From 16fe7f0e270d38cca42e7ab65c6722d2d18e30d0 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 12:44:26 +0900
Subject: [PATCH 01/16] =?UTF-8?q?chore:=20update=20brakeman=208.0.2=20?=
 =?UTF-8?q?=E2=86=92=208.0.4?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 Gemfile.lock | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Gemfile.lock b/Gemfile.lock
index 4a8207c..35c435a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -84,7 +84,7 @@ GEM
     bindex (0.8.1)
     bootsnap (1.22.0)
       msgpack (~> 1.2)
-    brakeman (8.0.2)
+    brakeman (8.0.4)
       racc
     builder (3.3.0)
     bundler-audit (0.9.3)

From e3050aa89a410453fcf6e2a9f1d6c65f4c62fb7a Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 12:44:32 +0900
Subject: [PATCH 02/16] test(m9): add closed_registration fixture for
 deadline-passed tests

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 test/fixtures/registrations.yml | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/test/fixtures/registrations.yml b/test/fixtures/registrations.yml
index 9b528a9..90f77c2 100644
--- a/test/fixtures/registrations.yml
+++ b/test/fixtures/registrations.yml
@@ -7,3 +7,13 @@ hong_5km:
   phone_number: "01012345678"
   address: "서울시 강남구"
   confirmation_code: "A1B2C3D4"
+
+closed_registration:
+  race: closed_race
+  course: closed_five_km
+  name: "김마감"
+  birth_date: "1985-05-05"
+  gender: "female"
+  phone_number: "01055556666"
+  address: "부산시 해운대구"
+  confirmation_code: "X9Y8Z7W6"

From 830d05d096586f2f15bba13f4a4af6f4be1d0768 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 12:44:38 +0900
Subject: [PATCH 03/16] feat(m9): add cancelable? and cancel! with idempotency
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- Add status enum (applied, canceled, refunded)
- Add cancelable? (applied + registration open)
- Add cancel! with idempotency (already canceled → true)
- Add NotCancelableError for closed registration cancel attempt

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 PLAN.md                          |  6 +++---
 app/models/registration.rb       | 15 +++++++++++++
 test/models/registration_test.rb | 36 ++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/PLAN.md b/PLAN.md
index 531172e..1193a11 100755
--- a/PLAN.md
+++ b/PLAN.md
@@ -254,9 +254,9 @@ bundle exec rails runner "puts 'OK'"
 
 **Unit Tests**
 
-- [ ] Registration#cancelable? - applied 상태 + 마감 전만 true
-- [ ] Registration#cancel! - 멱등성: 이미 취소면 성공 반환
-- [ ] 마감 후 cancel! → NotCancelableError
+- [x] Registration#cancelable? - applied 상태 + 마감 전만 true
+- [x] Registration#cancel! - 멱등성: 이미 취소면 성공 반환
+- [x] 마감 후 cancel! → NotCancelableError
 
 **Integration Tests**
 
diff --git a/app/models/registration.rb b/app/models/registration.rb
index 5bd0359..3833acb 100644
--- a/app/models/registration.rb
+++ b/app/models/registration.rb
@@ -1,10 +1,13 @@
 class Registration < ApplicationRecord
+  class NotCancelableError < StandardError; end
+
   belongs_to :race
   belongs_to :course
 
   before_validation :set_race_from_course
   before_create :generate_confirmation_code
 
+  enum :status, { applied: "applied", canceled: "canceled", refunded: "refunded" }
   enum :gender, { male: "male", female: "female" }
 
   normalizes :name, with: ->(name) { name.gsub(/\s+/, "") }
@@ -18,6 +21,18 @@ class Registration < ApplicationRecord
   validates :birth_date, :gender, presence: true
   validates :address, presence: true, length: { maximum: 30 }
 
+  def cancelable?
+    applied? && !race.registration_closed?
+  end
+
+  def cancel!
+    return true if canceled?
+
+    raise NotCancelableError, "취소 가능 기간이 지났습니다." unless cancelable?
+
+    update!(status: :canceled, canceled_at: Time.current)
+  end
+
   private
 
   def set_race_from_course
diff --git a/test/models/registration_test.rb b/test/models/registration_test.rb
index f84c267..17ff294 100644
--- a/test/models/registration_test.rb
+++ b/test/models/registration_test.rb
@@ -76,6 +76,42 @@ class RegistrationTest < ActiveSupport::TestCase
     assert_match(/\A[A-Z0-9]{8}\z/, registration.confirmation_code)
   end
 
+  test "cancelable? returns true when applied and registration open" do
+    assert registrations(:hong_5km).cancelable?
+  end
+
+  test "cancelable? returns false when registration closed" do
+    assert_not registrations(:closed_registration).cancelable?
+  end
+
+  test "cancelable? returns false when canceled or refunded" do
+    registration = registrations(:hong_5km)
+
+    registration.status = :canceled
+    assert_not registration.cancelable?
+
+    registration.status = :refunded
+    assert_not registration.cancelable?
+  end
+
+  test "cancel! changes status to canceled and sets canceled_at" do
+    registration = registrations(:hong_5km)
+    registration.cancel!
+    assert registration.canceled?
+    assert_not_nil registration.canceled_at
+  end
+
+  test "cancel! is idempotent for already canceled registration" do
+    registration = registrations(:hong_5km)
+    registration.cancel!
+    assert registration.cancel!
+  end
+
+  test "cancel! raises NotCancelableError when registration closed" do
+    registration = registrations(:closed_registration)
+    assert_raises(Registration::NotCancelableError) { registration.cancel! }
+  end
+
   test "requires name, phone_number, birth_date, gender, and address" do
     registration = registrations(:hong_5km)
     registration.name = nil

From 1b84e5d0581897a318a7c8b9532744fff8eb2542 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 12:44:46 +0900
Subject: [PATCH 04/16] docs: add cancel idempotency design rationale

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 docs/resume.md | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/docs/resume.md b/docs/resume.md
index edcec5e..ef3e999 100644
--- a/docs/resume.md
+++ b/docs/resume.md
@@ -142,3 +142,29 @@ end
 ```
 
 컨트롤러와 폼에서 race를 명시적으로 다룰 필요가 없어지고, 코스 선택만으로 신청이 완성된다.
+
+---
+
+# 취소의 멱등성 설계
+
+## 문제
+
+사용자가 취소 버튼을 두 번 누르거나, 완료 후 새로고침하면 같은 취소 요청이 중복으로 들어온다. 이때 에러를 보여주면 사용자는 "취소가 안 된 건가?"라고 혼란스러워한다.
+
+## 해결: 이미 처리된 상태면 성공 반환
+
+```ruby
+def cancel!
+  return true if canceled?
+  raise NotCancelableError, "취소 가능 기간이 지났습니다." unless cancelable?
+  update!(status: :canceled, canceled_at: Time.current)
+end
+```
+
+- `canceled?` → 이미 원하는 결과(취소)가 달성된 상태이므로 에러 없이 `true` 반환
+- `applied?` + 마감 전 → 정상 취소 처리
+- `applied?` + 마감 후 → `NotCancelableError` (이 경우만 에러)
+
+에러를 던지는 기준은 "사용자의 의도를 달성할 수 없는 경우"뿐이다.
+
+> `refunded` 상태의 멱등성 처리는 결제 기능 도입 후 작성 예정.

From 1b2724301734e82edce6b7b1c7cdd3e613d156ad Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 12:57:04 +0900
Subject: [PATCH 05/16] feat(m9): add LookupController with lookup routes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 app/controllers/lookup_controller.rb | 17 +++++++++++++++++
 app/views/lookup/new.html.erb        | 13 +++++++++++++
 app/views/lookup/show.html.erb       |  6 ++++++
 config/routes.rb                     |  4 ++++
 4 files changed, 40 insertions(+)
 create mode 100644 app/controllers/lookup_controller.rb
 create mode 100644 app/views/lookup/new.html.erb
 create mode 100644 app/views/lookup/show.html.erb

diff --git a/app/controllers/lookup_controller.rb b/app/controllers/lookup_controller.rb
new file mode 100644
index 0000000..5d7130c
--- /dev/null
+++ b/app/controllers/lookup_controller.rb
@@ -0,0 +1,17 @@
+class LookupController < ApplicationController
+  def new
+  end
+
+  def create
+    @registration = Registration.find_by(
+      confirmation_code: params[:confirmation_code],
+      name: params[:name]
+    )
+
+    if @registration
+      render :show
+    else
+      redirect_to lookup_path, alert: "신청 내역을 찾을 수 없습니다."
+    end
+  end
+end
diff --git a/app/views/lookup/new.html.erb b/app/views/lookup/new.html.erb
new file mode 100644
index 0000000..54ee556
--- /dev/null
+++ b/app/views/lookup/new.html.erb
@@ -0,0 +1,13 @@
+<h1>신청 조회</h1>
+
+<%= form_with url: lookup_path, method: :post do |f| %>
+  <div>
+    <%= f.label :confirmation_code, "확인 코드" %>
+    <%= f.text_field :confirmation_code %>
+  </div>
+  <div>
+    <%= f.label :name, "이름" %>
+    <%= f.text_field :name %>
+  </div>
+  <%= f.submit "조회" %>
+<% end %>
diff --git a/app/views/lookup/show.html.erb b/app/views/lookup/show.html.erb
new file mode 100644
index 0000000..f7bb393
--- /dev/null
+++ b/app/views/lookup/show.html.erb
@@ -0,0 +1,6 @@
+<h1>신청 내역</h1>
+
+<p class="confirmation-code"><%= @registration.confirmation_code %></p>
+<p>이름: <%= @registration.name %></p>
+<p>코스: <%= @registration.course.name %></p>
+<p>상태: <%= @registration.status %></p>
diff --git a/config/routes.rb b/config/routes.rb
index 60bfd32..4ff2634 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -11,6 +11,10 @@
 
   root "home#show"
 
+  get "lookup", to: "lookup#new"
+  post "lookup", to: "lookup#create"
+  delete "lookup", to: "lookup#cancel"
+
   resources :courses, only: [] do
     resources :registrations, only: [ :new, :create, :show ]
   end

From 6e36c3440a735f712bce08da7cfae336b45c1dbc Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 12:57:10 +0900
Subject: [PATCH 06/16] test(m9): add lookup integration tests

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 PLAN.md                         |  4 ++--
 test/integration/lookup_test.rb | 25 +++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 test/integration/lookup_test.rb

diff --git a/PLAN.md b/PLAN.md
index 1193a11..2d20102 100755
--- a/PLAN.md
+++ b/PLAN.md
@@ -260,8 +260,8 @@ bundle exec rails runner "puts 'OK'"
 
 **Integration Tests**
 
-- [ ] confirmation_code + 이름으로 조회 성공
-- [ ] 잘못된 정보로 조회 → 에러 메시지
+- [x] confirmation_code + 이름으로 조회 성공
+- [x] 잘못된 정보로 조회 → 에러 메시지
 - [ ] 취소 성공 → status 변경, canceled_at 기록
 - [ ] 이미 취소된 신청 다시 취소 → 에러 없이 성공 (P1)
 - [ ] 마감 후 취소 시도 → 차단 (P0)
diff --git a/test/integration/lookup_test.rb b/test/integration/lookup_test.rb
new file mode 100644
index 0000000..b6bfd75
--- /dev/null
+++ b/test/integration/lookup_test.rb
@@ -0,0 +1,25 @@
+require "test_helper"
+
+class LookupTest < ActionDispatch::IntegrationTest
+  test "lookup with valid confirmation_code and name shows registration details" do
+    registration = registrations(:hong_5km)
+
+    post lookup_path, params: {
+      confirmation_code: registration.confirmation_code,
+      name: registration.name
+    }
+
+    assert_response :success
+    assert_select ".confirmation-code", text: /#{registration.confirmation_code}/
+  end
+
+  test "lookup with invalid information shows error message" do
+    post lookup_path, params: {
+      confirmation_code: "ZZZZZZZZ",
+      name: "없는사람"
+    }
+
+    assert_redirected_to lookup_path
+    assert_equal "신청 내역을 찾을 수 없습니다.", flash[:alert]
+  end
+end

From bc598fe044ee8df351e470f5f8ec755097c07a77 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:01:51 +0900
Subject: [PATCH 07/16] docs: add render vs redirect and normalizes
 explanations

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 docs/resume.md | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/docs/resume.md b/docs/resume.md
index ef3e999..ee704ad 100644
--- a/docs/resume.md
+++ b/docs/resume.md
@@ -168,3 +168,70 @@ end
 에러를 던지는 기준은 "사용자의 의도를 달성할 수 없는 경우"뿐이다.
 
 > `refunded` 상태의 멱등성 처리는 결제 기능 도입 후 작성 예정.
+
+---
+
+# render vs redirect: 에러 전달 방식의 차이
+
+## render — 같은 요청에서 뷰를 다시 그린다
+
+- 인스턴스 변수(`@registration.errors`)가 유지되므로 뷰에서 필드별 에러를 직접 표시
+- 폼 입력값이 보존됨
+- 용도: validation 실패 (필수 필드 누락, 형식 오류 등)
+
+```ruby
+rescue ActiveRecord::RecordInvalid => e
+  @registration = e.record
+  render :new, status: :unprocessable_entity
+```
+
+## redirect — 새 요청을 보낸다
+
+- 인스턴스 변수가 소멸하므로 `flash`로 메시지를 전달
+- 폼 입력값이 사라짐
+- 용도: 권한 거부, 중복 신청, 마감 등 폼 보존이 불필요한 경우
+
+```ruby
+redirect_to new_course_registration_path(@course), alert: "정원이 마감되었습니다."
+```
+
+## 테스트에서의 차이
+
+| 방식 | 응답 검증 | 메시지 검증 |
+|------|-----------|-------------|
+| render | `assert_response :unprocessable_entity` | `assert_select ".field-errors"` |
+| redirect | `assert_redirected_to path` | `assert_equal "메시지", flash[:alert]` |
+
+redirect 후에는 페이지 본문이 없으므로 `assert_select`를 쓸 수 없고, flash로 검증한다.
+
+---
+
+# Rails normalizes vs before_validation
+
+## normalizes — 선언적 정규화 (Rails 7.1+)
+
+```ruby
+normalizes :name, with: ->(name) { name.gsub(/\s+/, "") }
+normalizes :phone_number, with: ->(phone) { phone.gsub(/\D/, "") }
+```
+
+- 속성이 **대입되는 즉시** 변환됨 (`registration.name = "홍 길 동"` → 바로 `"홍길동"`)
+- `find_by`에도 정규화가 적용됨 (`Registration.find_by(name: "홍 길 동")` → `"홍길동"`으로 검색)
+- 선언적이라 의도가 명확하고, 콜백 순서에 의존하지 않음
+
+## before_validation — 콜백 기반 정규화
+
+```ruby
+before_validation :normalize_name
+def normalize_name
+  self.name = name.gsub(/\s+/, "")
+end
+```
+
+- `valid?`나 `save` 호출 시에만 변환됨 — 대입 직후에는 원본값이 남아 있음
+- `find_by`에 적용되지 않음 — 검색 시 수동으로 정규화해야 함
+- 콜백 순서에 따라 다른 validation과 충돌할 수 있음
+
+## 이 프로젝트에서의 선택
+
+이름과 전화번호에 `normalizes`를 사용하여, 저장뿐 아니라 조회 시에도 일관된 정규화를 보장한다. 특히 조회 기능(`find_by(name:)`)에서 사용자가 공백을 포함해 입력해도 정확히 매칭된다.

From 9fadbb7925266dbf958f615327b73a31d67fe050 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:06:57 +0900
Subject: [PATCH 08/16] docs: require name for cancel request in TECHSPEC

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 TECHSPEC.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/TECHSPEC.md b/TECHSPEC.md
index 983237d..e81ce3a 100755
--- a/TECHSPEC.md
+++ b/TECHSPEC.md
@@ -709,7 +709,7 @@ end
 ```ruby
 # RegistrationsController
 def cancel
-  registration = Registration.find_by!(confirmation_code: params[:code])
+  registration = Registration.find_by!(confirmation_code: params[:confirmation_code], name: params[:name])
 
   registration.cancel!
   redirect_to registration_path(registration), notice: "신청이 취소되었습니다."
@@ -722,7 +722,7 @@ end
 
 **규칙:**
 
-- 조회 페이지에서 취소 진행 → confirmation_code만으로 식별
+- 조회 페이지에서 취소 진행 → confirmation_code + name으로 본인 확인
 - 이미 canceled/refunded 상태면 성공 응답 (에러 아님)
 - 신청 마감일 이후에는 취소 불가
 - 서버에서 취소 가능 여부 검증 (프론트엔드 버튼 숨김에만 의존하지 않음)

From 4f0101d9331d83c9068ad124fb5a2295d42390de Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:18:41 +0900
Subject: [PATCH 09/16] feat(m9): add cancel action to LookupController

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 app/controllers/lookup_controller.rb | 14 ++++++++++++++
 test/integration/lookup_test.rb      | 15 +++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/app/controllers/lookup_controller.rb b/app/controllers/lookup_controller.rb
index 5d7130c..da68fd7 100644
--- a/app/controllers/lookup_controller.rb
+++ b/app/controllers/lookup_controller.rb
@@ -14,4 +14,18 @@ def create
       redirect_to lookup_path, alert: "신청 내역을 찾을 수 없습니다."
     end
   end
+
+  def cancel
+    registration = Registration.find_by!(
+      confirmation_code: params[:confirmation_code],
+      name: params[:name]
+    )
+
+    registration.cancel!
+    redirect_to lookup_path, notice: "신청이 취소되었습니다."
+  rescue ActiveRecord::RecordNotFound
+    redirect_to lookup_path, alert: "신청 내역을 찾을 수 없습니다."
+  rescue Registration::NotCancelableError => e
+    redirect_to lookup_path, alert: e.message
+  end
 end
diff --git a/test/integration/lookup_test.rb b/test/integration/lookup_test.rb
index b6bfd75..ce05c8b 100644
--- a/test/integration/lookup_test.rb
+++ b/test/integration/lookup_test.rb
@@ -22,4 +22,19 @@ class LookupTest < ActionDispatch::IntegrationTest
     assert_redirected_to lookup_path
     assert_equal "신청 내역을 찾을 수 없습니다.", flash[:alert]
   end
+
+  test "cancel changes status to canceled and records canceled_at" do
+    registration = registrations(:hong_5km)
+
+    delete lookup_path, params: {
+      confirmation_code: registration.confirmation_code,
+      name: registration.name
+    }
+
+    registration.reload
+    assert registration.canceled?
+    assert_not_nil registration.canceled_at
+    assert_redirected_to lookup_path
+    assert_equal "신청이 취소되었습니다.", flash[:notice]
+  end
 end

From f08a246c5c2ec33a889e902c3b8d7cde8f79c0d7 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:19:15 +0900
Subject: [PATCH 10/16] docs: add if/else vs rescue error handling explanation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 docs/resume.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/docs/resume.md b/docs/resume.md
index ee704ad..1a10d89 100644
--- a/docs/resume.md
+++ b/docs/resume.md
@@ -206,6 +206,13 @@ redirect 후에는 페이지 본문이 없으므로 `assert_select`를 쓸 수 
 
 ---
 
+# if/else vs rescue: 에러 처리 방식 선택 기준
+
+- **if/else** — 예상된 분기. 정상 흐름의 일부. (예: 조회 실패, 사전 체크)
+- **rescue** — 예외 상황. 정상 흐름에서 벗어난 경우. (예: 동시성 충돌, DB 제약 위반)
+
+---
+
 # Rails normalizes vs before_validation
 
 ## normalizes — 선언적 정규화 (Rails 7.1+)

From ee8c85fc71bc1b9d1ce73cbfff60e73b13bab735 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:30:16 +0900
Subject: [PATCH 11/16] test(m9): add idempotent cancel and deadline cancel
 tests

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 test/integration/lookup_test.rb | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/test/integration/lookup_test.rb b/test/integration/lookup_test.rb
index ce05c8b..102e901 100644
--- a/test/integration/lookup_test.rb
+++ b/test/integration/lookup_test.rb
@@ -37,4 +37,29 @@ class LookupTest < ActionDispatch::IntegrationTest
     assert_redirected_to lookup_path
     assert_equal "신청이 취소되었습니다.", flash[:notice]
   end
+
+  test "canceling already canceled registration succeeds without error" do
+    registration = registrations(:hong_5km)
+    registration.cancel!
+
+    delete lookup_path, params: {
+      confirmation_code: registration.confirmation_code,
+      name: registration.name
+    }
+
+    assert_redirected_to lookup_path
+    assert_equal "신청이 취소되었습니다.", flash[:notice]
+  end
+
+  test "canceling after registration deadline is blocked" do
+    registration = registrations(:closed_registration)
+
+    delete lookup_path, params: {
+      confirmation_code: registration.confirmation_code,
+      name: registration.name
+    }
+
+    assert_redirected_to lookup_path
+    assert_equal "취소 가능 기간이 지났습니다.", flash[:alert]
+  end
 end

From c52a67b43c5269b134e1644fe82e98f623f4aa06 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:31:58 +0900
Subject: [PATCH 12/16] docs(m9): update commit hashes in PLAN.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 PLAN.md | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/PLAN.md b/PLAN.md
index 2d20102..d37cf0f 100755
--- a/PLAN.md
+++ b/PLAN.md
@@ -262,13 +262,13 @@ bundle exec rails runner "puts 'OK'"
 
 - [x] confirmation_code + 이름으로 조회 성공
 - [x] 잘못된 정보로 조회 → 에러 메시지
-- [ ] 취소 성공 → status 변경, canceled_at 기록
-- [ ] 이미 취소된 신청 다시 취소 → 에러 없이 성공 (P1)
-- [ ] 마감 후 취소 시도 → 차단 (P0)
+- [x] 취소 성공 → status 변경, canceled_at 기록
+- [x] 이미 취소된 신청 다시 취소 → 에러 없이 성공 (P1)
+- [x] 마감 후 취소 시도 → 차단 (P0)
 
 **완료 조건:** 조회/취소 플로우 동작, 멱등성 보장
 
-- Commits:
+- Commits: 830d05d, 1b27243, 4f0101d, ee8c85f
 
 ---
 

From 94a318ec5e0b06f34a312c830681cddafd3285c0 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:36:38 +0900
Subject: [PATCH 13/16] feat(m9): add lookup link to home page

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 app/views/home/show.html.erb | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/app/views/home/show.html.erb b/app/views/home/show.html.erb
index 7b3f205..a4cd337 100644
--- a/app/views/home/show.html.erb
+++ b/app/views/home/show.html.erb
@@ -9,3 +9,5 @@
     </div>
   <% end %>
 </div>
+
+<%= link_to "신청 조회/취소", lookup_path %>

From 1140de75c88a553caca88327d3280097f7dc729b Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:41:20 +0900
Subject: [PATCH 14/16] fix(m9): disable turbo on lookup form to allow render
 response

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 app/views/lookup/new.html.erb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/views/lookup/new.html.erb b/app/views/lookup/new.html.erb
index 54ee556..6202083 100644
--- a/app/views/lookup/new.html.erb
+++ b/app/views/lookup/new.html.erb
@@ -1,6 +1,6 @@
 <h1>신청 조회</h1>
 
-<%= form_with url: lookup_path, method: :post do |f| %>
+<%= form_with url: lookup_path, method: :post, data: { turbo: false } do |f| %>
   <div>
     <%= f.label :confirmation_code, "확인 코드" %>
     <%= f.text_field :confirmation_code %>

From afffd7280fa72bb3e7719089c03fdb79e274e8fe Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:43:04 +0900
Subject: [PATCH 15/16] docs: add Turbo Drive POST render conflict explanation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 docs/resume.md | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/docs/resume.md b/docs/resume.md
index 1a10d89..18e32e3 100644
--- a/docs/resume.md
+++ b/docs/resume.md
@@ -206,6 +206,20 @@ redirect 후에는 페이지 본문이 없으므로 `assert_select`를 쓸 수 
 
 ---
 
+# Turbo Drive와 POST → render 충돌
+
+일반적인 Rails POST 흐름은 "데이터 생성 → redirect → 새 페이지"이다. Turbo Drive는 이를 전제로 설계되어, POST 응답이 200(render)이면 에러를 발생시킨다. redirect(303) 또는 4xx/5xx만 허용한다.
+
+**문제:** lookup은 POST가 "생성"이 아니라 "검색"이다. 결과를 그 자리에서 render하고 싶지만, Turbo가 이를 거부한다. redirect하려면 URL에 confirmation_code와 이름을 실어야 하는데, 이는 개인정보 노출이므로 안 된다.
+
+**해결:** 해당 폼에서만 Turbo를 비활성화한다.
+
+```erb
+<%= form_with url: lookup_path, method: :post, data: { turbo: false } do |f| %>
+```
+
+---
+
 # if/else vs rescue: 에러 처리 방식 선택 기준
 
 - **if/else** — 예상된 분기. 정상 흐름의 일부. (예: 조회 실패, 사전 체크)

From 3e4d12f0ece72f7b120626cd08ae34c097dc8459 Mon Sep 17 00:00:00 2001
From: iamodh <imodh97@gmail.com>
Date: Fri, 27 Feb 2026 13:47:04 +0900
Subject: [PATCH 16/16] feat(m9): add cancel button to lookup show page

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 app/views/lookup/show.html.erb | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/app/views/lookup/show.html.erb b/app/views/lookup/show.html.erb
index f7bb393..6b9012e 100644
--- a/app/views/lookup/show.html.erb
+++ b/app/views/lookup/show.html.erb
@@ -4,3 +4,7 @@
 <p>이름: <%= @registration.name %></p>
 <p>코스: <%= @registration.course.name %></p>
 <p>상태: <%= @registration.status %></p>
+
+<% if @registration.cancelable? %>
+  <%= button_to "신청 취소", lookup_path, method: :delete, params: { confirmation_code: @registration.confirmation_code, name: @registration.name } %>
+<% end %>