diff --git a/lib/application/application.dart b/lib/application/application.dart
index 1ceb379..32e79f7 100644
--- a/lib/application/application.dart
+++ b/lib/application/application.dart
@@ -3,3 +3,6 @@
 /// This layer owns use cases and ports. It may depend on domain, but concrete
 /// adapters are wired only from the composition root.
 library;
+
+export 'ports.dart';
+export 'use_cases.dart';
diff --git a/lib/application/ports.dart b/lib/application/ports.dart
new file mode 100644
index 0000000..f83ebab
--- /dev/null
+++ b/lib/application/ports.dart
@@ -0,0 +1,49 @@
+import '../domain/domain.dart';
+
+abstract interface class Clock {
+  DateTime now();
+}
+
+final class SystemClock implements Clock {
+  const SystemClock();
+
+  @override
+  DateTime now() => DateTime.now().toUtc();
+}
+
+abstract interface class IdGenerator {
+  String newId();
+}
+
+abstract interface class ExerciseRepository {
+  Future<Exercise?> findById(String id);
+  Future<List<Exercise>> listActive();
+  Future<void> save(Exercise exercise);
+}
+
+abstract interface class ProgramRepository {
+  Future<Program?> findById(String id);
+  Future<void> save(Program program);
+  Future<void> saveExercise(ProgramExercise exercise);
+}
+
+abstract interface class WorkoutTemplateRepository {
+  Future<WorkoutTemplate?> findById(String id);
+  Future<void> save(WorkoutTemplate template);
+  Future<void> saveProgram(WorkoutTemplateProgram program);
+  Future<void> saveOverride(WorkoutTemplateExerciseOverride override);
+}
+
+abstract interface class ActiveSessionRepository {
+  Future<ActiveWorkoutSession?> findById(String id);
+  Future<void> save(ActiveWorkoutSession session);
+  Future<void> saveSetResult(ActiveSetResult result);
+  Future<void> saveRestState(ActiveRestState restState);
+  Future<List<ActiveSetResult>> listSetResults(String sessionId);
+  Future<List<ActiveRestState>> listRestStates(String sessionId);
+}
+
+abstract interface class WorkoutHistoryRepository {
+  Future<void> save(WorkoutHistory history);
+  Future<void> saveSetResult(WorkoutHistorySetResult result);
+}
diff --git a/lib/application/use_cases.dart b/lib/application/use_cases.dart
new file mode 100644
index 0000000..d43c94c
--- /dev/null
+++ b/lib/application/use_cases.dart
@@ -0,0 +1,390 @@
+import 'dart:convert';
+
+import '../domain/domain.dart';
+import 'ports.dart';
+
+final class ExerciseUseCases {
+  const ExerciseUseCases({
+    required this.repository,
+    required this.clock,
+    required this.ids,
+    required this.originDeviceId,
+  });
+
+  final ExerciseRepository repository;
+  final Clock clock;
+  final IdGenerator ids;
+  final String originDeviceId;
+
+  Future<Exercise> create({
+    required String name,
+    String? description,
+    String? imageMediaId,
+    String? videoMediaId,
+    required bool hasTimeMeasure,
+    required bool hasRepsMeasure,
+    required bool hasScoreMeasure,
+    String? scoreLabel,
+    String? scoreUnit,
+  }) async {
+    final now = clock.now();
+    final exercise = Exercise(
+      metadata: _newMetadata(ids, originDeviceId, now),
+      name: name,
+      description: description,
+      imageMediaId: imageMediaId,
+      videoMediaId: videoMediaId,
+      hasTimeMeasure: hasTimeMeasure,
+      hasRepsMeasure: hasRepsMeasure,
+      hasScoreMeasure: hasScoreMeasure,
+      scoreLabel: scoreLabel,
+      scoreUnit: scoreUnit,
+    );
+    await repository.save(exercise);
+    return exercise;
+  }
+
+  Future<void> save(Exercise exercise) => repository.save(exercise);
+
+  Future<Exercise> archive(String id) async {
+    final exercise = await repository.findById(id);
+    if (exercise == null) {
+      throw const DomainException('Exercise not found.');
+    }
+    final archived = exercise.archive(clock.now());
+    await repository.save(archived);
+    return archived;
+  }
+}
+
+final class ProgramUseCases {
+  const ProgramUseCases({
+    required this.programRepository,
+    required this.exerciseRepository,
+    required this.clock,
+    required this.ids,
+    required this.originDeviceId,
+  });
+
+  final ProgramRepository programRepository;
+  final ExerciseRepository exerciseRepository;
+  final Clock clock;
+  final IdGenerator ids;
+  final String originDeviceId;
+
+  Future<Program> create({
+    required String name,
+    required int defaultRestSeconds,
+  }) async {
+    final now = clock.now();
+    final program = Program(
+      metadata: _newMetadata(ids, originDeviceId, now),
+      name: name,
+      defaultRestSeconds: defaultRestSeconds,
+    );
+    await programRepository.save(program);
+    return program;
+  }
+
+  Future<ProgramExercise> addExercise({
+    required String programId,
+    required String exerciseId,
+    required int position,
+    required int setsCount,
+    required Set<WorkoutMeasure> enabledMeasures,
+    int? targetTimeSeconds,
+    int? targetReps,
+    double? targetScore,
+    int? restSecondsOverride,
+  }) async {
+    final source = await exerciseRepository.findById(exerciseId);
+    if (source == null) {
+      throw const DomainException('Exercise not found.');
+    }
+    final now = clock.now();
+    final programExercise = ProgramExercise.snapshotFromExercise(
+      metadata: _newMetadata(ids, originDeviceId, now),
+      programId: programId,
+      exercise: source,
+      position: position,
+      setsCount: setsCount,
+      enabledMeasures: enabledMeasures,
+      targetTimeSeconds: targetTimeSeconds,
+      targetReps: targetReps,
+      targetScore: targetScore,
+      restSecondsOverride: restSecondsOverride,
+    );
+    await programRepository.saveExercise(programExercise);
+    return programExercise;
+  }
+}
+
+final class WorkoutTemplateUseCases {
+  const WorkoutTemplateUseCases({
+    required this.templateRepository,
+    required this.programRepository,
+    required this.clock,
+    required this.ids,
+    required this.originDeviceId,
+  });
+
+  final WorkoutTemplateRepository templateRepository;
+  final ProgramRepository programRepository;
+  final Clock clock;
+  final IdGenerator ids;
+  final String originDeviceId;
+
+  Future<WorkoutTemplate> create({required String name}) async {
+    final now = clock.now();
+    final template = WorkoutTemplate(
+      metadata: _newMetadata(ids, originDeviceId, now),
+      name: name,
+    );
+    await templateRepository.save(template);
+    return template;
+  }
+
+  Future<WorkoutTemplateProgram> addProgramSnapshot({
+    required String workoutTemplateId,
+    required String programId,
+    required int position,
+  }) async {
+    final program = await programRepository.findById(programId);
+    if (program == null) {
+      throw const DomainException('Program not found.');
+    }
+    final now = clock.now();
+    final snapshot = WorkoutTemplateProgram.snapshotFromProgram(
+      metadata: _newMetadata(ids, originDeviceId, now),
+      workoutTemplateId: workoutTemplateId,
+      program: program,
+      position: position,
+    );
+    await templateRepository.saveProgram(snapshot);
+    return snapshot;
+  }
+
+  Future<WorkoutTemplateExerciseOverride> overrideExerciseTargets({
+    required String workoutTemplateProgramId,
+    required String snapshotProgramExerciseId,
+    int? setsCountOverride,
+    int? targetTimeSecondsOverride,
+    int? targetRepsOverride,
+    double? targetScoreOverride,
+    Set<WorkoutMeasure>? attemptedMeasureOverride,
+  }) async {
+    if (attemptedMeasureOverride != null) {
+      throw const DomainException(
+        'Workout templates cannot override active measures.',
+      );
+    }
+    final now = clock.now();
+    final override = WorkoutTemplateExerciseOverride(
+      metadata: _newMetadata(ids, originDeviceId, now),
+      workoutTemplateProgramId: workoutTemplateProgramId,
+      snapshotProgramExerciseId: snapshotProgramExerciseId,
+      setsCountOverride: setsCountOverride,
+      targetTimeSecondsOverride: targetTimeSecondsOverride,
+      targetRepsOverride: targetRepsOverride,
+      targetScoreOverride: targetScoreOverride,
+    );
+    await templateRepository.saveOverride(override);
+    return override;
+  }
+}
+
+final class ActiveWorkoutSessionUseCases {
+  const ActiveWorkoutSessionUseCases({
+    required this.sessionRepository,
+    required this.templateRepository,
+    required this.clock,
+    required this.ids,
+    required this.originDeviceId,
+  });
+
+  final ActiveSessionRepository sessionRepository;
+  final WorkoutTemplateRepository templateRepository;
+  final Clock clock;
+  final IdGenerator ids;
+  final String originDeviceId;
+
+  Future<ActiveWorkoutSession> startFromTemplate(String templateId) async {
+    final template = await templateRepository.findById(templateId);
+    if (template == null) {
+      throw const DomainException('Workout template not found.');
+    }
+    final now = clock.now();
+    final session = ActiveWorkoutSession(
+      metadata: _newMetadata(ids, originDeviceId, now),
+      sourceWorkoutTemplateId: templateId,
+      status: ActiveWorkoutStatus.running,
+      startedAt: now,
+      lastPersistedAt: now,
+      elapsedActiveMs: 0,
+      currentProgramIndex: 0,
+      currentExerciseIndex: 0,
+      currentSetIndex: 0,
+      resolvedTemplateSnapshotJson: jsonEncode({
+        'templateId': template.metadata.id,
+        'name': template.name,
+        'programs': template.programs
+            .map(
+              (program) => {
+                'id': program.metadata.id,
+                'programNameSnapshot': program.programNameSnapshot,
+                'programSnapshotJson': program.programSnapshotJson,
+              },
+            )
+            .toList(),
+        'overrides': template.overrides
+            .map(
+              (override) => {
+                'workoutTemplateProgramId': override.workoutTemplateProgramId,
+                'snapshotProgramExerciseId': override.snapshotProgramExerciseId,
+                'setsCountOverride': override.setsCountOverride,
+                'targetTimeSecondsOverride': override.targetTimeSecondsOverride,
+                'targetRepsOverride': override.targetRepsOverride,
+                'targetScoreOverride': override.targetScoreOverride,
+              },
+            )
+            .toList(),
+      }),
+    );
+    await sessionRepository.save(session);
+    return session;
+  }
+
+  Future<ActiveWorkoutSession> pause(String sessionId) async {
+    final session = await _requiredSession(sessionId);
+    final paused = session.pause(clock.now());
+    await sessionRepository.save(paused);
+    return paused;
+  }
+
+  Future<ActiveWorkoutSession> resume(String sessionId) async {
+    final session = await _requiredSession(sessionId);
+    final resumed = session.resume(clock.now());
+    await sessionRepository.save(resumed);
+    return resumed;
+  }
+
+  int elapsedActiveMilliseconds(ActiveWorkoutSession session) {
+    return session.elapsedActiveMillisecondsAt(clock.now());
+  }
+
+  Future<ActiveSetResult> recordSetResult(ActiveSetResult result) async {
+    await sessionRepository.saveSetResult(result);
+    return result;
+  }
+
+  Future<ActiveRestState> startRestAfterSet({
+    required String sessionId,
+    required int afterProgramIndex,
+    required int afterExerciseIndex,
+    required int afterSetIndex,
+    required int plannedRestSeconds,
+    int? adjustedRestSeconds,
+  }) async {
+    final now = clock.now();
+    final rest = ActiveRestState(
+      metadata: _newMetadata(ids, originDeviceId, now),
+      activeWorkoutSessionId: sessionId,
+      afterProgramIndex: afterProgramIndex,
+      afterExerciseIndex: afterExerciseIndex,
+      afterSetIndex: afterSetIndex,
+      plannedRestSeconds: plannedRestSeconds,
+      adjustedRestSeconds: adjustedRestSeconds ?? plannedRestSeconds,
+      startedAt: now,
+    );
+    await sessionRepository.saveRestState(rest);
+    return rest;
+  }
+
+  Future<ActiveWorkoutSession> _requiredSession(String sessionId) async {
+    final session = await sessionRepository.findById(sessionId);
+    if (session == null) {
+      throw const DomainException('Active workout session not found.');
+    }
+    return session;
+  }
+}
+
+final class CloseWorkoutSessionUseCase {
+  const CloseWorkoutSessionUseCase({
+    required this.sessionRepository,
+    required this.historyRepository,
+    required this.clock,
+    required this.ids,
+    required this.originDeviceId,
+  });
+
+  final ActiveSessionRepository sessionRepository;
+  final WorkoutHistoryRepository historyRepository;
+  final Clock clock;
+  final IdGenerator ids;
+  final String originDeviceId;
+
+  Future<WorkoutHistory> close({
+    required String sessionId,
+    required String nameSnapshot,
+    required bool completed,
+  }) async {
+    final session = await sessionRepository.findById(sessionId);
+    if (session == null) {
+      throw const DomainException('Active workout session not found.');
+    }
+    final now = clock.now();
+    final results = await sessionRepository.listSetResults(sessionId);
+    final historyId = ids.newId();
+    final history = WorkoutHistory(
+      metadata: EntityMetadata(
+        id: historyId,
+        createdAt: now,
+        updatedAt: now,
+        originDeviceId: originDeviceId,
+      ),
+      sourceWorkoutTemplateId: session.sourceWorkoutTemplateId,
+      sourceActiveWorkoutSessionId: session.metadata.id,
+      nameSnapshot: nameSnapshot,
+      startedAt: session.startedAt,
+      endedAt: now,
+      totalActiveMs: session.elapsedActiveMillisecondsAt(now),
+      completed: completed,
+      historySnapshotJson: jsonEncode({
+        'sessionId': session.metadata.id,
+        'resolvedTemplateSnapshotJson': session.resolvedTemplateSnapshotJson,
+        'results': results
+            .map(
+              (result) => {
+                'programSnapshotId': result.programSnapshotId,
+                'exerciseSnapshotId': result.exerciseSnapshotId,
+                'programIndex': result.programIndex,
+                'exerciseIndex': result.exerciseIndex,
+                'setIndex': result.setIndex,
+                'actualTimeMs': result.actualTimeMs,
+                'actualReps': result.actualReps,
+                'actualScore': result.actualScore,
+                'scoreLabelSnapshot': result.scoreLabelSnapshot,
+                'scoreUnitSnapshot': result.scoreUnitSnapshot,
+              },
+            )
+            .toList(),
+      }),
+    );
+    await historyRepository.save(history);
+    return history;
+  }
+}
+
+EntityMetadata _newMetadata(
+  IdGenerator ids,
+  String originDeviceId,
+  DateTime now,
+) {
+  return EntityMetadata(
+    id: ids.newId(),
+    createdAt: now,
+    updatedAt: now,
+    originDeviceId: originDeviceId,
+  );
+}
diff --git a/lib/domain/domain.dart b/lib/domain/domain.dart
index dbb123d..173f4bd 100644
--- a/lib/domain/domain.dart
+++ b/lib/domain/domain.dart
@@ -2,3 +2,5 @@
 ///
 /// Keep this layer free from Flutter, Drift, platform APIs, and IO.
 library;
+
+export 'entities.dart';
diff --git a/lib/domain/entities.dart b/lib/domain/entities.dart
new file mode 100644
index 0000000..5281155
--- /dev/null
+++ b/lib/domain/entities.dart
@@ -0,0 +1,742 @@
+import 'dart:convert';
+
+enum SyncState { localOnly, dirty, synced, deleted }
+
+enum MediaKind { image, video }
+
+enum WorkoutMeasure { time, reps, score }
+
+enum ActiveWorkoutStatus { running, paused, savedExit, completed, abandoned }
+
+final class DomainException implements Exception {
+  const DomainException(this.message);
+
+  final String message;
+
+  @override
+  String toString() => message;
+}
+
+final class EntityMetadata {
+  const EntityMetadata({
+    required this.id,
+    required this.createdAt,
+    required this.updatedAt,
+    required this.originDeviceId,
+    this.deletedAt,
+    this.schemaVersion = 1,
+    this.syncState = SyncState.dirty,
+    this.localRevision = 0,
+    this.futureOwnerProfileId,
+    this.lastSyncedAt,
+    this.remoteRevision,
+  });
+
+  final String id;
+  final DateTime createdAt;
+  final DateTime updatedAt;
+  final DateTime? deletedAt;
+  final int schemaVersion;
+  final SyncState syncState;
+  final int localRevision;
+  final String originDeviceId;
+  final String? futureOwnerProfileId;
+  final DateTime? lastSyncedAt;
+  final String? remoteRevision;
+
+  EntityMetadata touch(DateTime now) {
+    return copyWith(updatedAt: now, localRevision: localRevision + 1);
+  }
+
+  EntityMetadata markDeleted(DateTime now) {
+    return copyWith(
+      updatedAt: now,
+      deletedAt: now,
+      syncState: SyncState.deleted,
+      localRevision: localRevision + 1,
+    );
+  }
+
+  EntityMetadata copyWith({
+    DateTime? createdAt,
+    DateTime? updatedAt,
+    DateTime? deletedAt,
+    int? schemaVersion,
+    SyncState? syncState,
+    int? localRevision,
+    String? originDeviceId,
+    String? futureOwnerProfileId,
+    DateTime? lastSyncedAt,
+    String? remoteRevision,
+  }) {
+    return EntityMetadata(
+      id: id,
+      createdAt: createdAt ?? this.createdAt,
+      updatedAt: updatedAt ?? this.updatedAt,
+      deletedAt: deletedAt ?? this.deletedAt,
+      schemaVersion: schemaVersion ?? this.schemaVersion,
+      syncState: syncState ?? this.syncState,
+      localRevision: localRevision ?? this.localRevision,
+      originDeviceId: originDeviceId ?? this.originDeviceId,
+      futureOwnerProfileId: futureOwnerProfileId ?? this.futureOwnerProfileId,
+      lastSyncedAt: lastSyncedAt ?? this.lastSyncedAt,
+      remoteRevision: remoteRevision ?? this.remoteRevision,
+    );
+  }
+}
+
+final class MediaAsset {
+  const MediaAsset({
+    required this.metadata,
+    required this.kind,
+    required this.localUri,
+    this.mimeType,
+    this.sizeBytes,
+    this.width,
+    this.height,
+    this.durationMs,
+    this.checksum,
+    this.remoteUri,
+    this.thumbnailLocalUri,
+  });
+
+  final EntityMetadata metadata;
+  final MediaKind kind;
+  final String localUri;
+  final String? mimeType;
+  final int? sizeBytes;
+  final int? width;
+  final int? height;
+  final int? durationMs;
+  final String? checksum;
+  final String? remoteUri;
+  final String? thumbnailLocalUri;
+}
+
+final class Exercise {
+  Exercise({
+    required this.metadata,
+    required String name,
+    this.description,
+    this.imageMediaId,
+    this.videoMediaId,
+    required this.hasTimeMeasure,
+    required this.hasRepsMeasure,
+    required this.hasScoreMeasure,
+    this.scoreLabel,
+    this.scoreUnit,
+    this.archivedAt,
+  }) : name = _nonBlank(name, 'Exercise name') {
+    _requireAtLeastOneMeasure(
+      hasTime: hasTimeMeasure,
+      hasReps: hasRepsMeasure,
+      hasScore: hasScoreMeasure,
+    );
+    if (hasScoreMeasure) {
+      _nonBlank(scoreLabel, 'Score label');
+      _nonBlank(scoreUnit, 'Score unit');
+    }
+  }
+
+  final EntityMetadata metadata;
+  final String name;
+  final String? description;
+  final String? imageMediaId;
+  final String? videoMediaId;
+  final bool hasTimeMeasure;
+  final bool hasRepsMeasure;
+  final bool hasScoreMeasure;
+  final String? scoreLabel;
+  final String? scoreUnit;
+  final DateTime? archivedAt;
+
+  Set<WorkoutMeasure> get availableMeasures => {
+    if (hasTimeMeasure) WorkoutMeasure.time,
+    if (hasRepsMeasure) WorkoutMeasure.reps,
+    if (hasScoreMeasure) WorkoutMeasure.score,
+  };
+
+  Exercise archive(DateTime now) {
+    return copyWith(archivedAt: now, metadata: metadata.touch(now));
+  }
+
+  Exercise copyWith({
+    EntityMetadata? metadata,
+    String? name,
+    String? description,
+    String? imageMediaId,
+    String? videoMediaId,
+    bool? hasTimeMeasure,
+    bool? hasRepsMeasure,
+    bool? hasScoreMeasure,
+    String? scoreLabel,
+    String? scoreUnit,
+    DateTime? archivedAt,
+  }) {
+    return Exercise(
+      metadata: metadata ?? this.metadata,
+      name: name ?? this.name,
+      description: description ?? this.description,
+      imageMediaId: imageMediaId ?? this.imageMediaId,
+      videoMediaId: videoMediaId ?? this.videoMediaId,
+      hasTimeMeasure: hasTimeMeasure ?? this.hasTimeMeasure,
+      hasRepsMeasure: hasRepsMeasure ?? this.hasRepsMeasure,
+      hasScoreMeasure: hasScoreMeasure ?? this.hasScoreMeasure,
+      scoreLabel: scoreLabel ?? this.scoreLabel,
+      scoreUnit: scoreUnit ?? this.scoreUnit,
+      archivedAt: archivedAt ?? this.archivedAt,
+    );
+  }
+}
+
+final class Program {
+  Program({
+    required this.metadata,
+    required String name,
+    required this.defaultRestSeconds,
+    this.exercises = const [],
+  }) : name = _nonBlank(name, 'Program name') {
+    _requireNonNegative(defaultRestSeconds, 'Default rest seconds');
+  }
+
+  final EntityMetadata metadata;
+  final String name;
+  final int defaultRestSeconds;
+  final List<ProgramExercise> exercises;
+
+  Program copyWith({
+    List<ProgramExercise>? exercises,
+    EntityMetadata? metadata,
+  }) {
+    return Program(
+      metadata: metadata ?? this.metadata,
+      name: name,
+      defaultRestSeconds: defaultRestSeconds,
+      exercises: exercises ?? this.exercises,
+    );
+  }
+}
+
+final class ProgramExercise {
+  ProgramExercise({
+    required this.metadata,
+    required this.programId,
+    this.sourceExerciseId,
+    required this.position,
+    required String exerciseNameSnapshot,
+    this.exerciseDescriptionSnapshot,
+    this.exerciseImageMediaIdSnapshot,
+    this.exerciseVideoMediaIdSnapshot,
+    this.exerciseArchivedSnapshot = false,
+    required this.availableTimeSnapshot,
+    required this.availableRepsSnapshot,
+    required this.availableScoreSnapshot,
+    this.scoreLabelSnapshot,
+    this.scoreUnitSnapshot,
+    required this.setsCount,
+    required this.timeEnabled,
+    required this.repsEnabled,
+    required this.scoreEnabled,
+    this.targetTimeSeconds,
+    this.targetReps,
+    this.targetScore,
+    this.restSecondsOverride,
+  }) : exerciseNameSnapshot = _nonBlank(
+         exerciseNameSnapshot,
+         'Exercise snapshot name',
+       ) {
+    _requireNonNegative(position, 'Position');
+    _requirePositive(setsCount, 'Sets count');
+    _requireAtLeastOneMeasure(
+      hasTime: timeEnabled,
+      hasReps: repsEnabled,
+      hasScore: scoreEnabled,
+    );
+    if (timeEnabled && !availableTimeSnapshot) {
+      throw const DomainException('Time is not available on this exercise.');
+    }
+    if (repsEnabled && !availableRepsSnapshot) {
+      throw const DomainException('Reps are not available on this exercise.');
+    }
+    if (scoreEnabled && !availableScoreSnapshot) {
+      throw const DomainException('Score is not available on this exercise.');
+    }
+    _requireNullablePositive(targetTimeSeconds, 'Target time seconds');
+    _requireNullablePositive(targetReps, 'Target reps');
+    _requireNullableNonNegativeDouble(targetScore, 'Target score');
+    _requireNullableNonNegative(restSecondsOverride, 'Rest seconds override');
+  }
+
+  final EntityMetadata metadata;
+  final String programId;
+  final String? sourceExerciseId;
+  final int position;
+  final String exerciseNameSnapshot;
+  final String? exerciseDescriptionSnapshot;
+  final String? exerciseImageMediaIdSnapshot;
+  final String? exerciseVideoMediaIdSnapshot;
+  final bool exerciseArchivedSnapshot;
+  final bool availableTimeSnapshot;
+  final bool availableRepsSnapshot;
+  final bool availableScoreSnapshot;
+  final String? scoreLabelSnapshot;
+  final String? scoreUnitSnapshot;
+  final int setsCount;
+  final bool timeEnabled;
+  final bool repsEnabled;
+  final bool scoreEnabled;
+  final int? targetTimeSeconds;
+  final int? targetReps;
+  final double? targetScore;
+  final int? restSecondsOverride;
+
+  static ProgramExercise snapshotFromExercise({
+    required EntityMetadata metadata,
+    required String programId,
+    required Exercise exercise,
+    required int position,
+    required int setsCount,
+    required Set<WorkoutMeasure> enabledMeasures,
+    int? targetTimeSeconds,
+    int? targetReps,
+    double? targetScore,
+    int? restSecondsOverride,
+  }) {
+    final available = exercise.availableMeasures;
+    if (!available.containsAll(enabledMeasures)) {
+      throw const DomainException(
+        'Enabled measures must be a subset of exercise measures.',
+      );
+    }
+    return ProgramExercise(
+      metadata: metadata,
+      programId: programId,
+      sourceExerciseId: exercise.metadata.id,
+      position: position,
+      exerciseNameSnapshot: exercise.name,
+      exerciseDescriptionSnapshot: exercise.description,
+      exerciseImageMediaIdSnapshot: exercise.imageMediaId,
+      exerciseVideoMediaIdSnapshot: exercise.videoMediaId,
+      exerciseArchivedSnapshot: exercise.archivedAt != null,
+      availableTimeSnapshot: exercise.hasTimeMeasure,
+      availableRepsSnapshot: exercise.hasRepsMeasure,
+      availableScoreSnapshot: exercise.hasScoreMeasure,
+      scoreLabelSnapshot: exercise.scoreLabel,
+      scoreUnitSnapshot: exercise.scoreUnit,
+      setsCount: setsCount,
+      timeEnabled: enabledMeasures.contains(WorkoutMeasure.time),
+      repsEnabled: enabledMeasures.contains(WorkoutMeasure.reps),
+      scoreEnabled: enabledMeasures.contains(WorkoutMeasure.score),
+      targetTimeSeconds: targetTimeSeconds,
+      targetReps: targetReps,
+      targetScore: targetScore,
+      restSecondsOverride: restSecondsOverride,
+    );
+  }
+
+  Map<String, Object?> toSnapshotJson() => {
+    'id': metadata.id,
+    'sourceExerciseId': sourceExerciseId,
+    'position': position,
+    'exerciseNameSnapshot': exerciseNameSnapshot,
+    'exerciseDescriptionSnapshot': exerciseDescriptionSnapshot,
+    'exerciseImageMediaIdSnapshot': exerciseImageMediaIdSnapshot,
+    'exerciseVideoMediaIdSnapshot': exerciseVideoMediaIdSnapshot,
+    'exerciseArchivedSnapshot': exerciseArchivedSnapshot,
+    'availableTimeSnapshot': availableTimeSnapshot,
+    'availableRepsSnapshot': availableRepsSnapshot,
+    'availableScoreSnapshot': availableScoreSnapshot,
+    'scoreLabelSnapshot': scoreLabelSnapshot,
+    'scoreUnitSnapshot': scoreUnitSnapshot,
+    'setsCount': setsCount,
+    'timeEnabled': timeEnabled,
+    'repsEnabled': repsEnabled,
+    'scoreEnabled': scoreEnabled,
+    'targetTimeSeconds': targetTimeSeconds,
+    'targetReps': targetReps,
+    'targetScore': targetScore,
+    'restSecondsOverride': restSecondsOverride,
+  };
+}
+
+final class WorkoutTemplate {
+  WorkoutTemplate({
+    required this.metadata,
+    required String name,
+    this.lastStartedAt,
+    this.programs = const [],
+    this.overrides = const [],
+  }) : name = _nonBlank(name, 'Workout template name');
+
+  final EntityMetadata metadata;
+  final String name;
+  final DateTime? lastStartedAt;
+  final List<WorkoutTemplateProgram> programs;
+  final List<WorkoutTemplateExerciseOverride> overrides;
+}
+
+final class WorkoutTemplateProgram {
+  WorkoutTemplateProgram({
+    required this.metadata,
+    required this.workoutTemplateId,
+    this.sourceProgramId,
+    required this.position,
+    required String programNameSnapshot,
+    required this.defaultRestSecondsSnapshot,
+    required this.programSnapshotJson,
+  }) : programNameSnapshot = _nonBlank(
+         programNameSnapshot,
+         'Program snapshot name',
+       ) {
+    _requireNonNegative(position, 'Position');
+    _requireNonNegative(defaultRestSecondsSnapshot, 'Default rest seconds');
+  }
+
+  final EntityMetadata metadata;
+  final String workoutTemplateId;
+  final String? sourceProgramId;
+  final int position;
+  final String programNameSnapshot;
+  final int defaultRestSecondsSnapshot;
+  final String programSnapshotJson;
+
+  static WorkoutTemplateProgram snapshotFromProgram({
+    required EntityMetadata metadata,
+    required String workoutTemplateId,
+    required Program program,
+    required int position,
+  }) {
+    return WorkoutTemplateProgram(
+      metadata: metadata,
+      workoutTemplateId: workoutTemplateId,
+      sourceProgramId: program.metadata.id,
+      position: position,
+      programNameSnapshot: program.name,
+      defaultRestSecondsSnapshot: program.defaultRestSeconds,
+      programSnapshotJson: jsonEncode({
+        'programId': program.metadata.id,
+        'name': program.name,
+        'defaultRestSeconds': program.defaultRestSeconds,
+        'exercises': program.exercises
+            .map((exercise) => exercise.toSnapshotJson())
+            .toList(),
+      }),
+    );
+  }
+}
+
+final class WorkoutTemplateExerciseOverride {
+  WorkoutTemplateExerciseOverride({
+    required this.metadata,
+    required this.workoutTemplateProgramId,
+    required String snapshotProgramExerciseId,
+    this.setsCountOverride,
+    this.targetTimeSecondsOverride,
+    this.targetRepsOverride,
+    this.targetScoreOverride,
+  }) : snapshotProgramExerciseId = _nonBlank(
+         snapshotProgramExerciseId,
+         'Snapshot program exercise id',
+       ) {
+    _requireNullablePositive(setsCountOverride, 'Sets count override');
+    _requireNullablePositive(
+      targetTimeSecondsOverride,
+      'Target time seconds override',
+    );
+    _requireNullablePositive(targetRepsOverride, 'Target reps override');
+    _requireNullableNonNegativeDouble(
+      targetScoreOverride,
+      'Target score override',
+    );
+  }
+
+  final EntityMetadata metadata;
+  final String workoutTemplateProgramId;
+  final String snapshotProgramExerciseId;
+  final int? setsCountOverride;
+  final int? targetTimeSecondsOverride;
+  final int? targetRepsOverride;
+  final double? targetScoreOverride;
+}
+
+final class ActiveWorkoutSession {
+  ActiveWorkoutSession({
+    required this.metadata,
+    this.sourceWorkoutTemplateId,
+    required this.status,
+    required this.startedAt,
+    this.pausedAt,
+    this.endedAt,
+    required this.lastPersistedAt,
+    required this.elapsedActiveMs,
+    required this.currentProgramIndex,
+    required this.currentExerciseIndex,
+    required this.currentSetIndex,
+    required this.resolvedTemplateSnapshotJson,
+  }) {
+    _requireNonNegative(elapsedActiveMs, 'Elapsed active milliseconds');
+    _requireNonNegative(currentProgramIndex, 'Current program index');
+    _requireNonNegative(currentExerciseIndex, 'Current exercise index');
+    _requireNonNegative(currentSetIndex, 'Current set index');
+  }
+
+  final EntityMetadata metadata;
+  final String? sourceWorkoutTemplateId;
+  final ActiveWorkoutStatus status;
+  final DateTime startedAt;
+  final DateTime? pausedAt;
+  final DateTime? endedAt;
+  final DateTime lastPersistedAt;
+  final int elapsedActiveMs;
+  final int currentProgramIndex;
+  final int currentExerciseIndex;
+  final int currentSetIndex;
+  final String resolvedTemplateSnapshotJson;
+
+  int elapsedActiveMillisecondsAt(DateTime now) {
+    if (status != ActiveWorkoutStatus.running) {
+      return elapsedActiveMs;
+    }
+    return elapsedActiveMs + now.difference(lastPersistedAt).inMilliseconds;
+  }
+
+  ActiveWorkoutSession pause(DateTime now) {
+    return copyWith(
+      status: ActiveWorkoutStatus.paused,
+      pausedAt: now,
+      lastPersistedAt: now,
+      elapsedActiveMs: elapsedActiveMillisecondsAt(now),
+      metadata: metadata.touch(now),
+    );
+  }
+
+  ActiveWorkoutSession resume(DateTime now) {
+    return ActiveWorkoutSession(
+      metadata: metadata.touch(now),
+      sourceWorkoutTemplateId: sourceWorkoutTemplateId,
+      status: ActiveWorkoutStatus.running,
+      startedAt: startedAt,
+      pausedAt: null,
+      endedAt: endedAt,
+      lastPersistedAt: now,
+      elapsedActiveMs: elapsedActiveMs,
+      currentProgramIndex: currentProgramIndex,
+      currentExerciseIndex: currentExerciseIndex,
+      currentSetIndex: currentSetIndex,
+      resolvedTemplateSnapshotJson: resolvedTemplateSnapshotJson,
+    );
+  }
+
+  ActiveWorkoutSession copyWith({
+    EntityMetadata? metadata,
+    ActiveWorkoutStatus? status,
+    DateTime? pausedAt,
+    DateTime? endedAt,
+    DateTime? lastPersistedAt,
+    int? elapsedActiveMs,
+    int? currentProgramIndex,
+    int? currentExerciseIndex,
+    int? currentSetIndex,
+  }) {
+    return ActiveWorkoutSession(
+      metadata: metadata ?? this.metadata,
+      sourceWorkoutTemplateId: sourceWorkoutTemplateId,
+      status: status ?? this.status,
+      startedAt: startedAt,
+      pausedAt: pausedAt,
+      endedAt: endedAt ?? this.endedAt,
+      lastPersistedAt: lastPersistedAt ?? this.lastPersistedAt,
+      elapsedActiveMs: elapsedActiveMs ?? this.elapsedActiveMs,
+      currentProgramIndex: currentProgramIndex ?? this.currentProgramIndex,
+      currentExerciseIndex: currentExerciseIndex ?? this.currentExerciseIndex,
+      currentSetIndex: currentSetIndex ?? this.currentSetIndex,
+      resolvedTemplateSnapshotJson: resolvedTemplateSnapshotJson,
+    );
+  }
+}
+
+final class ActiveSetResult {
+  const ActiveSetResult({
+    required this.metadata,
+    required this.activeWorkoutSessionId,
+    required this.programSnapshotId,
+    required this.exerciseSnapshotId,
+    required this.programIndex,
+    required this.exerciseIndex,
+    required this.setIndex,
+    this.startedAt,
+    this.completedAt,
+    this.actualTimeMs,
+    this.actualReps,
+    this.actualScore,
+    this.scoreLabelSnapshot,
+    this.scoreUnitSnapshot,
+    this.note,
+  });
+
+  final EntityMetadata metadata;
+  final String activeWorkoutSessionId;
+  final String programSnapshotId;
+  final String exerciseSnapshotId;
+  final int programIndex;
+  final int exerciseIndex;
+  final int setIndex;
+  final DateTime? startedAt;
+  final DateTime? completedAt;
+  final int? actualTimeMs;
+  final int? actualReps;
+  final double? actualScore;
+  final String? scoreLabelSnapshot;
+  final String? scoreUnitSnapshot;
+  final String? note;
+}
+
+final class ActiveRestState {
+  const ActiveRestState({
+    required this.metadata,
+    required this.activeWorkoutSessionId,
+    required this.afterProgramIndex,
+    required this.afterExerciseIndex,
+    required this.afterSetIndex,
+    required this.plannedRestSeconds,
+    required this.adjustedRestSeconds,
+    required this.startedAt,
+    this.endedAt,
+    this.skippedAt,
+  });
+
+  final EntityMetadata metadata;
+  final String activeWorkoutSessionId;
+  final int afterProgramIndex;
+  final int afterExerciseIndex;
+  final int afterSetIndex;
+  final int plannedRestSeconds;
+  final int adjustedRestSeconds;
+  final DateTime startedAt;
+  final DateTime? endedAt;
+  final DateTime? skippedAt;
+}
+
+final class WorkoutHistory {
+  const WorkoutHistory({
+    required this.metadata,
+    this.sourceWorkoutTemplateId,
+    this.sourceActiveWorkoutSessionId,
+    required this.nameSnapshot,
+    required this.startedAt,
+    required this.endedAt,
+    required this.totalActiveMs,
+    required this.completed,
+    required this.historySnapshotJson,
+    this.results = const [],
+  });
+
+  final EntityMetadata metadata;
+  final String? sourceWorkoutTemplateId;
+  final String? sourceActiveWorkoutSessionId;
+  final String nameSnapshot;
+  final DateTime startedAt;
+  final DateTime endedAt;
+  final int totalActiveMs;
+  final bool completed;
+  final String historySnapshotJson;
+  final List<WorkoutHistorySetResult> results;
+}
+
+final class WorkoutHistorySetResult {
+  const WorkoutHistorySetResult({
+    required this.metadata,
+    required this.workoutHistoryId,
+    required this.programSnapshotId,
+    required this.exerciseSnapshotId,
+    required this.programIndex,
+    required this.exerciseIndex,
+    required this.setIndex,
+    required this.programNameSnapshot,
+    required this.exerciseNameSnapshot,
+    required this.timeEnabledSnapshot,
+    required this.repsEnabledSnapshot,
+    required this.scoreEnabledSnapshot,
+    this.targetTimeSecondsSnapshot,
+    this.targetRepsSnapshot,
+    this.targetScoreSnapshot,
+    this.actualTimeMs,
+    this.actualReps,
+    this.actualScore,
+    this.scoreLabelSnapshot,
+    this.scoreUnitSnapshot,
+    this.startedAt,
+    this.completedAt,
+  });
+
+  final EntityMetadata metadata;
+  final String workoutHistoryId;
+  final String programSnapshotId;
+  final String exerciseSnapshotId;
+  final int programIndex;
+  final int exerciseIndex;
+  final int setIndex;
+  final String programNameSnapshot;
+  final String exerciseNameSnapshot;
+  final bool timeEnabledSnapshot;
+  final bool repsEnabledSnapshot;
+  final bool scoreEnabledSnapshot;
+  final int? targetTimeSecondsSnapshot;
+  final int? targetRepsSnapshot;
+  final double? targetScoreSnapshot;
+  final int? actualTimeMs;
+  final int? actualReps;
+  final double? actualScore;
+  final String? scoreLabelSnapshot;
+  final String? scoreUnitSnapshot;
+  final DateTime? startedAt;
+  final DateTime? completedAt;
+}
+
+String _nonBlank(String? value, String label) {
+  final trimmed = value?.trim();
+  if (trimmed == null || trimmed.isEmpty) {
+    throw DomainException('$label must not be blank.');
+  }
+  return trimmed;
+}
+
+void _requireAtLeastOneMeasure({
+  required bool hasTime,
+  required bool hasReps,
+  required bool hasScore,
+}) {
+  if (!hasTime && !hasReps && !hasScore) {
+    throw const DomainException('At least one measure must be active.');
+  }
+}
+
+void _requirePositive(int value, String label) {
+  if (value <= 0) {
+    throw DomainException('$label must be positive.');
+  }
+}
+
+void _requireNonNegative(int value, String label) {
+  if (value < 0) {
+    throw DomainException('$label must not be negative.');
+  }
+}
+
+void _requireNullablePositive(int? value, String label) {
+  if (value != null) {
+    _requirePositive(value, label);
+  }
+}
+
+void _requireNullableNonNegative(int? value, String label) {
+  if (value != null) {
+    _requireNonNegative(value, label);
+  }
+}
+
+void _requireNullableNonNegativeDouble(double? value, String label) {
+  if (value != null && value < 0) {
+    throw DomainException('$label must not be negative.');
+  }
+}
diff --git a/lib/infrastructure/local/drift_repositories.dart b/lib/infrastructure/local/drift_repositories.dart
new file mode 100644
index 0000000..35e212d
--- /dev/null
+++ b/lib/infrastructure/local/drift_repositories.dart
@@ -0,0 +1,751 @@
+import 'package:drift/drift.dart';
+
+import '../../application/application.dart';
+import '../../domain/domain.dart' as domain;
+import 'app_database.dart' as db;
+
+final class DriftExerciseRepository implements ExerciseRepository {
+  const DriftExerciseRepository(this.database);
+
+  final db.AppDatabase database;
+
+  @override
+  Future<domain.Exercise?> findById(String id) async {
+    final row = await (database.select(
+      database.exercises,
+    )..where((table) => table.id.equals(id))).getSingleOrNull();
+    return row == null ? null : _exerciseFromRow(row);
+  }
+
+  @override
+  Future<List<domain.Exercise>> listActive() async {
+    final rows =
+        await (database.select(database.exercises)
+              ..where((table) => table.deletedAt.isNull())
+              ..orderBy([(table) => OrderingTerm.asc(table.name)]))
+            .get();
+    return rows.map(_exerciseFromRow).toList();
+  }
+
+  @override
+  Future<void> save(domain.Exercise exercise) async {
+    await database
+        .into(database.exercises)
+        .insertOnConflictUpdate(_exerciseCompanion(exercise));
+  }
+}
+
+final class DriftProgramRepository implements ProgramRepository {
+  const DriftProgramRepository(this.database);
+
+  final db.AppDatabase database;
+
+  @override
+  Future<domain.Program?> findById(String id) async {
+    final row = await (database.select(
+      database.programs,
+    )..where((table) => table.id.equals(id))).getSingleOrNull();
+    if (row == null) {
+      return null;
+    }
+    final exercises =
+        await (database.select(database.programExercises)
+              ..where((table) => table.programId.equals(id))
+              ..orderBy([(table) => OrderingTerm.asc(table.position)]))
+            .get();
+    return _programFromRow(
+      row,
+      exercises.map(_programExerciseFromRow).toList(),
+    );
+  }
+
+  @override
+  Future<void> save(domain.Program program) async {
+    await database
+        .into(database.programs)
+        .insertOnConflictUpdate(_programCompanion(program));
+    for (final exercise in program.exercises) {
+      await saveExercise(exercise);
+    }
+  }
+
+  @override
+  Future<void> saveExercise(domain.ProgramExercise exercise) async {
+    await database
+        .into(database.programExercises)
+        .insertOnConflictUpdate(_programExerciseCompanion(exercise));
+  }
+}
+
+final class DriftWorkoutTemplateRepository
+    implements WorkoutTemplateRepository {
+  const DriftWorkoutTemplateRepository(this.database);
+
+  final db.AppDatabase database;
+
+  @override
+  Future<domain.WorkoutTemplate?> findById(String id) async {
+    final row = await (database.select(
+      database.workoutTemplates,
+    )..where((table) => table.id.equals(id))).getSingleOrNull();
+    if (row == null) {
+      return null;
+    }
+    final programs =
+        await (database.select(database.workoutTemplatePrograms)
+              ..where((table) => table.workoutTemplateId.equals(id))
+              ..orderBy([(table) => OrderingTerm.asc(table.position)]))
+            .get();
+    final programIds = programs.map((program) => program.id).toSet();
+    final overrides = await (database.select(
+      database.workoutTemplateExerciseOverrides,
+    )..where((table) => table.workoutTemplateProgramId.isIn(programIds))).get();
+    return _workoutTemplateFromRow(
+      row,
+      programs.map(_workoutTemplateProgramFromRow).toList(),
+      overrides.map(_workoutTemplateExerciseOverrideFromRow).toList(),
+    );
+  }
+
+  @override
+  Future<void> save(domain.WorkoutTemplate template) async {
+    await database
+        .into(database.workoutTemplates)
+        .insertOnConflictUpdate(_workoutTemplateCompanion(template));
+    for (final program in template.programs) {
+      await saveProgram(program);
+    }
+    for (final override in template.overrides) {
+      await saveOverride(override);
+    }
+  }
+
+  @override
+  Future<void> saveProgram(domain.WorkoutTemplateProgram program) async {
+    await database
+        .into(database.workoutTemplatePrograms)
+        .insertOnConflictUpdate(_workoutTemplateProgramCompanion(program));
+  }
+
+  @override
+  Future<void> saveOverride(
+    domain.WorkoutTemplateExerciseOverride override,
+  ) async {
+    await database
+        .into(database.workoutTemplateExerciseOverrides)
+        .insertOnConflictUpdate(
+          _workoutTemplateExerciseOverrideCompanion(override),
+        );
+  }
+}
+
+final class DriftActiveSessionRepository implements ActiveSessionRepository {
+  const DriftActiveSessionRepository(this.database);
+
+  final db.AppDatabase database;
+
+  @override
+  Future<domain.ActiveWorkoutSession?> findById(String id) async {
+    final row = await (database.select(
+      database.activeWorkoutSessions,
+    )..where((table) => table.id.equals(id))).getSingleOrNull();
+    return row == null ? null : _activeWorkoutSessionFromRow(row);
+  }
+
+  @override
+  Future<void> save(domain.ActiveWorkoutSession session) async {
+    await database
+        .into(database.activeWorkoutSessions)
+        .insertOnConflictUpdate(_activeWorkoutSessionCompanion(session));
+  }
+
+  @override
+  Future<void> saveSetResult(domain.ActiveSetResult result) async {
+    await database
+        .into(database.activeSetResults)
+        .insertOnConflictUpdate(_activeSetResultCompanion(result));
+  }
+
+  @override
+  Future<void> saveRestState(domain.ActiveRestState restState) async {
+    await database
+        .into(database.activeRestStates)
+        .insertOnConflictUpdate(_activeRestStateCompanion(restState));
+  }
+
+  @override
+  Future<List<domain.ActiveSetResult>> listSetResults(String sessionId) async {
+    final rows =
+        await (database.select(database.activeSetResults)
+              ..where((table) => table.activeWorkoutSessionId.equals(sessionId))
+              ..orderBy([
+                (table) => OrderingTerm.asc(table.programIndex),
+                (table) => OrderingTerm.asc(table.exerciseIndex),
+                (table) => OrderingTerm.asc(table.setIndex),
+              ]))
+            .get();
+    return rows.map(_activeSetResultFromRow).toList();
+  }
+
+  @override
+  Future<List<domain.ActiveRestState>> listRestStates(String sessionId) async {
+    final rows =
+        await (database.select(database.activeRestStates)
+              ..where((table) => table.activeWorkoutSessionId.equals(sessionId))
+              ..orderBy([(table) => OrderingTerm.asc(table.startedAt)]))
+            .get();
+    return rows.map(_activeRestStateFromRow).toList();
+  }
+}
+
+final class DriftWorkoutHistoryRepository implements WorkoutHistoryRepository {
+  const DriftWorkoutHistoryRepository(this.database);
+
+  final db.AppDatabase database;
+
+  @override
+  Future<void> save(domain.WorkoutHistory history) async {
+    await database
+        .into(database.workoutHistories)
+        .insertOnConflictUpdate(_workoutHistoryCompanion(history));
+    for (final result in history.results) {
+      await saveSetResult(result);
+    }
+  }
+
+  @override
+  Future<void> saveSetResult(domain.WorkoutHistorySetResult result) async {
+    await database
+        .into(database.workoutHistorySetResults)
+        .insertOnConflictUpdate(_workoutHistorySetResultCompanion(result));
+  }
+}
+
+domain.EntityMetadata _metadataFromRow(dynamic row) {
+  return domain.EntityMetadata(
+    id: row.id as String,
+    createdAt: row.createdAt as DateTime,
+    updatedAt: row.updatedAt as DateTime,
+    deletedAt: row.deletedAt as DateTime?,
+    schemaVersion: row.schemaVersion as int,
+    syncState: _syncStateFromDb(row.syncState as String),
+    localRevision: row.localRevision as int,
+    originDeviceId: row.originDeviceId as String,
+    futureOwnerProfileId: row.futureOwnerProfileId as String?,
+    lastSyncedAt: row.lastSyncedAt as DateTime?,
+    remoteRevision: row.remoteRevision as String?,
+  );
+}
+
+List<Value<Object?>> _metadataValues(domain.EntityMetadata metadata) => [
+  Value(metadata.id),
+  Value(metadata.createdAt),
+  Value(metadata.updatedAt),
+  Value(metadata.deletedAt),
+  Value(metadata.schemaVersion),
+  Value(_syncStateToDb(metadata.syncState)),
+  Value(metadata.localRevision),
+  Value(metadata.originDeviceId),
+  Value(metadata.futureOwnerProfileId),
+  Value(metadata.lastSyncedAt),
+  Value(metadata.remoteRevision),
+];
+
+db.ExercisesCompanion _exerciseCompanion(domain.Exercise exercise) {
+  final values = _metadataValues(exercise.metadata);
+  return db.ExercisesCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    name: Value(exercise.name),
+    description: Value(exercise.description),
+    imageMediaId: Value(exercise.imageMediaId),
+    videoMediaId: Value(exercise.videoMediaId),
+    hasTimeMeasure: Value(exercise.hasTimeMeasure),
+    hasRepsMeasure: Value(exercise.hasRepsMeasure),
+    hasScoreMeasure: Value(exercise.hasScoreMeasure),
+    scoreLabel: Value(exercise.scoreLabel),
+    scoreUnit: Value(exercise.scoreUnit),
+    archivedAt: Value(exercise.archivedAt),
+  );
+}
+
+domain.Exercise _exerciseFromRow(db.Exercise row) {
+  return domain.Exercise(
+    metadata: _metadataFromRow(row),
+    name: row.name,
+    description: row.description,
+    imageMediaId: row.imageMediaId,
+    videoMediaId: row.videoMediaId,
+    hasTimeMeasure: row.hasTimeMeasure,
+    hasRepsMeasure: row.hasRepsMeasure,
+    hasScoreMeasure: row.hasScoreMeasure,
+    scoreLabel: row.scoreLabel,
+    scoreUnit: row.scoreUnit,
+    archivedAt: row.archivedAt,
+  );
+}
+
+db.ProgramsCompanion _programCompanion(domain.Program program) {
+  final values = _metadataValues(program.metadata);
+  return db.ProgramsCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    name: Value(program.name),
+    defaultRestSeconds: Value(program.defaultRestSeconds),
+  );
+}
+
+domain.Program _programFromRow(
+  db.Program row,
+  List<domain.ProgramExercise> exercises,
+) {
+  return domain.Program(
+    metadata: _metadataFromRow(row),
+    name: row.name,
+    defaultRestSeconds: row.defaultRestSeconds,
+    exercises: exercises,
+  );
+}
+
+db.ProgramExercisesCompanion _programExerciseCompanion(
+  domain.ProgramExercise exercise,
+) {
+  final values = _metadataValues(exercise.metadata);
+  return db.ProgramExercisesCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    programId: Value(exercise.programId),
+    sourceExerciseId: Value(exercise.sourceExerciseId),
+    position: Value(exercise.position),
+    exerciseNameSnapshot: Value(exercise.exerciseNameSnapshot),
+    exerciseDescriptionSnapshot: Value(exercise.exerciseDescriptionSnapshot),
+    exerciseImageMediaIdSnapshot: Value(exercise.exerciseImageMediaIdSnapshot),
+    exerciseVideoMediaIdSnapshot: Value(exercise.exerciseVideoMediaIdSnapshot),
+    exerciseArchivedSnapshot: Value(exercise.exerciseArchivedSnapshot),
+    availableTimeSnapshot: Value(exercise.availableTimeSnapshot),
+    availableRepsSnapshot: Value(exercise.availableRepsSnapshot),
+    availableScoreSnapshot: Value(exercise.availableScoreSnapshot),
+    scoreLabelSnapshot: Value(exercise.scoreLabelSnapshot),
+    scoreUnitSnapshot: Value(exercise.scoreUnitSnapshot),
+    setsCount: Value(exercise.setsCount),
+    timeEnabled: Value(exercise.timeEnabled),
+    repsEnabled: Value(exercise.repsEnabled),
+    scoreEnabled: Value(exercise.scoreEnabled),
+    targetTimeSeconds: Value(exercise.targetTimeSeconds),
+    targetReps: Value(exercise.targetReps),
+    targetScore: Value(exercise.targetScore),
+    restSecondsOverride: Value(exercise.restSecondsOverride),
+  );
+}
+
+domain.ProgramExercise _programExerciseFromRow(db.ProgramExercise row) {
+  return domain.ProgramExercise(
+    metadata: _metadataFromRow(row),
+    programId: row.programId,
+    sourceExerciseId: row.sourceExerciseId,
+    position: row.position,
+    exerciseNameSnapshot: row.exerciseNameSnapshot,
+    exerciseDescriptionSnapshot: row.exerciseDescriptionSnapshot,
+    exerciseImageMediaIdSnapshot: row.exerciseImageMediaIdSnapshot,
+    exerciseVideoMediaIdSnapshot: row.exerciseVideoMediaIdSnapshot,
+    exerciseArchivedSnapshot: row.exerciseArchivedSnapshot,
+    availableTimeSnapshot: row.availableTimeSnapshot,
+    availableRepsSnapshot: row.availableRepsSnapshot,
+    availableScoreSnapshot: row.availableScoreSnapshot,
+    scoreLabelSnapshot: row.scoreLabelSnapshot,
+    scoreUnitSnapshot: row.scoreUnitSnapshot,
+    setsCount: row.setsCount,
+    timeEnabled: row.timeEnabled,
+    repsEnabled: row.repsEnabled,
+    scoreEnabled: row.scoreEnabled,
+    targetTimeSeconds: row.targetTimeSeconds,
+    targetReps: row.targetReps,
+    targetScore: row.targetScore,
+    restSecondsOverride: row.restSecondsOverride,
+  );
+}
+
+db.WorkoutTemplatesCompanion _workoutTemplateCompanion(
+  domain.WorkoutTemplate template,
+) {
+  final values = _metadataValues(template.metadata);
+  return db.WorkoutTemplatesCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    name: Value(template.name),
+    lastStartedAt: Value(template.lastStartedAt),
+  );
+}
+
+domain.WorkoutTemplate _workoutTemplateFromRow(
+  db.WorkoutTemplate row,
+  List<domain.WorkoutTemplateProgram> programs,
+  List<domain.WorkoutTemplateExerciseOverride> overrides,
+) {
+  return domain.WorkoutTemplate(
+    metadata: _metadataFromRow(row),
+    name: row.name,
+    lastStartedAt: row.lastStartedAt,
+    programs: programs,
+    overrides: overrides,
+  );
+}
+
+db.WorkoutTemplateProgramsCompanion _workoutTemplateProgramCompanion(
+  domain.WorkoutTemplateProgram program,
+) {
+  final values = _metadataValues(program.metadata);
+  return db.WorkoutTemplateProgramsCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    workoutTemplateId: Value(program.workoutTemplateId),
+    sourceProgramId: Value(program.sourceProgramId),
+    position: Value(program.position),
+    programNameSnapshot: Value(program.programNameSnapshot),
+    defaultRestSecondsSnapshot: Value(program.defaultRestSecondsSnapshot),
+    programSnapshotJson: Value(program.programSnapshotJson),
+  );
+}
+
+domain.WorkoutTemplateProgram _workoutTemplateProgramFromRow(
+  db.WorkoutTemplateProgram row,
+) {
+  return domain.WorkoutTemplateProgram(
+    metadata: _metadataFromRow(row),
+    workoutTemplateId: row.workoutTemplateId,
+    sourceProgramId: row.sourceProgramId,
+    position: row.position,
+    programNameSnapshot: row.programNameSnapshot,
+    defaultRestSecondsSnapshot: row.defaultRestSecondsSnapshot,
+    programSnapshotJson: row.programSnapshotJson,
+  );
+}
+
+db.WorkoutTemplateExerciseOverridesCompanion
+_workoutTemplateExerciseOverrideCompanion(
+  domain.WorkoutTemplateExerciseOverride override,
+) {
+  final values = _metadataValues(override.metadata);
+  return db.WorkoutTemplateExerciseOverridesCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    workoutTemplateProgramId: Value(override.workoutTemplateProgramId),
+    snapshotProgramExerciseId: Value(override.snapshotProgramExerciseId),
+    setsCountOverride: Value(override.setsCountOverride),
+    targetTimeSecondsOverride: Value(override.targetTimeSecondsOverride),
+    targetRepsOverride: Value(override.targetRepsOverride),
+    targetScoreOverride: Value(override.targetScoreOverride),
+  );
+}
+
+domain.WorkoutTemplateExerciseOverride _workoutTemplateExerciseOverrideFromRow(
+  db.WorkoutTemplateExerciseOverride row,
+) {
+  return domain.WorkoutTemplateExerciseOverride(
+    metadata: _metadataFromRow(row),
+    workoutTemplateProgramId: row.workoutTemplateProgramId,
+    snapshotProgramExerciseId: row.snapshotProgramExerciseId,
+    setsCountOverride: row.setsCountOverride,
+    targetTimeSecondsOverride: row.targetTimeSecondsOverride,
+    targetRepsOverride: row.targetRepsOverride,
+    targetScoreOverride: row.targetScoreOverride,
+  );
+}
+
+db.ActiveWorkoutSessionsCompanion _activeWorkoutSessionCompanion(
+  domain.ActiveWorkoutSession session,
+) {
+  final values = _metadataValues(session.metadata);
+  return db.ActiveWorkoutSessionsCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    sourceWorkoutTemplateId: Value(session.sourceWorkoutTemplateId),
+    status: Value(_activeStatusToDb(session.status)),
+    startedAt: Value(session.startedAt),
+    pausedAt: Value(session.pausedAt),
+    endedAt: Value(session.endedAt),
+    lastPersistedAt: Value(session.lastPersistedAt),
+    elapsedActiveMs: Value(session.elapsedActiveMs),
+    currentProgramIndex: Value(session.currentProgramIndex),
+    currentExerciseIndex: Value(session.currentExerciseIndex),
+    currentSetIndex: Value(session.currentSetIndex),
+    resolvedTemplateSnapshotJson: Value(session.resolvedTemplateSnapshotJson),
+  );
+}
+
+domain.ActiveWorkoutSession _activeWorkoutSessionFromRow(
+  db.ActiveWorkoutSession row,
+) {
+  return domain.ActiveWorkoutSession(
+    metadata: _metadataFromRow(row),
+    sourceWorkoutTemplateId: row.sourceWorkoutTemplateId,
+    status: _activeStatusFromDb(row.status),
+    startedAt: row.startedAt,
+    pausedAt: row.pausedAt,
+    endedAt: row.endedAt,
+    lastPersistedAt: row.lastPersistedAt,
+    elapsedActiveMs: row.elapsedActiveMs,
+    currentProgramIndex: row.currentProgramIndex,
+    currentExerciseIndex: row.currentExerciseIndex,
+    currentSetIndex: row.currentSetIndex,
+    resolvedTemplateSnapshotJson: row.resolvedTemplateSnapshotJson,
+  );
+}
+
+db.ActiveSetResultsCompanion _activeSetResultCompanion(
+  domain.ActiveSetResult result,
+) {
+  final values = _metadataValues(result.metadata);
+  return db.ActiveSetResultsCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    activeWorkoutSessionId: Value(result.activeWorkoutSessionId),
+    programSnapshotId: Value(result.programSnapshotId),
+    exerciseSnapshotId: Value(result.exerciseSnapshotId),
+    programIndex: Value(result.programIndex),
+    exerciseIndex: Value(result.exerciseIndex),
+    setIndex: Value(result.setIndex),
+    startedAt: Value(result.startedAt),
+    completedAt: Value(result.completedAt),
+    actualTimeMs: Value(result.actualTimeMs),
+    actualReps: Value(result.actualReps),
+    actualScore: Value(result.actualScore),
+    scoreLabelSnapshot: Value(result.scoreLabelSnapshot),
+    scoreUnitSnapshot: Value(result.scoreUnitSnapshot),
+    note: Value(result.note),
+  );
+}
+
+domain.ActiveSetResult _activeSetResultFromRow(db.ActiveSetResult row) {
+  return domain.ActiveSetResult(
+    metadata: _metadataFromRow(row),
+    activeWorkoutSessionId: row.activeWorkoutSessionId,
+    programSnapshotId: row.programSnapshotId,
+    exerciseSnapshotId: row.exerciseSnapshotId,
+    programIndex: row.programIndex,
+    exerciseIndex: row.exerciseIndex,
+    setIndex: row.setIndex,
+    startedAt: row.startedAt,
+    completedAt: row.completedAt,
+    actualTimeMs: row.actualTimeMs,
+    actualReps: row.actualReps,
+    actualScore: row.actualScore,
+    scoreLabelSnapshot: row.scoreLabelSnapshot,
+    scoreUnitSnapshot: row.scoreUnitSnapshot,
+    note: row.note,
+  );
+}
+
+db.ActiveRestStatesCompanion _activeRestStateCompanion(
+  domain.ActiveRestState restState,
+) {
+  final values = _metadataValues(restState.metadata);
+  return db.ActiveRestStatesCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    activeWorkoutSessionId: Value(restState.activeWorkoutSessionId),
+    afterProgramIndex: Value(restState.afterProgramIndex),
+    afterExerciseIndex: Value(restState.afterExerciseIndex),
+    afterSetIndex: Value(restState.afterSetIndex),
+    plannedRestSeconds: Value(restState.plannedRestSeconds),
+    adjustedRestSeconds: Value(restState.adjustedRestSeconds),
+    startedAt: Value(restState.startedAt),
+    endedAt: Value(restState.endedAt),
+    skippedAt: Value(restState.skippedAt),
+  );
+}
+
+domain.ActiveRestState _activeRestStateFromRow(db.ActiveRestState row) {
+  return domain.ActiveRestState(
+    metadata: _metadataFromRow(row),
+    activeWorkoutSessionId: row.activeWorkoutSessionId,
+    afterProgramIndex: row.afterProgramIndex,
+    afterExerciseIndex: row.afterExerciseIndex,
+    afterSetIndex: row.afterSetIndex,
+    plannedRestSeconds: row.plannedRestSeconds,
+    adjustedRestSeconds: row.adjustedRestSeconds,
+    startedAt: row.startedAt,
+    endedAt: row.endedAt,
+    skippedAt: row.skippedAt,
+  );
+}
+
+db.WorkoutHistoriesCompanion _workoutHistoryCompanion(
+  domain.WorkoutHistory history,
+) {
+  final values = _metadataValues(history.metadata);
+  return db.WorkoutHistoriesCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    sourceWorkoutTemplateId: Value(history.sourceWorkoutTemplateId),
+    sourceActiveWorkoutSessionId: Value(history.sourceActiveWorkoutSessionId),
+    nameSnapshot: Value(history.nameSnapshot),
+    startedAt: Value(history.startedAt),
+    endedAt: Value(history.endedAt),
+    totalActiveMs: Value(history.totalActiveMs),
+    completed: Value(history.completed),
+    historySnapshotJson: Value(history.historySnapshotJson),
+  );
+}
+
+db.WorkoutHistorySetResultsCompanion _workoutHistorySetResultCompanion(
+  domain.WorkoutHistorySetResult result,
+) {
+  final values = _metadataValues(result.metadata);
+  return db.WorkoutHistorySetResultsCompanion(
+    id: values[0] as Value<String>,
+    createdAt: values[1] as Value<DateTime>,
+    updatedAt: values[2] as Value<DateTime>,
+    deletedAt: values[3] as Value<DateTime?>,
+    schemaVersion: values[4] as Value<int>,
+    syncState: values[5] as Value<String>,
+    localRevision: values[6] as Value<int>,
+    originDeviceId: values[7] as Value<String>,
+    futureOwnerProfileId: values[8] as Value<String?>,
+    lastSyncedAt: values[9] as Value<DateTime?>,
+    remoteRevision: values[10] as Value<String?>,
+    workoutHistoryId: Value(result.workoutHistoryId),
+    programSnapshotId: Value(result.programSnapshotId),
+    exerciseSnapshotId: Value(result.exerciseSnapshotId),
+    programIndex: Value(result.programIndex),
+    exerciseIndex: Value(result.exerciseIndex),
+    setIndex: Value(result.setIndex),
+    programNameSnapshot: Value(result.programNameSnapshot),
+    exerciseNameSnapshot: Value(result.exerciseNameSnapshot),
+    timeEnabledSnapshot: Value(result.timeEnabledSnapshot),
+    repsEnabledSnapshot: Value(result.repsEnabledSnapshot),
+    scoreEnabledSnapshot: Value(result.scoreEnabledSnapshot),
+    targetTimeSecondsSnapshot: Value(result.targetTimeSecondsSnapshot),
+    targetRepsSnapshot: Value(result.targetRepsSnapshot),
+    targetScoreSnapshot: Value(result.targetScoreSnapshot),
+    actualTimeMs: Value(result.actualTimeMs),
+    actualReps: Value(result.actualReps),
+    actualScore: Value(result.actualScore),
+    scoreLabelSnapshot: Value(result.scoreLabelSnapshot),
+    scoreUnitSnapshot: Value(result.scoreUnitSnapshot),
+    startedAt: Value(result.startedAt),
+    completedAt: Value(result.completedAt),
+  );
+}
+
+String _syncStateToDb(domain.SyncState state) => switch (state) {
+  domain.SyncState.localOnly => 'localOnly',
+  domain.SyncState.dirty => 'dirty',
+  domain.SyncState.synced => 'synced',
+  domain.SyncState.deleted => 'deleted',
+};
+
+domain.SyncState _syncStateFromDb(String value) => switch (value) {
+  'localOnly' => domain.SyncState.localOnly,
+  'dirty' => domain.SyncState.dirty,
+  'synced' => domain.SyncState.synced,
+  'deleted' => domain.SyncState.deleted,
+  _ => throw domain.DomainException('Unknown sync state: $value'),
+};
+
+String _activeStatusToDb(domain.ActiveWorkoutStatus status) => switch (status) {
+  domain.ActiveWorkoutStatus.running => 'running',
+  domain.ActiveWorkoutStatus.paused => 'paused',
+  domain.ActiveWorkoutStatus.savedExit => 'savedExit',
+  domain.ActiveWorkoutStatus.completed => 'completed',
+  domain.ActiveWorkoutStatus.abandoned => 'abandoned',
+};
+
+domain.ActiveWorkoutStatus _activeStatusFromDb(String value) => switch (value) {
+  'running' => domain.ActiveWorkoutStatus.running,
+  'paused' => domain.ActiveWorkoutStatus.paused,
+  'savedExit' => domain.ActiveWorkoutStatus.savedExit,
+  'completed' => domain.ActiveWorkoutStatus.completed,
+  'abandoned' => domain.ActiveWorkoutStatus.abandoned,
+  _ => throw domain.DomainException('Unknown active workout status: $value'),
+};
diff --git a/lib/infrastructure/local/local.dart b/lib/infrastructure/local/local.dart
index c44744f..54d2676 100644
--- a/lib/infrastructure/local/local.dart
+++ b/lib/infrastructure/local/local.dart
@@ -1,2 +1,3 @@
 export 'app_database.dart';
+export 'drift_repositories.dart';
 export 'local_id.dart';
diff --git a/lib/infrastructure/local/local_id.dart b/lib/infrastructure/local/local_id.dart
index 3d5702b..26242d7 100644
--- a/lib/infrastructure/local/local_id.dart
+++ b/lib/infrastructure/local/local_id.dart
@@ -1,12 +1,17 @@
 import 'dart:math';
 
+import '../../application/ports.dart';
+
 const _crockfordBase32 = '0123456789ABCDEFGHJKMNPQRSTVWXYZ';
 
-final class LocalIdGenerator {
+final class LocalIdGenerator implements IdGenerator {
   LocalIdGenerator({Random? random}) : _random = random ?? Random.secure();
 
   final Random _random;
 
+  @override
+  String newId() => newUlid();
+
   String newUlid({DateTime? now}) {
     final timestamp = (now ?? DateTime.now().toUtc()).millisecondsSinceEpoch;
     final buffer = StringBuffer();
diff --git a/test/application/use_cases_test.dart b/test/application/use_cases_test.dart
new file mode 100644
index 0000000..603764b
--- /dev/null
+++ b/test/application/use_cases_test.dart
@@ -0,0 +1,117 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:gametime/application/application.dart';
+import 'package:gametime/domain/domain.dart';
+
+void main() {
+  test('Exercise requires at least one active measure', () {
+    expect(
+      () => Exercise(
+        metadata: _metadata('exercise-1'),
+        name: 'Push up',
+        hasTimeMeasure: false,
+        hasRepsMeasure: false,
+        hasScoreMeasure: false,
+      ),
+      throwsA(isA<DomainException>()),
+    );
+  });
+
+  test('Workout template use case rejects active measure overrides', () async {
+    final useCase = WorkoutTemplateUseCases(
+      templateRepository: _FakeWorkoutTemplateRepository(),
+      programRepository: _FakeProgramRepository(),
+      clock: _FakeClock(DateTime.utc(2026, 7, 17, 12)),
+      ids: _FakeIds(),
+      originDeviceId: 'device-1',
+    );
+
+    await expectLater(
+      useCase.overrideExerciseTargets(
+        workoutTemplateProgramId: 'template-program-1',
+        snapshotProgramExerciseId: 'exercise-snapshot-1',
+        attemptedMeasureOverride: {WorkoutMeasure.reps},
+      ),
+      throwsA(isA<DomainException>()),
+    );
+  });
+
+  test('Active session elapsed time is based on persisted timestamps', () {
+    final clock = _FakeClock(DateTime.utc(2026, 7, 17, 12));
+    final session = ActiveWorkoutSession(
+      metadata: _metadata('session-1'),
+      status: ActiveWorkoutStatus.running,
+      startedAt: clock.now(),
+      lastPersistedAt: clock.now(),
+      elapsedActiveMs: 0,
+      currentProgramIndex: 0,
+      currentExerciseIndex: 0,
+      currentSetIndex: 0,
+      resolvedTemplateSnapshotJson: '{}',
+    );
+
+    clock.value = clock.value.add(const Duration(seconds: 30));
+    final paused = session.pause(clock.now());
+    expect(paused.elapsedActiveMs, 30000);
+
+    clock.value = clock.value.add(const Duration(minutes: 5));
+    final resumed = paused.resume(clock.now());
+    expect(resumed.elapsedActiveMillisecondsAt(clock.now()), 30000);
+
+    clock.value = clock.value.add(const Duration(seconds: 15));
+    expect(resumed.elapsedActiveMillisecondsAt(clock.now()), 45000);
+  });
+}
+
+EntityMetadata _metadata(String id) {
+  return EntityMetadata(
+    id: id,
+    createdAt: DateTime.utc(2026, 7, 17),
+    updatedAt: DateTime.utc(2026, 7, 17),
+    originDeviceId: 'device-1',
+  );
+}
+
+final class _FakeClock implements Clock {
+  _FakeClock(this.value);
+
+  DateTime value;
+
+  @override
+  DateTime now() => value;
+}
+
+final class _FakeIds implements IdGenerator {
+  var _next = 0;
+
+  @override
+  String newId() {
+    _next += 1;
+    return 'id-$_next';
+  }
+}
+
+final class _FakeWorkoutTemplateRepository
+    implements WorkoutTemplateRepository {
+  @override
+  Future<WorkoutTemplate?> findById(String id) async => null;
+
+  @override
+  Future<void> save(WorkoutTemplate template) async {}
+
+  @override
+  Future<void> saveOverride(WorkoutTemplateExerciseOverride override) async {}
+
+  @override
+  Future<void> saveProgram(WorkoutTemplateProgram program) async {}
+}
+
+final class _FakeProgramRepository implements ProgramRepository {
+  @override
+  Future<Program?> findById(String id) async => null;
+
+  @override
+  Future<void> save(Program program) async {}
+
+  @override
+  Future<void> saveExercise(ProgramExercise exercise) async {}
+}