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fix(claude): preserve parallel tool call stream indexes #4730

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fix(claude): preserve parallel tool call stream indexes #4730

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58 changes: 43 additions & 15 deletions relay/channel/claude/relay-claude.go
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Original file line number Diff line number Diff line change
Expand Up @@ -435,17 +435,20 @@ func RequestOpenAI2ClaudeMessage(c *gin.Context, textRequest dto.GeneralOpenAIRe
}

func StreamResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse) *dto.ChatCompletionsStreamResponse {
return streamResponseClaude2OpenAI(claudeResponse, nil)
}

func streamResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse, claudeInfo *ClaudeResponseInfo) *dto.ChatCompletionsStreamResponse {
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
if claudeResponse.Index != nil {
fcIdx = *claudeResponse.Index - 1
if fcIdx < 0 {
fcIdx = 0
toolCallIdx := func() int {
if claudeResponse.Index == nil {
return 0
}
return claudeInfo.getOpenAIToolCallIndex(*claudeResponse.Index)
}
var choice dto.ChatCompletionsStreamResponseChoice
if claudeResponse.Type == "message_start" {
Expand All @@ -464,7 +467,7 @@ 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(toolCallIdx()),
ID: claudeResponse.ContentBlock.Id,
Type: "function",
Function: dto.FunctionResponse{
Expand All @@ -481,11 +484,15 @@ func StreamResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse) *dto.ChatCo
choice.Delta.Content = claudeResponse.Delta.Text
switch claudeResponse.Delta.Type {
case "input_json_delta":
arguments := ""
if claudeResponse.Delta.PartialJson != nil {
arguments = *claudeResponse.Delta.PartialJson
}
tools = append(tools, dto.ToolCallResponse{
Type: "function",
Index: common.GetPointer(fcIdx),
Index: common.GetPointer(toolCallIdx()),
Function: dto.FunctionResponse{
Arguments: *claudeResponse.Delta.PartialJson,
Arguments: arguments,
},
})
case "signature_delta":
Expand Down Expand Up @@ -518,6 +525,25 @@ func StreamResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse) *dto.ChatCo
return &response
}

func (c *ClaudeResponseInfo) getOpenAIToolCallIndex(contentBlockIndex int) int {
if c == nil {
if contentBlockIndex <= 0 {
return 0
}
return contentBlockIndex - 1
}
Comment on lines +528 to +534

@coderabbitai coderabbitai Bot May 10, 2026

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⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Nil-state fallback still allows tool-call index collisions.

When claudeInfo is nil, Line 533 returns contentBlockIndex - 1; parallel tool blocks at indexes 0 and 1 both map to index 0. Since Line 438 uses this path in the exported wrapper, direct callers can still merge distinct tool arguments incorrectly.

Suggested fix 
 func (c *ClaudeResponseInfo) getOpenAIToolCallIndex(contentBlockIndex int) int {
 	if c == nil {
-		if contentBlockIndex <= 0 {
+		if contentBlockIndex < 0 {
 			return 0
 		}
-		return contentBlockIndex - 1
+		// Stateless fallback: keep indices unique to avoid collisions.
+		return contentBlockIndex
 	}
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
func (c *ClaudeResponseInfo) getOpenAIToolCallIndex(contentBlockIndex int) int {
if c == nil {
if contentBlockIndex <= 0 {
return 0
}
return contentBlockIndex - 1
}
func (c *ClaudeResponseInfo) getOpenAIToolCallIndex(contentBlockIndex int) int {
if c == nil {
if contentBlockIndex < 0 {
return 0
}
// Stateless fallback: keep indices unique to avoid collisions.
return contentBlockIndex
}
🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@relay/channel/claude/relay-claude.go` around lines 528 - 534, The nil-state
fallback in ClaudeResponseInfo.getOpenAIToolCallIndex currently maps multiple
contentBlockIndex values (e.g., 0 and 1) to the same tool index by returning
contentBlockIndex-1; change the fallback so it preserves uniqueness: when c ==
nil, return contentBlockIndex (with a guard to clamp negative values to 0)
instead of contentBlockIndex-1 so distinct parallel tool blocks map to distinct
indices. Ensure the updated logic handles contentBlockIndex < 0 by returning 0.

if c.toolCallIndexByContentBlock == nil {
c.toolCallIndexByContentBlock = make(map[int]int)
}
if index, ok := c.toolCallIndexByContentBlock[contentBlockIndex]; ok {
return index
}
index := c.nextToolCallIndex
c.toolCallIndexByContentBlock[contentBlockIndex] = index
c.nextToolCallIndex++
return index
}

func ResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse) *dto.OpenAITextResponse {
choices := make([]dto.OpenAITextResponseChoice, 0)
fullTextResponse := dto.OpenAITextResponse{
Expand Down Expand Up @@ -582,12 +608,14 @@ func ResponseClaude2OpenAI(claudeResponse *dto.ClaudeResponse) *dto.OpenAITextRe
}

type ClaudeResponseInfo struct {
ResponseId string
Created int64
Model string
ResponseText strings.Builder
Usage *dto.Usage
Done bool
ResponseId string
Created int64
Model string
ResponseText strings.Builder
Usage *dto.Usage
Done bool
toolCallIndexByContentBlock map[int]int
nextToolCallIndex int
}

func cacheCreationTokensForOpenAIUsage(usage *dto.Usage) int {
Expand Down Expand Up @@ -816,7 +844,7 @@ 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
Expand Down
49 changes: 49 additions & 0 deletions relay/channel/claude/relay_claude_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -176,6 +176,55 @@ func TestFormatClaudeResponseInfo_ContentBlockDelta(t *testing.T) {
}
}

func TestStreamResponseClaude2OpenAIMapsParallelToolUseIndexes(t *testing.T) {
claudeInfo := &ClaudeResponseInfo{}

firstStart := streamResponseClaude2OpenAI(&dto.ClaudeResponse{
Type: "content_block_start",
Index: intPtr(0),
ContentBlock: &dto.ClaudeMediaMessage{Type: "tool_use", Id: "toolu_1", Name: "read_file"},
}, claudeInfo)
requireToolCallIndex(t, firstStart, 0)

firstDelta := streamResponseClaude2OpenAI(&dto.ClaudeResponse{
Type: "content_block_delta",
Index: intPtr(0),
Delta: &dto.ClaudeMediaMessage{Type: "input_json_delta", PartialJson: stringPtr(`{"file_path":"/a"}`)},
}, claudeInfo)
requireToolCallIndex(t, firstDelta, 0)

secondStart := streamResponseClaude2OpenAI(&dto.ClaudeResponse{
Type: "content_block_start",
Index: intPtr(1),
ContentBlock: &dto.ClaudeMediaMessage{Type: "tool_use", Id: "toolu_2", Name: "read_file"},
}, claudeInfo)
requireToolCallIndex(t, secondStart, 1)

secondDelta := streamResponseClaude2OpenAI(&dto.ClaudeResponse{
Type: "content_block_delta",
Index: intPtr(1),
Delta: &dto.ClaudeMediaMessage{Type: "input_json_delta", PartialJson: stringPtr(`{"file_path":"/b"}`)},
}, claudeInfo)
requireToolCallIndex(t, secondDelta, 1)
}

func requireToolCallIndex(t *testing.T, response *dto.ChatCompletionsStreamResponse, expected int) {
t.Helper()
require.NotNil(t, response)
require.Len(t, response.Choices, 1)
require.Len(t, response.Choices[0].Delta.ToolCalls, 1)
require.NotNil(t, response.Choices[0].Delta.ToolCalls[0].Index)
require.Equal(t, expected, *response.Choices[0].Delta.ToolCalls[0].Index)
}

func intPtr(v int) *int {
return &v
}

func stringPtr(v string) *string {
return &v
}

func TestBuildOpenAIStyleUsageFromClaudeUsage(t *testing.T) {
usage := &dto.Usage{
PromptTokens: 100,
Expand Down