diff --git a/src/config/openapi/MANIFEST.sha256 b/src/config/openapi/MANIFEST.sha256
index cf6a74d..7bc41ba 100644
--- a/src/config/openapi/MANIFEST.sha256
+++ b/src/config/openapi/MANIFEST.sha256
@@ -1,6 +1,6 @@
-# source: tech-log-design-package contracts/openapi/studio-v1.yaml @ 06ae075 (master)
-6fc015ca6727af88b7fb0088e02ba97846e1dd79fb0d4fc593cc79f2a3b9795f  studio-v1.yaml
-# source: tech-log-design-package contracts/openapi/public-v1.yaml @ 06ae075 (master)
+# source: tech-log-design-package contracts/openapi/studio-v1.yaml @ 83148b2 (master)
+18dd46898be64b07f7e826409d19347512613ee2e22420028a4a0644f50f37dd  studio-v1.yaml
+# source: tech-log-design-package contracts/openapi/public-v1.yaml @ 83148b2 (master)
 702d6666a8feba9899c7eb7c2a94a0880bcb23b178c7ed2009c6e69d9a1c848c  public-v1.yaml
-# source: tech-log-design-package contracts/openapi/studio-management-v1.yaml @ 06ae075 (master)
+# source: tech-log-design-package contracts/openapi/studio-management-v1.yaml @ 83148b2 (master)
 72650735061fde627f5037571eb986cb758f44a546f065c88408399f8eec4a55  studio-management-v1.yaml
diff --git a/src/config/openapi/studio-v1.yaml b/src/config/openapi/studio-v1.yaml
index ac68d97..fb37387 100644
--- a/src/config/openapi/studio-v1.yaml
+++ b/src/config/openapi/studio-v1.yaml
@@ -1572,7 +1572,10 @@ components:
           properties:
             kind: { type: string, enum: [PROJECT_DECISION] }
             status: { type: string, enum: [PROPOSED, ADOPTED] }
-            decidedOn: { type: string, format: date }
+            # 결정일은 비어 있을 수 있다. 검증은 이것을 경고로만 다루므로(DECIDED_ON_REQUIRED)
+            # 날짜 없이 게시할 수 있는데, 렌더 모델이 필수로 요구하면 그 문서는 미리보기조차
+            # 열리지 않는다 — 두 규칙이 어긋나면 작성자는 "경고라며 왜 안 되냐"를 만난다.
+            decidedOn: { type: [string, "null"], format: date }
             statement: { type: string, maxLength: 100000 }
             rationale: { type: string, maxLength: 100000 }
             consequences: { type: array, maxItems: 50, items: { $ref: "#/components/schemas/OrderedText" } }