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fix(claude): avoid reusing content_block indexes in Codex SSE #538

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a321be1
fix(claude): avoid reusing content_block indexes in codex SSE
fuguiKz Dec 14, 2025
7761566
refactor(claude): dedupe tool_use block key lookup
fuguiKz Dec 14, 2025
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198 changes: 178 additions & 20 deletions internal/translator/codex/claude/codex_claude_response.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ import (
"context"
"encoding/json"
"fmt"
"sort"
"strings"

"github.com/tidwall/gjson"
Expand All @@ -21,6 +22,45 @@ var (
dataTag = []byte("data:")
)

type ConvertCodexResponseToClaudeParams struct {
HasToolCall bool
NextContentBlockIndex int

BlockIndexByKey map[string]int
StartedKeys map[string]bool
StoppedKeys map[string]bool
ToolKeyByOutputIndex map[int64]string
}

func (p *ConvertCodexResponseToClaudeParams) indexForKey(key string) int {
if idx, ok := p.BlockIndexByKey[key]; ok {
return idx
}
idx := p.NextContentBlockIndex
p.NextContentBlockIndex++
p.BlockIndexByKey[key] = idx
return idx
}

func codexClaudeThinkingKey(root gjson.Result) string {
outputIndex := root.Get("output_index").Int()
if summaryIndex := root.Get("summary_index"); summaryIndex.Exists() {
return fmt.Sprintf("thinking:%d:%d", outputIndex, summaryIndex.Int())
}
if contentIndex := root.Get("content_index"); contentIndex.Exists() {
return fmt.Sprintf("thinking:%d:%d", outputIndex, contentIndex.Int())
}
return fmt.Sprintf("thinking:%d", outputIndex)
}

func codexClaudeTextKey(root gjson.Result) string {
outputIndex := root.Get("output_index").Int()
if contentIndex := root.Get("content_index"); contentIndex.Exists() {
return fmt.Sprintf("text:%d:%d", outputIndex, contentIndex.Int())
}
return fmt.Sprintf("text:%d", outputIndex)
}

// ConvertCodexResponseToClaude performs sophisticated streaming response format conversion.
// This function implements a complex state machine that translates Codex API responses
// into Claude Code-compatible Server-Sent Events (SSE) format. It manages different response types
Expand All @@ -39,9 +79,16 @@ var (
// - []string: A slice of strings, each containing a Claude Code-compatible JSON response
func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRawJSON, requestRawJSON, rawJSON []byte, param *any) []string {
if *param == nil {
hasToolCall := false
*param = &hasToolCall
*param = &ConvertCodexResponseToClaudeParams{
HasToolCall: false,
NextContentBlockIndex: 0,
BlockIndexByKey: make(map[string]int),
StartedKeys: make(map[string]bool),
StoppedKeys: make(map[string]bool),
ToolKeyByOutputIndex: make(map[int64]string),
}
}
p := (*param).(*ConvertCodexResponseToClaudeParams)

// log.Debugf("rawJSON: %s", string(rawJSON))
if !bytes.HasPrefix(rawJSON, dataTag) {
Expand All @@ -62,55 +109,131 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa
output = "event: message_start\n"
output += fmt.Sprintf("data: %s\n\n", template)
} else if typeStr == "response.reasoning_summary_part.added" {
blockKey := codexClaudeThinkingKey(rootResult)
index := p.indexForKey(blockKey)

template = `{"type":"content_block_start","index":0,"content_block":{"type":"thinking","thinking":""}}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)

output = "event: content_block_start\n"
output += fmt.Sprintf("data: %s\n\n", template)
p.StartedKeys[blockKey] = true
delete(p.StoppedKeys, blockKey)
} else if typeStr == "response.reasoning_summary_text.delta" {
blockKey := codexClaudeThinkingKey(rootResult)
index := p.indexForKey(blockKey)

if !p.StartedKeys[blockKey] {
startTemplate := `{"type":"content_block_start","index":0,"content_block":{"type":"thinking","thinking":""}}`
startTemplate, _ = sjson.Set(startTemplate, "index", index)

output += "event: content_block_start\n"
output += fmt.Sprintf("data: %s\n\n", startTemplate)
p.StartedKeys[blockKey] = true
delete(p.StoppedKeys, blockKey)
}

template = `{"type":"content_block_delta","index":0,"delta":{"type":"thinking_delta","thinking":""}}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)
template, _ = sjson.Set(template, "delta.thinking", rootResult.Get("delta").String())

output = "event: content_block_delta\n"
output += "event: content_block_delta\n"
output += fmt.Sprintf("data: %s\n\n", template)
} else if typeStr == "response.reasoning_summary_part.done" {
blockKey := codexClaudeThinkingKey(rootResult)
index := p.indexForKey(blockKey)

if !p.StartedKeys[blockKey] || p.StoppedKeys[blockKey] {
return []string{}
}

template = `{"type":"content_block_stop","index":0}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)

output = "event: content_block_stop\n"
output += fmt.Sprintf("data: %s\n\n", template)
p.StoppedKeys[blockKey] = true
} else if typeStr == "response.content_part.added" {
blockKey := codexClaudeTextKey(rootResult)
index := p.indexForKey(blockKey)

template = `{"type":"content_block_start","index":0,"content_block":{"type":"text","text":""}}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)

output = "event: content_block_start\n"
output += fmt.Sprintf("data: %s\n\n", template)
p.StartedKeys[blockKey] = true
delete(p.StoppedKeys, blockKey)
} else if typeStr == "response.output_text.delta" {
blockKey := codexClaudeTextKey(rootResult)
index := p.indexForKey(blockKey)

if !p.StartedKeys[blockKey] {
startTemplate := `{"type":"content_block_start","index":0,"content_block":{"type":"text","text":""}}`
startTemplate, _ = sjson.Set(startTemplate, "index", index)

output += "event: content_block_start\n"
output += fmt.Sprintf("data: %s\n\n", startTemplate)
p.StartedKeys[blockKey] = true
delete(p.StoppedKeys, blockKey)
}

template = `{"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":""}}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)
template, _ = sjson.Set(template, "delta.text", rootResult.Get("delta").String())

output = "event: content_block_delta\n"
output += "event: content_block_delta\n"
output += fmt.Sprintf("data: %s\n\n", template)
} else if typeStr == "response.content_part.done" {
blockKey := codexClaudeTextKey(rootResult)
index := p.indexForKey(blockKey)

if !p.StartedKeys[blockKey] || p.StoppedKeys[blockKey] {
return []string{}
}

template = `{"type":"content_block_stop","index":0}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)

output = "event: content_block_stop\n"
output += fmt.Sprintf("data: %s\n\n", template)
p.StoppedKeys[blockKey] = true
} else if typeStr == "response.completed" {
var openBlocks []struct {
Index int
Key string
}
for key := range p.StartedKeys {
if p.StartedKeys[key] && !p.StoppedKeys[key] {
openBlocks = append(openBlocks, struct {
Index int
Key string
}{
Index: p.indexForKey(key),
Key: key,
})
}
}
sort.Slice(openBlocks, func(i, j int) bool { return openBlocks[i].Index < openBlocks[j].Index })
for _, blk := range openBlocks {
stopTemplate := `{"type":"content_block_stop","index":0}`
stopTemplate, _ = sjson.Set(stopTemplate, "index", blk.Index)

output += "event: content_block_stop\n"
output += fmt.Sprintf("data: %s\n\n", stopTemplate)
p.StoppedKeys[blk.Key] = true
}

template = `{"type":"message_delta","delta":{"stop_reason":"tool_use","stop_sequence":null},"usage":{"input_tokens":0,"output_tokens":0}}`
p := (*param).(*bool)
if *p {
if p.HasToolCall {
template, _ = sjson.Set(template, "delta.stop_reason", "tool_use")
} else {
template, _ = sjson.Set(template, "delta.stop_reason", "end_turn")
}
template, _ = sjson.Set(template, "usage.input_tokens", rootResult.Get("response.usage.input_tokens").Int())
template, _ = sjson.Set(template, "usage.output_tokens", rootResult.Get("response.usage.output_tokens").Int())

output = "event: message_delta\n"
output += "event: message_delta\n"
output += fmt.Sprintf("data: %s\n\n", template)
output += "event: message_stop\n"
output += `data: {"type":"message_stop"}`
Expand All @@ -119,10 +242,16 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa
itemResult := rootResult.Get("item")
itemType := itemResult.Get("type").String()
if itemType == "function_call" {
p := true
*param = &p
p.HasToolCall = true

outputIndex := rootResult.Get("output_index").Int()
callID := itemResult.Get("call_id").String()
blockKey := fmt.Sprintf("tool_use:%d:%s", outputIndex, callID)
p.ToolKeyByOutputIndex[outputIndex] = blockKey
index := p.indexForKey(blockKey)

template = `{"type":"content_block_start","index":0,"content_block":{"type":"tool_use","id":"","name":"","input":{}}}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)
template, _ = sjson.Set(template, "content_block.id", itemResult.Get("call_id").String())
{
// Restore original tool name if shortened
Expand All @@ -136,9 +265,11 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa

output = "event: content_block_start\n"
output += fmt.Sprintf("data: %s\n\n", template)
p.StartedKeys[blockKey] = true
delete(p.StoppedKeys, blockKey)

template = `{"type":"content_block_delta","index":0,"delta":{"type":"input_json_delta","partial_json":""}}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)

output += "event: content_block_delta\n"
output += fmt.Sprintf("data: %s\n\n", template)
Expand All @@ -147,21 +278,48 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa
itemResult := rootResult.Get("item")
itemType := itemResult.Get("type").String()
if itemType == "function_call" {
outputIndex := rootResult.Get("output_index").Int()
blockKey := p.ToolKeyByOutputIndex[outputIndex]
if blockKey == "" {
blockKey = fmt.Sprintf("tool_use:%d", outputIndex)
}
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@gemini-code-assist gemini-code-assist bot Dec 14, 2025

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medium

The logic to get a blockKey for a tool call, with a fallback for when an added event hasn't been seen, is duplicated in the handler for response.function_call_arguments.delta at lines 300-305.

This duplication can make maintenance harder. Additionally, the current implementation is inconsistent: the delta handler saves the fallback key to p.ToolKeyByOutputIndex, but this done handler does not. This could lead to subtle bugs if event ordering is unexpected.

For consistency, this handler should also save the fallback key. For example:

if blockKey == "" {
    blockKey = fmt.Sprintf("tool_use:%d", outputIndex)
    p.ToolKeyByOutputIndex[outputIndex] = blockKey // Add this line
}

Furthermore, to improve maintainability and avoid code duplication, I recommend extracting this logic into a helper method on ConvertCodexResponseToClaudeParams and using it in both places.

index := p.indexForKey(blockKey)

if !p.StartedKeys[blockKey] || p.StoppedKeys[blockKey] {
return []string{}
}

template = `{"type":"content_block_stop","index":0}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)

output = "event: content_block_stop\n"
output += fmt.Sprintf("data: %s\n\n", template)
p.StoppedKeys[blockKey] = true
}
} else if typeStr == "response.function_call_arguments.delta" {
outputIndex := rootResult.Get("output_index").Int()
blockKey := p.ToolKeyByOutputIndex[outputIndex]
if blockKey == "" {
blockKey = fmt.Sprintf("tool_use:%d", outputIndex)
p.ToolKeyByOutputIndex[outputIndex] = blockKey
}
index := p.indexForKey(blockKey)

if !p.StartedKeys[blockKey] || p.StoppedKeys[blockKey] {
return []string{}
}

template = `{"type":"content_block_delta","index":0,"delta":{"type":"input_json_delta","partial_json":""}}`
template, _ = sjson.Set(template, "index", rootResult.Get("output_index").Int())
template, _ = sjson.Set(template, "index", index)
template, _ = sjson.Set(template, "delta.partial_json", rootResult.Get("delta").String())

output += "event: content_block_delta\n"
output = "event: content_block_delta\n"
output += fmt.Sprintf("data: %s\n\n", template)
}

if output == "" {
return []string{}
}
return []string{output}
}

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