fix: 修正学习流程中的证据、复习与进度问题

- 独立尝试按课程要求校验内容，不再任意输入即算独立成功
- 复习节点改为学后第 1/3/7/14 天，之后每 30 天抽查；复习轮换情境
- 掌握状态按作答记录推导：需认识、可回忆、跨情境使用及最近两次无帮助
- 课程证据按实际用到的目标记录；跟读与课程对话只算辅助练习
- 复习成功不再降低已有状态
- 学完课程后进入下一节未完成课程；全部学完后引导巩固与阶段评估
- 新增 3 题基础定位，按结果设置起始课程
- 新增按课程开放的对话场景，首页推荐最少练习的场景
- 切换课程时清空上一课的步骤进度
- AI 返回 JSON 格式并按 JSON 回放历史；拼写校验忽略大小写与连字符；移除学习目标选择

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

kouyu_english/lib/core/ai_service.dart

@@ -382,12 +382,19 @@ class AiService {
     // with a small token cap, so reasoning only adds cost and can exhaust the
     // cap before the JSON is written. Other providers may reject these
     // DeepSeek-specific switches, so they keep the original payload.
+    //
+    // Every prompt asks for JSON, but without JSON Output DeepSeek copies the
+    // plain-text assistant turns in a dialogue history and answers in plain
+    // text about half the time, which the app then treats as a failed call.
     if (_isDeepSeek(uri)) {
       return isResponses
           ? {
               'model': model,
               'input': messages,
               'reasoning': {'effort': 'none'},
+              'text': {
+                'format': {'type': 'json_object'},
+              },
               'temperature': ?temperature,
               'max_output_tokens': ?maxTokens,
             }
@@ -395,6 +402,7 @@ class AiService {
               'model': model,
               'messages': messages,
               'thinking': {'type': 'disabled'},
+              'response_format': {'type': 'json_object'},
               'temperature': ?temperature,
               'max_tokens': ?maxTokens,
             };
@@ -787,7 +795,18 @@ class AiService {
       endpoint: endpoint,
       model: model,
       system: system,
-      messages: history,
+      // Earlier AI lines are stored as plain English. Sent that way they teach
+      // the model to answer in plain text (or, in JSON mode, with blanks), so
+      // they are replayed in the JSON shape the system prompt asks for.
+      messages: [
+        for (final message in history)
+          message['role'] == 'assistant'
+              ? {
+                  'role': 'assistant',
+                  'content': jsonEncode({'reply': message['content']}),
+                }
+              : message,
+      ],
       temperature: 0.3,
       maxTokens: 300,
     );

kouyu_english/lib/core/app_state.dart

@@ -9,6 +9,7 @@ import 'models.dart';
 import 'a0_core.dart';
 import 'generated_content.dart';
 import 'local_store.dart';
+import 'review_feedback.dart';
 import 'seed_courses.dart';
 import 'ai_config.dart';
 import 'ai_service.dart';
@@ -32,6 +33,10 @@ abstract class _AppStateData extends ChangeNotifier {
   bool keepRecordings = false;
   int completedLessons = 0;
   String activeLessonId = 'a0-01';
+
+  /// Lesson recommended by the placement check; it and earlier lessons are
+  /// open without finishing the lesson before them.
+  String placementStartLessonId = 'a0-01';
   final Set<String> completedLessonIds = {};
   final Set<String> completedSegmentIds = {};
   final Set<String> reportedAiVariantKeys = {};
@@ -212,6 +217,16 @@ class AppState extends _AppStateData
     notifyListeners();
   }
 
+  /// Applies the placement result. Only A0 starting points exist until A1
+  /// content is frozen, and placement never counts as passing a lesson.
+  void setPlacementStartLesson(String lessonId) {
+    if (!a0SeedLessons.any((lesson) => lesson.id == lessonId)) return;
+    placementStartLessonId = lessonId;
+    activeLessonId = lessonId;
+    _resetLessonFlow();
+    notifyListeners();
+  }
+
   void setAiProvider(AiProviderType value) {
     aiProvider = value;
     notifyListeners();
@@ -236,6 +251,7 @@ class AppState extends _AppStateData
   void clearProgress() {
     completedLessons = 0;
     activeLessonId = 'a0-01';
+    placementStartLessonId = 'a0-01';
     completedLessonIds.clear();
     completedSegmentIds.clear();
     reportedAiVariantKeys.clear();

kouyu_english/lib/core/app_state_assessment.dart

@@ -23,10 +23,22 @@ mixin _AssessmentProgress on _AppStateData, _ReviewAndMastery {
         );
   }
 
-  bool get a0Passed =>
-      coreUsableCount >= 48 &&
-      coreMasteredCount >= 30 &&
-      hasTwoValidAssessmentPasses;
+  /// Enough core items are usable and mastered to sit the stage assessment.
+  bool get a0AssessmentReady =>
+      coreUsableCount >= 48 && coreMasteredCount >= 30;
+
+  bool get a0Passed => a0AssessmentReady && hasTwoValidAssessmentPasses;
+
+  /// The first assessment pack the learner can start and has not passed yet.
+  String? get nextAssessmentPackId {
+    for (final packId in const ['A0-E1', 'A0-E2']) {
+      final passed = assessments.any(
+        (record) => record.packId == packId && record.passed,
+      );
+      if (!passed && canStartAssessmentPack(packId)) return packId;
+    }
+    return null;
+  }
 
   bool canStartAssessmentPack(String packId) {
     if (packId != 'A0-E2') return true;

kouyu_english/lib/core/app_state_lesson.dart

@@ -82,14 +82,29 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     notifyListeners();
   }
 
+  int _lessonIndex(String id) =>
+      a0SeedLessons.indexWhere((lesson) => lesson.id == id);
+
   bool isLessonUnlocked(String id) {
-    final index = a0SeedLessons.indexWhere((lesson) => lesson.id == id);
+    final index = _lessonIndex(id);
+    if (index < 0) return false;
+    // The placement start and everything before it are open, so a learner
+    // placed further ahead can still go back to easier lessons.
     return index == 0 ||
-        (index > 0 && completedLessonIds.contains(a0SeedLessons[index - 1].id));
+        index <= _lessonIndex(placementStartLessonId) ||
+        completedLessonIds.contains(a0SeedLessons[index - 1].id);
   }
 
+  bool get allLessonsComplete =>
+      a0SeedLessons.every((lesson) => completedLessonIds.contains(lesson.id));
+
   void openLesson(String id) {
     if (!isLessonUnlocked(id)) return;
+    if (id != activeLessonId) {
+      // Step flags belong to the lesson they were earned in; carrying them
+      // over would let another lesson finish without its own tasks.
+      _resetLessonFlow();
+    }
     activeLessonId = id;
     lessonStep = LessonStep.preview;
     previewIndex = 0;
@@ -104,24 +119,34 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     notifyListeners();
   }
 
-  void completeListening() {
+  /// [recognized] is true when the learner picked the right meaning on the
+  /// first try, which is recognition evidence for the segment's targets.
+  void completeListening({bool recognized = false}) {
     _introduceLessonTargets();
+    if (recognized && !lessonListeningComplete) {
+      _recordLessonTaskEvidence(
+        targetIds: _activeTargetItemIds,
+        taskSuffix: 'listening-check',
+        skill: '听辨识别',
+        outcome: EvidenceKind.independentSuccess,
+      );
+    }
     lessonListeningComplete = true;
     lessonStep = LessonStep.speaking;
     notifyListeners();
   }
 
-  void completeSpeaking({bool assisted = false}) {
+  /// Follow-reading repeats a model sentence, so it is always assisted
+  /// practice and never independent speaking evidence.
+  void completeSpeaking() {
     lessonSpeakingComplete = true;
     lessonStep = LessonStep.reading;
     _recordLessonTaskEvidence(
-      targetIds: [_primaryTargetId],
+      targetIds: _activeTargetItemIds,
       taskSuffix: 'speaking',
       skill: '口语表达',
-      outcome: assisted
-          ? EvidenceKind.assisted
-          : EvidenceKind.independentSuccess,
-      assisted: assisted,
+      outcome: EvidenceKind.assisted,
+      assisted: true,
     );
     notifyListeners();
   }
@@ -130,7 +155,7 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     lessonReadingComplete = true;
     lessonStep = LessonStep.writing;
     _recordLessonTaskEvidence(
-      targetIds: [_primaryTargetId],
+      targetIds: _activeTargetItemIds,
       taskSuffix: 'reading',
       skill: '阅读理解',
       outcome: EvidenceKind.exposure,
@@ -143,7 +168,7 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     lessonWritingDraft = '';
     lessonStep = LessonStep.dialogue;
     _recordLessonTaskEvidence(
-      targetIds: [_primaryTargetId],
+      targetIds: _answerTargets(assisted: assisted, rawAnswer: rawAnswer),
       taskSuffix: 'writing',
       skill: '写作表达',
       outcome: assisted
@@ -159,7 +184,7 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     lessonDialogueComplete = true;
     lessonStep = LessonStep.independent;
     _recordLessonTaskEvidence(
-      targetIds: [_primaryTargetId],
+      targetIds: _activeTargetItemIds,
       taskSuffix: 'dialogue',
       skill: '受控对话',
       outcome: EvidenceKind.assisted,
@@ -180,7 +205,7 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     independentAttemptSpoken = spoken && !assisted;
     lessonStep = LessonStep.complete;
     _recordLessonTaskEvidence(
-      targetIds: [_primaryTargetId],
+      targetIds: _answerTargets(assisted: assisted, rawAnswer: rawAnswer),
       taskSuffix: 'independent',
       skill: spoken && !assisted ? '口语表达' : '写作表达',
       inputMode: spoken && !assisted ? 'speech-unedited-transcript' : 'text',
@@ -198,12 +223,8 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     if (!lessonCanComplete) return;
     completedLessonIds.add(activeLessonId);
     completedLessons = completedLessonIds.length;
-    final currentIndex = a0SeedLessons.indexWhere(
-      (lesson) => lesson.id == activeLessonId,
-    );
-    if (currentIndex >= 0 && currentIndex < a0SeedLessons.length - 1) {
-      activeLessonId = a0SeedLessons[currentIndex + 1].id;
-    }
+    final next = _nextIncompleteLessonId();
+    if (next != null) activeLessonId = next;
     _resetLessonFlow();
     notifyListeners();
     _syncInBackground();
@@ -276,6 +297,22 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     return changed;
   }
 
+  /// The first unfinished lesson from the placement start onward, falling back
+  /// to any earlier unfinished lesson. Null once every lesson is finished.
+  String? _nextIncompleteLessonId() {
+    final start = _lessonIndex(
+      placementStartLessonId,
+    ).clamp(0, a0SeedLessons.length);
+    final ordered = [
+      ...a0SeedLessons.skip(start),
+      ...a0SeedLessons.take(start),
+    ];
+    return ordered
+        .where((lesson) => !completedLessonIds.contains(lesson.id))
+        .firstOrNull
+        ?.id;
+  }
+
   void _resetLessonFlow() {
     lessonStep = LessonStep.preview;
     previewIndex = 0;
@@ -305,31 +342,78 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     _syncInBackground();
   }
 
+  /// Records one dialogue turn.
+  ///
+  /// A lesson dialogue follows a model, so its turns stay assisted or pending.
+  /// A free scene ([sceneId] set) is use outside the lesson: every taught core
+  /// item the learner actually used counts as context use.
   void recordDialogueAttempt({
     required String taskId,
     required String rawAnswer,
     required bool assisted,
     bool spoken = false,
     String? recordingPath,
+    String? sceneId,
   }) {
     final now = DateTime.now();
+    final inScene = sceneId != null;
+    final itemIds = inScene
+        ? [
+            for (final id in a0CoreItems.keys)
+              if (mastery[id]?.firstTaughtAt != null &&
+                  coreItemUsedIn(id, rawAnswer))
+                id,
+          ]
+        : [
+            for (final id in _activeTargetItemIds)
+              if (coreItemUsedIn(id, rawAnswer)) id,
+          ];
+    if (itemIds.isEmpty && !inScene) itemIds.add(_primaryTargetId);
+    final outcome = assisted
+        ? EvidenceKind.assisted
+        : (inScene ? EvidenceKind.independentSuccess : EvidenceKind.pending);
+    for (var index = 0; index < itemIds.length; index++) {
+      final id = itemIds[index];
       attemptEvidence.add(
         AttemptEvidence(
-        id: 'dialogue-$taskId-${now.microsecondsSinceEpoch}',
-        itemId: _primaryTargetId,
+          id: 'dialogue-$taskId-$id-${now.microsecondsSinceEpoch}-$index',
+          itemId: id,
           taskId: taskId,
-        skill: '受控对话',
+          skill: inScene ? '情境使用' : '受控对话',
           inputMode: spoken ? 'speech-unedited-transcript' : 'text',
-        outcome: assisted ? EvidenceKind.assisted : EvidenceKind.pending,
+          outcome: outcome,
           createdAt: now,
           rawAnswer: rawAnswer,
           recordingPath: recordingPath,
           assisted: assisted,
         ),
       );
+      if (outcome != EvidenceKind.pending) _recordEvidence(id, outcome);
+    }
     notifyListeners();
   }
 
+  /// A scene the learner has the language for.
+  bool isSceneUnlocked(DialogueScene scene) =>
+      scene.unlockAfterLessonId == null ||
+      completedLessonIds.contains(scene.unlockAfterLessonId);
+
+  /// The open scene practised least recently, judged by its pending recaps.
+  DialogueScene get recommendedScene {
+    final open = a0Scenes.where(isSceneUnlocked).toList();
+    int recaps(DialogueScene scene) => reviewQueue
+        .where((item) => item.id.startsWith('dialogue-${scene.id}-'))
+        .length;
+    open.sort((left, right) {
+      final byRecaps = recaps(left).compareTo(recaps(right));
+      // Prefer the newest scene when both have been practised equally.
+      return byRecaps != 0
+          ? byRecaps
+          : a0Scenes.indexOf(right).compareTo(a0Scenes.indexOf(left));
+    });
+    return open.first;
+  }
+
   List<String> get _activeTargetItemIds {
     final lesson = lessonById(activeLessonId);
     return lesson.segments[activeSegmentIndexFor(activeLessonId)].targetItemIds;
@@ -337,6 +421,17 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
 
   String get _primaryTargetId => _activeTargetItemIds.lastOrNull ?? 'A0-P02';
 
+  /// An assisted answer is assisted practice for every target; an unaided one
+  /// only proves the targets it actually uses.
+  List<String> _answerTargets({required bool assisted, String? rawAnswer}) {
+    if (assisted) return _activeTargetItemIds;
+    final answer = rawAnswer ?? '';
+    return [
+      for (final id in _activeTargetItemIds)
+        if (coreItemUsedIn(id, answer)) id,
+    ];
+  }
+
   /// Records one evidence row for every target actually attached to a local
   /// task.  A task can be displayed once but must never silently award its
   /// result to unrelated core items.
@@ -353,7 +448,6 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
     final now = DateTime.now();
     for (var index = 0; index < targetIds.length; index++) {
       final id = targetIds[index];
-      _recordEvidence(id, outcome);
       attemptEvidence.add(
         AttemptEvidence(
           id: 'lesson-$_activeSegmentId-$taskSuffix-$id-${now.microsecondsSinceEpoch}-$index',
@@ -368,6 +462,8 @@ mixin _LessonProgress on _AppStateData, _ReviewAndMastery {
           assisted: assisted,
         ),
       );
+      // The row goes in first: status is derived from the attempt history.
+      _recordEvidence(id, outcome);
     }
   }
 

kouyu_english/lib/core/app_state_review.dart

@@ -102,7 +102,10 @@ mixin _ReviewAndMastery on _AppStateData {
     final nextSuccesses = canProgress
         ? current.successfulReviews + 1
         : current.successfulReviews;
-    const intervals = [1, 2, 4];
+    // Checkpoints fall on days 1, 3, 7 and 14 after first teaching: the first
+    // review is due one day after teaching, then 2, 4 and 7 days apart, and
+    // every 30 days once all four checkpoints are passed.
+    const intervals = [2, 4, 7];
     final intervalIndex = (nextSuccesses - 1)
         .clamp(0, intervals.length - 1)
         .toInt();
@@ -115,17 +118,23 @@ mixin _ReviewAndMastery on _AppStateData {
         : nextSuccesses >= 4
         ? 30
         : intervals[intervalIndex];
+    // The next check of a core item uses a different reviewed situation, so
+    // later successes also show the item works outside the lesson's context.
+    // An AI variant keeps its index so it can still be reported afterwards.
+    final nextTemplate =
+        a0CoreItems.containsKey(current.id) && !current.isAiGenerated
+        ? coreReviewVariant(current.id, current.variantIndex + 1)
+        : null;
     reviewQueue[index] = current.copyWith(
       dueAt: DateTime.now().add(Duration(days: days)),
       attempts: current.attempts + 1,
       successfulReviews: nextSuccesses,
       lastProgressedAt: canProgress ? now : current.lastProgressedAt,
+      prompt: nextTemplate?.prompt,
+      hint: nextTemplate?.hint,
+      skill: nextTemplate?.skill,
+      variantIndex: nextTemplate == null ? null : current.variantIndex + 1,
     );
-    if (assisted) {
-      _recordEvidence(current.id, EvidenceKind.assisted);
-    } else {
-      _recordReviewSuccess(current.id, nextSuccesses);
-    }
     _addAttemptEvidence(
       current,
       outcome: assisted
@@ -134,6 +143,11 @@ mixin _ReviewAndMastery on _AppStateData {
       assisted: assisted,
       rawAnswer: rawAnswer,
     );
+    if (assisted) {
+      _recordEvidence(current.id, EvidenceKind.assisted);
+    } else {
+      _recordReviewSuccess(current.id, nextSuccesses);
+    }
     notifyListeners();
     _syncInBackground();
   }
@@ -156,8 +170,9 @@ mixin _ReviewAndMastery on _AppStateData {
         ? (existing.checkpoint - 1).clamp(0, 4).toInt()
         : existing.checkpoint;
     mastery[item.id] = existing.copyWith(
-      status: secondFailure
-          ? _statusForCheckpoint(nextCheckpoint)
+      // Mastery needs all four checkpoints; losing one caps the item at use.
+      status: secondFailure && nextCheckpoint < 4
+          ? _lowerStatus(existing.status, MasteryStatus.use)
           : existing.status,
       checkpoint: nextCheckpoint,
       needsReview: true,
@@ -227,17 +242,17 @@ mixin _ReviewAndMastery on _AppStateData {
 
   /// Adds one low-priority, non-core recap based on a completed independent
   /// dialogue. It is deliberately separate from A0 denominator items.
-  void addDialogueRecap(String sentence) {
+  void addDialogueRecap(String sentence, {String sceneId = 'a0-meet'}) {
     final now = DateTime.now();
     final day =
         '${now.year}${now.month.toString().padLeft(2, '0')}${now.day.toString().padLeft(2, '0')}';
-    final id = 'dialogue-a0-meet-$day';
+    final id = 'dialogue-$sceneId-$day';
     if (reviewQueue.any((item) => item.id == id)) return;
     reviewQueue.add(
       ReviewItem(
         id: id,
         target: sentence,
-        prompt: '再用英语介绍一次自己。',
+        prompt: sceneById(sceneId).recapPrompt,
         hint: '试着不用提示，说出你刚才表达的内容。',
         dueAt: now.add(const Duration(days: 1)),
         skill: '情境复练',
@@ -374,7 +389,6 @@ mixin _ReviewAndMastery on _AppStateData {
       ..sort((left, right) => left.createdAt.compareTo(right.createdAt));
     var checkpoint = 0;
     var needsReview = forceReview;
-    var nonReviewSuccesses = 0;
     DateTime? firstTaughtAt;
     final progressedDays = <String>{};
     for (final event in events) {
@@ -384,10 +398,6 @@ mixin _ReviewAndMastery on _AppStateData {
           (firstTaughtAt == null || event.createdAt.isBefore(firstTaughtAt))) {
         firstTaughtAt = event.createdAt;
       }
-      if (!isReview && event.outcome == EvidenceKind.independentSuccess) {
-        nonReviewSuccesses++;
-        continue;
-      }
       if (!isReview) continue;
       if (event.outcome == EvidenceKind.independentSuccess) {
         final day =
@@ -399,12 +409,10 @@ mixin _ReviewAndMastery on _AppStateData {
         needsReview = true;
       }
     }
-    final independentLevel = nonReviewSuccesses.clamp(0, 3);
-    final level = checkpoint > independentLevel ? checkpoint : independentLevel;
     mastery[id] = MasteryItem(
       id: id,
       label: existing?.label ?? a0CoreItems[id] ?? id,
-      status: _statusForCheckpoint(level),
+      status: _statusFromEvidence(id, checkpoint),
       checkpoint: checkpoint,
       needsReview: needsReview,
       evidence: events.map((event) => event.outcome).toList(),
@@ -417,22 +425,17 @@ mixin _ReviewAndMastery on _AppStateData {
         mastery[id] ??
         MasteryItem(
           id: id,
-          label: id,
+          label: a0CoreItems[id] ?? id,
           status: MasteryStatus.newItem,
           evidence: const [],
         );
-    final allEvidence = [...existing.evidence, evidence];
-    MasteryStatus next = existing.status;
-    if (evidence == EvidenceKind.independentSuccess) {
-      next = switch (existing.status) {
-        MasteryStatus.newItem => MasteryStatus.recognize,
-        MasteryStatus.recognize => MasteryStatus.recall,
-        MasteryStatus.recall => MasteryStatus.use,
-        MasteryStatus.use || MasteryStatus.master => existing.status,
-        MasteryStatus.needsReview => MasteryStatus.recall,
-      };
-    }
-    mastery[id] = existing.copyWith(status: next, evidence: allEvidence);
+    mastery[id] = existing.copyWith(
+      status: _higherStatus(
+        existing.status,
+        _statusFromEvidence(id, existing.checkpoint),
+      ),
+      evidence: [...existing.evidence, evidence],
+    );
   }
 
   void _recordReviewSuccess(String id, int successes) {
@@ -445,19 +448,93 @@ mixin _ReviewAndMastery on _AppStateData {
           evidence: const [],
         );
     final checkpoint = successes.clamp(0, 4).toInt();
+    // A success never lowers what earlier evidence already showed.
     mastery[id] = existing.copyWith(
-      status: _statusForCheckpoint(checkpoint),
+      status: _higherStatus(
+        existing.status,
+        _statusFromEvidence(id, checkpoint),
+      ),
       checkpoint: checkpoint,
       needsReview: false,
       evidence: [...existing.evidence, EvidenceKind.independentSuccess],
     );
   }
 
-  MasteryStatus _statusForCheckpoint(int checkpoint) => switch (checkpoint) {
-    0 => MasteryStatus.newItem,
-    1 => MasteryStatus.recognize,
-    2 => MasteryStatus.recall,
-    3 => MasteryStatus.use,
-    _ => MasteryStatus.master,
+  /// Skills whose success only shows the learner recognises the item.
+  static const _recognitionSkills = {'听辨识别', '阅读识别', '听力理解', '阅读理解'};
+
+  /// Controlled lesson steps (follow-reading, scripted dialogue) are practice,
+  /// not attempts to recall, so they never count as a valid answer.
+  static bool _isControlledPractice(AttemptEvidence entry) =>
+      entry.taskId.startsWith('lesson-') &&
+      (entry.taskId.endsWith('-speaking') ||
+          entry.taskId.endsWith('-dialogue'));
+
+  /// Use outside the lesson it was taught in: a free scene dialogue, an AI
+  /// adaptive task, or a review answered in a changed situation.
+  static bool _isContextUse(AttemptEvidence entry) =>
+      entry.taskId.startsWith('dialogue-scene-') ||
+      entry.id.startsWith('adaptive-') ||
+      (entry.taskId == 'review-${entry.itemId}' && entry.variantIndex >= 1);
+
+  /// Learning engine 3.1: recognise = a recognition success; recall = an
+  /// unaided spoken or written success; use = unaided use in a different
+  /// situation; master = four checkpoints, all three kinds of evidence, and
+  /// the latest two valid answers both unaided.
+  MasteryStatus _statusFromEvidence(String id, int checkpoint) {
+    var recognized = false;
+    var recalled = false;
+    var usedInContext = false;
+    final validAnswers = <EvidenceKind>[];
+    final events = attemptEvidence.where((entry) => entry.itemId == id).toList()
+      ..sort((left, right) => left.createdAt.compareTo(right.createdAt));
+    for (final event in events) {
+      final recognition = _recognitionSkills.contains(event.skill);
+      if (event.outcome == EvidenceKind.independentSuccess) {
+        if (recognition) {
+          recognized = true;
+        } else {
+          recalled = true;
+          if (_isContextUse(event)) usedInContext = true;
+        }
+      }
+      if (!recognition &&
+          !_isControlledPractice(event) &&
+          (event.outcome == EvidenceKind.independentSuccess ||
+              event.outcome == EvidenceKind.assisted ||
+              event.outcome == EvidenceKind.languageError)) {
+        validAnswers.add(event.outcome);
+      }
+    }
+    final latestTwoUnaided =
+        validAnswers.length >= 2 &&
+        validAnswers
+            .skip(validAnswers.length - 2)
+            .every((outcome) => outcome == EvidenceKind.independentSuccess);
+    if (checkpoint >= 4 &&
+        recognized &&
+        recalled &&
+        usedInContext &&
+        latestTwoUnaided) {
+      return MasteryStatus.master;
+    }
+    if (recalled && usedInContext) return MasteryStatus.use;
+    if (recalled) return MasteryStatus.recall;
+    if (recognized) return MasteryStatus.recognize;
+    return MasteryStatus.newItem;
+  }
+
+  static int _statusRank(MasteryStatus status) => switch (status) {
+    MasteryStatus.newItem => 0,
+    MasteryStatus.recognize => 1,
+    MasteryStatus.recall || MasteryStatus.needsReview => 2,
+    MasteryStatus.use => 3,
+    MasteryStatus.master => 4,
   };
+
+  static MasteryStatus _higherStatus(MasteryStatus a, MasteryStatus b) =>
+      _statusRank(b) > _statusRank(a) ? b : a;
+
+  static MasteryStatus _lowerStatus(MasteryStatus a, MasteryStatus b) =>
+      _statusRank(b) < _statusRank(a) ? b : a;
 }

kouyu_english/lib/core/app_state_snapshot.dart

@@ -107,6 +107,8 @@ extension _AppStateSnapshot on AppState {
     previewIndex = data['previewIndex'] as int? ?? previewIndex;
     completedLessons = data['completedLessons'] as int? ?? completedLessons;
     activeLessonId = data['activeLessonId'] as String? ?? activeLessonId;
+    placementStartLessonId =
+        data['placementStartLessonId'] as String? ?? placementStartLessonId;
     completedLessonIds
       ..clear()
       ..addAll(
@@ -327,6 +329,7 @@ extension _AppStateSnapshot on AppState {
     'previewIndex': previewIndex,
     'completedLessons': completedLessons,
     'activeLessonId': activeLessonId,
+    'placementStartLessonId': placementStartLessonId,
     'completedLessonIds': completedLessonIds.toList(),
     'completedSegmentIds': completedSegmentIds.toList(),
     'reportedAiVariantKeys': reportedAiVariantKeys.toList(),

kouyu_english/lib/core/local_store.dart

@@ -429,6 +429,7 @@ class LocalSnapshotStore {
           'previewIndex',
           'completedLessons',
           'activeLessonId',
+          'placementStartLessonId',
           'completedLessonIds',
           'completedSegmentIds',
           'activeSegmentIndexes',

kouyu_english/lib/core/review_feedback.dart

@@ -1,3 +1,4 @@
+import 'a0_core.dart';
 import 'models.dart';
 
 class ReviewCheckResult {
@@ -21,70 +22,20 @@ class ReviewFeedback {
       .trim();
 
   static ReviewCheckResult check(ReviewItem item, String input) {
-    final text = _normalize(input);
-    final tokens = RegExp(
-      r"[a-z]+(?:'[a-z]+)?",
-    ).allMatches(text).map((match) => match.group(0)!).toSet();
-    bool has(String token) => tokens.contains(_normalize(token));
-    bool phrase(String value) => text.contains(_normalize(value));
-    bool hasAny(Iterable<String> values) => values.any(has);
-    final introduction =
-        phrase("i'm") || phrase('i am') || phrase('my name is');
-    final itIs = phrase("it's") || phrase('it is');
-    final numberWords = RegExp(
-      r'\b(zero|one|two|three|four|five|six|seven|eight|nine|ten)\b',
-    ).allMatches(text).length;
-
-    final complete = switch (item.id) {
-      'A0-P01' => introduction && tokens.length >= 2,
-      'A0-P02' => (phrase("what's your name") || phrase('what is your name')),
-      'A0-P03' => phrase('nice to meet you'),
-      'A0-P04' => phrase('how do you spell'),
-      'A0-P05' => phrase('how are you'),
-      'A0-P06' => introduction && hasAny(['good', 'okay', 'tired']),
-      'A0-P07' =>
-        phrase("what's your phone number") ||
-            phrase('what is your phone number'),
-      'A0-P08' =>
-        (phrase('my number is') || numberWords >= 3) && numberWords >= 3,
-      'A0-P09' => phrase("what's this") || phrase('what is this'),
-      'A0-P10' => itIs && hasAny(['book', 'pen', 'bag', 'key']),
-      'A0-P11' => phrase('where are you from'),
-      'A0-P12' => introduction && has('from') && tokens.length >= 3,
-      'A0-P13' => phrase('this is my') && tokens.length >= 4,
-      'A0-P14' => phrase('what day is it'),
-      'A0-P15' =>
-        itIs &&
-            hasAny([
-              'monday',
-              'tuesday',
-              'wednesday',
-              'thursday',
-              'friday',
-              'saturday',
-              'sunday',
-            ]),
-      'A0-P16' => phrase('what time is it'),
-      'A0-P17' =>
-        itIs &&
-            (has('clock') ||
-                has("o'clock") ||
-                has('oclock') ||
-                phrase("o'clock")),
-      'A0-P18' => introduction && has('like') && tokens.length >= 3,
-      'A0-P19' => phrase('do you like'),
-      'A0-P20' =>
-        phrase('please say that again') || phrase('please speak slowly'),
-      _ when item.id.startsWith('A0-W') =>
-        tokens.contains(_normalize(item.target)) || phrase(item.target),
-      _ => tokens.length >= 2,
-    };
+    final complete = a0CoreItems.containsKey(item.id)
+        // A word review checks the word it actually shows.
+        ? coreItemUsedIn(item.id, input, word: item.target)
+        : _tokens(_normalize(input)).length >= 2;
     return ReviewCheckResult(
       complete: complete,
       message: complete ? '表达已完成，可以进入下一次复习安排。' : _hint(item.id),
     );
   }
 
+  static Set<String> _tokens(String text) => RegExp(
+    r"[a-z]+(?:'[a-z]+)?",
+  ).allMatches(text).map((match) => match.group(0)!).toSet();
+
   static String _hint(String id) => switch (id) {
     'A0-P01' => '用 I’m / I am 或 My name is 介绍一个名字。',
     'A0-P02' => '试着问：What’s your name?',
@@ -97,3 +48,66 @@ class ReviewFeedback {
     _ => '再补充本次目标中的关键英文词或句型。',
   };
 }
+
+/// Whether [input] actually contains A0 core item [id]. Lessons, reviews and
+/// dialogues use the same rule, so evidence only goes to the items a learner
+/// really produced, never to every target a task happens to be attached to.
+bool coreItemUsedIn(String id, String input, {String? word}) {
+  final text = ReviewFeedback._normalize(input);
+  final tokens = ReviewFeedback._tokens(text);
+  bool has(String token) => tokens.contains(ReviewFeedback._normalize(token));
+  bool phrase(String value) => text.contains(ReviewFeedback._normalize(value));
+  bool hasAny(Iterable<String> values) => values.any(has);
+  final introduction = phrase("i'm") || phrase('i am') || phrase('my name is');
+  final itIs = phrase("it's") || phrase('it is');
+  final numberWords = RegExp(
+    r'\b(zero|one|two|three|four|five|six|seven|eight|nine|ten)\b',
+  ).allMatches(text).length;
+  const weekdays = [
+    'monday',
+    'tuesday',
+    'wednesday',
+    'thursday',
+    'friday',
+    'saturday',
+    'sunday',
+  ];
+
+  return switch (id) {
+    // "I'm from …" and "I'm good" are other items, not a name.
+    'A0-P01' =>
+      phrase('my name is') ||
+          RegExp(
+            r"\bi(?:'m| am) (?!from\b|good\b|okay\b|ok\b|fine\b|great\b|tired\b)[a-z]",
+          ).hasMatch(text),
+    'A0-P02' => phrase("what's your name") || phrase('what is your name'),
+    'A0-P03' => phrase('nice to meet you'),
+    'A0-P04' => phrase('how do you spell'),
+    'A0-P05' => phrase('how are you'),
+    'A0-P06' => introduction && hasAny(['good', 'okay', 'tired']),
+    'A0-P07' =>
+      phrase("what's your phone number") || phrase('what is your phone number'),
+    'A0-P08' => numberWords >= 3,
+    'A0-P09' => phrase("what's this") || phrase('what is this'),
+    'A0-P10' => itIs && hasAny(['book', 'pen', 'bag', 'key', 'phone']),
+    'A0-P11' => phrase('where are you from'),
+    'A0-P12' => introduction && has('from') && tokens.length >= 3,
+    'A0-P13' => phrase('this is my') && tokens.length >= 4,
+    'A0-P14' => phrase('what day is it'),
+    'A0-P15' => itIs && hasAny(weekdays),
+    'A0-P16' => phrase('what time is it'),
+    'A0-P17' =>
+      itIs &&
+          (has('clock') ||
+              has("o'clock") ||
+              has('oclock') ||
+              phrase("o'clock")),
+    'A0-P18' => introduction && has('like') && tokens.length >= 3,
+    'A0-P19' => phrase('do you like'),
+    'A0-P20' =>
+      phrase('please say that again') || phrase('please speak slowly'),
+    _ when a0CoreItems.containsKey(id) && id.startsWith('A0-W') =>
+      has(word ?? a0CoreItems[id]!) || phrase(word ?? a0CoreItems[id]!),
+    _ => false,
+  };
+}

kouyu_english/lib/core/seed_courses.dart

@@ -1116,7 +1116,16 @@ bool matchesSegmentIndependent(String segmentId, String response) {
       .expand((segments) => segments)
       .where((item) => item.id == segmentId)
       .firstOrNull;
-  if (segment == null) return true;
+  if (segment == null) {
+    // Single-segment lessons: every group of the lesson's independent task
+    // has to be present. Unknown segments never pass.
+    final lessonId = segmentId.replaceFirst(RegExp(r'-[a-z]$'), '');
+    final groups = a0IndependentRequiredTerms[lessonId];
+    if (groups == null) return false;
+    return groups.every(
+      (group) => group.any((term) => _containsTerm(text, term)),
+    );
+  }
   if (segmentId == 'a0-04-a' || segmentId == 'a0-04-b') {
     final count = segment.independentRequiredTerms
         .where((term) => text.contains(_normalizeDialogueInput(term)))
@@ -1129,10 +1138,64 @@ bool matchesSegmentIndependent(String segmentId, String response) {
             .length >=
         3;
   }
-  return segment.independentRequiredTerms
-      .any((term) => text.contains(_normalizeDialogueInput(term)));
+  return segment.independentRequiredTerms.any(
+    (term) => text.contains(_normalizeDialogueInput(term)),
+  );
 }
 
+const _introductionTerms = [
+  "i'm + #word",
+  'i am + #word',
+  'my name is',
+  "my name's",
+];
+
+/// What the independent attempt of each single-segment lesson has to contain.
+/// Each inner list is one part of the task; a part passes when any of its
+/// terms appears. Terms follow the same syntax as [LessonDialogue.requiredTerms].
+const a0IndependentRequiredTerms = <String, List<List<String>>>{
+  // 介绍你的名字并回应 Nice to meet you
+  'a0-01': [
+    _introductionTerms,
+    ['nice to meet you'],
+  ],
+  // 介绍名字并拼读它
+  'a0-02': [
+    _introductionTerms,
+    ['#spelling'],
+  ],
+  // 问候并说出你的状态
+  'a0-03': [
+    ['hello', 'hi', 'hey', 'how are you'],
+    ['good', 'okay', 'ok', 'fine', 'great', 'tired'],
+  ],
+  // 说出一个身边物品
+  'a0-05': [
+    ["it's a", 'it is a', "it's an", 'it is an'],
+  ],
+  // 说来自哪里并反问对方
+  'a0-06': [
+    ["i'm from", 'i am from'],
+    ['where are you from', '#question'],
+  ],
+  // 介绍一位家人或朋友
+  'a0-07': [
+    ['this is my'],
+  ],
+  // 说一个喜好并反问
+  'a0-09': [
+    ['i like', 'i love'],
+    ['do you like', '#question'],
+  ],
+  // 完成姓名、地点、喜好和反问
+  'a0-10': [
+    _introductionTerms,
+    ["i'm from", 'i am from', 'from + #word'],
+    ['i like', 'i love'],
+    ['#question'],
+  ],
+};
+
 class LessonDialogue {
   const LessonDialogue({
     required this.goal,
@@ -1172,8 +1235,17 @@ bool _containsTerm(String text, String term) {
 }
 
 bool _matchesStructure(String text, String token) => switch (token) {
-  // Three or more letters said one by one, e.g. "S-H-E-N" or "s h e n".
-  '#spelling' => RegExp(r'(?:^|[^a-z])[a-z](?:[ -][a-z]){2,}').hasMatch(text),
+  // Letters said one by one ("S-H-E-N", "s h e n", "L-I"), or the spelled
+  // name typed as one word ("Shen", "aaa"). Case and hyphens are ignored.
+  '#spelling' =>
+    RegExp(
+          r'(?:^|[^a-z])[a-z](?:\s*[-\u2010-\u2015]\s*[a-z]|\s[a-z])+(?![a-z])',
+        ).hasMatch(text) ||
+        RegExp(r'^[a-z]{2,}$').hasMatch(
+          text
+              .replaceAll(RegExp(r'[-\u2010-\u2015]'), '')
+              .replaceAll(RegExp(r'^[^a-z]+|[^a-z]+$'), ''),
+        ),
   // Any spoken or written digit.
   '#digit' => RegExp(
     r'(?<![a-z])(zero|one|two|three|four|five|six|seven|eight|nine|ten)(?![a-z])|[0-9]',
@@ -1232,21 +1304,150 @@ const a0MeetDialogue = LessonDialogue(
   requiredTerms: [
     ["i'm + #word", 'i am + #word', 'my name is', "my name's", 'name is'],
     ["i'm from", 'i am from', 'from + #word'],
-    [
-      'good',
-      'okay',
-      'ok',
-      'fine',
-      'great',
-      'tired',
-      'i like',
-      'i love',
-    ],
+    ['good', 'okay', 'ok', 'fine', 'great', 'tired', 'i like', 'i love'],
     ['#question'],
   ],
   taskLabels: ['介绍姓名', '说明来自哪里', '表达状态或喜好', '反问对方'],
 );
 
+/// A free practice scene. It opens once [unlockAfterLessonId] is complete
+/// (always open when null) and only uses language taught up to that lesson.
+class DialogueScene {
+  const DialogueScene({
+    required this.id,
+    required this.title,
+    required this.summary,
+    required this.script,
+    required this.recapPrompt,
+    this.unlockAfterLessonId,
+  });
+
+  final String id;
+  final String title;
+  final String summary;
+  final LessonDialogue script;
+
+  /// The follow-up review prompt added after the scene is finished.
+  final String recapPrompt;
+  final String? unlockAfterLessonId;
+}
+
+const a0Scenes = [
+  DialogueScene(
+    id: 'a0-meet',
+    title: '初次见面',
+    summary: '介绍姓名、地点、状态或喜好，并反问对方',
+    script: a0MeetDialogue,
+    recapPrompt: '再用英语介绍一次自己。',
+  ),
+  DialogueScene(
+    id: 'a0-number',
+    title: '留个电话',
+    summary: '问候、报出号码、再说一遍，并反问对方',
+    unlockAfterLessonId: 'a0-04',
+    recapPrompt: '用英语报一次你的虚拟电话号码。',
+    script: LessonDialogue(
+      goal: '问候并交换一个虚拟电话号码',
+      prompts: [
+        'Hi! How are you today?',
+        'Good. What\u2019s your phone number? Use a fake number.',
+        'Sorry, please say it again.',
+        'Thanks! Now ask me one question.',
+      ],
+      hints: [
+        'I\u2019m good, thanks.',
+        'My number is one-three-eight.',
+        'One-three-eight.',
+        'What\u2019s your phone number?',
+      ],
+      translations: [
+        '嗨！你今天好吗？',
+        '好的。你的电话号码是多少？用一个虚拟号码。',
+        '抱歉，请再说一遍。',
+        '谢谢！现在问我一个问题。',
+      ],
+      requiredTerms: [
+        ['good', 'okay', 'ok', 'fine', 'great', 'tired'],
+        ['#digit'],
+        ['#digit'],
+        ['#question'],
+      ],
+      taskLabels: ['说出你今天的状态', '报出一个号码', '再说一次号码', '反问对方'],
+    ),
+  ),
+  DialogueScene(
+    id: 'a0-photo',
+    title: '看照片聊天',
+    summary: '介绍照片里的人和东西，说喜好，并反问对方',
+    unlockAfterLessonId: 'a0-07',
+    recapPrompt: '用英语介绍一位家人或朋友。',
+    script: LessonDialogue(
+      goal: '介绍照片里的人和物品',
+      prompts: [
+        'Nice photo! Who is this?',
+        'And what\u2019s this in the photo?',
+        'Where are you from?',
+        'Cool! Now ask me one question.',
+      ],
+      hints: [
+        'This is my sister.',
+        'It\u2019s a bag.',
+        'I\u2019m from Hong Kong.',
+        'Who is this? / What\u2019s this?',
+      ],
+      translations: ['照片真好！这是谁？', '照片里这个是什么？', '你来自哪里？', '真酷！现在问我一个问题。'],
+      requiredTerms: [
+        ['this is my', 'this is'],
+        ["it's a", 'it is a', "it's an", 'it is an'],
+        ["i'm from", 'i am from', 'from + #word'],
+        ['#question'],
+      ],
+      taskLabels: ['介绍照片里的人', '说出照片里的物品', '说出你来自哪里', '反问对方'],
+    ),
+  ),
+  DialogueScene(
+    id: 'a0-plan',
+    title: '约个时间',
+    summary: '说星期和整点，回答喜好，并反问对方',
+    unlockAfterLessonId: 'a0-09',
+    recapPrompt: '用英语说今天星期几和现在几点。',
+    script: LessonDialogue(
+      goal: '说明星期、时间和喜好',
+      prompts: [
+        'Hi! What day is it today?',
+        'What time is it now?',
+        'Do you like coffee or tea?',
+        'Me too! Now ask me one question.',
+      ],
+      hints: [
+        'It\u2019s Friday.',
+        'It\u2019s three o\u2019clock.',
+        'I like tea.',
+        'Do you like music?',
+      ],
+      translations: ['嗨！今天星期几？', '现在几点？', '你喜欢咖啡还是茶？', '我也是！现在问我一个问题。'],
+      requiredTerms: [
+        [
+          'monday',
+          'tuesday',
+          'wednesday',
+          'thursday',
+          'friday',
+          'saturday',
+          'sunday',
+        ],
+        ["o'clock", 'oclock', "it's + #digit", 'it is + #digit'],
+        ['i like', 'i love', 'yes', 'no', "i don't"],
+        ['#question'],
+      ],
+      taskLabels: ['说出今天星期几', '说出现在几点', '说出你的喜好', '反问对方'],
+    ),
+  ),
+];
+
+DialogueScene sceneById(String id) =>
+    a0Scenes.where((scene) => scene.id == id).firstOrNull ?? a0Scenes.first;
+
 const a0Dialogues = <String, LessonDialogue>{
   'a0-01': LessonDialogue(
     goal: '问候、介绍姓名并回应见面问候',
@@ -1341,7 +1542,12 @@ const a0Dialogues = <String, LessonDialogue>{
       ['my number is + #digit', "my number's + #digit", 'number is + #digit'],
       ['yes', 'no', "that's right", 'right', 'correct'],
       ['#digit'],
-      ["what's your phone number", 'what is your phone number', 'your phone number', 'your number'],
+      [
+        "what's your phone number",
+        'what is your phone number',
+        'your phone number',
+        'your number',
+      ],
     ],
     taskLabels: ['报出一个三位号码', '确认或纠正听到的号码', '再说一次这三个数字', '反问对方的号码'],
   ),
@@ -1422,7 +1628,12 @@ const a0Dialogues = <String, LessonDialogue>{
       ['who is this', "who's this"],
       ['this is my', 'this is'],
     ],
-    taskLabels: ['介绍一位家人或朋友', '完整说出 This is my … 句型', '反问 Who is this', '再介绍一个人'],
+    taskLabels: [
+      '介绍一位家人或朋友',
+      '完整说出 This is my … 句型',
+      '反问 Who is this',
+      '再介绍一个人',
+    ],
   ),
   'a0-08': LessonDialogue(
     goal: '说明星期或整点',
@@ -1440,7 +1651,15 @@ const a0Dialogues = <String, LessonDialogue>{
     ],
     translations: ['今天星期几？', '现在几点了？', '请说一个完整的时间句子。', '现在请问我今天是星期几！'],
     requiredTerms: [
-      ['monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday'],
+      [
+        'monday',
+        'tuesday',
+        'wednesday',
+        'thursday',
+        'friday',
+        'saturday',
+        'sunday',
+      ],
       ["o'clock", 'oclock', "#digit + o'clock"],
       ["it's + o'clock", "it is + o'clock", "it's + #digit", 'it is + #digit'],
       ['what day is it', 'what day', '#question'],
@@ -1488,7 +1707,13 @@ const a0Dialogues = <String, LessonDialogue>{
     requiredTerms: [
       ['say that again', 'again', 'pardon'],
       ['slowly', 'slow'],
-      ["what's your name", 'what is your name', 'where are you from', 'your name', '#question'],
+      [
+        "what's your name",
+        'what is your name',
+        'where are you from',
+        'your name',
+        '#question',
+      ],
       ['i like', 'i love'],
     ],
     taskLabels: ['请求对方重复', '请求对方放慢语速', '反问名字或来自哪里', '说出一件你喜欢的事物'],

kouyu_english/lib/core/writing_feedback.dart

@@ -105,7 +105,7 @@ class WritingFeedback {
     'a0-08-b' => '用 It is / It’s 加 Thursday、Friday、Saturday 或 Sunday。',
     'a0-08-c' => '用 It is / It’s 加数字和 o’clock，例如 It’s three o’clock。',
     'a0-01' => '试着同时写一句问候和姓名，例如：Hello. I’m …',
-    'a0-02' => '写出姓名，并把至少三个字母用空格或连字符拼出来。',
+    'a0-02' => '写出姓名并拼写一遍，例如 My name is Shen. S-H-E-N.',
     'a0-03' => '用 I’m / I am 加上你的状态，例如 good 或 tired。',
     'a0-04' => '用英文写出三个数字，例如 one-three-nine。',
     'a0-05' => '用 It’s / It is 加一个物品，例如 a pen。',

kouyu_english/lib/features/dialogue/dialogue_flow.dart

@@ -11,12 +11,20 @@ import '../../widgets/lexicon_lookup.dart';
 import '../../widgets/voice_answer.dart';
 
 class DialogueScenePage extends StatelessWidget {
-  const DialogueScenePage({super.key, required this.onStart, this.onBack});
-  final VoidCallback onStart;
+  const DialogueScenePage({
+    super.key,
+    required this.state,
+    required this.onStart,
+    this.onBack,
+  });
+  final AppState state;
+  final ValueChanged<String> onStart;
   final VoidCallback? onBack;
 
   @override
-  Widget build(BuildContext context) => AppPage(
+  Widget build(BuildContext context) {
+    final recommended = state.recommendedScene;
+    return AppPage(
       appBar: onBack != null
           ? AppBar(
               leading: IconButton(
@@ -30,35 +38,66 @@ class DialogueScenePage extends StatelessWidget {
       child: SpacedColumn(
         children: [
           const Eyebrow('按当前水平推荐'),
-        Text('选一个场景，开口练习。', style: Theme.of(context).textTheme.headlineMedium),
+          Text(
+            '选一个场景，开口练习。',
+            style: Theme.of(context).textTheme.headlineMedium,
+          ),
           Text(
             '每轮 4 次回答，完成明确任务后结束。',
             style: Theme.of(context).textTheme.bodyMedium,
           ),
-        SectionCard(
-          tint: AppColors.softGreen,
+          for (final scene in a0Scenes)
+            if (state.isSceneUnlocked(scene))
+              _OpenScene(
+                scene: scene,
+                recommended: scene.id == recommended.id,
+                onStart: () => onStart(scene.id),
+              )
+            else
+              _LockedScene(
+                title: scene.title,
+                note:
+                    'A0 · 学完第 ${lessonById(scene.unlockAfterLessonId!).number} 课后开放',
+              ),
+          const _LockedScene(title: '咖啡店点单', note: 'A1 · 后续版本开放'),
+        ],
+      ),
+    );
+  }
+}
+
+class _OpenScene extends StatelessWidget {
+  const _OpenScene({
+    required this.scene,
+    required this.recommended,
+    required this.onStart,
+  });
+  final DialogueScene scene;
+  final bool recommended;
+  final VoidCallback onStart;
+
+  @override
+  Widget build(BuildContext context) => SectionCard(
+    tint: recommended ? AppColors.softGreen : null,
     child: SpacedColumn(
       children: [
-              const Row(
+        Row(
           mainAxisAlignment: MainAxisAlignment.spaceBetween,
           children: [
             Text(
-                    '初次见面',
-                    style: TextStyle(fontSize: 17, fontWeight: FontWeight.w600),
-                  ),
-                  Text('A0', style: TextStyle(color: AppColors.green)),
-                ],
+              scene.title,
+              style: const TextStyle(fontSize: 17, fontWeight: FontWeight.w600),
             ),
             Text(
-                '介绍姓名、地点、状态或喜好，并反问对方',
-                style: Theme.of(context).textTheme.bodyMedium,
+              recommended ? 'A0 · 推荐' : 'A0',
+              style: const TextStyle(color: AppColors.green),
             ),
-              PrimaryButton(label: '开始对话', onPressed: onStart),
           ],
         ),
-        ),
-        const _LockedScene(title: '认识新同学', note: 'A0 · 后续版本开放'),
-        const _LockedScene(title: '咖啡店', note: 'A1 · 后续版本开放'),
+        Text(scene.summary, style: Theme.of(context).textTheme.bodyMedium),
+        recommended
+            ? PrimaryButton(label: '开始对话', onPressed: onStart)
+            : SecondaryButton(label: '开始对话', onPressed: onStart),
       ],
     ),
   );
@@ -94,10 +133,14 @@ class DialoguePage extends StatefulWidget {
     required this.state,
     required this.onFinished,
     this.isLessonDialogue = false,
+    this.sceneId = 'a0-meet',
   });
   final AppState state;
   final ValueChanged<DialogueSummaryData?> onFinished;
   final bool isLessonDialogue;
+
+  /// The free scene to run when this is not a lesson dialogue.
+  final String sceneId;
   @override
   State<DialoguePage> createState() => _DialoguePageState();
 }
@@ -124,8 +167,18 @@ class _DialoguePageState extends State<DialoguePage>
   /// the dialogue ends: the spec forbids interrupting a beginner turn by turn.
   String? latestFeedback;
 
-  /// The free scene stores its draft under its own id.
-  static const _sceneDraftId = 'scene-a0-meet';
+  DialogueScene get _scene => sceneById(widget.sceneId);
+
+  /// A free scene may use everything the learner has finished so far.
+  String get _furthestCompletedLessonId => a0SeedLessons
+      .lastWhere(
+        (lesson) => widget.state.completedLessonIds.contains(lesson.id),
+        orElse: () => a0SeedLessons.first,
+      )
+      .id;
+
+  /// Each free scene stores its draft under its own id.
+  String get _sceneDraftId => 'scene-${_scene.id}';
 
   /// Closing line for the turn after the last scripted prompt. It stays inside
   /// taught A0 language instead of the old "Wonderful — nice meeting you!".
@@ -143,7 +196,7 @@ class _DialoguePageState extends State<DialoguePage>
               .id,
           widget.state.activeLessonId,
         )
-      : a0MeetDialogue;
+      : _scene.script;
 
   /// Only exact sentence matches are trusted. The old positional fallback
   /// attached `script.translations[stage]` to whatever the AI happened to say,
@@ -286,8 +339,10 @@ class _DialoguePageState extends State<DialoguePage>
       return;
     }
     widget.state.recordDialogueAttempt(
-      taskId:
-          'dialogue-${widget.isLessonDialogue ? _lessonSegmentId : 'a0-meet'}-$stage',
+      taskId: widget.isLessonDialogue
+          ? 'dialogue-$_lessonSegmentId-$stage'
+          : 'dialogue-scene-${_scene.id}-$stage',
+      sceneId: widget.isLessonDialogue ? null : _scene.id,
       rawAnswer: text,
       assisted: usedHelp,
       spoken: usedVoice && !transcriptEdited,
@@ -320,7 +375,10 @@ class _DialoguePageState extends State<DialoguePage>
           : 'nothing more, the conversation is finished',
       allowedLanguage: widget.isLessonDialogue
           ? taughtLanguageUpTo(widget.state.activeLessonId)
-          : allTaughtLanguage,
+          : _scene.unlockAfterLessonId == null
+          // The always-open scene mixes every A0 topic, as its script does.
+          ? allTaughtLanguage
+          : taughtLanguageUpTo(_furthestCompletedLessonId),
       history: turns
           .map(
             (turn) => <String, String>{
@@ -409,7 +467,7 @@ class _DialoguePageState extends State<DialoguePage>
     final personalSentence = learnerTurns.isEmpty
         ? 'My name is …'
         : learnerTurns.first.text;
-    widget.state.addDialogueRecap(personalSentence);
+    widget.state.addDialogueRecap(personalSentence, sceneId: _scene.id);
     widget.onFinished(
       DialogueSummaryData(
         // Only the turns the learner actually passed are reported.
@@ -584,7 +642,7 @@ class _DialoguePageState extends State<DialoguePage>
           onPressed: () => widget.onFinished(null),
         ),
         title: Text(
-          '${widget.isLessonDialogue ? '课程对话' : '初次见面'} · ${finished ? totalStages : stage + 1} / $totalStages',
+          '${widget.isLessonDialogue ? '课程对话' : _scene.title} · ${finished ? totalStages : stage + 1} / $totalStages',
         ),
       ),
       child: SpacedColumn(

kouyu_english/lib/features/home/home_page.dart

@@ -12,12 +12,16 @@ class HomePage extends StatelessWidget {
     required this.onStartPrimaryTask,
     required this.onOpenDialogue,
     required this.onResumeLessonDialogue,
+    required this.onStartReinforcement,
+    required this.onOpenAssessment,
   });
 
   final AppState state;
   final VoidCallback onStartPrimaryTask;
   final VoidCallback onOpenDialogue;
   final VoidCallback onResumeLessonDialogue;
+  final VoidCallback onStartReinforcement;
+  final ValueChanged<String> onOpenAssessment;
 
   @override
   Widget build(BuildContext context) {
@@ -26,16 +30,21 @@ class HomePage extends StatelessWidget {
     final activeLesson = lessonById(state.activeLessonId);
     final activeSegment = state.activeSegmentIndexFor(activeLesson.id) + 1;
     final resumeDialogue = state.hasResumableLessonDialogue;
+    final stageStep = !resumeDialogue && !isReview && state.allLessonsComplete
+        ? _stageStep()
+        : null;
     final primaryTitle = resumeDialogue
         ? '继续第 ${activeLesson.number} 课的课程对话'
         : isReview
         ? '先复习 $count 项'
-        : '第 ${activeLesson.number} 课 · ${activeLesson.title}${activeLesson.segments.length > 1 ? ' · 第 $activeSegment/${activeLesson.segments.length} 段' : ''}';
+        : stageStep?.title ??
+              '第 ${activeLesson.number} 课 · ${activeLesson.title}${activeLesson.segments.length > 1 ? ' · 第 $activeSegment/${activeLesson.segments.length} 段' : ''}';
     final primaryNote = resumeDialogue
         ? '已保留你的对话进度和提示状态。'
         : isReview
         ? (state.reviewBacklog ? '有积压项目；先花几分钟清掉到期复习。' : '昨天练过的关键句，今天换个情境再用一次。')
-        : '预热词汇 → 听说读写 → 对话 → 独立尝试';
+        : stageStep?.note ?? '预热词汇 → 听说读写 → 对话 → 独立尝试';
+    final scene = state.recommendedScene;
 
     return AppPage(
       child: SpacedColumn(
@@ -80,7 +89,9 @@ class HomePage extends StatelessWidget {
                       ),
                     ),
                     Text(
-                      isReview ? '${(count * 2).clamp(2, 10)} 分钟' : '12 分钟',
+                      isReview
+                          ? '${(count * 2).clamp(2, 10)} 分钟'
+                          : stageStep?.minutes ?? '12 分钟',
                       style: const TextStyle(color: AppColors.green),
                     ),
                   ],
@@ -94,10 +105,10 @@ class HomePage extends StatelessWidget {
                       ? '继续对话'
                       : isReview
                       ? '开始复习'
-                      : '开始今天的学习',
+                      : stageStep?.action ?? '开始今天的学习',
                   onPressed: resumeDialogue
                       ? onResumeLessonDialogue
-                      : onStartPrimaryTask,
+                      : stageStep?.onPressed ?? onStartPrimaryTask,
                 ),
               ],
             ),
@@ -110,7 +121,7 @@ class HomePage extends StatelessWidget {
                   style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600),
                 ),
                 Text(
-                  '初次见面 · 4 个任务 · 文字或语音输入',
+                  '${scene.title} · ${scene.script.prompts.length} 个任务 · 文字或语音输入',
                   style: Theme.of(context).textTheme.bodyMedium,
                 ),
                 SecondaryButton(label: '开始情境对话', onPressed: onOpenDialogue),
@@ -122,6 +133,56 @@ class HomePage extends StatelessWidget {
       ),
     );
   }
+
+  /// What comes after the last A0 lesson: consolidation until the core items
+  /// are ready, then the stage assessment, then waiting for A1 content.
+  _StageStep _stageStep() {
+    final usable =
+        '可使用 ${state.coreUsableCount}/48 · 已掌握 ${state.coreMasteredCount}/30';
+    if (state.a0Passed) {
+      return _StageStep(
+        title: 'A0 已通过',
+        note: 'A1 课程准备中。先用巩固练习和情境对话保持手感。',
+        action: '安排一题巩固练习',
+        minutes: '3 分钟',
+        onPressed: onStartReinforcement,
+      );
+    }
+    final packId = state.nextAssessmentPackId;
+    if (state.a0AssessmentReady && packId != null) {
+      return _StageStep(
+        title: 'A0 阶段评估 · $packId',
+        note: '$usable。可以开始阶段评估，两套评估间隔至少 24 小时。',
+        action: '开始阶段评估',
+        minutes: '15 分钟',
+        onPressed: () => onOpenAssessment(packId),
+      );
+    }
+    return _StageStep(
+      title: state.a0AssessmentReady ? '第二套评估 24 小时后开放' : 'A0 课程已学完',
+      note: state.a0AssessmentReady
+          ? '第一套评估已通过。等待期间继续巩固。'
+          : '$usable。继续按时复习、做情境对话，达到要求后开放阶段评估。',
+      action: '安排一题巩固练习',
+      minutes: '3 分钟',
+      onPressed: onStartReinforcement,
+    );
+  }
+}
+
+class _StageStep {
+  const _StageStep({
+    required this.title,
+    required this.note,
+    required this.action,
+    required this.minutes,
+    required this.onPressed,
+  });
+  final String title;
+  final String note;
+  final String action;
+  final String minutes;
+  final VoidCallback onPressed;
 }
 
 class _FrameworkNote extends StatelessWidget {

kouyu_english/lib/features/lesson/lesson_flow.dart

@@ -38,6 +38,10 @@ class _LessonFlowState extends State<LessonFlow> {
   final writingController = TextEditingController();
   final independentController = TextEditingController();
   int selectedAnswer = -1;
+
+  /// Set once a wrong meaning is picked, so only a first-try choice counts as
+  /// recognition evidence.
+  bool listeningMissed = false;
   int previewIndex = 0;
   bool listeningAudioPlayed = false;
   bool showWritingHelp = true;
@@ -108,7 +112,12 @@ class _LessonFlowState extends State<LessonFlow> {
           correctAnswer: activity.answers.first,
           selectedAnswer: selectedAnswer,
           audioPlayed: listeningAudioPlayed,
-          onSelected: (value) => setState(() => selectedAnswer = value),
+          onSelected: (value) => setState(() {
+            selectedAnswer = value;
+            if (listeningOptions[value] != activity.answers.first) {
+              listeningMissed = true;
+            }
+          }),
           onPlayed: () => setState(() => listeningAudioPlayed = true),
           onLookup: () => showLexiconLookup(
             context,
@@ -118,7 +127,8 @@ class _LessonFlowState extends State<LessonFlow> {
           onContinue:
               selectedAnswer >= 0 &&
                   listeningOptions[selectedAnswer] == activity.answers.first
-              ? widget.state.completeListening
+              ? () =>
+                    widget.state.completeListening(recognized: !listeningMissed)
               : null,
         );
       case LessonStep.speaking:
@@ -126,7 +136,7 @@ class _LessonFlowState extends State<LessonFlow> {
           state: widget.state,
           text: activity.speaking,
           keepRecording: widget.state.keepRecordings,
-          onContinue: () => widget.state.completeSpeaking(assisted: true),
+          onContinue: widget.state.completeSpeaking,
         );
       case LessonStep.reading:
         content = _ReadingStep(

kouyu_english/lib/features/onboarding/onboarding_pages.dart

@@ -3,7 +3,11 @@ import 'package:flutter/material.dart';
 import '../../core/app_state.dart';
 import '../../core/app_theme.dart';
 import '../../core/models.dart';
+import '../../core/review_feedback.dart';
+import '../../core/seed_courses.dart';
+import '../../core/voice_service.dart';
 import '../../widgets/app_widgets.dart';
+import '../../widgets/voice_answer.dart';
 
 class WelcomePage extends StatefulWidget {
   const WelcomePage({super.key, required this.state, required this.onContinue});
@@ -16,13 +20,11 @@ class WelcomePage extends StatefulWidget {
 }
 
 class _WelcomePageState extends State<WelcomePage> {
-  late LearningGoal selectedGoal;
   late int selectedMinutes;
 
   @override
   void initState() {
     super.initState();
-    selectedGoal = widget.state.goal;
     selectedMinutes = widget.state.dailyMinutes;
   }
 
@@ -72,16 +74,6 @@ class _WelcomePageState extends State<WelcomePage> {
             style: Theme.of(context).textTheme.headlineMedium,
           ),
           const Text('从真实生活场景开始，先做到听得懂、说得清。'),
-          _ChoiceGroup<LearningGoal>(
-            title: '你的主要目标',
-            value: selectedGoal,
-            options: const {
-              LearningGoal.dailyLife: '日常生活',
-              LearningGoal.travel: '旅行',
-              LearningGoal.workStarter: '工作起步',
-            },
-            onChanged: (value) => setState(() => selectedGoal = value),
-          ),
           _ChoiceGroup<int>(
             title: '每天学习多久？',
             value: selectedMinutes,
@@ -91,9 +83,7 @@ class _WelcomePageState extends State<WelcomePage> {
           PrimaryButton(
             label: '继续',
             onPressed: () {
-              widget.state
-                ..setGoal(selectedGoal)
-                ..setDailyMinutes(selectedMinutes);
+              widget.state.setDailyMinutes(selectedMinutes);
               widget.onContinue();
             },
           ),
@@ -119,8 +109,25 @@ class PlacementPage extends StatefulWidget {
   State<PlacementPage> createState() => _PlacementPageState();
 }
 
-class _PlacementPageState extends State<PlacementPage> {
+enum _PlacementPhase { selfReport, listen, readAloud, answer, result }
+
+class _PlacementPageState extends State<PlacementPage>
+    with VoiceAnswerMixin<PlacementPage> {
+  static const _listeningText = 'Hello. My name is Mia. Nice to meet you.';
+  static const _listeningOptions = [
+    '你好，我叫 Mia，很高兴认识你。',
+    '你好，我来自 Mia，今天很开心。',
+    '再见，Mia，明天见。',
+  ];
+  static const _readAloudText = 'Hello. My name is ...';
+
   late PlacementLevel selected;
+  var phase = _PlacementPhase.selfReport;
+  int listeningChoice = -1;
+  final answerController = TextEditingController();
+
+  @override
+  AppState get voiceState => widget.state;
 
   @override
   void initState() {
@@ -128,25 +135,94 @@ class _PlacementPageState extends State<PlacementPage> {
     selected = widget.state.placement;
   }
 
+  @override
+  void dispose() {
+    VoiceService.instance.stopSpeaking();
+    disposeVoiceAnswer(keepRecording: false);
+    answerController.dispose();
+    super.dispose();
+  }
+
+  bool get _understoodGreeting => listeningChoice == 0;
+
+  bool get _answeredName =>
+      coreItemUsedIn('A0-P01', answerController.text.trim());
+
+  /// Placement only picks an A0 starting point until A1 content is frozen, and
+  /// it never marks a lesson as passed.
+  String get _suggestedLessonId =>
+      _understoodGreeting && _answeredName ? 'a0-02' : 'a0-01';
+
+  String get _reason => _understoodGreeting && _answeredName
+      ? '你已经能听懂问候，也能说出自己的名字，可以从拼写名字开始。'
+      : _understoodGreeting
+      ? '你能听懂问候，先把自我介绍说完整会更稳。'
+      : '先从问候和介绍名字开始，打好第一句的基础。';
+
+  void _back() {
+    VoiceService.instance.stopSpeaking();
+    switch (phase) {
+      case _PlacementPhase.selfReport:
+        widget.onBack?.call();
+      case _PlacementPhase.listen:
+        setState(() => phase = _PlacementPhase.selfReport);
+      case _PlacementPhase.readAloud:
+        setState(() => phase = _PlacementPhase.listen);
+      case _PlacementPhase.answer:
+        setState(() => phase = _PlacementPhase.readAloud);
+      case _PlacementPhase.result:
+        setState(() => phase = _PlacementPhase.answer);
+    }
+  }
+
+  void _startFrom(String lessonId) {
+    widget.state.setPlacementStartLesson(lessonId);
+    widget.onStart();
+  }
+
+  Future<void> _toggleVoiceAnswer() async {
+    if (aiVoiceRecording) {
+      await finishVoiceInput(
+        keepAudio: false,
+        onTranscript: (text) => answerController.text = text,
+      );
+      return;
+    }
+    await startVoiceInput();
+  }
+
   @override
   Widget build(BuildContext context) {
+    final showBack =
+        widget.onBack != null || phase != _PlacementPhase.selfReport;
+    return AppPage(
+      appBar: showBack
+          ? AppBar(
+              leading: IconButton(
+                icon: const Icon(Icons.arrow_back),
+                tooltip: "返回",
+                onPressed: _back,
+              ),
+              title: const Text("基础定位"),
+            )
+          : null,
+      child: switch (phase) {
+        _PlacementPhase.selfReport => _selfReport(context),
+        _PlacementPhase.listen => _listen(context),
+        _PlacementPhase.readAloud => _readAloud(context),
+        _PlacementPhase.answer => _answer(context),
+        _PlacementPhase.result => _result(context),
+      },
+    );
+  }
+
+  Widget _selfReport(BuildContext context) {
     const labels = {
       PlacementLevel.beginner: ('完全零基础', '从你好、自我介绍开始'),
       PlacementLevel.someBasics: ('能说一点', '认识常见单词或短句'),
       PlacementLevel.simpleConversation: ('能简单对话', '想说得更自然、更有信心'),
     };
-    return AppPage(
-      appBar: widget.onBack != null
-          ? AppBar(
-              leading: IconButton(
-                icon: const Icon(Icons.arrow_back),
-                tooltip: "返回",
-                onPressed: widget.onBack,
-              ),
-              title: const Text("基础定位"),
-            )
-          : null,
-      child: SpacedColumn(
+    return SpacedColumn(
       spacing: 14,
       children: [
         const Eyebrow('第一步 · 约 3 分钟'),
@@ -163,17 +239,183 @@ class _PlacementPageState extends State<PlacementPage> {
           label: '开始 3 分钟定位',
           onPressed: () {
             widget.state.setPlacement(selected);
-              widget.onStart();
+            setState(() => phase = _PlacementPhase.listen);
           },
         ),
         Center(
           child: TextButton(
-              onPressed: widget.onStart,
+            onPressed: () => _startFrom('a0-01'),
             child: const Text('直接从第一课开始'),
           ),
         ),
       ],
+    );
+  }
+
+  Widget _listen(BuildContext context) => SpacedColumn(
+    spacing: 14,
+    children: [
+      const Eyebrow('定位 · 1 / 3'),
+      Text('听一听，选出意思。', style: Theme.of(context).textTheme.headlineMedium),
+      SecondaryButton(
+        label: '播放句子',
+        onPressed: () => VoiceService.instance.speak(_listeningText),
       ),
+      for (var index = 0; index < _listeningOptions.length; index++)
+        SectionCard(
+          tint: listeningChoice == index ? AppColors.softGreen : null,
+          onTap: () => setState(() => listeningChoice = index),
+          child: Row(
+            children: [
+              Icon(
+                listeningChoice == index
+                    ? Icons.radio_button_checked
+                    : Icons.radio_button_off,
+                color: listeningChoice == index
+                    ? AppColors.green
+                    : AppColors.muted,
+              ),
+              const SizedBox(width: 10),
+              Expanded(child: Text(_listeningOptions[index])),
+            ],
+          ),
+        ),
+      PrimaryButton(
+        label: '下一题',
+        onPressed: listeningChoice < 0
+            ? null
+            : () => setState(() => phase = _PlacementPhase.readAloud),
+      ),
+      Center(
+        child: TextButton(
+          onPressed: () => setState(() {
+            listeningChoice = -1;
+            phase = _PlacementPhase.readAloud;
+          }),
+          child: const Text('听不懂，下一题'),
+        ),
+      ),
+    ],
+  );
+
+  Widget _readAloud(BuildContext context) => SpacedColumn(
+    spacing: 14,
+    children: [
+      const Eyebrow('定位 · 2 / 3'),
+      Text('跟着读一句。', style: Theme.of(context).textTheme.headlineMedium),
+      const Text(
+        _readAloudText,
+        textAlign: TextAlign.center,
+        style: TextStyle(fontSize: 26, fontWeight: FontWeight.w600),
+      ),
+      SecondaryButton(
+        label: '播放示范音',
+        onPressed: () => VoiceService.instance.speak(_readAloudText),
+      ),
+      const SectionCard(
+        tint: AppColors.surfaceMuted,
+        child: Text('这一题只是开口热身，不录音、不打分，可以跳过。'),
+      ),
+      PrimaryButton(
+        label: '我读完了',
+        onPressed: () => setState(() => phase = _PlacementPhase.answer),
+      ),
+      Center(
+        child: TextButton(
+          onPressed: () => setState(() => phase = _PlacementPhase.answer),
+          child: const Text('现在不方便开口，跳过'),
+        ),
+      ),
+    ],
+  );
+
+  Widget _answer(BuildContext context) => SpacedColumn(
+    spacing: 14,
+    children: [
+      const Eyebrow('定位 · 3 / 3'),
+      Text('回答这个问题。', style: Theme.of(context).textTheme.headlineMedium),
+      SectionCard(
+        tint: AppColors.surfaceMuted,
+        child: Row(
+          children: [
+            const Expanded(
+              child: Text(
+                'What is your name?',
+                style: TextStyle(fontSize: 20, fontWeight: FontWeight.w600),
+              ),
+            ),
+            IconButton(
+              tooltip: '播放问题',
+              icon: const Icon(Icons.volume_up_outlined),
+              onPressed: () =>
+                  VoiceService.instance.speak('What is your name?'),
+            ),
+          ],
+        ),
+      ),
+      TextField(
+        controller: answerController,
+        decoration: const InputDecoration(hintText: '用英语输入你的回答'),
+        onChanged: (_) => setState(() {}),
+      ),
+      SecondaryButton(
+        label: transcribing ? '正在识别…' : (aiVoiceRecording ? '说完了，识别' : '用语音回答'),
+        onPressed: transcribing ? null : _toggleVoiceAnswer,
+      ),
+      PrimaryButton(
+        label: '查看建议',
+        onPressed: aiVoiceRecording || transcribing
+            ? null
+            : () => setState(() => phase = _PlacementPhase.result),
+      ),
+      Center(
+        child: TextButton(
+          onPressed: () => setState(() {
+            answerController.clear();
+            phase = _PlacementPhase.result;
+          }),
+          child: const Text('还不会说，查看建议'),
+        ),
+      ),
+    ],
+  );
+
+  Widget _result(BuildContext context) {
+    final lesson = lessonById(_suggestedLessonId);
+    return SpacedColumn(
+      spacing: 14,
+      children: [
+        const Eyebrow('定位结果'),
+        Text(
+          '建议从 A0 第 ${lesson.number} 课开始',
+          style: Theme.of(context).textTheme.headlineMedium,
+        ),
+        SectionCard(
+          tint: AppColors.softGreen,
+          child: SpacedColumn(
+            spacing: 6,
+            children: [
+              Text(
+                '第 ${lesson.number} 课 · ${lesson.title}',
+                style: const TextStyle(fontWeight: FontWeight.w600),
+              ),
+              Text(_reason),
+            ],
+          ),
+        ),
+        const Text('前面的课程随时可以回去学，定位不会跳过任何复习。'),
+        PrimaryButton(
+          label: '开始今天学习',
+          onPressed: () => _startFrom(_suggestedLessonId),
+        ),
+        if (_suggestedLessonId != 'a0-01')
+          Center(
+            child: TextButton(
+              onPressed: () => _startFrom('a0-01'),
+              child: const Text('从更简单内容开始'),
+            ),
+          ),
+      ],
     );
   }
 }

kouyu_english/lib/features/shell/learning_shell.dart

@@ -26,6 +26,7 @@ class _LearningShellState extends State<LearningShell> {
   var route = _ShellRoute.tab;
   _ShellRoute? previousRoute;
   bool dialogueInLesson = false;
+  String sceneId = 'a0-meet';
   AssessmentPack? assessmentPack;
   DialogueSummaryData? dialogueSummary;
 
@@ -45,9 +46,10 @@ class _LearningShellState extends State<LearningShell> {
     route = _ShellRoute.scene;
   });
 
-  void showDialogue({bool inLesson = false}) => setState(() {
+  void showDialogue({bool inLesson = false, String? scene}) => setState(() {
     previousRoute = route;
     dialogueInLesson = inLesson;
+    if (scene != null) sceneId = scene;
     route = _ShellRoute.dialogue;
   });
 
@@ -125,13 +127,16 @@ class _LearningShellState extends State<LearningShell> {
         );
       case _ShellRoute.scene:
         body = DialogueScenePage(
-          onStart: showDialogue,
+          state: widget.state,
+          onStart: (id) => showDialogue(scene: id),
           onBack: () => showTab(tab),
         );
       case _ShellRoute.dialogue:
         body = DialoguePage(
+          key: ValueKey(dialogueInLesson ? 'lesson' : 'scene-$sceneId'),
           state: widget.state,
           isLessonDialogue: dialogueInLesson,
+          sceneId: sceneId,
           onFinished: (summary) {
             if (dialogueInLesson) {
               showLesson();
@@ -147,7 +152,7 @@ class _LearningShellState extends State<LearningShell> {
           summary: dialogueSummary!,
           onHome: () => showTab(AppTab.home),
           onLesson: showLesson,
-          onRetry: showDialogue,
+          onRetry: () => showDialogue(scene: sceneId),
           onBack: () => showTab(tab),
         );
       case _ShellRoute.settings:
@@ -194,7 +199,8 @@ class _LearningShellState extends State<LearningShell> {
                   selectedIndex: tab.index,
                   height: 70,
                   indicatorColor: AppColors.softGreen,
-                  onDestinationSelected: (index) => showTab(AppTab.values[index]),
+                  onDestinationSelected: (index) =>
+                      showTab(AppTab.values[index]),
                   destinations: const [
                     NavigationDestination(
                       icon: Icon(Icons.home_outlined),
@@ -243,6 +249,16 @@ class _LearningShellState extends State<LearningShell> {
           },
           onOpenDialogue: showDialogueScene,
           onResumeLessonDialogue: () => showDialogue(inLesson: true),
+          onStartReinforcement: () {
+            widget.state.scheduleA0Reinforcement();
+            showTab(AppTab.review);
+          },
+          onOpenAssessment: (packId) {
+            final pack = a0AssessmentPacks
+                .where((item) => item.id == packId)
+                .firstOrNull;
+            if (pack != null) showAssessment(pack);
+          },
         );
       case AppTab.learn:
         return _LearningMap(
@@ -258,7 +274,10 @@ class _LearningShellState extends State<LearningShell> {
           state: widget.state,
         );
       case AppTab.dialogue:
-        return DialogueScenePage(onStart: showDialogue);
+        return DialogueScenePage(
+          state: widget.state,
+          onStart: (id) => showDialogue(scene: id),
+        );
       case AppTab.review:
         return ReviewPage(
           state: widget.state,

kouyu_english/test/app_state_test.dart

@@ -123,6 +123,17 @@ void main() {
     final state = AppState();
     state.reviewQueue.add(dueItem());
     final item = state.reviewQueue.first;
+    state.attemptEvidence.add(
+      AttemptEvidence(
+        id: 'recognized',
+        itemId: item.id,
+        taskId: 'lesson-a0-06-a-listening-check',
+        skill: '听辨识别',
+        inputMode: 'choice',
+        outcome: EvidenceKind.independentSuccess,
+        createdAt: DateTime.now().subtract(const Duration(days: 20)),
+      ),
+    );
 
     for (var index = 0; index < 4; index++) {
       final current = state.reviewQueue.firstWhere(
@@ -141,6 +152,13 @@ void main() {
 
     expect(state.mastery[item.id]!.checkpoint, 4);
     expect(state.mastery[item.id]!.status, MasteryStatus.master);
+    // Later checks rotate to other reviewed situations.
+    expect(
+      state.reviewQueue
+          .firstWhere((candidate) => candidate.id == item.id)
+          .variantIndex,
+      4,
+    );
     expect(
       state.reviewQueue
           .firstWhere((candidate) => candidate.id == item.id)
@@ -153,6 +171,17 @@ void main() {
   test('mastery can be rebuilt from spaced review evidence', () {
     final state = AppState();
     final base = DateTime.utc(2026, 9, 1);
+    state.attemptEvidence.add(
+      AttemptEvidence(
+        id: 'recognized',
+        itemId: 'A0-P12',
+        taskId: 'lesson-a0-06-a-listening-check',
+        skill: '听辨识别',
+        inputMode: 'choice',
+        outcome: EvidenceKind.independentSuccess,
+        createdAt: base,
+      ),
+    );
     for (var index = 0; index < 4; index++) {
       state.attemptEvidence.add(
         AttemptEvidence(
@@ -163,14 +192,75 @@ void main() {
           inputMode: 'text',
           outcome: EvidenceKind.independentSuccess,
           createdAt: base.add(Duration(days: index + 1)),
+          variantIndex: index,
+        ),
+      );
+    }
+
+    state.rebuildMasteryFromEvidence();
+
+    expect(state.mastery['A0-P12']!.checkpoint, 4);
+    expect(state.mastery['A0-P12']!.status, MasteryStatus.master);
+  });
+
+  test('four checkpoints without every kind of evidence are not mastery', () {
+    final state = AppState();
+    final base = DateTime.utc(2026, 9, 1);
+    for (var index = 0; index < 4; index++) {
+      state.attemptEvidence.add(
+        AttemptEvidence(
+          id: 'same-context-$index',
+          itemId: 'A0-P12',
+          taskId: 'review-A0-P12',
+          skill: '口语表达',
+          inputMode: 'text',
+          outcome: EvidenceKind.independentSuccess,
+          createdAt: base.add(Duration(days: index + 1)),
         ),
       );
     }
 
     state.rebuildMasteryFromEvidence();
 
+    // No recognition success and never used outside the original situation.
     expect(state.mastery['A0-P12']!.checkpoint, 4);
-    expect(state.mastery['A0-P12']!.status, MasteryStatus.master);
+    expect(state.mastery['A0-P12']!.status, MasteryStatus.recall);
+  });
+
+  test('a review success never lowers an existing status', () {
+    final state = AppState();
+    state.mastery['A0-P12'] = const MasteryItem(
+      id: 'A0-P12',
+      label: "I'm from [place].",
+      status: MasteryStatus.use,
+      evidence: [],
+      checkpoint: 1,
+    );
+    state.reviewQueue.add(dueItem());
+
+    state.completeReview(state.reviewQueue.single, assisted: false);
+
+    expect(state.mastery['A0-P12']!.status, MasteryStatus.use);
+  });
+
+  test('review checkpoints follow days 1, 3, 7 and 14', () {
+    final state = AppState();
+    state.reviewQueue.add(dueItem());
+    final gaps = <int>[];
+    for (var index = 0; index < 3; index++) {
+      final current = state.reviewQueue.single;
+      state.reviewQueue[0] = current.copyWith(
+        dueAt: DateTime.now(),
+        lastProgressedAt: DateTime.now().subtract(const Duration(days: 1)),
+      );
+      state.completeReview(state.reviewQueue.single, assisted: false);
+      gaps.add(
+        state.reviewQueue.single.dueAt.difference(DateTime.now()).inHours ~/
+                24 +
+            1,
+      );
+    }
+    expect(gaps, [2, 4, 7]);
   });
 
   test(
@@ -265,7 +355,7 @@ void main() {
       final state = AppState();
       state.completePreview();
       state.completeListening();
-      state.completeSpeaking(assisted: true);
+      state.completeSpeaking();
       state.completeReading();
       state.completeWriting(assisted: true);
 
@@ -553,7 +643,9 @@ void main() {
       correct: true,
     );
     expect(state.attemptEvidence, hasLength(1));
-    expect(state.mastery['A0-P12']!.status, MasteryStatus.recognize);
+    // An unaided adaptive answer is recall in a situation other than the
+    // lesson, which is what usable means.
+    expect(state.mastery['A0-P12']!.status, MasteryStatus.use);
   });
 
   test(
@@ -640,9 +732,51 @@ void main() {
     final speaking = state.attemptEvidence.where(
       (entry) => entry.taskId == 'lesson-$segmentId-speaking',
     );
-    expect(speaking, hasLength(1));
-    expect(speaking.single.itemId, targets.last);
-    expect(speaking.single.outcome, EvidenceKind.independentSuccess);
+    // Follow-reading is assisted practice for every target, never
+    // independent evidence for one of them.
+    expect(speaking.map((entry) => entry.itemId), targets);
+    expect(
+      speaking.every((entry) => entry.outcome == EvidenceKind.assisted),
+      isTrue,
+    );
+
+    state.completeReading();
+    state.completeWriting(rawAnswer: 'Hello. My name is Mia.');
+    final writing = state.attemptEvidence.where(
+      (entry) => entry.taskId == 'lesson-$segmentId-writing',
+    );
+    expect(writing.map((entry) => entry.itemId).toSet(), {'A0-W36', 'A0-P01'});
+  });
+
+  test('a first-try listening choice is recognition evidence', () {
+    final state = AppState();
+    state.completePreview();
+    state.completeListening(recognized: true);
+
+    for (final id in lessonById('a0-01').targetItemIds) {
+      expect(state.mastery[id]!.status, MasteryStatus.recognize);
+    }
+  });
+
+  test('scene dialogue credits taught items the learner actually used', () {
+    final state = AppState();
+    state.completePreview();
+    state.completeListening();
+
+    state.recordDialogueAttempt(
+      taskId: 'dialogue-scene-a0-meet-0',
+      rawAnswer: 'Hi! My name is Mia.',
+      assisted: false,
+      sceneId: 'a0-meet',
+    );
+
+    final used = state.attemptEvidence
+        .where((entry) => entry.taskId == 'dialogue-scene-a0-meet-0')
+        .map((entry) => entry.itemId)
+        .toSet();
+    expect(used, {'A0-W37', 'A0-P01'});
+    expect(state.mastery['A0-P01']!.status, MasteryStatus.use);
+    expect(state.mastery['A0-P03']!.status, MasteryStatus.newItem);
   });
 
   test(
@@ -659,13 +793,17 @@ void main() {
         assisted: false,
         rawAnswer: 'Hello. I am Mia.',
       );
-      final primary = lessonById('a0-01').targetItemIds.last;
+      const introduced = 'A0-P01';
 
       state.mastery.clear();
       state.rebuildMasteryFromEvidence();
 
-      expect(state.mastery[primary]!.firstTaughtAt, isNotNull);
-      expect(state.mastery[primary]!.status, MasteryStatus.use);
+      expect(state.mastery[introduced]!.firstTaughtAt, isNotNull);
+      // Recalled inside the lesson, not yet used in another situation.
+      expect(state.mastery[introduced]!.status, MasteryStatus.recall);
+      // The answer never said "Nice to meet you", so that target gets no
+      // production evidence from it.
+      expect(state.mastery['A0-P03']!.status, MasteryStatus.newItem);
       expect(
         state.mastery[lessonById('a0-01').targetItemIds.first]!.firstTaughtAt,
         isNotNull,
@@ -770,6 +908,79 @@ void main() {
     expect(matchesSegmentIndependent('a0-08-b', 'It is Monday.'), isFalse);
   });
 
+  test('single-segment independent attempts reject off-task answers', () {
+    const offTask = 'abc';
+    for (final lessonId in [
+      'a0-01',
+      'a0-02',
+      'a0-03',
+      'a0-05',
+      'a0-06',
+      'a0-07',
+      'a0-09',
+      'a0-10',
+    ]) {
+      expect(
+        matchesSegmentIndependent('$lessonId-a', offTask),
+        isFalse,
+        reason: lessonId,
+      );
+    }
+    expect(
+      matchesSegmentIndependent('a0-01-a', "Hi, I'm Mia. Nice to meet you."),
+      isTrue,
+    );
+    expect(matchesSegmentIndependent('a0-01-a', "Hi, I'm Mia."), isFalse);
+    expect(matchesSegmentIndependent('a0-05-a', "It's a pen."), isTrue);
+    expect(
+      matchesSegmentIndependent(
+        'a0-06-a',
+        "I'm from Guangzhou. Where are you from?",
+      ),
+      isTrue,
+    );
+    expect(
+      matchesSegmentIndependent('a0-06-a', "I'm from Guangzhou."),
+      isFalse,
+    );
+    expect(
+      matchesSegmentIndependent(
+        'a0-10-a',
+        "I'm Mia. I'm from Guangzhou. I like tea. Do you like tea?",
+      ),
+      isTrue,
+    );
+  });
+
+  test('each free scene keeps its own daily recap', () {
+    final state = AppState();
+
+    state.addDialogueRecap('My name is Alex.');
+    state.addDialogueRecap('It is Monday.', sceneId: 'a0-plan');
+
+    expect(
+      state.reviewQueue.where(
+        (item) => item.id.startsWith('dialogue-a0-meet-'),
+      ),
+      hasLength(1),
+    );
+    final plan = state.reviewQueue.singleWhere(
+      (item) => item.id.startsWith('dialogue-a0-plan-'),
+    );
+    expect(plan.prompt, sceneById('a0-plan').recapPrompt);
+  });
+
+  test('scenes open with their lessons and rotate the recommendation', () {
+    final state = AppState();
+    expect(a0Scenes.where(state.isSceneUnlocked).map((scene) => scene.id), [
+      'a0-meet',
+    ]);
+    state.completedLessonIds.addAll(['a0-01', 'a0-02', 'a0-03', 'a0-04']);
+    expect(state.recommendedScene.id, 'a0-number');
+    state.addDialogueRecap('My number is one two three.', sceneId: 'a0-number');
+    expect(state.recommendedScene.id, 'a0-meet');
+  });
+
   test('completed independent dialogue creates one daily non-core recap', () {
     final state = AppState();
 
@@ -797,7 +1008,7 @@ void main() {
       for (var segment = 0; segment < lesson.segments.length; segment++) {
         state.completePreview();
         state.completeListening();
-        state.completeSpeaking(assisted: true);
+        state.completeSpeaking();
         state.completeReading();
         state.completeWriting(assisted: true);
         state.completeLessonDialogue();
@@ -893,10 +1104,7 @@ void main() {
       checkOpenAssessmentAnswer(speaking[6], 'Please speak slowly.'),
       isTrue,
     );
-    expect(
-      checkOpenAssessmentAnswer(speaking[6], 'Repeat, please.'),
-      isTrue,
-    );
+    expect(checkOpenAssessmentAnswer(speaking[6], 'Repeat, please.'), isTrue);
   });
 
   test('finishLesson advances activeLessonId to next available lesson', () {
@@ -904,7 +1112,7 @@ void main() {
     expect(state.activeLessonId, 'a0-01');
     state.completePreview();
     state.completeListening();
-    state.completeSpeaking(assisted: false);
+    state.completeSpeaking();
     state.completeReading();
     state.completeWriting(assisted: false);
     state.completeLessonDialogue();
@@ -916,6 +1124,68 @@ void main() {
     expect(state.activeLessonId, 'a0-02');
   });
 
+  void finishActiveLesson(AppState state) {
+    state.completePreview();
+    state.completeListening();
+    state.completeSpeaking();
+    state.completeReading();
+    state.completeWriting(assisted: true);
+    state.completeLessonDialogue();
+    state.completeIndependentAttempt(assisted: true);
+    state.finishLesson();
+  }
+
+  test('switching lessons clears step flags from the previous lesson', () {
+    final state = AppState();
+    state.completePreview();
+    state.completeListening();
+    state.completeSpeaking();
+    state.completeReading();
+    state.completeWriting(assisted: true);
+    state.completeLessonDialogue();
+    state.completeIndependentAttempt(assisted: true);
+    state.completedLessonIds.add('a0-01');
+
+    state.openLesson('a0-02');
+
+    expect(state.lessonCanComplete, isFalse);
+    expect(state.lessonListeningComplete, isFalse);
+  });
+
+  test('placement opens its start lesson without passing earlier ones', () {
+    final state = AppState();
+    state.setPlacementStartLesson('a0-02');
+
+    expect(state.activeLessonId, 'a0-02');
+    expect(state.isLessonUnlocked('a0-01'), isTrue);
+    expect(state.isLessonUnlocked('a0-02'), isTrue);
+    expect(state.isLessonUnlocked('a0-03'), isFalse);
+    expect(state.completedLessonIds, isEmpty);
+
+    finishActiveLesson(state);
+    expect(state.activeLessonId, 'a0-03');
+  });
+
+  test('after the last lesson the learner is sent to unfinished lessons', () {
+    final state = AppState();
+    state.setPlacementStartLesson('a0-02');
+    for (var index = 1; index < a0SeedLessons.length; index++) {
+      final lesson = a0SeedLessons[index];
+      state.openLesson(lesson.id);
+      for (var segment = 0; segment < lesson.segments.length; segment++) {
+        state.completeSegment(lesson.id, segment);
+      }
+      finishActiveLesson(state);
+    }
+    expect(state.activeLessonId, 'a0-01');
+    expect(state.allLessonsComplete, isFalse);
+
+    finishActiveLesson(state);
+    expect(state.allLessonsComplete, isTrue);
+    expect(state.a0AssessmentReady, isFalse);
+    expect(state.nextAssessmentPackId, 'A0-E1');
+  });
+
   test(
     'a passed assessment skill remains valid during the seven-day retest window',
     () {

kouyu_english/test/deepseek_thinking_test.dart

@@ -43,6 +43,7 @@ void main() {
     final body = await captureBody('https://api.deepseek.com');
 
     expect(body['thinking'], {'type': 'disabled'});
+    expect(body['response_format'], {'type': 'json_object'});
     expect(body.containsKey('reasoning_effort'), isFalse);
     expect(body['max_tokens'], 200);
   });
@@ -51,6 +52,9 @@ void main() {
     final body = await captureBody('https://api.deepseek.com/v1/responses');
 
     expect(body['reasoning'], {'effort': 'none'});
+    expect(body['text'], {
+      'format': {'type': 'json_object'},
+    });
     expect(body.containsKey('reasoning_effort'), isFalse);
     expect(body.containsKey('thinking'), isFalse);
   });
@@ -59,6 +63,48 @@ void main() {
     final body = await captureBody('https://example.test/v1');
 
     expect(body.containsKey('thinking'), isFalse);
+    expect(body.containsKey('response_format'), isFalse);
     expect(body['reasoning_effort'], 'low');
   });
+
+  test('dialogue history replays earlier AI lines as JSON', () async {
+    AiService.instance.setFallbackApiKey('test-key');
+    List<dynamic>? messages;
+    final reply = await http.runWithClient(
+      () => AiService.instance.dialogueReply(
+        provider: AiProviderType.compatible,
+        endpoint: 'https://api.deepseek.com',
+        model: 'deepseek-flash',
+        aiGoal: 'Ask where the learner is from.',
+        learnerTask: 'say where they are from',
+        history: const [
+          {'role': 'assistant', 'content': "Hi! What's your name?"},
+          {'role': 'user', 'content': 'My name is Alex.'},
+        ],
+      ),
+      () => MockClient((request) async {
+        final body = jsonDecode(request.body) as Map<String, dynamic>;
+        messages = body['messages'] as List<dynamic>;
+        return http.Response(
+          jsonEncode({
+            'choices': [
+              {
+                'message': {'content': '{"reply":"Where are you from?"}'},
+              },
+            ],
+          }),
+          200,
+          headers: {'content-type': 'application/json; charset=utf-8'},
+        );
+      }),
+    );
+
+    expect(reply?.reply, 'Where are you from?');
+    expect(messages, hasLength(3));
+    expect(messages![0]['role'], 'system');
+    expect(jsonDecode(messages![1]['content'] as String), {
+      'reply': "Hi! What's your name?",
+    });
+    expect(messages![2], {'role': 'user', 'content': 'My name is Alex.'});
+  });
 }

kouyu_english/test/dialogue_task_test.dart

@@ -28,7 +28,10 @@ void main() {
         );
       }
       expect(a0MeetDialogue.taskLabels.length, a0MeetDialogue.prompts.length);
-      expect(a0MeetDialogue.requiredTerms.length, a0MeetDialogue.prompts.length);
+      expect(
+        a0MeetDialogue.requiredTerms.length,
+        a0MeetDialogue.prompts.length,
+      );
     });
 
     test('示范答案能通过对应回合的校验', () {
@@ -46,37 +49,101 @@ void main() {
 
     test('跑题回答不再因为关键词沾边而通过', () {
       // 旧实现用 text.contains('it')，下面这些句子全部会被判为完成任务。
-      expect(matchesDialogueStage(a0Dialogues['a0-05']!, 0, 'I did it.'), isFalse);
-      expect(matchesDialogueStage(a0Dialogues['a0-08']!, 0, 'It is good.'), isFalse);
-      expect(matchesDialogueStage(a0Dialogues['a0-09']!, 2, 'I like tea.'), isFalse);
+      expect(
+        matchesDialogueStage(a0Dialogues['a0-05']!, 0, 'I did it.'),
+        isFalse,
+      );
+      expect(
+        matchesDialogueStage(a0Dialogues['a0-08']!, 0, 'It is good.'),
+        isFalse,
+      );
+      expect(
+        matchesDialogueStage(a0Dialogues['a0-09']!, 2, 'I like tea.'),
+        isFalse,
+      );
       expect(matchesDialogueStage(a0MeetDialogue, 0, 'Hello.'), isFalse);
       expect(matchesDialogueStage(a0MeetDialogue, 1, 'I am good.'), isFalse);
     });
 
     test('自由场景接受同样正确的其他说法', () {
       // 旧正则只认 good/okay/tired，也不认 my name's。
-      expect(matchesDialogueStage(a0MeetDialogue, 0, "My name's Shen."), isTrue);
+      expect(
+        matchesDialogueStage(a0MeetDialogue, 0, "My name's Shen."),
+        isTrue,
+      );
       expect(matchesDialogueStage(a0MeetDialogue, 0, 'I am Shen.'), isTrue);
-      expect(matchesDialogueStage(a0MeetDialogue, 2, "I'm fine, thanks."), isTrue);
+      expect(
+        matchesDialogueStage(a0MeetDialogue, 2, "I'm fine, thanks."),
+        isTrue,
+      );
       expect(matchesDialogueStage(a0MeetDialogue, 2, 'I am great!'), isTrue);
-      expect(matchesDialogueStage(a0MeetDialogue, 3, 'Where are you from?'), isTrue);
-      expect(matchesDialogueStage(a0MeetDialogue, 3, 'Do you like tea?'), isTrue);
+      expect(
+        matchesDialogueStage(a0MeetDialogue, 3, 'Where are you from?'),
+        isTrue,
+      );
+      expect(
+        matchesDialogueStage(a0MeetDialogue, 3, 'Do you like tea?'),
+        isTrue,
+      );
     });
 
     test('只写半句不算完成任务', () {
       expect(matchesDialogueStage(a0MeetDialogue, 0, "I'm"), isFalse);
-      expect(matchesDialogueStage(a0Dialogues['a0-04']!, 0, 'My number is'), isFalse);
       expect(
-        matchesDialogueStage(a0Dialogues['a0-04']!, 0, 'My number is one-three-eight.'),
+        matchesDialogueStage(a0Dialogues['a0-04']!, 0, 'My number is'),
+        isFalse,
+      );
+      expect(
+        matchesDialogueStage(
+          a0Dialogues['a0-04']!,
+          0,
+          'My number is one-three-eight.',
+        ),
         isTrue,
       );
     });
 
     test('拼读和数字这类结构化要求可以识别', () {
       expect(matchesDialogueStage(a0Dialogues['a0-02']!, 1, 'S-H-E-N'), isTrue);
-      expect(matchesDialogueStage(a0Dialogues['a0-02']!, 1, 'Shen'), isFalse);
-      expect(matchesDialogueStage(a0Dialogues['a0-08']!, 2, "It's three o'clock."), isTrue);
-      expect(matchesDialogueStage(a0Dialogues['a0-08']!, 2, "It's Monday."), isFalse);
+    });
+
+    test('拼读忽略大小写和连字符', () {
+      final spelling = a0Dialogues['a0-02']!;
+      for (final answer in [
+        'A-A-A',
+        'aaa',
+        'AAA',
+        'a-a-a',
+        'A - A - A',
+        'a a a',
+        'Shen',
+        'S-H-E-N.',
+        'She-n',
+        'L-I',
+        'Li',
+        'My name is Alex. A-L-E-X.',
+      ]) {
+        expect(
+          matchesDialogueStage(spelling, 1, answer),
+          isTrue,
+          reason: answer,
+        );
+      }
+      for (final answer in ['a', 'My name is Alex.', '123', '---']) {
+        expect(
+          matchesDialogueStage(spelling, 1, answer),
+          isFalse,
+          reason: answer,
+        );
+      }
+      expect(
+        matchesDialogueStage(a0Dialogues['a0-08']!, 2, "It's three o'clock."),
+        isTrue,
+      );
+      expect(
+        matchesDialogueStage(a0Dialogues['a0-08']!, 2, "It's Monday."),
+        isFalse,
+      );
     });
 
     test('任务标签可用于提示和总结', () {
@@ -86,7 +153,11 @@ void main() {
 
     test('输入校验忽略多余空格与大小写', () {
       expect(
-        matchesDialogueStage(a0MeetDialogue, 0, "   MY    NAME    IS    SHEN   "),
+        matchesDialogueStage(
+          a0MeetDialogue,
+          0,
+          "   MY    NAME    IS    SHEN   ",
+        ),
         isTrue,
       );
       expect(
@@ -94,11 +165,19 @@ void main() {
         isTrue,
       );
       expect(
-        matchesDialogueStage(a0Dialogues["a0-04"]!, 0, "MY   NUMBER   IS   ONE-THREE-EIGHT"),
+        matchesDialogueStage(
+          a0Dialogues["a0-04"]!,
+          0,
+          "MY   NUMBER   IS   ONE-THREE-EIGHT",
+        ),
         isTrue,
       );
       expect(
-        matchesDialogueStage(a0Dialogues["a0-08"]!, 2, "IT'S    THREE    O'CLOCK"),
+        matchesDialogueStage(
+          a0Dialogues["a0-08"]!,
+          2,
+          "IT'S    THREE    O'CLOCK",
+        ),
         isTrue,
       );
     });
@@ -110,7 +189,10 @@ void main() {
       expect(later.length, greaterThan(first.length));
       expect(first.every(later.contains), isTrue);
       expect(later.length, lessThanOrEqualTo(allTaughtLanguage.length));
-      expect(first.any((word) => word.toLowerCase().contains('coffee')), isFalse);
+      expect(
+        first.any((word) => word.toLowerCase().contains('coffee')),
+        isFalse,
+      );
     });
   });
 }

kouyu_english/test/placement_and_scene_test.dart

@@ -0,0 +1,92 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:kouyu_english/core/app_state.dart';
+import 'package:kouyu_english/features/dialogue/dialogue_flow.dart';
+import 'package:kouyu_english/features/onboarding/onboarding_pages.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  setUp(() {
+    SharedPreferences.setMockInitialValues({});
+  });
+
+  testWidgets('three-question placement suggests a starting lesson', (
+    tester,
+  ) async {
+    final state = AppState();
+    var started = false;
+    await tester.pumpWidget(
+      MaterialApp(
+        home: PlacementPage(state: state, onStart: () => started = true),
+      ),
+    );
+
+    await tester.tap(find.text('开始 3 分钟定位'));
+    await tester.pumpAndSettle();
+    expect(find.text('定位 · 1 / 3'), findsOneWidget);
+    await tester.tap(find.text('你好，我叫 Mia，很高兴认识你。'));
+    await tester.pump();
+    await tester.tap(find.text('下一题'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('定位 · 2 / 3'), findsOneWidget);
+    await tester.tap(find.text('现在不方便开口，跳过'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('定位 · 3 / 3'), findsOneWidget);
+    await tester.enterText(find.byType(TextField), 'My name is Mia.');
+    await tester.tap(find.text('查看建议'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('建议从 A0 第 2 课开始'), findsOneWidget);
+    expect(find.text('从更简单内容开始'), findsOneWidget);
+    await tester.tap(find.text('开始今天学习'));
+    await tester.pump();
+
+    expect(started, isTrue);
+    expect(state.activeLessonId, 'a0-02');
+    expect(state.placementStartLessonId, 'a0-02');
+    expect(state.completedLessonIds, isEmpty);
+  });
+
+  testWidgets('an unanswered placement starts from lesson one', (tester) async {
+    final state = AppState();
+    await tester.pumpWidget(
+      MaterialApp(
+        home: PlacementPage(state: state, onStart: () {}),
+      ),
+    );
+
+    await tester.tap(find.text('开始 3 分钟定位'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('听不懂，下一题'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('我读完了'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('还不会说，查看建议'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('建议从 A0 第 1 课开始'), findsOneWidget);
+    expect(find.text('从更简单内容开始'), findsNothing);
+  });
+
+  testWidgets('scene page lists open and locked scenes', (tester) async {
+    final state = AppState()
+      ..completedLessonIds.addAll(['a0-01', 'a0-02', 'a0-03', 'a0-04']);
+    String? startedScene;
+    await tester.pumpWidget(
+      MaterialApp(
+        home: DialogueScenePage(
+          state: state,
+          onStart: (id) => startedScene = id,
+        ),
+      ),
+    );
+
+    expect(find.text('初次见面'), findsOneWidget);
+    expect(find.text('留个电话'), findsOneWidget);
+    expect(find.text('A0 · 学完第 7 课后开放'), findsOneWidget);
+    await tester.tap(find.widgetWithText(FilledButton, '开始对话').first);
+    expect(startedScene, isNotNull);
+  });
+}