diff --git a/Megrez.Tests/MegrezTests.cs b/Megrez.Tests/MegrezTests.cs
index 4392172..b77bb4f 100644
--- a/Megrez.Tests/MegrezTests.cs
+++ b/Megrez.Tests/MegrezTests.cs
@@ -54,8 +54,8 @@ public void Test03_BasicFeaturesOfCompositor() {
     Assert.AreEqual(actual: compositor.Separator, expected: "");
     Assert.AreEqual(actual: compositor.Cursor, expected: 0);
     Assert.AreEqual(actual: compositor.Length, expected: 0);
-
-    Assert.IsTrue(compositor.InsertKey("a"));
+    bool foobar = compositor.InsertKey("a");
+    Assert.IsTrue(foobar);
     Assert.AreEqual(actual: compositor.Cursor, expected: 1);
     Assert.AreEqual(actual: compositor.Length, expected: 1);
     Assert.AreEqual(actual: compositor.Spans.Count, expected: 1);
diff --git a/Megrez/src/0_CSharpExtensions.cs b/Megrez/src/0_CSharpExtensions.cs
index 97decb6..0bbc4c7 100644
--- a/Megrez/src/0_CSharpExtensions.cs
+++ b/Megrez/src/0_CSharpExtensions.cs
@@ -98,7 +98,7 @@ public BRange(int lowerbound, int upperbound) {
 
   public List<int> ToList() {
     List<int> result = new();
-    for (int i = Lowerbound; i < Upperbound; i++) {
+    for (int i = Lowerbound; i <= Upperbound; i++) {
       result.Add(i);
     }
     return result;
diff --git a/Megrez/src/1_Compositor.cs b/Megrez/src/1_Compositor.cs
index 043f958..d5e0b28 100644
--- a/Megrez/src/1_Compositor.cs
+++ b/Megrez/src/1_Compositor.cs
@@ -70,15 +70,6 @@ public enum ResizeBehavior {
   /// </summary>
   public CompositorConfig Config = new();
 
-  private static int _maxSpanLength = 10;
-  /// <summary>
-  /// 一個幅位單元內所能接受的最長的節點幅位長度。
-  /// </summary>
-  public static int MaxSpanLength {
-    get => _maxSpanLength;
-    set => _maxSpanLength = Math.Max(6, value);
-  }
-
   /// <summary>
   /// 公用變數，在生成索引鍵字串時用來分割每個索引鍵單位。最好是鍵盤無法直接敲的 ASCII 字元。
   /// </summary>
@@ -226,7 +217,7 @@ public bool InsertKey(string key) {
     if (string.IsNullOrEmpty(key) || key == Separator) return false;
     if (!TheLangModel.HasUnigramsFor(new() { key })) return false;
     Keys.Insert(Cursor, key);
-    List<SpanUnit> gridBackup = Spans;
+    List<SpanUnit> gridBackup = Spans.Select(x => x.HardCopy()).ToList();
     ResizeGridAt(Cursor, ResizeBehavior.Expand);
     int nodesInserted = Update();
     // 用來在 langModel.HasUnigramsFor() 結果不準確的時候防呆、恢復被搞壞的 Spans。
@@ -351,6 +342,7 @@ public string DumpDOT() {
   /// <param name="action">指定是擴張還是縮減一個幅位。</param>
   internal void ResizeGridAt(int location, ResizeBehavior action) {
     location = Math.Max(Math.Min(location, Spans.Count), 0);  // 防呆。
+    int oldContainerLength = Spans.Count;
     switch (action) {
       case ResizeBehavior.Expand:
         Spans.Insert(location, new());
@@ -361,7 +353,9 @@ internal void ResizeGridAt(int location, ResizeBehavior action) {
         Spans.RemoveAt(location);
         break;
     }
-    DropWreckedNodesAt(location);
+    int newContainerLength = Spans.Count;
+    int sizeDelta = newContainerLength - oldContainerLength;
+    DropWreckedNodesAt(location, sizeDelta);
   }
 
   /// <summary>
@@ -397,42 +391,22 @@ internal void ResizeGridAt(int location, ResizeBehavior action) {
   /// </code>
   /// </summary>
   /// <param name="location">給定的幅位座標。</param>
-  internal void DropWreckedNodesAt(int location) {
+  /// <param name="sizeDelta">在需要呼叫這個方法時，Grid 的長度變化量（可為負數）。</param>
+  internal void DropWreckedNodesAt(int location, int sizeDelta) {
+    int oldContainerLength = Spans.Count - sizeDelta;
+    if (oldContainerLength < 0) return;
     location = Math.Max(Math.Min(location, Spans.Count), 0);  // 防呆。
     if (Spans.IsEmpty()) return;
-    int affectedLength = MaxSpanLength - 1;
+    int affectedLength = oldContainerLength - 1;
     int begin = Math.Max(0, location - affectedLength);
     if (location < begin) return;
-    foreach (int delta in new BRange(begin, location)) {
-      foreach (int theLength in new BRange(location - delta + 1, MaxSpanLength)) {
+    foreach (int delta in new BRange(begin, location - 1)) {
+      foreach (int theLength in new BRange(location - delta + 1, oldContainerLength)) {
         Spans[delta].Nodes.Remove(theLength);
       }
     }
   }
 
-  /// <summary>
-  /// 自索引鍵陣列獲取指定範圍的資料。
-  /// </summary>
-  /// <param name="range">指定範圍。</param>
-  /// <returns>拿到的資料。</returns>
-  private List<string> GetJoinedKeyArray(BRange range) =>
-      range.Upperbound <= Keys.Count && range.Lowerbound >= 0
-          ? Keys.GetRange(range.Lowerbound, range.Upperbound - range.Lowerbound).ToList()
-          : new();
-
-  /// <summary>
-  /// 在指定位置（以指定索引鍵陣列和指定幅位長度）拿取節點。
-  /// </summary>
-  /// <param name="location">指定游標位置。</param>
-  /// <param name="length">指定幅位長度。</param>
-  /// <param name="keyArray">指定索引鍵陣列。</param>
-  /// <returns>拿取的節點。拿不到的話就會是 null。</returns>
-  private Node? GetNodeAt(int location, int length, List<string> keyArray) {
-    location = Math.Max(Math.Min(location, Spans.Count - 1), 0);  // 防呆。
-    return Spans[location].NodeOf(length) is not {}
-    node ? null : node.KeyArray.SequenceEqual(keyArray) ? node : null;
-  }
-
   /// <summary>
   /// 根據當前狀況更新整個組字器的節點文脈。
   /// </summary>
@@ -442,19 +416,22 @@ private List<string> GetJoinedKeyArray(BRange range) =>
   /// </param>
   /// <returns>新增或影響了多少個節點。如果返回「0」則表示可能發生了錯誤。 </returns>
   public int Update(bool updateExisting = false) {
-    BRange range = new(Math.Max(0, Cursor - MaxSpanLength), Math.Min(Cursor + MaxSpanLength, Keys.Count));
     int nodesChanged = 0;
-    foreach (int position in range) {
-      foreach (int theLength in new BRange(1, Math.Min(MaxSpanLength, range.Upperbound - position) + 1)) {
-        List<string> joinedKeyArray = GetJoinedKeyArray(new(position, position + theLength));
-        BRange safeLocationRange = new(0, Spans.Count);
-        Node? theNode = safeLocationRange.Contains(position) ? GetNodeAt(position, theLength, joinedKeyArray) : null;
-        if (theNode is {}) {
+    int spansCount = Spans.Count;
+    if (spansCount < 1) return 0;
+    foreach (int position in new BRange(0, Spans.Count - 1)) {
+      int upperBound4Lengths = spansCount - position;
+      if (upperBound4Lengths < 1) continue;
+      foreach (int theLength in new BRange(1, upperBound4Lengths)) {
+        if (!(position + theLength <= Keys.Count && position >= 0)) continue;
+        List<string> joinedKeyArray = Keys.GetRange(position, theLength);
+        if (Spans[position].NodeOf(theLength) is {} theNode) {
           if (!updateExisting) continue;
           List<Unigram> unigramsA = TheLangModel.UnigramsFor(joinedKeyArray);
+          // 自動銷毀無效的節點。
           if (unigramsA.IsEmpty()) {
             if (theNode.KeyArray.Count == 1) continue;
-            Spans[position].Nullify(givenNode: theNode);
+            Spans[position].Nodes.Remove(theNode.SpanLength);
           } else {
             theNode.SyncingUnigramsFrom(unigramsA);
           }
diff --git a/Megrez/src/4_SpanUnit.cs b/Megrez/src/4_SpanUnit.cs
index 8363258..4ae2b9f 100644
--- a/Megrez/src/4_SpanUnit.cs
+++ b/Megrez/src/4_SpanUnit.cs
@@ -86,12 +86,6 @@ public bool Append(Node node) {
       return true;
     }
 
-    /// <summary>
-    /// 丟掉任何與給定節點完全雷同的節點。
-    /// </summary>
-    /// <param name="givenNode">要參照的節點。</param>
-    public void Nullify(Node givenNode) => Nodes.Remove(givenNode.SpanLength);
-
     /// <summary>
     /// 以給定的幅位長度，在當前幅位單元內找出對應的節點。
     /// </summary>
@@ -143,7 +137,7 @@ public List<NodeWithLocation> FetchOverlappingNodesAt(int givenLocation) {
     }
 
     // 再獲取以當前位置結尾或開頭的節點。
-    int begin = givenLocation - Math.Min(givenLocation, MaxSpanLength - 1);
+    int begin = givenLocation - Math.Min(givenLocation, Spans.Count - 1);
     foreach (int theLocation in new BRange(begin, givenLocation)) {
       int alpha = givenLocation - theLocation + 1;
       int bravo = Spans[theLocation].MaxLength;