranche and test it.

One accept-set raise, spent once. OperationEnvelopeBlock is capped at major 2 (bundle.rs:69) because no operation payload embeds these types. The first new kind that does raises it to 3; every later kind in that major is free. The new kinds therefore land as one batch, not dribbled out per need. Note this is a different major from Push-4b's schema major 3, which is the Score/Snapshot-role wire that tranche 3b-i opened and permanently froze — there is no free ride between them.

Additive discriminants. New kinds extend past TransposeInterval under the existing convention (req:binfmt:kind-discriminants); canonical bytes for existing types do not move.

5. Acceptance

A document created empty and given only operations materializes a note-bearing Score — the full chain, no fixture, no base.
Two replicas applying concurrent genesis-era operations in any delivery order converge to byte-identical MaterializedState.
Opening such a document from a bundle reaches a note, which is what unblocks T1b.
Existing canonical bytes, goldens, and conformance gates unmoved except where the accept-set raise is the deliberate change.

6. What this unblocks

spec/PLAN_EDITOR_APP.md §Ruling B blocker (i) is resolved. Blocker (ii) — the version-aware envelope decoder — is unaffected and still open; its residual is one bounded ops packet. T1b's remaining runway is therefore blocker (ii) plus the Ruling-D ownership API, and the lease/save/single-writer machinery can be contracted in parallel with this tranche, since it does not depend on genesis being authorable.

Related: spec/ANALYSIS_GENESIS_PERSISTENCE.md, spec/PLAN_EDITOR_APP.md §Ruling B / §3.7, spec/PLAN_PUSH4B_TUNING.md (the tranche mold).

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