fix: drain OpenAI compat streams for usage

backend/internal/pkg/apicompat/anthropic_responses_test.go

@@ -434,6 +434,45 @@ func TestStreamingTextOnly(t *testing.T) {
 	assert.Equal(t, "message_stop", events[1].Type)
 }
 
+func TestResponsesEventToAnthropicEvents_ResponseDone(t *testing.T) {
+	state := NewResponsesEventToAnthropicState()
+	state.Model = "gpt-4o"
+
+	events := ResponsesEventToAnthropicEvents(&ResponsesStreamEvent{
+		Type: "response.done",
+		Response: &ResponsesResponse{
+			Status: "completed",
+			Usage:  &ResponsesUsage{InputTokens: 12, OutputTokens: 4},
+		},
+	}, state)
+	require.Len(t, events, 2)
+	assert.Equal(t, "message_delta", events[0].Type)
+	assert.Equal(t, "end_turn", events[0].Delta.StopReason)
+	assert.Equal(t, 12, events[0].Usage.InputTokens)
+	assert.Equal(t, 4, events[0].Usage.OutputTokens)
+	assert.Equal(t, "message_stop", events[1].Type)
+	assert.Nil(t, FinalizeResponsesAnthropicStream(state))
+}
+
+func TestResponsesEventToAnthropicEvents_ResponseDoneIncomplete(t *testing.T) {
+	state := NewResponsesEventToAnthropicState()
+	state.Model = "gpt-4o"
+
+	events := ResponsesEventToAnthropicEvents(&ResponsesStreamEvent{
+		Type: "response.done",
+		Response: &ResponsesResponse{
+			Status:            "incomplete",
+			IncompleteDetails: &ResponsesIncompleteDetails{Reason: "max_output_tokens"},
+			Usage:             &ResponsesUsage{InputTokens: 12, OutputTokens: 4},
+		},
+	}, state)
+	require.Len(t, events, 2)
+	assert.Equal(t, "message_delta", events[0].Type)
+	assert.Equal(t, "max_tokens", events[0].Delta.StopReason)
+	assert.Equal(t, "message_stop", events[1].Type)
+	assert.Nil(t, FinalizeResponsesAnthropicStream(state))
+}
+
 func TestStreamingCachedTokensUseAnthropicInputSemantics(t *testing.T) {
 	state := NewResponsesEventToAnthropicState()
 	ResponsesEventToAnthropicEvents(&ResponsesStreamEvent{

backend/internal/pkg/apicompat/chatcompletions_responses_test.go

@@ -720,6 +720,49 @@ func TestResponsesEventToChatChunks_Completed(t *testing.T) {
 	assert.Equal(t, 30, chunks[1].Usage.PromptTokensDetails.CachedTokens)
 }
 
+func TestResponsesEventToChatChunks_ResponseDone(t *testing.T) {
+	state := NewResponsesEventToChatState()
+	state.Model = "gpt-4o"
+	state.IncludeUsage = true
+
+	chunks := ResponsesEventToChatChunks(&ResponsesStreamEvent{
+		Type: "response.done",
+		Response: &ResponsesResponse{
+			Status: "completed",
+			Usage:  &ResponsesUsage{InputTokens: 13, OutputTokens: 7},
+		},
+	}, state)
+	require.Len(t, chunks, 2)
+	require.NotNil(t, chunks[0].Choices[0].FinishReason)
+	assert.Equal(t, "stop", *chunks[0].Choices[0].FinishReason)
+	require.NotNil(t, chunks[1].Usage)
+	assert.Equal(t, 13, chunks[1].Usage.PromptTokens)
+	assert.Equal(t, 7, chunks[1].Usage.CompletionTokens)
+	assert.Nil(t, FinalizeResponsesChatStream(state))
+}
+
+func TestResponsesEventToChatChunks_ResponseDoneIncomplete(t *testing.T) {
+	state := NewResponsesEventToChatState()
+	state.Model = "gpt-4o"
+	state.IncludeUsage = true
+
+	chunks := ResponsesEventToChatChunks(&ResponsesStreamEvent{
+		Type: "response.done",
+		Response: &ResponsesResponse{
+			Status:            "incomplete",
+			IncompleteDetails: &ResponsesIncompleteDetails{Reason: "max_output_tokens"},
+			Usage:             &ResponsesUsage{InputTokens: 13, OutputTokens: 7},
+		},
+	}, state)
+	require.Len(t, chunks, 2)
+	require.NotNil(t, chunks[0].Choices[0].FinishReason)
+	assert.Equal(t, "length", *chunks[0].Choices[0].FinishReason)
+	require.NotNil(t, chunks[1].Usage)
+	assert.Equal(t, 13, chunks[1].Usage.PromptTokens)
+	assert.Equal(t, 7, chunks[1].Usage.CompletionTokens)
+	assert.Nil(t, FinalizeResponsesChatStream(state))
+}
+
 func TestResponsesEventToChatChunks_CompletedWithToolCalls(t *testing.T) {
 	state := NewResponsesEventToChatState()
 	state.Model = "gpt-4o"

backend/internal/pkg/apicompat/responses_to_anthropic.go

@@ -212,7 +212,9 @@ func ResponsesEventToAnthropicEvents(
 		return resToAnthHandleReasoningDelta(evt, state)
 	case "response.reasoning_summary_text.done":
 		return resToAnthHandleBlockDone(state)
-	case "response.completed", "response.incomplete", "response.failed":
+	// response.done 是 Realtime/WS 与项目透传路径使用的终止别名；
+	// 普通 Responses HTTP SSE 的公开终止事件仍以 response.completed 为主。
+	case "response.completed", "response.done", "response.incomplete", "response.failed":
 		return resToAnthHandleCompleted(evt, state)
 	default:
 		return nil

backend/internal/pkg/apicompat/responses_to_chatcompletions.go

@@ -160,7 +160,9 @@ func ResponsesEventToChatChunks(evt *ResponsesStreamEvent, state *ResponsesEvent
 		return resToChatHandleReasoningDelta(evt, state)
 	case "response.reasoning_summary_text.done":
 		return nil
-	case "response.completed", "response.incomplete", "response.failed":
+	// response.done 是 Realtime/WS 与项目透传路径使用的终止别名；
+	// 普通 Responses HTTP SSE 的公开终止事件仍以 response.completed 为主。
+	case "response.completed", "response.done", "response.incomplete", "response.failed":
 		return resToChatHandleCompleted(evt, state)
 	default:
 		return nil

backend/internal/pkg/apicompat/types.go

@@ -314,7 +314,7 @@ type ResponsesOutputTokensDetails struct {
 type ResponsesStreamEvent struct {
 	Type string `json:"type"`
 
-	// response.created / response.completed / response.failed / response.incomplete
+	// response.created / response.completed / response.done / response.failed / response.incomplete
 	Response *ResponsesResponse `json:"response,omitempty"`
 
 	// response.output_item.added / response.output_item.done

backend/internal/service/gateway_service.go

@@ -8174,9 +8174,16 @@ func detachedBillingContext(ctx context.Context) (context.Context, context.Cance
 }
 
 func detachStreamUpstreamContext(ctx context.Context, stream bool) (context.Context, context.CancelFunc) {
+	if ctx == nil {
+		return context.Background(), func() {}
+	}
 	if !stream {
 		return ctx, func() {}
 	}
+	return context.WithoutCancel(ctx), func() {}
+}
+
+func detachUpstreamContext(ctx context.Context) (context.Context, context.CancelFunc) {
 	if ctx == nil {
 		return context.Background(), func() {}
 	}

backend/internal/service/gateway_service_streaming_test.go

@@ -13,6 +13,8 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+type upstreamContextTestKey string
+
 func TestGatewayService_StreamingReusesScannerBufferAndStillParsesUsage(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	cfg := &config.Config{
@@ -50,3 +52,14 @@ func TestGatewayService_StreamingReusesScannerBufferAndStillParsesUsage(t *testi
 	require.Equal(t, 3, result.usage.InputTokens)
 	require.Equal(t, 7, result.usage.OutputTokens)
 }
+
+func TestDetachUpstreamContextIgnoresClientCancel(t *testing.T) {
+	parent, cancel := context.WithCancel(context.WithValue(context.Background(), upstreamContextTestKey("test-key"), "test-value"))
+	upstreamCtx, release := detachUpstreamContext(parent)
+	defer release()
+
+	cancel()
+
+	require.NoError(t, upstreamCtx.Err())
+	require.Equal(t, "test-value", upstreamCtx.Value(upstreamContextTestKey("test-key")))
+}

backend/internal/service/openai_compat_model_test.go

@@ -3,13 +3,16 @@ package service
 import (
 	"bytes"
 	"context"
+	"errors"
 	"io"
 	"net/http"
 	"net/http/httptest"
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"testing"
+	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/apicompat"
@@ -18,6 +21,51 @@ import (
 	"github.com/tidwall/gjson"
 )
 
+type openAICompatFailingWriter struct {
+	gin.ResponseWriter
+	failAfter int
+	writes    int
+}
+
+func (w *openAICompatFailingWriter) Write(p []byte) (int, error) {
+	if w.writes >= w.failAfter {
+		return 0, errors.New("write failed: client disconnected")
+	}
+	w.writes++
+	return w.ResponseWriter.Write(p)
+}
+
+type openAICompatBlockingReadCloser struct {
+	data      []byte
+	offset    int
+	closed    chan struct{}
+	closeOnce sync.Once
+}
+
+func newOpenAICompatBlockingReadCloser(data []byte) *openAICompatBlockingReadCloser {
+	return &openAICompatBlockingReadCloser{
+		data:   data,
+		closed: make(chan struct{}),
+	}
+}
+
+func (r *openAICompatBlockingReadCloser) Read(p []byte) (int, error) {
+	if r.offset < len(r.data) {
+		n := copy(p, r.data[r.offset:])
+		r.offset += n
+		return n, nil
+	}
+	<-r.closed
+	return 0, io.EOF
+}
+
+func (r *openAICompatBlockingReadCloser) Close() error {
+	r.closeOnce.Do(func() {
+		close(r.closed)
+	})
+	return nil
+}
+
 func TestNormalizeOpenAICompatRequestedModel(t *testing.T) {
 	t.Parallel()
 
@@ -228,3 +276,238 @@ func TestForwardAsAnthropic_ForcedCodexInstructionsTemplateUsesCachedTemplateCon
 	require.NotNil(t, result)
 	require.Equal(t, "cached-prefix\n\nclient-system", gjson.GetBytes(upstream.lastBody, "instructions").String())
 }
+
+func TestForwardAsAnthropic_ClientDisconnectDrainsUpstreamUsage(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Writer = &openAICompatFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+	body := []byte(`{"model":"gpt-5.4","max_tokens":16,"messages":[{"role":"user","content":"hello"}],"stream":true}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", bytes.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	upstreamBody := strings.Join([]string{
+		`data: {"type":"response.created","response":{"id":"resp_1","model":"gpt-5.4","status":"in_progress","output":[]}}`,
+		"",
+		`data: {"type":"response.output_text.delta","delta":"ok"}`,
+		"",
+		`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","model":"gpt-5.4","status":"completed","output":[{"type":"message","id":"msg_1","role":"assistant","status":"completed","content":[{"type":"output_text","text":"ok"}]}],"usage":{"input_tokens":9,"output_tokens":4,"total_tokens":13,"input_tokens_details":{"cached_tokens":3}}}}`,
+		"",
+		"data: [DONE]",
+		"",
+	}, "\n")
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_disconnect"}},
+		Body:       io.NopCloser(strings.NewReader(upstreamBody)),
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	result, err := svc.ForwardAsAnthropic(context.Background(), c, account, body, "", "gpt-5.1")
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, 9, result.Usage.InputTokens)
+	require.Equal(t, 4, result.Usage.OutputTokens)
+	require.Equal(t, 3, result.Usage.CacheReadInputTokens)
+}
+
+func TestForwardAsAnthropic_TerminalUsageWithoutUpstreamCloseReturns(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Writer = &openAICompatFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+	body := []byte(`{"model":"gpt-5.4","max_tokens":16,"messages":[{"role":"user","content":"hello"}],"stream":true}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", bytes.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	upstreamBody := []byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","model":"gpt-5.4","status":"completed","output":[{"type":"message","id":"msg_1","role":"assistant","status":"completed","content":[{"type":"output_text","text":"ok"}]}],"usage":{"input_tokens":15,"output_tokens":6,"total_tokens":21,"input_tokens_details":{"cached_tokens":5}}}}` + "\n\n")
+	upstreamStream := newOpenAICompatBlockingReadCloser(upstreamBody)
+	defer upstreamStream.Close()
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_terminal_no_close"}},
+		Body:       upstreamStream,
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	type forwardResult struct {
+		result *OpenAIForwardResult
+		err    error
+	}
+	resultCh := make(chan forwardResult, 1)
+	go func() {
+		result, err := svc.ForwardAsAnthropic(context.Background(), c, account, body, "", "gpt-5.1")
+		resultCh <- forwardResult{result: result, err: err}
+	}()
+
+	select {
+	case got := <-resultCh:
+		require.NoError(t, got.err)
+		require.NotNil(t, got.result)
+		require.Equal(t, 15, got.result.Usage.InputTokens)
+		require.Equal(t, 6, got.result.Usage.OutputTokens)
+		require.Equal(t, 5, got.result.Usage.CacheReadInputTokens)
+	case <-time.After(time.Second):
+		require.Fail(t, "ForwardAsAnthropic should return after terminal usage event even if upstream keeps the connection open")
+	}
+}
+
+func TestForwardAsAnthropic_BufferedTerminalWithoutUpstreamCloseReturns(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	body := []byte(`{"model":"gpt-5.4","max_tokens":16,"messages":[{"role":"user","content":"hello"}],"stream":false}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", bytes.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	upstreamBody := []byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","model":"gpt-5.4","status":"completed","output":[{"type":"message","id":"msg_1","role":"assistant","status":"completed","content":[{"type":"output_text","text":"ok"}]}],"usage":{"input_tokens":15,"output_tokens":6,"total_tokens":21,"input_tokens_details":{"cached_tokens":5}}}}` + "\n\n")
+	upstreamStream := newOpenAICompatBlockingReadCloser(upstreamBody)
+	defer upstreamStream.Close()
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_buffered_terminal_no_close"}},
+		Body:       upstreamStream,
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	type forwardResult struct {
+		result *OpenAIForwardResult
+		err    error
+	}
+	resultCh := make(chan forwardResult, 1)
+	go func() {
+		result, err := svc.ForwardAsAnthropic(context.Background(), c, account, body, "", "gpt-5.1")
+		resultCh <- forwardResult{result: result, err: err}
+	}()
+
+	select {
+	case got := <-resultCh:
+		require.NoError(t, got.err)
+		require.NotNil(t, got.result)
+		require.Equal(t, 15, got.result.Usage.InputTokens)
+		require.Equal(t, 6, got.result.Usage.OutputTokens)
+		require.Equal(t, 5, got.result.Usage.CacheReadInputTokens)
+		require.Contains(t, rec.Body.String(), `"stop_reason":"end_turn"`)
+	case <-time.After(time.Second):
+		require.Fail(t, "ForwardAsAnthropic buffered response should return after terminal usage event even if upstream keeps the connection open")
+	}
+}
+
+func TestForwardAsAnthropic_DoneSentinelWithoutTerminalReturnsError(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	body := []byte(`{"model":"gpt-5.4","max_tokens":16,"messages":[{"role":"user","content":"hello"}],"stream":true}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", bytes.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	upstreamBody := "data: [DONE]\n\n"
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_missing_terminal"}},
+		Body:       io.NopCloser(strings.NewReader(upstreamBody)),
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	result, err := svc.ForwardAsAnthropic(context.Background(), c, account, body, "", "gpt-5.1")
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "missing terminal event")
+	require.NotNil(t, result)
+	require.Zero(t, result.Usage.InputTokens)
+	require.Zero(t, result.Usage.OutputTokens)
+}
+
+func TestForwardAsAnthropic_UpstreamRequestIgnoresClientCancel(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	reqCtx, cancel := context.WithCancel(context.Background())
+	body := []byte(`{"model":"gpt-5.4","max_tokens":16,"messages":[{"role":"user","content":"hello"}],"stream":false}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", bytes.NewReader(body)).WithContext(reqCtx)
+	c.Request.Header.Set("Content-Type", "application/json")
+	cancel()
+
+	upstreamBody := strings.Join([]string{
+		`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","model":"gpt-5.4","status":"completed","output":[{"type":"message","id":"msg_1","role":"assistant","status":"completed","content":[{"type":"output_text","text":"ok"}]}],"usage":{"input_tokens":5,"output_tokens":2,"total_tokens":7}}}`,
+		"",
+		"data: [DONE]",
+		"",
+	}, "\n")
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_ctx"}},
+		Body:       io.NopCloser(strings.NewReader(upstreamBody)),
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	result, err := svc.ForwardAsAnthropic(reqCtx, c, account, body, "", "gpt-5.1")
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.NotNil(t, upstream.lastReq)
+	require.NoError(t, upstream.lastReq.Context().Err())
+}

backend/internal/service/openai_gateway_chat_completions.go

@@ -10,6 +10,7 @@ import (
 	"io"
 	"net/http"
 	"strings"
+	"sync/atomic"
 	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/apicompat"
@@ -189,7 +190,9 @@ func (s *OpenAIGatewayService) ForwardAsChatCompletions(
 	}
 
 	// 6. Build upstream request
-	upstreamReq, err := s.buildUpstreamRequest(ctx, c, account, responsesBody, token, true, promptCacheKey, false)
+	upstreamCtx, releaseUpstreamCtx := detachUpstreamContext(ctx)
+	upstreamReq, err := s.buildUpstreamRequest(upstreamCtx, c, account, responsesBody, token, true, promptCacheKey, false)
+	releaseUpstreamCtx()
 	if err != nil {
 		return nil, fmt.Errorf("build upstream request: %w", err)
 	}
@@ -348,59 +351,9 @@ func (s *OpenAIGatewayService) handleChatBufferedStreamingResponse(
 ) (*OpenAIForwardResult, error) {
 	requestID := resp.Header.Get("x-request-id")
 
-	scanner := bufio.NewScanner(resp.Body)
+	finalResponse, usage, acc, err := s.readOpenAICompatBufferedTerminal(resp, "openai chat_completions buffered", requestID)
-	maxLineSize := defaultMaxLineSize
+	if err != nil {
-	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		return nil, err
-		maxLineSize = s.cfg.Gateway.MaxLineSize
-	}
-	scanner.Buffer(make([]byte, 0, 64*1024), maxLineSize)
-
-	var finalResponse *apicompat.ResponsesResponse
-	var usage OpenAIUsage
-	acc := apicompat.NewBufferedResponseAccumulator()
-
-	for scanner.Scan() {
-		line := scanner.Text()
-		if !strings.HasPrefix(line, "data: ") || line == "data: [DONE]" {
-			continue
-		}
-		payload := line[6:]
-
-		var event apicompat.ResponsesStreamEvent
-		if err := json.Unmarshal([]byte(payload), &event); err != nil {
-			logger.L().Warn("openai chat_completions buffered: failed to parse event",
-				zap.Error(err),
-				zap.String("request_id", requestID),
-			)
-			continue
-		}
-
-		// Accumulate delta content for fallback when terminal output is empty.
-		acc.ProcessEvent(&event)
-
-		if (event.Type == "response.completed" || event.Type == "response.done" ||
-			event.Type == "response.incomplete" || event.Type == "response.failed") &&
-			event.Response != nil {
-			finalResponse = event.Response
-			if event.Response.Usage != nil {
-				usage = OpenAIUsage{
-					InputTokens:  event.Response.Usage.InputTokens,
-					OutputTokens: event.Response.Usage.OutputTokens,
-				}
-				if event.Response.Usage.InputTokensDetails != nil {
-					usage.CacheReadInputTokens = event.Response.Usage.InputTokensDetails.CachedTokens
-				}
-			}
-		}
-	}
-
-	if err := scanner.Err(); err != nil {
-		if !errors.Is(err, context.Canceled) && !errors.Is(err, context.DeadlineExceeded) {
-			logger.L().Warn("openai chat_completions buffered: read error",
-				zap.Error(err),
-				zap.String("request_id", requestID),
-			)
-		}
 	}
 
 	if finalResponse == nil {
@@ -459,6 +412,7 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 	var usage OpenAIUsage
 	var firstTokenMs *int
 	firstChunk := true
+	clientDisconnected := false
 
 	scanner := bufio.NewScanner(resp.Body)
 	maxLineSize := defaultMaxLineSize
@@ -467,6 +421,20 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 	}
 	scanner.Buffer(make([]byte, 0, 64*1024), maxLineSize)
 
+	streamInterval := time.Duration(0)
+	if s.cfg != nil && s.cfg.Gateway.StreamDataIntervalTimeout > 0 {
+		streamInterval = time.Duration(s.cfg.Gateway.StreamDataIntervalTimeout) * time.Second
+	}
+	var intervalTicker *time.Ticker
+	if streamInterval > 0 {
+		intervalTicker = time.NewTicker(streamInterval)
+		defer intervalTicker.Stop()
+	}
+	var intervalCh <-chan time.Time
+	if intervalTicker != nil {
+		intervalCh = intervalTicker.C
+	}
+
 	resultWithUsage := func() *OpenAIForwardResult {
 		return &OpenAIForwardResult{
 			RequestID:     requestID,
@@ -496,54 +464,66 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 			return false
 		}
 
-		// Extract usage from completion events
+		// 仅按兼容转换器支持的终止事件提取 usage，避免无意扩大事件语义。
-		if (event.Type == "response.completed" || event.Type == "response.incomplete" || event.Type == "response.failed") &&
+		isTerminalEvent := isOpenAICompatResponsesTerminalEvent(event.Type)
-			event.Response != nil && event.Response.Usage != nil {
+		if isTerminalEvent && event.Response != nil && event.Response.Usage != nil {
-			usage = OpenAIUsage{
+			usage = copyOpenAIUsageFromResponsesUsage(event.Response.Usage)
-				InputTokens:  event.Response.Usage.InputTokens,
-				OutputTokens: event.Response.Usage.OutputTokens,
-			}
-			if event.Response.Usage.InputTokensDetails != nil {
-				usage.CacheReadInputTokens = event.Response.Usage.InputTokensDetails.CachedTokens
-			}
 		}
 
 		chunks := apicompat.ResponsesEventToChatChunks(&event, state)
-		for _, chunk := range chunks {
+		if !clientDisconnected {
-			sse, err := apicompat.ChatChunkToSSE(chunk)
+			for _, chunk := range chunks {
-			if err != nil {
+				sse, err := apicompat.ChatChunkToSSE(chunk)
-				logger.L().Warn("openai chat_completions stream: failed to marshal chunk",
+				if err != nil {
-					zap.Error(err),
+					logger.L().Warn("openai chat_completions stream: failed to marshal chunk",
-					zap.String("request_id", requestID),
+						zap.Error(err),
-				)
+						zap.String("request_id", requestID),
-				continue
+					)
-			}
+					continue
-			if _, err := fmt.Fprint(c.Writer, sse); err != nil {
+				}
-				logger.L().Info("openai chat_completions stream: client disconnected",
+				if _, err := fmt.Fprint(c.Writer, sse); err != nil {
-					zap.String("request_id", requestID),
+					clientDisconnected = true
-				)
+					logger.L().Info("openai chat_completions stream: client disconnected, continuing to drain upstream for billing",
-				return true
+						zap.String("request_id", requestID),
+					)
+					break
+				}
 			}
 		}
-		if len(chunks) > 0 {
+		if len(chunks) > 0 && !clientDisconnected {
 			c.Writer.Flush()
 		}
-		return false
+		return isTerminalEvent
 	}
 
 	finalizeStream := func() (*OpenAIForwardResult, error) {
-		if finalChunks := apicompat.FinalizeResponsesChatStream(state); len(finalChunks) > 0 {
+		if finalChunks := apicompat.FinalizeResponsesChatStream(state); len(finalChunks) > 0 && !clientDisconnected {
 			for _, chunk := range finalChunks {
 				sse, err := apicompat.ChatChunkToSSE(chunk)
 				if err != nil {
 					continue
 				}
-				fmt.Fprint(c.Writer, sse) //nolint:errcheck
+				if _, err := fmt.Fprint(c.Writer, sse); err != nil {
+					clientDisconnected = true
+					logger.L().Info("openai chat_completions stream: client disconnected during final flush",
+						zap.String("request_id", requestID),
+					)
+					break
+				}
 			}
 		}
 		// Send [DONE] sentinel
-		fmt.Fprint(c.Writer, "data: [DONE]\n\n") //nolint:errcheck
+		if !clientDisconnected {
-		c.Writer.Flush()
+			if _, err := fmt.Fprint(c.Writer, "data: [DONE]\n\n"); err != nil {
+				clientDisconnected = true
+				logger.L().Info("openai chat_completions stream: client disconnected during done flush",
+					zap.String("request_id", requestID),
+				)
+			}
+		}
+		if !clientDisconnected {
+			c.Writer.Flush()
+		}
 		return resultWithUsage(), nil
 	}
 
@@ -555,6 +535,9 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 			)
 		}
 	}
+	missingTerminalErr := func() (*OpenAIForwardResult, error) {
+		return resultWithUsage(), fmt.Errorf("stream usage incomplete: missing terminal event")
+	}
 
 	// Determine keepalive interval
 	keepaliveInterval := time.Duration(0)
@@ -563,18 +546,25 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 	}
 
 	// No keepalive: fast synchronous path
-	if keepaliveInterval <= 0 {
+	if streamInterval <= 0 && keepaliveInterval <= 0 {
 		for scanner.Scan() {
 			line := scanner.Text()
-			if !strings.HasPrefix(line, "data: ") || line == "data: [DONE]" {
+			payload, ok := extractOpenAISSEDataLine(line)
+			if !ok {
 				continue
 			}
-			if processDataLine(line[6:]) {
+			if strings.TrimSpace(payload) == "[DONE]" {
-				return resultWithUsage(), nil
+				return missingTerminalErr()
+			}
+			if processDataLine(payload) {
+				return finalizeStream()
 			}
 		}
-		handleScanErr(scanner.Err())
+		if err := scanner.Err(); err != nil {
-		return finalizeStream()
+			handleScanErr(err)
+			return resultWithUsage(), fmt.Errorf("stream usage incomplete: %w", err)
+		}
+		return missingTerminalErr()
 	}
 
 	// With keepalive: goroutine + channel + select
@@ -584,6 +574,8 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 	}
 	events := make(chan scanEvent, 16)
 	done := make(chan struct{})
+	var lastReadAt int64
+	atomic.StoreInt64(&lastReadAt, time.Now().UnixNano())
 	sendEvent := func(ev scanEvent) bool {
 		select {
 		case events <- ev:
@@ -595,6 +587,7 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 	go func() {
 		defer close(events)
 		for scanner.Scan() {
+			atomic.StoreInt64(&lastReadAt, time.Now().UnixNano())
 			if !sendEvent(scanEvent{line: scanner.Text()}) {
 				return
 			}
@@ -605,30 +598,59 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 	}()
 	defer close(done)
 
-	keepaliveTicker := time.NewTicker(keepaliveInterval)
+	var keepaliveTicker *time.Ticker
-	defer keepaliveTicker.Stop()
+	if keepaliveInterval > 0 {
+		keepaliveTicker = time.NewTicker(keepaliveInterval)
+		defer keepaliveTicker.Stop()
+	}
+	var keepaliveCh <-chan time.Time
+	if keepaliveTicker != nil {
+		keepaliveCh = keepaliveTicker.C
+	}
 	lastDataAt := time.Now()
 
 	for {
 		select {
 		case ev, ok := <-events:
 			if !ok {
-				return finalizeStream()
+				return missingTerminalErr()
 			}
 			if ev.err != nil {
 				handleScanErr(ev.err)
-				return finalizeStream()
+				return resultWithUsage(), fmt.Errorf("stream usage incomplete: %w", ev.err)
 			}
 			lastDataAt = time.Now()
 			line := ev.line
-			if !strings.HasPrefix(line, "data: ") || line == "data: [DONE]" {
+			payload, ok := extractOpenAISSEDataLine(line)
+			if !ok {
 				continue
 			}
-			if processDataLine(line[6:]) {
+			if strings.TrimSpace(payload) == "[DONE]" {
-				return resultWithUsage(), nil
+				return missingTerminalErr()
+			}
+			if processDataLine(payload) {
+				return finalizeStream()
 			}
 
-		case <-keepaliveTicker.C:
+		case <-intervalCh:
+			lastRead := time.Unix(0, atomic.LoadInt64(&lastReadAt))
+			if time.Since(lastRead) < streamInterval {
+				continue
+			}
+			if clientDisconnected {
+				return resultWithUsage(), fmt.Errorf("stream usage incomplete after timeout")
+			}
+			logger.L().Warn("openai chat_completions stream: data interval timeout",
+				zap.String("request_id", requestID),
+				zap.String("model", originalModel),
+				zap.Duration("interval", streamInterval),
+			)
+			return resultWithUsage(), fmt.Errorf("stream data interval timeout")
+
+		case <-keepaliveCh:
+			if clientDisconnected {
+				continue
+			}
 			if time.Since(lastDataAt) < keepaliveInterval {
 				continue
 			}
@@ -637,7 +659,8 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 				logger.L().Info("openai chat_completions stream: client disconnected during keepalive",
 					zap.String("request_id", requestID),
 				)
-				return resultWithUsage(), nil
+				clientDisconnected = true
+				continue
 			}
 			c.Writer.Flush()
 		}

backend/internal/service/openai_gateway_chat_completions_test.go

@@ -1,13 +1,36 @@
 package service
 
 import (
+	"bytes"
+	"context"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
 	"testing"
+	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/apicompat"
+	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/require"
 	"github.com/tidwall/gjson"
 )
 
+type openAIChatFailingWriter struct {
+	gin.ResponseWriter
+	failAfter int
+	writes    int
+}
+
+func (w *openAIChatFailingWriter) Write(p []byte) (int, error) {
+	if w.writes >= w.failAfter {
+		return 0, errors.New("write failed: client disconnected")
+	}
+	w.writes++
+	return w.ResponseWriter.Write(p)
+}
+
 func TestNormalizeResponsesRequestServiceTier(t *testing.T) {
 	t.Parallel()
 
@@ -73,3 +96,238 @@ func TestNormalizeResponsesBodyServiceTier(t *testing.T) {
 	require.Empty(t, tier)
 	require.False(t, gjson.GetBytes(body, "service_tier").Exists())
 }
+
+func TestForwardAsChatCompletions_ClientDisconnectDrainsUpstreamUsage(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Writer = &openAIChatFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+	body := []byte(`{"model":"gpt-5.4","messages":[{"role":"user","content":"hello"}],"stream":true}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	upstreamBody := strings.Join([]string{
+		`data: {"type":"response.created","response":{"id":"resp_1","model":"gpt-5.4","status":"in_progress","output":[]}}`,
+		"",
+		`data: {"type":"response.output_text.delta","delta":"ok"}`,
+		"",
+		`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","model":"gpt-5.4","status":"completed","output":[{"type":"message","id":"msg_1","role":"assistant","status":"completed","content":[{"type":"output_text","text":"ok"}]}],"usage":{"input_tokens":11,"output_tokens":5,"total_tokens":16,"input_tokens_details":{"cached_tokens":4}}}}`,
+		"",
+		"data: [DONE]",
+		"",
+	}, "\n")
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_chat_disconnect"}},
+		Body:       io.NopCloser(strings.NewReader(upstreamBody)),
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	result, err := svc.ForwardAsChatCompletions(context.Background(), c, account, body, "", "gpt-5.1")
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, 11, result.Usage.InputTokens)
+	require.Equal(t, 5, result.Usage.OutputTokens)
+	require.Equal(t, 4, result.Usage.CacheReadInputTokens)
+}
+
+func TestForwardAsChatCompletions_TerminalUsageWithoutUpstreamCloseReturns(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Writer = &openAIChatFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+	body := []byte(`{"model":"gpt-5.4","messages":[{"role":"user","content":"hello"}],"stream":true}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	upstreamBody := []byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","model":"gpt-5.4","status":"completed","output":[{"type":"message","id":"msg_1","role":"assistant","status":"completed","content":[{"type":"output_text","text":"ok"}]}],"usage":{"input_tokens":17,"output_tokens":8,"total_tokens":25,"input_tokens_details":{"cached_tokens":6}}}}` + "\n\n")
+	upstreamStream := newOpenAICompatBlockingReadCloser(upstreamBody)
+	defer upstreamStream.Close()
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_chat_terminal_no_close"}},
+		Body:       upstreamStream,
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	type forwardResult struct {
+		result *OpenAIForwardResult
+		err    error
+	}
+	resultCh := make(chan forwardResult, 1)
+	go func() {
+		result, err := svc.ForwardAsChatCompletions(context.Background(), c, account, body, "", "gpt-5.1")
+		resultCh <- forwardResult{result: result, err: err}
+	}()
+
+	select {
+	case got := <-resultCh:
+		require.NoError(t, got.err)
+		require.NotNil(t, got.result)
+		require.Equal(t, 17, got.result.Usage.InputTokens)
+		require.Equal(t, 8, got.result.Usage.OutputTokens)
+		require.Equal(t, 6, got.result.Usage.CacheReadInputTokens)
+	case <-time.After(time.Second):
+		require.Fail(t, "ForwardAsChatCompletions should return after terminal usage event even if upstream keeps the connection open")
+	}
+}
+
+func TestForwardAsChatCompletions_BufferedTerminalWithoutUpstreamCloseReturns(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	body := []byte(`{"model":"gpt-5.4","messages":[{"role":"user","content":"hello"}],"stream":false}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	upstreamBody := []byte(`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","model":"gpt-5.4","status":"completed","output":[{"type":"message","id":"msg_1","role":"assistant","status":"completed","content":[{"type":"output_text","text":"ok"}]}],"usage":{"input_tokens":17,"output_tokens":8,"total_tokens":25,"input_tokens_details":{"cached_tokens":6}}}}` + "\n\n")
+	upstreamStream := newOpenAICompatBlockingReadCloser(upstreamBody)
+	defer upstreamStream.Close()
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_chat_buffered_terminal_no_close"}},
+		Body:       upstreamStream,
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	type forwardResult struct {
+		result *OpenAIForwardResult
+		err    error
+	}
+	resultCh := make(chan forwardResult, 1)
+	go func() {
+		result, err := svc.ForwardAsChatCompletions(context.Background(), c, account, body, "", "gpt-5.1")
+		resultCh <- forwardResult{result: result, err: err}
+	}()
+
+	select {
+	case got := <-resultCh:
+		require.NoError(t, got.err)
+		require.NotNil(t, got.result)
+		require.Equal(t, 17, got.result.Usage.InputTokens)
+		require.Equal(t, 8, got.result.Usage.OutputTokens)
+		require.Equal(t, 6, got.result.Usage.CacheReadInputTokens)
+		require.Contains(t, rec.Body.String(), `"finish_reason":"stop"`)
+	case <-time.After(time.Second):
+		require.Fail(t, "ForwardAsChatCompletions buffered response should return after terminal usage event even if upstream keeps the connection open")
+	}
+}
+
+func TestForwardAsChatCompletions_DoneSentinelWithoutTerminalReturnsError(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	body := []byte(`{"model":"gpt-5.4","messages":[{"role":"user","content":"hello"}],"stream":true}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	upstreamBody := "data: [DONE]\n\n"
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_chat_missing_terminal"}},
+		Body:       io.NopCloser(strings.NewReader(upstreamBody)),
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	result, err := svc.ForwardAsChatCompletions(context.Background(), c, account, body, "", "gpt-5.1")
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "missing terminal event")
+	require.NotNil(t, result)
+	require.Zero(t, result.Usage.InputTokens)
+	require.Zero(t, result.Usage.OutputTokens)
+}
+
+func TestForwardAsChatCompletions_UpstreamRequestIgnoresClientCancel(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	reqCtx, cancel := context.WithCancel(context.Background())
+	body := []byte(`{"model":"gpt-5.4","messages":[{"role":"user","content":"hello"}],"stream":false}`)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(body)).WithContext(reqCtx)
+	c.Request.Header.Set("Content-Type", "application/json")
+	cancel()
+
+	upstreamBody := strings.Join([]string{
+		`data: {"type":"response.completed","response":{"id":"resp_1","object":"response","model":"gpt-5.4","status":"completed","output":[{"type":"message","id":"msg_1","role":"assistant","status":"completed","content":[{"type":"output_text","text":"ok"}]}],"usage":{"input_tokens":5,"output_tokens":2,"total_tokens":7}}}`,
+		"",
+		"data: [DONE]",
+		"",
+	}, "\n")
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_chat_ctx"}},
+		Body:       io.NopCloser(strings.NewReader(upstreamBody)),
+	}}
+
+	svc := &OpenAIGatewayService{httpUpstream: upstream}
+	account := &Account{
+		ID:          1,
+		Name:        "openai-oauth",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"access_token":       "oauth-token",
+			"chatgpt_account_id": "chatgpt-acc",
+		},
+	}
+
+	result, err := svc.ForwardAsChatCompletions(reqCtx, c, account, body, "", "gpt-5.1")
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.NotNil(t, upstream.lastReq)
+	require.NoError(t, upstream.lastReq.Context().Err())
+}

backend/internal/service/openai_gateway_messages.go

@@ -10,6 +10,7 @@ import (
 	"io"
 	"net/http"
 	"strings"
+	"sync/atomic"
 	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/apicompat"
@@ -163,7 +164,9 @@ func (s *OpenAIGatewayService) ForwardAsAnthropic(
 	}
 
 	// 6. Build upstream request
-	upstreamReq, err := s.buildUpstreamRequest(ctx, c, account, responsesBody, token, isStream, promptCacheKey, false)
+	upstreamCtx, releaseUpstreamCtx := detachUpstreamContext(ctx)
+	upstreamReq, err := s.buildUpstreamRequest(upstreamCtx, c, account, responsesBody, token, isStream, promptCacheKey, false)
+	releaseUpstreamCtx()
 	if err != nil {
 		return nil, fmt.Errorf("build upstream request: %w", err)
 	}
@@ -296,61 +299,9 @@ func (s *OpenAIGatewayService) handleAnthropicBufferedStreamingResponse(
 ) (*OpenAIForwardResult, error) {
 	requestID := resp.Header.Get("x-request-id")
 
-	scanner := bufio.NewScanner(resp.Body)
+	finalResponse, usage, acc, err := s.readOpenAICompatBufferedTerminal(resp, "openai messages buffered", requestID)
-	maxLineSize := defaultMaxLineSize
+	if err != nil {
-	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		return nil, err
-		maxLineSize = s.cfg.Gateway.MaxLineSize
-	}
-	scanner.Buffer(make([]byte, 0, 64*1024), maxLineSize)
-
-	var finalResponse *apicompat.ResponsesResponse
-	var usage OpenAIUsage
-	acc := apicompat.NewBufferedResponseAccumulator()
-
-	for scanner.Scan() {
-		line := scanner.Text()
-
-		if !strings.HasPrefix(line, "data: ") || line == "data: [DONE]" {
-			continue
-		}
-		payload := line[6:]
-
-		var event apicompat.ResponsesStreamEvent
-		if err := json.Unmarshal([]byte(payload), &event); err != nil {
-			logger.L().Warn("openai messages buffered: failed to parse event",
-				zap.Error(err),
-				zap.String("request_id", requestID),
-			)
-			continue
-		}
-
-		// Accumulate delta content for fallback when terminal output is empty.
-		acc.ProcessEvent(&event)
-
-		// Terminal events carry the complete ResponsesResponse with output + usage.
-		if (event.Type == "response.completed" || event.Type == "response.done" ||
-			event.Type == "response.incomplete" || event.Type == "response.failed") &&
-			event.Response != nil {
-			finalResponse = event.Response
-			if event.Response.Usage != nil {
-				usage = OpenAIUsage{
-					InputTokens:  event.Response.Usage.InputTokens,
-					OutputTokens: event.Response.Usage.OutputTokens,
-				}
-				if event.Response.Usage.InputTokensDetails != nil {
-					usage.CacheReadInputTokens = event.Response.Usage.InputTokensDetails.CachedTokens
-				}
-			}
-		}
-	}
-
-	if err := scanner.Err(); err != nil {
-		if !errors.Is(err, context.Canceled) && !errors.Is(err, context.DeadlineExceeded) {
-			logger.L().Warn("openai messages buffered: read error",
-				zap.Error(err),
-				zap.String("request_id", requestID),
-			)
-		}
 	}
 
 	if finalResponse == nil {
@@ -380,6 +331,153 @@ func (s *OpenAIGatewayService) handleAnthropicBufferedStreamingResponse(
 	}, nil
 }
 
+func isOpenAICompatResponsesTerminalEvent(eventType string) bool {
+	switch strings.TrimSpace(eventType) {
+	case "response.completed", "response.done", "response.incomplete", "response.failed":
+		return true
+	default:
+		return false
+	}
+}
+
+func isOpenAICompatDoneSentinelLine(line string) bool {
+	payload, ok := extractOpenAISSEDataLine(line)
+	return ok && strings.TrimSpace(payload) == "[DONE]"
+}
+
+func (s *OpenAIGatewayService) readOpenAICompatBufferedTerminal(
+	resp *http.Response,
+	logPrefix string,
+	requestID string,
+) (*apicompat.ResponsesResponse, OpenAIUsage, *apicompat.BufferedResponseAccumulator, error) {
+	acc := apicompat.NewBufferedResponseAccumulator()
+	var usage OpenAIUsage
+	if resp == nil || resp.Body == nil {
+		return nil, usage, acc, errors.New("upstream response body is nil")
+	}
+
+	scanner := bufio.NewScanner(resp.Body)
+	maxLineSize := defaultMaxLineSize
+	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		maxLineSize = s.cfg.Gateway.MaxLineSize
+	}
+	scanner.Buffer(make([]byte, 0, 64*1024), maxLineSize)
+
+	streamInterval := time.Duration(0)
+	if s.cfg != nil && s.cfg.Gateway.StreamDataIntervalTimeout > 0 {
+		streamInterval = time.Duration(s.cfg.Gateway.StreamDataIntervalTimeout) * time.Second
+	}
+	var timeoutCh <-chan time.Time
+	var timeoutTimer *time.Timer
+	resetTimeout := func() {
+		if streamInterval <= 0 {
+			return
+		}
+		if timeoutTimer == nil {
+			timeoutTimer = time.NewTimer(streamInterval)
+			timeoutCh = timeoutTimer.C
+			return
+		}
+		if !timeoutTimer.Stop() {
+			select {
+			case <-timeoutTimer.C:
+			default:
+			}
+		}
+		timeoutTimer.Reset(streamInterval)
+	}
+	stopTimeout := func() {
+		if timeoutTimer == nil {
+			return
+		}
+		if !timeoutTimer.Stop() {
+			select {
+			case <-timeoutTimer.C:
+			default:
+			}
+		}
+	}
+	resetTimeout()
+	defer stopTimeout()
+
+	type scanEvent struct {
+		line string
+		err  error
+	}
+	events := make(chan scanEvent, 16)
+	done := make(chan struct{})
+	go func() {
+		defer close(events)
+		for scanner.Scan() {
+			select {
+			case events <- scanEvent{line: scanner.Text()}:
+			case <-done:
+				return
+			}
+		}
+		if err := scanner.Err(); err != nil {
+			select {
+			case events <- scanEvent{err: err}:
+			case <-done:
+			}
+		}
+	}()
+	defer close(done)
+
+	for {
+		select {
+		case ev, ok := <-events:
+			if !ok {
+				return nil, usage, acc, nil
+			}
+			resetTimeout()
+			if ev.err != nil {
+				if !errors.Is(ev.err, context.Canceled) && !errors.Is(ev.err, context.DeadlineExceeded) {
+					logger.L().Warn(logPrefix+": read error",
+						zap.Error(ev.err),
+						zap.String("request_id", requestID),
+					)
+				}
+				return nil, usage, acc, ev.err
+			}
+
+			payload, ok := extractOpenAISSEDataLine(ev.line)
+			if !ok || payload == "" {
+				continue
+			}
+			if strings.TrimSpace(payload) == "[DONE]" {
+				return nil, usage, acc, nil
+			}
+
+			var event apicompat.ResponsesStreamEvent
+			if err := json.Unmarshal([]byte(payload), &event); err != nil {
+				logger.L().Warn(logPrefix+": failed to parse event",
+					zap.Error(err),
+					zap.String("request_id", requestID),
+				)
+				continue
+			}
+
+			acc.ProcessEvent(&event)
+
+			if isOpenAICompatResponsesTerminalEvent(event.Type) && event.Response != nil {
+				if event.Response.Usage != nil {
+					usage = copyOpenAIUsageFromResponsesUsage(event.Response.Usage)
+				}
+				return event.Response, usage, acc, nil
+			}
+
+		case <-timeoutCh:
+			_ = resp.Body.Close()
+			logger.L().Warn(logPrefix+": data interval timeout",
+				zap.String("request_id", requestID),
+				zap.Duration("interval", streamInterval),
+			)
+			return nil, usage, acc, fmt.Errorf("stream data interval timeout")
+		}
+	}
+}
+
 // handleAnthropicStreamingResponse reads Responses SSE events from upstream,
 // converts each to Anthropic SSE events, and writes them to the client.
 // When StreamKeepaliveInterval is configured, it uses a goroutine + channel
@@ -409,6 +507,7 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 	var usage OpenAIUsage
 	var firstTokenMs *int
 	firstChunk := true
+	clientDisconnected := false
 
 	scanner := bufio.NewScanner(resp.Body)
 	maxLineSize := defaultMaxLineSize
@@ -417,6 +516,20 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 	}
 	scanner.Buffer(make([]byte, 0, 64*1024), maxLineSize)
 
+	streamInterval := time.Duration(0)
+	if s.cfg != nil && s.cfg.Gateway.StreamDataIntervalTimeout > 0 {
+		streamInterval = time.Duration(s.cfg.Gateway.StreamDataIntervalTimeout) * time.Second
+	}
+	var intervalTicker *time.Ticker
+	if streamInterval > 0 {
+		intervalTicker = time.NewTicker(streamInterval)
+		defer intervalTicker.Stop()
+	}
+	var intervalCh <-chan time.Time
+	if intervalTicker != nil {
+		intervalCh = intervalTicker.C
+	}
+
 	// resultWithUsage builds the final result snapshot.
 	resultWithUsage := func() *OpenAIForwardResult {
 		return &OpenAIForwardResult{
@@ -432,7 +545,6 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 	}
 
 	// processDataLine handles a single "data: ..." SSE line from upstream.
-	// Returns (clientDisconnected bool).
 	processDataLine := func(payload string) bool {
 		if firstChunk {
 			firstChunk = false
@@ -449,53 +561,58 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 			return false
 		}
 
-		// Extract usage from completion events
+		// 仅按兼容转换器支持的终止事件提取 usage，避免无意扩大事件语义。
-		if (event.Type == "response.completed" || event.Type == "response.incomplete" || event.Type == "response.failed") &&
+		isTerminalEvent := isOpenAICompatResponsesTerminalEvent(event.Type)
-			event.Response != nil && event.Response.Usage != nil {
+		if isTerminalEvent && event.Response != nil && event.Response.Usage != nil {
-			usage = OpenAIUsage{
+			usage = copyOpenAIUsageFromResponsesUsage(event.Response.Usage)
-				InputTokens:  event.Response.Usage.InputTokens,
-				OutputTokens: event.Response.Usage.OutputTokens,
-			}
-			if event.Response.Usage.InputTokensDetails != nil {
-				usage.CacheReadInputTokens = event.Response.Usage.InputTokensDetails.CachedTokens
-			}
 		}
 
 		// Convert to Anthropic events
 		events := apicompat.ResponsesEventToAnthropicEvents(&event, state)
-		for _, evt := range events {
+		if !clientDisconnected {
-			sse, err := apicompat.ResponsesAnthropicEventToSSE(evt)
+			for _, evt := range events {
-			if err != nil {
+				sse, err := apicompat.ResponsesAnthropicEventToSSE(evt)
-				logger.L().Warn("openai messages stream: failed to marshal event",
+				if err != nil {
-					zap.Error(err),
+					logger.L().Warn("openai messages stream: failed to marshal event",
-					zap.String("request_id", requestID),
+						zap.Error(err),
-				)
+						zap.String("request_id", requestID),
-				continue
+					)
-			}
+					continue
-			if _, err := fmt.Fprint(c.Writer, sse); err != nil {
+				}
-				logger.L().Info("openai messages stream: client disconnected",
+				if _, err := fmt.Fprint(c.Writer, sse); err != nil {
-					zap.String("request_id", requestID),
+					clientDisconnected = true
-				)
+					logger.L().Info("openai messages stream: client disconnected, continuing to drain upstream for billing",
-				return true
+						zap.String("request_id", requestID),
+					)
+					break
+				}
 			}
 		}
-		if len(events) > 0 {
+		if len(events) > 0 && !clientDisconnected {
 			c.Writer.Flush()
 		}
-		return false
+		return isTerminalEvent
 	}
 
 	// finalizeStream sends any remaining Anthropic events and returns the result.
 	finalizeStream := func() (*OpenAIForwardResult, error) {
-		if finalEvents := apicompat.FinalizeResponsesAnthropicStream(state); len(finalEvents) > 0 {
+		if finalEvents := apicompat.FinalizeResponsesAnthropicStream(state); len(finalEvents) > 0 && !clientDisconnected {
 			for _, evt := range finalEvents {
 				sse, err := apicompat.ResponsesAnthropicEventToSSE(evt)
 				if err != nil {
 					continue
 				}
-				fmt.Fprint(c.Writer, sse) //nolint:errcheck
+				if _, err := fmt.Fprint(c.Writer, sse); err != nil {
+					clientDisconnected = true
+					logger.L().Info("openai messages stream: client disconnected during final flush",
+						zap.String("request_id", requestID),
+					)
+					break
+				}
+			}
+			if !clientDisconnected {
+				c.Writer.Flush()
 			}
-			c.Writer.Flush()
 		}
 		return resultWithUsage(), nil
 	}
@@ -509,6 +626,9 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 			)
 		}
 	}
+	missingTerminalErr := func() (*OpenAIForwardResult, error) {
+		return resultWithUsage(), fmt.Errorf("stream usage incomplete: missing terminal event")
+	}
 
 	// ── Determine keepalive interval ──
 	keepaliveInterval := time.Duration(0)
@@ -517,18 +637,25 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 	}
 
 	// ── No keepalive: fast synchronous path (no goroutine overhead) ──
-	if keepaliveInterval <= 0 {
+	if streamInterval <= 0 && keepaliveInterval <= 0 {
 		for scanner.Scan() {
 			line := scanner.Text()
-			if !strings.HasPrefix(line, "data: ") || line == "data: [DONE]" {
+			payload, ok := extractOpenAISSEDataLine(line)
+			if !ok {
 				continue
 			}
-			if processDataLine(line[6:]) {
+			if strings.TrimSpace(payload) == "[DONE]" {
-				return resultWithUsage(), nil
+				return missingTerminalErr()
+			}
+			if processDataLine(payload) {
+				return finalizeStream()
 			}
 		}
-		handleScanErr(scanner.Err())
+		if err := scanner.Err(); err != nil {
-		return finalizeStream()
+			handleScanErr(err)
+			return resultWithUsage(), fmt.Errorf("stream usage incomplete: %w", err)
+		}
+		return missingTerminalErr()
 	}
 
 	// ── With keepalive: goroutine + channel + select ──
@@ -538,6 +665,8 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 	}
 	events := make(chan scanEvent, 16)
 	done := make(chan struct{})
+	var lastReadAt int64
+	atomic.StoreInt64(&lastReadAt, time.Now().UnixNano())
 	sendEvent := func(ev scanEvent) bool {
 		select {
 		case events <- ev:
@@ -549,6 +678,7 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 	go func() {
 		defer close(events)
 		for scanner.Scan() {
+			atomic.StoreInt64(&lastReadAt, time.Now().UnixNano())
 			if !sendEvent(scanEvent{line: scanner.Text()}) {
 				return
 			}
@@ -559,8 +689,15 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 	}()
 	defer close(done)
 
-	keepaliveTicker := time.NewTicker(keepaliveInterval)
+	var keepaliveTicker *time.Ticker
-	defer keepaliveTicker.Stop()
+	if keepaliveInterval > 0 {
+		keepaliveTicker = time.NewTicker(keepaliveInterval)
+		defer keepaliveTicker.Stop()
+	}
+	var keepaliveCh <-chan time.Time
+	if keepaliveTicker != nil {
+		keepaliveCh = keepaliveTicker.C
+	}
 	lastDataAt := time.Now()
 
 	for {
@@ -568,22 +705,44 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 		case ev, ok := <-events:
 			if !ok {
 				// Upstream closed
-				return finalizeStream()
+				return missingTerminalErr()
 			}
 			if ev.err != nil {
 				handleScanErr(ev.err)
-				return finalizeStream()
+				return resultWithUsage(), fmt.Errorf("stream usage incomplete: %w", ev.err)
 			}
 			lastDataAt = time.Now()
 			line := ev.line
-			if !strings.HasPrefix(line, "data: ") || line == "data: [DONE]" {
+			payload, ok := extractOpenAISSEDataLine(line)
+			if !ok {
 				continue
 			}
-			if processDataLine(line[6:]) {
+			if strings.TrimSpace(payload) == "[DONE]" {
-				return resultWithUsage(), nil
+				return missingTerminalErr()
+			}
+			if processDataLine(payload) {
+				return finalizeStream()
 			}
 
-		case <-keepaliveTicker.C:
+		case <-intervalCh:
+			lastRead := time.Unix(0, atomic.LoadInt64(&lastReadAt))
+			if time.Since(lastRead) < streamInterval {
+				continue
+			}
+			if clientDisconnected {
+				return resultWithUsage(), fmt.Errorf("stream usage incomplete after timeout")
+			}
+			logger.L().Warn("openai messages stream: data interval timeout",
+				zap.String("request_id", requestID),
+				zap.String("model", originalModel),
+				zap.Duration("interval", streamInterval),
+			)
+			return resultWithUsage(), fmt.Errorf("stream data interval timeout")
+
+		case <-keepaliveCh:
+			if clientDisconnected {
+				continue
+			}
 			if time.Since(lastDataAt) < keepaliveInterval {
 				continue
 			}
@@ -593,7 +752,8 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 				logger.L().Info("openai messages stream: client disconnected during keepalive",
 					zap.String("request_id", requestID),
 				)
-				return resultWithUsage(), nil
+				clientDisconnected = true
+				continue
 			}
 			c.Writer.Flush()
 		}
@@ -610,3 +770,17 @@ func writeAnthropicError(c *gin.Context, statusCode int, errType, message string
 		},
 	})
 }
+
+func copyOpenAIUsageFromResponsesUsage(usage *apicompat.ResponsesUsage) OpenAIUsage {
+	if usage == nil {
+		return OpenAIUsage{}
+	}
+	result := OpenAIUsage{
+		InputTokens:  usage.InputTokens,
+		OutputTokens: usage.OutputTokens,
+	}
+	if usage.InputTokensDetails != nil {
+		result.CacheReadInputTokens = usage.InputTokensDetails.CachedTokens
+	}
+	return result
+}

backend/internal/service/openai_gateway_service.go

@@ -2601,7 +2601,7 @@ func (s *OpenAIGatewayService) Forward(ctx context.Context, c *gin.Context, acco
 	httpInvalidEncryptedContentRetryTried := false
 	for {
 		// Build upstream request
-		upstreamCtx, releaseUpstreamCtx := detachStreamUpstreamContext(ctx, reqStream)
+		upstreamCtx, releaseUpstreamCtx := detachUpstreamContext(ctx)
 		upstreamReq, err := s.buildUpstreamRequest(upstreamCtx, c, account, body, token, reqStream, promptCacheKey, isCodexCLI)
 		releaseUpstreamCtx()
 		if err != nil {
@@ -2852,7 +2852,7 @@ func (s *OpenAIGatewayService) forwardOpenAIPassthrough(
 		return nil, err
 	}
 
-	upstreamCtx, releaseUpstreamCtx := detachStreamUpstreamContext(ctx, reqStream)
+	upstreamCtx, releaseUpstreamCtx := detachUpstreamContext(ctx)
 	upstreamReq, err := s.buildUpstreamRequestOpenAIPassthrough(upstreamCtx, c, account, body, token)
 	releaseUpstreamCtx()
 	if err != nil {

backend/internal/service/openai_oauth_passthrough_test.go

@@ -307,6 +307,52 @@ func TestOpenAIGatewayService_OAuthPassthrough_CompactUsesJSONAndKeepsNonStreami
 	require.Contains(t, rec.Body.String(), `"id":"cmp_123"`)
 }
 
+func TestOpenAIGatewayService_OAuthPassthrough_UpstreamRequestIgnoresClientCancel(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	reqCtx, cancel := context.WithCancel(context.Background())
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/responses", bytes.NewReader(nil)).WithContext(reqCtx)
+	c.Request.Header.Set("User-Agent", "codex_cli_rs/0.1.0")
+	cancel()
+
+	originalBody := []byte(`{"model":"gpt-5.2","stream":true,"store":true,"instructions":"local-test-instructions","input":[{"type":"text","text":"hi"}]}`)
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_passthrough_ctx"}},
+		Body: io.NopCloser(strings.NewReader(strings.Join([]string{
+			`data: {"type":"response.completed","response":{"usage":{"input_tokens":2,"output_tokens":1}}}`,
+			"",
+			"data: [DONE]",
+			"",
+		}, "\n"))),
+	}}
+
+	svc := &OpenAIGatewayService{
+		cfg:          &config.Config{Gateway: config.GatewayConfig{ForceCodexCLI: false}},
+		httpUpstream: upstream,
+	}
+	account := &Account{
+		ID:             123,
+		Name:           "acc",
+		Platform:       PlatformOpenAI,
+		Type:           AccountTypeOAuth,
+		Concurrency:    1,
+		Credentials:    map[string]any{"access_token": "oauth-token", "chatgpt_account_id": "chatgpt-acc"},
+		Extra:          map[string]any{"openai_passthrough": true, "openai_oauth_responses_websockets_v2_mode": OpenAIWSIngressModeOff},
+		Status:         StatusActive,
+		Schedulable:    true,
+		RateMultiplier: f64p(1),
+	}
+
+	result, err := svc.Forward(reqCtx, c, account, originalBody)
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.NotNil(t, upstream.lastReq)
+	require.NoError(t, upstream.lastReq.Context().Err())
+}
+
 func TestOpenAIGatewayService_OAuthPassthrough_CodexMissingInstructionsRejectedBeforeUpstream(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	logSink, restore := captureStructuredLog(t)
@@ -405,6 +451,52 @@ func TestOpenAIGatewayService_OAuthPassthrough_DisabledUsesLegacyTransform(t *te
 	require.Contains(t, string(upstream.lastBody), `"stream":true`)
 }
 
+func TestOpenAIGatewayService_OAuthLegacy_UpstreamRequestIgnoresClientCancel(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	reqCtx, cancel := context.WithCancel(context.Background())
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/responses", bytes.NewReader(nil)).WithContext(reqCtx)
+	c.Request.Header.Set("User-Agent", "codex_cli_rs/0.1.0")
+	cancel()
+
+	originalBody := []byte(`{"model":"gpt-5.2","stream":false,"store":true,"input":[{"type":"text","text":"hi"}]}`)
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}, "x-request-id": []string{"rid_legacy_ctx"}},
+		Body: io.NopCloser(strings.NewReader(strings.Join([]string{
+			`data: {"type":"response.completed","response":{"usage":{"input_tokens":1,"output_tokens":1}}}`,
+			"",
+			"data: [DONE]",
+			"",
+		}, "\n"))),
+	}}
+
+	svc := &OpenAIGatewayService{
+		cfg:          &config.Config{Gateway: config.GatewayConfig{ForceCodexCLI: false}},
+		httpUpstream: upstream,
+	}
+	account := &Account{
+		ID:             123,
+		Name:           "acc",
+		Platform:       PlatformOpenAI,
+		Type:           AccountTypeOAuth,
+		Concurrency:    1,
+		Credentials:    map[string]any{"access_token": "oauth-token", "chatgpt_account_id": "chatgpt-acc"},
+		Extra:          map[string]any{"openai_passthrough": false, "openai_oauth_responses_websockets_v2_mode": OpenAIWSIngressModeOff},
+		Status:         StatusActive,
+		Schedulable:    true,
+		RateMultiplier: f64p(1),
+	}
+
+	result, err := svc.Forward(reqCtx, c, account, originalBody)
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.NotNil(t, upstream.lastReq)
+	require.NoError(t, upstream.lastReq.Context().Err())
+}
+
 func TestOpenAIGatewayService_OAuthLegacy_CompositeCodexUAUsesCodexOriginator(t *testing.T) {
 	gin.SetMode(gin.TestMode)