azooKey · sinoda1114 · Sep 6, 2026
diff --git a/Core/Sources/Core/InputUtils/KatakanaEnglishCandidates.swift b/Core/Sources/Core/InputUtils/KatakanaEnglishCandidates.swift
@@ -0,0 +1,135 @@
+/// カタカナで入力した外来語から、対応する英単語の綴りを候補に追加する。
+///
+/// 機械的なローマ字化ではなく、一般的な英語表記だけを明示的に登録する。
+enum KatakanaEnglishCandidates {
+    private static let words: [String: String] = [
+        // 日常で使う物・場所
+        "ベッド": "bed",
+        "ボトル": "bottle",
+        "カメラ": "camera",
+        "カード": "card",
+        "コーヒー": "coffee",
+        "ドア": "door",
+        "ドレス": "dress",
+        "エレベーター": "elevator",
+        "フード": "food",
+        "ホテル": "hotel",
+        "アイスクリーム": "ice cream",
+        "ジャケット": "jacket",
+        "キッチン": "kitchen",
+        "ランチ": "lunch",
+        "マップ": "map",
+        "メニュー": "menu",
+        "ミラー": "mirror",
+        "オフィス": "office",
+        "パスポート": "passport",
+        "ペン": "pen",
+        "ピザ": "pizza",
+        "レストラン": "restaurant",
+        "シャツ": "shirt",
+        "ショップ": "shop",
+        "ソファ": "sofa",
+        "スーツ": "suit",
+        "タクシー": "taxi",
+        "チケット": "ticket",
+        "トイレ": "toilet",
+        "トレイン": "train",
+        "バス": "bus",
+        "ウォーター": "water",
+        "ウィンドウ": "window",
+
+        // デジタル作業
+        "アクセス": "access",
+        "アカウント": "account",
+        "アプリ": "app",
+        "アップデート": "update",
+        "アップロード": "upload",
+        "ブラウザ": "browser",
+        "クリック": "click",
+        "コード": "code",
+        "コンテンツ": "content",
+        "データ": "data",
+        "デバッグ": "debug",
+        "デバイス": "device",
+        "ディスプレイ": "display",
+        "ドキュメント": "document",
+        "ダウンロード": "download",
+        "エラー": "error",
+        "ファイル": "file",
+        "フォルダ": "folder",
+        "インストール": "install",
+        "インターフェース": "interface",
+        "インターネット": "internet",
+        "キーボード": "keyboard",
+        "リンク": "link",
+        "ログイン": "login",
+        "マウス": "mouse",
+        "ネットワーク": "network",
+        "オプション": "option",
+        "パスワード": "password",
+        "プライバシー": "privacy",
+        "プログラム": "program",
+        "プロジェクト": "project",
+        "リリース": "release",
+        "セキュリティ": "security",
+        "サーバー": "server",
+        "サービス": "service",
+        "ソフトウェア": "software",
+        "スマートフォン": "smartphone",
+        "システム": "system",
+        "タブ": "tab",
+        "テキスト": "text",
+        "ユーザー": "user",
+        "バージョン": "version",
+        "ウェブ": "web",
+        "ウェブサイト": "website",
+
+        // 仕事・コミュニケーション
+        "アジェンダ": "agenda",
+        "アポイントメント": "appointment",
+        "ミーティング": "meeting",
+        "メッセージ": "message",
+        "メール": "email",
+        "プレゼンテーション": "presentation",
+        "レポート": "report",
+        "スケジュール": "schedule",
+        "タスク": "task",
+        "チーム": "team",
+
+        // よく使う一般語
+        "アイデア": "idea",
+        "アイコン": "icon",
+        "イメージ": "image",
+        "イベント": "event",
+        "ゲーム": "game",
+        "グループ": "group",
+        "キーワード": "keyword",
+        "ラベル": "label",
+        "レイアウト": "layout",
+        "リスト": "list",
+        "モデル": "model",
+        "ニュース": "news",
+        "ページ": "page",
+        "パターン": "pattern",
+        "プラン": "plan",
+        "ポイント": "point",
+        "ポリシー": "policy",
+        "レスポンス": "response",
+        "ルール": "rule",
+        "サンプル": "sample",
+        "サイズ": "size",
+        "スタイル": "style",
+        "タイトル": "title",
+        "トピック": "topic",
+        "タイプ": "type",
+        "ワーク": "work"
+    ]
+
+    static func variants(for reading: String) -> [String] {
+        guard let word = Self.words[reading] else {
+            return []
+        }
+        let title = word.prefix(1).uppercased() + word.dropFirst()
+        return title == word ? [word] : [word, title]
+    }
+}
diff --git a/Core/Sources/Core/InputUtils/SegmentsManager.swift b/Core/Sources/Core/InputUtils/SegmentsManager.swift
@@ -564,7 +564,7 @@ public final class SegmentsManager {
 
         let leftSideContext = forcedLeftSideContext ?? self.getCleanLeftSideContext(maxCount: ContextLength.conversion)
         let rightSideContext = forcedRightSideContext ?? self.getCleanRightSideContext(maxCount: ContextLength.conversion)
-        let result = self.kanaKanjiConverter.requestCandidates(
+        var result = self.kanaKanjiConverter.requestCandidates(
             self.composingText,
             options: options(
                 leftSideContext: leftSideContext,
@@ -574,6 +574,27 @@ public final class SegmentsManager {
                 requireEnglishPrediction: Config.DebugPredictiveTyping().value ? .manualMix : .disabled
             )
         )
+        if self.composingText.isAtEndIndex {
+            let reading = self.composingText.convertTarget.toKatakana()
+            let englishWords = KatakanaEnglishCandidates.variants(for: reading)
+            if !englishWords.isEmpty {
+                var seen = Set(result.mainResults.map(\.text))
+                let candidates = englishWords.compactMap { word -> Candidate? in
+                    guard seen.insert(word).inserted else {
+                        return nil
+                    }
+                    return Candidate(
+                        text: word,
+                        value: -18,
+                        composingCount: .surfaceCount(self.composingText.convertTarget.count),
+                        lastMid: MIDData.一般.mid,
+                        data: [.init(word: word, ruby: reading, cid: CIDData.固有名詞.cid, mid: MIDData.一般.mid, value: -18)],
+                        isLearningTarget: false
+                    )
+                }
+                result.mainResults.insert(contentsOf: candidates, at: min(5, result.mainResults.count))
+            }
+        }
         self.rawCandidates = result
     }
 

diff --git a/Core/Tests/CoreTests/InputUtilsTests/KatakanaEnglishCandidatesTests.swift b/Core/Tests/CoreTests/InputUtilsTests/KatakanaEnglishCandidatesTests.swift
@@ -0,0 +1,40 @@
+@testable import Core
+import Foundation
+import KanaKanjiConverterModuleWithDefaultDictionary
+import Testing
+
+struct KatakanaEnglishCandidatesTests {
+    @Test func returnsLowercaseAndSentenceCaseVariants() {
+        #expect(KatakanaEnglishCandidates.variants(for: "セキュリティ") == ["security", "Security"])
+        #expect(KatakanaEnglishCandidates.variants(for: "ディスプレイ") == ["display", "Display"])
+        #expect(KatakanaEnglishCandidates.variants(for: "スマートフォン") == ["smartphone", "Smartphone"])
+        #expect(KatakanaEnglishCandidates.variants(for: "ベッド") == ["bed", "Bed"])
+        #expect(KatakanaEnglishCandidates.variants(for: "マウス") == ["mouse", "Mouse"])
+        #expect(KatakanaEnglishCandidates.variants(for: "キーボード") == ["keyboard", "Keyboard"])
+        #expect(KatakanaEnglishCandidates.variants(for: "メール") == ["email", "Email"])
+    }
+
+    @Test func doesNotGuessUnknownKatakanaWords() {
+        #expect(KatakanaEnglishCandidates.variants(for: "アズーキー").isEmpty)
+    }
+
+    @MainActor @Test func insertsEnglishSpellingIntoConversionCandidates() {
+        let manager = SegmentsManager(
+            kanaKanjiConverter: .withDefaultDictionary(),
+            applicationDirectoryURL: URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true),
+            containerURL: nil,
+            context: .init(useZenzai: false)
+        )
+        manager.insertAtCursorPosition("セキュリティ", inputStyle: .direct)
+        manager.requestSetCandidateWindowState(visible: true)
+
+        switch manager.getCurrentCandidateWindow(inputState: .selecting) {
+        case .selecting(let candidates, _):
+            let texts = candidates.map(\.text)
+            #expect(texts.contains("security"))
+            #expect(texts.contains("Security"))
+        case .hidden, .composing:
+            Issue.record("Expected conversion candidates.")
+        }
+    }
+}