diff --git a/Packages/vChewing_MainAssembly/Sources/MainAssembly/AppDelegate.swift b/Packages/vChewing_MainAssembly/Sources/MainAssembly/AppDelegate.swift
index dcb983423..105b669e2 100644
--- a/Packages/vChewing_MainAssembly/Sources/MainAssembly/AppDelegate.swift
+++ b/Packages/vChewing_MainAssembly/Sources/MainAssembly/AppDelegate.swift
@@ -69,6 +69,8 @@ public extension AppDelegate {
 
     SpeechSputnik.shared.refreshStatus() // 根據現狀條件決定是否初期化語音引擎。
 
+    CandidateTextService.enableFinalSanityCheck()
+
     // 一旦發現與使用者半衰模組的觀察行為有關的崩潰標記被開啟：
     // 如果有開啟 Debug 模式的話，就將既有的半衰記憶資料檔案更名＋打上當時的時間戳。
     // 如果沒有開啟 Debug 模式的話，則將半衰記憶資料直接清空。
diff --git a/Packages/vChewing_MainAssembly/Sources/MainAssembly/CandidateTextService_SelectorImpl.swift b/Packages/vChewing_MainAssembly/Sources/MainAssembly/CandidateTextService_SelectorImpl.swift
index 4b420bbeb..24bd3cc46 100644
--- a/Packages/vChewing_MainAssembly/Sources/MainAssembly/CandidateTextService_SelectorImpl.swift
+++ b/Packages/vChewing_MainAssembly/Sources/MainAssembly/CandidateTextService_SelectorImpl.swift
@@ -12,6 +12,28 @@ import Shared
 import Tekkon
 
 public extension CandidateTextService {
+  // MARK: - Final Sanity Check Implementation.
+
+  static func enableFinalSanityCheck() {
+    finalSanityCheck = finalSanityCheckImplemented
+  }
+
+  private static func finalSanityCheckImplemented(_ target: CandidateTextService) -> Bool {
+    switch target.value {
+    case .url: return true
+    case let .selector(strSelector):
+      guard target.candidateText != "%s" else { return true } // 防止誤傷到編輯器。
+      switch strSelector {
+      case "copyUnicodeMetadata:": return true
+      case _ where strSelector.hasPrefix("copyRuby"),
+           _ where strSelector.hasPrefix("copyBraille"),
+           _ where strSelector.hasPrefix("copyInline"):
+        return !target.reading.joined().isEmpty // 以便應對 [""] 的情況。
+      default: return true
+      }
+    }
+  }
+
   // MARK: - Selector Methods, CandidatePairServicable, and the Coordinator.
 
   var responseFromSelector: String? {
diff --git a/Packages/vChewing_MainAssembly/Tests/MainAssemblyTests/CandidateServiceCoordinatorTests.swift b/Packages/vChewing_MainAssembly/Tests/MainAssemblyTests/CandidateServiceCoordinatorTests.swift
index cf639e138..1e7a64c32 100644
--- a/Packages/vChewing_MainAssembly/Tests/MainAssemblyTests/CandidateServiceCoordinatorTests.swift
+++ b/Packages/vChewing_MainAssembly/Tests/MainAssemblyTests/CandidateServiceCoordinatorTests.swift
@@ -24,6 +24,21 @@ class CandidateServiceCoordinatorTests: XCTestCase {
     #"Braille 2018: %s"# + "\t" + #"@SEL:copyBraille2018:"#,
   ]
 
+  func testSelector_FinalSanityCheck() throws {
+    var stacked = Self.testDataMap.parseIntoCandidateTextServiceStack(
+      candidate: "胡桃", reading: [] // 故意使用空 Reading
+    )
+    let count1 = stacked.count
+    print("Current Count before Sanity Check ON: \(stacked.count)")
+    CandidateTextService.enableFinalSanityCheck()
+    stacked = Self.testDataMap.parseIntoCandidateTextServiceStack(
+      candidate: "胡桃", reading: [] // 故意使用空 Reading
+    )
+    let count2 = stacked.count
+    print("Current Count after Sanity Check ON: \(stacked.count)")
+    XCTAssertGreaterThan(count1, count2)
+  }
+
   func testSelector_UnicodeMetadata() throws {
     let stacked = Self.testDataMap.parseIntoCandidateTextServiceStack(
       candidate: "胡桃", reading: ["ㄏㄨˊ", "ㄊㄠˊ"]
diff --git a/Packages/vChewing_Shared/Sources/Shared/CandidateTextService.swift b/Packages/vChewing_Shared/Sources/Shared/CandidateTextService.swift
index b11f693a8..5f93b1fcb 100644
--- a/Packages/vChewing_Shared/Sources/Shared/CandidateTextService.swift
+++ b/Packages/vChewing_Shared/Sources/Shared/CandidateTextService.swift
@@ -26,6 +26,8 @@ public struct CandidateTextService: Codable {
   public let value: ServiceValue
   public let candidateText: String
 
+  public static var finalSanityCheck: ((CandidateTextService) -> Bool)?
+
   public init?(key: String, definedValue: String, param: String = #"%s"#, reading: [String] = []) {
     guard !key.isEmpty, !definedValue.isEmpty, definedValue.first != "#" else { return nil }
     candidateText = param
@@ -62,6 +64,8 @@ public struct CandidateTextService: Codable {
     }
     guard let finalServiceValue = finalServiceValue else { return nil }
     value = finalServiceValue
+    let finalSanityCheckResult = Self.finalSanityCheck?(self) ?? true
+    if !finalSanityCheckResult { return nil }
   }
 }