feat: complete kiro platform support

backend/internal/service/gateway_service.go

@@ -912,6 +912,7 @@ type claudeOAuthNormalizeOptions struct {
 	injectMetadata          bool
 	metadataUserID          string
 	stripSystemCacheControl bool
+	preserveToolChoice      bool
 }
 
 // sanitizeSystemText rewrites only the fixed OpenCode identity sentence (if present).
@@ -1126,6 +1127,12 @@ func normalizeClaudeOAuthRequestBody(body []byte, modelID string, opts claudeOAu
 			modified = true
 		}
 	}
+	if !opts.preserveToolChoice && gjson.GetBytes(out, "tool_choice").Exists() {
+		if next, ok := deleteJSONPathBytes(out, "tool_choice"); ok {
+			out = next
+			modified = true
+		}
+	}
 
 	// max_tokens：真实 CLI 的默认值是 128000。缺失时补齐以对齐指纹。
 	if !gjson.GetBytes(out, "max_tokens").Exists() {
@@ -4518,7 +4525,10 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 		// 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}
+		normalizeOpts := claudeOAuthNormalizeOptions{
+			stripSystemCacheControl: !systemRewritten,
+			preserveToolChoice:      account.Platform == PlatformKiro,
+		}
 		if s.identityService != nil {
 			fp, err := s.identityService.GetOrCreateFingerprint(ctx, account.ID, c.Request.Header)
 			if err == nil && fp != nil {
@@ -8968,6 +8978,10 @@ func (s *GatewayService) ForwardCountTokens(ctx context.Context, c *gin.Context,
 		s.countTokensError(c, http.StatusNotFound, "not_found_error", "count_tokens endpoint is not supported for this platform")
 		return nil
 	}
+	if account.Platform == PlatformKiro && account.Type == AccountTypeOAuth {
+		s.countTokensError(c, http.StatusNotFound, "not_found_error", "Token counting is not supported for this platform")
+		return nil
+	}
 
 	// 应用模型映射：
 	// - APIKey 账号：使用账号级别的显式映射（如果配置），否则透传原始模型名