diff --git a/tests/unit/backend.test.js b/tests/unit/backend.test.js
index 5a7306b..4ee892f 100644
--- a/tests/unit/backend.test.js
+++ b/tests/unit/backend.test.js
@@ -2,24 +2,29 @@
  * Backend GAS function tests using mock runtime.
  * Ref: #51 — Wave 5 GAS mock testing phase 2
  *
- * Strategy: Wrap 程式碼.js source in a factory function that receives mock
- * objects as params, returning the declared functions for direct testing.
+ * Strategy: Install GAS mocks as globals via vi.stubGlobal, then require()
+ * 程式碼.js directly so v8 can instrument it for coverage. Module cache is
+ * invalidated between calls to get a fresh evaluation (matching the old
+ * sandbox-per-test behavior).
+ *
+ * Ref: #107 — Migrated from new Function() sandbox to direct require() for
+ * v8 coverage instrumentation.
  */
-import { describe, it, expect } from 'vitest';
-import { readFileSync } from 'fs';
-import { resolve } from 'path';
+import { describe, it, expect, vi } from 'vitest';
+import { createRequire } from 'module';
 import { createMockSheet, createMockSpreadsheetApp, createMockSession,
          createMockLockService, createMockPropertiesService, createMockLogger,
          createMockHtmlService, createMockDriveApp } from '../mocks/gasMocks.js';
 
-const gasSource = readFileSync(
-  resolve(import.meta.dirname, '../../程式碼.js'),
-  'utf-8'
-);
+const _require = createRequire(import.meta.url);
+const backendPath = _require.resolve('../../程式碼.js');
 
 /**
- * Create a sandboxed GAS environment — wraps 程式碼.js in a function that
- * receives GAS globals as parameters and returns all declared functions.
+ * Create a GAS environment — installs mocks as globals, then require()s
+ * 程式碼.js with a fresh module evaluation (cache invalidated).
+ *
+ * Ref: #107 — replaced new Function() sandbox with direct require() so
+ * v8 coverage provider can instrument 程式碼.js.
  */
 function createGasEnv(opts = {}) {
   const sheets = opts.sheets || {};
@@ -31,26 +36,19 @@ function createGasEnv(opts = {}) {
   const HtmlService = createMockHtmlService();
   const DriveApp = createMockDriveApp(opts.driveFiles || {});
 
-  // Wrap the GAS source so that all top-level functions become properties
-  // of an object we can return. We inject the GAS globals as local variables.
-  const wrappedSource = `
-    return (function(SpreadsheetApp, Session, LockService, PropertiesService, Logger, HtmlService, DriveApp) {
-      ${gasSource}
-      return {
-        getConfig, _findScheduleRowInfo, _checkPermission, _getSs, getSheet, getOrCreateSheet,
-        doGet, getData, saveData, checkMetadata, addSchedule,
-        updateScheduleMetadata, deleteSchedule, copySchedule,
-        getVersions, getVersionData, getFontBase64FromDrive
-      };
-    })(SpreadsheetApp, Session, LockService, PropertiesService, Logger, HtmlService, DriveApp);
-  `;
-
-  const factory = new Function(
-    'SpreadsheetApp', 'Session', 'LockService', 'PropertiesService', 'Logger', 'HtmlService', 'DriveApp',
-    wrappedSource
-  );
-
-  return factory(SpreadsheetApp, Session, LockService, PropertiesService, Logger, HtmlService, DriveApp);
+  // Install GAS globals so 程式碼.js's top-level code can find them
+  vi.stubGlobal('SpreadsheetApp', SpreadsheetApp);
+  vi.stubGlobal('Session', Session);
+  vi.stubGlobal('LockService', LockService);
+  vi.stubGlobal('PropertiesService', PropertiesService);
+  vi.stubGlobal('Logger', Logger);
+  vi.stubGlobal('HtmlService', HtmlService);
+  vi.stubGlobal('DriveApp', DriveApp);
+
+  // Invalidate module cache to get a fresh evaluation (resets _ss memoization)
+  delete _require.cache[backendPath];
+
+  return _require(backendPath);
 }
 
 // ─── checkMetadata ───────────────────────────────────────────────────────
diff --git a/tests/unit/backendSignatureContracts.test.js b/tests/unit/backendSignatureContracts.test.js
index 5973b6a..4479bd1 100644
--- a/tests/unit/backendSignatureContracts.test.js
+++ b/tests/unit/backendSignatureContracts.test.js
@@ -4,26 +4,26 @@
  *
  * Ref: #107 — P0 Coverage Sprint Wave 1 (signature contracts)
  *
- * Strategy: Reuses the createGasEnv() sandbox pattern from backend.test.js
- * to wrap 程式碼.js and expose all functions. Validates:
+ * Strategy: Installs GAS mocks as globals, then require()s 程式碼.js directly
+ * so v8 can instrument it for coverage. Validates:
  *   1. All 17 functions exist and are typeof 'function'
  *   2. Each function's .length matches its declared parameter count
  *   3. The 9 frontend-called functions (via ServerApi.call) exist in env
+ *
+ * Ref: #107 — Migrated from new Function() sandbox to direct require().
  */
-import { describe, it, expect } from 'vitest';
-import { readFileSync } from 'fs';
-import { resolve } from 'path';
-import { createMockSheet, createMockSpreadsheetApp, createMockSession,
+import { describe, it, expect, vi } from 'vitest';
+import { createRequire } from 'module';
+import { createMockSpreadsheetApp, createMockSession,
          createMockLockService, createMockPropertiesService, createMockLogger,
          createMockHtmlService, createMockDriveApp } from '../mocks/gasMocks.js';
 
-const gasSource = readFileSync(
-  resolve(import.meta.dirname, '../../程式碼.js'),
-  'utf-8'
-);
+const _require = createRequire(import.meta.url);
+const backendPath = _require.resolve('../../程式碼.js');
 
 /**
- * Create a sandboxed GAS environment — mirrors backend.test.js createGasEnv.
+ * Create a GAS environment — mirrors backend.test.js createGasEnv.
+ * Ref: #107 — direct require() for v8 coverage.
  */
 function createGasEnv(opts = {}) {
   const sheets = opts.sheets || {};
@@ -35,24 +35,17 @@ function createGasEnv(opts = {}) {
   const HtmlService = createMockHtmlService();
   const DriveApp = createMockDriveApp(opts.driveFiles || {});
 
-  const wrappedSource = `
-    return (function(SpreadsheetApp, Session, LockService, PropertiesService, Logger, HtmlService, DriveApp) {
-      ${gasSource}
-      return {
-        getConfig, _findScheduleRowInfo, _checkPermission, _getSs, getSheet, getOrCreateSheet,
-        doGet, getData, saveData, checkMetadata, addSchedule,
-        updateScheduleMetadata, deleteSchedule, copySchedule,
-        getVersions, getVersionData, getFontBase64FromDrive
-      };
-    })(SpreadsheetApp, Session, LockService, PropertiesService, Logger, HtmlService, DriveApp);
-  `;
-
-  const factory = new Function(
-    'SpreadsheetApp', 'Session', 'LockService', 'PropertiesService', 'Logger', 'HtmlService', 'DriveApp',
-    wrappedSource
-  );
-
-  return factory(SpreadsheetApp, Session, LockService, PropertiesService, Logger, HtmlService, DriveApp);
+  vi.stubGlobal('SpreadsheetApp', SpreadsheetApp);
+  vi.stubGlobal('Session', Session);
+  vi.stubGlobal('LockService', LockService);
+  vi.stubGlobal('PropertiesService', PropertiesService);
+  vi.stubGlobal('Logger', Logger);
+  vi.stubGlobal('HtmlService', HtmlService);
+  vi.stubGlobal('DriveApp', DriveApp);
+
+  delete _require.cache[backendPath];
+
+  return _require(backendPath);
 }
 
 // ─── All 17 top-level functions with expected parameter counts ────────────
@@ -116,8 +109,10 @@ describe('程式碼.js Signature Contracts', () => {
       }
     );
 
-    it('env exposes exactly 17 functions', () => {
-      const fnCount = Object.keys(env).filter(k => typeof env[k] === 'function').length;
+    it('env exposes exactly 17 production functions (excluding test helpers)', () => {
+      const fnCount = Object.keys(env)
+        .filter(k => typeof env[k] === 'function' && !k.startsWith('_reset'))
+        .length;
       expect(fnCount).toBe(17);
     });
   });
diff --git a/tests/unit/businessLogicEdgeCases.test.js b/tests/unit/businessLogicEdgeCases.test.js
index e743dfd..48be1e6 100644
--- a/tests/unit/businessLogicEdgeCases.test.js
+++ b/tests/unit/businessLogicEdgeCases.test.js
@@ -12,9 +12,8 @@
  *
  * Closes #138
  */
-import { describe, it, expect } from 'vitest';
-import { readFileSync } from 'fs';
-import { resolve } from 'path';
+import { describe, it, expect, vi } from 'vitest';
+import { createRequire } from 'module';
 import {
   timeToMinutes,
   checkTimeConflict,
@@ -23,12 +22,10 @@ import { createMockSheet, createMockSpreadsheetApp, createMockSession,
          createMockLockService, createMockPropertiesService, createMockLogger,
          createMockHtmlService, createMockDriveApp } from '../mocks/gasMocks.js';
 
-// ─── GAS environment factory (same as backend.test.js) ─────────────────────
+// ─── GAS environment factory (Ref: #107 — direct require for v8 coverage) ──
 
-const gasSource = readFileSync(
-  resolve(import.meta.dirname, '../../程式碼.js'),
-  'utf-8'
-);
+const _require = createRequire(import.meta.url);
+const backendPath = _require.resolve('../../程式碼.js');
 
 function createGasEnv(opts = {}) {
   const sheets = opts.sheets || {};
@@ -40,24 +37,17 @@ function createGasEnv(opts = {}) {
   const HtmlService = createMockHtmlService();
   const DriveApp = createMockDriveApp(opts.driveFiles || {});
 
-  const wrappedSource = `
-    return (function(SpreadsheetApp, Session, LockService, PropertiesService, Logger, HtmlService, DriveApp) {
-      ${gasSource}
-      return {
-        getConfig, _findScheduleRowInfo, _checkPermission, _getSs, getSheet, getOrCreateSheet,
-        doGet, getData, saveData, checkMetadata, addSchedule,
-        updateScheduleMetadata, deleteSchedule, copySchedule,
-        getVersions, getVersionData, getFontBase64FromDrive
-      };
-    })(SpreadsheetApp, Session, LockService, PropertiesService, Logger, HtmlService, DriveApp);
-  `;
-
-  const factory = new Function(
-    'SpreadsheetApp', 'Session', 'LockService', 'PropertiesService', 'Logger', 'HtmlService', 'DriveApp',
-    wrappedSource
-  );
-
-  return factory(SpreadsheetApp, Session, LockService, PropertiesService, Logger, HtmlService, DriveApp);
+  vi.stubGlobal('SpreadsheetApp', SpreadsheetApp);
+  vi.stubGlobal('Session', Session);
+  vi.stubGlobal('LockService', LockService);
+  vi.stubGlobal('PropertiesService', PropertiesService);
+  vi.stubGlobal('Logger', Logger);
+  vi.stubGlobal('HtmlService', HtmlService);
+  vi.stubGlobal('DriveApp', DriveApp);
+
+  delete _require.cache[backendPath];
+
+  return _require(backendPath);
 }
 
 // ═══════════════════════════════════════════════════════════════════════════
diff --git a/tests/unit/wiringContracts.test.js b/tests/unit/wiringContracts.test.js
index de64544..3e7672e 100644
--- a/tests/unit/wiringContracts.test.js
+++ b/tests/unit/wiringContracts.test.js
@@ -40,42 +40,39 @@ function extractProductionFunctions(source) {
 
 const productionFunctions = extractProductionFunctions(productionSource);
 
-// ─── Parse backend.test.js factory return ──────────────────────────────────
-
-const backendTestSource = readFileSync(
-  resolve(import.meta.dirname, './backend.test.js'),
-  'utf-8'
+// ─── Verify 程式碼.js exports via direct require ─────────────────────────────
+// Ref: #107 — backend.test.js no longer uses factory return block; instead
+// 程式碼.js exports its functions via conditional module.exports. We verify
+// the wiring by requiring the module directly.
+
+import { createRequire } from 'module';
+import { createMockSpreadsheetApp, createMockSession,
+         createMockLockService, createMockPropertiesService, createMockLogger,
+         createMockHtmlService, createMockDriveApp } from '../mocks/gasMocks.js';
+
+const _require = createRequire(import.meta.url);
+const backendPath = _require.resolve('../../程式碼.js');
+
+// Install minimal GAS mocks so require() succeeds (程式碼.js accesses no globals
+// at module-load time, but the conditional export block reads function refs)
+globalThis.SpreadsheetApp = createMockSpreadsheetApp({});
+globalThis.Session = createMockSession('test@example.com');
+globalThis.LockService = createMockLockService();
+globalThis.PropertiesService = createMockPropertiesService({});
+globalThis.Logger = createMockLogger();
+globalThis.HtmlService = createMockHtmlService();
+globalThis.DriveApp = createMockDriveApp({});
+
+delete _require.cache[backendPath];
+const backendExports = _require(backendPath);
+
+// Extract function names from the module exports (excluding test-only helpers)
+const factoryReturnNames = new Set(
+  Object.keys(backendExports).filter(k =>
+    typeof backendExports[k] === 'function' && !k.startsWith('_reset')
+  )
 );
 
-/**
- * Extract function names from the factory return block in backend.test.js.
- * The factory pattern returns an object literal: `return { fn1, fn2, ... };`
- */
-function extractFactoryReturnNames(source) {
-  // Find the return { ... } block inside the wrapped source template literal
-  const returnBlockRegex = /return\s*\{[\s\S]*?\};\s*\}\)\(SpreadsheetApp/;
-  const blockMatch = source.match(returnBlockRegex);
-  if (!blockMatch) return new Set();
-
-  const block = blockMatch[0];
-  // Extract identifiers (handles multiline, trailing commas)
-  const names = new Set();
-  const idRegex = /\b(\w+)\b/g;
-  let m;
-  // Skip the 'return' keyword and the closing parens
-  const inner = block.replace(/^return\s*\{/, '').replace(/\};\s*\}\)\(SpreadsheetApp$/, '');
-  while ((m = idRegex.exec(inner)) !== null) {
-    const name = m[1];
-    // Filter out non-function tokens
-    if (name !== 'return' && name !== 'SpreadsheetApp') {
-      names.add(name);
-    }
-  }
-  return names;
-}
-
-const factoryReturnNames = extractFactoryReturnNames(backendTestSource);
-
 // ─── Parse tests/lib/ exported functions ───────────────────────────────────
 
 const libDir = resolve(import.meta.dirname, '../lib');
diff --git "a/\347\250\213\345\274\217\347\242\274.js" "b/\347\250\213\345\274\217\347\242\274.js"
index 04d24e2..5cf555c 100644
--- "a/\347\250\213\345\274\217\347\242\274.js"
+++ "b/\347\250\213\345\274\217\347\242\274.js"
@@ -602,4 +602,19 @@ function getFontBase64FromDrive() {
     Logger.log(`從 Drive 獲取字體時發生錯誤: ${e.stack}`);
     return { success: false, error: e.toString() };
   }
-}
\ No newline at end of file
+}
+
+// Ref: #107 — Enable vitest v8 coverage instrumentation.
+// GAS runtime has no `module` global, so this export block is a no-op in production.
+/* eslint-disable no-undef */
+if (typeof module !== 'undefined') {
+  module.exports = {
+    _getSs, getConfig, _findScheduleRowInfo, _checkPermission,
+    getSheet, getOrCreateSheet, doGet, getData, saveData, checkMetadata,
+    addSchedule, updateScheduleMetadata, deleteSchedule, copySchedule,
+    getVersions, getVersionData, getFontBase64FromDrive,
+    // Test-only: allow resetting memoized spreadsheet reference between tests
+    _resetSs: () => { _ss = null; },
+  };
+}
+/* eslint-enable no-undef */
\ No newline at end of file