diff --git a/Packages/vChewing_Megrez/Sources/Megrez/1_Compositor.swift b/Packages/vChewing_Megrez/Sources/Megrez/1_Compositor.swift
index c1e6501a..465ae409 100644
--- a/Packages/vChewing_Megrez/Sources/Megrez/1_Compositor.swift
+++ b/Packages/vChewing_Megrez/Sources/Megrez/1_Compositor.swift
@@ -21,7 +21,7 @@ extension Megrez {
     /// 該軌格內可以允許的最大幅位長度。
     public static var maxSpanLength: Int = 10 { didSet { maxSpanLength = max(6, maxSpanLength) } }
     /// 公開：多字讀音鍵當中用以分割漢字讀音的記號的預設值，是「-」。
-    public static let kDefaultSeparator: String = "-"
+    public static var theSeparator: String = "-"
     /// 該組字器的游標位置。
     public var cursor: Int = 0 {
       didSet {
@@ -33,7 +33,12 @@ extension Megrez {
     /// 該組字器的標記器位置。
     public var marker: Int = 0 { didSet { marker = max(0, min(marker, length)) } }
     /// 公開：多字讀音鍵當中用以分割漢字讀音的記號，預設為「-」。
-    public var separator = kDefaultSeparator
+    public var separator = theSeparator {
+      didSet {
+        Self.theSeparator = separator
+      }
+    }
+
     /// 公開：組字器內已經插入的單筆索引鍵的數量。
     public var width: Int { keys.count }
     /// 公開：最近一次爬軌結果。
@@ -71,7 +76,7 @@ extension Megrez {
     /// - Parameter key: 要插入的索引鍵。
     /// - Returns: 該操作是否成功執行。
     @discardableResult public mutating func insertKey(_ key: String) -> Bool {
-      guard !key.isEmpty, key != separator, langModel.hasUnigramsFor(key: key) else { return false }
+      guard !key.isEmpty, key != separator, langModel.hasUnigramsFor(keyArray: [key]) else { return false }
       keys.insert(key, at: cursor)
       let gridBackup = spans
       resizeGrid(at: cursor, do: .expand)
@@ -242,7 +247,7 @@ extension Megrez.Compositor {
     return true
   }
 
-  func getJointKeyArray(range: Range<Int>) -> [String] {
+  func getJoinedKeyArray(range: Range<Int>) -> [String] {
     // 下面這句不能用 contains，不然會要求至少 macOS 13 Ventura。
     guard range.upperBound <= keys.count, range.lowerBound >= 0 else { return [] }
     return keys[range].map { String($0) }
@@ -262,11 +267,10 @@ extension Megrez.Compositor {
     var nodesChanged = 0
     for position in range {
       for theLength in 1...min(maxSpanLength, range.upperBound - position) {
-        let jointKeyArray = getJointKeyArray(range: position..<(position + theLength))
-        let jointKey = jointKeyArray.joined(separator: separator)
-        if let theNode = getNode(at: position, length: theLength, keyArray: jointKeyArray) {
+        let joinedKeyArray = getJoinedKeyArray(range: position..<(position + theLength))
+        if let theNode = getNode(at: position, length: theLength, keyArray: joinedKeyArray) {
           if !updateExisting { continue }
-          let unigrams = langModel.unigramsFor(key: jointKey)
+          let unigrams = langModel.unigramsFor(keyArray: joinedKeyArray)
           // 自動銷毀無效的節點。
           if unigrams.isEmpty {
             if theNode.keyArray.count == 1 { continue }
@@ -277,10 +281,10 @@ extension Megrez.Compositor {
           nodesChanged += 1
           continue
         }
-        let unigrams = langModel.unigramsFor(key: jointKey)
+        let unigrams = langModel.unigramsFor(keyArray: joinedKeyArray)
         guard !unigrams.isEmpty else { continue }
         insertNode(
-          .init(keyArray: jointKeyArray, spanLength: theLength, unigrams: unigrams, keySeparator: separator),
+          .init(keyArray: joinedKeyArray, spanLength: theLength, unigrams: unigrams),
           at: position
         )
         nodesChanged += 1
diff --git a/Packages/vChewing_Megrez/Sources/Megrez/2_Walker.swift b/Packages/vChewing_Megrez/Sources/Megrez/2_Walker.swift
index 385f837a..ee755c79 100644
--- a/Packages/vChewing_Megrez/Sources/Megrez/2_Walker.swift
+++ b/Packages/vChewing_Megrez/Sources/Megrez/2_Walker.swift
@@ -32,7 +32,7 @@ extension Megrez.Compositor {
       }
     }
 
-    let terminal = Vertex(node: .init(keyArray: ["_TERMINAL_"], keySeparator: separator))
+    let terminal = Vertex(node: .init(keyArray: ["_TERMINAL_"]))
 
     for (i, vertexSpan) in vertexSpans.enumerated() {
       for vertex in vertexSpan {
@@ -47,7 +47,7 @@ extension Megrez.Compositor {
       }
     }
 
-    let root = Vertex(node: .init(keyArray: ["_ROOT_"], keySeparator: separator))
+    let root = Vertex(node: .init(keyArray: ["_ROOT_"]))
     root.distance = 0
     root.edges.append(contentsOf: vertexSpans[0])
 
diff --git a/Packages/vChewing_Megrez/Sources/Megrez/3_KeyValuePaired.swift b/Packages/vChewing_Megrez/Sources/Megrez/3_KeyValuePaired.swift
index 54a3223f..f9db2329 100644
--- a/Packages/vChewing_Megrez/Sources/Megrez/3_KeyValuePaired.swift
+++ b/Packages/vChewing_Megrez/Sources/Megrez/3_KeyValuePaired.swift
@@ -7,49 +7,66 @@ import Foundation
 
 extension Megrez.Compositor {
   public struct KeyValuePaired: Equatable, Hashable, Comparable, CustomStringConvertible {
-    /// 鍵。一般情況下用來放置讀音等可以用來作為索引的內容。
-    public var key: String
+    /// 鍵陣列。一般情況下用來放置讀音等可以用來作為索引的內容。
+    public var keyArray: [String]
     /// 資料值。
     public var value: String
     /// 將當前鍵值列印成一個字串。
-    public var description: String { "(" + key + "," + value + ")" }
+    public var description: String { "(" + keyArray.description + "," + value + ")" }
     /// 判斷當前鍵值配對是否合規。如果鍵與值有任一為空，則結果為 false。
-    public var isValid: Bool { !key.isEmpty && !value.isEmpty }
+    public var isValid: Bool { !keyArray.joined().isEmpty && !value.isEmpty }
     /// 將當前鍵值列印成一個字串，但如果該鍵值配對為空的話則僅列印「()」。
-    public var toNGramKey: String { !isValid ? "()" : "(" + key + "," + value + ")" }
+    public var toNGramKey: String { !isValid ? "()" : "(" + joinedKey() + "," + value + ")" }
+
+    /// 初期化一組鍵值配對。
+    /// - Parameters:
+    ///   - key: 鍵陣列。一般情況下用來放置讀音等可以用來作為索引的內容。
+    ///   - value: 資料值。
+    public init(keyArray: [String], value: String = "N/A") {
+      self.keyArray = keyArray.isEmpty ? ["N/A"] : keyArray
+      self.value = value.isEmpty ? "N/A" : value
+    }
 
     /// 初期化一組鍵值配對。
     /// - Parameters:
     ///   - key: 鍵。一般情況下用來放置讀音等可以用來作為索引的內容。
     ///   - value: 資料值。
-    public init(key: String = "", value: String = "") {
-      self.key = key
-      self.value = value
+    public init(key: String = "N/A", value: String = "N/A") {
+      keyArray = key.isEmpty ? ["N/A"] : key.components(separatedBy: Megrez.Compositor.theSeparator)
+      self.value = value.isEmpty ? "N/A" : value
     }
 
     public func hash(into hasher: inout Hasher) {
-      hasher.combine(key)
+      hasher.combine(keyArray)
       hasher.combine(value)
     }
 
+    public func joinedKey(by separator: String = Megrez.Compositor.theSeparator) -> String {
+      keyArray.joined(separator: separator)
+    }
+
     public static func == (lhs: KeyValuePaired, rhs: KeyValuePaired) -> Bool {
-      lhs.key == rhs.key && lhs.value == rhs.value
+      lhs.keyArray == rhs.keyArray && lhs.value == rhs.value
     }
 
     public static func < (lhs: KeyValuePaired, rhs: KeyValuePaired) -> Bool {
-      (lhs.key.count < rhs.key.count) || (lhs.key.count == rhs.key.count && lhs.value < rhs.value)
+      (lhs.keyArray.joined().count < rhs.keyArray.joined().count)
+        || (lhs.keyArray.joined().count == rhs.keyArray.joined().count && lhs.value < rhs.value)
     }
 
     public static func > (lhs: KeyValuePaired, rhs: KeyValuePaired) -> Bool {
-      (lhs.key.count > rhs.key.count) || (lhs.key.count == rhs.key.count && lhs.value > rhs.value)
+      (lhs.keyArray.joined().count > rhs.keyArray.joined().count)
+        || (lhs.keyArray.joined().count == rhs.keyArray.joined().count && lhs.value > rhs.value)
     }
 
     public static func <= (lhs: KeyValuePaired, rhs: KeyValuePaired) -> Bool {
-      (lhs.key.count <= rhs.key.count) || (lhs.key.count == rhs.key.count && lhs.value <= rhs.value)
+      (lhs.keyArray.joined().count <= rhs.keyArray.joined().count)
+        || (lhs.keyArray.joined().count == rhs.keyArray.joined().count && lhs.value <= rhs.value)
     }
 
     public static func >= (lhs: KeyValuePaired, rhs: KeyValuePaired) -> Bool {
-      (lhs.key.count >= rhs.key.count) || (lhs.key.count == rhs.key.count && lhs.value >= rhs.value)
+      (lhs.keyArray.joined().count >= rhs.keyArray.joined().count)
+        || (lhs.keyArray.joined().count == rhs.keyArray.joined().count && lhs.value >= rhs.value)
     }
   }
 
@@ -70,7 +87,7 @@ extension Megrez.Compositor {
     }
     let keyAtCursor = keys[location]
     for theNode in anchors.map(\.node) {
-      if theNode.key.isEmpty { continue }
+      if theNode.keyArray.joined(separator: separator).isEmpty { continue }
       for gram in theNode.unigrams {
         switch filter {
           case .all:
@@ -81,7 +98,7 @@ extension Megrez.Compositor {
           case .endAt:
             if theNode.keyArray.reversed()[0] != keyAtCursor { continue }
         }
-        result.append(.init(key: theNode.key, value: gram.value))
+        result.append(.init(keyArray: theNode.keyArray, value: gram.value))
       }
     }
     return result
@@ -100,7 +117,7 @@ extension Megrez.Compositor {
   )
     -> Bool
   {
-    overrideCandidateAgainst(key: candidate.key, at: location, value: candidate.value, type: overrideType)
+    overrideCandidateAgainst(keyArray: candidate.keyArray, at: location, value: candidate.value, type: overrideType)
   }
 
   /// 使用給定的候選字詞字串，將給定位置的節點的候選字詞改為與之一致的候選字詞。
@@ -115,7 +132,7 @@ extension Megrez.Compositor {
     _ candidate: String,
     at location: Int, overrideType: Node.OverrideType = .withHighScore
   ) -> Bool {
-    overrideCandidateAgainst(key: nil, at: location, value: candidate, type: overrideType)
+    overrideCandidateAgainst(keyArray: nil, at: location, value: candidate, type: overrideType)
   }
 
   // MARK: Internal implementations.
@@ -127,14 +144,18 @@ extension Megrez.Compositor {
   ///   - value: 資料值。
   ///   - type: 指定覆寫行為。
   /// - Returns: 該操作是否成功執行。
-  internal func overrideCandidateAgainst(key: String?, at location: Int, value: String, type: Node.OverrideType)
+  internal func overrideCandidateAgainst(keyArray: [String]?, at location: Int, value: String, type: Node.OverrideType)
     -> Bool
   {
     let location = max(min(location, keys.count), 0)  // 防呆
     var arrOverlappedNodes: [NodeAnchor] = fetchOverlappingNodes(at: min(keys.count - 1, location))
     var overridden: NodeAnchor?
     for anchor in arrOverlappedNodes {
-      if let key = key, anchor.node.key != key { continue }
+      if let keyArray = keyArray,
+        anchor.node.keyArray.joined(separator: separator) != keyArray.joined(separator: separator)
+      {
+        continue
+      }
       if anchor.node.selectOverrideUnigram(value: value, type: type) {
         overridden = anchor
         break
@@ -150,7 +171,9 @@ extension Megrez.Compositor {
       arrOverlappedNodes = fetchOverlappingNodes(at: i)
       for anchor in arrOverlappedNodes {
         if anchor.node == overridden.node { continue }
-        if !overridden.node.key.contains(anchor.node.key) || !overridden.node.value.contains(anchor.node.value) {
+        if !overridden.node.keyArray.joined(separator: separator).contains(
+          anchor.node.keyArray.joined(separator: separator)) || !overridden.node.value.contains(anchor.node.value)
+        {
           anchor.node.reset()
           continue
         }
diff --git a/Packages/vChewing_Megrez/Sources/Megrez/6_Node.swift b/Packages/vChewing_Megrez/Sources/Megrez/6_Node.swift
index 78fa31ea..a7d38a03 100644
--- a/Packages/vChewing_Megrez/Sources/Megrez/6_Node.swift
+++ b/Packages/vChewing_Megrez/Sources/Megrez/6_Node.swift
@@ -34,7 +34,8 @@ extension Megrez.Compositor {
     /// 數（比如野獸常數），以讓「c」更容易單獨被選中。
     public var overridingScore: Double = 114_514
 
-    public private(set) var key: String
+    // public var key: String { keyArray.joined(separator: Megrez.Compositor.theSeparator) }
+
     public private(set) var keyArray: [String]
     public private(set) var spanLength: Int
     public private(set) var unigrams: [Megrez.Unigram]
@@ -42,10 +43,10 @@ extension Megrez.Compositor {
       didSet { currentUnigramIndex = max(min(unigrams.count - 1, currentUnigramIndex), 0) }
     }
 
-    public var currentPair: Megrez.Compositor.KeyValuePaired { .init(key: key, value: value) }
+    public var currentPair: Megrez.Compositor.KeyValuePaired { .init(keyArray: keyArray, value: value) }
 
     public func hash(into hasher: inout Hasher) {
-      hasher.combine(key)
+      hasher.combine(keyArray)
       hasher.combine(spanLength)
       hasher.combine(unigrams)
       hasher.combine(currentUnigramIndex)
@@ -68,14 +69,11 @@ extension Megrez.Compositor {
     public private(set) var overrideType: Node.OverrideType
 
     public static func == (lhs: Node, rhs: Node) -> Bool {
-      lhs.key == rhs.key && lhs.spanLength == rhs.spanLength
+      lhs.keyArray == rhs.keyArray && lhs.spanLength == rhs.spanLength
         && lhs.unigrams == rhs.unigrams && lhs.overrideType == rhs.overrideType
     }
 
-    public init(
-      keyArray: [String] = [], spanLength: Int = 0, unigrams: [Megrez.Unigram] = [], keySeparator: String = ""
-    ) {
-      key = keyArray.joined(separator: keySeparator)
+    public init(keyArray: [String] = [], spanLength: Int = 0, unigrams: [Megrez.Unigram] = []) {
       self.keyArray = keyArray
       self.spanLength = spanLength
       self.unigrams = unigrams
@@ -112,6 +110,10 @@ extension Megrez.Compositor {
       overrideType = .withNoOverrides
     }
 
+    public func joinedKey(by separator: String = Megrez.Compositor.theSeparator) -> String {
+      keyArray.joined(separator: separator)
+    }
+
     public func selectOverrideUnigram(value: String, type: Node.OverrideType) -> Bool {
       guard type != .withNoOverrides else {
         return false
@@ -136,7 +138,7 @@ extension Megrez.Compositor {
     let spanIndex: Int  // 幅位座標
     var spanLength: Int { node.spanLength }
     var unigrams: [Megrez.Unigram] { node.unigrams }
-    var key: String { node.key }
+    var keyArray: [String] { node.keyArray }
     var value: String { node.value }
 
     /// 將該節錨雜湊化。
@@ -154,7 +156,12 @@ extension Array where Element == Megrez.Compositor.Node {
   public var values: [String] { map(\.value) }
 
   /// 從一個節點陣列當中取出目前的索引鍵陣列。
-  public var keys: [String] { map(\.key) }
+  public func joinedKeys(by separator: String = Megrez.Compositor.theSeparator) -> [String] {
+    map { $0.keyArray.lazy.joined(separator: separator) }
+  }
+
+  /// 從一個節點陣列當中取出目前的索引鍵陣列。
+  public var keyArrays: [[String]] { map(\.keyArray) }
 
   /// 返回一連串的節點起點。結果為 (Result A, Result B) 辭典陣列
   /// Result A 以索引查座標，Result B 以座標查索引。
diff --git a/Packages/vChewing_Megrez/Sources/Megrez/7_LangModel.swift b/Packages/vChewing_Megrez/Sources/Megrez/7_LangModel.swift
index b08a6ed0..9c975148 100644
--- a/Packages/vChewing_Megrez/Sources/Megrez/7_LangModel.swift
+++ b/Packages/vChewing_Megrez/Sources/Megrez/7_LangModel.swift
@@ -5,10 +5,10 @@
 
 /// 語言模組協定。
 public protocol LangModelProtocol {
-  /// 給定鍵，讓語言模型找給一組單元圖陣列。
-  func unigramsFor(key: String) -> [Megrez.Unigram]
-  /// 給定鍵，確認是否有單元圖記錄在庫。
-  func hasUnigramsFor(key: String) -> Bool
+  /// 給定鍵陣列，讓語言模型找給一組單元圖陣列。
+  func unigramsFor(keyArray: [String]) -> [Megrez.Unigram]
+  /// 給定鍵陣列，確認是否有單元圖記錄在庫。
+  func hasUnigramsFor(keyArray: [String]) -> Bool
 }
 
 extension Megrez.Compositor {
@@ -24,15 +24,15 @@ extension Megrez.Compositor {
     /// 給定索引鍵，讓語言模型找給一組經過穩定排序的單元圖陣列。
     /// - Parameter key: 給定的索引鍵字串。
     /// - Returns: 對應的經過穩定排序的單元圖陣列。
-    public func unigramsFor(key: String) -> [Megrez.Unigram] {
-      langModel.unigramsFor(key: key).stableSorted { $0.score > $1.score }
+    public func unigramsFor(keyArray: [String]) -> [Megrez.Unigram] {
+      langModel.unigramsFor(keyArray: keyArray).stableSorted { $0.score > $1.score }
     }
 
     /// 根據給定的索引鍵來確認各個資料庫陣列內是否存在對應的資料。
     /// - Parameter key: 索引鍵。
     /// - Returns: 是否在庫。
-    public func hasUnigramsFor(key: String) -> Bool {
-      langModel.hasUnigramsFor(key: key)
+    public func hasUnigramsFor(keyArray: [String]) -> Bool {
+      langModel.hasUnigramsFor(keyArray: keyArray)
     }
   }
 }
diff --git a/Packages/vChewing_Megrez/Tests/MegrezTests/LMDataForTests.swift b/Packages/vChewing_Megrez/Tests/MegrezTests/LMDataForTests.swift
index d89de536..6da9e48b 100644
--- a/Packages/vChewing_Megrez/Tests/MegrezTests/LMDataForTests.swift
+++ b/Packages/vChewing_Megrez/Tests/MegrezTests/LMDataForTests.swift
@@ -25,16 +25,16 @@ class SimpleLM: LangModelProtocol {
     }
   }
 
-  func unigramsFor(key: String) -> [Megrez.Unigram] {
-    if let f = mutDatabase[key] {
+  func unigramsFor(keyArray: [String]) -> [Megrez.Unigram] {
+    if let f = mutDatabase[keyArray.joined()] {
       return f
     } else {
       return [Megrez.Unigram]().sorted { $0.score > $1.score }
     }
   }
 
-  func hasUnigramsFor(key: String) -> Bool {
-    mutDatabase.keys.contains(key)
+  func hasUnigramsFor(keyArray: [String]) -> Bool {
+    mutDatabase.keys.contains(keyArray.joined())
   }
 
   func trim(key: String, value: String) {
@@ -46,12 +46,12 @@ class SimpleLM: LangModelProtocol {
 }
 
 class MockLM: LangModelProtocol {
-  func unigramsFor(key: String) -> [Megrez.Unigram] {
-    [Megrez.Unigram(value: key, score: -1)]
+  func unigramsFor(keyArray: [String]) -> [Megrez.Unigram] {
+    [Megrez.Unigram(value: keyArray.joined(), score: -1)]
   }
 
-  func hasUnigramsFor(key: String) -> Bool {
-    !key.isEmpty
+  func hasUnigramsFor(keyArray: [String]) -> Bool {
+    !keyArray.isEmpty
   }
 }
 
diff --git a/Packages/vChewing_Megrez/Tests/MegrezTests/MegrezTests.swift b/Packages/vChewing_Megrez/Tests/MegrezTests/MegrezTests.swift
index 8ec5c7a1..ad1077e9 100644
--- a/Packages/vChewing_Megrez/Tests/MegrezTests/MegrezTests.swift
+++ b/Packages/vChewing_Megrez/Tests/MegrezTests/MegrezTests.swift
@@ -12,9 +12,11 @@ final class MegrezTests: XCTestCase {
   func testSpan() throws {
     let langModel = SimpleLM(input: strSampleData)
     let span = Megrez.Compositor.Span()
-    let n1 = Megrez.Compositor.Node(keyArray: ["gao1"], spanLength: 1, unigrams: langModel.unigramsFor(key: "gao1"))
+    let n1 = Megrez.Compositor.Node(
+      keyArray: ["gao1"], spanLength: 1, unigrams: langModel.unigramsFor(keyArray: ["gao1"])
+    )
     let n3 = Megrez.Compositor.Node(
-      keyArray: ["gao1ke1ji4"], spanLength: 3, unigrams: langModel.unigramsFor(key: "gao1ke1ji4")
+      keyArray: ["gao1ke1ji4"], spanLength: 3, unigrams: langModel.unigramsFor(keyArray: ["gao1ke1ji4"])
     )
     XCTAssertEqual(span.maxLength, 0)
     span.append(node: n1)
@@ -50,19 +52,19 @@ final class MegrezTests: XCTestCase {
 
   func testRankedLangModel() throws {
     class TestLM: LangModelProtocol {
-      func hasUnigramsFor(key: String) -> Bool { key == "foo" }
-      func unigramsFor(key: String) -> [Megrez.Unigram] {
-        key == "foo"
+      func hasUnigramsFor(keyArray: [String]) -> Bool { keyArray == ["foo"] }
+      func unigramsFor(keyArray: [String]) -> [Megrez.Unigram] {
+        keyArray == ["foo"]
           ? [.init(value: "middle", score: -5), .init(value: "highest", score: -2), .init(value: "lowest", score: -10)]
           : .init()
       }
     }
 
     let lmRanked = Megrez.Compositor.LangModelRanked(withLM: TestLM())
-    XCTAssertTrue(lmRanked.hasUnigramsFor(key: "foo"))
-    XCTAssertFalse(lmRanked.hasUnigramsFor(key: "bar"))
-    XCTAssertTrue(lmRanked.unigramsFor(key: "bar").isEmpty)
-    let unigrams = lmRanked.unigramsFor(key: "foo")
+    XCTAssertTrue(lmRanked.hasUnigramsFor(keyArray: ["foo"]))
+    XCTAssertFalse(lmRanked.hasUnigramsFor(keyArray: ["bar"]))
+    XCTAssertTrue(lmRanked.unigramsFor(keyArray: ["bar"]).isEmpty)
+    let unigrams = lmRanked.unigramsFor(keyArray: ["foo"])
     XCTAssertEqual(unigrams.count, 3)
     XCTAssertEqual(unigrams[0].value, "highest")
     XCTAssertEqual(unigrams[0].score, -2)
@@ -74,7 +76,7 @@ final class MegrezTests: XCTestCase {
 
   func testCompositor_BasicTests() throws {
     var compositor = Megrez.Compositor(with: MockLM())
-    XCTAssertEqual(compositor.separator, Megrez.Compositor.kDefaultSeparator)
+    XCTAssertEqual(compositor.separator, Megrez.Compositor.theSeparator)
     XCTAssertEqual(compositor.cursor, 0)
     XCTAssertEqual(compositor.length, 0)
 
@@ -87,7 +89,7 @@ final class MegrezTests: XCTestCase {
       print("fuckme")
       return
     }
-    XCTAssertEqual(zeroNode.key, "a")
+    XCTAssertEqual(zeroNode.keyArray.joined(separator: compositor.separator), "a")
 
     compositor.dropKey(direction: .rear)
     XCTAssertEqual(compositor.cursor, 0)
@@ -97,9 +99,9 @@ final class MegrezTests: XCTestCase {
 
   func testCompositor_InvalidOperations() throws {
     class TestLM: LangModelProtocol {
-      func hasUnigramsFor(key: String) -> Bool { key == "foo" }
-      func unigramsFor(key: String) -> [Megrez.Unigram] {
-        key == "foo" ? [.init(value: "foo", score: -1)] : .init()
+      func hasUnigramsFor(keyArray: [String]) -> Bool { keyArray == ["foo"] }
+      func unigramsFor(keyArray: [String]) -> [Megrez.Unigram] {
+        keyArray == ["foo"] ? [.init(value: "foo", score: -1)] : .init()
       }
     }
 
@@ -146,14 +148,14 @@ final class MegrezTests: XCTestCase {
     XCTAssertEqual(compositor.length, 3)
     XCTAssertEqual(compositor.spans.count, 3)
     XCTAssertEqual(compositor.spans[0].maxLength, 3)
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.key, "a")
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.key, "a;b")
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 3)?.key, "a;b;c")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "a")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.keyArray.joined(separator: compositor.separator), "a;b")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 3)?.keyArray.joined(separator: compositor.separator), "a;b;c")
     XCTAssertEqual(compositor.spans[1].maxLength, 2)
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.key, "b")
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 2)?.key, "b;c")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "b")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 2)?.keyArray.joined(separator: compositor.separator), "b;c")
     XCTAssertEqual(compositor.spans[2].maxLength, 1)
-    XCTAssertEqual(compositor.spans[2].nodeOf(length: 1)?.key, "c")
+    XCTAssertEqual(compositor.spans[2].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "c")
   }
 
   func testCompositor_SpanDeletionFromFront() throws {
@@ -168,10 +170,10 @@ final class MegrezTests: XCTestCase {
     XCTAssertEqual(compositor.length, 2)
     XCTAssertEqual(compositor.spans.count, 2)
     XCTAssertEqual(compositor.spans[0].maxLength, 2)
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.key, "a")
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.key, "a;b")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "a")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.keyArray.joined(separator: compositor.separator), "a;b")
     XCTAssertEqual(compositor.spans[1].maxLength, 1)
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.key, "b")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "b")
   }
 
   func testCompositor_SpanDeletionFromMiddle() throws {
@@ -187,10 +189,10 @@ final class MegrezTests: XCTestCase {
     XCTAssertEqual(compositor.length, 2)
     XCTAssertEqual(compositor.spans.count, 2)
     XCTAssertEqual(compositor.spans[0].maxLength, 2)
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.key, "a")
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.key, "a;c")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "a")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.keyArray.joined(separator: compositor.separator), "a;c")
     XCTAssertEqual(compositor.spans[1].maxLength, 1)
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.key, "c")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "c")
 
     compositor.clear()
     compositor.insertKey("a")
@@ -203,10 +205,10 @@ final class MegrezTests: XCTestCase {
     XCTAssertEqual(compositor.length, 2)
     XCTAssertEqual(compositor.spans.count, 2)
     XCTAssertEqual(compositor.spans[0].maxLength, 2)
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.key, "a")
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.key, "a;c")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "a")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.keyArray.joined(separator: compositor.separator), "a;c")
     XCTAssertEqual(compositor.spans[1].maxLength, 1)
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.key, "c")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "c")
   }
 
   func testCompositor_SpanDeletionFromRear() throws {
@@ -223,10 +225,10 @@ final class MegrezTests: XCTestCase {
     XCTAssertEqual(compositor.length, 2)
     XCTAssertEqual(compositor.spans.count, 2)
     XCTAssertEqual(compositor.spans[0].maxLength, 2)
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.key, "b")
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.key, "b;c")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "b")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.keyArray.joined(separator: compositor.separator), "b;c")
     XCTAssertEqual(compositor.spans[1].maxLength, 1)
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.key, "c")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "c")
   }
 
   func testCompositor_SpanInsertion() throws {
@@ -242,19 +244,19 @@ final class MegrezTests: XCTestCase {
     XCTAssertEqual(compositor.length, 4)
     XCTAssertEqual(compositor.spans.count, 4)
     XCTAssertEqual(compositor.spans[0].maxLength, 4)
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.key, "a")
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.key, "a;X")
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 3)?.key, "a;X;b")
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 4)?.key, "a;X;b;c")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "a")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 2)?.keyArray.joined(separator: compositor.separator), "a;X")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 3)?.keyArray.joined(separator: compositor.separator), "a;X;b")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 4)?.keyArray.joined(separator: compositor.separator), "a;X;b;c")
     XCTAssertEqual(compositor.spans[1].maxLength, 3)
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.key, "X")
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 2)?.key, "X;b")
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 3)?.key, "X;b;c")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "X")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 2)?.keyArray.joined(separator: compositor.separator), "X;b")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 3)?.keyArray.joined(separator: compositor.separator), "X;b;c")
     XCTAssertEqual(compositor.spans[2].maxLength, 2)
-    XCTAssertEqual(compositor.spans[2].nodeOf(length: 1)?.key, "b")
-    XCTAssertEqual(compositor.spans[2].nodeOf(length: 2)?.key, "b;c")
+    XCTAssertEqual(compositor.spans[2].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "b")
+    XCTAssertEqual(compositor.spans[2].nodeOf(length: 2)?.keyArray.joined(separator: compositor.separator), "b;c")
     XCTAssertEqual(compositor.spans[3].maxLength, 1)
-    XCTAssertEqual(compositor.spans[3].nodeOf(length: 1)?.key, "c")
+    XCTAssertEqual(compositor.spans[3].nodeOf(length: 1)?.keyArray.joined(separator: compositor.separator), "c")
   }
 
   func testCompositor_LongGridDeletion() throws {
@@ -279,17 +281,17 @@ final class MegrezTests: XCTestCase {
     XCTAssertEqual(compositor.cursor, 6)
     XCTAssertEqual(compositor.length, 13)
     XCTAssertEqual(compositor.spans.count, 13)
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 6)?.key, "abcdef")
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 6)?.key, "bcdefh")
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 5)?.key, "bcdef")
-    XCTAssertEqual(compositor.spans[2].nodeOf(length: 6)?.key, "cdefhi")
-    XCTAssertEqual(compositor.spans[2].nodeOf(length: 5)?.key, "cdefh")
-    XCTAssertEqual(compositor.spans[3].nodeOf(length: 6)?.key, "defhij")
-    XCTAssertEqual(compositor.spans[4].nodeOf(length: 6)?.key, "efhijk")
-    XCTAssertEqual(compositor.spans[5].nodeOf(length: 6)?.key, "fhijkl")
-    XCTAssertEqual(compositor.spans[6].nodeOf(length: 6)?.key, "hijklm")
-    XCTAssertEqual(compositor.spans[7].nodeOf(length: 6)?.key, "ijklmn")
-    XCTAssertEqual(compositor.spans[8].nodeOf(length: 5)?.key, "jklmn")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "abcdef")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "bcdefh")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 5)?.keyArray.joined(separator: compositor.separator), "bcdef")
+    XCTAssertEqual(compositor.spans[2].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "cdefhi")
+    XCTAssertEqual(compositor.spans[2].nodeOf(length: 5)?.keyArray.joined(separator: compositor.separator), "cdefh")
+    XCTAssertEqual(compositor.spans[3].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "defhij")
+    XCTAssertEqual(compositor.spans[4].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "efhijk")
+    XCTAssertEqual(compositor.spans[5].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "fhijkl")
+    XCTAssertEqual(compositor.spans[6].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "hijklm")
+    XCTAssertEqual(compositor.spans[7].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "ijklmn")
+    XCTAssertEqual(compositor.spans[8].nodeOf(length: 5)?.keyArray.joined(separator: compositor.separator), "jklmn")
   }
 
   func testCompositor_LongGridInsertion() throws {
@@ -314,19 +316,19 @@ final class MegrezTests: XCTestCase {
     XCTAssertEqual(compositor.cursor, 8)
     XCTAssertEqual(compositor.length, 15)
     XCTAssertEqual(compositor.spans.count, 15)
-    XCTAssertEqual(compositor.spans[0].nodeOf(length: 6)?.key, "abcdef")
-    XCTAssertEqual(compositor.spans[1].nodeOf(length: 6)?.key, "bcdefg")
-    XCTAssertEqual(compositor.spans[2].nodeOf(length: 6)?.key, "cdefgX")
-    XCTAssertEqual(compositor.spans[3].nodeOf(length: 6)?.key, "defgXh")
-    XCTAssertEqual(compositor.spans[3].nodeOf(length: 5)?.key, "defgX")
-    XCTAssertEqual(compositor.spans[4].nodeOf(length: 6)?.key, "efgXhi")
-    XCTAssertEqual(compositor.spans[4].nodeOf(length: 5)?.key, "efgXh")
-    XCTAssertEqual(compositor.spans[4].nodeOf(length: 4)?.key, "efgX")
-    XCTAssertEqual(compositor.spans[4].nodeOf(length: 3)?.key, "efg")
-    XCTAssertEqual(compositor.spans[5].nodeOf(length: 6)?.key, "fgXhij")
-    XCTAssertEqual(compositor.spans[6].nodeOf(length: 6)?.key, "gXhijk")
-    XCTAssertEqual(compositor.spans[7].nodeOf(length: 6)?.key, "Xhijkl")
-    XCTAssertEqual(compositor.spans[8].nodeOf(length: 6)?.key, "hijklm")
+    XCTAssertEqual(compositor.spans[0].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "abcdef")
+    XCTAssertEqual(compositor.spans[1].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "bcdefg")
+    XCTAssertEqual(compositor.spans[2].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "cdefgX")
+    XCTAssertEqual(compositor.spans[3].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "defgXh")
+    XCTAssertEqual(compositor.spans[3].nodeOf(length: 5)?.keyArray.joined(separator: compositor.separator), "defgX")
+    XCTAssertEqual(compositor.spans[4].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "efgXhi")
+    XCTAssertEqual(compositor.spans[4].nodeOf(length: 5)?.keyArray.joined(separator: compositor.separator), "efgXh")
+    XCTAssertEqual(compositor.spans[4].nodeOf(length: 4)?.keyArray.joined(separator: compositor.separator), "efgX")
+    XCTAssertEqual(compositor.spans[4].nodeOf(length: 3)?.keyArray.joined(separator: compositor.separator), "efg")
+    XCTAssertEqual(compositor.spans[5].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "fgXhij")
+    XCTAssertEqual(compositor.spans[6].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "gXhijk")
+    XCTAssertEqual(compositor.spans[7].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "Xhijkl")
+    XCTAssertEqual(compositor.spans[8].nodeOf(length: 6)?.keyArray.joined(separator: compositor.separator), "hijklm")
   }
 
   func testCompositor_StressBench() throws {
@@ -349,7 +351,7 @@ final class MegrezTests: XCTestCase {
       compositor.insertKey(String(i))
     }
     let result = compositor.walk().0
-    XCTAssertEqual(result.keys, ["高科技", "公司", "的", "年終", "獎金"])
+    XCTAssertEqual(result.joinedKeys(by: ""), ["高科技", "公司", "的", "年終", "獎金"])
   }
 
   func testCompositor_InputTestAndCursorJump() throws {
@@ -510,11 +512,11 @@ final class MegrezTests: XCTestCase {
     XCTAssertEqual(result.values, ["高熱", "火焰", "危險"])
     let location = 2
 
-    XCTAssertTrue(compositor.overrideCandidate(.init(key: "huo3", value: "🔥"), at: location))
+    XCTAssertTrue(compositor.overrideCandidate(.init(keyArray: ["huo3"], value: "🔥"), at: location))
     result = compositor.walk().0
     XCTAssertEqual(result.values, ["高熱", "🔥", "焰", "危險"])
 
-    XCTAssertTrue(compositor.overrideCandidate(.init(key: "huo3yan4", value: "🔥"), at: location))
+    XCTAssertTrue(compositor.overrideCandidate(.init(keyArray: ["huo3", "yan4"], value: "🔥"), at: location))
     result = compositor.walk().0
     XCTAssertEqual(result.values, ["高熱", "🔥", "危險"])
   }