diff --git a/apps/client/src/hooks/useSocketSubscriptions.ts b/apps/client/src/hooks/useSocketSubscriptions.ts
index 19a2ef8..8d8009f 100644
--- a/apps/client/src/hooks/useSocketSubscriptions.ts
+++ b/apps/client/src/hooks/useSocketSubscriptions.ts
@@ -7,13 +7,14 @@
 import { socketManager } from "@client/network/SocketManager";
 import { domain } from "@repo/shared";
 import type { GameResultPayload } from "@repo/shared";
+import type { Dispatch, SetStateAction } from "react";
 
 type UseSocketSubscriptionsParams = {
   completeJoinRequest: () => void;
   setGameResult: (payload: GameResultPayload | null) => void;
   setMyId: (id: string | null) => void;
   setRoom: (room: domain.room.Room | null) => void;
-  setScenePhase: (phase: domain.app.ScenePhaseType) => void;
+  setScenePhase: Dispatch<SetStateAction<domain.app.ScenePhaseType>>;
 };
 
 type AppSocketHandlers = {
@@ -80,7 +81,16 @@
       handleRoomUpdate: (updatedRoom: domain.room.Room) => {
         completeJoinRequest();
         setRoom(updatedRoom);
-        setScenePhase(domain.app.ScenePhase.LOBBY);
+        setScenePhase((currentPhase) => {
+          if (
+            currentPhase === domain.app.ScenePhase.PLAYING ||
+            currentPhase === domain.app.ScenePhase.RESULT
+          ) {
+            return currentPhase;
+          }
+
+          return domain.app.ScenePhase.LOBBY;
+        });
       },
 
       handleGameStart: () => {
diff --git a/apps/server/src/domains/game/GameManager.ts b/apps/server/src/domains/game/GameManager.ts
index 128278b..4b0e499 100644
--- a/apps/server/src/domains/game/GameManager.ts
+++ b/apps/server/src/domains/game/GameManager.ts
@@ -48,6 +48,11 @@
     this.playerOperationService.removePlayer(id);
   }
 
+  // 切断プレイヤーをBot制御へ引き継ぐ
+  replaceDisconnectedPlayerWithBot(id: string): boolean {
+    return this.playerOperationService.replaceDisconnectedPlayerWithBot(id);
+  }
+
   // 指定プレイヤー座標更新処理
   movePlayer(id: string, x: number, y: number) {
     this.playerOperationService.movePlayer(id, x, y);
diff --git a/apps/server/src/domains/game/application/ports/gameUseCasePorts.ts b/apps/server/src/domains/game/application/ports/gameUseCasePorts.ts
index a5bd40d..0e247fc 100644
--- a/apps/server/src/domains/game/application/ports/gameUseCasePorts.ts
+++ b/apps/server/src/domains/game/application/ports/gameUseCasePorts.ts
@@ -44,6 +44,7 @@
 /** 切断ユースケースが利用するプレイヤー削除入力ポート */
 export interface DisconnectPlayerPort {
   removePlayer(id: string): void;
+  replaceDisconnectedPlayerWithBot(id: string): boolean;
 }
 
 /** ゲーム系ユースケースが利用する送信出力ポート */
diff --git a/apps/server/src/domains/game/application/services/GamePlayerOperationService.ts b/apps/server/src/domains/game/application/services/GamePlayerOperationService.ts
index 8367b1d..f2e3505 100644
--- a/apps/server/src/domains/game/application/services/GamePlayerOperationService.ts
+++ b/apps/server/src/domains/game/application/services/GamePlayerOperationService.ts
@@ -55,4 +55,18 @@
       });
     }
   }
+
+  public replaceDisconnectedPlayerWithBot(id: string): boolean {
+    const session = this.sessionRef.current;
+    if (!session || !this.activePlayerIds.has(id)) {
+      logEvent(logScopes.GAME_PLAYER_OPERATION_SERVICE, {
+        event: gameDomainLogEvents.PLAYER_REMOVE,
+        result: logResults.IGNORED_PLAYER_NOT_IN_SESSION,
+        socketId: id,
+      });
+      return false;
+    }
+
+    return session.promotePlayerToBotControl(id);
+  }
 }
\ No newline at end of file
diff --git a/apps/server/src/domains/game/application/services/GameRoomSession.ts b/apps/server/src/domains/game/application/services/GameRoomSession.ts
index 6b52829..cd90ba7 100644
--- a/apps/server/src/domains/game/application/services/GameRoomSession.ts
+++ b/apps/server/src/domains/game/application/services/GameRoomSession.ts
@@ -135,9 +135,20 @@
   }
 
   public removePlayer(id: string): boolean {
+    this.gameLoop?.releaseBotControl(id);
     return this.players.delete(id);
   }
 
+  /** 指定プレイヤーを切断後もBot制御で継続させる */
+  public promotePlayerToBotControl(id: string): boolean {
+    if (!this.players.has(id) || !this.gameLoop) {
+      return false;
+    }
+
+    this.gameLoop.promotePlayerToBotControl(id);
+    return true;
+  }
+
   public getStartTime(): number | undefined {
     return this.startTime;
   }
diff --git a/apps/server/src/domains/game/application/useCases/disconnectUseCase.ts b/apps/server/src/domains/game/application/useCases/disconnectUseCase.ts
index c762160..a7def6d 100644
--- a/apps/server/src/domains/game/application/useCases/disconnectUseCase.ts
+++ b/apps/server/src/domains/game/application/useCases/disconnectUseCase.ts
@@ -20,15 +20,20 @@
   playerId,
   output,
 }: DisconnectUseCaseParams) => {
-  gameManager.removePlayer(playerId);
+  const replacedWithBot = gameManager.replaceDisconnectedPlayerWithBot(playerId);
 
-  if (roomId) {
-    output.publishPlayerRemovedToRoom(roomId, playerId);
+  if (!replacedWithBot) {
+    gameManager.removePlayer(playerId);
+
+    if (roomId) {
+      output.publishPlayerRemovedToRoom(roomId, playerId);
+    }
   }
 
   logEvent(logScopes.GAME_USE_CASE, {
     event: gameUseCaseLogEvents.DISCONNECT,
     result: logResults.PLAYER_REMOVED,
     socketId: playerId,
+    replacedWithBot,
   });
 };
diff --git a/apps/server/src/domains/game/loop/GameLoop.ts b/apps/server/src/domains/game/loop/GameLoop.ts
index 35e3df8..403867b 100644
--- a/apps/server/src/domains/game/loop/GameLoop.ts
+++ b/apps/server/src/domains/game/loop/GameLoop.ts
@@ -13,7 +13,11 @@
   logResults,
   logScopes,
 } from "@server/logging/index";
-import { BotTurnOrchestrator, isBotPlayerId } from "../application/services/bot/index.js";
+import {
+  BotTurnOrchestrator,
+  isBotPlayerId,
+  type BotPlayerId,
+} from "../application/services/bot/index.js";
 import { setPlayerPosition } from "../entities/player/playerMovement.js";
 
 /** ルーム内ゲーム進行を定周期で実行するループ管理クラス */
@@ -26,6 +30,7 @@
   private readonly maxCatchUpTicks: number = 3;
   private lastSentPlayers: Map<string, domain.game.PlayerPositionUpdate> =
     new Map();
+  private disconnectedBotControlledPlayerIds: Set<string> = new Set();
   private botTurnOrchestrator: BotTurnOrchestrator =
     new BotTurnOrchestrator();
 
@@ -127,9 +132,12 @@
     gridColorsSnapshot: number[],
   ): void {
     this.players.forEach((player) => {
-      if (isBotPlayerId(player.id)) {
+      if (
+        isBotPlayerId(player.id) ||
+        this.disconnectedBotControlledPlayerIds.has(player.id)
+      ) {
         const decision = this.botTurnOrchestrator.decide(
-          player.id,
+          player.id as BotPlayerId,
           player,
           gridColorsSnapshot,
           nowMs,
@@ -147,14 +155,29 @@
   /** 指定プレイヤーがBotなら被弾硬直を適用する */
   public applyBotHitStun(playerId: string, nowMs: number): boolean {
     const player = this.players.get(playerId);
-    if (!player || !isBotPlayerId(player.id)) {
+    const isBotControlled =
+      !!player &&
+      (isBotPlayerId(player.id) ||
+        this.disconnectedBotControlledPlayerIds.has(player.id));
+
+    if (!isBotControlled) {
       return false;
     }
 
-    this.botTurnOrchestrator.applyHitStun(player.id, nowMs);
+    this.botTurnOrchestrator.applyHitStun(playerId as BotPlayerId, nowMs);
     return true;
   }
 
+  /** 切断プレイヤーをBot制御対象へ昇格する */
+  public promotePlayerToBotControl(playerId: string): void {
+    this.disconnectedBotControlledPlayerIds.add(playerId);
+  }
+
+  /** プレイヤー削除時にBot制御対象から除外する */
+  public releaseBotControl(playerId: string): void {
+    this.disconnectedBotControlledPlayerIds.delete(playerId);
+  }
+
   private buildTickData(): domain.game.TickData {
     const activePlayerIds = new Set<string>();
     const playerUpdates = this.collectChangedPlayerUpdates(activePlayerIds);
@@ -213,6 +236,7 @@
 
     this.isRunning = false;
     this.botTurnOrchestrator.clear();
+    this.disconnectedBotControlledPlayerIds.clear();
     this.lastSentPlayers.clear();
 
     if (this.loopId) {