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- 后端新增 PreviewFromCRS 接口，允许用户先预览 CRS 中的账号
- 后端支持在同步时选择特定账号，不选中的账号将被跳过
- 前端重构 SyncFromCrsModal 为三步向导：输入凭据 → 预览账号 → 执行同步
- 改进表单无障碍性：添加 for/id 关联和 required 属性
- 修复 Back 按钮返回时的状态清理
- 新增 buildSelectedSet 和 shouldCreateAccount 的单元测试
- 完整的向后兼容性：旧客户端不发送 selected_account_ids 时行为不变

- Fix gofmt alignment in ops_realtime_models.go
- Remove SetAntigravityQuotaScopeLimit mock from api_contract_test.go
- Add UpdateSortOrders mock to mockGroupRepoForGateway

Merge functional changes from develop branch:
- Remove AntigravityQuotaScope system (claude/gemini_text/gemini_image)
- Replace with per-model rate limiting using resolveAntigravityModelKey
- Remove model load statistics (IncrModelCallCount/GetModelLoadBatch)
- Simplify account selection to unified priority→load→LRU algorithm
- Remove SetAntigravityQuotaScopeLimit from AccountRepository
- Clean up scope-related UI indicators and API fields

Add post-sort shuffle for accounts with identical (priority, loadRate,
lastUsedAt) to break deterministic ordering when concurrent requests
read the same scheduler snapshot. Applies to both Antigravity and
OpenAI scheduling paths, plus the sortAccountsByPriorityAndLastUsed
helper.

Keeps upstream CallCount/ModelLoadInfo scheduling intact; shuffle is
additive and only randomises within equivalent-rank groups.

Without this routing guard, ForwardUpstream is never called because
Forward() always proceeds with the standard OAuth/cookie flow.

- In handleSmartRetry, use the actual upstream retryDelay to set model
  rate limit duration instead of always using the 30s default
- Return info.RetryDelay from shouldTriggerAntigravitySmartRetry when
  shouldRateLimitModel=true, so callers know the actual delay
- Extract getDefaultRateLimitDuration() and resolveResetTime() helpers
  to reduce duplication in handleUpstreamError 429 handling
- Improve debug logging with upstream_retry_delay and response body

ParseGatewayRequest only parsed Anthropic format (system/messages),
ignoring Gemini native format (systemInstruction/contents). This caused
GenerateSessionHash to produce identical hashes for all Gemini sessions.

Add protocol parameter to ParseGatewayRequest to branch between
Anthropic and Gemini parsing. Update GenerateSessionHash message
traversal to extract text from both formats.

Mix SessionContext (ClientIP, UserAgent, APIKeyID) into
GenerateSessionHash 3rd-level fallback to differentiate requests
from different users sending identical content.

Also switch hashContent from SHA256-truncated to XXHash64 for
better performance, and optimize Trie Lua script to match from
longest prefix first.

Previously, thoughtSignature cleanup only applied to Gemini CLI
requests (detected via x-gemini-api-privileged-user-id header or
tmp dir pattern). This caused 400 errors for non-CLI clients when
session cache expired and they sent stale signatures.

Remove the isGeminiCLIRequest guard so all clients benefit from
proactive thoughtSignature cleanup on session binding miss.

- Add `sort_order` field to groups table with migration
- Add `PUT /api/v1/admin/groups/sort-order` API for batch update
- Implement drag-and-drop UI using vue-draggable-plus
- All queries now order groups by sort_order
- Add i18n support (en/zh) for sort-related UI text
- Update test stubs to satisfy new interface methods

优化 /admin/users 页面的并发数列，显示「当前/最大」格式，
参考 AccountCapacityCell 的设计风格。

- 后端 UserHandler 注入 ConcurrencyService，批量查询用户当前并发数
- 新增 UserConcurrencyCell 组件，支持颜色状态（空闲灰/使用中黄/满载红）
- 前端 AdminUser 类型添加 current_concurrency 字段

Upstream accounts now use the standard APIKey type instead of a dedicated
upstream type. GetBaseURL() and new GetGeminiBaseURL() automatically append
/antigravity for Antigravity platform APIKey accounts, eliminating the need
for separate upstream forwarding methods.

- Remove ForwardUpstream, ForwardUpstreamGemini, testUpstreamConnection
- Remove upstream branch guards in Forward/ForwardGemini/TestConnection
- Add migration 052 to convert existing upstream accounts to apikey
- Update frontend CreateAccountModal to create apikey type
- Add unit tests for GetBaseURL and GetGeminiBaseURL

ForwardUpstream/ForwardUpstreamGemini should pipe the upstream response
directly to the client (headers + body), not parse it as SSE stream.

Replace manual header setting (Content-Type, anthropic-version, anthropic-beta)
with full client header passthrough in ForwardUpstream/ForwardUpstreamGemini.
Only authentication headers (Authorization, x-api-key) are overridden with
upstream account credentials. Hop-by-hop headers are excluded.

Add unit tests covering header passthrough, auth override, and hop-by-hop filtering.

v0.1.74 merged upstream accounts into the OAuth path, causing requests
to hit the wrong protocol and endpoint. Add three upstream-specific
methods (testUpstreamConnection, ForwardUpstream, ForwardUpstreamGemini)
that use base_url + apiKey auth and passthrough the original body, while
reusing the existing response handling and error/retry logic.

- handleUpstreamError 补齐新增的三个参数 (0, "", false)
- handleStreamingResponse 移除已删除的 nil 参数
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

基于 backend-code-audit 审计报告，修复剩余 P0/P1/P2 共 34 项问题：

P0 生产 Bug：
- 修复 time.Since(time.Now()) 计时逻辑错误 (P0-03)
- generateRandomID 改用 crypto/rand 替代固定索引 (P0-04)
- IncrementQuotaUsed 重写为 Ent 原子操作消除 TOCTOU 竞态 (P0-05)

安全加固：
- gateway/openai handler 错误响应替换为泛化消息，防止内部信息泄露 (P1-14)
- usage_log_repo dateFormat 参数改用白名单映射，防止 SQL 注入 (P1-16)
- 默认配置安全加固：sslmode=prefer、response_headers=true、mode=release (P1-18/19, P2-15)

性能优化：
- gateway handler 循环内 defer 替换为显式 releaseWait 闭包 (P1-02)
- group_repo/promo_code_repo Count 前 Clone 查询避免状态污染 (P1-03)
- usage_log_repo 四个查询添加 LIMIT 10000 防止 OOM (P1-07)
- GetBatchUsageStats 添加时间范围参数，默认最近 30 天 (P1-10)
- ip.go CIDR 预编译为包级变量 (P1-11)
- BatchUpdateCredentials 重构为先验证后更新 (P1-13)

缓存一致性：
- billing_cache 添加 jitteredTTL 防止缓存雪崩 (P2-10)
- DeductUserBalance/UpdateSubscriptionUsage 错误传播修复 (P2-12)
- UserService.UpdateBalance 成功后异步失效 billingCache (P2-13)

代码质量：
- search 截断改为按 rune 处理，支持多字节字符 (P2-01)
- TLS Handshake 改为 HandshakeContext 支持 context 取消 (P2-07)
- CORS 预检添加 Access-Control-Max-Age: 86400 (P2-16)

测试覆盖：
- 新增 user_service_test.go（UpdateBalance 缓存失效 6 个用例）
- 新增 batch_update_credentials_test.go（fail-fast + 类型验证 7 个用例）
- 新增 response_transformer_test.go、ip_test.go、usage_log_repo_unit_test.go、search_truncate_test.go
- 集成测试：IncrementQuotaUsed 并发测试、billing_cache 错误传播测试
- config_test.go 补充 server.mode/sslmode 默认值断言
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Change antigravitySmartRetryMaxAttempts from 3 to 1 to prevent
  repeated rate limiting and long waits
- Clear sticky session binding (DeleteSessionAccountID) after smart
  retry exhaustion, so subsequent requests don't hit the same
  rate-limited account
- Add flow diagrams to Forward/ForwardGemini doc comments
- Add comprehensive unit tests covering:
  - Sticky session cleared on retry failure (429, 503, network error)
  - Sticky session NOT cleared on retry success
  - Sticky session NOT cleared for non-sticky requests (empty hash)
  - Sticky session NOT cleared on long delay path (handled by handler)
  - Nil cache safety (no panic)
  - MaxAttempts constant verification
  - End-to-end retryLoop → switchError propagation with session clear

The digest chain fallback is only needed for Gemini endpoints, not
for the Anthropic Messages API path. Remove the handler integration
while keeping the reusable service/repository layer for future use.

The previous fallback (step 3) in GenerateSessionHash hashed system +
all messages together, producing a different hash each round as the
conversation grew ([a] -> [a,b] -> [a,b,c]). This made fallback sticky
sessions ineffective for multi-turn conversations.

Implement per-message Trie digest chain matching (reusing Gemini's Trie
infrastructure) so that the previous round's chain is always a prefix
of the current round's chain, enabling reliable session affinity.

oauth 和 openai 包的 SessionStore.Stop() 直接调用 close(stopCh)，
重复调用会导致 panic。使用 sync.Once 包裹确保幂等安全。

新增单元测试覆盖连续调用和 50 goroutine 并发调用场景。
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ForgotPassword 原来从 c.Request.Host 构建重置链接基础 URL，攻击者
可伪造 Host 头将重置链接指向恶意域名窃取 token。

修复方案：
- ServerConfig 新增 frontend_url 配置项
- auth_handler 改为从配置读取前端 URL，未配置时拒绝请求
- Validate() 校验 frontend_url 必须为绝对 HTTP(S) URL
- 新增 TestValidateServerFrontendURL 单元测试
- config.example.yaml 添加配置说明
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- avoid panic by using safe UUID prefix truncation in Gemini digest fallback logs\n- remove unconditional Antigravity 429 full-body debug logs and honor log truncation config\n- align Antigravity quick preset mappings to opus 4.6-thinking targets only\n- restore scope rate-limit aggregation/output in ops availability stats

SSE 热路径中 replaceModelInSSELine 和 replaceModelInResponseBody 原来
使用 json.Unmarshal/Marshal 对每个事件做全量反序列化再序列化，现改为
gjson.Get/sjson.Set 精确字段操作，消除 O(n) 中间 map 分配，保持 JSON
字段顺序不变。涉及 OpenAIGatewayService 和 GatewayService 两个服务。

新增 23 个单元测试覆盖：顶层/嵌套 model 替换、不匹配跳过、空行/[DONE]/
非法 JSON 等边界情况。

Fixes: P1-08
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Remove threshold-based waiting in both sticky session and antigravity
pre-check paths. When a model is rate-limited, immediately clear the
sticky session and switch accounts instead of waiting for short durations.

管理员改密后旧JWT会被拒绝，并补充单元测试覆盖。