fix: 修复非CC客户端OAuth伪装被Anthropic检测为第三方应用的问题

commit f3aa54b 的 rewriteSystemForNonClaudeCode 未能通过 Anthropic 第三方检测，
根因是两个关键信号与真实 Claude Code 不一致：

1. anthropic-beta 头缺少 claude-code-20250219：伪装路径主动将该 beta
   加入 drop set 并移除，但 Anthropic 依赖此 beta 识别 Claude Code 请求。
   修复：非 haiku 模型的伪装请求强制包含 claude-code beta。

2. system 字段使用 string 格式而非 array+cache_control：真实 Claude Code
   始终以 [{type,text,cache_control:{type:"ephemeral"}}] 发送 system，
   string 格式成为第三方检测信号。
   修复：rewriteSystemForNonClaudeCode 改为注入 array 格式。

附带调整：stripSystemCacheControl 按 system 是否被重写动态决定，
重写时保留 CC prompt 的 cache_control，未重写时（haiku/已含CC前缀）
保持原有剥离行为。

backend/internal/service/gateway_anthropic_apikey_passthrough_test.go

@@ -761,7 +761,9 @@ func TestGatewayService_AnthropicOAuth_ForwardPreservesBillingHeaderSystemBlock(
 
 			system := gjson.GetBytes(upstream.lastBody, "system")
 			require.True(t, system.Exists())
-			require.Equal(t, claudeCodeSystemPrompt, system.String())
+			require.True(t, system.IsArray(), "system should be an array")
+			require.Equal(t, claudeCodeSystemPrompt, system.Array()[0].Get("text").String())
+			require.Equal(t, "ephemeral", system.Array()[0].Get("cache_control.type").String())
 
 			// 原始 system prompt 应迁移至 messages 中
 			messages := gjson.GetBytes(upstream.lastBody, "messages")

backend/internal/service/gateway_prompt_test.go

@@ -284,7 +284,7 @@ func TestRewriteSystemForNonClaudeCode(t *testing.T) {
 		name             string
 		body             string
 		system           any
-		wantSystemStr    string // system 应为纯字符串
+		wantSystemText   string // system array 第一个 block 的 text
 		wantMessagesLen  int    // messages 数组长度
 		wantFirstMsgRole string // 第一条消息的 role
 		wantFirstMsgText string // 第一条消息的 content[0].text
@@ -294,21 +294,21 @@ func TestRewriteSystemForNonClaudeCode(t *testing.T) {
 			name:            "nil system - no messages injected",
 			body:            `{"model":"claude-3","messages":[{"role":"user","content":"hello"}]}`,
 			system:          nil,
-			wantSystemStr:   claudeCodeSystemPrompt,
+			wantSystemText:  claudeCodeSystemPrompt,
 			wantMessagesLen: 1, // 原始 1 条消息，不注入
 		},
 		{
 			name:            "empty string system - no messages injected",
 			body:            `{"model":"claude-3","messages":[{"role":"user","content":"hello"}]}`,
 			system:          "",
-			wantSystemStr:   claudeCodeSystemPrompt,
+			wantSystemText:  claudeCodeSystemPrompt,
 			wantMessagesLen: 1,
 		},
 		{
 			name:             "custom string system - migrated to messages",
 			body:             `{"model":"claude-3","messages":[{"role":"user","content":"hello"}]}`,
 			system:           "You are a personal assistant running inside OpenClaw.",
-			wantSystemStr:    claudeCodeSystemPrompt,
+			wantSystemText:   claudeCodeSystemPrompt,
 			wantMessagesLen:  3, // instruction + ack + original
 			wantFirstMsgRole: "user",
 			wantFirstMsgText: "[System Instructions]\nYou are a personal assistant running inside OpenClaw.",
@@ -318,7 +318,7 @@ func TestRewriteSystemForNonClaudeCode(t *testing.T) {
 			name:            "system equals Claude Code prompt - no messages injected",
 			body:            `{"model":"claude-3","messages":[{"role":"user","content":"hello"}]}`,
 			system:          claudeCodeSystemPrompt,
-			wantSystemStr:   claudeCodeSystemPrompt,
+			wantSystemText:  claudeCodeSystemPrompt,
 			wantMessagesLen: 1,
 		},
 		{
@@ -328,7 +328,7 @@ func TestRewriteSystemForNonClaudeCode(t *testing.T) {
 				map[string]any{"type": "text", "text": "First instruction"},
 				map[string]any{"type": "text", "text": "Second instruction"},
 			},
-			wantSystemStr:    claudeCodeSystemPrompt,
+			wantSystemText:   claudeCodeSystemPrompt,
 			wantMessagesLen:  3,
 			wantFirstMsgRole: "user",
 			wantFirstMsgText: "[System Instructions]\nFirst instruction\n\nSecond instruction",
@@ -338,14 +338,14 @@ func TestRewriteSystemForNonClaudeCode(t *testing.T) {
 			name:            "empty array system - no messages injected",
 			body:            `{"model":"claude-3","messages":[{"role":"user","content":"hello"}]}`,
 			system:          []any{},
-			wantSystemStr:   claudeCodeSystemPrompt,
+			wantSystemText:  claudeCodeSystemPrompt,
 			wantMessagesLen: 1,
 		},
 		{
 			name:             "json.RawMessage string system",
 			body:             `{"model":"claude-3","system":"Custom prompt","messages":[{"role":"user","content":"hello"}]}`,
 			system:           json.RawMessage(`"Custom prompt"`),
-			wantSystemStr:    claudeCodeSystemPrompt,
+			wantSystemText:   claudeCodeSystemPrompt,
 			wantMessagesLen:  3,
 			wantFirstMsgRole: "user",
 			wantFirstMsgText: "[System Instructions]\nCustom prompt",
@@ -355,14 +355,14 @@ func TestRewriteSystemForNonClaudeCode(t *testing.T) {
 			name:            "json.RawMessage nil system",
 			body:            `{"model":"claude-3","messages":[{"role":"user","content":"hello"}]}`,
 			system:          json.RawMessage(nil),
-			wantSystemStr:   claudeCodeSystemPrompt,
+			wantSystemText:  claudeCodeSystemPrompt,
 			wantMessagesLen: 1,
 		},
 		{
 			name:             "multiple original messages preserved",
 			body:             `{"model":"claude-3","messages":[{"role":"user","content":"msg1"},{"role":"assistant","content":"resp1"},{"role":"user","content":"msg2"}]}`,
 			system:           "Be helpful",
-			wantSystemStr:    claudeCodeSystemPrompt,
+			wantSystemText:   claudeCodeSystemPrompt,
 			wantMessagesLen:  5, // 2 injected + 3 original
 			wantFirstMsgRole: "user",
 			wantFirstMsgText: "[System Instructions]\nBe helpful",
@@ -378,10 +378,17 @@ func TestRewriteSystemForNonClaudeCode(t *testing.T) {
 			err := json.Unmarshal(result, &parsed)
 			require.NoError(t, err)
 
-			// system 应为纯字符串
+			// system 应为 array 格式: [{type: "text", text: "...", cache_control: {type: "ephemeral"}}]
-			systemVal, ok := parsed["system"].(string)
+			systemArr, ok := parsed["system"].([]any)
-			require.True(t, ok, "system should be a string, got %T", parsed["system"])
+			require.True(t, ok, "system should be an array, got %T", parsed["system"])
-			require.Equal(t, tt.wantSystemStr, systemVal)
+			require.Len(t, systemArr, 1, "system array should have exactly 1 block")
+			systemBlock, ok := systemArr[0].(map[string]any)
+			require.True(t, ok)
+			require.Equal(t, "text", systemBlock["type"])
+			require.Equal(t, tt.wantSystemText, systemBlock["text"])
+			cc, ok := systemBlock["cache_control"].(map[string]any)
+			require.True(t, ok, "system block should have cache_control")
+			require.Equal(t, "ephemeral", cc["type"])
 
 			// 检查 messages
 			messages, ok := parsed["messages"].([]any)

backend/internal/service/gateway_service.go

@@ -3739,8 +3739,17 @@ func rewriteSystemForNonClaudeCode(body []byte, system any) []byte {
 		originalSystemText = strings.Join(parts, "\n\n")
 	}
 
-	// 2. 将 system 替换为 Claude Code 标准提示词（纯字符串，通过 Anthropic 检测）
+	// 2. 将 system 替换为 Claude Code 标准提示词（array 格式，与真实 Claude Code 一致）
-	out, ok := setJSONValueBytes(body, "system", claudeCodeSystemPrompt)
+	//    真实 Claude Code 始终以 [{type: "text", text: "...", cache_control: {type: "ephemeral"}}] 发送 system。
+	//    使用 string 格式会被 Anthropic 检测为第三方应用。
+	claudeCodeSystemBlock := []map[string]any{
+		{
+			"type":          "text",
+			"text":          claudeCodeSystemPrompt,
+			"cache_control": map[string]string{"type": "ephemeral"},
+		},
+	}
+	out, ok := setJSONValueBytes(body, "system", claudeCodeSystemBlock)
 	if !ok {
 		logger.LegacyPrintf("service.gateway", "Warning: failed to set Claude Code system prompt")
 		return body
@@ -3978,12 +3987,17 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 	if shouldMimicClaudeCode {
 		// 非 Claude Code 客户端：将 system 替换为 Claude Code 标识，原始 system 迁移至 messages
 		// 条件：1) OAuth/SetupToken 账号  2) 不是 Claude Code 客户端  3) 不是 Haiku 模型  4) system 中还没有 Claude Code 提示词
+		systemRewritten := false
 		if !strings.Contains(strings.ToLower(reqModel), "haiku") &&
 			!systemIncludesClaudeCodePrompt(parsed.System) {
 			body = rewriteSystemForNonClaudeCode(body, parsed.System)
+			systemRewritten = true
 		}
 
-		normalizeOpts := claudeOAuthNormalizeOptions{stripSystemCacheControl: true}
+		// system 被重写时保留 CC prompt 的 cache_control: ephemeral（匹配真实 Claude Code 行为）；
+		// 未重写时（haiku / 已含 CC 前缀）剥离客户端 cache_control，与原有行为一致。
+		// 两种情况下 enforceCacheControlLimit 都会兜底处理上限。
+		normalizeOpts := claudeOAuthNormalizeOptions{stripSystemCacheControl: !systemRewritten}
 		if s.identityService != nil {
 			fp, err := s.identityService.GetOrCreateFingerprint(ctx, account.ID, c.Request.Header)
 			if err == nil && fp != nil {
@@ -5605,7 +5619,6 @@ func (s *GatewayService) buildUpstreamRequest(ctx context.Context, c *gin.Contex
 	// Build effective drop set: merge static defaults with dynamic beta policy filter rules
 	policyFilterSet := s.getBetaPolicyFilterSet(ctx, c, account, modelID)
 	effectiveDropSet := mergeDropSets(policyFilterSet)
-	effectiveDropWithClaudeCodeSet := mergeDropSets(policyFilterSet, claude.BetaClaudeCode)
 
 	// 处理 anthropic-beta header（OAuth 账号需要包含 oauth beta）
 	if tokenType == "oauth" {
@@ -5616,11 +5629,16 @@ func (s *GatewayService) buildUpstreamRequest(ctx context.Context, c *gin.Contex
 			applyClaudeCodeMimicHeaders(req, reqStream)
 
 			incomingBeta := getHeaderRaw(req.Header, "anthropic-beta")
-			// Match real Claude CLI traffic (per mitmproxy reports):
+			// Claude Code OAuth credentials are scoped to Claude Code.
-			// messages requests typically use only oauth + interleaved-thinking.
+			// Non-haiku models MUST include claude-code beta for Anthropic to recognize
-			// Also drop claude-code beta if a downstream client added it.
+			// this as a legitimate Claude Code request; without it, the request is
+			// rejected as third-party ("out of extra usage").
+			// Haiku models are exempt from third-party detection and don't need it.
 			requiredBetas := []string{claude.BetaOAuth, claude.BetaInterleavedThinking}
-			setHeaderRaw(req.Header, "anthropic-beta", mergeAnthropicBetaDropping(requiredBetas, incomingBeta, effectiveDropWithClaudeCodeSet))
+			if !strings.Contains(strings.ToLower(modelID), "haiku") {
+				requiredBetas = []string{claude.BetaClaudeCode, claude.BetaOAuth, claude.BetaInterleavedThinking}
+			}
+			setHeaderRaw(req.Header, "anthropic-beta", mergeAnthropicBetaDropping(requiredBetas, incomingBeta, effectiveDropSet))
 		} else {
 			// Claude Code 客户端：尽量透传原始 header，仅补齐 oauth beta
 			clientBetaHeader := getHeaderRaw(req.Header, "anthropic-beta")