diff --git a/crates/cli/src/cli.rs b/crates/cli/src/cli.rs
index 10a5b87b..0e916192 100644
--- a/crates/cli/src/cli.rs
+++ b/crates/cli/src/cli.rs
@@ -429,7 +429,8 @@ pub enum Command {
         long_about = "Open the terminal UI in the browser\n\n\
             Opens the browser on the local yas server, with that server's named\n\
             remotes reachable through its Relay. Manage remotes with\n\
-            `yas remote add/remove` or through the Remotes dialog in the browser.\n\n\
+            `yas remote add/remove` or through the Remotes dialog in the browser.\n\
+            `--on` and `--hub` are refused: the UI always starts from the local server.\n\n\
             Examples:\n\
               yas open                        # local + all configured remotes\n\
               yas remote add rabbit ssh:rabbit\n\
diff --git a/crates/cli/src/interactive.rs b/crates/cli/src/interactive.rs
index 16501426..e9d0b57d 100644
--- a/crates/cli/src/interactive.rs
+++ b/crates/cli/src/interactive.rs
@@ -27,7 +27,7 @@ struct BrowserState {
 }
 
 /// Open the local browser UI backed by one native YAS server.
-pub async fn run_browser(port: Option<u16>, _hub: &str) {
+pub async fn run_browser(port: Option<u16>) {
     let token: String = {
         use rand::RngExt as _;
         rand::rng()
diff --git a/crates/cli/src/main.rs b/crates/cli/src/main.rs
index cec2b09d..3a2a3f87 100644
--- a/crates/cli/src/main.rs
+++ b/crates/cli/src/main.rs
@@ -1008,8 +1008,14 @@ async fn async_main() {
             }
         }
         Command::Open { port } => {
-            let hub = yas_webrtc_forwarder::normalize_hub(&cli.connect.hub);
-            interactive::run_browser(port, &hub).await;
+            let hub_env = std::env::var_os("YAS_HUB").is_some();
+            if let Err(error) =
+                open_target_flags(cli.connect.on.as_deref(), &cli.connect.hub, hub_env)
+            {
+                eprintln!("yas: {error}");
+                std::process::exit(2);
+            }
+            interactive::run_browser(port).await;
         }
         Command::Edge => {
             yas_edge::run().await;
@@ -1089,6 +1095,22 @@ async fn async_main() {
 
 /// Read a `usize` limit from the environment. Unset, unparseable or 0 all
 /// mean "no limit", which is what the server's `> 0` guards already expect.
+/// `yas open` always serves the local server's UI and reaches other targets
+/// through its Remotes dialog, so a command-line target would be ignored.
+fn open_target_flags(on: Option<&str>, hub: &str, hub_env: bool) -> Result<(), String> {
+    if let Some(on) = on {
+        let on = mask_remote_credentials(on);
+        return Err(format!(
+            "yas open does not take --on ({on}); it opens the local server's UI, which \
+             lists configured remotes (add one with `yas remote add NAME {on}`)"
+        ));
+    }
+    if !hub_env && hub != yas_webrtc_forwarder::DEFAULT_HUB_URL {
+        return Err("yas open does not take --hub; it opens the local server's UI".into());
+    }
+    Ok(())
+}
+
 fn env_usize(key: &str) -> usize {
     std::env::var(key)
         .ok()
@@ -1467,7 +1489,18 @@ async fn cmd_upgrade() -> Result<(), Box<dyn std::error::Error>> {
 
 #[cfg(test)]
 mod tests {
-    use super::{mask_remote_credentials, proxy_daemon_requested};
+    use super::{mask_remote_credentials, open_target_flags, proxy_daemon_requested};
+
+    #[test]
+    fn open_refuses_targets_it_would_ignore() {
+        let default_hub = yas_webrtc_forwarder::DEFAULT_HUB_URL;
+        assert!(open_target_flags(None, default_hub, false).is_ok());
+        let error = open_target_flags(Some("share:secret"), default_hub, false).unwrap_err();
+        assert!(error.contains("--on"), "{error}");
+        assert!(!error.contains("secret"), "{error}");
+        assert!(open_target_flags(None, "hub.example", false).is_err());
+        assert!(open_target_flags(None, "hub.example", true).is_ok());
+    }
 
     #[test]
     fn test_mask_remote_credentials() {