fix(desktop): relay host status, display, and server-side LAN candidate

- Probe relay hosts through a throwaway E2EE tunnel in the host switcher
  instead of an HTTP probe against the relay:// pseudo-URL, which always
  reported Unreachable
- Show 'via OpenChamber Relay' for relay hosts in the switcher and the
  servers list instead of the raw relay:// pseudo-URL; hide the URL-centric
  edit action for relay hosts (saving it would drop the tunnel descriptor)
- Pairing LAN candidate prefers the address the requesting client actually
  reached the server on; interface scanning could pick an unroutable virtual
  bridge (docker0), producing links whose LAN leg silently failed and forced
  devices onto the relay

packages/ui/src/components/desktop/DesktopHostSwitcher.tsx

@@ -450,6 +450,13 @@ export function DesktopHostSwitcherDialog({
       const localClientToken = await getLocalClientToken();
       const results = await Promise.all(
         hosts.map(async (h) => {
+          // Relay hosts have no HTTP address to probe — check reachability
+          // through a throwaway E2EE tunnel instead.
+          if (h.relay) {
+            const startedAt = performance.now();
+            const ok = await probeRelayHost(h.relay).catch(() => false);
+            return [h.id, { status: ok ? ('ok' as const) : ('unreachable' as const), latencyMs: Math.round(performance.now() - startedAt) } satisfies HostStatus] as const;
+          }
           const url = normalizeHostUrl(isElectronShell() ? getDesktopHostApiUrl(h) : h.url);
           if (!url) {
             return [h.id, { status: 'unreachable' as const, latencyMs: 0 } satisfies HostStatus] as const;
@@ -898,7 +905,9 @@ export function DesktopHostSwitcherDialog({
                 const displayLabel = host.id === LOCAL_HOST_ID
                   ? t('desktopHostSwitcher.instance.local')
                   : redactSensitiveUrl(host.label);
-                const displayUrl = redactSensitiveUrl(effectiveUrl);
+                // Relay hosts have a relay:// pseudo-URL that means nothing to a
+                // person — say how the connection works instead.
+                const displayUrl = host.relay ? t('mobile.connect.relay.badge') : redactSensitiveUrl(effectiveUrl);
 
                 return (
                   <div

packages/ui/src/components/sections/remote-instances/RemoteInstancesPage.tsx

@@ -1459,16 +1459,23 @@ export const RemoteInstancesPage: React.FC = () => {
                           <p className="typography-ui-label text-foreground truncate">{redactSensitiveUrl(host.label)}</p>
                           {directDefaultHostId === host.id ? <span className="typography-micro text-muted-foreground">{t('desktopHostSwitcher.header.default')}</span> : null}
                         </div>
-                        <p className="typography-micro text-muted-foreground font-mono truncate">{redactSensitiveUrl(host.apiUrl || host.url)}</p>
+                        <p className={cn('typography-micro text-muted-foreground truncate', !host.relay && 'font-mono')}>
+                          {host.relay ? t('mobile.connect.relay.badge') : redactSensitiveUrl(host.apiUrl || host.url)}
+                        </p>
                       </div>
                       <div className="flex shrink-0 items-center gap-1">
                         <Button type="button" variant="ghost" size="xs" className="!font-normal" onClick={() => void setDefaultDirectHost(host.id)} disabled={directSaving || directDefaultHostId === host.id} aria-label={t('desktopHostSwitcher.actions.setAsDefaultAria')}>
                           {directDefaultHostId === host.id ? <Icon name="star-fill" className="h-3.5 w-3.5" /> : <Icon name="star" className="h-3.5 w-3.5" />}
                         </Button>
-                        <Button type="button" variant="ghost" size="xs" className="!font-normal" onClick={() => beginEditDirectHost(host)} disabled={directSaving}>
-                          <Icon name="pencil" className="h-3.5 w-3.5" />
-                          {t('desktopHostSwitcher.actions.edit')}
-                        </Button>
+                        {/* The edit form is URL/token-centric; saving it would drop a
+                            relay host's tunnel descriptor. Relay hosts are re-imported
+                            via a fresh pairing link instead. */}
+                        {host.relay ? null : (
+                          <Button type="button" variant="ghost" size="xs" className="!font-normal" onClick={() => beginEditDirectHost(host)} disabled={directSaving}>
+                            <Icon name="pencil" className="h-3.5 w-3.5" />
+                            {t('desktopHostSwitcher.actions.edit')}
+                          </Button>
+                        )}
                         <Button type="button" variant="ghost" size="xs" className="!font-normal" onClick={() => void handleRemoveDirectHost(host.id)} disabled={directSaving}>
                           <Icon name="delete-bin" className="h-3.5 w-3.5" />
                           {t('settings.common.actions.delete')}

packages/web/server/index.js

@@ -1117,17 +1117,35 @@ async function main(options = {}) {
   // a specific non-loopback host → that host), NOT from how the UI was opened — so
   // "Local network" works even when the UI is opened on localhost, and is absent
   // when the server is only bound to loopback (a LAN link would not connect).
-  const resolvePairingTransports = () => {
+  // The IPv4 the requesting client actually reached this server on (if any).
+  // Strips the IPv6-mapped prefix; loopback means "not a LAN path".
+  const requestReachedLanAddress = (req) => {
+    const raw = typeof req?.socket?.localAddress === 'string' ? req.socket.localAddress : '';
+    const address = raw.startsWith('::ffff:') ? raw.slice(7) : raw;
+    if (!/^\d+\.\d+\.\d+\.\d+$/.test(address)) return null;
+    if (address.startsWith('127.')) return null;
+    return address;
+  };
+  const resolvePairingTransports = (req) => {
     const activePort = tunnelRuntimeContext.getActivePort() || port;
     const local = `http://127.0.0.1:${activePort}`;
     let lanHost = null;
     if (isNetworkExposedBindHost(effectiveBindHost)) {
+      // Prefer the address the client is ALREADY talking to us on — it is the
+      // one interface guaranteed to be routable from that client's network.
+      // Interface scanning is only a fallback: on servers with virtual bridges
+      // (docker0 etc.) the first non-internal IPv4 can be an address no other
+      // machine can reach, which produced pairing links whose LAN candidate
+      // silently failed and forced devices onto the relay.
+      lanHost = requestReachedLanAddress(req);
       try {
-        for (const list of Object.values(os.networkInterfaces())) {
-          for (const entry of (list || [])) {
-            if (entry.family === 'IPv4' && !entry.internal) { lanHost = entry.address; break; }
+        if (!lanHost) {
+          for (const list of Object.values(os.networkInterfaces())) {
+            for (const entry of (list || [])) {
+              if (entry.family === 'IPv4' && !entry.internal) { lanHost = entry.address; break; }
+            }
+            if (lanHost) break;
           }
-          if (lanHost) break;
         }
       } catch {
         lanHost = null;

packages/web/server/lib/opencode/core-routes.js

@@ -800,7 +800,7 @@ export const registerAuthAndAccessRoutes = (app, dependencies) => {
   app.get('/api/client-auth/pairing/transports', async (req, res, next) => {
     await runWithClientCreateAuth(req, res, next, async () => {
       res.setHeader('Cache-Control', 'no-store');
-      res.json(getPairingTransports());
+      res.json(getPairingTransports(req));
     });
   });