diff --git a/main.go b/main.go
index fdf5751..8c2d0a7 100644
--- a/main.go
+++ b/main.go
@@ -73,7 +73,7 @@ func handleURI(rawURI string) error {
 
 	// 런처 자동 업데이트 체크
 	if updated, updateErr := ensureLauncher(serverInfo); updateErr != nil {
-		_ = updateErr // 업데이트 실패는 치명적이지 않음
+		fmt.Fprintf(os.Stderr, "런처 업데이트 실패: %v\n", updateErr)
 	} else if updated {
 		cmd := exec.Command(os.Args[0], os.Args[1:]...)
 		if err := cmd.Start(); err != nil {
diff --git a/protocol.go b/protocol.go
index ae840d8..5cd370b 100644
--- a/protocol.go
+++ b/protocol.go
@@ -15,8 +15,13 @@ import (
 )
 
 const (
-	protocolName    = "a301"
-	gameExeName     = "A301.exe"
+	protocolName = "a301"
+	gameExeName  = "A301.exe"
+)
+
+// serverInfoURL and redeemTicketURL can be overridden at build time via
+// -ldflags "-X main.serverInfoURL=... -X main.redeemTicketURL=..."
+var (
 	serverInfoURL   = "https://a301.api.tolelom.xyz/api/download/info"
 	redeemTicketURL = "https://a301.api.tolelom.xyz/api/auth/redeem-ticket"
 )
@@ -122,7 +127,7 @@ func fetchServerInfoOnce() (*downloadInfo, error) {
 		return nil, &errNoRetry{fmt.Errorf("게임이 아직 준비되지 않았습니다")}
 	}
 	if resp.StatusCode >= 400 {
-		return nil, &errNoRetry{fmt.Errorf("서버 오류 (HTTP %d)", resp.StatusCode)}
+		return nil, &errNoRetry{fmt.Errorf("요청 실패 (HTTP %d)", resp.StatusCode)}
 	}
 
 	var info downloadInfo
@@ -157,7 +162,11 @@ func redeemTicket(ticket string) (string, error) {
 
 func redeemTicketFrom(url, ticket string) (string, error) {
 	client := &http.Client{Timeout: 10 * time.Second}
-	body := fmt.Sprintf(`{"ticket":"%s"}`, ticket)
+	payload, err := json.Marshal(map[string]string{"ticket": ticket})
+	if err != nil {
+		return "", fmt.Errorf("요청 데이터 생성 실패: %w", err)
+	}
+	body := string(payload)
 	resp, err := client.Post(url, "application/json", strings.NewReader(body))
 	if err != nil {
 		return "", fmt.Errorf("서버에 연결할 수 없습니다: %w", err)