diff --git a/relay/channel/claude/relay-claude.go b/relay/channel/claude/relay-claude.go
index 18d7455e9f22..aad8c2706b97 100644
--- a/relay/channel/claude/relay-claude.go
+++ b/relay/channel/claude/relay-claude.go
@@ -438,15 +438,18 @@ func RequestOpenAI2ClaudeMessage(c *gin.Context, textRequest dto.GeneralOpenAIRe
 	return &claudeRequest, nil
 }
 
-func StreamResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse) *dto.ChatCompletionsStreamResponse {
+func StreamResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse, claudeInfo *ClaudeResponseInfo) *dto.ChatCompletionsStreamResponse {
+	if claudeInfo == nil {
+		claudeInfo = &ClaudeResponseInfo{}
+	}
 	var response dto.ChatCompletionsStreamResponse
 	response.Object = "chat.completion.chunk"
 	response.Model = claudeResponse.Model
 	response.Choices = make([]dto.ChatCompletionsStreamResponseChoice, 0)
 	tools := make([]dto.ToolCallResponse, 0)
-	fcIdx := 0
+	blockIdx := 0
 	if claudeResponse.Index != nil {
-		fcIdx = *claudeResponse.Index
+		blockIdx = *claudeResponse.Index
 	}
 	var choice dto.ChatCompletionsStreamResponseChoice
 	if claudeResponse.Type == "message_start" {
@@ -465,7 +468,7 @@ func StreamResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse) *dto.ChatCo
 			}
 			if claudeResponse.ContentBlock.Type == "tool_use" {
 				tools = append(tools, dto.ToolCallResponse{
-					Index: common.GetPointer(fcIdx),
+					Index: common.GetPointer(claudeInfo.toolCallIndex(blockIdx)),
 					ID:    claudeResponse.ContentBlock.Id,
 					Type:  "function",
 					Function: dto.FunctionResponse{
@@ -484,7 +487,7 @@ func StreamResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse) *dto.ChatCo
 			case "input_json_delta":
 				tools = append(tools, dto.ToolCallResponse{
 					Type:  "function",
-					Index: common.GetPointer(fcIdx),
+					Index: common.GetPointer(claudeInfo.toolCallIndex(blockIdx)),
 					Function: dto.FunctionResponse{
 						Arguments: *claudeResponse.Delta.PartialJson,
 					},
@@ -589,6 +592,23 @@ type ClaudeResponseInfo struct {
 	ResponseText strings.Builder
 	Usage        *dto.Usage
 	Done         bool
+	ToolIndexMap map[int]int
+}
+
+// toolCallIndex maps a Claude content-block index to a 0-based OpenAI tool_call
+// ordinal (Claude counts all blocks; OpenAI counts only tool calls). Call it
+// only for tool_use blocks — for text/thinking blocks it would consume an
+// ordinal and shift later tool indices.
+func (info *ClaudeResponseInfo) toolCallIndex(blockIndex int) int {
+	if info.ToolIndexMap == nil {
+		info.ToolIndexMap = make(map[int]int)
+	}
+	if idx, ok := info.ToolIndexMap[blockIndex]; ok {
+		return idx
+	}
+	idx := len(info.ToolIndexMap)
+	info.ToolIndexMap[blockIndex] = idx
+	return idx
 }
 
 func cacheCreationTokensForOpenAIUsage(usage *dto.Usage) int {
@@ -817,7 +837,7 @@ func HandleStreamResponseData(c *gin.Context, info *relaycommon.RelayInfo, claud
 		}
 		helper.ClaudeChunkData(c, claudeResponse, data)
 	} else if info.RelayFormat == types.RelayFormatOpenAI {
-		response := StreamResponseClaude2OpenAI(&claudeResponse)
+		response := StreamResponseClaude2OpenAI(&claudeResponse, claudeInfo)
 
 		if !FormatClaudeResponseInfo(&claudeResponse, response, claudeInfo) {
 			return nil
diff --git a/relay/channel/claude/relay_claude_test.go b/relay/channel/claude/relay_claude_test.go
index 495c500bbd13..34a90b6b26ce 100644
--- a/relay/channel/claude/relay_claude_test.go
+++ b/relay/channel/claude/relay_claude_test.go
@@ -13,6 +13,78 @@ func commonPointer[T any](value T) *T {
 	return &value
 }
 
+func mkToolUseStart(i int, id string) *dto.ClaudeResponse {
+	idx := i
+	return &dto.ClaudeResponse{
+		Type:         "content_block_start",
+		Index:        &idx,
+		ContentBlock: &dto.ClaudeMediaMessage{Type: "tool_use", Id: id, Name: "f"},
+	}
+}
+
+// claude-opus-4-8 回归：前导 text 块不得把后续 tool_use 的工具序号顶离 0。
+func TestStreamToolCallIndex_LeadingTextDoesNotShiftToolIndex(t *testing.T) {
+	info := &ClaudeResponseInfo{Usage: &dto.Usage{}}
+
+	text := "好的，我来安排执行。"
+	textIdx := 0
+	resp := StreamResponseClaude2OpenAI(&dto.ClaudeResponse{
+		Type:         "content_block_start",
+		Index:        &textIdx,
+		ContentBlock: &dto.ClaudeMediaMessage{Type: "text", Text: &text},
+	}, info)
+	require.Len(t, resp.Choices[0].Delta.ToolCalls, 0)
+	require.Empty(t, info.ToolIndexMap, "前导文本块不应分配工具序号")
+
+	blk := 1
+	resp = StreamResponseClaude2OpenAI(&dto.ClaudeResponse{
+		Type:         "content_block_start",
+		Index:        &blk,
+		ContentBlock: &dto.ClaudeMediaMessage{Type: "tool_use", Id: "toolu_1", Name: "execute_task"},
+	}, info)
+	require.Len(t, resp.Choices[0].Delta.ToolCalls, 1)
+	require.NotNil(t, resp.Choices[0].Delta.ToolCalls[0].Index)
+	require.Equal(t, 0, *resp.Choices[0].Delta.ToolCalls[0].Index)
+	require.Equal(t, "toolu_1", resp.Choices[0].Delta.ToolCalls[0].ID)
+
+	pj := `{"intent":"x"}` // input_json_delta 复用 start 分配的序号
+	resp = StreamResponseClaude2OpenAI(&dto.ClaudeResponse{
+		Type:  "content_block_delta",
+		Index: &blk,
+		Delta: &dto.ClaudeMediaMessage{Type: "input_json_delta", PartialJson: &pj},
+	}, info)
+	require.Len(t, resp.Choices[0].Delta.ToolCalls, 1)
+	require.Equal(t, 0, *resp.Choices[0].Delta.ToolCalls[0].Index)
+	require.Equal(t, pj, resp.Choices[0].Delta.ToolCalls[0].Function.Arguments)
+}
+
+// 前导 thinking 块同样不应占用工具序号；其后两个工具应得到连续的 0、1。
+func TestStreamToolCallIndex_LeadingThinkingThenTools(t *testing.T) {
+	info := &ClaudeResponseInfo{Usage: &dto.Usage{}}
+
+	think := "let me think"
+	thIdx := 0
+	StreamResponseClaude2OpenAI(&dto.ClaudeResponse{
+		Type:  "content_block_delta",
+		Index: &thIdx,
+		Delta: &dto.ClaudeMediaMessage{Type: "thinking_delta", Thinking: &think},
+	}, info)
+
+	r1 := StreamResponseClaude2OpenAI(mkToolUseStart(1, "a"), info)
+	r2 := StreamResponseClaude2OpenAI(mkToolUseStart(2, "b"), info)
+	require.Equal(t, 0, *r1.Choices[0].Delta.ToolCalls[0].Index)
+	require.Equal(t, 1, *r2.Choices[0].Delta.ToolCalls[0].Index)
+}
+
+// 无前导块、多工具从块 0 起：序号 0、1 不撞键(对应 ff06067a1)。
+func TestStreamToolCallIndex_MultipleToolsFromZeroNoCollision(t *testing.T) {
+	info := &ClaudeResponseInfo{Usage: &dto.Usage{}}
+	r0 := StreamResponseClaude2OpenAI(mkToolUseStart(0, "a"), info)
+	r1 := StreamResponseClaude2OpenAI(mkToolUseStart(1, "b"), info)
+	require.Equal(t, 0, *r0.Choices[0].Delta.ToolCalls[0].Index)
+	require.Equal(t, 1, *r1.Choices[0].Delta.ToolCalls[0].Index)
+}
+
 func TestFormatClaudeResponseInfo_MessageStart(t *testing.T) {
 	claudeInfo := &ClaudeResponseInfo{
 		Usage: &dto.Usage{},