diff --git a/DataIO.js.html b/DataIO.js.html
new file mode 100644
index 0000000..a36c746
--- /dev/null
+++ b/DataIO.js.html
@@ -0,0 +1,216 @@
+<script>
+/**
+ * DataIO.js.html — Data input/output methods (server sync, versioning, local persistence)
+ *
+ * Part of #129 Phase 1 (PR5/7): IIFE-wrapped domain separation.
+ * These methods handle version history loading, server data synchronisation,
+ * local data persistence (localStorage), and conflict resolution.
+ *
+ * Load order: after JavaScript.html + UtilityFunctions.js + LockManager.js +
+ * DataCollection.js (which creates window.App, utility, lock, and collection
+ * methods), before App.init() trigger.
+ *
+ * Dependencies:
+ *   - DataCollection.js (App.getAllTags, App.ensureDataIds)
+ *   - ScheduleManager (App.loadInitialSchedules, App.loadSchedule,
+ *     App.saveSchedulesToLocal — circular, resolved via App.xxx at call time)
+ *   - ServerApi.call (external module)
+ *   - AppConfig (STATUS, APP_VERSION)
+ *   - AppElements (versionHistorySelect, versionHistoryModal)
+ *   - localStorage
+ */
+(function(App) {
+
+  // --- Version history ---
+
+  App.loadVersions = async function() {
+    const select = AppElements.versionHistorySelect;
+    select.innerHTML = '<option>正在載入中...</option>';
+    App.ui.showNotification('正在獲取版本列表...', 'info');
+
+    try {
+      const versions = await ServerApi.call('getVersions', App.activeScheduleId);
+      if (!versions || versions.error) throw new Error(versions ? versions.error : '未知錯誤');
+
+      select.innerHTML = '';
+      if (versions.length > 0) {
+        versions.forEach(v => {
+          const option = document.createElement('option');
+          option.value = v.id;
+          option.textContent = `${new Date(v.id).toLocaleString()} by ${App.getShortUserName(v.user)}`;
+          select.appendChild(option);
+        });
+        App.ui.showNotification('版本列表已更新', 'success');
+      } else {
+        select.innerHTML = '<option>此課表沒有歷史紀錄</option>';
+      }
+    } catch (error) {
+      App.ui.showNotification('獲取版本列表失敗: ' + error.message, 'error');
+      select.innerHTML = '<option>獲取失敗</option>';
+    }
+  };
+
+  App.handleLoadVersion = async function() {
+    const select = AppElements.versionHistorySelect;
+    const versionId = select.value;
+    if (!versionId || select.options[select.selectedIndex].text === '沒有歷史紀錄') {
+      App.ui.showNotification('請選擇一個有效的版本', 'error');
+      return;
+    }
+    if (App.isDirty && !await App.modals.showConfirm(`您有未儲存的變更，確定要讀取歷史版本並覆蓋當前的課表嗎？`)) {
+      return;
+    }
+    AppElements.versionHistoryModal.style.display = 'none';
+    App.ui.showLoading('正在讀取歷史版本...');
+
+    try {
+      const data = await ServerApi.call('getVersionData', versionId);
+      if (!data || !data.success) throw new Error(data ? data.error : '未知錯誤');
+
+      const currentSchedule = App.schedules[App.activeScheduleId];
+      currentSchedule.data.classrooms = data.classrooms || [];
+      currentSchedule.data.scheduleData = App.ensureDataIds(data.scheduleData || {});
+      currentSchedule.data.tags = data.tags || [];
+
+      App.saveSchedulesToLocal();
+      App.loadSchedule(App.activeScheduleId);
+
+      App.ui.updateSyncStatus(AppConfig.STATUS.OFFLINE, App.lastCloudModifiedTime);
+      App.ui.showNotification(`已在本地載入版本: ${new Date(data.versionId).toLocaleString()}`, 'info');
+    } catch (error) {
+      App.ui.showNotification('讀取版本失敗: ' + error.message, 'error');
+    } finally {
+      App.ui.hideLoading();
+    }
+  };
+
+  // --- Local persistence ---
+
+  App.saveDataToLocal = function() {
+    try {
+      // Sync the current working data back to the main schedules object
+      if (App.activeScheduleId && App.schedules[App.activeScheduleId]) {
+        const activeSchedule = App.schedules[App.activeScheduleId];
+        if (activeSchedule.data) {
+          activeSchedule.data.scheduleData = App.scheduleData;
+          activeSchedule.data.classrooms = App.classrooms;
+          activeSchedule.data.tags = App.getAllTags(); // Also update the tags list for consistency
+        }
+      }
+
+      // After saving, the list of all tags might have changed.
+      // We need to re-initialize the tag filter to get the fresh list, while preserving the current value.
+      let currentFilterValue = [];
+      if (App.tagFilterTagify) {
+        currentFilterValue = App.tagFilterTagify.value.map(tag => tag.value);
+      }
+
+      App.tags = App.getAllTags(); // Recalculate all tags from current data
+      App.ui.initializeTagFilter(); // This will destroy and recreate the Tagify instance
+
+      if (App.tagFilterTagify && currentFilterValue.length > 0) {
+        // Restore the previous value without triggering 'add' events.
+        // loadOriginalValues will only add valid tags from the new whitelist.
+        App.tagFilterTagify.loadOriginalValues(currentFilterValue);
+      }
+
+      App.saveSchedulesToLocal();
+      localStorage.setItem('activeScheduleId', App.activeScheduleId);
+      localStorage.setItem('app_version', AppConfig.APP_VERSION);
+      if (App.lastSyncTime) localStorage.setItem('lastSyncTime', App.lastSyncTime.toISOString());
+    } catch (e) {
+      console.error("保存數據到本地失敗:", e);
+      App.ui.showNotification("保存數據失敗，可能是存儲空間不足", "error");
+    }
+  };
+
+  // --- Server communication ---
+
+  App.loadDataFromServer = async function() {
+    if (App.isConnecting) {
+      App.ui.showNotification("A sync operation is already in progress.", "info");
+      return;
+    }
+    App.isConnecting = true;
+    App.ui.manageLoadingState('start', { message: '正在從雲端同步資料...' });
+
+    try {
+      const result = await ServerApi.call('getData');
+      if (!result || result.error) throw new Error(result ? result.error : '從服務器獲取的數據為空');
+
+      App.schedules = result.schedules || {};
+      App.scheduleLastModified = {}; // Clear old timestamps
+      for (const id in App.schedules) {
+        if (App.schedules[id].lastModified) {
+          App.scheduleLastModified[id] = App.schedules[id].lastModified;
+          // The timestamp is sensitive and only needed for the save operation,
+          // let's not keep it in the main data object that gets saved to local storage.
+          delete App.schedules[id].lastModified;
+        }
+      }
+
+      App.activeMetadataTimestamp = result.metadataTimestamp;
+
+      // After fetching data, the client decides which schedule to load.
+      App.loadInitialSchedules();
+
+      App.lastSyncTime = new Date();
+      App.saveSchedulesToLocal();
+      App.ui.manageLoadingState('end', { success: true, message: '從雲端讀取數據成功！' });
+
+    } catch (error) {
+      App.ui.manageLoadingState('end', { success: false, message: `讀取失敗: ${error.message}` });
+    } finally {
+      App.isConnecting = false;
+    }
+  };
+
+  App.saveDataToServer = async function() {
+    if (App.isConnecting) return;
+    App.isConnecting = true;
+    App.ui.manageLoadingState('start', { message: '正在檢查版本並儲存至雲端...' });
+
+    try {
+      const currentScheduleTimestamp = App.scheduleLastModified[App.activeScheduleId];
+      if (!currentScheduleTimestamp) {
+        throw new Error("找不到當前課表的版本資訊，無法儲存。請嘗試重新載入。");
+      }
+
+      const dataToSend = {
+        scheduleId: App.activeScheduleId,
+        lastModified: currentScheduleTimestamp, // *** STEP 4: Attach the specific timestamp
+        scheduleData: {
+          classrooms: App.classrooms,
+          scheduleData: App.scheduleData,
+          tags: App.tags
+        }
+      };
+
+      const saveResult = await ServerApi.call('saveData', dataToSend);
+
+      // *** STEP 4: Handle new conflict error
+      if (saveResult && saveResult.conflict) {
+        App.modals.showConfirm(saveResult.error, true); // textContent is XSS-safe; escapeHtml removed to prevent double-escaping
+        App.ui.manageLoadingState('end', { success: false, isConflict: true });
+        return;
+      }
+
+      if (!saveResult || !saveResult.success) {
+        throw new Error(saveResult?.error || '儲存時發生未知錯誤');
+      }
+
+      App.lastSyncTime = new Date();
+      App.scheduleLastModified[App.activeScheduleId] = saveResult.lastModified;
+      App.historyModule.updateCleanSnapshot();
+      App.historyModule.checkDirty();
+      App.ui.manageLoadingState('end', { success: true, message: '數據已成功儲存到雲端！' });
+
+    } catch (error) {
+      App.ui.manageLoadingState('end', { success: false, message: `數據儲存失敗: ${error.message}` });
+    } finally {
+      App.isConnecting = false;
+    }
+  };
+
+})(App);
+</script>
diff --git a/Index.html b/Index.html
index ebf4441..bba72d9 100644
--- a/Index.html
+++ b/Index.html
@@ -477,6 +477,7 @@ <h2 class="text-2xl font-bold mb-6 text-center text-purple-800">PDF 下載選項
     <?!= HtmlService.createHtmlOutputFromFile('LockManager.js').getContent(); ?>
     <?!= HtmlService.createHtmlOutputFromFile('DataCollection.js').getContent(); ?>
     <?!= HtmlService.createHtmlOutputFromFile('FilterEngine.js').getContent(); ?>
+    <?!= HtmlService.createHtmlOutputFromFile('DataIO.js').getContent(); ?>
     <script>App.init();</script>
 </body>
 </html>
diff --git a/JavaScript.html b/JavaScript.html
index f57e48d..d73089b 100644
--- a/JavaScript.html
+++ b/JavaScript.html
@@ -431,191 +431,12 @@
                 this.ui.updateClearAllFiltersButtonVisibility();
             },
 
-            // --- API COMMUNICATION ---
-            loadVersions: async function () {
-                const select = AppElements.versionHistorySelect;
-                select.innerHTML = '<option>正在載入中...</option>';
-                this.ui.showNotification('正在獲取版本列表...', 'info');
 
-                try {
-                    const versions = await ServerApi.call('getVersions', this.activeScheduleId);
-                    if (!versions || versions.error) throw new Error(versions ? versions.error : '未知錯誤');
-
-                    select.innerHTML = '';
-                    if (versions.length > 0) {
-                        versions.forEach(v => {
-                            const option = document.createElement('option');
-                            option.value = v.id;
-                            option.textContent = `${new Date(v.id).toLocaleString()} by ${this.getShortUserName(v.user)}`;
-                            select.appendChild(option);
-                        });
-                        this.ui.showNotification('版本列表已更新', 'success');
-                    } else {
-                        select.innerHTML = '<option>此課表沒有歷史紀錄</option>';
-                    }
-                } catch (error) {
-                    this.ui.showNotification('獲取版本列表失敗: ' + error.message, 'error');
-                    select.innerHTML = '<option>獲取失敗</option>';
-                }
-            },
-
-            handleLoadVersion: async function () {
-                const select = AppElements.versionHistorySelect;
-                const versionId = select.value;
-                if (!versionId || select.options[select.selectedIndex].text === '沒有歷史紀錄') {
-                    this.ui.showNotification('請選擇一個有效的版本', 'error');
-                    return;
-                }
-                if (this.isDirty && !await this.modals.showConfirm(`您有未儲存的變更，確定要讀取歷史版本並覆蓋當前的課表嗎？`)) {
-                    return;
-                }
-                AppElements.versionHistoryModal.style.display = 'none';
-                this.ui.showLoading('正在讀取歷史版本...');
-
-                try {
-                    const data = await ServerApi.call('getVersionData', versionId);
-                    if (!data || !data.success) throw new Error(data ? data.error : '未知錯誤');
-
-                    const currentSchedule = this.schedules[this.activeScheduleId];
-                    currentSchedule.data.classrooms = data.classrooms || [];
-                    currentSchedule.data.scheduleData = this.ensureDataIds(data.scheduleData || {});
-                    currentSchedule.data.tags = data.tags || [];
-
-                    this.saveSchedulesToLocal();
-                    this.loadSchedule(this.activeScheduleId);
-
-                    this.ui.updateSyncStatus(AppConfig.STATUS.OFFLINE, this.lastCloudModifiedTime);
-                    this.ui.showNotification(`已在本地載入版本: ${new Date(data.versionId).toLocaleString()}`, 'info');
-                } catch (error) {
-                    this.ui.showNotification('讀取版本失敗: ' + error.message, 'error');
-                } finally {
-                    this.ui.hideLoading();
-                }
-            },
-
-            saveDataToLocal: function () {
-                try {
-                    // Sync the current working data back to the main schedules object
-                    if (this.activeScheduleId && this.schedules[this.activeScheduleId]) {
-                        const activeSchedule = this.schedules[this.activeScheduleId];
-                        if (activeSchedule.data) {
-                            activeSchedule.data.scheduleData = this.scheduleData;
-                            activeSchedule.data.classrooms = this.classrooms;
-                            activeSchedule.data.tags = this.getAllTags(); // Also update the tags list for consistency
-                        }
-                    }
-
-                    // After saving, the list of all tags might have changed.
-                    // We need to re-initialize the tag filter to get the fresh list, while preserving the current value.
-                    let currentFilterValue = [];
-                    if (this.tagFilterTagify) {
-                        currentFilterValue = this.tagFilterTagify.value.map(tag => tag.value);
-                    }
-
-                    this.tags = this.getAllTags(); // Recalculate all tags from current data
-                    this.ui.initializeTagFilter(); // This will destroy and recreate the Tagify instance
-
-                    if (this.tagFilterTagify && currentFilterValue.length > 0) {
-                        // Restore the previous value without triggering 'add' events.
-                        // loadOriginalValues will only add valid tags from the new whitelist.
-                        this.tagFilterTagify.loadOriginalValues(currentFilterValue);
-                    }
-
-                    this.saveSchedulesToLocal();
-                    localStorage.setItem('activeScheduleId', this.activeScheduleId);
-                    localStorage.setItem('app_version', AppConfig.APP_VERSION);
-                    if (this.lastSyncTime) localStorage.setItem('lastSyncTime', this.lastSyncTime.toISOString());
-                } catch (e) {
-                    console.error("保存數據到本地失敗:", e);
-                    this.ui.showNotification("保存數據失敗，可能是存儲空間不足", "error");
-                }
-            },
-
-            loadDataFromServer: async function () {
-                if (this.isConnecting) {
-                    this.ui.showNotification("A sync operation is already in progress.", "info");
-                    return;
-                }
-                this.isConnecting = true;
-                this.ui.manageLoadingState('start', { message: '正在從雲端同步資料...' });
-
-                try {
-                    const result = await ServerApi.call('getData');
-                    if (!result || result.error) throw new Error(result ? result.error : '從服務器獲取的數據為空');
-
-                    this.schedules = result.schedules || {};
-                    this.scheduleLastModified = {}; // Clear old timestamps
-                    for (const id in this.schedules) {
-                        if (this.schedules[id].lastModified) {
-                            this.scheduleLastModified[id] = this.schedules[id].lastModified;
-                            // The timestamp is sensitive and only needed for the save operation,
-                            // let's not keep it in the main data object that gets saved to local storage.
-                            delete this.schedules[id].lastModified;
-                        }
-                    }
-
-                    this.activeMetadataTimestamp = result.metadataTimestamp;
-
-                    // After fetching data, the client decides which schedule to load.
-                    this.loadInitialSchedules();
-
-                    this.lastSyncTime = new Date();
-                    this.saveSchedulesToLocal();
-                    this.ui.manageLoadingState('end', { success: true, message: '從雲端讀取數據成功！' });
-
-                } catch (error) {
-                    this.ui.manageLoadingState('end', { success: false, message: `讀取失敗: ${error.message}` });
-                } finally {
-                    this.isConnecting = false;
-                }
-            },
-
-            saveDataToServer: async function () {
-                if (this.isConnecting) return;
-                this.isConnecting = true;
-                this.ui.manageLoadingState('start', { message: '正在檢查版本並儲存至雲端...' });
-
-                try {
-                    const currentScheduleTimestamp = this.scheduleLastModified[this.activeScheduleId];
-                    if (!currentScheduleTimestamp) {
-                        throw new Error("找不到當前課表的版本資訊，無法儲存。請嘗試重新載入。");
-                    }
-
-                    const dataToSend = {
-                        scheduleId: this.activeScheduleId,
-                        lastModified: currentScheduleTimestamp, // *** STEP 4: Attach the specific timestamp
-                        scheduleData: {
-                            classrooms: this.classrooms,
-                            scheduleData: this.scheduleData,
-                            tags: this.tags
-                        }
-                    };
-
-                    const saveResult = await ServerApi.call('saveData', dataToSend);
-
-                    // *** STEP 4: Handle new conflict error
-                    if (saveResult && saveResult.conflict) {
-                        this.modals.showConfirm(saveResult.error, true); // textContent is XSS-safe; escapeHtml removed to prevent double-escaping
-                        this.ui.manageLoadingState('end', { success: false, isConflict: true });
-                        return;
-                    }
-
-                    if (!saveResult || !saveResult.success) {
-                        throw new Error(saveResult?.error || '儲存時發生未知錯誤');
-                    }
-
-                    this.lastSyncTime = new Date();
-                    this.scheduleLastModified[this.activeScheduleId] = saveResult.lastModified;
-                    this.historyModule.updateCleanSnapshot();
-                    this.historyModule.checkDirty();
-                    this.ui.manageLoadingState('end', { success: true, message: '數據已成功儲存到雲端！' });
-
-                } catch (error) {
-                    this.ui.manageLoadingState('end', { success: false, message: `數據儲存失敗: ${error.message}` });
-                } finally {
-                    this.isConnecting = false;
-                }
-            },
+            // loadVersions — moved to DataIO.js.html (Phase 1 PR5)
+            // handleLoadVersion — moved to DataIO.js.html (Phase 1 PR5)
+            // saveDataToLocal — moved to DataIO.js.html (Phase 1 PR5)
+            // loadDataFromServer — moved to DataIO.js.html (Phase 1 PR5)
+            // saveDataToServer — moved to DataIO.js.html (Phase 1 PR5)
 
             // findNextUpcomingClasses — moved to DataCollection.js.html (Phase 1 PR3)
 
diff --git a/tests/helpers/sourceAnalysis.js b/tests/helpers/sourceAnalysis.js
index e7f914b..6af4f2e 100644
--- a/tests/helpers/sourceAnalysis.js
+++ b/tests/helpers/sourceAnalysis.js
@@ -21,7 +21,16 @@ export function extractMethodBody(source, methodName) {
   const declPattern = new RegExp(
     `${methodName}\\s*:\\s*(?:async\\s+)?function\\s*\\([^)]*\\)\\s*\\{`
   );
-  const match = declPattern.exec(source);
+  let match = declPattern.exec(source);
+
+  // Also try IIFE-extracted pattern: App.methodName = (async)? function(...) {
+  if (!match) {
+    const iifePattern = new RegExp(
+      `App\\.${methodName}\\s*=\\s*(?:async\\s+)?function\\s*\\([^)]*\\)\\s*\\{`
+    );
+    match = iifePattern.exec(source);
+  }
+
   if (!match) return null;
 
   const startIdx = match.index + match[0].length;
diff --git a/tests/unit/appWiringContracts.test.js b/tests/unit/appWiringContracts.test.js
index b8017ad..ddb96e7 100644
--- a/tests/unit/appWiringContracts.test.js
+++ b/tests/unit/appWiringContracts.test.js
@@ -61,7 +61,7 @@ const privateMethods = extractPrivateMethods(jsHtmlSource);
  */
 const EXTRACTED_TO_LIB = new Set([
   // stateHelpers.js
-  'handleEditClassroom', 'saveDataToServer',
+  'handleEditClassroom',
   // interactionHelpers.js (handleDrop → applyDrop)
   'handleDrop',
   // appLifecycleHelpers.js (new — this wave)
@@ -81,10 +81,6 @@ const NOT_EXTRACTABLE = new Set([
   'handleScheduleListClick',      // DOM event delegation + ServerApi + modals
   'handleScheduleSelectChange',   // DOM event + modal confirm + state (aggregateScheduleData already extracted)
   'applyTagFilters',              // Tagify instance + modal confirm + DOM
-  'loadVersions',                 // DOM + ServerApi
-  'handleLoadVersion',            // DOM + ServerApi + state
-  'saveDataToLocal',              // localStorage + Tagify + DOM (core sync logic extracted as processServerLoadResult)
-  'loadDataFromServer',           // ServerApi + state orchestration (result processing extracted)
   'isCurrentUserAdmin',           // Global var IS_ADMIN (trivial, 1 line)
   'printScheduleToPdf',           // jsPDF + DOM + ServerApi (massively coupled)
 ]);
@@ -122,6 +118,9 @@ const IIFE_EXTRACTED = new Set([
   'filterDataByTags', 'filterDataByActiveFilters',
   // FilterEngine.js.html (PR4) — private helpers also IIFE-extracted
   '_filterScheduleData',
+  // DataIO.js.html (PR5)
+  'loadVersions', 'handleLoadVersion', 'saveDataToLocal',
+  'loadDataFromServer', 'saveDataToServer',
 ]);
 
 // ─── Tests ─────────────────────────────────────────────────────────────────
@@ -134,8 +133,8 @@ describe('JavaScript.html App method wiring contracts (#116)', () => {
   it('should have expected total App method count', () => {
     // All public methods (excluding underscore-prefixed private helpers)
     const publicMethods = appMethods.filter(m => !m.startsWith('_'));
-    // 48 original - 7 PR1 - 4 PR2 public - 11 PR3 public - 7 PR4 public = 19 remaining in JavaScript.html
-    expect(publicMethods.length).toBe(19);
+    // 48 original - 7 PR1 - 4 PR2 public - 11 PR3 public - 7 PR4 public - 5 PR5 = 14 remaining in JavaScript.html
+    expect(publicMethods.length).toBe(14);
   });
 
   it('every public App method should be classified (extracted OR not-extractable)', () => {
diff --git a/tests/unit/asyncMethodsWiring.test.js b/tests/unit/asyncMethodsWiring.test.js
index fb83e98..62a70dd 100644
--- a/tests/unit/asyncMethodsWiring.test.js
+++ b/tests/unit/asyncMethodsWiring.test.js
@@ -22,6 +22,12 @@ const jsHtmlSource = readFileSync(
   'utf-8'
 );
 
+// DataIO methods moved to IIFE module (Phase 1 PR5)
+const dataIOSource = readFileSync(
+  resolve(import.meta.dirname, '../../DataIO.js.html'),
+  'utf-8'
+);
+
 const gasSource = readFileSync(
   resolve(import.meta.dirname, '../../程式碼.js'),
   'utf-8'
@@ -54,30 +60,47 @@ const KNOWN_BACKEND_FUNCTIONS = extractGasFunctionNames(gasSource);
  * Note: applyTagFilters has NO ServerApi calls (pure frontend).
  * handleScheduleSelectChange has NO direct ServerApi calls (delegates to loadSchedule/loadDataFromServer).
  */
-const ASYNC_METHOD_WIRING = [
+// Methods in JavaScript.html
+const JS_HTML_ASYNC_METHODS = [
   ['handleAddSchedule', 227, ['addSchedule']],
   ['handleScheduleListClick', 259, ['updateScheduleMetadata', 'deleteSchedule', 'copySchedule']],
   ['handleScheduleSelectChange', 359, []], // No direct ServerApi.call — delegates to loadSchedule
   ['applyTagFilters', 433, []], // Pure frontend, no ServerApi
-  ['loadVersions', 505, ['getVersions']],
-  ['handleLoadVersion', 532, ['getVersionData']],
-  ['loadDataFromServer', 604, ['getData']],
-  ['saveDataToServer', 643, ['saveData']],
   ['printScheduleToPdf', 1117, ['getFontBase64FromDrive']],
 ];
 
+// Methods moved to DataIO.js.html (Phase 1 PR5)
+const DATA_IO_ASYNC_METHODS = [
+  ['loadVersions', 0, ['getVersions']],
+  ['handleLoadVersion', 0, ['getVersionData']],
+  ['loadDataFromServer', 0, ['getData']],
+  ['saveDataToServer', 0, ['saveData']],
+];
+
+const ASYNC_METHOD_WIRING = [...JS_HTML_ASYNC_METHODS, ...DATA_IO_ASYNC_METHODS];
+
 // ─── Helpers ─────────────────────────────────────────────────────────────
 
 /**
- * Extract the body of an async method from JavaScript.html source.
- * Searches for `methodName: async function` and captures the balanced braces body.
+ * Extract the body of an async method from source.
+ * Supports both object literal (`methodName: async function`) and
+ * IIFE-extracted (`App.methodName = async function`) patterns.
  */
 function extractMethodBody(source, methodName) {
-  // Match the method declaration pattern in the App object literal
+  // Try object literal pattern first
   const declPattern = new RegExp(
     `${methodName}\\s*:\\s*async\\s+function\\s*\\([^)]*\\)\\s*\\{`
   );
-  const match = declPattern.exec(source);
+  let match = declPattern.exec(source);
+
+  // Try IIFE-extracted pattern: App.methodName = async function(...) {
+  if (!match) {
+    const iifePattern = new RegExp(
+      `App\\.${methodName}\\s*=\\s*async\\s+function\\s*\\([^)]*\\)\\s*\\{`
+    );
+    match = iifePattern.exec(source);
+  }
+
   if (!match) return null;
 
   // Find the balanced closing brace
@@ -113,9 +136,9 @@ describe('Async App Methods — Wiring Smoke Tests (Static Analysis)', () => {
 
   // ─── 1. Method existence in source ────────────────────────────────────
 
-  describe('all 9 async methods exist in JavaScript.html', () => {
-    it.each(ASYNC_METHOD_WIRING)(
-      '%s is declared as async method',
+  describe('all 5 JavaScript.html async methods exist', () => {
+    it.each(JS_HTML_ASYNC_METHODS)(
+      '%s is declared as async method in JavaScript.html',
       (methodName, _line, _expectedCalls) => {
         const body = extractMethodBody(jsHtmlSource, methodName);
         expect(body).not.toBeNull();
@@ -124,15 +147,34 @@ describe('Async App Methods — Wiring Smoke Tests (Static Analysis)', () => {
     );
   });
 
+  describe('all 4 DataIO.js.html async methods exist', () => {
+    it.each(DATA_IO_ASYNC_METHODS)(
+      '%s is declared as async method in DataIO.js.html',
+      (methodName, _line, _expectedCalls) => {
+        const body = extractMethodBody(dataIOSource, methodName);
+        expect(body).not.toBeNull();
+        expect(body).toContain('async function');
+      }
+    );
+  });
+
   // ─── 2. ServerApi.call wiring ──────────────────────────────────────────
 
+  /**
+   * Helper: resolve the correct source for a method
+   */
+  function resolveSource(methodName) {
+    if (DATA_IO_ASYNC_METHODS.some(([n]) => n === methodName)) return dataIOSource;
+    return jsHtmlSource;
+  }
+
   describe('each method calls expected ServerApi.call targets', () => {
     it.each(
       ASYNC_METHOD_WIRING.filter(([, , calls]) => calls.length > 0)
     )(
       '%s calls ServerApi.call with correct function name(s)',
       (methodName, _line, expectedCalls) => {
-        const body = extractMethodBody(jsHtmlSource, methodName);
+        const body = extractMethodBody(resolveSource(methodName), methodName);
         expect(body).not.toBeNull();
 
         const actualCalls = extractServerApiCalls(body);
@@ -149,7 +191,7 @@ describe('Async App Methods — Wiring Smoke Tests (Static Analysis)', () => {
     )(
       '%s has no ServerApi.call (pure frontend / delegator)',
       (methodName, _line, _expectedCalls) => {
-        const body = extractMethodBody(jsHtmlSource, methodName);
+        const body = extractMethodBody(resolveSource(methodName), methodName);
         expect(body).not.toBeNull();
 
         const actualCalls = extractServerApiCalls(body);
@@ -173,12 +215,15 @@ describe('Async App Methods — Wiring Smoke Tests (Static Analysis)', () => {
     );
   });
 
-  // ─── 4. No unexpected ServerApi.call in JavaScript.html ────────────────
+  // ─── 4. No unexpected ServerApi.call in source files ────────────────
 
   describe('completeness — no undocumented ServerApi.call targets', () => {
-    it('all ServerApi.call targets in JavaScript.html are in our wiring map', () => {
-      // Extract ALL ServerApi.call from entire JavaScript.html
-      const allCalls = extractServerApiCalls(jsHtmlSource);
+    it('all ServerApi.call targets in JavaScript.html + DataIO.js.html are in our wiring map', () => {
+      // Extract ALL ServerApi.call from JavaScript.html and DataIO.js.html
+      const allCalls = [
+        ...extractServerApiCalls(jsHtmlSource),
+        ...extractServerApiCalls(dataIOSource),
+      ];
       const uniqueCalls = [...new Set(allCalls)];
 
       // All targets documented in ASYNC_METHOD_WIRING
diff --git a/tests/unit/lifecycleRegression.test.js b/tests/unit/lifecycleRegression.test.js
index ad07827..bad1d5e 100644
--- a/tests/unit/lifecycleRegression.test.js
+++ b/tests/unit/lifecycleRegression.test.js
@@ -20,6 +20,7 @@ import {
 // ─── Source loading ──────────────────────────────────────────────────────
 
 const jsHtmlSource = loadSource(import.meta.dirname, '../../JavaScript.html');
+const dataIOSource = loadSource(import.meta.dirname, '../../DataIO.js.html');
 const interactionSource = loadSource(import.meta.dirname, '../../Interaction.js.html');
 const uiSource = loadSource(import.meta.dirname, '../../UI.js.html');
 
@@ -80,7 +81,7 @@ describe('Lifecycle Regression — init → load → render → interact → sav
   // ═══════════════════════════════════════════════════════════════════════
 
   describe('Phase B: load — data flow from server', () => {
-    const loadBody = extractMethodBody(jsHtmlSource, 'loadDataFromServer');
+    const loadBody = extractMethodBody(dataIOSource, 'loadDataFromServer');
 
     it('loadDataFromServer method exists', () => {
       expect(loadBody).not.toBeNull();
@@ -91,30 +92,30 @@ describe('Lifecycle Regression — init → load → render → interact → sav
       expect(calls).toContain('getData');
     });
 
-    it('updates this.schedules from result', () => {
-      expect(containsCall(loadBody, 'this\\.schedules\\s*=')).toBe(true);
+    it('updates App.schedules from result', () => {
+      expect(containsCall(loadBody, 'App\\.schedules\\s*=')).toBe(true);
     });
 
-    it('updates this.activeMetadataTimestamp', () => {
-      expect(containsCall(loadBody, 'this\\.activeMetadataTimestamp\\s*=')).toBe(true);
+    it('updates App.activeMetadataTimestamp', () => {
+      expect(containsCall(loadBody, 'App\\.activeMetadataTimestamp\\s*=')).toBe(true);
     });
 
     it('calls loadInitialSchedules after fetching', () => {
-      expect(containsCall(loadBody, 'this\\.loadInitialSchedules')).toBe(true);
+      expect(containsCall(loadBody, 'App\\.loadInitialSchedules')).toBe(true);
     });
 
     it('calls saveSchedulesToLocal after data processing', () => {
-      expect(containsCall(loadBody, 'this\\.saveSchedulesToLocal')).toBe(true);
+      expect(containsCall(loadBody, 'App\\.saveSchedulesToLocal')).toBe(true);
     });
 
     it('calls manageLoadingState for start and end', () => {
-      expect(containsCall(loadBody, "this\\.ui\\.manageLoadingState\\(\\s*'start'")).toBe(true);
-      expect(containsCall(loadBody, "this\\.ui\\.manageLoadingState\\(\\s*'end'")).toBe(true);
+      expect(containsCall(loadBody, "App\\.ui\\.manageLoadingState\\(\\s*'start'")).toBe(true);
+      expect(containsCall(loadBody, "App\\.ui\\.manageLoadingState\\(\\s*'end'")).toBe(true);
     });
 
     it('manages isConnecting flag', () => {
-      expect(containsCall(loadBody, 'this\\.isConnecting\\s*=\\s*true')).toBe(true);
-      expect(containsCall(loadBody, 'this\\.isConnecting\\s*=\\s*false')).toBe(true);
+      expect(containsCall(loadBody, 'App\\.isConnecting\\s*=\\s*true')).toBe(true);
+      expect(containsCall(loadBody, 'App\\.isConnecting\\s*=\\s*false')).toBe(true);
     });
   });
 
@@ -262,7 +263,7 @@ describe('Lifecycle Regression — init → load → render → interact → sav
   // ═══════════════════════════════════════════════════════════════════════
 
   describe('Phase E: save — data flow to server', () => {
-    const saveBody = extractMethodBody(jsHtmlSource, 'saveDataToServer');
+    const saveBody = extractMethodBody(dataIOSource, 'saveDataToServer');
 
     it('saveDataToServer method exists', () => {
       expect(saveBody).not.toBeNull();
@@ -273,14 +274,14 @@ describe('Lifecycle Regression — init → load → render → interact → sav
       expect(calls).toContain('saveData');
     });
 
-    it('collects data from this.classrooms, this.scheduleData, this.tags', () => {
-      expect(containsCall(saveBody, 'this\\.classrooms')).toBe(true);
-      expect(containsCall(saveBody, 'this\\.scheduleData')).toBe(true);
-      expect(containsCall(saveBody, 'this\\.tags')).toBe(true);
+    it('collects data from App.classrooms, App.scheduleData, App.tags', () => {
+      expect(containsCall(saveBody, 'App\\.classrooms')).toBe(true);
+      expect(containsCall(saveBody, 'App\\.scheduleData')).toBe(true);
+      expect(containsCall(saveBody, 'App\\.tags')).toBe(true);
     });
 
     it('includes lastModified timestamp for conflict detection', () => {
-      expect(containsCall(saveBody, 'this\\.scheduleLastModified')).toBe(true);
+      expect(containsCall(saveBody, 'App\\.scheduleLastModified')).toBe(true);
     });
 
     it('handles conflict response (saveResult.conflict)', () => {
@@ -288,20 +289,20 @@ describe('Lifecycle Regression — init → load → render → interact → sav
     });
 
     it('updates scheduleLastModified on success', () => {
-      expect(containsCall(saveBody, 'this\\.scheduleLastModified\\[this\\.activeScheduleId\\]\\s*=')).toBe(true);
+      expect(containsCall(saveBody, 'App\\.scheduleLastModified\\[App\\.activeScheduleId\\]\\s*=')).toBe(true);
     });
 
     it('calls manageLoadingState for start and end', () => {
-      expect(containsCall(saveBody, "this\\.ui\\.manageLoadingState\\(\\s*'start'")).toBe(true);
-      expect(containsCall(saveBody, "this\\.ui\\.manageLoadingState\\(\\s*'end'")).toBe(true);
+      expect(containsCall(saveBody, "App\\.ui\\.manageLoadingState\\(\\s*'start'")).toBe(true);
+      expect(containsCall(saveBody, "App\\.ui\\.manageLoadingState\\(\\s*'end'")).toBe(true);
     });
 
     it('manages isConnecting flag', () => {
-      expect(containsCall(saveBody, 'this\\.isConnecting')).toBe(true);
+      expect(containsCall(saveBody, 'App\\.isConnecting')).toBe(true);
     });
 
     it('updates history clean snapshot on success', () => {
-      expect(containsCall(saveBody, 'this\\.historyModule\\.updateCleanSnapshot')).toBe(true);
+      expect(containsCall(saveBody, 'App\\.historyModule\\.updateCleanSnapshot')).toBe(true);
     });
   });
 
@@ -320,8 +321,8 @@ describe('Lifecycle Regression — init → load → render → interact → sav
     });
 
     it('load → render: loadDataFromServer calls loadInitialSchedules which calls loadSchedule', () => {
-      const loadBody = extractMethodBody(jsHtmlSource, 'loadDataFromServer');
-      expect(containsCall(loadBody, 'this\\.loadInitialSchedules')).toBe(true);
+      const loadBody = extractMethodBody(dataIOSource, 'loadDataFromServer');
+      expect(containsCall(loadBody, 'App\\.loadInitialSchedules')).toBe(true);
 
       const loadInitBody = extractMethodBody(jsHtmlSource, 'loadInitialSchedules');
       expect(containsCall(loadInitBody, 'this\\.loadSchedule')).toBe(true);
@@ -342,9 +343,9 @@ describe('Lifecycle Regression — init → load → render → interact → sav
     });
 
     it('save → render: saveDataToServer updates history which can trigger re-render', () => {
-      const saveBody = extractMethodBody(jsHtmlSource, 'saveDataToServer');
-      expect(containsCall(saveBody, 'this\\.historyModule\\.updateCleanSnapshot')).toBe(true);
-      expect(containsCall(saveBody, 'this\\.historyModule\\.checkDirty')).toBe(true);
+      const saveBody = extractMethodBody(dataIOSource, 'saveDataToServer');
+      expect(containsCall(saveBody, 'App\\.historyModule\\.updateCleanSnapshot')).toBe(true);
+      expect(containsCall(saveBody, 'App\\.historyModule\\.checkDirty')).toBe(true);
     });
   });