diff --git a/apps/server/src/application/coordinators/disconnectCoordinator.ts b/apps/server/src/application/coordinators/disconnectCoordinator.ts
index 47df6fe..739dee6 100644
--- a/apps/server/src/application/coordinators/disconnectCoordinator.ts
+++ b/apps/server/src/application/coordinators/disconnectCoordinator.ts
@@ -16,11 +16,15 @@
 import { disconnectUseCase } from "@server/domains/game/application/useCases/disconnectUseCase";
 import { roomDisconnectUseCase } from "@server/domains/room/application/useCases/roomDisconnectUseCase";
 
+type DisconnectDeps = {
+  roomManager: DisconnectRoomPort & FindRoomByPlayerPort & FindRoomByIdPort;
+  runtimeRegistry: FindGameByPlayerPort & CleanupGameRuntimePort;
+};
+
 /** 切断調停で利用する入力ポートと出力ポートの契約 */
 export type DisconnectCoordinatorParams = {
   socketId: string;
-  roomManager: DisconnectRoomPort & FindRoomByPlayerPort & FindRoomByIdPort;
-  runtimeRegistry: FindGameByPlayerPort & CleanupGameRuntimePort;
+} & DisconnectDeps & {
   gameOutput: Pick<GameOutputPort, "publishPlayerRemovedToRoom">;
   roomOutput: Pick<RoomOutputPort, "publishRoomUpdateToRoom">;
 };
@@ -47,9 +51,8 @@
 
   roomDisconnectUseCase({
     roomManager,
+    runtimeRegistry,
     socketId,
     output: roomOutput,
   });
-
-  runtimeRegistry.cleanupDisposedRoomRuntimes();
 };
diff --git a/apps/server/src/application/coordinators/readyForGameCoordinator.ts b/apps/server/src/application/coordinators/readyForGameCoordinator.ts
index 0f64720..19fbd7c 100644
--- a/apps/server/src/application/coordinators/readyForGameCoordinator.ts
+++ b/apps/server/src/application/coordinators/readyForGameCoordinator.ts
@@ -8,10 +8,14 @@
 import type { FindGameByPlayerPort, FindRoomByPlayerPort } from "@server/domains/room/application/ports/roomUseCasePorts";
 import { readyForGameUseCase } from "@server/domains/game/application/useCases/readyForGameUseCase";
 
-type ReadyForGameCoordinatorParams = {
-  socketId: string;
+type ReadyForGameDeps = {
   roomManager: FindRoomByPlayerPort;
   runtimeRegistry: FindGameByPlayerPort;
+};
+
+type ReadyForGameCoordinatorParams = {
+  socketId: string;
+} & ReadyForGameDeps & {
   output: Pick<GameOutputPort, "publishCurrentPlayersToSocket" | "publishGameStartToSocket">;
 };
 
diff --git a/apps/server/src/application/coordinators/startGameCoordinator.ts b/apps/server/src/application/coordinators/startGameCoordinator.ts
index e5143d9..d7c43e0 100644
--- a/apps/server/src/application/coordinators/startGameCoordinator.ts
+++ b/apps/server/src/application/coordinators/startGameCoordinator.ts
@@ -15,10 +15,14 @@
 import { gameUseCaseLogEvents, logResults, logScopes } from "@server/logging/index";
 import { roomConsts } from "@repo/shared";
 
-type StartGameCoordinatorParams = {
-  ownerId: string;
+type StartGameDeps = {
   roomManager: FindRoomByOwnerPort & RoomPhaseTransitionPort;
   runtimeRegistry: FindGameByRoomPort;
+};
+
+type StartGameCoordinatorParams = {
+  ownerId: string;
+} & StartGameDeps & {
   output: Pick<
     GameOutputPort,
     | "publishUpdatePlayersToSocket"
diff --git a/apps/server/src/domains/room/RoomManager.ts b/apps/server/src/domains/room/RoomManager.ts
index 47a86ed..4205a81 100644
--- a/apps/server/src/domains/room/RoomManager.ts
+++ b/apps/server/src/domains/room/RoomManager.ts
@@ -3,9 +3,9 @@
  * ルーム状態の保持とルーム操作サービスへの委譲を担うマネージャ
  */
 import type { roomTypes } from "@repo/shared";
-import { roomConsts } from "@repo/shared";
 import { RoomJoinService } from "./application/services/RoomJoinService";
 import { RoomExitService } from "./application/services/RoomExitService";
+import { RoomPhaseService } from "./application/services/RoomPhaseService";
 import { RoomQueryService } from "./application/services/RoomQueryService";
 import type { JoinRoomResult } from "./application/ports/roomUseCasePorts";
 
@@ -14,11 +14,13 @@
   private rooms: Map<string, roomTypes.Room> = new Map();
   private roomJoinService: RoomJoinService;
   private roomExitService: RoomExitService;
+  private roomPhaseService: RoomPhaseService;
   private roomQueryService: RoomQueryService;
 
   constructor() {
     this.roomJoinService = new RoomJoinService(this.rooms);
     this.roomExitService = new RoomExitService(this.rooms);
+    this.roomPhaseService = new RoomPhaseService(this.rooms);
     this.roomQueryService = new RoomQueryService(this.rooms);
   }
 
@@ -49,23 +51,11 @@
 
   // ルーム状態をPLAYINGへ更新する
   public markRoomPlaying(roomId: string): roomTypes.Room | undefined {
-    const room = this.roomQueryService.getRoomById(roomId);
-    if (!room) {
-      return undefined;
-    }
-
-    room.status = roomConsts.RoomPhase.PLAYING;
-    return room;
+    return this.roomPhaseService.markRoomPlaying(roomId);
   }
 
   // ルーム状態をWAITINGへ更新する
   public markRoomWaiting(roomId: string): roomTypes.Room | undefined {
-    const room = this.roomQueryService.getRoomById(roomId);
-    if (!room) {
-      return undefined;
-    }
-
-    room.status = roomConsts.RoomPhase.WAITING;
-    return room;
+    return this.roomPhaseService.markRoomWaiting(roomId);
   }
 }
\ No newline at end of file
diff --git a/apps/server/src/domains/room/application/services/RoomPhaseService.ts b/apps/server/src/domains/room/application/services/RoomPhaseService.ts
new file mode 100644
index 0000000..997c27a
--- /dev/null
+++ b/apps/server/src/domains/room/application/services/RoomPhaseService.ts
@@ -0,0 +1,31 @@
+/**
+ * RoomPhaseService
+ * ルーム状態のフェーズ更新処理を提供する
+ */
+import { roomConsts } from "@repo/shared";
+import type { roomTypes } from "@repo/shared";
+
+/** ルーム状態のフェーズ遷移を管理するサービス */
+export class RoomPhaseService {
+  constructor(private rooms: Map<string, roomTypes.Room>) {}
+
+  public markRoomPlaying(roomId: string): roomTypes.Room | undefined {
+    const room = this.rooms.get(roomId);
+    if (!room) {
+      return undefined;
+    }
+
+    room.status = roomConsts.RoomPhase.PLAYING;
+    return room;
+  }
+
+  public markRoomWaiting(roomId: string): roomTypes.Room | undefined {
+    const room = this.rooms.get(roomId);
+    if (!room) {
+      return undefined;
+    }
+
+    room.status = roomConsts.RoomPhase.WAITING;
+    return room;
+  }
+}
diff --git a/apps/server/src/domains/room/application/useCases/joinRoomUseCase.ts b/apps/server/src/domains/room/application/useCases/joinRoomUseCase.ts
index d1ddd59..f83aa9b 100644
--- a/apps/server/src/domains/room/application/useCases/joinRoomUseCase.ts
+++ b/apps/server/src/domains/room/application/useCases/joinRoomUseCase.ts
@@ -4,6 +4,7 @@
  */
 import type { roomTypes } from "@repo/shared";
 import type {
+  EnsureGameRuntimePort,
   JoinRoomPort,
   JoinRoomResult,
   RoomOutputPort,
@@ -13,6 +14,7 @@
 
 type JoinRoomUseCaseParams = {
   roomManager: JoinRoomPort;
+  runtimeRegistry: EnsureGameRuntimePort;
   socketId: string;
   data: roomTypes.JoinRoomPayload;
   output: Pick<RoomOutputPort, "publishJoinRejectedToSocket">;
@@ -21,6 +23,7 @@
 /** 参加イベントを受け取り，参加可否を判定する */
 export const joinRoomUseCase = ({
   roomManager,
+  runtimeRegistry,
   socketId,
   data,
   output,
@@ -51,5 +54,7 @@
     return joinResult;
   }
 
+  runtimeRegistry.ensureGameManagerForRoom(roomId);
+
   return joinResult;
 };
diff --git a/apps/server/src/domains/room/application/useCases/roomDisconnectUseCase.ts b/apps/server/src/domains/room/application/useCases/roomDisconnectUseCase.ts
index f534d14..9d3c9ce 100644
--- a/apps/server/src/domains/room/application/useCases/roomDisconnectUseCase.ts
+++ b/apps/server/src/domains/room/application/useCases/roomDisconnectUseCase.ts
@@ -2,13 +2,14 @@
  * roomDisconnectUseCase
  * 切断時のルーム退出処理と状態更新配信を行うユースケース
  */
-import type { DisconnectRoomPort } from "../ports/roomUseCasePorts";
+import type { CleanupGameRuntimePort, DisconnectRoomPort } from "../ports/roomUseCasePorts";
 import type { RoomOutputPort } from "../ports/roomUseCasePorts";
 import { logEvent } from "@server/logging/logger";
 import { logResults, logScopes, roomUseCaseLogEvents } from "@server/logging/index";
 
 type RoomDisconnectUseCaseParams = {
   roomManager: DisconnectRoomPort;
+  runtimeRegistry: CleanupGameRuntimePort;
   socketId: string;
   output: Pick<RoomOutputPort, "publishRoomUpdateToRoom">;
 };
@@ -16,6 +17,7 @@
 /** 切断ソケットを各ルームから退出させ，更新ルームを配信する */
 export const roomDisconnectUseCase = ({
   roomManager,
+  runtimeRegistry,
   socketId,
   output,
 }: RoomDisconnectUseCaseParams) => {
@@ -38,4 +40,6 @@
       totalPlayers: room.players.length,
     });
   });
+
+  runtimeRegistry.cleanupDisposedRoomRuntimes();
 };
diff --git a/apps/server/src/network/handlers/game/registerGameHandlers.ts b/apps/server/src/network/handlers/game/registerGameHandlers.ts
index 90f5996..97e40a9 100644
--- a/apps/server/src/network/handlers/game/registerGameHandlers.ts
+++ b/apps/server/src/network/handlers/game/registerGameHandlers.ts
@@ -11,6 +11,7 @@
   FindGameByPlayerPort,
   FindRoomByOwnerPort,
   FindRoomByPlayerPort,
+  RoomScopedGamePort,
   RoomPhaseTransitionPort,
 } from "@server/domains/room/application/ports/roomUseCasePorts";
 import { movePlayerUseCase } from "@server/domains/game/application/useCases/movePlayerUseCase";
@@ -29,6 +30,28 @@
   [protocol.SocketEvents.PLACE_BOMB]: isPlaceBombPayload,
 } as const;
 
+type RuntimeResolution = {
+  roomId: string;
+  gameManager: RoomScopedGamePort;
+};
+
+const resolveRuntimeBySocketId = (
+  roomManager: FindRoomByPlayerPort,
+  runtimeRegistry: FindGameByPlayerPort,
+  socketId: string
+): RuntimeResolution | undefined => {
+  const roomId = roomManager.getRoomByPlayerId(socketId)?.roomId;
+  const gameManager = runtimeRegistry.getGameManagerByPlayerId(socketId);
+  if (!roomId || !gameManager) {
+    return undefined;
+  }
+
+  return {
+    roomId,
+    gameManager,
+  };
+};
+
 /** ゲームイベントの購読とユースケース呼び出しを設定する */
 export const registerGameHandlers = (
   io: Server,
@@ -90,13 +113,13 @@
       return;
     }
 
-    const gameManager = runtimeRegistry.getGameManagerByPlayerId(socket.id);
-    if (!gameManager) {
+    const runtime = resolveRuntimeBySocketId(roomManager, runtimeRegistry, socket.id);
+    if (!runtime) {
       return;
     }
 
     movePlayerUseCase({
-      gameManager,
+      gameManager: runtime.gameManager,
       playerId: socket.id,
       move: data,
     });
@@ -108,15 +131,14 @@
       return;
     }
 
-    const roomId = roomManager.getRoomByPlayerId(socket.id)?.roomId;
-    const gameManager = runtimeRegistry.getGameManagerByPlayerId(socket.id);
-    if (!roomId || !gameManager) {
+    const runtime = resolveRuntimeBySocketId(roomManager, runtimeRegistry, socket.id);
+    if (!runtime) {
       return;
     }
 
     placeBombUseCase({
-      roomId,
-      bombStore: gameManager,
+      roomId: runtime.roomId,
+      bombStore: runtime.gameManager,
       input: {
         socketId: socket.id,
         payload: data,
diff --git a/apps/server/src/network/handlers/room/registerRoomHandlers.ts b/apps/server/src/network/handlers/room/registerRoomHandlers.ts
index db1b83c..ca247cb 100644
--- a/apps/server/src/network/handlers/room/registerRoomHandlers.ts
+++ b/apps/server/src/network/handlers/room/registerRoomHandlers.ts
@@ -48,6 +48,7 @@
 
     const joinResult = joinRoomUseCase({
       roomManager,
+      runtimeRegistry,
       socketId: socket.id,
       data,
       output: roomOutputAdapter,
@@ -74,7 +75,6 @@
         return;
 
       case "joined":
-        runtimeRegistry.ensureGameManagerForRoom(roomId);
         await socket.join(roomId);
         roomOutputAdapter.publishRoomUpdateToRoom(roomId, joinResult.room);
         logEvent(logScopes.ROOM_USE_CASE, {
diff --git a/apps/server/src/network/types/connectionPorts.ts b/apps/server/src/network/types/connectionPorts.ts
index 2b1f4a2..ca79e45 100644
--- a/apps/server/src/network/types/connectionPorts.ts
+++ b/apps/server/src/network/types/connectionPorts.ts
@@ -29,6 +29,24 @@
   & FindGameByRoomPort
   & FindGameByPlayerPort;
 
+/** START_GAME調停で利用する依存集合 */
+export type StartGameDeps = {
+  roomManager: FindRoomByOwnerPort & RoomPhaseTransitionPort;
+  runtimeRegistry: FindGameByRoomPort;
+};
+
+/** READY_FOR_GAME調停で利用する依存集合 */
+export type ReadyForGameDeps = {
+  roomManager: FindRoomByPlayerPort;
+  runtimeRegistry: FindGameByPlayerPort;
+};
+
+/** DISCONNECT調停で利用する依存集合 */
+export type DisconnectDeps = {
+  roomManager: DisconnectRoomPort & FindRoomByPlayerPort & FindRoomByIdPort;
+  runtimeRegistry: FindGameByPlayerPort & CleanupGameRuntimePort;
+};
+
 /** ソケット接続全体で利用するルーム管理ポート集合 */
 export type SocketConnectionRoomPort =
   & ConnectionRoomPort
@@ -41,7 +59,7 @@
   & CleanupGameRuntimePort;
 
 /** ソケット接続ハンドラで受け取るマネージャ依存の束 */
-export type SocketConnectionManagerBundle = {
+export type SocketConnectionManagerBundle = DisconnectDeps & {
   roomManager: SocketConnectionRoomPort;
   runtimeRegistry: SocketConnectionRuntimePort;
 };