diff --git a/backend/model/board_seed_test.go b/backend/model/board_seed_test.go
new file mode 100644
index 0000000..76be51d
--- /dev/null
+++ b/backend/model/board_seed_test.go
@@ -0,0 +1,42 @@
+package model
+
+import (
+	"testing"
+
+	"github.com/glebarez/sqlite"
+	"gorm.io/gorm"
+)
+
+// 默认板块只在空库播种：站长改名/删除板块后重启不得复活默认板块（0.2.1 事故回归）
+func TestSeedDefaultBoardsOnlyWhenEmpty(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	if err != nil {
+		t.Fatalf("open sqlite: %v", err)
+	}
+	if err := db.AutoMigrate(&Board{}); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+
+	// 空库首启：播种 4 个默认板块
+	seedDefaultBoards(db)
+	var n int64
+	db.Model(&Board{}).Count(&n)
+	if n != 4 {
+		t.Fatalf("空库应播种 4 个默认板块，实际 %d", n)
+	}
+
+	// 站长改名后重启：不再复活默认板块
+	if err := db.Model(&Board{}).Where("name = ?", "综合讨论").Update("name", "新综合").Error; err != nil {
+		t.Fatalf("rename: %v", err)
+	}
+	seedDefaultBoards(db)
+	db.Model(&Board{}).Count(&n)
+	if n != 4 {
+		t.Fatalf("改名后重启不应重复播种，实际 %d 个板块", n)
+	}
+	var revived int64
+	db.Model(&Board{}).Where("name = ?", "综合讨论").Count(&revived)
+	if revived != 0 {
+		t.Fatal("默认板块「综合讨论」被复活")
+	}
+}
diff --git a/backend/model/db.go b/backend/model/db.go
index d5e1688..e92ce42 100644
--- a/backend/model/db.go
+++ b/backend/model/db.go
@@ -382,20 +382,23 @@ func backfillBoardDefaults(db *gorm.DB) {
 	}
 }
 
-// seedDefaultBoards 写入默认板块
+// seedDefaultBoards 仅在板块表为空（全新站点首启）时写入默认板块。
+// 曾按「名字是否存在」补种：站长改名板块后每次重启都会复活一套默认板块
+// （真实事故：0.2.1 重启后默认 4 板块重现）。表里已有任何未删除板块即视为已初始化。
 func seedDefaultBoards(db *gorm.DB) {
+	var count int64
+	db.Model(&Board{}).Count(&count)
+	if count > 0 {
+		return
+	}
 	defaults := []Board{
 		{Name: "综合讨论", Description: "什么都可以聊", Icon: "message-circle", SortOrder: 1, PostPolicy: BoardPostPolicyAll, Visible: true},
 		{Name: "技术分享", Description: "分享技术心得与问题", Icon: "code", SortOrder: 2, PostPolicy: BoardPostPolicyAll, Visible: true},
 		{Name: "问答求助", Description: "提问与解答", Icon: "help-circle", SortOrder: 3, PostPolicy: BoardPostPolicyAll, Visible: true},
 		{Name: "闲聊灌水", Description: "轻松闲聊", Icon: "coffee", SortOrder: 4, PostPolicy: BoardPostPolicyAll, Visible: true},
 	}
-	for _, b := range defaults {
-		var count int64
-		db.Model(&Board{}).Where("name = ?", b.Name).Count(&count)
-		if count == 0 {
-			_ = db.Create(&b).Error
-		}
+	for i := range defaults {
+		_ = db.Create(&defaults[i]).Error
 	}
 }