fix(price): add default token estimate for tiered expression pre-consume

relay/helper/price.go

@@ -35,6 +35,11 @@ func modelPriceNotConfiguredError(modelName string, userId int) error {
 // https://docs.claude.com/en/docs/build-with-claude/prompt-caching#1-hour-cache-duration
 const claudeCacheCreation1hMultiplier = 6 / 3.75
 
+// defaultTieredPreConsumeMaxTokens is the fallback completion-token estimate
+// used for tiered expression pre-consume when the client omits max_tokens, so
+// the pre-consumed quota still reflects a plausible output cost in paid groups.
+const defaultTieredPreConsumeMaxTokens = 8192
+
 // HandleGroupRatio checks for "auto_group" in the context and updates the group ratio and relayInfo.UsingGroup if present
 func HandleGroupRatio(ctx *gin.Context, relayInfo *relaycommon.RelayInfo) types.GroupRatioInfo {
 	groupRatioInfo := types.GroupRatioInfo{
@@ -244,9 +249,9 @@ func modelPriceHelperTiered(c *gin.Context, info *relaycommon.RelayInfo, promptT
 		return types.PriceData{}, fmt.Errorf("model %s is configured as tiered_expr but has no billing expression", info.OriginModelName)
 	}
 
-	estimatedCompletionTokens := 0
-	if meta.MaxTokens != 0 {
-		estimatedCompletionTokens = meta.MaxTokens
+	estimatedCompletionTokens := meta.MaxTokens
+	if estimatedCompletionTokens == 0 && groupRatioInfo.GroupRatio != 0 {
+		estimatedCompletionTokens = defaultTieredPreConsumeMaxTokens
 	}
 
 	requestInput, err := ResolveIncomingBillingExprRequestInput(c, info)