diff --git a/internal/handler/gateway.go b/internal/handler/gateway.go
index 8526656..6f5fd7e 100644
--- a/internal/handler/gateway.go
+++ b/internal/handler/gateway.go
@@ -111,7 +111,9 @@ func (h *GatewayHandler) Cancel(c *gin.Context) {
 }
 
 // Callback POST /api/v2/callback/:method —— 渠道异步回调;经 provider.VerifyCallback → Settle。
-// 已受理(含未知单/幂等/金额不符,都不需要渠道重投)一律回 200。
+// 按 SettleResult 分终态/可重试:not_found/duplicate/ignored/amount_mismatch 都是终态
+// (含 amount_mismatch —— Settle 对其返回非 nil err,但仍是已受理的终态),一律回 200 停投;
+// SettleFailed(暂时性失败)与验签/解析失败(err!=nil 且非 amount_mismatch)是可重试态,回 400 让渠道重投。
 func (h *GatewayHandler) Callback(c *gin.Context) {
 	method := c.Param("method")
 	raw, err := io.ReadAll(http.MaxBytesReader(c.Writer, c.Request.Body, maxOrderBodyBytes))
@@ -126,13 +128,18 @@ 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 {
-		// 验签失败等:回 400 让渠道按策略重投(或人工排障)。
+	switch {
+	case err == nil:
+		c.JSON(http.StatusOK, gin.H{"result": string(res)})
+	case res == gateway.SettleAmountMismatch:
+		// 金额/币种不符是终态,不是可重试的暂时性失败:回 200 受理,让渠道停止重投。
+		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:
+		// SettleFailed/验签失败等:回 400 让渠道按策略重投(或人工排障)。
 		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) {
diff --git a/internal/handler/gateway_test.go b/internal/handler/gateway_test.go
index 84f6644..bced738 100644
--- a/internal/handler/gateway_test.go
+++ b/internal/handler/gateway_test.go
@@ -30,6 +30,12 @@ func (oneResolver) Resolve(sku string) (int64, string, string, string, error) {
 }
 
 func buildEngine(t *testing.T) *gin.Engine {
+	t.Helper()
+	r, _ := buildEngineWithStore(t)
+	return r
+}
+
+func buildEngineWithStore(t *testing.T) (*gin.Engine, *store.OrderStore) {
 	t.Helper()
 	gin.SetMode(gin.TestMode)
 	orders := store.NewOrderStore(model.OpenTestDB(t))
@@ -41,7 +47,7 @@ func buildEngine(t *testing.T) *gin.Engine {
 	g := gateway.New(orders, preg, areg, oneResolver{}, nopEnqueuer{}, "global")
 	r := gin.New()
 	router.SetupV2(r, g)
-	return r
+	return r, orders
 }
 
 func do(t *testing.T, r *gin.Engine, method, path string, body any) (*httptest.ResponseRecorder, map[string]any) {
@@ -99,3 +105,60 @@ func TestV2OrderLifecycle(t *testing.T) {
 		t.Fatalf("cancel = %d %v", wCancel.Code, outCancel)
 	}
 }
+
+// TestV2CallbackAmountMismatchIs200Terminal 覆盖 P2-7 审查发现:金额/币种不符是终态,
+// 渠道无需(也不该)重投,回调必须回 200 停投,而不是 400 触发无限重投。
+func TestV2CallbackAmountMismatchIs200Terminal(t *testing.T) {
+	r, orders := buildEngineWithStore(t)
+
+	w, out := do(t, r, http.MethodPost, "/api/v2/orders", map[string]any{"sku": "pro_year", "method": "fake"})
+	if w.Code != http.StatusOK {
+		t.Fatalf("create code=%d body=%v", w.Code, out)
+	}
+	orderNo := out["data"].(map[string]any)["order_no"].(string)
+
+	atts, err := orders.ListAttemptsByStatus(model.AttemptPending, 10)
+	if err != nil || len(atts) == 0 {
+		t.Fatalf("无 pending 尝试: %v", err)
+	}
+	var ref string
+	for _, a := range atts {
+		if a.OutTradeNo == orderNo {
+			ref = a.ProviderRef
+		}
+	}
+	if ref == "" {
+		t.Fatalf("未找到订单 %s 的尝试", orderNo)
+	}
+
+	// 币种正确但少付(amount_minor=1 << 应收 29990000)→ amount_mismatch,终态,必须 200。
+	wc, outc := do(t, r, http.MethodPost, "/api/v2/callback/fake", map[string]any{
+		"provider_ref": ref, "status": "succeeded", "amount_minor": 1, "currency": "USDT",
+	})
+	if wc.Code != http.StatusOK {
+		t.Fatalf("amount_mismatch callback code=%d body=%v (终态应 200 停投,不应 400 触发无限重投)", wc.Code, outc)
+	}
+	if outc["result"] != string(gateway.SettleAmountMismatch) {
+		t.Fatalf("result = %v, want amount_mismatch", outc["result"])
+	}
+
+	// 订单应仍是 pending(未被误标为已支付)。
+	_, outStatus := do(t, r, http.MethodGet, "/api/v2/orders/"+orderNo, nil)
+	if outStatus["data"].(map[string]any)["status"] != "pending" {
+		t.Fatalf("order status = %v, want pending", outStatus["data"])
+	}
+}
+
+// TestV2CallbackMalformedBodyIs400Transient 验签/解析失败是瞬时态,渠道应重投,故回 400。
+func TestV2CallbackMalformedBodyIs400Transient(t *testing.T) {
+	r := buildEngine(t)
+
+	req := httptest.NewRequest(http.MethodPost, "/api/v2/callback/fake", bytes.NewBufferString("not-json"))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("malformed body callback code=%d, want 400", w.Code)
+	}
+}