diff --git a/plugins/wasm-go/extensions/ai-statistics/main.go b/plugins/wasm-go/extensions/ai-statistics/main.go
index 380e0d5bc..fa5f80879 100644
--- a/plugins/wasm-go/extensions/ai-statistics/main.go
+++ b/plugins/wasm-go/extensions/ai-statistics/main.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"strings"
 
@@ -52,79 +53,66 @@ func onHttpResponseHeaders(ctx wrapper.HttpContext, config AIStatisticsConfig, l
 	return types.ActionContinue
 }
 
-func getLastChunk(data []byte) []byte {
-	chunks := strings.Split(strings.TrimSpace(string(data)), "\n\n")
-	length := len(chunks)
-	if length < 2 {
+func onHttpStreamingBody(ctx wrapper.HttpContext, config AIStatisticsConfig, data []byte, endOfStream bool, log wrapper.Log) []byte {
+	model, inputToken, outputToken, ok := getUsage(data)
+	if !ok {
 		return data
 	}
-	// ai-proxy append extra usage chunk
-	return []byte(chunks[length-1])
-}
-
-func onHttpStreamingBody(ctx wrapper.HttpContext, config AIStatisticsConfig, data []byte, endOfStream bool, log wrapper.Log) []byte {
-	lastChunk := getLastChunk(data)
-	modelObj := gjson.GetBytes(lastChunk, "model")
-	inputTokenObj := gjson.GetBytes(lastChunk, "usage.prompt_tokens")
-	outputTokenObj := gjson.GetBytes(lastChunk, "usage.completion_tokens")
-	if modelObj.Exists() && inputTokenObj.Exists() && outputTokenObj.Exists() {
-		ctx.SetContext("model", modelObj.String())
-		ctx.SetContext("input_token", inputTokenObj.Int())
-		ctx.SetContext("output_token", outputTokenObj.Int())
-	}
-
-	if endOfStream {
-		var route, cluster string
-		if raw, err := proxywasm.GetProperty([]string{"route_name"}); err == nil {
-			route = string(raw)
-		}
-		if raw, err := proxywasm.GetProperty([]string{"cluster_name"}); err == nil {
-			cluster = string(raw)
-		}
-		model, ok := ctx.GetContext("model").(string)
-		if !ok {
-			log.Error("Get model failed!")
-			return data
-		}
-		inputToken, ok := ctx.GetContext("input_token").(int64)
-		if !ok {
-			log.Error("Get input_token failed!")
-			return data
-		}
-		outputToken, ok := ctx.GetContext("output_token").(int64)
-		if !ok {
-			log.Error("Get output_token failed!")
-			return data
-		}
-		config.incrementCounter("route."+route+".upstream."+cluster+".model."+model+".input_token", uint64(inputToken), log)
-		config.incrementCounter("route."+route+".upstream."+cluster+".model."+model+".output_token", uint64(outputToken), log)
-		proxywasm.SetProperty([]string{"model"}, []byte(model))
-		proxywasm.SetProperty([]string{"input_token"}, []byte(fmt.Sprint(inputToken)))
-		proxywasm.SetProperty([]string{"output_token"}, []byte(fmt.Sprint(outputToken)))
-	}
-
+	setFilterStateData(model, inputToken, outputToken, log)
+	incrementCounter(config, model, inputToken, outputToken, log)
 	return data
 }
 
 func onHttpResponseBody(ctx wrapper.HttpContext, config AIStatisticsConfig, body []byte, log wrapper.Log) types.Action {
-	modeObj := gjson.GetBytes(body, "model")
-	inputTokenObj := gjson.GetBytes(body, "usage.prompt_tokens")
-	outputTokenObj := gjson.GetBytes(body, "usage.completion_tokens")
-	if !modeObj.Exists() {
-		log.Error("Get model failed")
+	model, inputToken, outputToken, ok := getUsage(body)
+	if !ok {
 		return types.ActionContinue
 	}
-	if !inputTokenObj.Exists() {
-		log.Error("Get input_token failed")
-		return types.ActionContinue
+	setFilterStateData(model, inputToken, outputToken, log)
+	incrementCounter(config, model, inputToken, outputToken, log)
+	return types.ActionContinue
+}
+
+func getUsage(data []byte) (model string, inputTokenUsage int64, outputTokenUsage int64, ok bool) {
+	chunks := bytes.Split(bytes.TrimSpace(data), []byte("\n\n"))
+	for _, chunk := range chunks {
+		// the feature strings are used to identify the usage data, like:
+		// {"model":"gpt2","usage":{"prompt_tokens":1,"completion_tokens":1}}
+		if !bytes.Contains(chunk, []byte("prompt_tokens")) {
+			continue
+		}
+		if !bytes.Contains(chunk, []byte("completion_tokens")) {
+			continue
+		}
+		modelObj := gjson.GetBytes(chunk, "model")
+		inputTokenObj := gjson.GetBytes(chunk, "usage.prompt_tokens")
+		outputTokenObj := gjson.GetBytes(chunk, "usage.completion_tokens")
+		if modelObj.Exists() && inputTokenObj.Exists() && outputTokenObj.Exists() {
+			model = modelObj.String()
+			inputTokenUsage = inputTokenObj.Int()
+			outputTokenUsage = outputTokenObj.Int()
+			ok = true
+			return
+		}
 	}
-	if !outputTokenObj.Exists() {
-		log.Error("Get output_token failed")
-		return types.ActionContinue
+	return
+}
+
+// setFilterData sets the input_token and output_token in the filter state.
+// ai-token-ratelimit will use these values to calculate the total token usage.
+func setFilterStateData(model string, inputToken int64, outputToken int64, log wrapper.Log) {
+	if e := proxywasm.SetProperty([]string{"model"}, []byte(model)); e != nil {
+		log.Errorf("failed to set model in filter state: %v", e)
 	}
-	model := modeObj.String()
-	inputToken := inputTokenObj.Int()
-	outputToken := outputTokenObj.Int()
+	if e := proxywasm.SetProperty([]string{"input_token"}, []byte(fmt.Sprintf("%d", inputToken))); e != nil {
+		log.Errorf("failed to set input_token in filter state: %v", e)
+	}
+	if e := proxywasm.SetProperty([]string{"output_token"}, []byte(fmt.Sprintf("%d", outputToken))); e != nil {
+		log.Errorf("failed to set output_token in filter state: %v", e)
+	}
+}
+
+func incrementCounter(config AIStatisticsConfig, model string, inputToken int64, outputToken int64, log wrapper.Log) {
 	var route, cluster string
 	if raw, err := proxywasm.GetProperty([]string{"route_name"}); err == nil {
 		route = string(raw)
@@ -134,10 +122,4 @@ func onHttpResponseBody(ctx wrapper.HttpContext, config AIStatisticsConfig, body
 	}
 	config.incrementCounter("route."+route+".upstream."+cluster+".model."+model+".input_token", uint64(inputToken), log)
 	config.incrementCounter("route."+route+".upstream."+cluster+".model."+model+".output_token", uint64(outputToken), log)
-
-	proxywasm.SetProperty([]string{"model"}, []byte(model))
-	proxywasm.SetProperty([]string{"input_token"}, []byte(fmt.Sprint(inputToken)))
-	proxywasm.SetProperty([]string{"output_token"}, []byte(fmt.Sprint(outputToken)))
-
-	return types.ActionContinue
 }