feat: detect client disconnect during streaming and continue draining upstream for billing

backend/internal/service/antigravity_gateway_service.go

@@ -1305,6 +1305,7 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 
 	var usage *ClaudeUsage
 	var firstTokenMs *int
+	var clientDisconnect bool
 	if claudeReq.Stream {
 		// 客户端要求流式，直接透传转换
 		streamRes, err := s.handleClaudeStreamingResponse(c, resp, startTime, originalModel)
@@ -1314,6 +1315,7 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 		}
 		usage = streamRes.usage
 		firstTokenMs = streamRes.firstTokenMs
+		clientDisconnect = streamRes.clientDisconnect
 	} else {
 		// 客户端要求非流式，收集流式响应后转换返回
 		streamRes, err := s.handleClaudeStreamToNonStreaming(c, resp, startTime, originalModel)
@@ -1326,12 +1328,13 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 	}
 
 	return &ForwardResult{
-		RequestID:    requestID,
-		Usage:        *usage,
-		Model:        originalModel, // 使用原始模型用于计费和日志
-		Stream:       claudeReq.Stream,
-		Duration:     time.Since(startTime),
-		FirstTokenMs: firstTokenMs,
+		RequestID:        requestID,
+		Usage:            *usage,
+		Model:            originalModel, // 使用原始模型用于计费和日志
+		Stream:           claudeReq.Stream,
+		Duration:         time.Since(startTime),
+		FirstTokenMs:     firstTokenMs,
+		ClientDisconnect: clientDisconnect,
 	}, nil
 }
 
@@ -1860,6 +1863,7 @@ handleSuccess:
 
 	var usage *ClaudeUsage
 	var firstTokenMs *int
+	var clientDisconnect bool
 
 	if stream {
 		// 客户端要求流式，直接透传
@@ -1870,6 +1874,7 @@ handleSuccess:
 		}
 		usage = streamRes.usage
 		firstTokenMs = streamRes.firstTokenMs
+		clientDisconnect = streamRes.clientDisconnect
 	} else {
 		// 客户端要求非流式，收集流式响应后返回
 		streamRes, err := s.handleGeminiStreamToNonStreaming(c, resp, startTime)
@@ -1893,14 +1898,15 @@ handleSuccess:
 	}
 
 	return &ForwardResult{
-		RequestID:    requestID,
-		Usage:        *usage,
-		Model:        originalModel,
-		Stream:       stream,
-		Duration:     time.Since(startTime),
-		FirstTokenMs: firstTokenMs,
-		ImageCount:   imageCount,
-		ImageSize:    imageSize,
+		RequestID:        requestID,
+		Usage:            *usage,
+		Model:            originalModel,
+		Stream:           stream,
+		Duration:         time.Since(startTime),
+		FirstTokenMs:     firstTokenMs,
+		ClientDisconnect: clientDisconnect,
+		ImageCount:       imageCount,
+		ImageSize:        imageSize,
 	}, nil
 }
 
@@ -2319,8 +2325,69 @@ func (s *AntigravityGatewayService) handleUpstreamError(
 }
 
 type antigravityStreamResult struct {
-	usage        *ClaudeUsage
-	firstTokenMs *int
+	usage            *ClaudeUsage
+	firstTokenMs     *int
+	clientDisconnect bool // 客户端是否在流式传输过程中断开
+}
+
+// antigravityClientWriter 封装流式响应的客户端写入，自动检测断开并标记。
+// 断开后所有写入操作变为 no-op，调用方通过 Disconnected() 判断是否继续 drain 上游。
+type antigravityClientWriter struct {
+	w            gin.ResponseWriter
+	flusher      http.Flusher
+	disconnected bool
+	prefix       string // 日志前缀，标识来源方法
+}
+
+func newAntigravityClientWriter(w gin.ResponseWriter, flusher http.Flusher, prefix string) *antigravityClientWriter {
+	return &antigravityClientWriter{w: w, flusher: flusher, prefix: prefix}
+}
+
+// Write 写入数据到客户端，写入失败时标记断开并返回 false
+func (cw *antigravityClientWriter) Write(p []byte) bool {
+	if cw.disconnected {
+		return false
+	}
+	if _, err := cw.w.Write(p); err != nil {
+		cw.markDisconnected()
+		return false
+	}
+	cw.flusher.Flush()
+	return true
+}
+
+// Fprintf 格式化写入数据到客户端，写入失败时标记断开并返回 false
+func (cw *antigravityClientWriter) Fprintf(format string, args ...any) bool {
+	if cw.disconnected {
+		return false
+	}
+	if _, err := fmt.Fprintf(cw.w, format, args...); err != nil {
+		cw.markDisconnected()
+		return false
+	}
+	cw.flusher.Flush()
+	return true
+}
+
+func (cw *antigravityClientWriter) Disconnected() bool { return cw.disconnected }
+
+func (cw *antigravityClientWriter) markDisconnected() {
+	cw.disconnected = true
+	log.Printf("Client disconnected during streaming (%s), continuing to drain upstream for billing", cw.prefix)
+}
+
+// handleStreamReadError 处理上游读取错误的通用逻辑。
+// 返回 (clientDisconnect, handled)：handled=true 表示错误已处理，调用方应返回已收集的 usage。
+func handleStreamReadError(err error, clientDisconnected bool, prefix string) (disconnect bool, handled bool) {
+	if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
+		log.Printf("Context canceled during streaming (%s), returning collected usage", prefix)
+		return true, true
+	}
+	if clientDisconnected {
+		log.Printf("Upstream read error after client disconnect (%s): %v, returning collected usage", prefix, err)
+		return true, true
+	}
+	return false, false
 }
 
 func (s *AntigravityGatewayService) handleGeminiStreamingResponse(c *gin.Context, resp *http.Response, startTime time.Time) (*antigravityStreamResult, error) {
@@ -2396,10 +2463,12 @@ func (s *AntigravityGatewayService) handleGeminiStreamingResponse(c *gin.Context
 		intervalCh = intervalTicker.C
 	}
 
+	cw := newAntigravityClientWriter(c.Writer, flusher, "antigravity gemini")
+
 	// 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 {
+		if errorEventSent || cw.Disconnected() {
 			return
 		}
 		errorEventSent = true
@@ -2411,9 +2480,12 @@ func (s *AntigravityGatewayService) handleGeminiStreamingResponse(c *gin.Context
 		select {
 		case ev, ok := <-events:
 			if !ok {
-				return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, nil
+				return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: cw.Disconnected()}, nil
 			}
 			if ev.err != nil {
+				if disconnect, handled := handleStreamReadError(ev.err, cw.Disconnected(), "antigravity gemini"); handled {
+					return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: disconnect}, nil
+				}
 				if errors.Is(ev.err, bufio.ErrTooLong) {
 					log.Printf("SSE line too long (antigravity): max_size=%d error=%v", maxLineSize, ev.err)
 					sendErrorEvent("response_too_large")
@@ -2428,11 +2500,7 @@ func (s *AntigravityGatewayService) handleGeminiStreamingResponse(c *gin.Context
 			if strings.HasPrefix(trimmed, "data:") {
 				payload := strings.TrimSpace(strings.TrimPrefix(trimmed, "data:"))
 				if payload == "" || payload == "[DONE]" {
-					if _, err := fmt.Fprintf(c.Writer, "%s\n", line); err != nil {
-						sendErrorEvent("write_failed")
-						return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, err
-					}
-					flusher.Flush()
+					cw.Fprintf("%s\n", line)
 					continue
 				}
 
@@ -2468,27 +2536,22 @@ func (s *AntigravityGatewayService) handleGeminiStreamingResponse(c *gin.Context
 					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()
+				cw.Fprintf("data: %s\n\n", payload)
 				continue
 			}
 
-			if _, err := fmt.Fprintf(c.Writer, "%s\n", line); err != nil {
-				sendErrorEvent("write_failed")
-				return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, err
-			}
-			flusher.Flush()
+			cw.Fprintf("%s\n", line)
 
 		case <-intervalCh:
 			lastRead := time.Unix(0, atomic.LoadInt64(&lastReadAt))
 			if time.Since(lastRead) < streamInterval {
 				continue
 			}
+			if cw.Disconnected() {
+				log.Printf("Upstream timeout after client disconnect (antigravity gemini), returning collected usage")
+				return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
+			}
 			log.Printf("Stream data interval timeout (antigravity)")
-			// 注意：此函数没有 account 上下文，无法调用 HandleStreamTimeout
 			sendErrorEvent("stream_timeout")
 			return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream data interval timeout")
 		}
@@ -3186,10 +3249,12 @@ func (s *AntigravityGatewayService) handleClaudeStreamingResponse(c *gin.Context
 		intervalCh = intervalTicker.C
 	}
 
+	cw := newAntigravityClientWriter(c.Writer, flusher, "antigravity claude")
+
 	// 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 {
+		if errorEventSent || cw.Disconnected() {
 			return
 		}
 		errorEventSent = true
@@ -3197,19 +3262,27 @@ func (s *AntigravityGatewayService) handleClaudeStreamingResponse(c *gin.Context
 		flusher.Flush()
 	}
 
+	// finishUsage 是获取 processor 最终 usage 的辅助函数
+	finishUsage := func() *ClaudeUsage {
+		_, agUsage := processor.Finish()
+		return convertUsage(agUsage)
+	}
+
 	for {
 		select {
 		case ev, ok := <-events:
 			if !ok {
-				// 发送结束事件
+				// 上游完成，发送结束事件
 				finalEvents, agUsage := processor.Finish()
 				if len(finalEvents) > 0 {
-					_, _ = c.Writer.Write(finalEvents)
-					flusher.Flush()
+					cw.Write(finalEvents)
 				}
-				return &antigravityStreamResult{usage: convertUsage(agUsage), firstTokenMs: firstTokenMs}, nil
+				return &antigravityStreamResult{usage: convertUsage(agUsage), firstTokenMs: firstTokenMs, clientDisconnect: cw.Disconnected()}, nil
 			}
 			if ev.err != nil {
+				if disconnect, handled := handleStreamReadError(ev.err, cw.Disconnected(), "antigravity claude"); handled {
+					return &antigravityStreamResult{usage: finishUsage(), firstTokenMs: firstTokenMs, clientDisconnect: disconnect}, nil
+				}
 				if errors.Is(ev.err, bufio.ErrTooLong) {
 					log.Printf("SSE line too long (antigravity): max_size=%d error=%v", maxLineSize, ev.err)
 					sendErrorEvent("response_too_large")
@@ -3219,25 +3292,14 @@ func (s *AntigravityGatewayService) handleClaudeStreamingResponse(c *gin.Context
 				return nil, fmt.Errorf("stream read error: %w", ev.err)
 			}
 
-			line := ev.line
 			// 处理 SSE 行，转换为 Claude 格式
-			claudeEvents := processor.ProcessLine(strings.TrimRight(line, "\r\n"))
-
+			claudeEvents := processor.ProcessLine(strings.TrimRight(ev.line, "\r\n"))
 			if len(claudeEvents) > 0 {
 				if firstTokenMs == nil {
 					ms := int(time.Since(startTime).Milliseconds())
 					firstTokenMs = &ms
 				}
-
-				if _, writeErr := c.Writer.Write(claudeEvents); writeErr != nil {
-					finalEvents, agUsage := processor.Finish()
-					if len(finalEvents) > 0 {
-						_, _ = c.Writer.Write(finalEvents)
-					}
-					sendErrorEvent("write_failed")
-					return &antigravityStreamResult{usage: convertUsage(agUsage), firstTokenMs: firstTokenMs}, writeErr
-				}
-				flusher.Flush()
+				cw.Write(claudeEvents)
 			}
 
 		case <-intervalCh:
@@ -3245,13 +3307,15 @@ func (s *AntigravityGatewayService) handleClaudeStreamingResponse(c *gin.Context
 			if time.Since(lastRead) < streamInterval {
 				continue
 			}
+			if cw.Disconnected() {
+				log.Printf("Upstream timeout after client disconnect (antigravity claude), returning collected usage")
+				return &antigravityStreamResult{usage: finishUsage(), firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
+			}
 			log.Printf("Stream data interval timeout (antigravity)")
-			// 注意：此函数没有 account 上下文，无法调用 HandleStreamTimeout
 			sendErrorEvent("stream_timeout")
 			return &antigravityStreamResult{usage: convertUsage(nil), firstTokenMs: firstTokenMs}, fmt.Errorf("stream data interval timeout")
 		}
 	}
-
 }
 
 // extractImageSize 从 Gemini 请求中提取 image_size 参数
@@ -3390,3 +3454,289 @@ func filterEmptyPartsFromGeminiRequest(body []byte) ([]byte, error) {
 	payload["contents"] = filtered
 	return json.Marshal(payload)
 }
+
+// ForwardUpstream 使用 base_url + /v1/messages + 双 header 认证透传上游 Claude 请求
+func (s *AntigravityGatewayService) ForwardUpstream(ctx context.Context, c *gin.Context, account *Account, body []byte) (*ForwardResult, error) {
+	startTime := time.Now()
+	sessionID := getSessionID(c)
+	prefix := logPrefix(sessionID, account.Name)
+
+	// 获取上游配置
+	baseURL := strings.TrimSpace(account.GetCredential("base_url"))
+	apiKey := strings.TrimSpace(account.GetCredential("api_key"))
+	if baseURL == "" || apiKey == "" {
+		return nil, fmt.Errorf("upstream account missing base_url or api_key")
+	}
+	baseURL = strings.TrimSuffix(baseURL, "/")
+
+	// 解析请求获取模型信息
+	var claudeReq antigravity.ClaudeRequest
+	if err := json.Unmarshal(body, &claudeReq); err != nil {
+		return nil, fmt.Errorf("parse claude request: %w", err)
+	}
+	if strings.TrimSpace(claudeReq.Model) == "" {
+		return nil, fmt.Errorf("missing model")
+	}
+	originalModel := claudeReq.Model
+	billingModel := originalModel
+
+	// 构建上游请求 URL
+	upstreamURL := baseURL + "/v1/messages"
+
+	// 创建请求
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, upstreamURL, bytes.NewReader(body))
+	if err != nil {
+		return nil, fmt.Errorf("create upstream request: %w", err)
+	}
+
+	// 设置请求头
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", "Bearer "+apiKey)
+	req.Header.Set("x-api-key", apiKey) // Claude API 兼容
+
+	// 透传 Claude 相关 headers
+	if v := c.GetHeader("anthropic-version"); v != "" {
+		req.Header.Set("anthropic-version", v)
+	}
+	if v := c.GetHeader("anthropic-beta"); v != "" {
+		req.Header.Set("anthropic-beta", v)
+	}
+
+	// 代理 URL
+	proxyURL := ""
+	if account.ProxyID != nil && account.Proxy != nil {
+		proxyURL = account.Proxy.URL()
+	}
+
+	// 发送请求
+	resp, err := s.httpUpstream.Do(req, proxyURL, account.ID, account.Concurrency)
+	if err != nil {
+		log.Printf("%s upstream request failed: %v", prefix, err)
+		return nil, fmt.Errorf("upstream request failed: %w", err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	// 处理错误响应
+	if resp.StatusCode >= 400 {
+		respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
+
+		// 429 错误时标记账号限流
+		if resp.StatusCode == http.StatusTooManyRequests {
+			quotaScope, _ := resolveAntigravityQuotaScope(originalModel)
+			s.handleUpstreamError(ctx, prefix, account, resp.StatusCode, resp.Header, respBody, quotaScope, 0, "", false)
+		}
+
+		// 透传上游错误
+		c.Header("Content-Type", resp.Header.Get("Content-Type"))
+		c.Status(resp.StatusCode)
+		_, _ = c.Writer.Write(respBody)
+
+		return &ForwardResult{
+			Model: billingModel,
+		}, nil
+	}
+
+	// 处理成功响应（流式/非流式）
+	var usage *ClaudeUsage
+	var firstTokenMs *int
+	var clientDisconnect bool
+
+	if claudeReq.Stream {
+		// 流式响应：透传
+		c.Header("Content-Type", "text/event-stream")
+		c.Header("Cache-Control", "no-cache")
+		c.Header("Connection", "keep-alive")
+		c.Header("X-Accel-Buffering", "no")
+		c.Status(http.StatusOK)
+
+		streamRes := s.streamUpstreamResponse(c, resp, startTime)
+		usage = streamRes.usage
+		firstTokenMs = streamRes.firstTokenMs
+		clientDisconnect = streamRes.clientDisconnect
+	} else {
+		// 非流式响应：直接透传
+		respBody, err := io.ReadAll(resp.Body)
+		if err != nil {
+			return nil, fmt.Errorf("read upstream response: %w", err)
+		}
+
+		// 提取 usage
+		usage = s.extractClaudeUsage(respBody)
+
+		c.Header("Content-Type", resp.Header.Get("Content-Type"))
+		c.Status(http.StatusOK)
+		_, _ = c.Writer.Write(respBody)
+	}
+
+	// 构建计费结果
+	duration := time.Since(startTime)
+	log.Printf("%s status=success duration_ms=%d", prefix, duration.Milliseconds())
+
+	return &ForwardResult{
+		Model:            billingModel,
+		Stream:           claudeReq.Stream,
+		Duration:         duration,
+		FirstTokenMs:     firstTokenMs,
+		ClientDisconnect: clientDisconnect,
+		Usage: ClaudeUsage{
+			InputTokens:              usage.InputTokens,
+			OutputTokens:             usage.OutputTokens,
+			CacheReadInputTokens:     usage.CacheReadInputTokens,
+			CacheCreationInputTokens: usage.CacheCreationInputTokens,
+		},
+	}, nil
+}
+
+// streamUpstreamResponse 透传上游 SSE 流并提取 Claude usage
+func (s *AntigravityGatewayService) streamUpstreamResponse(c *gin.Context, resp *http.Response, startTime time.Time) *antigravityStreamResult {
+	usage := &ClaudeUsage{}
+	var firstTokenMs *int
+
+	scanner := bufio.NewScanner(resp.Body)
+	maxLineSize := defaultMaxLineSize
+	if s.settingService.cfg != nil && s.settingService.cfg.Gateway.MaxLineSize > 0 {
+		maxLineSize = s.settingService.cfg.Gateway.MaxLineSize
+	}
+	scanner.Buffer(make([]byte, 64*1024), maxLineSize)
+
+	type scanEvent struct {
+		line string
+		err  error
+	}
+	events := make(chan scanEvent, 16)
+	done := make(chan struct{})
+	sendEvent := func(ev scanEvent) bool {
+		select {
+		case events <- ev:
+			return true
+		case <-done:
+			return false
+		}
+	}
+	var lastReadAt int64
+	atomic.StoreInt64(&lastReadAt, time.Now().UnixNano())
+	go func() {
+		defer close(events)
+		for scanner.Scan() {
+			atomic.StoreInt64(&lastReadAt, time.Now().UnixNano())
+			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.settingService.cfg != nil && s.settingService.cfg.Gateway.StreamDataIntervalTimeout > 0 {
+		streamInterval = time.Duration(s.settingService.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
+	}
+
+	flusher, _ := c.Writer.(http.Flusher)
+	cw := newAntigravityClientWriter(c.Writer, flusher, "antigravity upstream")
+
+	for {
+		select {
+		case ev, ok := <-events:
+			if !ok {
+				return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: cw.Disconnected()}
+			}
+			if ev.err != nil {
+				if disconnect, handled := handleStreamReadError(ev.err, cw.Disconnected(), "antigravity upstream"); handled {
+					return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: disconnect}
+				}
+				log.Printf("Stream read error (antigravity upstream): %v", ev.err)
+				return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}
+			}
+
+			line := ev.line
+
+			// 记录首 token 时间
+			if firstTokenMs == nil && len(line) > 0 {
+				ms := int(time.Since(startTime).Milliseconds())
+				firstTokenMs = &ms
+			}
+
+			// 尝试从 message_delta 或 message_stop 事件提取 usage
+			s.extractSSEUsage(line, usage)
+
+			// 透传行
+			cw.Fprintf("%s\n", line)
+
+		case <-intervalCh:
+			lastRead := time.Unix(0, atomic.LoadInt64(&lastReadAt))
+			if time.Since(lastRead) < streamInterval {
+				continue
+			}
+			if cw.Disconnected() {
+				log.Printf("Upstream timeout after client disconnect (antigravity upstream), returning collected usage")
+				return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}
+			}
+			log.Printf("Stream data interval timeout (antigravity upstream)")
+			return &antigravityStreamResult{usage: usage, firstTokenMs: firstTokenMs}
+		}
+	}
+}
+
+// extractSSEUsage 从 SSE data 行中提取 Claude usage（用于流式透传场景）
+func (s *AntigravityGatewayService) extractSSEUsage(line string, usage *ClaudeUsage) {
+	if !strings.HasPrefix(line, "data: ") {
+		return
+	}
+	dataStr := strings.TrimPrefix(line, "data: ")
+	var event map[string]any
+	if json.Unmarshal([]byte(dataStr), &event) != nil {
+		return
+	}
+	u, ok := event["usage"].(map[string]any)
+	if !ok {
+		return
+	}
+	if v, ok := u["input_tokens"].(float64); ok && int(v) > 0 {
+		usage.InputTokens = int(v)
+	}
+	if v, ok := u["output_tokens"].(float64); ok && int(v) > 0 {
+		usage.OutputTokens = int(v)
+	}
+	if v, ok := u["cache_read_input_tokens"].(float64); ok && int(v) > 0 {
+		usage.CacheReadInputTokens = int(v)
+	}
+	if v, ok := u["cache_creation_input_tokens"].(float64); ok && int(v) > 0 {
+		usage.CacheCreationInputTokens = int(v)
+	}
+}
+
+// extractClaudeUsage 从非流式 Claude 响应提取 usage
+func (s *AntigravityGatewayService) extractClaudeUsage(body []byte) *ClaudeUsage {
+	usage := &ClaudeUsage{}
+	var resp map[string]any
+	if json.Unmarshal(body, &resp) != nil {
+		return usage
+	}
+	if u, ok := resp["usage"].(map[string]any); ok {
+		if v, ok := u["input_tokens"].(float64); ok {
+			usage.InputTokens = int(v)
+		}
+		if v, ok := u["output_tokens"].(float64); ok {
+			usage.OutputTokens = int(v)
+		}
+		if v, ok := u["cache_read_input_tokens"].(float64); ok {
+			usage.CacheReadInputTokens = int(v)
+		}
+		if v, ok := u["cache_creation_input_tokens"].(float64); ok {
+			usage.CacheCreationInputTokens = int(v)
+		}
+	}
+	return usage
+}

backend/internal/service/antigravity_gateway_service_test.go

@@ -4,17 +4,42 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
+	"fmt"
 	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
 	"time"
 
+	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/antigravity"
 	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/require"
 )
 
+// antigravityFailingWriter 模拟客户端断开连接的 gin.ResponseWriter
+type antigravityFailingWriter struct {
+	gin.ResponseWriter
+	failAfter int // 允许成功写入的次数，之后所有写入返回错误
+	writes    int
+}
+
+func (w *antigravityFailingWriter) 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)
+}
+
+// newAntigravityTestService 创建用于流式测试的 AntigravityGatewayService
+func newAntigravityTestService(cfg *config.Config) *AntigravityGatewayService {
+	return &AntigravityGatewayService{
+		settingService: &SettingService{cfg: cfg},
+	}
+}
+
 func TestStripSignatureSensitiveBlocksFromClaudeRequest(t *testing.T) {
 	req := &antigravity.ClaudeRequest{
 		Model: "claude-sonnet-4-5",
@@ -337,8 +362,8 @@ func TestAntigravityGatewayService_Forward_StickySessionForceCacheBilling(t *tes
 	require.True(t, failoverErr.ForceCacheBilling, "ForceCacheBilling should be true for sticky session switch")
 }
 
-// TestAntigravityGatewayService_ForwardGemini_StickySessionForceCacheBilling
-// 验证：ForwardGemini 粘性会话切换时，UpstreamFailoverError.ForceCacheBilling 应为 true
+// TestAntigravityGatewayService_ForwardGemini_StickySessionForceCacheBilling verifies
+// that ForwardGemini sets ForceCacheBilling=true for sticky session switch.
 func TestAntigravityGatewayService_ForwardGemini_StickySessionForceCacheBilling(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	writer := httptest.NewRecorder()
@@ -391,3 +416,438 @@ func TestAntigravityGatewayService_ForwardGemini_StickySessionForceCacheBilling(
 	require.Equal(t, http.StatusServiceUnavailable, failoverErr.StatusCode)
 	require.True(t, failoverErr.ForceCacheBilling, "ForceCacheBilling should be true for sticky session switch")
 }
+
+// --- 流式 happy path 测试 ---
+
+// TestStreamUpstreamResponse_NormalComplete
+// 验证：正常流式转发完成时，数据正确透传、usage 正确收集、clientDisconnect=false
+func TestStreamUpstreamResponse_NormalComplete(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize},
+	})
+
+	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 func() { _ = pw.Close() }()
+		fmt.Fprintln(pw, `event: message_start`)
+		fmt.Fprintln(pw, `data: {"type":"message_start","message":{"usage":{"input_tokens":10}}}`)
+		fmt.Fprintln(pw, "")
+		fmt.Fprintln(pw, `event: content_block_delta`)
+		fmt.Fprintln(pw, `data: {"type":"content_block_delta","delta":{"text":"hello"}}`)
+		fmt.Fprintln(pw, "")
+		fmt.Fprintln(pw, `event: message_delta`)
+		fmt.Fprintln(pw, `data: {"type":"message_delta","usage":{"output_tokens":5}}`)
+		fmt.Fprintln(pw, "")
+	}()
+
+	result := svc.streamUpstreamResponse(c, resp, time.Now())
+	_ = pr.Close()
+
+	require.NotNil(t, result)
+	require.False(t, result.clientDisconnect, "normal completion should not set clientDisconnect")
+	require.NotNil(t, result.usage)
+	require.Equal(t, 5, result.usage.OutputTokens, "should collect output_tokens from message_delta")
+	require.NotNil(t, result.firstTokenMs, "should record first token time")
+
+	// 验证数据被透传到客户端
+	body := rec.Body.String()
+	require.Contains(t, body, "event: message_start")
+	require.Contains(t, body, "content_block_delta")
+	require.Contains(t, body, "message_delta")
+}
+
+// TestHandleGeminiStreamingResponse_NormalComplete
+// 验证：正常 Gemini 流式转发，数据正确透传、usage 正确收集
+func TestHandleGeminiStreamingResponse_NormalComplete(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize},
+	})
+
+	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 func() { _ = pw.Close() }()
+		// 第一个 chunk（部分内容）
+		fmt.Fprintln(pw, `data: {"candidates":[{"content":{"parts":[{"text":"Hello"}]}}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":3}}`)
+		fmt.Fprintln(pw, "")
+		// 第二个 chunk（最终内容+完整 usage）
+		fmt.Fprintln(pw, `data: {"candidates":[{"content":{"parts":[{"text":" world"}]},"finishReason":"STOP"}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":8,"cachedContentTokenCount":2}}`)
+		fmt.Fprintln(pw, "")
+	}()
+
+	result, err := svc.handleGeminiStreamingResponse(c, resp, time.Now())
+	_ = pr.Close()
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.False(t, result.clientDisconnect, "normal completion should not set clientDisconnect")
+	require.NotNil(t, result.usage)
+	// Gemini usage: promptTokenCount=10, candidatesTokenCount=8, cachedContentTokenCount=2
+	// → InputTokens=10-2=8, OutputTokens=8, CacheReadInputTokens=2
+	require.Equal(t, 8, result.usage.InputTokens)
+	require.Equal(t, 8, result.usage.OutputTokens)
+	require.Equal(t, 2, result.usage.CacheReadInputTokens)
+	require.NotNil(t, result.firstTokenMs, "should record first token time")
+
+	// 验证数据被透传到客户端
+	body := rec.Body.String()
+	require.Contains(t, body, "Hello")
+	require.Contains(t, body, "world")
+	// 不应包含错误事件
+	require.NotContains(t, body, "event: error")
+}
+
+// TestHandleClaudeStreamingResponse_NormalComplete
+// 验证：正常 Claude 流式转发（Gemini→Claude 转换），数据正确转换并输出
+func TestHandleClaudeStreamingResponse_NormalComplete(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize},
+	})
+
+	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 func() { _ = pw.Close() }()
+		// v1internal 包装格式：Gemini 数据嵌套在 "response" 字段下
+		// ProcessLine 先尝试反序列化为 V1InternalResponse，裸格式会导致 Response.UsageMetadata 为空
+		fmt.Fprintln(pw, `data: {"response":{"candidates":[{"content":{"parts":[{"text":"Hi there"}]},"finishReason":"STOP"}],"usageMetadata":{"promptTokenCount":5,"candidatesTokenCount":3}}}`)
+		fmt.Fprintln(pw, "")
+	}()
+
+	result, err := svc.handleClaudeStreamingResponse(c, resp, time.Now(), "claude-sonnet-4-5")
+	_ = pr.Close()
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.False(t, result.clientDisconnect, "normal completion should not set clientDisconnect")
+	require.NotNil(t, result.usage)
+	// Gemini→Claude 转换的 usage：promptTokenCount=5→InputTokens=5, candidatesTokenCount=3→OutputTokens=3
+	require.Equal(t, 5, result.usage.InputTokens)
+	require.Equal(t, 3, result.usage.OutputTokens)
+	require.NotNil(t, result.firstTokenMs, "should record first token time")
+
+	// 验证输出是 Claude SSE 格式（processor 会转换）
+	body := rec.Body.String()
+	require.Contains(t, body, "event: message_start", "should contain Claude message_start event")
+	require.Contains(t, body, "event: message_stop", "should contain Claude message_stop event")
+	// 不应包含错误事件
+	require.NotContains(t, body, "event: error")
+}
+
+// --- 流式客户端断开检测测试 ---
+
+// TestStreamUpstreamResponse_ClientDisconnectDrainsUsage
+// 验证：客户端写入失败后，streamUpstreamResponse 继续读取上游以收集 usage
+func TestStreamUpstreamResponse_ClientDisconnectDrainsUsage(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize},
+	})
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/", nil)
+	c.Writer = &antigravityFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+
+	pr, pw := io.Pipe()
+	resp := &http.Response{StatusCode: http.StatusOK, Body: pr, Header: http.Header{}}
+
+	go func() {
+		defer func() { _ = pw.Close() }()
+		fmt.Fprintln(pw, `event: message_start`)
+		fmt.Fprintln(pw, `data: {"type":"message_start","message":{"usage":{"input_tokens":10}}}`)
+		fmt.Fprintln(pw, "")
+		fmt.Fprintln(pw, `event: message_delta`)
+		fmt.Fprintln(pw, `data: {"type":"message_delta","usage":{"output_tokens":20}}`)
+		fmt.Fprintln(pw, "")
+	}()
+
+	result := svc.streamUpstreamResponse(c, resp, time.Now())
+	_ = pr.Close()
+
+	require.NotNil(t, result)
+	require.True(t, result.clientDisconnect)
+	require.NotNil(t, result.usage)
+	require.Equal(t, 20, result.usage.OutputTokens)
+}
+
+// TestStreamUpstreamResponse_ContextCanceled
+// 验证：context 取消时返回 usage 且标记 clientDisconnect
+func TestStreamUpstreamResponse_ContextCanceled(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize},
+	})
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	c.Request = httptest.NewRequest(http.MethodPost, "/", nil).WithContext(ctx)
+
+	resp := &http.Response{StatusCode: http.StatusOK, Body: cancelReadCloser{}, Header: http.Header{}}
+
+	result := svc.streamUpstreamResponse(c, resp, time.Now())
+
+	require.NotNil(t, result)
+	require.True(t, result.clientDisconnect)
+	require.NotContains(t, rec.Body.String(), "event: error")
+}
+
+// TestStreamUpstreamResponse_Timeout
+// 验证：上游超时时返回已收集的 usage
+func TestStreamUpstreamResponse_Timeout(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{StreamDataIntervalTimeout: 1, MaxLineSize: defaultMaxLineSize},
+	})
+
+	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{}}
+
+	result := svc.streamUpstreamResponse(c, resp, time.Now())
+	_ = pw.Close()
+	_ = pr.Close()
+
+	require.NotNil(t, result)
+	require.False(t, result.clientDisconnect)
+}
+
+// TestStreamUpstreamResponse_TimeoutAfterClientDisconnect
+// 验证：客户端断开后上游超时，返回 usage 并标记 clientDisconnect
+func TestStreamUpstreamResponse_TimeoutAfterClientDisconnect(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{StreamDataIntervalTimeout: 1, MaxLineSize: defaultMaxLineSize},
+	})
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/", nil)
+	c.Writer = &antigravityFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+
+	pr, pw := io.Pipe()
+	resp := &http.Response{StatusCode: http.StatusOK, Body: pr, Header: http.Header{}}
+
+	go func() {
+		fmt.Fprintln(pw, `data: {"type":"message_start","message":{"usage":{"input_tokens":5}}}`)
+		fmt.Fprintln(pw, "")
+		// 不关闭 pw → 等待超时
+	}()
+
+	result := svc.streamUpstreamResponse(c, resp, time.Now())
+	_ = pw.Close()
+	_ = pr.Close()
+
+	require.NotNil(t, result)
+	require.True(t, result.clientDisconnect)
+}
+
+// TestHandleGeminiStreamingResponse_ClientDisconnect
+// 验证：Gemini 流式转发中客户端断开后继续 drain 上游
+func TestHandleGeminiStreamingResponse_ClientDisconnect(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize},
+	})
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/", nil)
+	c.Writer = &antigravityFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+
+	pr, pw := io.Pipe()
+	resp := &http.Response{StatusCode: http.StatusOK, Body: pr, Header: http.Header{}}
+
+	go func() {
+		defer func() { _ = pw.Close() }()
+		fmt.Fprintln(pw, `data: {"candidates":[{"content":{"parts":[{"text":"hi"}]}}],"usageMetadata":{"promptTokenCount":5,"candidatesTokenCount":10}}`)
+		fmt.Fprintln(pw, "")
+	}()
+
+	result, err := svc.handleGeminiStreamingResponse(c, resp, time.Now())
+	_ = pr.Close()
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.True(t, result.clientDisconnect)
+	require.NotContains(t, rec.Body.String(), "write_failed")
+}
+
+// TestHandleGeminiStreamingResponse_ContextCanceled
+// 验证：context 取消时不注入错误事件
+func TestHandleGeminiStreamingResponse_ContextCanceled(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize},
+	})
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	c.Request = httptest.NewRequest(http.MethodPost, "/", nil).WithContext(ctx)
+
+	resp := &http.Response{StatusCode: http.StatusOK, Body: cancelReadCloser{}, Header: http.Header{}}
+
+	result, err := svc.handleGeminiStreamingResponse(c, resp, time.Now())
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.True(t, result.clientDisconnect)
+	require.NotContains(t, rec.Body.String(), "event: error")
+}
+
+// TestHandleClaudeStreamingResponse_ClientDisconnect
+// 验证：Claude 流式转发中客户端断开后继续 drain 上游
+func TestHandleClaudeStreamingResponse_ClientDisconnect(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize},
+	})
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/", nil)
+	c.Writer = &antigravityFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+
+	pr, pw := io.Pipe()
+	resp := &http.Response{StatusCode: http.StatusOK, Body: pr, Header: http.Header{}}
+
+	go func() {
+		defer func() { _ = pw.Close() }()
+		// v1internal 包装格式
+		fmt.Fprintln(pw, `data: {"response":{"candidates":[{"content":{"parts":[{"text":"hello"}]},"finishReason":"STOP"}],"usageMetadata":{"promptTokenCount":8,"candidatesTokenCount":15}}}`)
+		fmt.Fprintln(pw, "")
+	}()
+
+	result, err := svc.handleClaudeStreamingResponse(c, resp, time.Now(), "claude-sonnet-4-5")
+	_ = pr.Close()
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.True(t, result.clientDisconnect)
+}
+
+// TestHandleClaudeStreamingResponse_ContextCanceled
+// 验证：context 取消时不注入错误事件
+func TestHandleClaudeStreamingResponse_ContextCanceled(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	svc := newAntigravityTestService(&config.Config{
+		Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize},
+	})
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	c.Request = httptest.NewRequest(http.MethodPost, "/", nil).WithContext(ctx)
+
+	resp := &http.Response{StatusCode: http.StatusOK, Body: cancelReadCloser{}, Header: http.Header{}}
+
+	result, err := svc.handleClaudeStreamingResponse(c, resp, time.Now(), "claude-sonnet-4-5")
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.True(t, result.clientDisconnect)
+	require.NotContains(t, rec.Body.String(), "event: error")
+}
+
+// TestExtractSSEUsage 验证 extractSSEUsage 从 SSE data 行正确提取 usage
+func TestExtractSSEUsage(t *testing.T) {
+	svc := &AntigravityGatewayService{}
+	tests := []struct {
+		name     string
+		line     string
+		expected ClaudeUsage
+	}{
+		{
+			name:     "message_delta with output_tokens",
+			line:     `data: {"type":"message_delta","usage":{"output_tokens":42}}`,
+			expected: ClaudeUsage{OutputTokens: 42},
+		},
+		{
+			name:     "non-data line ignored",
+			line:     `event: message_start`,
+			expected: ClaudeUsage{},
+		},
+		{
+			name:     "top-level usage with all fields",
+			line:     `data: {"usage":{"input_tokens":10,"output_tokens":20,"cache_read_input_tokens":5,"cache_creation_input_tokens":3}}`,
+			expected: ClaudeUsage{InputTokens: 10, OutputTokens: 20, CacheReadInputTokens: 5, CacheCreationInputTokens: 3},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			usage := &ClaudeUsage{}
+			svc.extractSSEUsage(tt.line, usage)
+			require.Equal(t, tt.expected, *usage)
+		})
+	}
+}
+
+// TestAntigravityClientWriter 验证 antigravityClientWriter 的断开检测
+func TestAntigravityClientWriter(t *testing.T) {
+	t.Run("normal write succeeds", func(t *testing.T) {
+		gin.SetMode(gin.TestMode)
+		rec := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(rec)
+		flusher, _ := c.Writer.(http.Flusher)
+		cw := newAntigravityClientWriter(c.Writer, flusher, "test")
+
+		ok := cw.Write([]byte("hello"))
+		require.True(t, ok)
+		require.False(t, cw.Disconnected())
+		require.Contains(t, rec.Body.String(), "hello")
+	})
+
+	t.Run("write failure marks disconnected", func(t *testing.T) {
+		gin.SetMode(gin.TestMode)
+		rec := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(rec)
+		fw := &antigravityFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+		flusher, _ := c.Writer.(http.Flusher)
+		cw := newAntigravityClientWriter(fw, flusher, "test")
+
+		ok := cw.Write([]byte("hello"))
+		require.False(t, ok)
+		require.True(t, cw.Disconnected())
+	})
+
+	t.Run("subsequent writes are no-op", func(t *testing.T) {
+		gin.SetMode(gin.TestMode)
+		rec := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(rec)
+		fw := &antigravityFailingWriter{ResponseWriter: c.Writer, failAfter: 0}
+		flusher, _ := c.Writer.(http.Flusher)
+		cw := newAntigravityClientWriter(fw, flusher, "test")
+
+		cw.Write([]byte("first"))
+		ok := cw.Fprintf("second %d", 2)
+		require.False(t, ok)
+		require.True(t, cw.Disconnected())
+	})
+}