diff --git a/tools/rugnux_cli.cpp b/tools/rugnux_cli.cpp
index cb422877..01ea9918 100644
--- a/tools/rugnux_cli.cpp
+++ b/tools/rugnux_cli.cpp
@@ -378,7 +378,9 @@ std::optional<CrystalLattice> parse_lattice_arg(const char *arg) {
 // path and the full-analysis path (each then sets its own space group and images-per-trigger).
 void configure_offline_output(DiffractionExperiment &experiment, const std::string &output_prefix) {
     experiment.BitDepthImage(32).Compression(CompressionAlgorithm::BSHUF_LZ4);
-    experiment.FilePrefix(output_prefix);
+    // Offline CLI: the operator chose the output path, so allow an absolute -o (the multi-user guard
+    // that FilePrefix() applies is only for remotely-supplied prefixes in the broker/writer).
+    experiment.FilePrefixTrusted(output_prefix);
     experiment.Mode(DetectorMode::Standard);   // full image analysis
     experiment.PixelSigned(true);
     experiment.OverwriteExistingFiles(true);