diff --git a/service/convert.go b/service/convert.go
index 95acf835ee46..817b64313ef4 100644
--- a/service/convert.go
+++ b/service/convert.go
@@ -465,9 +465,7 @@ func StreamResponseOpenAI2Claude(openAIResponse *dto.ChatCompletionsStreamRespon
 		doneChunk := chosenChoice.FinishReason != nil && *chosenChoice.FinishReason != ""
 		if doneChunk {
 			info.FinishReason = *chosenChoice.FinishReason
-			oaiUsage := openAIResponse.Usage
-			if oaiUsage == nil {
-				oaiUsage = info.ClaudeConvertInfo.Usage
+			if openAIResponse.Usage == nil && info.ClaudeConvertInfo.Usage == nil {
 				// Some upstreams emit finish_reason first, then send a final usage-only chunk.
 				// Defer closing until usage is available so the final message_delta carries it.
 				return claudeResponses
diff --git a/service/convert_test.go b/service/convert_test.go
new file mode 100644
index 000000000000..d397fa117e6a
--- /dev/null
+++ b/service/convert_test.go
@@ -0,0 +1,80 @@
+package service
+
+import (
+	"testing"
+
+	"github.com/QuantumNous/new-api/common"
+	"github.com/QuantumNous/new-api/constant"
+	"github.com/QuantumNous/new-api/dto"
+	relaycommon "github.com/QuantumNous/new-api/relay/common"
+	"github.com/stretchr/testify/require"
+)
+
+func TestStreamResponseOpenAI2ClaudeClosesStopChunkWithoutUpstreamUsage(t *testing.T) {
+	info := &relaycommon.RelayInfo{
+		ClaudeConvertInfo: &relaycommon.ClaudeConvertInfo{
+			LastMessagesType: relaycommon.LastMessageTypeNone,
+			Usage: &dto.Usage{
+				PromptTokens:     10,
+				CompletionTokens: 20,
+			},
+		},
+	}
+
+	content := func(text string) *dto.ChatCompletionsStreamResponse {
+		return &dto.ChatCompletionsStreamResponse{
+			Id:      "chatcmpl-test",
+			Object:  "chat.completion.chunk",
+			Model:   "qwen3.6-plus",
+			Choices: []dto.ChatCompletionsStreamResponseChoice{{Delta: dto.ChatCompletionsStreamResponseChoiceDelta{Content: common.GetPointer(text)}}},
+		}
+	}
+	reasoning := func(text string) *dto.ChatCompletionsStreamResponse {
+		return &dto.ChatCompletionsStreamResponse{
+			Id:      "chatcmpl-test",
+			Object:  "chat.completion.chunk",
+			Model:   "qwen3.6-plus",
+			Choices: []dto.ChatCompletionsStreamResponseChoice{{Delta: dto.ChatCompletionsStreamResponseChoiceDelta{ReasoningContent: common.GetPointer(text)}}},
+		}
+	}
+
+	info.SendResponseCount = 1
+	responses := StreamResponseOpenAI2Claude(reasoning("thinking"), info)
+	require.Len(t, responses, 3)
+	require.Equal(t, "message_start", responses[0].Type)
+	require.Equal(t, "content_block_start", responses[1].Type)
+	require.Equal(t, "content_block_delta", responses[2].Type)
+
+	info.SendResponseCount = 2
+	responses = StreamResponseOpenAI2Claude(content("hello"), info)
+	require.Len(t, responses, 3)
+	require.Equal(t, "content_block_stop", responses[0].Type)
+	require.Equal(t, 0, responses[0].GetIndex())
+	require.Equal(t, "content_block_start", responses[1].Type)
+	require.Equal(t, 1, responses[1].GetIndex())
+	require.Equal(t, "content_block_delta", responses[2].Type)
+
+	finishReason := constant.FinishReasonStop
+	responses = StreamResponseOpenAI2Claude(&dto.ChatCompletionsStreamResponse{
+		Id:     "chatcmpl-test",
+		Object: "chat.completion.chunk",
+		Model:  "qwen3.6-plus",
+		Choices: []dto.ChatCompletionsStreamResponseChoice{{
+			Delta:        dto.ChatCompletionsStreamResponseChoiceDelta{Content: common.GetPointer("")},
+			FinishReason: &finishReason,
+		}},
+	}, info)
+
+	require.Len(t, responses, 3)
+	require.Equal(t, "content_block_stop", responses[0].Type)
+	require.Equal(t, 1, responses[0].GetIndex())
+	require.Equal(t, "message_delta", responses[1].Type)
+	require.NotNil(t, responses[1].Usage)
+	require.Equal(t, 10, responses[1].Usage.InputTokens)
+	require.Equal(t, 20, responses[1].Usage.OutputTokens)
+	require.NotNil(t, responses[1].Delta)
+	require.NotNil(t, responses[1].Delta.StopReason)
+	require.Equal(t, "end_turn", *responses[1].Delta.StopReason)
+	require.Equal(t, "message_stop", responses[2].Type)
+	require.True(t, info.ClaudeConvertInfo.Done)
+}