diff --git a/backend/internal/config/config.go b/backend/internal/config/config.go
index 42f1e629..de876098 100644
--- a/backend/internal/config/config.go
+++ b/backend/internal/config/config.go
@@ -1402,7 +1402,7 @@ func setDefaults() {
 	viper.SetDefault("gateway.concurrency_slot_ttl_minutes", 30) // 并发槽位过期时间（支持超长请求）
 	viper.SetDefault("gateway.stream_data_interval_timeout", 180)
 	viper.SetDefault("gateway.stream_keepalive_interval", 10)
-	viper.SetDefault("gateway.max_line_size", 40*1024*1024)
+	viper.SetDefault("gateway.max_line_size", 500*1024*1024)
 	viper.SetDefault("gateway.scheduling.sticky_session_max_waiting", 3)
 	viper.SetDefault("gateway.scheduling.sticky_session_wait_timeout", 120*time.Second)
 	viper.SetDefault("gateway.scheduling.fallback_wait_timeout", 30*time.Second)
diff --git a/backend/internal/service/gateway_service.go b/backend/internal/service/gateway_service.go
index c6bec806..9b3c8bc0 100644
--- a/backend/internal/service/gateway_service.go
+++ b/backend/internal/service/gateway_service.go
@@ -41,7 +41,7 @@ const (
 	claudeAPIURL            = "https://api.anthropic.com/v1/messages?beta=true"
 	claudeAPICountTokensURL = "https://api.anthropic.com/v1/messages/count_tokens?beta=true"
 	stickySessionTTL        = time.Hour // 粘性会话TTL
-	defaultMaxLineSize      = 40 * 1024 * 1024
+	defaultMaxLineSize      = 500 * 1024 * 1024
 	// Canonical Claude Code banner. Keep it EXACT (no trailing whitespace/newlines)
 	// to match real Claude CLI traffic as closely as possible. When we need a visual
 	// separator between system blocks, we add "\n\n" at concatenation time.