diff --git a/design/backend/sequence/inner/event-추천안선택.puml b/design/backend/sequence/inner/event-추천안선택.puml
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+@startuml event-추천안선택
+!theme mono
+
+title Event Service - 선택한 AI 추천안 저장 (UFR-EVENT-040)
+
+participant "EventController" as Controller <<C>>
+participant "EventService" as Service <<S>>
+participant "EventRepository" as Repo <<R>>
+participant "Redis Cache" as Cache <<E>>
+database "Event DB" as DB <<E>>
+
+note over Controller: PUT /api/events/drafts/{id}/recommendation
+Controller -> Service: updateEventRecommendation(eventDraftId, userId,\nselectedRecommendation)
+activate Service
+
+Service -> Repo: findById(eventDraftId)
+activate Repo
+Repo -> DB: 이벤트 초안 조회\n(초안ID와 사용자ID로 조회)
+activate DB
+DB --> Repo: EventDraft
+deactivate DB
+Repo --> Service: EventDraft entity
+deactivate Repo
+
+Service -> Service: validateOwnership(userId, eventDraft)
+Service -> Service: validateRecommendation(selectedRecommendation)
+note right: 선택한 추천안\n유효성 검증
+
+Service -> Service: applyRecommendation(eventDraft, selectedRecommendation)
+note right: 추천안 적용:\n- 이벤트 제목\n- 경품 정보\n- 참여 방법\n- 예상 비용\n- 예상 ROI
+
+Service -> Repo: update(eventDraft)
+activate Repo
+Repo -> DB: 이벤트 초안 업데이트\n(선택된 추천안 정보,\n제목, 경품, 참여방법,\n예상비용, 예상ROI,\n수정일시를 업데이트)
+activate DB
+DB --> Repo: OK
+deactivate DB
+Repo --> Service: EventDraft entity
+deactivate Repo
+
+Service -> Cache: delete("ai:recommendation:" + eventDraftId)
+activate Cache
+note right: Redis 캐시 무효화\n(AI 추천 결과)
+Cache --> Service: OK
+deactivate Cache
+
+Service --> Controller: EventRecommendationResponse\n{eventDraftId, selectedRecommendation}
+deactivate Service
+Controller --> Client: 200 OK\n{eventDraftId}
+
+note over Controller, Cache: 최종 선택된 추천안만\nEvent DB에 저장됨\n\nRedis에 저장된 3가지 추천안은\n선택 후 삭제됨
+
+@enduml