fix: 修复 /v1/messages 间歇性 400 错误 (#112)

* fix(upstream): 修复上游格式兼容性问题

- 跳过Claude模型无signature的thinking block
- 支持custom类型工具(MCP)格式转换
- 添加ClaudeCustomToolSpec结构体支持MCP工具
- 添加Custom字段验证，跳过无效custom工具
- 在convertClaudeToolsToGeminiTools中添加schema清理
- 完整的单元测试覆盖，包含边界情况

修复: Issue 0.1 signature缺失, Issue 0.2 custom工具格式
改进: Codex审查发现的2个重要问题

测试:
- TestBuildParts_ThinkingBlockWithoutSignature: 验证thinking block处理
- TestBuildTools_CustomTypeTools: 验证custom工具转换和边界情况
- TestConvertClaudeToolsToGeminiTools_CustomType: 验证service层转换

* feat(gemini): 添加Gemini限额与TierID支持

实现PR1：Gemini限额与TierID功能

后端修改：
- GeminiTokenInfo结构体添加TierID字段
- fetchProjectID函数返回(projectID, tierID, error)
- 从LoadCodeAssist响应中提取tierID（优先IsDefault，回退到第一个非空tier）
- ExchangeCode、RefreshAccountToken、GetAccessToken函数更新以处理tierID
- BuildAccountCredentials函数保存tier_id到credentials

前端修改：
- AccountStatusIndicator组件添加tier显示
- 支持LEGACY/PRO/ULTRA等tier类型的友好显示
- 使用蓝色badge展示tier信息

技术细节：
- tierID提取逻辑：优先选择IsDefault的tier，否则选择第一个非空tier
- 所有fetchProjectID调用点已更新以处理新的返回签名
- 前端gracefully处理missing/unknown tier_id

* refactor(gemini): 优化TierID实现并添加安全验证

根据并发代码审查（code-reviewer, security-auditor, gemini, codex）的反馈进行改进：

安全改进：
- 添加validateTierID函数验证tier_id格式和长度（最大64字符）
- 限制tier_id字符集为字母数字、下划线、连字符和斜杠
- 在BuildAccountCredentials中验证tier_id后再存储
- 静默跳过无效tier_id，不阻塞账户创建

代码质量改进：
- 提取extractTierIDFromAllowedTiers辅助函数消除重复代码
- 重构fetchProjectID函数，tierID提取逻辑只执行一次
- 改进代码可读性和可维护性

审查工具：
- code-reviewer agent (a09848e)
- security-auditor agent (a9a149c)
- gemini CLI (bcc7c81)
- codex (b5d8919)

修复问题：
- HIGH: 未验证的tier_id输入
- MEDIUM: 代码重复（tierID提取逻辑重复2次）

* fix(format): 修复 gofmt 格式问题

- 修复 claude_types.go 中的字段对齐问题
- 修复 gemini_messages_compat_service.go 中的缩进问题

* fix(upstream): 修复上游格式兼容性问题 (#14)

* fix(upstream): 修复上游格式兼容性问题

- 跳过Claude模型无signature的thinking block
- 支持custom类型工具(MCP)格式转换
- 添加ClaudeCustomToolSpec结构体支持MCP工具
- 添加Custom字段验证，跳过无效custom工具
- 在convertClaudeToolsToGeminiTools中添加schema清理
- 完整的单元测试覆盖，包含边界情况

修复: Issue 0.1 signature缺失, Issue 0.2 custom工具格式
改进: Codex审查发现的2个重要问题

测试:
- TestBuildParts_ThinkingBlockWithoutSignature: 验证thinking block处理
- TestBuildTools_CustomTypeTools: 验证custom工具转换和边界情况
- TestConvertClaudeToolsToGeminiTools_CustomType: 验证service层转换

* fix(format): 修复 gofmt 格式问题

- 修复 claude_types.go 中的字段对齐问题
- 修复 gemini_messages_compat_service.go 中的缩进问题

* fix(format): 修复 claude_types.go 的 gofmt 格式问题

* feat(antigravity): 优化 thinking block 和 schema 处理

- 为 dummy thinking block 添加 ThoughtSignature
- 重构 thinking block 处理逻辑，在每个条件分支内创建 part
- 优化 excludedSchemaKeys，移除 Gemini 实际支持的字段
  (minItems, maxItems, minimum, maximum, additionalProperties, format)
- 添加详细注释说明 Gemini API 支持的 schema 字段

* fix(antigravity): 增强 schema 清理的安全性

基于 Codex review 建议：
- 添加 format 字段白名单过滤，只保留 Gemini 支持的 date-time/date/time
- 补充更多不支持的 schema 关键字到黑名单：
  * 组合 schema: oneOf, anyOf, allOf, not, if/then/else
  * 对象验证: minProperties, maxProperties, patternProperties 等
  * 定义引用: $defs, definitions
- 避免不支持的 schema 字段导致 Gemini API 校验失败

* fix(lint): 修复 gemini_messages_compat_service 空分支警告

- 在 cleanToolSchema 的 if 语句中添加 continue
- 移除重复的注释

* fix(antigravity): 移除 minItems/maxItems 以兼容 Claude API

- 将 minItems 和 maxItems 添加到 schema 黑名单
- Claude API (Vertex AI) 不支持这些数组验证字段
- 添加调试日志记录工具 schema 转换过程
- 修复 tools.14.custom.input_schema 验证错误

* fix(antigravity): 修复 additionalProperties schema 对象问题

- 将 additionalProperties 的 schema 对象转换为布尔值 true
- Claude API 只支持 additionalProperties: false，不支持 schema 对象
- 修复 tools.14.custom.input_schema 验证错误
- 参考 Claude 官方文档的 JSON Schema 限制

* fix(antigravity): 修复 Claude 模型 thinking 块兼容性问题

- 完全跳过 Claude 模型的 thinking 块以避免 signature 验证失败
- 只在 Gemini 模型中使用 dummy thought signature
- 修改 additionalProperties 默认值为 false（更安全）
- 添加调试日志以便排查问题

* fix(upstream): 修复跨模型切换时的 dummy signature 问题

基于 Codex review 和用户场景分析的修复：

1. 问题场景
   - Gemini (thinking) → Claude (thinking) 切换时
   - Gemini 返回的 thinking 块使用 dummy signature
   - Claude API 会拒绝 dummy signature，导致 400 错误

2. 修复内容
   - request_transformer.go:262: 跳过 dummy signature
   - 只保留真实的 Claude signature
   - 支持频繁的跨模型切换

3. 其他修复（基于 Codex review）
   - gateway_service.go:691: 修复 io.ReadAll 错误处理
   - gateway_service.go:687: 条件日志（尊重 LogUpstreamErrorBody 配置）
   - gateway_service.go:915: 收紧 400 failover 启发式
   - request_transformer.go:188: 移除签名成功日志

4. 新增功能（默认关闭）
   - 阶段 1: 上游错误日志（GATEWAY_LOG_UPSTREAM_ERROR_BODY）
   - 阶段 2: Antigravity thinking 修复
   - 阶段 3: API-key beta 注入（GATEWAY_INJECT_BETA_FOR_APIKEY）
   - 阶段 3: 智能 400 failover（GATEWAY_FAILOVER_ON_400）

测试：所有测试通过

* fix(lint): 修复 golangci-lint 问题

- 应用 De Morgan 定律简化条件判断
- 修复 gofmt 格式问题
- 移除未使用的 min 函数

backend/internal/config/config.go

@@ -119,6 +119,17 @@ type GatewayConfig struct {
 	// ConcurrencySlotTTLMinutes: 并发槽位过期时间（分钟）
 	// 应大于最长 LLM 请求时间，防止请求完成前槽位过期
 	ConcurrencySlotTTLMinutes int `mapstructure:"concurrency_slot_ttl_minutes"`
+
+	// 是否记录上游错误响应体摘要（避免输出请求内容）
+	LogUpstreamErrorBody bool `mapstructure:"log_upstream_error_body"`
+	// 上游错误响应体记录最大字节数（超过会截断）
+	LogUpstreamErrorBodyMaxBytes int `mapstructure:"log_upstream_error_body_max_bytes"`
+
+	// API-key 账号在客户端未提供 anthropic-beta 时，是否按需自动补齐（默认关闭以保持兼容）
+	InjectBetaForApiKey bool `mapstructure:"inject_beta_for_apikey"`
+
+	// 是否允许对部分 400 错误触发 failover（默认关闭以避免改变语义）
+	FailoverOn400 bool `mapstructure:"failover_on_400"`
 }
 
 func (s *ServerConfig) Address() string {
@@ -313,6 +324,10 @@ func setDefaults() {
 
 	// Gateway
 	viper.SetDefault("gateway.response_header_timeout", 300) // 300秒(5分钟)等待上游响应头，LLM高负载时可能排队较久
+	viper.SetDefault("gateway.log_upstream_error_body", false)
+	viper.SetDefault("gateway.log_upstream_error_body_max_bytes", 2048)
+	viper.SetDefault("gateway.inject_beta_for_apikey", false)
+	viper.SetDefault("gateway.failover_on_400", false)
 	viper.SetDefault("gateway.max_body_size", int64(100*1024*1024))
 	viper.SetDefault("gateway.connection_pool_isolation", ConnectionPoolIsolationAccountProxy)
 	// HTTP 上游连接池配置（针对 5000+ 并发用户优化）

backend/internal/pkg/antigravity/claude_types.go

@@ -54,6 +54,9 @@ type CustomToolSpec struct {
 	InputSchema map[string]any `json:"input_schema"`
 }
 
+// ClaudeCustomToolSpec 兼容旧命名（MCP custom 工具规格）
+type ClaudeCustomToolSpec = CustomToolSpec
+
 // SystemBlock system prompt 数组形式的元素
 type SystemBlock struct {
 	Type string `json:"type"`

backend/internal/pkg/antigravity/request_transformer.go

@@ -14,13 +14,16 @@ func TransformClaudeToGemini(claudeReq *ClaudeRequest, projectID, mappedModel st
 	// 用于存储 tool_use id -> name 映射
 	toolIDToName := make(map[string]string)
 
-	// 检测是否启用 thinking
-	isThinkingEnabled := claudeReq.Thinking != nil && claudeReq.Thinking.Type == "enabled"
-
 	// 只有 Gemini 模型支持 dummy thought workaround
 	// Claude 模型通过 Vertex/Google API 需要有效的 thought signatures
 	allowDummyThought := strings.HasPrefix(mappedModel, "gemini-")
 
+	// 检测是否启用 thinking
+	requestedThinkingEnabled := claudeReq.Thinking != nil && claudeReq.Thinking.Type == "enabled"
+	// 为避免 Claude 模型的 thought signature/消息块约束导致 400（上游要求 thinking 块开头等），
+	// 非 Gemini 模型默认不启用 thinking（除非未来支持完整签名链路）。
+	isThinkingEnabled := requestedThinkingEnabled && allowDummyThought
+
 	// 1. 构建 contents
 	contents, err := buildContents(claudeReq.Messages, toolIDToName, isThinkingEnabled, allowDummyThought)
 	if err != nil {
@@ -31,7 +34,15 @@ func TransformClaudeToGemini(claudeReq *ClaudeRequest, projectID, mappedModel st
 	systemInstruction := buildSystemInstruction(claudeReq.System, claudeReq.Model)
 
 	// 3. 构建 generationConfig
-	generationConfig := buildGenerationConfig(claudeReq)
+	reqForGen := claudeReq
+	if requestedThinkingEnabled && !allowDummyThought {
+		log.Printf("[Warning] Disabling thinking for non-Gemini model in antigravity transform: model=%s", mappedModel)
+		// shallow copy to avoid mutating caller's request
+		clone := *claudeReq
+		clone.Thinking = nil
+		reqForGen = &clone
+	}
+	generationConfig := buildGenerationConfig(reqForGen)
 
 	// 4. 构建 tools
 	tools := buildTools(claudeReq.Tools)
@@ -148,8 +159,9 @@ func buildContents(messages []ClaudeMessage, toolIDToName map[string]string, isT
 			if !hasThoughtPart && len(parts) > 0 {
 				// 在开头添加 dummy thinking block
 				parts = append([]GeminiPart{{
-					Text:    "Thinking...",
-					Thought: true,
+					Text:             "Thinking...",
+					Thought:          true,
+					ThoughtSignature: dummyThoughtSignature,
 				}}, parts...)
 			}
 		}
@@ -171,6 +183,34 @@ func buildContents(messages []ClaudeMessage, toolIDToName map[string]string, isT
 // 参考: https://ai.google.dev/gemini-api/docs/thought-signatures
 const dummyThoughtSignature = "skip_thought_signature_validator"
 
+// isValidThoughtSignature 验证 thought signature 是否有效
+// Claude API 要求 signature 必须是 base64 编码的字符串，长度至少 32 字节
+func isValidThoughtSignature(signature string) bool {
+	// 空字符串无效
+	if signature == "" {
+		return false
+	}
+
+	// signature 应该是 base64 编码，长度至少 40 个字符（约 30 字节）
+	// 参考 Claude API 文档和实际观察到的有效 signature
+	if len(signature) < 40 {
+		log.Printf("[Debug] Signature too short: len=%d", len(signature))
+		return false
+	}
+
+	// 检查是否是有效的 base64 字符
+	// base64 字符集: A-Z, a-z, 0-9, +, /, =
+	for i, c := range signature {
+		if (c < 'A' || c > 'Z') && (c < 'a' || c > 'z') &&
+			(c < '0' || c > '9') && c != '+' && c != '/' && c != '=' {
+			log.Printf("[Debug] Invalid base64 character at position %d: %c (code=%d)", i, c, c)
+			return false
+		}
+	}
+
+	return true
+}
+
 // buildParts 构建消息的 parts
 // allowDummyThought: 只有 Gemini 模型支持 dummy thought signature
 func buildParts(content json.RawMessage, toolIDToName map[string]string, allowDummyThought bool) ([]GeminiPart, error) {
@@ -199,22 +239,30 @@ func buildParts(content json.RawMessage, toolIDToName map[string]string, allowDu
 			}
 
 		case "thinking":
-			part := GeminiPart{
-				Text:    block.Thinking,
-				Thought: true,
-			}
-			// 保留原有 signature（Claude 模型需要有效的 signature）
-			if block.Signature != "" {
-				part.ThoughtSignature = block.Signature
-			} else if !allowDummyThought {
-				// Claude 模型需要有效 signature，跳过无 signature 的 thinking block
-				log.Printf("Warning: skipping thinking block without signature for Claude model")
+			if allowDummyThought {
+				// Gemini 模型可以使用 dummy signature
+				parts = append(parts, GeminiPart{
+					Text:             block.Thinking,
+					Thought:          true,
+					ThoughtSignature: dummyThoughtSignature,
+				})
 				continue
-			} else {
-				// Gemini 模型使用 dummy signature
-				part.ThoughtSignature = dummyThoughtSignature
 			}
-			parts = append(parts, part)
+
+			// Claude 模型：仅在提供有效 signature 时保留 thinking block；否则跳过以避免上游校验失败。
+			signature := strings.TrimSpace(block.Signature)
+			if signature == "" || signature == dummyThoughtSignature {
+				log.Printf("[Warning] Skipping thinking block for Claude model (missing or dummy signature)")
+				continue
+			}
+			if !isValidThoughtSignature(signature) {
+				log.Printf("[Debug] Thinking signature may be invalid (passing through anyway): len=%d", len(signature))
+			}
+			parts = append(parts, GeminiPart{
+				Text:             block.Thinking,
+				Thought:          true,
+				ThoughtSignature: signature,
+			})
 
 		case "image":
 			if block.Source != nil && block.Source.Type == "base64" {
@@ -239,10 +287,9 @@ func buildParts(content json.RawMessage, toolIDToName map[string]string, allowDu
 					ID:   block.ID,
 				},
 			}
-			// 保留原有 signature，或对 Gemini 模型使用 dummy signature
-			if block.Signature != "" {
-				part.ThoughtSignature = block.Signature
-			} else if allowDummyThought {
+			// 只有 Gemini 模型使用 dummy signature
+			// Claude 模型不设置 signature（避免验证问题）
+			if allowDummyThought {
 				part.ThoughtSignature = dummyThoughtSignature
 			}
 			parts = append(parts, part)
@@ -386,9 +433,9 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 
 	// 普通工具
 	var funcDecls []GeminiFunctionDecl
-	for _, tool := range tools {
+	for i, tool := range tools {
 		// 跳过无效工具名称
-		if tool.Name == "" {
+		if strings.TrimSpace(tool.Name) == "" {
 			log.Printf("Warning: skipping tool with empty name")
 			continue
 		}
@@ -397,10 +444,18 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 		var inputSchema map[string]any
 
 		// 检查是否为 custom 类型工具 (MCP)
-		if tool.Type == "custom" && tool.Custom != nil {
-			// Custom 格式: 从 custom 字段获取 description 和 input_schema
+		if tool.Type == "custom" {
+			if tool.Custom == nil || tool.Custom.InputSchema == nil {
+				log.Printf("[Warning] Skipping invalid custom tool '%s': missing custom spec or input_schema", tool.Name)
+				continue
+			}
 			description = tool.Custom.Description
 			inputSchema = tool.Custom.InputSchema
+
+			// 调试日志：记录 custom 工具的 schema
+			if schemaJSON, err := json.Marshal(inputSchema); err == nil {
+				log.Printf("[Debug] Tool[%d] '%s' (custom) original schema: %s", i, tool.Name, string(schemaJSON))
+			}
 		} else {
 			// 标准格式: 从顶层字段获取
 			description = tool.Description
@@ -409,7 +464,6 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 
 		// 清理 JSON Schema
 		params := cleanJSONSchema(inputSchema)
-
 		// 为 nil schema 提供默认值
 		if params == nil {
 			params = map[string]any{
@@ -418,6 +472,11 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 			}
 		}
 
+		// 调试日志：记录清理后的 schema
+		if paramsJSON, err := json.Marshal(params); err == nil {
+			log.Printf("[Debug] Tool[%d] '%s' cleaned schema: %s", i, tool.Name, string(paramsJSON))
+		}
+
 		funcDecls = append(funcDecls, GeminiFunctionDecl{
 			Name:        tool.Name,
 			Description: description,
@@ -479,31 +538,64 @@ func cleanJSONSchema(schema map[string]any) map[string]any {
 }
 
 // excludedSchemaKeys 不支持的 schema 字段
+// 基于 Claude API (Vertex AI) 的实际支持情况
+// 支持: type, description, enum, properties, required, additionalProperties, items
+// 不支持: minItems, maxItems, minLength, maxLength, pattern, minimum, maximum 等验证字段
 var excludedSchemaKeys = map[string]bool{
-	"$schema":              true,
-	"$id":                  true,
-	"$ref":                 true,
-	"additionalProperties": true,
-	"minLength":            true,
-	"maxLength":            true,
-	"minItems":             true,
-	"maxItems":             true,
-	"uniqueItems":          true,
-	"minimum":              true,
-	"maximum":              true,
-	"exclusiveMinimum":     true,
-	"exclusiveMaximum":     true,
-	"pattern":              true,
-	"format":               true,
-	"default":              true,
-	"strict":               true,
-	"const":                true,
-	"examples":             true,
-	"deprecated":           true,
-	"readOnly":             true,
-	"writeOnly":            true,
-	"contentMediaType":     true,
-	"contentEncoding":      true,
+	// 元 schema 字段
+	"$schema": true,
+	"$id":     true,
+	"$ref":    true,
+
+	// 字符串验证（Gemini 不支持）
+	"minLength": true,
+	"maxLength": true,
+	"pattern":   true,
+
+	// 数字验证（Claude API 通过 Vertex AI 不支持这些字段）
+	"minimum":          true,
+	"maximum":          true,
+	"exclusiveMinimum": true,
+	"exclusiveMaximum": true,
+	"multipleOf":       true,
+
+	// 数组验证（Claude API 通过 Vertex AI 不支持这些字段）
+	"uniqueItems": true,
+	"minItems":    true,
+	"maxItems":    true,
+
+	// 组合 schema（Gemini 不支持）
+	"oneOf":       true,
+	"anyOf":       true,
+	"allOf":       true,
+	"not":         true,
+	"if":          true,
+	"then":        true,
+	"else":        true,
+	"$defs":       true,
+	"definitions": true,
+
+	// 对象验证（仅保留 properties/required/additionalProperties）
+	"minProperties":     true,
+	"maxProperties":     true,
+	"patternProperties": true,
+	"propertyNames":     true,
+	"dependencies":      true,
+	"dependentSchemas":  true,
+	"dependentRequired": true,
+
+	// 其他不支持的字段
+	"default":          true,
+	"const":            true,
+	"examples":         true,
+	"deprecated":       true,
+	"readOnly":         true,
+	"writeOnly":        true,
+	"contentMediaType": true,
+	"contentEncoding":  true,
+
+	// Claude 特有字段
+	"strict": true,
 }
 
 // cleanSchemaValue 递归清理 schema 值
@@ -523,6 +615,31 @@ func cleanSchemaValue(value any) any {
 				continue
 			}
 
+			// 特殊处理 format 字段：只保留 Gemini 支持的 format 值
+			if k == "format" {
+				if formatStr, ok := val.(string); ok {
+					// Gemini 只支持 date-time, date, time
+					if formatStr == "date-time" || formatStr == "date" || formatStr == "time" {
+						result[k] = val
+					}
+					// 其他 format 值直接跳过
+				}
+				continue
+			}
+
+			// 特殊处理 additionalProperties：Claude API 只支持布尔值，不支持 schema 对象
+			if k == "additionalProperties" {
+				if boolVal, ok := val.(bool); ok {
+					result[k] = boolVal
+					log.Printf("[Debug] additionalProperties is bool: %v", boolVal)
+				} else {
+					// 如果是 schema 对象，转换为 false（更安全的默认值）
+					result[k] = false
+					log.Printf("[Debug] additionalProperties is not bool (type: %T), converting to false", val)
+				}
+				continue
+			}
+
 			// 递归清理所有值
 			result[k] = cleanSchemaValue(val)
 		}

backend/internal/pkg/antigravity/request_transformer_test.go

@@ -0,0 +1,179 @@
+package antigravity
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+// TestBuildParts_ThinkingBlockWithoutSignature 测试thinking block无signature时的处理
+func TestBuildParts_ThinkingBlockWithoutSignature(t *testing.T) {
+	tests := []struct {
+		name              string
+		content           string
+		allowDummyThought bool
+		expectedParts     int
+		description       string
+	}{
+		{
+			name: "Claude model - skip thinking block without signature",
+			content: `[
+				{"type": "text", "text": "Hello"},
+				{"type": "thinking", "thinking": "Let me think...", "signature": ""},
+				{"type": "text", "text": "World"}
+			]`,
+			allowDummyThought: false,
+			expectedParts:     2, // 只有两个text block
+			description:       "Claude模型应该跳过无signature的thinking block",
+		},
+		{
+			name: "Claude model - keep thinking block with signature",
+			content: `[
+				{"type": "text", "text": "Hello"},
+				{"type": "thinking", "thinking": "Let me think...", "signature": "valid_sig"},
+				{"type": "text", "text": "World"}
+			]`,
+			allowDummyThought: false,
+			expectedParts:     3, // 三个block都保留
+			description:       "Claude模型应该保留有signature的thinking block",
+		},
+		{
+			name: "Gemini model - use dummy signature",
+			content: `[
+				{"type": "text", "text": "Hello"},
+				{"type": "thinking", "thinking": "Let me think...", "signature": ""},
+				{"type": "text", "text": "World"}
+			]`,
+			allowDummyThought: true,
+			expectedParts:     3, // 三个block都保留，thinking使用dummy signature
+			description:       "Gemini模型应该为无signature的thinking block使用dummy signature",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			toolIDToName := make(map[string]string)
+			parts, err := buildParts(json.RawMessage(tt.content), toolIDToName, tt.allowDummyThought)
+
+			if err != nil {
+				t.Fatalf("buildParts() error = %v", err)
+			}
+
+			if len(parts) != tt.expectedParts {
+				t.Errorf("%s: got %d parts, want %d parts", tt.description, len(parts), tt.expectedParts)
+			}
+		})
+	}
+}
+
+// TestBuildTools_CustomTypeTools 测试custom类型工具转换
+func TestBuildTools_CustomTypeTools(t *testing.T) {
+	tests := []struct {
+		name        string
+		tools       []ClaudeTool
+		expectedLen int
+		description string
+	}{
+		{
+			name: "Standard tool format",
+			tools: []ClaudeTool{
+				{
+					Name:        "get_weather",
+					Description: "Get weather information",
+					InputSchema: map[string]any{
+						"type": "object",
+						"properties": map[string]any{
+							"location": map[string]any{"type": "string"},
+						},
+					},
+				},
+			},
+			expectedLen: 1,
+			description: "标准工具格式应该正常转换",
+		},
+		{
+			name: "Custom type tool (MCP format)",
+			tools: []ClaudeTool{
+				{
+					Type: "custom",
+					Name: "mcp_tool",
+					Custom: &ClaudeCustomToolSpec{
+						Description: "MCP tool description",
+						InputSchema: map[string]any{
+							"type": "object",
+							"properties": map[string]any{
+								"param": map[string]any{"type": "string"},
+							},
+						},
+					},
+				},
+			},
+			expectedLen: 1,
+			description: "Custom类型工具应该从Custom字段读取description和input_schema",
+		},
+		{
+			name: "Mixed standard and custom tools",
+			tools: []ClaudeTool{
+				{
+					Name:        "standard_tool",
+					Description: "Standard tool",
+					InputSchema: map[string]any{"type": "object"},
+				},
+				{
+					Type: "custom",
+					Name: "custom_tool",
+					Custom: &ClaudeCustomToolSpec{
+						Description: "Custom tool",
+						InputSchema: map[string]any{"type": "object"},
+					},
+				},
+			},
+			expectedLen: 1, // 返回一个GeminiToolDeclaration，包含2个function declarations
+			description: "混合标准和custom工具应该都能正确转换",
+		},
+		{
+			name: "Invalid custom tool - nil Custom field",
+			tools: []ClaudeTool{
+				{
+					Type: "custom",
+					Name: "invalid_custom",
+					// Custom 为 nil
+				},
+			},
+			expectedLen: 0, // 应该被跳过
+			description: "Custom字段为nil的custom工具应该被跳过",
+		},
+		{
+			name: "Invalid custom tool - nil InputSchema",
+			tools: []ClaudeTool{
+				{
+					Type: "custom",
+					Name: "invalid_custom",
+					Custom: &ClaudeCustomToolSpec{
+						Description: "Invalid",
+						// InputSchema 为 nil
+					},
+				},
+			},
+			expectedLen: 0, // 应该被跳过
+			description: "InputSchema为nil的custom工具应该被跳过",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := buildTools(tt.tools)
+
+			if len(result) != tt.expectedLen {
+				t.Errorf("%s: got %d tool declarations, want %d", tt.description, len(result), tt.expectedLen)
+			}
+
+			// 验证function declarations存在
+			if len(result) > 0 && result[0].FunctionDeclarations != nil {
+				if len(result[0].FunctionDeclarations) != len(tt.tools) {
+					t.Errorf("%s: got %d function declarations, want %d",
+						tt.description, len(result[0].FunctionDeclarations), len(tt.tools))
+				}
+			}
+		})
+	}
+}

backend/internal/pkg/claude/constants.go

@@ -16,6 +16,12 @@ const DefaultBetaHeader = BetaClaudeCode + "," + BetaOAuth + "," + BetaInterleav
 // HaikuBetaHeader Haiku 模型使用的 anthropic-beta header（不需要 claude-code beta）
 const HaikuBetaHeader = BetaOAuth + "," + BetaInterleavedThinking
 
+// ApiKeyBetaHeader API-key 账号建议使用的 anthropic-beta header（不包含 oauth）
+const ApiKeyBetaHeader = BetaClaudeCode + "," + BetaInterleavedThinking + "," + BetaFineGrainedToolStreaming
+
+// ApiKeyHaikuBetaHeader Haiku 模型在 API-key 账号下使用的 anthropic-beta header（不包含 oauth / claude-code）
+const ApiKeyHaikuBetaHeader = BetaInterleavedThinking
+
 // Claude Code 客户端默认请求头
 var DefaultHeaders = map[string]string{
 	"User-Agent":                                "claude-cli/2.0.62 (external, cli)",

backend/internal/service/antigravity_gateway_service.go

@@ -358,6 +358,15 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 		return nil, fmt.Errorf("transform request: %w", err)
 	}
 
+	// 调试：记录转换后的请求体（仅记录前 2000 字符）
+	if bodyJSON, err := json.Marshal(geminiBody); err == nil {
+		truncated := string(bodyJSON)
+		if len(truncated) > 2000 {
+			truncated = truncated[:2000] + "..."
+		}
+		log.Printf("[Debug] Transformed Gemini request: %s", truncated)
+	}
+
 	// 构建上游 action
 	action := "generateContent"
 	if claudeReq.Stream {

backend/internal/service/gateway_service.go

@@ -19,6 +19,7 @@ import (
 	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/claude"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
+	"github.com/tidwall/gjson"
 	"github.com/tidwall/sjson"
 
 	"github.com/gin-gonic/gin"
@@ -684,6 +685,30 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 
 	// 处理错误响应（不可重试的错误）
 	if resp.StatusCode >= 400 {
+		// 可选：对部分 400 触发 failover（默认关闭以保持语义）
+		if resp.StatusCode == 400 && s.cfg != nil && s.cfg.Gateway.FailoverOn400 {
+			respBody, readErr := io.ReadAll(resp.Body)
+			if readErr != nil {
+				// ReadAll failed, fall back to normal error handling without consuming the stream
+				return s.handleErrorResponse(ctx, resp, c, account)
+			}
+			_ = resp.Body.Close()
+			resp.Body = io.NopCloser(bytes.NewReader(respBody))
+
+			if s.shouldFailoverOn400(respBody) {
+				if s.cfg.Gateway.LogUpstreamErrorBody {
+					log.Printf(
+						"Account %d: 400 error, attempting failover: %s",
+						account.ID,
+						truncateForLog(respBody, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
+					)
+				} else {
+					log.Printf("Account %d: 400 error, attempting failover", account.ID)
+				}
+				s.handleFailoverSideEffects(ctx, resp, account)
+				return nil, &UpstreamFailoverError{StatusCode: resp.StatusCode}
+			}
+		}
 		return s.handleErrorResponse(ctx, resp, c, account)
 	}
 
@@ -786,6 +811,13 @@ func (s *GatewayService) buildUpstreamRequest(ctx context.Context, c *gin.Contex
 	// 处理anthropic-beta header（OAuth账号需要特殊处理）
 	if tokenType == "oauth" {
 		req.Header.Set("anthropic-beta", s.getBetaHeader(modelID, c.GetHeader("anthropic-beta")))
+	} else if s.cfg != nil && s.cfg.Gateway.InjectBetaForApiKey && req.Header.Get("anthropic-beta") == "" {
+		// API-key：仅在请求显式使用 beta 特性且客户端未提供时，按需补齐（默认关闭）
+		if requestNeedsBetaFeatures(body) {
+			if beta := defaultApiKeyBetaHeader(body); beta != "" {
+				req.Header.Set("anthropic-beta", beta)
+			}
+		}
 	}
 
 	return req, nil
@@ -838,6 +870,83 @@ func (s *GatewayService) getBetaHeader(modelID string, clientBetaHeader string)
 	return claude.DefaultBetaHeader
 }
 
+func requestNeedsBetaFeatures(body []byte) bool {
+	tools := gjson.GetBytes(body, "tools")
+	if tools.Exists() && tools.IsArray() && len(tools.Array()) > 0 {
+		return true
+	}
+	if strings.EqualFold(gjson.GetBytes(body, "thinking.type").String(), "enabled") {
+		return true
+	}
+	return false
+}
+
+func defaultApiKeyBetaHeader(body []byte) string {
+	modelID := gjson.GetBytes(body, "model").String()
+	if strings.Contains(strings.ToLower(modelID), "haiku") {
+		return claude.ApiKeyHaikuBetaHeader
+	}
+	return claude.ApiKeyBetaHeader
+}
+
+func truncateForLog(b []byte, maxBytes int) string {
+	if maxBytes <= 0 {
+		maxBytes = 2048
+	}
+	if len(b) > maxBytes {
+		b = b[:maxBytes]
+	}
+	s := string(b)
+	// 保持一行，避免污染日志格式
+	s = strings.ReplaceAll(s, "\n", "\\n")
+	s = strings.ReplaceAll(s, "\r", "\\r")
+	return s
+}
+
+func (s *GatewayService) shouldFailoverOn400(respBody []byte) bool {
+	// 只对“可能是兼容性差异导致”的 400 允许切换，避免无意义重试。
+	// 默认保守：无法识别则不切换。
+	msg := strings.ToLower(strings.TrimSpace(extractUpstreamErrorMessage(respBody)))
+	if msg == "" {
+		return false
+	}
+
+	// 缺少/错误的 beta header：换账号/链路可能成功（尤其是混合调度时）。
+	// 更精确匹配 beta 相关的兼容性问题，避免误触发切换。
+	if strings.Contains(msg, "anthropic-beta") ||
+		strings.Contains(msg, "beta feature") ||
+		strings.Contains(msg, "requires beta") {
+		return true
+	}
+
+	// thinking/tool streaming 等兼容性约束（常见于中间转换链路）
+	if strings.Contains(msg, "thinking") || strings.Contains(msg, "thought_signature") || strings.Contains(msg, "signature") {
+		return true
+	}
+	if strings.Contains(msg, "tool_use") || strings.Contains(msg, "tool_result") || strings.Contains(msg, "tools") {
+		return true
+	}
+
+	return false
+}
+
+func extractUpstreamErrorMessage(body []byte) string {
+	// Claude 风格：{"type":"error","error":{"type":"...","message":"..."}}
+	if m := gjson.GetBytes(body, "error.message").String(); strings.TrimSpace(m) != "" {
+		inner := strings.TrimSpace(m)
+		// 有些上游会把完整 JSON 作为字符串塞进 message
+		if strings.HasPrefix(inner, "{") {
+			if innerMsg := gjson.Get(inner, "error.message").String(); strings.TrimSpace(innerMsg) != "" {
+				return innerMsg
+			}
+		}
+		return m
+	}
+
+	// 兜底：尝试顶层 message
+	return gjson.GetBytes(body, "message").String()
+}
+
 func (s *GatewayService) handleErrorResponse(ctx context.Context, resp *http.Response, c *gin.Context, account *Account) (*ForwardResult, error) {
 	body, _ := io.ReadAll(resp.Body)
 
@@ -850,6 +959,16 @@ func (s *GatewayService) handleErrorResponse(ctx context.Context, resp *http.Res
 
 	switch resp.StatusCode {
 	case 400:
+		// 仅记录上游错误摘要（避免输出请求内容）；需要时可通过配置打开
+		if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
+			log.Printf(
+				"Upstream 400 error (account=%d platform=%s type=%s): %s",
+				account.ID,
+				account.Platform,
+				account.Type,
+				truncateForLog(body, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
+			)
+		}
 		c.Data(http.StatusBadRequest, "application/json", body)
 		return nil, fmt.Errorf("upstream error: %d", resp.StatusCode)
 	case 401:
@@ -1329,6 +1448,18 @@ func (s *GatewayService) ForwardCountTokens(ctx context.Context, c *gin.Context,
 		// 标记账号状态（429/529等）
 		s.rateLimitService.HandleUpstreamError(ctx, account, resp.StatusCode, resp.Header, respBody)
 
+		// 记录上游错误摘要便于排障（不回显请求内容）
+		if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
+			log.Printf(
+				"count_tokens upstream error %d (account=%d platform=%s type=%s): %s",
+				resp.StatusCode,
+				account.ID,
+				account.Platform,
+				account.Type,
+				truncateForLog(respBody, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
+			)
+		}
+
 		// 返回简化的错误响应
 		errMsg := "Upstream request failed"
 		switch resp.StatusCode {
@@ -1409,6 +1540,13 @@ func (s *GatewayService) buildCountTokensRequest(ctx context.Context, c *gin.Con
 	// OAuth 账号：处理 anthropic-beta header
 	if tokenType == "oauth" {
 		req.Header.Set("anthropic-beta", s.getBetaHeader(modelID, c.GetHeader("anthropic-beta")))
+	} else if s.cfg != nil && s.cfg.Gateway.InjectBetaForApiKey && req.Header.Get("anthropic-beta") == "" {
+		// API-key：与 messages 同步的按需 beta 注入（默认关闭）
+		if requestNeedsBetaFeatures(body) {
+			if beta := defaultApiKeyBetaHeader(body); beta != "" {
+				req.Header.Set("anthropic-beta", beta)
+			}
+		}
 	}
 
 	return req, nil

backend/internal/service/gemini_messages_compat_service.go

@@ -2278,11 +2278,13 @@ func convertClaudeToolsToGeminiTools(tools any) []any {
 				"properties": map[string]any{},
 			}
 		}
+		// 清理 JSON Schema
+		cleanedParams := cleanToolSchema(params)
 
 		funcDecls = append(funcDecls, map[string]any{
 			"name":        name,
 			"description": desc,
-			"parameters":  params,
+			"parameters":  cleanedParams,
 		})
 	}
 
@@ -2296,6 +2298,41 @@ func convertClaudeToolsToGeminiTools(tools any) []any {
 	}
 }
 
+// cleanToolSchema 清理工具的 JSON Schema，移除 Gemini 不支持的字段
+func cleanToolSchema(schema any) any {
+	if schema == nil {
+		return nil
+	}
+
+	switch v := schema.(type) {
+	case map[string]any:
+		cleaned := make(map[string]any)
+		for key, value := range v {
+			// 跳过不支持的字段
+			if key == "$schema" || key == "$id" || key == "$ref" ||
+				key == "additionalProperties" || key == "minLength" ||
+				key == "maxLength" || key == "minItems" || key == "maxItems" {
+				continue
+			}
+			// 递归清理嵌套对象
+			cleaned[key] = cleanToolSchema(value)
+		}
+		// 规范化 type 字段为大写
+		if typeVal, ok := cleaned["type"].(string); ok {
+			cleaned["type"] = strings.ToUpper(typeVal)
+		}
+		return cleaned
+	case []any:
+		cleaned := make([]any, len(v))
+		for i, item := range v {
+			cleaned[i] = cleanToolSchema(item)
+		}
+		return cleaned
+	default:
+		return v
+	}
+}
+
 func convertClaudeGenerationConfig(req map[string]any) map[string]any {
 	out := make(map[string]any)
 	if mt, ok := asInt(req["max_tokens"]); ok && mt > 0 {

backend/internal/service/gemini_messages_compat_service_test.go

@@ -0,0 +1,128 @@
+package service
+
+import (
+	"testing"
+)
+
+// TestConvertClaudeToolsToGeminiTools_CustomType 测试custom类型工具转换
+func TestConvertClaudeToolsToGeminiTools_CustomType(t *testing.T) {
+	tests := []struct {
+		name        string
+		tools       any
+		expectedLen int
+		description string
+	}{
+		{
+			name: "Standard tools",
+			tools: []any{
+				map[string]any{
+					"name":         "get_weather",
+					"description":  "Get weather info",
+					"input_schema": map[string]any{"type": "object"},
+				},
+			},
+			expectedLen: 1,
+			description: "标准工具格式应该正常转换",
+		},
+		{
+			name: "Custom type tool (MCP format)",
+			tools: []any{
+				map[string]any{
+					"type": "custom",
+					"name": "mcp_tool",
+					"custom": map[string]any{
+						"description":  "MCP tool description",
+						"input_schema": map[string]any{"type": "object"},
+					},
+				},
+			},
+			expectedLen: 1,
+			description: "Custom类型工具应该从custom字段读取",
+		},
+		{
+			name: "Mixed standard and custom tools",
+			tools: []any{
+				map[string]any{
+					"name":         "standard_tool",
+					"description":  "Standard",
+					"input_schema": map[string]any{"type": "object"},
+				},
+				map[string]any{
+					"type": "custom",
+					"name": "custom_tool",
+					"custom": map[string]any{
+						"description":  "Custom",
+						"input_schema": map[string]any{"type": "object"},
+					},
+				},
+			},
+			expectedLen: 1,
+			description: "混合工具应该都能正确转换",
+		},
+		{
+			name: "Custom tool without custom field",
+			tools: []any{
+				map[string]any{
+					"type": "custom",
+					"name": "invalid_custom",
+					// 缺少 custom 字段
+				},
+			},
+			expectedLen: 0, // 应该被跳过
+			description: "缺少custom字段的custom工具应该被跳过",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := convertClaudeToolsToGeminiTools(tt.tools)
+
+			if tt.expectedLen == 0 {
+				if result != nil {
+					t.Errorf("%s: expected nil result, got %v", tt.description, result)
+				}
+				return
+			}
+
+			if result == nil {
+				t.Fatalf("%s: expected non-nil result", tt.description)
+			}
+
+			if len(result) != 1 {
+				t.Errorf("%s: expected 1 tool declaration, got %d", tt.description, len(result))
+				return
+			}
+
+			toolDecl, ok := result[0].(map[string]any)
+			if !ok {
+				t.Fatalf("%s: result[0] is not map[string]any", tt.description)
+			}
+
+			funcDecls, ok := toolDecl["functionDeclarations"].([]any)
+			if !ok {
+				t.Fatalf("%s: functionDeclarations is not []any", tt.description)
+			}
+
+			toolsArr, _ := tt.tools.([]any)
+			expectedFuncCount := 0
+			for _, tool := range toolsArr {
+				toolMap, _ := tool.(map[string]any)
+				if toolMap["name"] != "" {
+					// 检查是否为有效的custom工具
+					if toolMap["type"] == "custom" {
+						if toolMap["custom"] != nil {
+							expectedFuncCount++
+						}
+					} else {
+						expectedFuncCount++
+					}
+				}
+			}
+
+			if len(funcDecls) != expectedFuncCount {
+				t.Errorf("%s: expected %d function declarations, got %d",
+					tt.description, expectedFuncCount, len(funcDecls))
+			}
+		})
+	}
+}

backend/internal/service/gemini_oauth_service.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -163,6 +164,45 @@ type GeminiTokenInfo struct {
 	Scope        string `json:"scope,omitempty"`
 	ProjectID    string `json:"project_id,omitempty"`
 	OAuthType    string `json:"oauth_type,omitempty"` // "code_assist" 或 "ai_studio"
+	TierID       string `json:"tier_id,omitempty"`    // Gemini Code Assist tier: LEGACY/PRO/ULTRA
+}
+
+// validateTierID validates tier_id format and length
+func validateTierID(tierID string) error {
+	if tierID == "" {
+		return nil // Empty is allowed
+	}
+	if len(tierID) > 64 {
+		return fmt.Errorf("tier_id exceeds maximum length of 64 characters")
+	}
+	// Allow alphanumeric, underscore, hyphen, and slash (for tier paths)
+	if !regexp.MustCompile(`^[a-zA-Z0-9_/-]+$`).MatchString(tierID) {
+		return fmt.Errorf("tier_id contains invalid characters")
+	}
+	return nil
+}
+
+// extractTierIDFromAllowedTiers extracts tierID from LoadCodeAssist response
+// Prioritizes IsDefault tier, falls back to first non-empty tier
+func extractTierIDFromAllowedTiers(allowedTiers []geminicli.AllowedTier) string {
+	tierID := "LEGACY"
+	// First pass: look for default tier
+	for _, tier := range allowedTiers {
+		if tier.IsDefault && strings.TrimSpace(tier.ID) != "" {
+			tierID = strings.TrimSpace(tier.ID)
+			break
+		}
+	}
+	// Second pass: if still LEGACY, take first non-empty tier
+	if tierID == "LEGACY" {
+		for _, tier := range allowedTiers {
+			if strings.TrimSpace(tier.ID) != "" {
+				tierID = strings.TrimSpace(tier.ID)
+				break
+			}
+		}
+	}
+	return tierID
 }
 
 func (s *GeminiOAuthService) ExchangeCode(ctx context.Context, input *GeminiExchangeCodeInput) (*GeminiTokenInfo, error) {
@@ -223,13 +263,14 @@ func (s *GeminiOAuthService) ExchangeCode(ctx context.Context, input *GeminiExch
 	expiresAt := time.Now().Unix() + tokenResp.ExpiresIn - 300
 
 	projectID := sessionProjectID
+	var tierID string
 
 	// 对于 code_assist 模式，project_id 是必需的
 	// 对于 ai_studio 模式，project_id 是可选的（不影响使用 AI Studio API）
 	if oauthType == "code_assist" {
 		if projectID == "" {
 			var err error
-			projectID, err = s.fetchProjectID(ctx, tokenResp.AccessToken, proxyURL)
+			projectID, tierID, err = s.fetchProjectID(ctx, tokenResp.AccessToken, proxyURL)
 			if err != nil {
 				// 记录警告但不阻断流程，允许后续补充 project_id
 				fmt.Printf("[GeminiOAuth] Warning: Failed to fetch project_id during token exchange: %v\n", err)
@@ -248,6 +289,7 @@ func (s *GeminiOAuthService) ExchangeCode(ctx context.Context, input *GeminiExch
 		ExpiresAt:    expiresAt,
 		Scope:        tokenResp.Scope,
 		ProjectID:    projectID,
+		TierID:       tierID,
 		OAuthType:    oauthType,
 	}, nil
 }
@@ -357,7 +399,7 @@ func (s *GeminiOAuthService) RefreshAccountToken(ctx context.Context, account *A
 	// For Code Assist, project_id is required. Auto-detect if missing.
 	// For AI Studio OAuth, project_id is optional and should not block refresh.
 	if oauthType == "code_assist" && strings.TrimSpace(tokenInfo.ProjectID) == "" {
-		projectID, err := s.fetchProjectID(ctx, tokenInfo.AccessToken, proxyURL)
+		projectID, tierID, err := s.fetchProjectID(ctx, tokenInfo.AccessToken, proxyURL)
 		if err != nil {
 			return nil, fmt.Errorf("failed to auto-detect project_id: %w", err)
 		}
@@ -366,6 +408,7 @@ func (s *GeminiOAuthService) RefreshAccountToken(ctx context.Context, account *A
 			return nil, fmt.Errorf("failed to auto-detect project_id: empty result")
 		}
 		tokenInfo.ProjectID = projectID
+		tokenInfo.TierID = tierID
 	}
 
 	return tokenInfo, nil
@@ -388,6 +431,13 @@ func (s *GeminiOAuthService) BuildAccountCredentials(tokenInfo *GeminiTokenInfo)
 	if tokenInfo.ProjectID != "" {
 		creds["project_id"] = tokenInfo.ProjectID
 	}
+	if tokenInfo.TierID != "" {
+		// Validate tier_id before storing
+		if err := validateTierID(tokenInfo.TierID); err == nil {
+			creds["tier_id"] = tokenInfo.TierID
+		}
+		// Silently skip invalid tier_id (don't block account creation)
+	}
 	if tokenInfo.OAuthType != "" {
 		creds["oauth_type"] = tokenInfo.OAuthType
 	}
@@ -398,34 +448,26 @@ func (s *GeminiOAuthService) Stop() {
 	s.sessionStore.Stop()
 }
 
-func (s *GeminiOAuthService) fetchProjectID(ctx context.Context, accessToken, proxyURL string) (string, error) {
+func (s *GeminiOAuthService) fetchProjectID(ctx context.Context, accessToken, proxyURL string) (string, string, error) {
 	if s.codeAssist == nil {
-		return "", errors.New("code assist client not configured")
+		return "", "", errors.New("code assist client not configured")
 	}
 
 	loadResp, loadErr := s.codeAssist.LoadCodeAssist(ctx, accessToken, proxyURL, nil)
+
+	// Extract tierID from response (works whether CloudAICompanionProject is set or not)
+	tierID := "LEGACY"
+	if loadResp != nil {
+		tierID = extractTierIDFromAllowedTiers(loadResp.AllowedTiers)
+	}
+
+	// If LoadCodeAssist returned a project, use it
 	if loadErr == nil && loadResp != nil && strings.TrimSpace(loadResp.CloudAICompanionProject) != "" {
-		return strings.TrimSpace(loadResp.CloudAICompanionProject), nil
+		return strings.TrimSpace(loadResp.CloudAICompanionProject), tierID, nil
 	}
 
 	// Pick tier from allowedTiers; if no default tier is marked, pick the first non-empty tier ID.
-	tierID := "LEGACY"
-	if loadResp != nil {
-		for _, tier := range loadResp.AllowedTiers {
-			if tier.IsDefault && strings.TrimSpace(tier.ID) != "" {
-				tierID = strings.TrimSpace(tier.ID)
-				break
-			}
-		}
-		if strings.TrimSpace(tierID) == "" || tierID == "LEGACY" {
-			for _, tier := range loadResp.AllowedTiers {
-				if strings.TrimSpace(tier.ID) != "" {
-					tierID = strings.TrimSpace(tier.ID)
-					break
-				}
-			}
-		}
-	}
+	// (tierID already extracted above, reuse it)
 
 	req := &geminicli.OnboardUserRequest{
 		TierID: tierID,
@@ -443,39 +485,39 @@ func (s *GeminiOAuthService) fetchProjectID(ctx context.Context, accessToken, pr
 			// If Code Assist onboarding fails (e.g. INVALID_ARGUMENT), fallback to Cloud Resource Manager projects.
 			fallback, fbErr := fetchProjectIDFromResourceManager(ctx, accessToken, proxyURL)
 			if fbErr == nil && strings.TrimSpace(fallback) != "" {
-				return strings.TrimSpace(fallback), nil
+				return strings.TrimSpace(fallback), tierID, nil
 			}
-			return "", err
+			return "", "", err
 		}
 		if resp.Done {
 			if resp.Response != nil && resp.Response.CloudAICompanionProject != nil {
 				switch v := resp.Response.CloudAICompanionProject.(type) {
 				case string:
-					return strings.TrimSpace(v), nil
+					return strings.TrimSpace(v), tierID, nil
 				case map[string]any:
 					if id, ok := v["id"].(string); ok {
-						return strings.TrimSpace(id), nil
+						return strings.TrimSpace(id), tierID, nil
 					}
 				}
 			}
 
 			fallback, fbErr := fetchProjectIDFromResourceManager(ctx, accessToken, proxyURL)
 			if fbErr == nil && strings.TrimSpace(fallback) != "" {
-				return strings.TrimSpace(fallback), nil
+				return strings.TrimSpace(fallback), tierID, nil
 			}
-			return "", errors.New("onboardUser completed but no project_id returned")
+			return "", "", errors.New("onboardUser completed but no project_id returned")
 		}
 		time.Sleep(2 * time.Second)
 	}
 
 	fallback, fbErr := fetchProjectIDFromResourceManager(ctx, accessToken, proxyURL)
 	if fbErr == nil && strings.TrimSpace(fallback) != "" {
-		return strings.TrimSpace(fallback), nil
+		return strings.TrimSpace(fallback), tierID, nil
 	}
 	if loadErr != nil {
-		return "", fmt.Errorf("loadCodeAssist failed (%v) and onboardUser timeout after %d attempts", loadErr, maxAttempts)
+		return "", "", fmt.Errorf("loadCodeAssist failed (%v) and onboardUser timeout after %d attempts", loadErr, maxAttempts)
 	}
-	return "", fmt.Errorf("onboardUser timeout after %d attempts", maxAttempts)
+	return "", "", fmt.Errorf("onboardUser timeout after %d attempts", maxAttempts)
 }
 
 type googleCloudProject struct {

backend/internal/service/gemini_token_provider.go

@@ -112,7 +112,7 @@ func (p *GeminiTokenProvider) GetAccessToken(ctx context.Context, account *Accou
 			}
 		}
 
-		detected, err := p.geminiOAuthService.fetchProjectID(ctx, accessToken, proxyURL)
+		detected, tierID, err := p.geminiOAuthService.fetchProjectID(ctx, accessToken, proxyURL)
 		if err != nil {
 			log.Printf("[GeminiTokenProvider] Auto-detect project_id failed: %v, fallback to AI Studio API mode", err)
 			return accessToken, nil
@@ -123,6 +123,9 @@ func (p *GeminiTokenProvider) GetAccessToken(ctx context.Context, account *Accou
 				account.Credentials = make(map[string]any)
 			}
 			account.Credentials["project_id"] = detected
+			if tierID != "" {
+				account.Credentials["tier_id"] = tierID
+			}
 			_ = p.accountRepo.Update(ctx, account)
 		}
 	}

deploy/config.example.yaml

@@ -122,6 +122,21 @@ pricing:
   # Hash check interval in minutes
   hash_check_interval_minutes: 10
 
+# =============================================================================
+# Gateway (Optional)
+# =============================================================================
+gateway:
+  # Wait time (in seconds) for upstream response headers (streaming body not affected)
+  response_header_timeout: 300
+  # Log upstream error response body summary (safe/truncated; does not log request content)
+  log_upstream_error_body: false
+  # Max bytes to log from upstream error body
+  log_upstream_error_body_max_bytes: 2048
+  # Auto inject anthropic-beta for API-key accounts when needed (default off)
+  inject_beta_for_apikey: false
+  # Allow failover on selected 400 errors (default off)
+  failover_on_400: false
+
 # =============================================================================
 # Gemini OAuth (Required for Gemini accounts)
 # =============================================================================

frontend/package-lock.json

@@ -952,6 +952,7 @@
       "integrity": "sha512-N2clP5pJhB2YnZJ3PIHFk5RkygRX5WO/5f0WC08tp0wd+sv0rsJk3MqWn3CbNmT2J505a5336jaQj4ph1AdMug==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "undici-types": "~6.21.0"
       }
@@ -1367,6 +1368,7 @@
         }
       ],
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "baseline-browser-mapping": "^2.9.0",
         "caniuse-lite": "^1.0.30001759",
@@ -1443,6 +1445,7 @@
       "resolved": "https://registry.npmmirror.com/chart.js/-/chart.js-4.5.1.tgz",
       "integrity": "sha512-GIjfiT9dbmHRiYi6Nl2yFCq7kkwdkp1W/lp2J99rX0yo9tgJGn3lKQATztIjb5tVtevcBtIdICNWqlq5+E8/Pw==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@kurkle/color": "^0.3.0"
       },
@@ -2040,6 +2043,7 @@
       "integrity": "sha512-/imKNG4EbWNrVjoNC/1H5/9GFy+tqjGBHCaSsN+P2RnPqjsLmv6UD3Ej+Kj8nBWaRAwyk7kK5ZUc+OEatnTR3A==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "bin": {
         "jiti": "bin/jiti.js"
       }
@@ -2348,6 +2352,7 @@
         }
       ],
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "nanoid": "^3.3.11",
         "picocolors": "^1.1.1",
@@ -2821,6 +2826,7 @@
       "integrity": "sha512-5gTmgEY/sqK6gFXLIsQNH19lWb4ebPDLA4SdLP7dsWkIXHWlG66oPuVvXSGFPppYZz8ZDZq0dYYrbHfBCVUb1Q==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "engines": {
         "node": ">=12"
       },
@@ -2854,6 +2860,7 @@
       "integrity": "sha512-hjcS1mhfuyi4WW8IWtjP7brDrG2cuDZukyrYrSauoXGNgx0S7zceP07adYkJycEr56BOUTNPzbInooiN3fn1qw==",
       "devOptional": true,
       "license": "Apache-2.0",
+      "peer": true,
       "bin": {
         "tsc": "bin/tsc",
         "tsserver": "bin/tsserver"
@@ -2926,6 +2933,7 @@
       "integrity": "sha512-o5a9xKjbtuhY6Bi5S3+HvbRERmouabWbyUcpXXUA1u+GNUKoROi9byOJ8M0nHbHYHkYICiMlqxkg1KkYmm25Sw==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "esbuild": "^0.21.3",
         "postcss": "^8.4.43",
@@ -3097,6 +3105,7 @@
       "resolved": "https://registry.npmmirror.com/vue/-/vue-3.5.25.tgz",
       "integrity": "sha512-YLVdgv2K13WJ6n+kD5owehKtEXwdwXuj2TTyJMsO7pSeKw2bfRNZGjhB7YzrpbMYj5b5QsUebHpOqR3R3ziy/g==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@vue/compiler-dom": "3.5.25",
         "@vue/compiler-sfc": "3.5.25",
@@ -3190,6 +3199,7 @@
       "integrity": "sha512-P7OP77b2h/Pmk+lZdJ0YWs+5tJ6J2+uOQPo7tlBnY44QqQSPYvS0qVT4wqDJgwrZaLe47etJLLQRFia71GYITw==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@volar/typescript": "2.4.15",
         "@vue/language-core": "2.2.12"

frontend/src/components/account/AccountStatusIndicator.vue

@@ -83,6 +83,14 @@
         ></div>
       </div>
     </div>
+
+    <!-- Tier Indicator -->
+    <span
+      v-if="tierDisplay"
+      class="inline-flex items-center rounded bg-blue-100 px-1.5 py-0.5 text-xs font-medium text-blue-700 dark:bg-blue-900/30 dark:text-blue-400"
+    >
+      {{ tierDisplay }}
+    </span>
   </div>
 </template>
 
@@ -140,4 +148,23 @@ const statusText = computed(() => {
   return props.account.status
 })
 
+// Computed: tier display
+const tierDisplay = computed(() => {
+  const credentials = props.account.credentials as Record<string, any> | undefined
+  const tierId = credentials?.tier_id
+  if (!tierId || tierId === 'unknown') return null
+
+  const tierMap: Record<string, string> = {
+    'free': 'Free',
+    'payg': 'Pay-as-you-go',
+    'pay-as-you-go': 'Pay-as-you-go',
+    'enterprise': 'Enterprise',
+    'LEGACY': 'Legacy',
+    'PRO': 'Pro',
+    'ULTRA': 'Ultra'
+  }
+
+  return tierMap[tierId] || tierId
+})
+
 </script>