diff --git a/src/gui/mod.rs b/src/gui/mod.rs
index 4d7718e..7f646f5 100644
--- a/src/gui/mod.rs
+++ b/src/gui/mod.rs
@@ -584,7 +584,11 @@ impl ApplicationHandler<UserEvent> for App {
 /// Launch the GUI. Blocks until the window is closed (or the tray Quit is
 /// chosen). Runs on the main thread, a winit requirement, which is where `main`
 /// calls it from.
-pub fn run() -> anyhow::Result<()> {
+/// `relay` is the parent's `--relay` flag (if any), forwarded to every child
+/// process so a relay chosen on the GUI command line reaches the headless
+/// host/viewer. (The `PIXELPASS_RELAY` env var is inherited regardless; this
+/// covers the flag form.)
+pub fn run(relay: Option<String>) -> anyhow::Result<()> {
     let event_loop = EventLoop::<UserEvent>::with_user_event()
         .build()
         .map_err(|e| anyhow::anyhow!("failed to build the event loop: {e}"))?;
@@ -607,6 +611,7 @@ pub fn run() -> anyhow::Result<()> {
         tray,
         close_to_tray: gui_settings.close_to_tray,
         show_qr: gui_settings.show_qr,
+        relay,
         waker,
     };
     let mut app = App {
@@ -845,6 +850,9 @@ struct PixelPassApp {
     /// Persisted preference: render the QR-code panel on the host screen.
     /// Defaults to on; toggled in Settings.
     show_qr: bool,
+    /// The parent's `--relay` flag, forwarded to host/viewer children so the
+    /// flag form reaches them (env-var form is inherited automatically).
+    relay: Option<String>,
     /// Wakes the winit loop when a spawned child emits/exits.
     waker: Waker,
 }
@@ -1230,6 +1238,10 @@ impl PixelPassApp {
         if self.host.window {
             args.push("--window".to_string());
         }
+        if let Some(relay) = &self.relay {
+            args.push("--relay".to_string());
+            args.push(relay.clone());
+        }
 
         match ChildProc::spawn(&args, self.waker.clone()) {
             Ok(p) => self.host.proc = Some(p),
@@ -1503,7 +1515,11 @@ impl PixelPassApp {
 
         let ticket = self.viewer.ticket_input.trim().to_string();
         self.viewer.connecting_to = ticket_endpoint_id(&ticket).map(|id| short_id(&id));
-        let args = vec![ticket, "--output".to_string(), "json".to_string()];
+        let mut args = vec![ticket, "--output".to_string(), "json".to_string()];
+        if let Some(relay) = &self.relay {
+            args.push("--relay".to_string());
+            args.push(relay.clone());
+        }
         match ChildProc::spawn(&args, self.waker.clone()) {
             Ok(p) => self.viewer.proc = Some(p),
             Err(e) => self.viewer.error = Some(format!("Couldn't connect: {e}")),
diff --git a/src/main.rs b/src/main.rs
index 98ea6cb..2739ff4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -25,7 +25,7 @@ async fn main() -> Result<()> {
     if cli.gui {
         #[cfg(feature = "gui")]
         {
-            return gui::run();
+            return gui::run(cli.relay);
         }
         #[cfg(not(feature = "gui"))]
         {