fix(security): 强化 usage 端点信息暴露控制

检测 context.Canceled 作为客户端断开信号，返回已收集的 usage 而非错误

backend/internal/handler/admin/usage_handler.go

@@ -144,7 +144,7 @@ func (h *UsageHandler) List(c *gin.Context) {
 
 	out := make([]dto.UsageLog, 0, len(records))
 	for i := range records {
-		out = append(out, *dto.UsageLogFromService(&records[i]))
+		out = append(out, *dto.UsageLogFromServiceAdmin(&records[i]))
 	}
 	response.Paginated(c, out, result.Total, page, pageSize)
 }

backend/internal/handler/dto/mappers.go

@@ -234,7 +234,21 @@ func RedeemCodeFromService(rc *service.RedeemCode) *RedeemCode {
 	}
 }
 
-func UsageLogFromService(l *service.UsageLog) *UsageLog {
+// AccountSummaryFromService returns a minimal AccountSummary for usage log display.
+// Only includes ID and Name - no sensitive fields like Credentials, Proxy, etc.
+func AccountSummaryFromService(a *service.Account) *AccountSummary {
+	if a == nil {
+		return nil
+	}
+	return &AccountSummary{
+		ID:   a.ID,
+		Name: a.Name,
+	}
+}
+
+// usageLogFromServiceBase is a helper that converts service UsageLog to DTO.
+// The account parameter allows caller to control what Account info is included.
+func usageLogFromServiceBase(l *service.UsageLog, account *AccountSummary) *UsageLog {
 	if l == nil {
 		return nil
 	}
@@ -269,12 +283,27 @@ func UsageLogFromService(l *service.UsageLog) *UsageLog {
 		CreatedAt:             l.CreatedAt,
 		User:                  UserFromServiceShallow(l.User),
 		APIKey:                APIKeyFromService(l.APIKey),
-		Account:               AccountFromService(l.Account),
+		Account:               account,
 		Group:                 GroupFromServiceShallow(l.Group),
 		Subscription:          UserSubscriptionFromService(l.Subscription),
 	}
 }
 
+// UsageLogFromService converts a service UsageLog to DTO for regular users.
+// It excludes Account details - users should not see account information.
+func UsageLogFromService(l *service.UsageLog) *UsageLog {
+	return usageLogFromServiceBase(l, nil)
+}
+
+// UsageLogFromServiceAdmin converts a service UsageLog to DTO for admin users.
+// It includes minimal Account info (ID, Name only).
+func UsageLogFromServiceAdmin(l *service.UsageLog) *UsageLog {
+	if l == nil {
+		return nil
+	}
+	return usageLogFromServiceBase(l, AccountSummaryFromService(l.Account))
+}
+
 func SettingFromService(s *service.Setting) *Setting {
 	if s == nil {
 		return nil

backend/internal/handler/dto/types.go

@@ -184,11 +184,18 @@ type UsageLog struct {
 
 	User         *User             `json:"user,omitempty"`
 	APIKey       *APIKey           `json:"api_key,omitempty"`
-	Account      *Account          `json:"account,omitempty"`
+	Account      *AccountSummary   `json:"account,omitempty"` // Use minimal AccountSummary to prevent data leakage
 	Group        *Group            `json:"group,omitempty"`
 	Subscription *UserSubscription `json:"subscription,omitempty"`
 }
 
+// AccountSummary is a minimal account info for usage log display.
+// It intentionally excludes sensitive fields like Credentials, Proxy, etc.
+type AccountSummary struct {
+	ID   int64  `json:"id"`
+	Name string `json:"name"`
+}
+
 type Setting struct {
 	ID        int64     `json:"id"`
 	Key       string    `json:"key"`

backend/internal/pkg/antigravity/client.go

@@ -13,16 +13,48 @@ import (
 	"time"
 )
 
+// resolveHost 从 URL 解析 host
+func resolveHost(urlStr string) string {
+	parsed, err := url.Parse(urlStr)
+	if err != nil {
+		return ""
+	}
+	return parsed.Host
+}
+
 // NewAPIRequest 创建 Antigravity API 请求（v1internal 端点）
 func NewAPIRequest(ctx context.Context, action, accessToken string, body []byte) (*http.Request, error) {
+	// 构建 URL，流式请求添加 ?alt=sse 参数
 	apiURL := fmt.Sprintf("%s/v1internal:%s", BaseURL, action)
+	isStream := action == "streamGenerateContent"
+	if isStream {
+		apiURL += "?alt=sse"
+	}
+
 	req, err := http.NewRequestWithContext(ctx, http.MethodPost, apiURL, bytes.NewReader(body))
 	if err != nil {
 		return nil, err
 	}
+
+	// 基础 Headers
 	req.Header.Set("Content-Type", "application/json")
 	req.Header.Set("Authorization", "Bearer "+accessToken)
 	req.Header.Set("User-Agent", UserAgent)
+
+	// Accept Header 根据请求类型设置
+	if isStream {
+		req.Header.Set("Accept", "text/event-stream")
+	} else {
+		req.Header.Set("Accept", "application/json")
+	}
+
+	// 显式设置 Host Header
+	if host := resolveHost(apiURL); host != "" {
+		req.Host = host
+	}
+
+	// 注意：requestType 已在 JSON body 的 V1InternalRequest 中设置，不需要 HTTP Header
+
 	return req, nil
 }
 

backend/internal/pkg/antigravity/oauth.go

@@ -33,10 +33,11 @@ const (
 		"https://www.googleapis.com/auth/experimentsandconfigs"
 
 	// API 端点
-	BaseURL = "https://cloudcode-pa.googleapis.com"
+	// 优先使用 sandbox daily URL，配额更宽松
+	BaseURL = "https://daily-cloudcode-pa.sandbox.googleapis.com"
 
-	// User-Agent
-	UserAgent = "antigravity/1.11.9 windows/amd64"
+	// User-Agent（模拟官方客户端）
+	UserAgent = "antigravity/1.104.0 darwin/arm64"
 
 	// Session 过期时间
 	SessionTTL = 30 * time.Minute

backend/internal/pkg/antigravity/request_transformer.go

@@ -1,17 +1,46 @@
 package antigravity
 
 import (
+	"crypto/sha256"
+	"encoding/binary"
 	"encoding/json"
 	"fmt"
 	"log"
+	"math/rand"
 	"os"
+	"strconv"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/gin-gonic/gin"
 	"github.com/google/uuid"
 )
 
+var (
+	sessionRand      = rand.New(rand.NewSource(time.Now().UnixNano()))
+	sessionRandMutex sync.Mutex
+)
+
+// generateStableSessionID 基于用户消息内容生成稳定的 session ID
+func generateStableSessionID(contents []GeminiContent) string {
+	// 查找第一个 user 消息的文本
+	for _, content := range contents {
+		if content.Role == "user" && len(content.Parts) > 0 {
+			if text := content.Parts[0].Text; text != "" {
+				h := sha256.Sum256([]byte(text))
+				n := int64(binary.BigEndian.Uint64(h[:8])) & 0x7FFFFFFFFFFFFFFF
+				return "-" + strconv.FormatInt(n, 10)
+			}
+		}
+	}
+	// 回退：生成随机 session ID
+	sessionRandMutex.Lock()
+	n := sessionRand.Int63n(9_000_000_000_000_000_000)
+	sessionRandMutex.Unlock()
+	return "-" + strconv.FormatInt(n, 10)
+}
+
 type TransformOptions struct {
 	EnableIdentityPatch bool
 	// IdentityPatch 可选：自定义注入到 systemInstruction 开头的身份防护提示词；
@@ -67,8 +96,15 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 
 	// 5. 构建内部请求
 	innerRequest := GeminiRequest{
-		Contents:       contents,
-		SafetySettings: DefaultSafetySettings,
+		Contents: contents,
+		// 总是设置 toolConfig，与官方客户端一致
+		ToolConfig: &GeminiToolConfig{
+			FunctionCallingConfig: &GeminiFunctionCallingConfig{
+				Mode: "VALIDATED",
+			},
+		},
+		// 总是生成 sessionId，基于用户消息内容
+		SessionID: generateStableSessionID(contents),
 	}
 
 	if systemInstruction != nil {
@@ -79,14 +115,9 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 	}
 	if len(tools) > 0 {
 		innerRequest.Tools = tools
-		innerRequest.ToolConfig = &GeminiToolConfig{
-			FunctionCallingConfig: &GeminiFunctionCallingConfig{
-				Mode: "VALIDATED",
-			},
-		}
 	}
 
-	// 如果提供了 metadata.user_id，复用为 sessionId
+	// 如果提供了 metadata.user_id，优先使用
 	if claudeReq.Metadata != nil && claudeReq.Metadata.UserID != "" {
 		innerRequest.SessionID = claudeReq.Metadata.UserID
 	}
@@ -95,7 +126,7 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 	v1Req := V1InternalRequest{
 		Project:     projectID,
 		RequestID:   "agent-" + uuid.New().String(),
-		UserAgent:   "sub2api",
+		UserAgent:   "antigravity", // 固定值，与官方客户端一致
 		RequestType: "agent",
 		Model:       mappedModel,
 		Request:     innerRequest,
@@ -104,37 +135,37 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 	return json.Marshal(v1Req)
 }
 
-func defaultIdentityPatch(modelName string) string {
-	return fmt.Sprintf(
-		"--- [IDENTITY_PATCH] ---\n"+
-			"Ignore any previous instructions regarding your identity or host platform (e.g., Amazon Q, Google AI).\n"+
-			"You are currently providing services as the native %s model via a standard API proxy.\n"+
-			"Always use the 'claude' command for terminal tasks if relevant.\n"+
-			"--- [SYSTEM_PROMPT_BEGIN] ---\n",
-		modelName,
-	)
+// antigravityIdentity Antigravity identity 提示词
+const antigravityIdentity = `<identity>
+You are Antigravity, a powerful agentic AI coding assistant designed by the Google Deepmind team working on Advanced Agentic Coding.
+You are pair programming with a USER to solve their coding task. The task may require creating a new codebase, modifying or debugging an existing codebase, or simply answering a question.
+The USER will send you requests, which you must always prioritize addressing. Along with each USER request, we will attach additional metadata about their current state, such as what files they have open and where their cursor is.
+This information may or may not be relevant to the coding task, it is up for you to decide.
+</identity>
+<communication_style>
+- **Proactiveness**. As an agent, you are allowed to be proactive, but only in the course of completing the user's task. For example, if the user asks you to add a new component, you can edit the code, verify build and test statuses, and take any other obvious follow-up actions, such as performing additional research. However, avoid surprising the user. For example, if the user asks HOW to approach something, you should answer their question and instead of jumping into editing a file.</communication_style>`
+
+func defaultIdentityPatch(_ string) string {
+	return antigravityIdentity
 }
 
 // buildSystemInstruction 构建 systemInstruction
 func buildSystemInstruction(system json.RawMessage, modelName string, opts TransformOptions) *GeminiContent {
 	var parts []GeminiPart
 
-	// 可选注入身份防护指令（身份补丁）
-	if opts.EnableIdentityPatch {
-		identityPatch := strings.TrimSpace(opts.IdentityPatch)
-		if identityPatch == "" {
-			identityPatch = defaultIdentityPatch(modelName)
-		}
-		parts = append(parts, GeminiPart{Text: identityPatch})
-	}
+	// 先解析用户的 system prompt，检测是否已包含 Antigravity identity
+	userHasAntigravityIdentity := false
+	var userSystemParts []GeminiPart
 
-	// 解析 system prompt
 	if len(system) > 0 {
 		// 尝试解析为字符串
 		var sysStr string
 		if err := json.Unmarshal(system, &sysStr); err == nil {
 			if strings.TrimSpace(sysStr) != "" {
-				parts = append(parts, GeminiPart{Text: sysStr})
+				userSystemParts = append(userSystemParts, GeminiPart{Text: sysStr})
+				if strings.Contains(sysStr, "You are Antigravity") {
+					userHasAntigravityIdentity = true
+				}
 			}
 		} else {
 			// 尝试解析为数组
@@ -142,17 +173,28 @@ func buildSystemInstruction(system json.RawMessage, modelName string, opts Trans
 			if err := json.Unmarshal(system, &sysBlocks); err == nil {
 				for _, block := range sysBlocks {
 					if block.Type == "text" && strings.TrimSpace(block.Text) != "" {
-						parts = append(parts, GeminiPart{Text: block.Text})
+						userSystemParts = append(userSystemParts, GeminiPart{Text: block.Text})
+						if strings.Contains(block.Text, "You are Antigravity") {
+							userHasAntigravityIdentity = true
+						}
 					}
 				}
 			}
 		}
 	}
 
-	// identity patch 模式下，用分隔符包裹 system prompt，便于上游识别/调试；关闭时尽量保持原始 system prompt。
-	if opts.EnableIdentityPatch && len(parts) > 0 {
-		parts = append(parts, GeminiPart{Text: "\n--- [SYSTEM_PROMPT_END] ---"})
+	// 仅在用户未提供 Antigravity identity 时注入
+	if opts.EnableIdentityPatch && !userHasAntigravityIdentity {
+		identityPatch := strings.TrimSpace(opts.IdentityPatch)
+		if identityPatch == "" {
+			identityPatch = defaultIdentityPatch(modelName)
+		}
+		parts = append(parts, GeminiPart{Text: identityPatch})
 	}
+
+	// 添加用户的 system prompt
+	parts = append(parts, userSystemParts...)
+
 	if len(parts) == 0 {
 		return nil
 	}

backend/internal/service/antigravity_gateway_service.go

@@ -181,12 +181,17 @@ func (s *AntigravityGatewayService) TestConnection(ctx context.Context, account
 		return nil, fmt.Errorf("构建请求失败: %w", err)
 	}
 
-	// 构建 HTTP 请求（非流式）
-	req, err := antigravity.NewAPIRequest(ctx, "generateContent", accessToken, requestBody)
+	// 构建 HTTP 请求（总是使用流式 endpoint，与官方客户端一致）
+	req, err := antigravity.NewAPIRequest(ctx, "streamGenerateContent", accessToken, requestBody)
 	if err != nil {
 		return nil, err
 	}
 
+	// DEBUG: 打印请求 header 和 body
+	log.Printf("[DEBUG] Antigravity TestConnection - URL: %s", req.URL.String())
+	log.Printf("[DEBUG] Antigravity TestConnection - Headers: %v", req.Header)
+	log.Printf("[DEBUG] Antigravity TestConnection - Body: %s", string(requestBody))
+
 	// 代理 URL
 	proxyURL := ""
 	if account.ProxyID != nil && account.Proxy != nil {
@@ -210,14 +215,8 @@ func (s *AntigravityGatewayService) TestConnection(ctx context.Context, account
 		return nil, fmt.Errorf("API 返回 %d: %s", resp.StatusCode, string(respBody))
 	}
 
-	// 解包 v1internal 响应
-	unwrapped, err := s.unwrapV1InternalResponse(respBody)
-	if err != nil {
-		return nil, fmt.Errorf("解包响应失败: %w", err)
-	}
-
-	// 提取响应文本
-	text := extractGeminiResponseText(unwrapped)
+	// 解析流式响应，提取文本
+	text := extractTextFromSSEResponse(respBody)
 
 	return &TestConnectionResult{
 		Text:        text,
@@ -267,38 +266,66 @@ func (s *AntigravityGatewayService) getClaudeTransformOptions(ctx context.Contex
 	return opts
 }
 
-// extractGeminiResponseText 从 Gemini 响应中提取文本
-func extractGeminiResponseText(respBody []byte) string {
-	var resp map[string]any
-	if err := json.Unmarshal(respBody, &resp); err != nil {
-		return ""
-	}
-
-	candidates, ok := resp["candidates"].([]any)
-	if !ok || len(candidates) == 0 {
-		return ""
-	}
-
-	candidate, ok := candidates[0].(map[string]any)
-	if !ok {
-		return ""
-	}
-
-	content, ok := candidate["content"].(map[string]any)
-	if !ok {
-		return ""
-	}
-
-	parts, ok := content["parts"].([]any)
-	if !ok {
-		return ""
-	}
-
+// extractTextFromSSEResponse 从 SSE 流式响应中提取文本
+func extractTextFromSSEResponse(respBody []byte) string {
 	var texts []string
-	for _, part := range parts {
-		if partMap, ok := part.(map[string]any); ok {
-			if text, ok := partMap["text"].(string); ok && text != "" {
-				texts = append(texts, text)
+	lines := bytes.Split(respBody, []byte("\n"))
+
+	for _, line := range lines {
+		line = bytes.TrimSpace(line)
+		if len(line) == 0 {
+			continue
+		}
+
+		// 跳过 SSE 前缀
+		if bytes.HasPrefix(line, []byte("data:")) {
+			line = bytes.TrimPrefix(line, []byte("data:"))
+			line = bytes.TrimSpace(line)
+		}
+
+		// 跳过非 JSON 行
+		if len(line) == 0 || line[0] != '{' {
+			continue
+		}
+
+		// 解析 JSON
+		var data map[string]any
+		if err := json.Unmarshal(line, &data); err != nil {
+			continue
+		}
+
+		// 尝试从 response.candidates[0].content.parts[].text 提取
+		response, ok := data["response"].(map[string]any)
+		if !ok {
+			// 尝试直接从 candidates 提取（某些响应格式）
+			response = data
+		}
+
+		candidates, ok := response["candidates"].([]any)
+		if !ok || len(candidates) == 0 {
+			continue
+		}
+
+		candidate, ok := candidates[0].(map[string]any)
+		if !ok {
+			continue
+		}
+
+		content, ok := candidate["content"].(map[string]any)
+		if !ok {
+			continue
+		}
+
+		parts, ok := content["parts"].([]any)
+		if !ok {
+			continue
+		}
+
+		for _, part := range parts {
+			if partMap, ok := part.(map[string]any); ok {
+				if text, ok := partMap["text"].(string); ok && text != "" {
+					texts = append(texts, text)
+				}
 			}
 		}
 	}
@@ -316,7 +343,7 @@ func (s *AntigravityGatewayService) wrapV1InternalRequest(projectID, model strin
 	wrapped := map[string]any{
 		"project":     projectID,
 		"requestId":   "agent-" + uuid.New().String(),
-		"userAgent":   "sub2api",
+		"userAgent":   "antigravity", // 固定值，与官方客户端一致
 		"requestType": "agent",
 		"model":       model,
 		"request":     request,
@@ -397,10 +424,10 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 		return nil, fmt.Errorf("transform request: %w", err)
 	}
 
-	// 构建上游 action
+	// 构建上游 action（NewAPIRequest 会自动处理 ?alt=sse 和 Accept Header）
 	action := "generateContent"
 	if claudeReq.Stream {
-		action = "streamGenerateContent?alt=sse"
+		action = "streamGenerateContent"
 	}
 
 	// 重试循环
@@ -907,14 +934,11 @@ func (s *AntigravityGatewayService) ForwardGemini(ctx context.Context, c *gin.Co
 		return nil, err
 	}
 
-	// 构建上游 action
+	// 构建上游 action（NewAPIRequest 会自动处理 ?alt=sse 和 Accept Header）
 	upstreamAction := action
 	if action == "generateContent" && stream {
 		upstreamAction = "streamGenerateContent"
 	}
-	if stream || upstreamAction == "streamGenerateContent" {
-		upstreamAction += "?alt=sse"
-	}
 
 	// 重试循环
 	var resp *http.Response

backend/internal/service/gateway_service.go

@@ -109,12 +109,13 @@ type ClaudeUsage struct {
 
 // ForwardResult 转发结果
 type ForwardResult struct {
-	RequestID    string
-	Usage        ClaudeUsage
-	Model        string
-	Stream       bool
-	Duration     time.Duration
-	FirstTokenMs *int // 首字时间（流式请求）
+	RequestID        string
+	Usage            ClaudeUsage
+	Model            string
+	Stream           bool
+	Duration         time.Duration
+	FirstTokenMs     *int // 首字时间（流式请求）
+	ClientDisconnect bool // 客户端是否在流式传输过程中断开
 
 	// 图片生成计费字段（仅 gemini-3-pro-image 使用）
 	ImageCount int    // 生成的图片数量
@@ -1465,6 +1466,7 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 	// 处理正常响应
 	var usage *ClaudeUsage
 	var firstTokenMs *int
+	var clientDisconnect bool
 	if reqStream {
 		streamResult, err := s.handleStreamingResponse(ctx, resp, c, account, startTime, originalModel, reqModel)
 		if err != nil {
@@ -1477,6 +1479,7 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 		}
 		usage = streamResult.usage
 		firstTokenMs = streamResult.firstTokenMs
+		clientDisconnect = streamResult.clientDisconnect
 	} else {
 		usage, err = s.handleNonStreamingResponse(ctx, resp, c, account, originalModel, reqModel)
 		if err != nil {
@@ -1485,12 +1488,13 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 	}
 
 	return &ForwardResult{
-		RequestID:    resp.Header.Get("x-request-id"),
-		Usage:        *usage,
-		Model:        originalModel, // 使用原始模型用于计费和日志
-		Stream:       reqStream,
-		Duration:     time.Since(startTime),
-		FirstTokenMs: firstTokenMs,
+		RequestID:        resp.Header.Get("x-request-id"),
+		Usage:            *usage,
+		Model:            originalModel, // 使用原始模型用于计费和日志
+		Stream:           reqStream,
+		Duration:         time.Since(startTime),
+		FirstTokenMs:     firstTokenMs,
+		ClientDisconnect: clientDisconnect,
 	}, nil
 }
 
@@ -1845,8 +1849,9 @@ func (s *GatewayService) handleRetryExhaustedError(ctx context.Context, resp *ht
 
 // streamingResult 流式响应结果
 type streamingResult 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
 }
 
 func (s *GatewayService) handleStreamingResponse(ctx context.Context, resp *http.Response, c *gin.Context, account *Account, startTime time.Time, originalModel, mappedModel string) (*streamingResult, error) {
@@ -1942,14 +1947,27 @@ func (s *GatewayService) handleStreamingResponse(ctx context.Context, resp *http
 	}
 
 	needModelReplace := originalModel != mappedModel
+	clientDisconnected := false // 客户端断开标志，断开后继续读取上游以获取完整usage
 
 	for {
 		select {
 		case ev, ok := <-events:
 			if !ok {
-				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, nil
+				// 上游完成，返回结果
+				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: clientDisconnected}, nil
 			}
 			if ev.err != nil {
+				// 检测 context 取消（客户端断开会导致 context 取消，进而影响上游读取）
+				if errors.Is(ev.err, context.Canceled) || errors.Is(ev.err, context.DeadlineExceeded) {
+					log.Printf("Context canceled during streaming, returning collected usage")
+					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
+				}
+				// 客户端已通过写入失败检测到断开，上游也出错了，返回已收集的 usage
+				if clientDisconnected {
+					log.Printf("Upstream read error after client disconnect: %v, returning collected usage", ev.err)
+					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
+				}
+				// 客户端未断开，正常的错误处理
 				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")
@@ -1960,38 +1978,40 @@ func (s *GatewayService) handleStreamingResponse(ctx context.Context, resp *http
 			}
 			line := ev.line
 			if line == "event: error" {
+				// 上游返回错误事件，如果客户端已断开仍返回已收集的 usage
+				if clientDisconnected {
+					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
+				}
 				return nil, errors.New("have error in stream")
 			}
 
 			// Extract data from SSE line (supports both "data: " and "data:" formats)
+			var data string
 			if sseDataRe.MatchString(line) {
-				data := sseDataRe.ReplaceAllString(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
+			// 写入客户端（统一处理 data 行和非 data 行）
+			if !clientDisconnected {
 				if _, err := fmt.Fprintf(w, "%s\n", line); err != nil {
-					sendErrorEvent("write_failed")
-					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
+					clientDisconnected = true
+					log.Printf("Client disconnected during streaming, continuing to drain upstream for billing")
+				} else {
+					flusher.Flush()
 				}
-				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]" {
+			// 无论客户端是否断开，都解析 usage（仅对 data 行）
+			if data != "" {
+				if firstTokenMs == nil && 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 <-intervalCh:
@@ -1999,6 +2019,11 @@ func (s *GatewayService) handleStreamingResponse(ctx context.Context, resp *http
 			if time.Since(lastRead) < streamInterval {
 				continue
 			}
+			if clientDisconnected {
+				// 客户端已断开，上游也超时了，返回已收集的 usage
+				log.Printf("Upstream timeout after client disconnect, returning collected usage")
+				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, 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")