diff --git a/src/adapter/outbound/persistence-jpa/src/main/java/dev/caskeleton/adapter/outbound/persistence/techlog/management/JdbcProjectActivityRepositoryAdapter.java b/src/adapter/outbound/persistence-jpa/src/main/java/dev/caskeleton/adapter/outbound/persistence/techlog/management/JdbcProjectActivityRepositoryAdapter.java
index 7ff1005..758b0b4 100644
--- a/src/adapter/outbound/persistence-jpa/src/main/java/dev/caskeleton/adapter/outbound/persistence/techlog/management/JdbcProjectActivityRepositoryAdapter.java
+++ b/src/adapter/outbound/persistence-jpa/src/main/java/dev/caskeleton/adapter/outbound/persistence/techlog/management/JdbcProjectActivityRepositoryAdapter.java
@@ -9,7 +9,6 @@ import java.sql.SQLException;
 import java.util.List;
 import java.util.Optional;
 import java.util.UUID;
-import java.util.function.Supplier;
 import org.springframework.jdbc.core.simple.JdbcClient;
 import org.springframework.stereotype.Repository;
 
@@ -30,15 +29,14 @@ public class JdbcProjectActivityRepositoryAdapter implements ProjectActivityRepo
           + " related_resource_type, related_resource_id, occurred_at, version";
 
   private final JdbcClient jdbcClient;
-  private final Supplier<UUID> idGenerator;
 
+  /*
+   * 생성자는 하나뿐이어야 한다. 한때 테스트용 id 생성기를 받는 두 번째 생성자가 있었고, 그러면
+   * 컴포넌트 스캔이 어느 것을 쓸지 정하지 못해 기본 생성자를 찾다가 실패한다 — 컴파일도 테스트도
+   * 통과하고 운영에서 기동만 못 한다. id 는 여기서 만들면 되고, 통합 테스트는 그 값을 볼 필요가 없다.
+   */
   public JdbcProjectActivityRepositoryAdapter(JdbcClient jdbcClient) {
-    this(jdbcClient, UUID::randomUUID);
-  }
-
-  JdbcProjectActivityRepositoryAdapter(JdbcClient jdbcClient, Supplier<UUID> idGenerator) {
     this.jdbcClient = jdbcClient;
-    this.idGenerator = idGenerator;
   }
 
   private static ProjectActivityView map(ResultSet rs, int rowNum) throws SQLException {
@@ -85,7 +83,7 @@ public class JdbcProjectActivityRepositoryAdapter implements ProjectActivityRepo
 
   @Override
   public ProjectActivityView create(CreateProjectActivityCommand command) {
-    UUID id = idGenerator.get();
+    UUID id = UUID.randomUUID();
     jdbcClient
         .sql(
             "INSERT INTO project_activity (id, project_id, activity_type, title, summary,"
diff --git a/src/app-bootstrap/src/test/java/dev/caskeleton/bootstrap/architecture/CleanArchitectureTest.java b/src/app-bootstrap/src/test/java/dev/caskeleton/bootstrap/architecture/CleanArchitectureTest.java
index 74be600..e89c68c 100644
--- a/src/app-bootstrap/src/test/java/dev/caskeleton/bootstrap/architecture/CleanArchitectureTest.java
+++ b/src/app-bootstrap/src/test/java/dev/caskeleton/bootstrap/architecture/CleanArchitectureTest.java
@@ -2158,4 +2158,67 @@ class CleanArchitectureTest {
         .filter(value -> value instanceof Number number && number.intValue() == SqlTypes.UUID)
         .isPresent();
   }
+
+  /**
+   * Spring 이 생성자를 고를 수 있어야 한다.
+   *
+   * <p>이 규칙은 사고 하나에서 나왔다. 한 어댑터가 생성자를 둘 갖고 있었고 — 하나는 운영용, 하나는 테스트가 id 생성기를 넣기 위한 것 — 둘 중 어느 것에도
+   * {@code @Autowired} 가 없었다. 컴포넌트 스캔은 고르지 못하고 기본 생성자를 찾다가 실패한다. 컴파일도, 단위 테스트도, 실제 PostgreSQL 위에서
+   * 도는 통합 테스트도 전부 통과했다. 그 어느 것도 컨텍스트를 띄우지 않기 때문이다. 운영에서 기동만 못 했다.
+   *
+   * <p>그래서 여기서 막는다: 스캔되는 스프링 컴포넌트는 생성자가 하나이거나, 여럿이면 그중 하나에 {@code @Autowired} 가 붙어 있어야 한다.
+   */
+  @ArchTest
+  static final ArchRule SPRING_COMPONENTS_HAVE_AN_UNAMBIGUOUS_CONSTRUCTOR =
+      classes()
+          .that()
+          .areAnnotatedWith("org.springframework.stereotype.Repository")
+          .or()
+          .areAnnotatedWith("org.springframework.stereotype.Service")
+          .or()
+          .areAnnotatedWith("org.springframework.stereotype.Component")
+          .or()
+          .areAnnotatedWith("org.springframework.web.bind.annotation.RestController")
+          .should(haveAConstructorSpringCanChoose())
+          .as(
+              "D20: a scanned Spring component must have exactly one constructor, or mark one"
+                  + " @Autowired — otherwise component scan falls back to a no-arg constructor that"
+                  + " does not exist and the application fails to start");
+
+  private static ArchCondition<JavaClass> haveAConstructorSpringCanChoose() {
+    return new ArchCondition<>("have a constructor Spring can choose") {
+      @Override
+      public void check(JavaClass item, ConditionEvents events) {
+        var constructors =
+            item.getConstructors().stream()
+                .filter(constructor -> !constructor.getModifiers().contains(JavaModifier.SYNTHETIC))
+                .toList();
+        if (constructors.size() <= 1) {
+          return;
+        }
+        boolean autowired =
+            constructors.stream()
+                .anyMatch(
+                    constructor ->
+                        constructor.getAnnotations().stream()
+                            .anyMatch(
+                                annotation ->
+                                    annotation
+                                        .getRawType()
+                                        .getName()
+                                        .equals(
+                                            "org.springframework.beans.factory.annotation.Autowired")));
+        if (!autowired) {
+          events.add(
+              SimpleConditionEvent.violated(
+                  item,
+                  item.getName()
+                      + " declares "
+                      + constructors.size()
+                      + " constructors and marks none @Autowired;"
+                      + " component scan cannot choose one"));
+        }
+      }
+    };
+  }
 }