fix(channels): 后端按次/图片计费跳过 token 区间重叠校验

前端在上一个 commit 已对 image / per_request 模式跳过 unbounded-last
和重叠检查, 但保存时后端仍按 token 语义校验, 导致添加第二个图片层级
时报错:

  invalid pricing intervals for platform 'openai' models
  [gpt-image-2 gpt-image-1.5 gpt-image-1]:
    interval #1: unbounded interval (max_tokens=null) must be the last one

ValidateIntervals 加 mode 参数, 与前端校验逻辑对齐:
- token 模式行为不变 (区间重叠 / last-unlimited 仍校验)
- per_request / image 模式跳过区间重叠和 last-unlimited 检查,
  保留单条 min/max 自洽校验与价格非负校验。

调用方 validatePricingIntervals 把 pricing.BillingMode 透给校验器。
既有单测全部加上 BillingModeToken 显式参数, 新增 3 个 image 模式用例
(允许多条 unbounded / 仍拒绝负价 / 仍拒绝 max <= min)。

backend/internal/service/channel.go

@@ -262,10 +262,17 @@ func deepCopyFeaturesConfig(src map[string]any) map[string]any {
 }
 
 // ValidateIntervals 校验区间列表的合法性。
-// 规则：MinTokens >= 0；MaxTokens 若非 nil 则 > 0 且 > MinTokens；
+//
-// 所有价格字段 >= 0；区间按 MinTokens 排序后无重叠（(min, max] 语义）；
+// mode 决定区间语义：
-// 无界区间（MaxTokens=nil）必须是最后一个。间隙允许（回退默认价格）。
+//   - BillingModeToken（含空值）：区间是上下文 token 数分段 (min, max]，
-func ValidateIntervals(intervals []PricingInterval) error {
+//     按 MinTokens 排序后无重叠，无界区间（MaxTokens=nil）必须是最后一个。
+//   - BillingModePerRequest / BillingModeImage：区间是按 tier_label
+//     (1K/2K/4K 等) 分层，匹配走 label 不依赖 min/max，因此跳过区间重叠
+//     与 last-unlimited 校验，仅做单条字段自洽（min/max/价格非负）检查。
+//
+// 通用规则：MinTokens >= 0；MaxTokens 若非 nil 则 > 0 且 > MinTokens；
+// 所有价格字段 >= 0。
+func ValidateIntervals(intervals []PricingInterval, mode BillingMode) error {
 	if len(intervals) == 0 {
 		return nil
 	}
@@ -280,6 +287,11 @@ func ValidateIntervals(intervals []PricingInterval) error {
 			return err
 		}
 	}
+
+	// per_request / image 模式按 tier_label 匹配，不做 token 区间重叠校验
+	if mode == BillingModePerRequest || mode == BillingModeImage {
+		return nil
+	}
 	return validateIntervalOverlap(sorted)
 }
 

backend/internal/service/channel_service.go

@@ -951,7 +951,7 @@ func validateNoConflictingMappings(mapping map[string]map[string]string) error {
 
 func validatePricingIntervals(pricingList []ChannelModelPricing) error {
 	for _, pricing := range pricingList {
-		if err := ValidateIntervals(pricing.Intervals); err != nil {
+		if err := ValidateIntervals(pricing.Intervals, pricing.BillingMode); err != nil {
 			return infraerrors.BadRequest(
 				"INVALID_PRICING_INTERVALS",
 				fmt.Sprintf("invalid pricing intervals for platform '%s' models %v: %v",

backend/internal/service/channel_test.go

@@ -311,8 +311,8 @@ func TestChannelClone_EdgeCases(t *testing.T) {
 // --- ValidateIntervals ---
 
 func TestValidateIntervals_Empty(t *testing.T) {
-	require.NoError(t, ValidateIntervals(nil))
+	require.NoError(t, ValidateIntervals(nil, BillingModeToken))
-	require.NoError(t, ValidateIntervals([]PricingInterval{}))
+	require.NoError(t, ValidateIntervals([]PricingInterval{}, BillingModeToken))
 }
 
 func TestValidateIntervals_ValidIntervals(t *testing.T) {
@@ -357,7 +357,7 @@ func TestValidateIntervals_ValidIntervals(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			require.NoError(t, ValidateIntervals(tt.intervals))
+			require.NoError(t, ValidateIntervals(tt.intervals, BillingModeToken))
 		})
 	}
 }
@@ -366,7 +366,7 @@ func TestValidateIntervals_NegativeMinTokens(t *testing.T) {
 	intervals := []PricingInterval{
 		{MinTokens: -1, MaxTokens: testPtrInt(100), InputPrice: testPtrFloat64(1e-6)},
 	}
-	err := ValidateIntervals(intervals)
+	err := ValidateIntervals(intervals, BillingModeToken)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "min_tokens")
 	require.Contains(t, err.Error(), ">= 0")
@@ -376,7 +376,7 @@ func TestValidateIntervals_MaxTokensZero(t *testing.T) {
 	intervals := []PricingInterval{
 		{MinTokens: 0, MaxTokens: testPtrInt(0), InputPrice: testPtrFloat64(1e-6)},
 	}
-	err := ValidateIntervals(intervals)
+	err := ValidateIntervals(intervals, BillingModeToken)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "max_tokens")
 	require.Contains(t, err.Error(), "> 0")
@@ -386,7 +386,7 @@ func TestValidateIntervals_MaxLessThanMin(t *testing.T) {
 	intervals := []PricingInterval{
 		{MinTokens: 100, MaxTokens: testPtrInt(50), InputPrice: testPtrFloat64(1e-6)},
 	}
-	err := ValidateIntervals(intervals)
+	err := ValidateIntervals(intervals, BillingModeToken)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "max_tokens")
 	require.Contains(t, err.Error(), "> min_tokens")
@@ -396,7 +396,7 @@ func TestValidateIntervals_MaxEqualsMin(t *testing.T) {
 	intervals := []PricingInterval{
 		{MinTokens: 100, MaxTokens: testPtrInt(100), InputPrice: testPtrFloat64(1e-6)},
 	}
-	err := ValidateIntervals(intervals)
+	err := ValidateIntervals(intervals, BillingModeToken)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "max_tokens")
 	require.Contains(t, err.Error(), "> min_tokens")
@@ -407,7 +407,7 @@ func TestValidateIntervals_NegativePrice(t *testing.T) {
 	intervals := []PricingInterval{
 		{MinTokens: 0, MaxTokens: testPtrInt(100), InputPrice: &negPrice},
 	}
-	err := ValidateIntervals(intervals)
+	err := ValidateIntervals(intervals, BillingModeToken)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "input_price")
 	require.Contains(t, err.Error(), ">= 0")
@@ -418,7 +418,7 @@ func TestValidateIntervals_OverlappingIntervals(t *testing.T) {
 		{MinTokens: 0, MaxTokens: testPtrInt(200), InputPrice: testPtrFloat64(1e-6)},
 		{MinTokens: 100, MaxTokens: testPtrInt(300), InputPrice: testPtrFloat64(2e-6)},
 	}
-	err := ValidateIntervals(intervals)
+	err := ValidateIntervals(intervals, BillingModeToken)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "overlap")
 }
@@ -428,12 +428,43 @@ func TestValidateIntervals_UnboundedNotLast(t *testing.T) {
 		{MinTokens: 0, MaxTokens: nil, InputPrice: testPtrFloat64(1e-6)},
 		{MinTokens: 128000, MaxTokens: testPtrInt(256000), InputPrice: testPtrFloat64(2e-6)},
 	}
-	err := ValidateIntervals(intervals)
+	err := ValidateIntervals(intervals, BillingModeToken)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "unbounded")
 	require.Contains(t, err.Error(), "last")
 }
 
+func TestValidateIntervals_ImageModeAllowsMultipleUnboundedTiers(t *testing.T) {
+	// image / per_request 按 tier_label 匹配，多条 min=0/max=nil 是合法形态。
+	intervals := []PricingInterval{
+		{MinTokens: 0, MaxTokens: nil, TierLabel: "1K", PerRequestPrice: testPtrFloat64(0.04)},
+		{MinTokens: 0, MaxTokens: nil, TierLabel: "2K", PerRequestPrice: testPtrFloat64(0.06)},
+		{MinTokens: 0, MaxTokens: nil, TierLabel: "4K", PerRequestPrice: testPtrFloat64(0.08)},
+	}
+	require.NoError(t, ValidateIntervals(intervals, BillingModeImage))
+	require.NoError(t, ValidateIntervals(intervals, BillingModePerRequest))
+}
+
+func TestValidateIntervals_ImageModeStillRejectsNegativePrice(t *testing.T) {
+	// image 模式只跳过区间重叠校验，单条字段自洽（价格非负）仍要校验。
+	intervals := []PricingInterval{
+		{MinTokens: 0, MaxTokens: nil, TierLabel: "1K", PerRequestPrice: testPtrFloat64(-1)},
+	}
+	err := ValidateIntervals(intervals, BillingModeImage)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "must be >= 0")
+}
+
+func TestValidateIntervals_ImageModeStillRejectsBadMaxTokens(t *testing.T) {
+	// image 模式仍校验 max <= min 这种单条不合法。
+	intervals := []PricingInterval{
+		{MinTokens: 100, MaxTokens: testPtrInt(50), TierLabel: "1K", PerRequestPrice: testPtrFloat64(0.04)},
+	}
+	err := ValidateIntervals(intervals, BillingModeImage)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "must be > min_tokens")
+}
+
 func TestSupportedModels_ExactKeysAndPricing(t *testing.T) {
 	ch := &Channel{
 		ModelPricing: []ChannelModelPricing{