diff --git a/apps/api/prisma/migrations/20260828053415_add_good_family_id/migration.sql b/apps/api/prisma/migrations/20260828053415_add_good_family_id/migration.sql
new file mode 100644
index 0000000..9dc2ee2
--- /dev/null
+++ b/apps/api/prisma/migrations/20260828053415_add_good_family_id/migration.sql
@@ -0,0 +1,14 @@
+-- AlterTable
+ALTER TABLE "goods" ADD COLUMN     "family_id" BIGINT;
+
+-- CreateIndex
+CREATE INDEX "goods_family_id_idx" ON "goods"("family_id");
+
+-- AddForeignKey
+ALTER TABLE "goods" ADD CONSTRAINT "goods_family_id_fkey" FOREIGN KEY ("family_id") REFERENCES "product_families"("family_id") ON DELETE SET NULL ON UPDATE NO ACTION;
+
+-- Backfill: Good 的族 = 其主链接所属族（派生数据，后续由服务层联动维护）
+UPDATE "goods" SET "family_id" = (
+  SELECT "o"."family_id" FROM "origin_goods" "o"
+  WHERE "o"."origin_good_id" = "goods"."origin_good_id"
+);
diff --git a/apps/api/prisma/schema.prisma b/apps/api/prisma/schema.prisma
index 5929a2c..270aa76 100644
--- a/apps/api/prisma/schema.prisma
+++ b/apps/api/prisma/schema.prisma
@@ -212,6 +212,7 @@ model Position {
 model Good {
   id           BigInt   @id @default(autoincrement()) @map("good_id")
   originGoodId BigInt   @map("origin_good_id")
+  familyId     BigInt?  @map("family_id")
   countryId    BigInt   @map("country_id")
   categoryId   BigInt   @map("category_id")
   tagId        BigInt?  @map("tag_id")
@@ -223,6 +224,7 @@ model Good {
   updatedAt    DateTime @default(now()) @updatedAt @map("updated_at") @db.Timestamptz(6)
 
   originGood OriginGood @relation(fields: [originGoodId], references: [id], onDelete: Restrict, onUpdate: NoAction)
+  family     ProductFamily? @relation(fields: [familyId], references: [id], onDelete: SetNull, onUpdate: NoAction)
   country    Country    @relation(fields: [countryId], references: [id], onDelete: Restrict, onUpdate: NoAction)
   category   Category   @relation(fields: [categoryId], references: [id], onDelete: Restrict, onUpdate: NoAction)
   tag        Tag?       @relation(fields: [tagId], references: [id], onDelete: SetNull, onUpdate: NoAction)
@@ -231,6 +233,7 @@ model Good {
   mergedOriginGoods GoodOriginGood[]
 
   @@index([originGoodId])
+  @@index([familyId])
   @@index([countryId])
   @@index([categoryId])
   @@index([tagId])
@@ -292,6 +295,7 @@ model ProductFamily {
 
   originGoods    OriginGood[]
   priceOverrides FamilyPriceOverride[]
+  goods          Good[]
   country        Country?  @relation(fields: [countryId], references: [id], onDelete: SetNull, onUpdate: NoAction)
   category       Category? @relation(fields: [categoryId], references: [id], onDelete: SetNull, onUpdate: NoAction)
 
diff --git a/plans/feature/product-family-public-feature.md b/plans/feature/product-family-public-feature.md
new file mode 100644
index 0000000..9d8f67e
--- /dev/null
+++ b/plans/feature/product-family-public-feature.md
@@ -0,0 +1,49 @@
+# 产品族三期（公开读路径灰度 + Good.familyId）实施计划
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** `Good.familyId` 落库并在公开详情中灰度暴露族数据（并集尺码表/包装/五维价格矩阵），零新增公开端点、开关可秒回退（设计 D4）。
+
+**Architecture:** `Good.familyId` 是**派生数据**：创建时自动取主链接的族；族成员变更时联动刷新。公开详情的族块直接来自 `ProductFamily` 物化 JSON（零额外查询），由环境变量 `PUBLIC_DETAIL_FROM_FAMILY`（默认 false）控制是否输出。
+
+**明确的范围边界:** 列表/筛选/排序仍基于主源 `goodPrice`（SQL 层无法廉价解析族矩阵 JSON），仅详情页价格以矩阵为准；`good_origin_goods` 转只读保留，观察期后再删（另行任务）。
+
+---
+
+### Task 1: Schema + 迁移 + 回填
+
+- [ ] `Good` model 增加 `familyId BigInt? @map("family_id")` + `family ProductFamily? @relation(... SetNull)` + `@@index([familyId])`；`ProductFamily` relations 加 `goods Good[]`。
+- [ ] `npx prisma migrate dev --name add_good_family_id`，迁移 SQL 末尾追加回填：
+  `UPDATE goods SET family_id = (SELECT family_id FROM origin_goods WHERE origin_goods.origin_good_id = goods.origin_good_id);`
+- [ ] Commit `feat(api): good family_id column with backfill`
+
+### Task 2: Good.familyId 派生逻辑
+
+- [ ] `goods.service.ts`：`create` / `batchCreate` / `createCustom` 创建 Good 时 `familyId = originGood.familyId`（含 custom 直挂的 familyId）；
+- [ ] `product-families.service.ts`：`updateMembers` / `tryAutoAttachToFamily`（sync.service）成员移动后联动
+  `UPDATE goods SET family_id`（`good.updateMany({ where: { originGoodId: { in: movedIds } }, data: { familyId } })`，摘除时置 null）。
+- [ ] 测试：创建 Good 带 familyId、成员移动联动（集成）。
+- [ ] Commit `feat(api): derive good family membership`
+
+### Task 3: 公开详情族块（灰度开关）
+
+- [ ] `PUBLIC_GOOD_INCLUDE` 的 `originGood.include` 加 `family: { select: { id, familyCode, familyName, sizeChart, packageSpecs, priceMatrix } }`；
+- [ ] `PublicGoodDetailDto` 增加可选 `family` 字段；`toPublicGoodDetail` 在
+  `process.env.PUBLIC_DETAIL_FROM_FAMILY === 'true'` 且 `originGood.family` 存在时输出
+  `{ familyId, familyCode, familyName, sizes, colors, crafts, logistics, sizeChart, packageSpecs, priceMatrix, minPrice }`
+  （minPrice = 矩阵 rows 最低价）；开关关闭时**完全不含**该字段（响应形状与现状逐字节一致）。
+- [ ] 测试：开关两态（spec 内直接改 env 再实例化 service）、族块字段正确、无族 Good 字段缺失。
+- [ ] Commit `feat(api): public good detail family block behind flag`
+
+### Task 4: 验证 + 文档 + 合并
+
+- [ ] api 全量测试两轮全绿；`pnpm -r build` 通过。
+- [ ] 冒烟：开关 off 响应无 family 键；on 时含 DG001 族块（470 格）。
+- [ ] 更新 `docs/references/structs.md`（Good.familyId、公开详情族块、环境变量）、`docs/references/product-center.md`（三期行为与边界声明）、`README.md` 环境变量说明。
+- [ ] 遵循 verification-before-completion；合并回 develop。
+
+## Self-Review
+
+- 设计 §10.2 复用原则 ✓（零新增端点）；§5.3 Good.familyId ✓；§12.6 读路径灰度 ✓（开关粒度为详情族块）；
+- 列表价/筛选不动已作为边界显式声明（SQL 不可行 + 避免展示价与筛选价不一致）；
+- `good_origin_goods` 保留只读，删除另立任务（观察期要求）。