fix(translator): add unit tests to validate output_item.done fallback logic for Gemini and Claude

internal/translator/codex/claude/codex_claude_response.go

@@ -26,6 +26,8 @@ type ConvertCodexResponseToClaudeParams struct {
 	HasToolCall               bool
 	BlockIndex                int
 	HasReceivedArgumentsDelta bool
+	HasTextDelta              bool
+	TextBlockOpen             bool
 	ThinkingBlockOpen         bool
 	ThinkingStopPending       bool
 	ThinkingSignature         string
@@ -104,9 +106,11 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa
 	} else if typeStr == "response.content_part.added" {
 		template = []byte(`{"type":"content_block_start","index":0,"content_block":{"type":"text","text":""}}`)
 		template, _ = sjson.SetBytes(template, "index", params.BlockIndex)
+		params.TextBlockOpen = true
 
 		output = translatorcommon.AppendSSEEventBytes(output, "content_block_start", template, 2)
 	} else if typeStr == "response.output_text.delta" {
+		params.HasTextDelta = true
 		template = []byte(`{"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":""}}`)
 		template, _ = sjson.SetBytes(template, "index", params.BlockIndex)
 		template, _ = sjson.SetBytes(template, "delta.text", rootResult.Get("delta").String())
@@ -115,6 +119,7 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa
 	} else if typeStr == "response.content_part.done" {
 		template = []byte(`{"type":"content_block_stop","index":0}`)
 		template, _ = sjson.SetBytes(template, "index", params.BlockIndex)
+		params.TextBlockOpen = false
 		params.BlockIndex++
 
 		output = translatorcommon.AppendSSEEventBytes(output, "content_block_stop", template, 2)
@@ -172,7 +177,49 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa
 	} else if typeStr == "response.output_item.done" {
 		itemResult := rootResult.Get("item")
 		itemType := itemResult.Get("type").String()
-		if itemType == "function_call" {
+		if itemType == "message" {
+			if params.HasTextDelta {
+				return [][]byte{output}
+			}
+			contentResult := itemResult.Get("content")
+			if !contentResult.Exists() || !contentResult.IsArray() {
+				return [][]byte{output}
+			}
+			var textBuilder strings.Builder
+			contentResult.ForEach(func(_, part gjson.Result) bool {
+				if part.Get("type").String() != "output_text" {
+					return true
+				}
+				if txt := part.Get("text").String(); txt != "" {
+					textBuilder.WriteString(txt)
+				}
+				return true
+			})
+			text := textBuilder.String()
+			if text == "" {
+				return [][]byte{output}
+			}
+
+			output = append(output, finalizeCodexThinkingBlock(params)...)
+			if !params.TextBlockOpen {
+				template = []byte(`{"type":"content_block_start","index":0,"content_block":{"type":"text","text":""}}`)
+				template, _ = sjson.SetBytes(template, "index", params.BlockIndex)
+				params.TextBlockOpen = true
+				output = translatorcommon.AppendSSEEventBytes(output, "content_block_start", template, 2)
+			}
+
+			template = []byte(`{"type":"content_block_delta","index":0,"delta":{"type":"text_delta","text":""}}`)
+			template, _ = sjson.SetBytes(template, "index", params.BlockIndex)
+			template, _ = sjson.SetBytes(template, "delta.text", text)
+			output = translatorcommon.AppendSSEEventBytes(output, "content_block_delta", template, 2)
+
+			template = []byte(`{"type":"content_block_stop","index":0}`)
+			template, _ = sjson.SetBytes(template, "index", params.BlockIndex)
+			params.TextBlockOpen = false
+			params.BlockIndex++
+			params.HasTextDelta = true
+			output = translatorcommon.AppendSSEEventBytes(output, "content_block_stop", template, 2)
+		} else if itemType == "function_call" {
 			template = []byte(`{"type":"content_block_stop","index":0}`)
 			template, _ = sjson.SetBytes(template, "index", params.BlockIndex)
 			params.BlockIndex++

internal/translator/codex/claude/codex_claude_response_test.go

@@ -280,3 +280,40 @@ func TestConvertCodexResponseToClaudeNonStream_ThinkingIncludesSignature(t *test
 		t.Fatalf("unexpected thinking text: %q", got)
 	}
 }
+
+func TestConvertCodexResponseToClaude_StreamEmptyOutputUsesOutputItemDoneMessageFallback(t *testing.T) {
+	ctx := context.Background()
+	originalRequest := []byte(`{"tools":[]}`)
+	var param any
+
+	chunks := [][]byte{
+		[]byte("data: {\"type\":\"response.created\",\"response\":{\"id\":\"resp_1\",\"model\":\"gpt-5\"}}"),
+		[]byte("data: {\"type\":\"response.output_item.done\",\"item\":{\"type\":\"message\",\"role\":\"assistant\",\"content\":[{\"type\":\"output_text\",\"text\":\"ok\"}]},\"output_index\":0}"),
+		[]byte("data: {\"type\":\"response.completed\",\"response\":{\"usage\":{\"input_tokens\":1,\"output_tokens\":1}}}"),
+	}
+
+	var outputs [][]byte
+	for _, chunk := range chunks {
+		outputs = append(outputs, ConvertCodexResponseToClaude(ctx, "", originalRequest, nil, chunk, &param)...)
+	}
+
+	foundText := false
+	for _, out := range outputs {
+		for _, line := range strings.Split(string(out), "\n") {
+			if !strings.HasPrefix(line, "data: ") {
+				continue
+			}
+			data := gjson.Parse(strings.TrimPrefix(line, "data: "))
+			if data.Get("type").String() == "content_block_delta" && data.Get("delta.type").String() == "text_delta" && data.Get("delta.text").String() == "ok" {
+				foundText = true
+				break
+			}
+		}
+		if foundText {
+			break
+		}
+	}
+	if !foundText {
+		t.Fatalf("expected fallback content from response.output_item.done message; outputs=%q", outputs)
+	}
+}

internal/translator/codex/gemini/codex_gemini_response.go

@@ -20,10 +20,11 @@ var (
 
 // ConvertCodexResponseToGeminiParams holds parameters for response conversion.
 type ConvertCodexResponseToGeminiParams struct {
-	Model             string
-	CreatedAt         int64
-	ResponseID        string
-	LastStorageOutput []byte
+	Model              string
+	CreatedAt          int64
+	ResponseID         string
+	LastStorageOutput  []byte
+	HasOutputTextDelta bool
 }
 
 // ConvertCodexResponseToGemini converts Codex streaming response format to Gemini format.
@@ -42,10 +43,11 @@ type ConvertCodexResponseToGeminiParams struct {
 func ConvertCodexResponseToGemini(_ context.Context, modelName string, originalRequestRawJSON, requestRawJSON, rawJSON []byte, param *any) [][]byte {
 	if *param == nil {
 		*param = &ConvertCodexResponseToGeminiParams{
-			Model:             modelName,
-			CreatedAt:         0,
-			ResponseID:        "",
-			LastStorageOutput: nil,
+			Model:              modelName,
+			CreatedAt:          0,
+			ResponseID:         "",
+			LastStorageOutput:  nil,
+			HasOutputTextDelta: false,
 		}
 	}
 
@@ -58,18 +60,18 @@ func ConvertCodexResponseToGemini(_ context.Context, modelName string, originalR
 	typeResult := rootResult.Get("type")
 	typeStr := typeResult.String()
 
+	params := (*param).(*ConvertCodexResponseToGeminiParams)
+
 	// Base Gemini response template
 	template := []byte(`{"candidates":[{"content":{"role":"model","parts":[]}}],"usageMetadata":{"trafficType":"PROVISIONED_THROUGHPUT"},"modelVersion":"gemini-2.5-pro","createTime":"2025-08-15T02:52:03.884209Z","responseId":"06CeaPH7NaCU48APvNXDyA4"}`)
-	if len((*param).(*ConvertCodexResponseToGeminiParams).LastStorageOutput) > 0 && typeStr == "response.output_item.done" {
-		template = append([]byte(nil), (*param).(*ConvertCodexResponseToGeminiParams).LastStorageOutput...)
-	} else {
-		template, _ = sjson.SetBytes(template, "modelVersion", (*param).(*ConvertCodexResponseToGeminiParams).Model)
+	{
+		template, _ = sjson.SetBytes(template, "modelVersion", params.Model)
 		createdAtResult := rootResult.Get("response.created_at")
 		if createdAtResult.Exists() {
-			(*param).(*ConvertCodexResponseToGeminiParams).CreatedAt = createdAtResult.Int()
-			template, _ = sjson.SetBytes(template, "createTime", time.Unix((*param).(*ConvertCodexResponseToGeminiParams).CreatedAt, 0).Format(time.RFC3339Nano))
+			params.CreatedAt = createdAtResult.Int()
+			template, _ = sjson.SetBytes(template, "createTime", time.Unix(params.CreatedAt, 0).Format(time.RFC3339Nano))
 		}
-		template, _ = sjson.SetBytes(template, "responseId", (*param).(*ConvertCodexResponseToGeminiParams).ResponseID)
+		template, _ = sjson.SetBytes(template, "responseId", params.ResponseID)
 	}
 
 	// Handle function call completion
@@ -101,7 +103,7 @@ func ConvertCodexResponseToGemini(_ context.Context, modelName string, originalR
 			template, _ = sjson.SetRawBytes(template, "candidates.0.content.parts.-1", functionCall)
 			template, _ = sjson.SetBytes(template, "candidates.0.finishReason", "STOP")
 
-			(*param).(*ConvertCodexResponseToGeminiParams).LastStorageOutput = append([]byte(nil), template...)
+			params.LastStorageOutput = append([]byte(nil), template...)
 
 			// Use this return to storage message
 			return [][]byte{}
@@ -111,15 +113,45 @@ func ConvertCodexResponseToGemini(_ context.Context, modelName string, originalR
 	if typeStr == "response.created" { // Handle response creation - set model and response ID
 		template, _ = sjson.SetBytes(template, "modelVersion", rootResult.Get("response.model").String())
 		template, _ = sjson.SetBytes(template, "responseId", rootResult.Get("response.id").String())
-		(*param).(*ConvertCodexResponseToGeminiParams).ResponseID = rootResult.Get("response.id").String()
+		params.ResponseID = rootResult.Get("response.id").String()
 	} else if typeStr == "response.reasoning_summary_text.delta" { // Handle reasoning/thinking content delta
 		part := []byte(`{"thought":true,"text":""}`)
 		part, _ = sjson.SetBytes(part, "text", rootResult.Get("delta").String())
 		template, _ = sjson.SetRawBytes(template, "candidates.0.content.parts.-1", part)
 	} else if typeStr == "response.output_text.delta" { // Handle regular text content delta
+		params.HasOutputTextDelta = true
 		part := []byte(`{"text":""}`)
 		part, _ = sjson.SetBytes(part, "text", rootResult.Get("delta").String())
 		template, _ = sjson.SetRawBytes(template, "candidates.0.content.parts.-1", part)
+	} else if typeStr == "response.output_item.done" { // Fallback: emit final message text when no delta chunks were received
+		itemResult := rootResult.Get("item")
+		if itemResult.Get("type").String() != "message" || params.HasOutputTextDelta {
+			return [][]byte{}
+		}
+		contentResult := itemResult.Get("content")
+		if !contentResult.Exists() || !contentResult.IsArray() {
+			return [][]byte{}
+		}
+		wroteText := false
+		contentResult.ForEach(func(_, partResult gjson.Result) bool {
+			if partResult.Get("type").String() != "output_text" {
+				return true
+			}
+			text := partResult.Get("text").String()
+			if text == "" {
+				return true
+			}
+			part := []byte(`{"text":""}`)
+			part, _ = sjson.SetBytes(part, "text", text)
+			template, _ = sjson.SetRawBytes(template, "candidates.0.content.parts.-1", part)
+			wroteText = true
+			return true
+		})
+		if wroteText {
+			params.HasOutputTextDelta = true
+			return [][]byte{template}
+		}
+		return [][]byte{}
 	} else if typeStr == "response.completed" { // Handle response completion with usage metadata
 		template, _ = sjson.SetBytes(template, "usageMetadata.promptTokenCount", rootResult.Get("response.usage.input_tokens").Int())
 		template, _ = sjson.SetBytes(template, "usageMetadata.candidatesTokenCount", rootResult.Get("response.usage.output_tokens").Int())
@@ -129,11 +161,10 @@ func ConvertCodexResponseToGemini(_ context.Context, modelName string, originalR
 		return [][]byte{}
 	}
 
-	if len((*param).(*ConvertCodexResponseToGeminiParams).LastStorageOutput) > 0 {
-		return [][]byte{
-			append([]byte(nil), (*param).(*ConvertCodexResponseToGeminiParams).LastStorageOutput...),
-			template,
-		}
+	if len(params.LastStorageOutput) > 0 {
+		stored := append([]byte(nil), params.LastStorageOutput...)
+		params.LastStorageOutput = nil
+		return [][]byte{stored, template}
 	}
 	return [][]byte{template}
 }

internal/translator/codex/gemini/codex_gemini_response_test.go

@@ -0,0 +1,35 @@
+package gemini
+
+import (
+	"context"
+	"testing"
+
+	"github.com/tidwall/gjson"
+)
+
+func TestConvertCodexResponseToGemini_StreamEmptyOutputUsesOutputItemDoneMessageFallback(t *testing.T) {
+	ctx := context.Background()
+	originalRequest := []byte(`{"tools":[]}`)
+	var param any
+
+	chunks := [][]byte{
+		[]byte("data: {\"type\":\"response.output_item.done\",\"item\":{\"type\":\"message\",\"role\":\"assistant\",\"content\":[{\"type\":\"output_text\",\"text\":\"ok\"}]},\"output_index\":0}"),
+		[]byte("data: {\"type\":\"response.completed\",\"response\":{\"usage\":{\"input_tokens\":1,\"output_tokens\":1}}}"),
+	}
+
+	var outputs [][]byte
+	for _, chunk := range chunks {
+		outputs = append(outputs, ConvertCodexResponseToGemini(ctx, "gemini-2.5-pro", originalRequest, nil, chunk, &param)...)
+	}
+
+	found := false
+	for _, out := range outputs {
+		if gjson.GetBytes(out, "candidates.0.content.parts.0.text").String() == "ok" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatalf("expected fallback content from response.output_item.done message; outputs=%q", outputs)
+	}
+}