fix(流式): 提升SSE稳定性并统一超时配置

- 扩展SSE行长与间隔超时处理，补充keepalive

- 写入失败与超长行时发送错误事件，修复并发释放

- 同步默认配置与示例配置，更新Caddy超时/压缩规则

- 新增OpenAI流式超时与超长行测试

测试: go test ./...

backend/internal/service/antigravity_gateway_service.go

@@ -13,6 +13,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/antigravity"
 	"github.com/gin-gonic/gin"
 	"github.com/google/uuid"
@@ -64,6 +65,7 @@ type AntigravityGatewayService struct {
 	tokenProvider    *AntigravityTokenProvider
 	rateLimitService *RateLimitService
 	httpUpstream     HTTPUpstream
+	cfg              *config.Config
 }
 
 func NewAntigravityGatewayService(
@@ -72,12 +74,14 @@ func NewAntigravityGatewayService(
 	tokenProvider *AntigravityTokenProvider,
 	rateLimitService *RateLimitService,
 	httpUpstream HTTPUpstream,
+	cfg *config.Config,
 ) *AntigravityGatewayService {
 	return &AntigravityGatewayService{
 		accountRepo:      accountRepo,
 		tokenProvider:    tokenProvider,
 		rateLimitService: rateLimitService,
 		httpUpstream:     httpUpstream,
+		cfg:              cfg,
 	}
 }
 
@@ -674,57 +678,147 @@ func (s *AntigravityGatewayService) handleGeminiStreamingResponse(c *gin.Context
 		return nil, errors.New("streaming not supported")
 	}
 
-	reader := bufio.NewReader(resp.Body)
+	// 使用 Scanner 并限制单行大小，避免 ReadString 无上限导致 OOM
+	scanner := bufio.NewScanner(resp.Body)
+	scanner.Buffer(make([]byte, 64*1024), defaultMaxLineSize)
 	usage := &ClaudeUsage{}
 	var firstTokenMs *int
 
+	type scanEvent struct {
+		line string
+		err  error
+	}
+	// 独立 goroutine 读取上游，避免读取阻塞影响超时处理
+	events := make(chan scanEvent, 1)
+	done := make(chan struct{})
+	sendEvent := func(ev scanEvent) bool {
+		select {
+		case events <- ev:
+			return true
+		case <-done:
+			return false
+		}
+	}
+	go func() {
+		defer close(events)
+		for scanner.Scan() {
+			if !sendEvent(scanEvent{line: scanner.Text()}) {
+				return
+			}
+		}
+		if err := scanner.Err(); err != nil {
+			_ = sendEvent(scanEvent{err: err})
+		}
+	}()
+	defer close(done)
+
+	// 上游数据间隔超时保护（防止上游挂起长期占用连接）
+	streamInterval := time.Duration(0)
+	if s.cfg != nil && s.cfg.Gateway.StreamDataIntervalTimeout > 0 {
+		streamInterval = time.Duration(s.cfg.Gateway.StreamDataIntervalTimeout) * time.Second
+	}
+	var intervalTimer *time.Timer
+	if streamInterval > 0 {
+		intervalTimer = time.NewTimer(streamInterval)
+		defer intervalTimer.Stop()
+	}
+	var intervalCh <-chan time.Time
+	if intervalTimer != nil {
+		intervalCh = intervalTimer.C
+	}
+	resetInterval := func() {
+		if intervalTimer == nil {
+			return
+		}
+		if !intervalTimer.Stop() {
+			select {
+			case <-intervalTimer.C:
+			default:
+			}
+		}
+		intervalTimer.Reset(streamInterval)
+	}
+
+	// 仅发送一次错误事件，避免多次写入导致协议混乱
+	errorEventSent := false
+	sendErrorEvent := func(reason string) {
+		if errorEventSent {
+			return
+		}
+		errorEventSent = true
+		_, _ = fmt.Fprintf(c.Writer, "event: error\ndata: {\"error\":\"%s\"}\n\n", reason)
+		flusher.Flush()
+	}
+
 	for {
-		line, err := reader.ReadString('\n')
-		if len(line) > 0 {
+		select {
+		case ev, ok := <-events:
+			if !ok {
+				return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, nil
+			}
+			if ev.err != nil {
+				if errors.Is(ev.err, bufio.ErrTooLong) {
+					log.Printf("SSE line too long (antigravity): max_size=%d error=%v", defaultMaxLineSize, ev.err)
+					sendErrorEvent("response_too_large")
+					return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, ev.err
+				}
+				sendErrorEvent("stream_read_error")
+				return nil, ev.err
+			}
+
+			resetInterval()
+			line := ev.line
 			trimmed := strings.TrimRight(line, "\r\n")
 			if strings.HasPrefix(trimmed, "data:") {
 				payload := strings.TrimSpace(strings.TrimPrefix(trimmed, "data:"))
 				if payload == "" || payload == "[DONE]" {
-					_, _ = io.WriteString(c.Writer, line)
-					flusher.Flush()
-				} else {
-					// 解包 v1internal 响应
-					inner, parseErr := s.unwrapV1InternalResponse([]byte(payload))
-					if parseErr == nil && inner != nil {
-						payload = string(inner)
-					}
-
-					// 解析 usage
-					var parsed map[string]any
-					if json.Unmarshal(inner, &parsed) == nil {
-						if u := extractGeminiUsage(parsed); u != nil {
-							usage = u
-						}
-					}
-
-					if firstTokenMs == nil {
-						ms := int(time.Since(startTime).Milliseconds())
-						firstTokenMs = &ms
-					}
-
-					_, _ = fmt.Fprintf(c.Writer, "data: %s\n\n", payload)
+					if _, err := fmt.Fprintf(c.Writer, "%s\n", line); err != nil {
+						sendErrorEvent("write_failed")
+						return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, err
+					}
 					flusher.Flush()
+					continue
 				}
-			} else {
-				_, _ = io.WriteString(c.Writer, line)
-				flusher.Flush()
-			}
-		}
 
-		if errors.Is(err, io.EOF) {
-			break
-		}
-		if err != nil {
-			return nil, err
+				// 解包 v1internal 响应
+				inner, parseErr := s.unwrapV1InternalResponse([]byte(payload))
+				if parseErr == nil && inner != nil {
+					payload = string(inner)
+				}
+
+				// 解析 usage
+				var parsed map[string]any
+				if json.Unmarshal(inner, &parsed) == nil {
+					if u := extractGeminiUsage(parsed); u != nil {
+						usage = u
+					}
+				}
+
+				if firstTokenMs == nil {
+					ms := int(time.Since(startTime).Milliseconds())
+					firstTokenMs = &ms
+				}
+
+				if _, err := fmt.Fprintf(c.Writer, "data: %s\n\n", payload); err != nil {
+					sendErrorEvent("write_failed")
+					return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, err
+				}
+				flusher.Flush()
+				continue
+			}
+
+			if _, err := fmt.Fprintf(c.Writer, "%s\n", line); err != nil {
+				sendErrorEvent("write_failed")
+				return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, err
+			}
+			flusher.Flush()
+
+		case <-intervalCh:
+			log.Printf("Stream data interval timeout (antigravity)")
+			sendErrorEvent("stream_timeout")
+			return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream data interval timeout")
 		}
 	}
-
-	return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, nil
 }
 
 func (s *AntigravityGatewayService) handleGeminiNonStreamingResponse(c *gin.Context, resp *http.Response) (*ClaudeUsage, error) {
@@ -863,7 +957,9 @@ func (s *AntigravityGatewayService) handleClaudeStreamingResponse(c *gin.Context
 
 	processor := antigravity.NewStreamingProcessor(originalModel)
 	var firstTokenMs *int
-	reader := bufio.NewReader(resp.Body)
+	// 使用 Scanner 并限制单行大小，避免 ReadString 无上限导致 OOM
+	scanner := bufio.NewScanner(resp.Body)
+	scanner.Buffer(make([]byte, 64*1024), defaultMaxLineSize)
 
 	// 辅助函数：转换 antigravity.ClaudeUsage 到 service.ClaudeUsage
 	convertUsage := func(agUsage *antigravity.ClaudeUsage) *ClaudeUsage {
@@ -878,13 +974,95 @@ func (s *AntigravityGatewayService) handleClaudeStreamingResponse(c *gin.Context
 		}
 	}
 
-	for {
-		line, err := reader.ReadString('\n')
-		if err != nil && !errors.Is(err, io.EOF) {
-			return nil, fmt.Errorf("stream read error: %w", err)
+	type scanEvent struct {
+		line string
+		err  error
+	}
+	// 独立 goroutine 读取上游，避免读取阻塞影响超时处理
+	events := make(chan scanEvent, 1)
+	done := make(chan struct{})
+	sendEvent := func(ev scanEvent) bool {
+		select {
+		case events <- ev:
+			return true
+		case <-done:
+			return false
 		}
+	}
+	go func() {
+		defer close(events)
+		for scanner.Scan() {
+			if !sendEvent(scanEvent{line: scanner.Text()}) {
+				return
+			}
+		}
+		if err := scanner.Err(); err != nil {
+			_ = sendEvent(scanEvent{err: err})
+		}
+	}()
+	defer close(done)
 
-		if len(line) > 0 {
+	streamInterval := time.Duration(0)
+	if s.cfg != nil && s.cfg.Gateway.StreamDataIntervalTimeout > 0 {
+		streamInterval = time.Duration(s.cfg.Gateway.StreamDataIntervalTimeout) * time.Second
+	}
+	var intervalTimer *time.Timer
+	if streamInterval > 0 {
+		intervalTimer = time.NewTimer(streamInterval)
+		defer intervalTimer.Stop()
+	}
+	var intervalCh <-chan time.Time
+	if intervalTimer != nil {
+		intervalCh = intervalTimer.C
+	}
+	resetInterval := func() {
+		if intervalTimer == nil {
+			return
+		}
+		if !intervalTimer.Stop() {
+			select {
+			case <-intervalTimer.C:
+			default:
+			}
+		}
+		intervalTimer.Reset(streamInterval)
+	}
+
+	// 仅发送一次错误事件，避免多次写入导致协议混乱
+	errorEventSent := false
+	sendErrorEvent := func(reason string) {
+		if errorEventSent {
+			return
+		}
+		errorEventSent = true
+		_, _ = fmt.Fprintf(c.Writer, "event: error\ndata: {\"error\":\"%s\"}\n\n", reason)
+		flusher.Flush()
+	}
+
+	for {
+		select {
+		case ev, ok := <-events:
+			if !ok {
+				// 发送结束事件
+				finalEvents, agUsage := processor.Finish()
+				if len(finalEvents) > 0 {
+					_, _ = c.Writer.Write(finalEvents)
+					flusher.Flush()
+				}
+				return &antigravityStreamResult{usage: convertUsage(agUsage), firstTokenMs: firstTokenMs}, nil
+			}
+			if ev.err != nil {
+				if errors.Is(ev.err, bufio.ErrTooLong) {
+					log.Printf("SSE line too long (antigravity): max_size=%d error=%v", defaultMaxLineSize, ev.err)
+					sendErrorEvent("response_too_large")
+					return &antigravityStreamResult{usage: convertUsage(nil), firstTokenMs: firstTokenMs}, ev.err
+				}
+				sendErrorEvent("stream_read_error")
+				return nil, fmt.Errorf("stream read error: %w", ev.err)
+			}
+
+			resetInterval()
+			line := ev.line
 			// 处理 SSE 行，转换为 Claude 格式
 			claudeEvents := processor.ProcessLine(strings.TrimRight(line, "\r\n"))
 
@@ -899,23 +1077,17 @@ func (s *AntigravityGatewayService) handleClaudeStreamingResponse(c *gin.Context
 					if len(finalEvents) > 0 {
 						_, _ = c.Writer.Write(finalEvents)
 					}
+					sendErrorEvent("write_failed")
 					return &antigravityStreamResult{usage: convertUsage(agUsage), firstTokenMs: firstTokenMs}, writeErr
 				}
 				flusher.Flush()
 			}
-		}
 
-		if errors.Is(err, io.EOF) {
-			break
+		case <-intervalCh:
+			log.Printf("Stream data interval timeout (antigravity)")
+			sendErrorEvent("stream_timeout")
+			return &antigravityStreamResult{usage: convertUsage(nil), firstTokenMs: firstTokenMs}, fmt.Errorf("stream data interval timeout")
 		}
 	}
 
-	// 发送结束事件
-	finalEvents, agUsage := processor.Finish()
-	if len(finalEvents) > 0 {
-		_, _ = c.Writer.Write(finalEvents)
-		flusher.Flush()
-	}
-
-	return &antigravityStreamResult{usage: convertUsage(agUsage), firstTokenMs: firstTokenMs}, nil
 }

backend/internal/service/gateway_service.go

@@ -32,6 +32,7 @@ const (
 	claudeAPIURL            = "https://api.anthropic.com/v1/messages?beta=true"
 	claudeAPICountTokensURL = "https://api.anthropic.com/v1/messages/count_tokens?beta=true"
 	stickySessionTTL        = time.Hour // 粘性会话TTL
+	defaultMaxLineSize      = 10 * 1024 * 1024
 )
 
 // sseDataRe matches SSE data lines with optional whitespace after colon.
@@ -1448,53 +1449,143 @@ func (s *GatewayService) handleStreamingResponse(ctx context.Context, resp *http
 	var firstTokenMs *int
 	scanner := bufio.NewScanner(resp.Body)
 	// 设置更大的buffer以处理长行
-	scanner.Buffer(make([]byte, 64*1024), 1024*1024)
+	maxLineSize := defaultMaxLineSize
+	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		maxLineSize = s.cfg.Gateway.MaxLineSize
+	}
+	scanner.Buffer(make([]byte, 64*1024), maxLineSize)
+
+	type scanEvent struct {
+		line string
+		err  error
+	}
+	// 独立 goroutine 读取上游，避免读取阻塞导致超时/keepalive无法处理
+	events := make(chan scanEvent, 1)
+	done := make(chan struct{})
+	sendEvent := func(ev scanEvent) bool {
+		select {
+		case events <- ev:
+			return true
+		case <-done:
+			return false
+		}
+	}
+	go func() {
+		defer close(events)
+		for scanner.Scan() {
+			if !sendEvent(scanEvent{line: scanner.Text()}) {
+				return
+			}
+		}
+		if err := scanner.Err(); err != nil {
+			_ = sendEvent(scanEvent{err: err})
+		}
+	}()
+	defer close(done)
+
+	streamInterval := time.Duration(0)
+	if s.cfg != nil && s.cfg.Gateway.StreamDataIntervalTimeout > 0 {
+		streamInterval = time.Duration(s.cfg.Gateway.StreamDataIntervalTimeout) * time.Second
+	}
+	// 仅监控上游数据间隔超时，避免上游挂起占用资源
+	var intervalTimer *time.Timer
+	if streamInterval > 0 {
+		intervalTimer = time.NewTimer(streamInterval)
+		defer intervalTimer.Stop()
+	}
+
+	// 仅发送一次错误事件，避免多次写入导致协议混乱（写失败时尽力通知客户端）
+	errorEventSent := false
+	sendErrorEvent := func(reason string) {
+		if errorEventSent {
+			return
+		}
+		errorEventSent = true
+		_, _ = fmt.Fprintf(w, "event: error\ndata: {\"error\":\"%s\"}\n\n", reason)
+		flusher.Flush()
+	}
 
 	needModelReplace := originalModel != mappedModel
 
-	for scanner.Scan() {
-		line := scanner.Text()
-		if line == "event: error" {
-			return nil, errors.New("have error in stream")
+	for {
+		select {
+		case ev, ok := <-events:
+			if !ok {
+				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, nil
+			}
+			if ev.err != nil {
+				if errors.Is(ev.err, bufio.ErrTooLong) {
+					log.Printf("SSE line too long: account=%d max_size=%d error=%v", account.ID, maxLineSize, ev.err)
+					sendErrorEvent("response_too_large")
+					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, ev.err
+				}
+				sendErrorEvent("stream_read_error")
+				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream read error: %w", ev.err)
+			}
+			line := ev.line
+			if intervalTimer != nil {
+				resetTimer(intervalTimer, streamInterval)
+			}
+			if line == "event: error" {
+				return nil, errors.New("have error in stream")
+			}
+
+			// Extract data from SSE line (supports both "data: " and "data:" formats)
+			if sseDataRe.MatchString(line) {
+				data := sseDataRe.ReplaceAllString(line, "")
+
+				// 如果有模型映射，替换响应中的model字段
+				if needModelReplace {
+					line = s.replaceModelInSSELine(line, mappedModel, originalModel)
+				}
+
+				// 转发行
+				if _, err := fmt.Fprintf(w, "%s\n", line); err != nil {
+					sendErrorEvent("write_failed")
+					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
+				}
+				flusher.Flush()
+
+				// 记录首字时间：第一个有效的 content_block_delta 或 message_start
+				if firstTokenMs == nil && data != "" && data != "[DONE]" {
+					ms := int(time.Since(startTime).Milliseconds())
+					firstTokenMs = &ms
+				}
+				s.parseSSEUsage(data, usage)
+			} else {
+				// 非 data 行直接转发
+				if _, err := fmt.Fprintf(w, "%s\n", line); err != nil {
+					sendErrorEvent("write_failed")
+					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
+				}
+				flusher.Flush()
+			}
+
+		case <-func() <-chan time.Time {
+			if intervalTimer != nil {
+				return intervalTimer.C
+			}
+			return nil
+		}():
+			log.Printf("Stream data interval timeout: account=%d model=%s interval=%s", account.ID, originalModel, streamInterval)
+			sendErrorEvent("stream_timeout")
+			return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream data interval timeout")
 		}
-
-		// Extract data from SSE line (supports both "data: " and "data:" formats)
-		if sseDataRe.MatchString(line) {
-			data := sseDataRe.ReplaceAllString(line, "")
-
-			// 如果有模型映射，替换响应中的model字段
-			if needModelReplace {
-				line = s.replaceModelInSSELine(line, mappedModel, originalModel)
-			}
-
-			// 转发行
-			if _, err := fmt.Fprintf(w, "%s\n", line); err != nil {
-				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
-			}
-			flusher.Flush()
-
-			// 记录首字时间：第一个有效的 content_block_delta 或 message_start
-			if firstTokenMs == nil && data != "" && data != "[DONE]" {
-				ms := int(time.Since(startTime).Milliseconds())
-				firstTokenMs = &ms
-			}
-			s.parseSSEUsage(data, usage)
-		} else {
-			// 非 data 行直接转发
-			if _, err := fmt.Fprintf(w, "%s\n", line); err != nil {
-				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
-			}
-			flusher.Flush()
-		}
-	}
-
-	if err := scanner.Err(); err != nil {
-		return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream read error: %w", err)
 	}
 
 	return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, nil
 }
 
+func resetTimer(timer *time.Timer, interval time.Duration) {
+	if !timer.Stop() {
+		select {
+		case <-timer.C:
+		default:
+		}
+	}
+	timer.Reset(interval)
+}
+
 // replaceModelInSSELine 替换SSE数据行中的model字段
 func (s *GatewayService) replaceModelInSSELine(line, fromModel, toModel string) string {
 	if !sseDataRe.MatchString(line) {

backend/internal/service/openai_gateway_service.go

@@ -775,47 +775,154 @@ func (s *OpenAIGatewayService) handleStreamingResponse(ctx context.Context, resp
 	usage := &OpenAIUsage{}
 	var firstTokenMs *int
 	scanner := bufio.NewScanner(resp.Body)
-	scanner.Buffer(make([]byte, 64*1024), 1024*1024)
+	maxLineSize := defaultMaxLineSize
+	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		maxLineSize = s.cfg.Gateway.MaxLineSize
+	}
+	scanner.Buffer(make([]byte, 64*1024), maxLineSize)
+
+	type scanEvent struct {
+		line string
+		err  error
+	}
+	// 独立 goroutine 读取上游，避免读取阻塞影响 keepalive/超时处理
+	events := make(chan scanEvent, 1)
+	done := make(chan struct{})
+	sendEvent := func(ev scanEvent) bool {
+		select {
+		case events <- ev:
+			return true
+		case <-done:
+			return false
+		}
+	}
+	go func() {
+		defer close(events)
+		for scanner.Scan() {
+			if !sendEvent(scanEvent{line: scanner.Text()}) {
+				return
+			}
+		}
+		if err := scanner.Err(); err != nil {
+			_ = sendEvent(scanEvent{err: err})
+		}
+	}()
+	defer close(done)
+
+	streamInterval := time.Duration(0)
+	if s.cfg != nil && s.cfg.Gateway.StreamDataIntervalTimeout > 0 {
+		streamInterval = time.Duration(s.cfg.Gateway.StreamDataIntervalTimeout) * time.Second
+	}
+	// 仅监控上游数据间隔超时，不被下游 keepalive 影响
+	var intervalTimer *time.Timer
+	if streamInterval > 0 {
+		intervalTimer = time.NewTimer(streamInterval)
+		defer intervalTimer.Stop()
+	}
+	var intervalCh <-chan time.Time
+	if intervalTimer != nil {
+		intervalCh = intervalTimer.C
+	}
+
+	keepaliveInterval := time.Duration(0)
+	if s.cfg != nil && s.cfg.Gateway.StreamKeepaliveInterval > 0 {
+		keepaliveInterval = time.Duration(s.cfg.Gateway.StreamKeepaliveInterval) * time.Second
+	}
+	// 下游 keepalive 仅用于防止代理空闲断开
+	var keepaliveTicker *time.Ticker
+	if keepaliveInterval > 0 {
+		keepaliveTicker = time.NewTicker(keepaliveInterval)
+		defer keepaliveTicker.Stop()
+	}
+	var keepaliveCh <-chan time.Time
+	if keepaliveTicker != nil {
+		keepaliveCh = keepaliveTicker.C
+	}
+	// 记录上次收到上游数据的时间，用于控制 keepalive 发送频率
+	lastDataAt := time.Now()
+
+	// 仅发送一次错误事件，避免多次写入导致协议混乱（写失败时尽力通知客户端）
+	errorEventSent := false
+	sendErrorEvent := func(reason string) {
+		if errorEventSent {
+			return
+		}
+		errorEventSent = true
+		_, _ = fmt.Fprintf(w, "event: error\ndata: {\"error\":\"%s\"}\n\n", reason)
+		flusher.Flush()
+	}
 
 	needModelReplace := originalModel != mappedModel
 
-	for scanner.Scan() {
-		line := scanner.Text()
-
-		// Extract data from SSE line (supports both "data: " and "data:" formats)
-		if openaiSSEDataRe.MatchString(line) {
-			data := openaiSSEDataRe.ReplaceAllString(line, "")
-
-			// Replace model in response if needed
-			if needModelReplace {
-				line = s.replaceModelInSSELine(line, mappedModel, originalModel)
+	for {
+		select {
+		case ev, ok := <-events:
+			if !ok {
+				return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, nil
+			}
+			if ev.err != nil {
+				if errors.Is(ev.err, bufio.ErrTooLong) {
+					log.Printf("SSE line too long: account=%d max_size=%d error=%v", account.ID, maxLineSize, ev.err)
+					sendErrorEvent("response_too_large")
+					return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, ev.err
+				}
+				sendErrorEvent("stream_read_error")
+				return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream read error: %w", ev.err)
 			}
 
-			// Forward line
-			if _, err := fmt.Fprintf(w, "%s\n", line); err != nil {
-				return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
+			line := ev.line
+			lastDataAt = time.Now()
+			if intervalTimer != nil {
+				resetTimer(intervalTimer, streamInterval)
 			}
-			flusher.Flush()
 
-			// Record first token time
-			if firstTokenMs == nil && data != "" && data != "[DONE]" {
-				ms := int(time.Since(startTime).Milliseconds())
-				firstTokenMs = &ms
+			// Extract data from SSE line (supports both "data: " and "data:" formats)
+			if openaiSSEDataRe.MatchString(line) {
+				data := openaiSSEDataRe.ReplaceAllString(line, "")
+
+				// Replace model in response if needed
+				if needModelReplace {
+					line = s.replaceModelInSSELine(line, mappedModel, originalModel)
+				}
+
+				// Forward line
+				if _, err := fmt.Fprintf(w, "%s\n", line); err != nil {
+					sendErrorEvent("write_failed")
+					return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
+				}
+				flusher.Flush()
+
+				// Record first token time
+				if firstTokenMs == nil && data != "" && data != "[DONE]" {
+					ms := int(time.Since(startTime).Milliseconds())
+					firstTokenMs = &ms
+				}
+				s.parseSSEUsage(data, usage)
+			} else {
+				// Forward non-data lines as-is
+				if _, err := fmt.Fprintf(w, "%s\n", line); err != nil {
+					sendErrorEvent("write_failed")
+					return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
+				}
+				flusher.Flush()
 			}
-			s.parseSSEUsage(data, usage)
-		} else {
-			// Forward non-data lines as-is
-			if _, err := fmt.Fprintf(w, "%s\n", line); err != nil {
+
+		case <-intervalCh:
+			log.Printf("Stream data interval timeout: account=%d model=%s interval=%s", account.ID, originalModel, streamInterval)
+			sendErrorEvent("stream_timeout")
+			return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream data interval timeout")
+
+		case <-keepaliveCh:
+			if time.Since(lastDataAt) < keepaliveInterval {
+				continue
+			}
+			if _, err := fmt.Fprint(w, ":\n\n"); err != nil {
 				return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
 			}
 			flusher.Flush()
 		}
 	}
 
-	if err := scanner.Err(); err != nil {
-		return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream read error: %w", err)
-	}
-
 	return &openaiStreamingResult{usage: usage, firstTokenMs: firstTokenMs}, nil
 }
 

backend/internal/service/openai_gateway_service_test.go

@@ -0,0 +1,90 @@
+package service
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/gin-gonic/gin"
+)
+
+func TestOpenAIStreamingTimeout(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	cfg := &config.Config{
+		Gateway: config.GatewayConfig{
+			StreamDataIntervalTimeout: 1,
+			StreamKeepaliveInterval:   0,
+			MaxLineSize:               defaultMaxLineSize,
+		},
+	}
+	svc := &OpenAIGatewayService{cfg: cfg}
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/", nil)
+
+	pr, pw := io.Pipe()
+	resp := &http.Response{
+		StatusCode: http.StatusOK,
+		Body:       pr,
+		Header:     http.Header{},
+	}
+
+	start := time.Now()
+	_, err := svc.handleStreamingResponse(c.Request.Context(), resp, c, &Account{ID: 1}, start, "model", "model")
+	_ = pw.Close()
+	_ = pr.Close()
+
+	if err == nil || !strings.Contains(err.Error(), "stream data interval timeout") {
+		t.Fatalf("expected stream timeout error, got %v", err)
+	}
+	if !strings.Contains(rec.Body.String(), "stream_timeout") {
+		t.Fatalf("expected stream_timeout SSE error, got %q", rec.Body.String())
+	}
+}
+
+func TestOpenAIStreamingTooLong(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	cfg := &config.Config{
+		Gateway: config.GatewayConfig{
+			StreamDataIntervalTimeout: 0,
+			StreamKeepaliveInterval:   0,
+			MaxLineSize:               64 * 1024,
+		},
+	}
+	svc := &OpenAIGatewayService{cfg: cfg}
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/", nil)
+
+	pr, pw := io.Pipe()
+	resp := &http.Response{
+		StatusCode: http.StatusOK,
+		Body:       pr,
+		Header:     http.Header{},
+	}
+
+	go func() {
+		defer pw.Close()
+		// 写入超过 MaxLineSize 的单行数据，触发 ErrTooLong
+		payload := "data: " + strings.Repeat("a", 128*1024) + "\n"
+		_, _ = pw.Write([]byte(payload))
+	}()
+
+	_, err := svc.handleStreamingResponse(c.Request.Context(), resp, c, &Account{ID: 2}, time.Now(), "model", "model")
+	_ = pr.Close()
+
+	if !errors.Is(err, bufio.ErrTooLong) {
+		t.Fatalf("expected ErrTooLong, got %v", err)
+	}
+	if !strings.Contains(rec.Body.String(), "response_too_large") {
+		t.Fatalf("expected response_too_large SSE error, got %q", rec.Body.String())
+	}
+}