diff --git a/tests/test_link.py b/tests/test_link.py
index 8dbfac4..f512f24 100644
--- a/tests/test_link.py
+++ b/tests/test_link.py
@@ -241,6 +241,17 @@ class Connecting(unittest.TestCase):
         self.assertIn("No headset", s["error"]["message"])
         self.assertEqual(self.routes[-1], ("frame-control-no-headset", ["-o", "HostName=no-headset.invalid"]))
 
+    def test_a_headset_without_addresses_reaches_nothing(self):
+        d = self.device("localhost")
+        self.hosts({"localhost": "ok"})
+        self.link.connect(["start"])
+        fl.devices_action(self.link, {"action": "address-remove", "id": d["id"], "host": "localhost"}, None)
+        self.assertIn("HostName=no-address.invalid", self.routes[-1][1])  # at once, not after a retry
+        self.link.connect(["switch"])
+        s = self.link.snapshot()
+        self.assertEqual((s["phase"], s["retry_at"]), ("failed", None))
+        self.assertIn("no addresses", s["error"]["message"])
+
     def test_a_bare_alias_lets_ssh_config_decide(self):
         self.link.override = "frame-bare"
         self.hosts({"frame-bare": "ok"})  # the stand-in ssh has no config: the alias is the host
diff --git a/ui/frame_link.py b/ui/frame_link.py
index 2b360cf..5dbcefc 100644
--- a/ui/frame_link.py
+++ b/ui/frame_link.py
@@ -338,8 +338,10 @@ class Link:
         """What every ssh command adds to reach DEVICE at HOST."""
         if device.get("none"):
             return ["-o", "HostName=no-headset.invalid"]  # fails at once, with ssh's own "can't resolve"
-        if device.get("transient") or not host:
+        if device.get("transient"):
             return []
+        if not host:  # a headset with no addresses: reach nothing, not whatever ~/.ssh/config says
+            return ["-o", "HostName=no-address.invalid"]
         return ["-o", f"HostName={frame_devices.ssh_host(host)}",
                 "-o", f"HostKeyAlias={frame_devices.host_key_alias(device['id'])}",
                 "-o", f"UserKnownHostsFile={frame_devices.known_hosts_opt(device['id'])}", "-o", "HashKnownHosts=no",
@@ -454,7 +456,7 @@ class Link:
                     self.state.update(phase="connected", retry_at=None, error=None)
                 else:
                     self.fails += 1
-                    self.state.update(phase="failed", retry_at=None if device.get("none") else
+                    self.state.update(phase="failed", retry_at=None if device.get("none") or not (device.get("transient") or device["addresses"]) else
                                       now() + RETRY[min(self.fails, len(RETRY)) - 1])
                     if not self.state["error"]:
                         self.state["error"] = {"stage": "find", "message": "Couldn't connect", "raw": ""}
@@ -485,6 +487,9 @@ class Link:
         if device.get("none"):
             self.fail("find", "No headset is set up. Add one on the Devices tab.")
             return False
+        if not device.get("transient") and not device["addresses"]:
+            self.fail("find", f"{device['name']} has no addresses. Add one on the Devices tab.")
+            return False
         # 1. this computer's network
         self.stage("network", "active")
         net = frame_network.current_network(self.last_fp)
@@ -506,8 +511,7 @@ class Link:
         # 2. find the headset
         self.stage("find", "active")
         port = device.get("port") or 22
-        bare = device.get("transient") or not device["addresses"]
-        if bare:
+        if device.get("transient"):
             host, port, user, proxied = ssh_g(device["alias"])
             if user and not device.get("user"):
                 device["user"] = user
@@ -951,9 +955,13 @@ def devices_action(link, body, open_setup, busy=lambda: 0):
     elif action == "address-update":
         a = reg.update_address(did, body.get("host"), new_host=body.get("newHost"), kind=body.get("kind"),
                                label=body.get("label"))
+        if is_active and a["host"] != body.get("host"):
+            link.invalidate()  # the address in use may have moved
         msg = f"Saved {a['host']}"
     elif action == "address-remove":
         reg.remove_address(did, body.get("host"))
+        if is_active:
+            link.invalidate()  # it may be the address in use: stop using it now
         msg = f"Removed {body.get('host')}"
     elif action == "address-move":
         delta = body.get("delta")
diff --git a/ui/index.html b/ui/index.html
index 754624e..7f77b32 100644
--- a/ui/index.html
+++ b/ui/index.html
@@ -1537,12 +1537,12 @@ window.addEventListener("drop", e => {
   const dirs = new Set(items.map((it, i) => it.webkitGetAsEntry && it.webkitGetAsEntry()?.isDirectory ? i : -1).filter(i => i >= 0));
   sendFiles([...e.dataTransfer.files], dirs);
 });
-function upload(file, mode) {
+function upload(file, mode, dev = window.connDevice) {
   return new Promise((resolve, reject) => {
     const xhr = new XMLHttpRequest();
     xhr.open("POST", "/api/upload");
     xhr.setRequestHeader("X-Frame-UI", UI_KEY);
-    if (window.connDevice) xhr.setRequestHeader("X-Frame-Device", window.connDevice);
+    if (dev) xhr.setRequestHeader("X-Frame-Device", dev);
     xhr.setRequestHeader("X-Filename", encodeURIComponent(file.name));
     xhr.setRequestHeader("X-Mode", mode);
     const bar = $("prog").firstElementChild;
@@ -1603,7 +1603,12 @@ $("apkAltClose").onclick = () => $("apkAltDlg").close();
 
 const TITLE_EXT = /\.(zip|exe)$/i;
 async function sendFiles(files, dirs = new Set()) {
+  const dev = window.connDevice;  // the whole batch is for the headset it was dropped on
   for (const [i, f] of files.entries()) {
+    if (window.connDevice !== dev) {
+      toast(`Switched headsets: didn't send ${files.length - i} remaining file${files.length - i === 1 ? "" : "s"}`, true);
+      break;
+    }
     const path = window.frameApp?.pathForFile ? window.frameApp.pathForFile(f) : "";
     if (dirs.has(i)) {
       if (path) await sideload(f, path, true);
@@ -1613,7 +1618,7 @@ async function sendFiles(files, dirs = new Set()) {
     if (!f.size) { toast(`${f.name}: empty files aren't supported`, true); continue; }
     if (TITLE_EXT.test(f.name)) { await sideload(f, path); continue; }
     const apk = f.name.toLowerCase().endsWith(".apk");
-    await act(apk ? `Install ${f.name}` : `Copy ${f.name} to ~/Downloads`, () => upload(f, apk ? "apk" : "push"));
+    await act(apk ? `Install ${f.name}` : `Copy ${f.name} to ~/Downloads`, () => upload(f, apk ? "apk" : "push", dev));
   }
   $("fileInput").value = "";
   refresh();
@@ -2639,9 +2644,14 @@ $("connSetup").onclick = setUpActive;
 
 // ---- Devices tab ----
 PAGES.push("devices");
+let devicesSeq = 0;  // an older answer arriving late mustn't bring back the old selection
 async function loadDevices() {
   if (!link.live) return;
-  try { dv.data = await api("/api/devices"); } catch (e) { return failed($("devList"), e); }
+  const seq = ++devicesSeq;
+  let data;
+  try { data = await api("/api/devices"); } catch (e) { if (seq === devicesSeq) failed($("devList"), e); return; }
+  if (seq !== devicesSeq) return;
+  dv.data = data;
   dv.list = dv.data.devices;
   if (!dv.list.some(d => d.id === dv.sel)) dv.sel = dv.data.active;
   const sel = $("devSel");