diff --git a/backend/internal/service/account_test_service.go b/backend/internal/service/account_test_service.go
index a67a699e9f..fd29b324b1 100644
--- a/backend/internal/service/account_test_service.go
+++ b/backend/internal/service/account_test_service.go
@@ -602,7 +602,11 @@ func (s *AccountTestService) testOpenAIAccountConnection(c *gin.Context, account
 		req.Header.Set("accept", "text/event-stream")
 		req.Header.Set("OpenAI-Beta", "responses=experimental")
 		req.Header.Set("Originator", "codex_cli_rs")
-		req.Header.Set("User-Agent", codexCLIUserAgent)
+		if customUA := strings.TrimSpace(credentialAccount.GetOpenAIUserAgent()); customUA != "" {
+			req.Header.Set("User-Agent", customUA)
+		} else {
+			req.Header.Set("User-Agent", codexCLIUserAgent)
+		}
 		setOpenAIChatGPTAccountHeaders(req.Header, credentialAccount)
 	}