diff --git a/plugins/wasm-go/extensions/ai-proxy/provider/claude_to_openai.go b/plugins/wasm-go/extensions/ai-proxy/provider/claude_to_openai.go
index 558371608..d9416270e 100644
--- a/plugins/wasm-go/extensions/ai-proxy/provider/claude_to_openai.go
+++ b/plugins/wasm-go/extensions/ai-proxy/provider/claude_to_openai.go
@@ -788,16 +788,21 @@ func (c *ClaudeToOpenAIConverter) buildClaudeStreamResponse(ctx wrapper.HttpCont
 		log.Debugf("[OpenAI->Claude] Processing usage info - input: %d, output: %d",
 			openaiResponse.Usage.PromptTokens, openaiResponse.Usage.CompletionTokens)
 
+		usage := &claudeTextGenUsage{
+			InputTokens:  openaiResponse.Usage.PromptTokens,
+			OutputTokens: openaiResponse.Usage.CompletionTokens,
+		}
+		if openaiResponse.Usage.PromptTokensDetails != nil {
+			usage.CacheReadInputTokens = openaiResponse.Usage.PromptTokensDetails.CachedTokens
+		}
+
 		// Send message_delta with both stop_reason and usage (Claude protocol requirement)
 		messageDelta := &claudeTextGenStreamResponse{
 			Type: "message_delta",
 			Delta: &claudeTextGenDelta{
 				StopSequence: json.RawMessage("null"), // Explicit null per Claude spec
 			},
-			Usage: &claudeTextGenUsage{
-				InputTokens:  openaiResponse.Usage.PromptTokens,
-				OutputTokens: openaiResponse.Usage.CompletionTokens,
-			},
+			Usage: usage,
 		}
 
 		// Include cached stop_reason if available
diff --git a/plugins/wasm-go/extensions/ai-proxy/provider/claude_to_openai_test.go b/plugins/wasm-go/extensions/ai-proxy/provider/claude_to_openai_test.go
index 94751d770..b490a3591 100644
--- a/plugins/wasm-go/extensions/ai-proxy/provider/claude_to_openai_test.go
+++ b/plugins/wasm-go/extensions/ai-proxy/provider/claude_to_openai_test.go
@@ -859,6 +859,22 @@ func TestClaudeToOpenAIConverter_ConvertReasoningResponseToClaude(t *testing.T)
 	}
 }
 
+func TestClaudeToOpenAIConverter_ConvertOpenAIStreamResponseToClaude_WithCachedTokens(t *testing.T) {
+	converter := &ClaudeToOpenAIConverter{}
+
+	streamChunk := "data: {\"id\":\"chatcmpl-test\",\"model\":\"gpt-4o\",\"choices\":[{\"index\":0,\"delta\":{\"role\":\"assistant\"}}]}\n\n" +
+		"data: {\"id\":\"chatcmpl-test\",\"model\":\"gpt-4o\",\"choices\":[{\"index\":0,\"finish_reason\":\"stop\"}],\"usage\":{\"prompt_tokens\":100,\"completion_tokens\":20,\"total_tokens\":120,\"prompt_tokens_details\":{\"cached_tokens\":60}}}\n\n"
+
+	result, err := converter.ConvertOpenAIStreamResponseToClaude(nil, []byte(streamChunk))
+	require.NoError(t, err)
+
+	resultStr := string(result)
+	assert.Contains(t, resultStr, "\"type\":\"message_delta\"")
+	assert.Contains(t, resultStr, "\"input_tokens\":100")
+	assert.Contains(t, resultStr, "\"output_tokens\":20")
+	assert.Contains(t, resultStr, "\"cache_read_input_tokens\":60")
+}
+
 func TestClaudeToOpenAIConverter_StripCchFromSystemMessage(t *testing.T) {
 	converter := &ClaudeToOpenAIConverter{}