-**Last Updated:** 2026-05-25

-| UI | Prototype exists; Snapshots/Data Types now default to the local device timeline instead of a multi-device picker. Dashboard status reads archive/cache observation rows and shows cache health, with SwiftData retained only for capture/review actions; Snapshots timeline reads archive/cache rows when available and no longer queries `SnapshotDelta` for list summaries; snapshot detail summaries/type rows require Core Data cache rows and no longer fall back to `SnapshotDelta`/`TypeDelta`; Data Types list rows no longer fall back to SwiftData `TypeCount` traversal; data type detail reads Core Data type/diff summaries and uses SQLite `diffRecords` for paged drill-down; record-change evolution and temporal distribution screens now receive DTO rows/cache input instead of querying SwiftData directly; export preview reads the archive export API before showing/exporting JSON; simplified detail mode replaces heavy charts with summary rows on small/accessibility layouts or when enabled in Settings; visible change labels now use neutral new/missing/change-review language, with SwiftData detail cache as transition fallback | Remove remaining SwiftData navigation handles |

-- Current UI/cache layers still depend on 22 SwiftData-backed files for launch container, capture review actions, navigation handles, some charts, and PDF paths.

-**Last Updated:** 2026-05-25

-- [x] Data type detail uses SQLite `diffSummary` when archive observation ids exist.

-**Last Updated:** 2026-05-25

-After moving temporal distribution to cache DTO inputs, 19 app files still

-have SwiftData imports.

-    @Environment(\.modelContext) private var modelContext

-    @Query private var allDeltas: [SnapshotDelta]

-    private var currentDelta: SnapshotDelta? {

-        guard let previousSnapshot else { return nil }

-        return allDeltas.first {

-            $0.toSnapshotID == currentSnapshot.id &&

-            $0.fromSnapshotID == previousSnapshot.id

-        }

-    }

-

-    private var currentTypeDelta: TypeDelta? {

-        currentDelta?.typeDeltas?.first { $0.typeIdentifier == typeIdentifier }

-    }

-

-        let net = (currentTypeDelta?.countDelta ?? (quickCurrentCountValue - quickPreviousCountValue))

-            let fallback = recordEvolutionFallback(for: snapshot)

-    // MARK: - Optimized Content

-

-    @ViewBuilder

-    private var metricComparison: some View {

-        if previousSnapshot == nil {

-            EmptyView()

-        } else {

-            MetricComparisonCard(

-                currentValue: currentTypeCount?.count ?? 0,

-                previousValue: previousTypeCount?.count,

-                displayName: displayName,

-                isCurrentValid: (currentTypeCount?.count ?? 0) >= 0,

-                isPreviousTracked: previousTypeCount != nil

-            )

-        }

-    }

-

-    @ViewBuilder

-    private var typeEvolutionSection: some View {

-        if previousSnapshot != nil {

-            TypeEvolutionTimeline(

-                snapshots: timelineSnapshots,

-                typeIdentifier: typeIdentifier,

-                displayName: displayName,

-                currentSnapshotID: currentSnapshot.id

-            )

-        }

-    }

-

-    private func typeDeltaSummaryText(_ typeDelta: TypeDelta) -> String {

-        switch typeDelta.transition {

-        case .unchanged:

-            return "No metric-level change recorded."

-        case .changed:

-            if typeDelta.countDelta == 0 {

-                return "Content changed while count stayed the same."

-            }

-            let prefix = typeDelta.countDelta > 0 ? "+" : ""

-            return "Count delta: \(prefix)\(typeDelta.countDelta)."

-        case .appeared:

-            return "Metric is new in this observation."

-        case .disappeared:

-            return "Metric is missing from this observation."

-        }

-    }

-

-    private func recordEvolutionFallback(for snapshot: HealthSnapshot) -> (added: Int, disappeared: Int, exact: Bool) {

-        guard let delta = allDeltas.first(where: {

-            $0.fromSnapshotID == previous.id &&

-            $0.toSnapshotID == snapshot.id

-        }),

-        let typeDelta = delta.typeDeltas?.first(where: { $0.typeIdentifier == typeIdentifier }) else {

-            return (0, 0, false)

-        }

-

-        switch typeDelta.transition {

-        case .unchanged:

-            return (0, 0, false)

-        case .changed:

-            if typeDelta.countDelta > 0 {

-                return (typeDelta.countDelta, 0, false)

-            }

-            if typeDelta.countDelta < 0 {

-                return (0, abs(typeDelta.countDelta), false)

-            }

-            return (0, 0, false)

-        case .appeared:

-            return (max(typeDelta.countDelta, 1), 0, false)

-        case .disappeared:

-            return (0, max(abs(typeDelta.countDelta), 1), false)

-        }

-        let resolution = currentDetailCacheResolution()

-        detailCacheDiagnostic = resolution?.diagnostic ?? detailCacheDiagnostic

-        guard let cache = resolution?.cache else {

-            diffState = .unavailable

-        diffState = .loaded(DataTypeRecordDiff(cache: cache))

-    @MainActor

-    private func currentDetailCacheResolution() -> TypeCountDetailCacheResolution? {

-        if isCurrentTypeContentAliasToPrevious {

-            return TypeCountDetailCacheResolution(

-                cache: nil,

-                diagnostic: "alias-to-previous"

-            )

-        }

-

-        if let cache = currentTypeCount?.detailCache,

-           cache.matchesBaseline(previousSnapshot?.id) {

-            return TypeCountDetailCacheResolution(

-                cache: cache,

-                diagnostic: "resolver-v4 phase=cache-hit-view"

-            )

-        }

-

-        guard let currentTypeCount,

-              let previousSnapshot else {

-            return nil

-        }

-

-        return currentTypeCount.resolveDetailCacheWithDiagnostics(

-            previous: previousTypeCount,

-            baselineSnapshotID: previousSnapshot.id,

-            context: modelContext,

-            source: "dataTypeDetail"

-        )

-    }