The SINGLE authored input to an engagement (Plan 15 drift ④: consolidates the former mission.json + criteria.json — ehimare led this and is canonical). Holds the business framing (purpose/useCases/stakeholders/stressTest/values/narrative) AND the scored criteria[] the kernel reads via ctx.data.requirements.criteria. Instance extensions narrow via allOf + $ref to this $id with unevaluatedProperties:false.

The architectures (positions) — the spine of distinct structural stances a solution can fill (e.g. complete solution → in-house build). The board groups solutions by architecture via solution.architecture → architectures[].key. A bare array of architecture records. Instance extensions narrow via allOf + $ref to this $id with unevaluatedProperties:false.

The decisions / values layer — the side-ledger of open forks that accrues across ALL phases (Plan 15 MR-4: decisions are not a phase). A fork narrows the live solution space; its options prune a typed reference set (Plan 15 MR-1: architectures | solutions | fillers, instance-declared). Instance extensions narrow via allOf + $ref to this $id with unevaluatedProperties:false.

Phase-4 candidate compositions — the filled, scored architectures. A solutions file is EITHER a bare array of solution objects (e.g. skischule's solutions-platform.json) OR an object wrapping them under `system` (demo/template/ehimare). Both shapes are blessed; pick whichever the instance ships. The per-solution shape is $defs/solution. Instance extensions narrow via allOf + $ref to this $id and add their own keys with unevaluatedProperties:false.

The building blocks that fill gaps a core solution leaves — the dockable components a solution's coverage references via `part:<id>`/`aug:<id>`. Backs the 'Building blocks by job' view. Instance extensions narrow via allOf + $ref to this $id with unevaluatedProperties:false.

The raw, un-scored tool survey — every candidate seen, with its gate verdicts. Backs the Tools view; scoring happens later in solutions/matrix. Typically GENERATED from a richer research profile (not hand-maintained). Instance extensions narrow via allOf + $ref to this $id with unevaluatedProperties:false.

The append-only research ledger backing the Deep-dive → Report view — what was surveyed, round by round, plus the per-position/per-assist research state. Append-only `rounds[]` is what makes the iterative loop (Plan 15 MR-4) representable: new evidence is added, never overwritten. Instance extensions narrow via allOf + $ref to this $id with unevaluatedProperties:false.

Cockpit configuration — the weighting model and category spine the kernel scores under. Drift fixed per Plan 15 drift ①: the canonical keys are `weights`/`presets` (every instance ships these; the prose contract's former `weightTriple`/`weightingPresets` are retired). Instance extensions narrow via allOf + $ref to this $id and add their own keys with unevaluatedProperties:false.

Per-instance extension for the skischule engagement's solutions file (solutions-platform.json) — a Plan 15 TARGET-SPEC. skischule's signature divergence is its typed COST ENGINE (seasonal seats · annual discount · peak weeks · the Chatwoot configurator), which the generic base deliberately does not model. This composes the base solution ($ref) and adds the cost-engine fields; unevaluatedProperties:false rejects anything neither the base nor this extension documents. The cost-component shape is skischule-internal and refined when skischule actually re-pins and migrates — not validated until then (§ Completion criterion).