diff --git a/Core/Sources/ConverterServer/ConverterServer+KeyEvent.swift b/Core/Sources/ConverterServer/ConverterServer+KeyEvent.swift
index 56cba218..b4837ce2 100644
--- a/Core/Sources/ConverterServer/ConverterServer+KeyEvent.swift
+++ b/Core/Sources/ConverterServer/ConverterServer+KeyEvent.swift
@@ -373,6 +373,10 @@ extension ConverterServer {
         guard !prediction.appendText.isEmpty else {
             return
         }
+        if let candidate = prediction.candidate {
+            // 読みを補完する前に伝える。補完後の再変換で候補の表記が先頭の制約になる
+            manager.acceptPredictionCandidate(candidate)
+        }
         manager.insertAtCursorPosition(prediction.appendText, inputStyle: .direct)
     }
 }
diff --git a/Core/Sources/Core/InputUtils/SegmentsManager.swift b/Core/Sources/Core/InputUtils/SegmentsManager.swift
index 3188ca36..5cb442ee 100644
--- a/Core/Sources/Core/InputUtils/SegmentsManager.swift
+++ b/Core/Sources/Core/InputUtils/SegmentsManager.swift
@@ -65,6 +65,8 @@ public final class SegmentsManager {
         public var displayText: String
         public var appendText: String
         public var deleteCount: Int = 0
+        /// 表示のもとになった変換器の候補。受け入れたことを変換器へ伝えるのに使う
+        public var candidate: Candidate?
     }
 
     struct BackspaceTypoCorrectionLock: Sendable {
@@ -861,6 +863,11 @@ public final class SegmentsManager {
         return [backspaceAdjustedPredictionCandidate]
     }
 
+    /// 予測候補を受け入れたことを変換器へ伝える。以降の変換では、その候補の表記が先頭の制約になる
+    public func acceptPredictionCandidate(_ candidate: Candidate) {
+        self.kanaKanjiConverter.setPrefixCandidate(candidate)
+    }
+
     public static func preferredPredictionCandidates(
         typoCorrectionCandidates: [PredictionCandidate],
         predictionCandidates: [PredictionCandidate]
@@ -898,11 +905,12 @@ public final class SegmentsManager {
             guard !reading.isEmpty else {
                 continue
             }
-            if let predictionCandidate = Self.makePredictionCandidate(
+            if var predictionCandidate = Self.makePredictionCandidate(
                 currentTarget: target,
                 candidateReading: reading,
                 displayText: candidate.text
             ) {
+                predictionCandidate.candidate = candidate
                 return [predictionCandidate]
             }
         }