diff --git a/backend/internal/service/rate_limit_429_cooldown_test.go b/backend/internal/service/rate_limit_429_cooldown_test.go
index fb7e0dd7af..96fc199096 100644
--- a/backend/internal/service/rate_limit_429_cooldown_test.go
+++ b/backend/internal/service/rate_limit_429_cooldown_test.go
@@ -97,6 +97,45 @@ func TestHandle429_FallbackDisabledSkipsLocalMark(t *testing.T) {
 	require.Zero(t, accountRepo.rateLimitCalls)
 }
 
+// Anthropic 无 reset 头的 429（如 Extra usage required）也应走兜底冷却，
+// 否则账号永不冷却，调度器会让每个请求反复撞同一批 429 账号（旋转木马）。
+func TestHandle429_AnthropicNoResetTimeUsesFallbackCooldown(t *testing.T) {
+	accountRepo := &rateLimit429AccountRepoStub{}
+	settingRepo := newMockSettingRepo()
+	data, _ := json.Marshal(RateLimit429CooldownSettings{Enabled: true, CooldownSeconds: 12})
+	settingRepo.data[SettingKeyRateLimit429CooldownSettings] = string(data)
+
+	settingSvc := NewSettingService(settingRepo, &config.Config{})
+	svc := NewRateLimitService(accountRepo, nil, &config.Config{}, nil, nil)
+	svc.SetSettingService(settingSvc)
+
+	account := &Account{ID: 45, Platform: PlatformAnthropic, Type: AccountTypeOAuth}
+	before := time.Now()
+	svc.handle429(context.Background(), account, http.Header{}, []byte(`{"error":{"type":"rate_limit_error","message":"Extra usage required"}}`))
+	after := time.Now()
+
+	require.Equal(t, 1, accountRepo.rateLimitCalls)
+	require.Equal(t, int64(45), accountRepo.lastRateLimitID)
+	require.True(t, !accountRepo.lastRateLimitReset.Before(before.Add(12*time.Second)) && !accountRepo.lastRateLimitReset.After(after.Add(12*time.Second)))
+}
+
+// 管理端关闭兜底冷却时，Anthropic 无 reset 头的 429 保持旧行为：不标记账号。
+func TestHandle429_AnthropicNoResetTimeFallbackDisabledSkipsMark(t *testing.T) {
+	accountRepo := &rateLimit429AccountRepoStub{}
+	settingRepo := newMockSettingRepo()
+	data, _ := json.Marshal(RateLimit429CooldownSettings{Enabled: false, CooldownSeconds: 12})
+	settingRepo.data[SettingKeyRateLimit429CooldownSettings] = string(data)
+
+	settingSvc := NewSettingService(settingRepo, &config.Config{})
+	svc := NewRateLimitService(accountRepo, nil, &config.Config{}, nil, nil)
+	svc.SetSettingService(settingSvc)
+
+	account := &Account{ID: 46, Platform: PlatformAnthropic, Type: AccountTypeOAuth}
+	svc.handle429(context.Background(), account, http.Header{}, []byte(`{"error":{"type":"rate_limit_error","message":"Extra usage required"}}`))
+
+	require.Zero(t, accountRepo.rateLimitCalls)
+}
+
 func TestHandle429_FallbackUsesDefaultSecondsWhenSettingServiceMissing(t *testing.T) {
 	accountRepo := &rateLimit429AccountRepoStub{}
 	cfg := &config.Config{}
diff --git a/backend/internal/service/ratelimit_service.go b/backend/internal/service/ratelimit_service.go
index 50d38e7d13..100b240785 100644
--- a/backend/internal/service/ratelimit_service.go
+++ b/backend/internal/service/ratelimit_service.go
@@ -994,12 +994,15 @@ func (s *RateLimitService) handle429(ctx context.Context, account *Account, head
 		}
 
 		// Anthropic 平台：没有限流重置时间的 429 可能是非真实限流（如 Extra usage required），
-		// 不标记账号限流状态，直接透传错误给客户端
+		// 不适合按 5h/7d 窗口长时间封禁；但完全不标记会导致账号永不冷却，
+		// 调度器让每个请求反复撞同一批持续 429 的账号（failover 预算被白白烧掉，
+		// 客户端稳定收到 429）。因此同样走可配置的秒级兜底回避，管理端可调大或关闭。
 		if account.Platform == PlatformAnthropic {
-			slog.Warn("rate_limit_429_no_reset_time_skipped",
+			slog.Warn("rate_limit_429_no_reset_time",
 				"account_id", account.ID,
 				"platform", account.Platform,
 				"reason", "no rate limit reset time in headers, likely not a real rate limit")
+			s.apply429FallbackRateLimit(ctx, account, "anthropic_no_reset_time")
 			return
 		}