| 2026-06-03 | pending | Fast-path unchanged verification after an empty HealthKit delta page. | The successful full-profile reimport spent `15.1s` in finalize despite `0.1s` insert time; Heart Rate alone spent `9.0s` finalizing. The empty-delta path now calls an explicit unchanged-verification store method that copies the previous type summary and daily aggregates without first scanning sample events to prove zero changes. Expected signal: repeated no-delta/full-profile `SummedFinalizeElapsed` and Heart Rate finalize time drop sharply. |

 | 2026-06-03 | pending | Persist HealthKit capture anchors in SQLite. | A later no-delta attempt still reimported full high-volume types (`Records: 2,646,590`, `WallClock: 45.8s`, Heart Rate `922,521`, Active Energy `346,473`) because incremental anchors were still read from legacy SwiftData `TypeCount`, while the refactored app now chains observations from SQLite. SQLite now stores per-type capture state (`anchor_data`, count, content hash, yearly counts, range) and the import path uses it when legacy `TypeCount` state is missing. Expected signal: the first run after this change may seed anchors; the following no-delta run should report empty HealthKit delta pages instead of full `record_import` counts for large stable types. |

 | 2026-06-03 | pending | Clarify capture mode in record-import diagnostics. | Two full-profile repeated snapshots after SQLite capture-state persistence completed successfully with stable checksum and identical record count (`2,646,613`). The first ran in `6.3s` with `SummedProcessingElapsed: 0.0s`, `SummedInsertElapsed: 0.0s`, `SummedFinalizeElapsed: 2.6s`; the second ran in `6.4s` with `0.0s` processing/insert and `2.7s` finalize. Heart Rate `922,526` and Active Energy `346,478` each completed around `0.2s`, proving the heavy full reimport path was avoided. The report wording still said "`N` samples in 1 anchored segment", which is ambiguous for inherited unchanged summaries; diagnostics now label unchanged empty-delta, delta-apply, and full-import modes explicitly. |

 ## Current Diagnosis

 3. Continue repeated full-profile captures, but do not require perfect no-delta.

    Compare `snapshotChecksum`, `Records`, `WallClockDuration`,

    `SummedProcessingElapsed`, `SummedInsertElapsed`, `SummedFinalizeElapsed`,

 4. Add or inspect timing around per-record processing for changed high-volume metrics, especially Heart Rate, to separate sample DTO/fingerprint work from SQLite idempotency checks.

 5. Run a non-chain-start/full-scan benchmark after skipping unchanged `verified` events and fast-pathing already-open visibility ranges. Compare `SummedInsertElapsed`, `Heart Rate insertElapsed`, `Steps insertElapsed`, and `Walking + Running Distance insertElapsed`.

 6. Reduce any remaining per-sample SQLite writes for unchanged existing samples during non-chain-start full scans.

             records: [],

             recordArchiveData: recordArchiveData

         )

         result.timingBreakdown = timingBreakdown

         await persistTypeCaptureState(from: result, observationID: archiveObservationID)

         return result

         case initialImport

         case delta

         case unchangedDelta

     }

     struct Bin: Sendable {

     let distributionBins: [DistributionBinData]

     let records: [RecordData]

     let recordArchiveData: Data?

     var timeoutConfiguredSeconds: TimeInterval = 0

     var totalElapsedSeconds: TimeInterval = 0

     var timeoutMode: String = "default"

             suggestedRetryTimeout: result.suggestedRetryTimeout,

             timeoutCount: result.timeoutCount,

             successCount: result.successCount,

         )

     }

         var timeoutCount: Int = 0

         var successCount: Int = 0

         var timingBreakdown: ImportTimingBreakdown = .zero

         var blockProgress: String = ""

         var blockElapsedSeconds: TimeInterval = 0

         var blockSamplesPerSecond: Double = 0

         suggestedRetryTimeout: TimeInterval,

         timeoutCount: Int,

         successCount: Int,

     ) {

         let index = visibleTypeIndex(for: id)

         types[index].quality = quality

         types[index].timeoutCount = timeoutCount

         types[index].successCount = successCount

         types[index].timingBreakdown = timingBreakdown

     }

     func updateTimeoutProfile(

         let summedMetricResidualElapsed = progress.types.reduce(0) { partial, type in

             partial + timingResidual(totalElapsed: type.totalElapsedSeconds, breakdown: type.timingBreakdown)

         }

         lines.append("SummedMetricTotalElapsed: \(formatDuration(summedMetricTotalElapsed))")

         lines.append("SummedFetchElapsed: \(formatDuration(aggregateTiming.fetchElapsedSeconds))")

         lines.append("SummedProcessingElapsed: \(formatDuration(aggregateTiming.processingElapsedSeconds))")

         lines.append("SummedInsertElapsed: \(formatDuration(aggregateTiming.insertElapsedSeconds))")

         lines.append("SummedFinalizeElapsed: \(formatDuration(aggregateTiming.finalizeElapsedSeconds))")

         lines.append("SummedResidualElapsed: \(formatDuration(summedMetricResidualElapsed))")

         lines.append("")

         lines.append(failedLines)

             lines.append("  identifier: \(type.id)")

             lines.append("  quality: \(type.quality)")

             lines.append("  count: \(type.recordCount)")

             lines.append("  timeoutMode: \(type.timeoutMode)")

             lines.append("  timeoutConfigured: \(formatDuration(type.timeoutConfiguredSeconds))")

             lines.append("  lastSuccessfulElapsed: \(type.lastSuccessfulElapsed > 0 ? formatDuration(type.lastSuccessfulElapsed) : "none")")