docs(v2): P2 计划 settle 代码段同步 T5 修复(瞬时读库错误→SettleFailed)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nMthbVEmQquxBRKb9Fj8u

docs/superpowers/plans/2026-07-10-pay-v2-p2-pipeline.md

@@ -1321,7 +1321,9 @@ func (g *Gateway) Settle(ctx context.Context, ev *provider.PaidEvent) (SettleRes
 		if errors.Is(err, store.ErrAttemptNotFound) {
 			return SettleNotFound, nil
 		}
-		return SettleNotFound, err
+		// 读库瞬时失败是可重试态(SettleFailed),不能与"查无此单"(终态,ack 即弃)
+		// 混淆——否则按 result 决定 ack 的调用方会让渠道停止重投,已付单永不入账。
+		return SettleFailed, err
 	}
 	// 金额/币种核对:币种须一致,实付须 ≥ 应收(允许 crypto 多付,拒少付)。
 	if ev.PaidCurrency != att.Currency || ev.PaidAmountMinor < att.AmountMinor {
@@ -2158,13 +2160,19 @@ func (h *GatewayHandler) Callback(c *gin.Context) {
 	res, err := h.g.HandleCallback(c.Request.Context(), method, provider.CallbackInput{
 		Raw: raw, Headers: headers,
 	})
-	if err != nil {
+	// 按 SettleResult(而非只看 err)分终态/可重试:amount_mismatch 是终态——
-		// 验签失败等:回 400 让渠道按策略重投(或人工排障)。
+	// 重投同一回调永远解决不了,必须回 200 让渠道停投(差错单归 P6 对账/人工);
+	// SettleFailed/验签失败才是可重试态,回 400 让渠道重投。
+	switch {
+	case err == nil:
+		c.JSON(http.StatusOK, gin.H{"result": string(res)})
+	case res == gateway.SettleAmountMismatch:
+		log.Printf("[v2 callback] method=%s 金额/币种不符(终态,已受理停投): %v", method, err)
+		c.JSON(http.StatusOK, gin.H{"result": string(res)})
+	default:
 		log.Printf("[v2 callback] method=%s result=%s err=%v", method, res, err)
 		util.RespondError(c, http.StatusBadRequest, "callback_failed", "回调处理失败")
-		return
 	}
-	c.JSON(http.StatusOK, gin.H{"result": string(res)})
 }
 
 func (h *GatewayHandler) writeCreateErr(c *gin.Context, action, method string, err error) {