diff --git a/route/question/share.go b/route/question/share.go
index 9e6189e..7cb348a 100644
--- a/route/question/share.go
+++ b/route/question/share.go
@@ -328,7 +328,7 @@ func (c *ttlCache) cleanup() {
 // 社交图标 URL 固定不变，基本永远命中；头像/背景变更时最多延迟 1 小时生效。
 var imageCache = newTTLCache(24)
 
-// 分享图结果缓存，TTL 30 分钟。key 含用户资料指纹，资料变更后自动失效。
+// 分享图结果缓存，TTL 1 小时。key 含用户资料指纹，资料变更后自动失效。
 // 存的是 PNG 编码字节（约 0.2~1MB/张），限制 32 条，总内存 ≤ 32MB。
 var shareCardCache = newTTLCache(32)
 
@@ -561,7 +561,9 @@ func writeShareCardResponse(ctx context.Context, data []byte) {
 }
 
 // shareCardCacheKey 基于用户资料生成缓存指纹。
-// 资料（名称/简介/头像/背景/社交链接）任何一项变更都会导致 key 变化，缓存自动失效。
+// 资料（域名/名称/简介/头像/背景/社交链接）任何一项变更都会导致 key 变化，缓存自动失效。
+// conf 里的 ExternalURL / ShareBackground 不入 key：改配置必须重启，进程内缓存随之清空。
+// 头像、背景走 R2 随机 key（内容不可变），换图即换 URL，也不会出现同名不同图。
 func shareCardCacheKey(user *db.User) string {
 	h := md5.New()
 	fmt.Fprintf(h, "%s|%s|%s|%s|%s|%s|%s|%s|%s|%s",
@@ -948,7 +950,7 @@ func drawQuestionQRCard(canvas *image.RGBA, user *db.User, question *db.Question
 	return nil
 }
 
-// 单题分享图结果缓存，TTL 30 分钟，上限 16 条（1C1G 内存友好）。
+// 单题分享图结果缓存，TTL 1 小时，上限 16 条（1C1G 内存友好）。
 var questionShareCache = newTTLCache(16)
 
 // QuestionShareCard 生成单个问题（问题+回答）的分享卡片图。
@@ -1111,9 +1113,12 @@ func QuestionShareCard(ctx context.Context) {
 }
 
 // questionShareCardCacheKey 基于问题内容与用户资料生成缓存指纹，内容/资料变更自动失效。
+// user.Domain 虽然当前不可改（只在注册时写入），但它进了二维码内容：一旦将来开放改域名，
+// 漏掉它就会出现「卡片二维码指向旧域名」的一小时窗口，这里先按事实把它算进去。
 func questionShareCardCacheKey(user *db.User, question *db.Question) string {
 	h := md5.New()
-	fmt.Fprintf(h, "q|%d|%s|%s|%s|%s|%s", question.ID, question.Content, question.Answer, user.Name, user.Avatar, user.Background)
+	fmt.Fprintf(h, "q|%d|%s|%s|%s|%s|%s|%s",
+		question.ID, question.Content, question.Answer, user.Domain, user.Name, user.Avatar, user.Background)
 	return fmt.Sprintf("qshare:%x", h.Sum(nil))
 }
 
diff --git a/route/question/share_layout_test.go b/route/question/share_layout_test.go
index 8d54e21..251046f 100644
--- a/route/question/share_layout_test.go
+++ b/route/question/share_layout_test.go
@@ -349,6 +349,59 @@ func qrModules(t *testing.T, content string) int {
 	return len(q.Bitmap())
 }
 
+// 缓存 key 必须覆盖所有画进图里的资料：漏一项就会出现「改了资料，卡片还是一小时旧图」。
+func TestShareCardCacheKeysCoverDrawnFields(t *testing.T) {
+	base := db.User{Domain: "d", Name: "n", Intro: "i", Avatar: "a", Background: "b",
+		Acfunlink: "1", Bililink: "2", Weibolink: "3", Bloglink: "4", Xiaohongshulink: "5"}
+	baseKey := shareCardCacheKey(&base)
+
+	userMuts := []struct {
+		field string
+		apply func(u *db.User)
+	}{
+		{"domain", func(u *db.User) { u.Domain = "x" }},
+		{"name", func(u *db.User) { u.Name = "x" }},
+		{"intro", func(u *db.User) { u.Intro = "x" }},
+		{"avatar", func(u *db.User) { u.Avatar = "x" }},
+		{"background", func(u *db.User) { u.Background = "x" }},
+		{"acfun", func(u *db.User) { u.Acfunlink = "x" }},
+		{"bili", func(u *db.User) { u.Bililink = "x" }},
+		{"weibo", func(u *db.User) { u.Weibolink = "x" }},
+		{"blog", func(u *db.User) { u.Bloglink = "x" }},
+		{"xiaohongshu", func(u *db.User) { u.Xiaohongshulink = "x" }},
+	}
+	for _, m := range userMuts {
+		u := base
+		m.apply(&u)
+		if shareCardCacheKey(&u) == baseKey {
+			t.Errorf("user.%s is drawn on the card but not in shareCardCacheKey", m.field)
+		}
+	}
+
+	question := db.Question{Content: "c", Answer: "a"}
+	question.ID = 7
+	qKey := questionShareCardCacheKey(&base, &question)
+	questionMuts := []struct {
+		field string
+		apply func(u *db.User, q *db.Question)
+	}{
+		{"question.ID", func(u *db.User, q *db.Question) { q.ID++ }},
+		{"question.Content", func(u *db.User, q *db.Question) { q.Content = "x" }},
+		{"question.Answer", func(u *db.User, q *db.Question) { q.Answer = "x" }},
+		{"user.Domain", func(u *db.User, q *db.Question) { u.Domain = "x" }},
+		{"user.Name", func(u *db.User, q *db.Question) { u.Name = "x" }},
+		{"user.Avatar", func(u *db.User, q *db.Question) { u.Avatar = "x" }},
+		{"user.Background", func(u *db.User, q *db.Question) { u.Background = "x" }},
+	}
+	for _, m := range questionMuts {
+		u, q := base, question
+		m.apply(&u, &q)
+		if questionShareCardCacheKey(&u, &q) == qKey {
+			t.Errorf("%s is drawn on the question card but not in questionShareCardCacheKey", m.field)
+		}
+	}
+}
+
 // 视觉自检：TEST_PREVIEW=1 时把链接区渲成 PNG，人工确认断行与对齐。
 func TestShareCardLinkPreview(t *testing.T) {
 	if os.Getenv("TEST_PREVIEW") == "" {