diff --git a/core/server.js b/core/server.js
index 527fd9c..49b6199 100644
--- a/core/server.js
+++ b/core/server.js
@@ -166,6 +166,7 @@ export async function createPithos(opts = {}) {
       pithos: pithosVersion,
       // electron-builder's portable exe sets this; updates then fetch the portable build.
       portable: hostName === 'desktop' && !!process.env.PORTABLE_EXECUTABLE_FILE,
+      platform: process.platform,
       daemon: daemon.status(),
       external: await probeExternal(c),
       s3d: { ...v, pinned: S3D_VERSION, installable: !!assetForPlatform(), outdated: !!(v?.version && cmpVersion(v.version, S3D_VERSION) < 0) },
@@ -540,7 +541,9 @@ export async function createPithos(opts = {}) {
     if (releaseCache && Date.now() - releaseCache.at < 10 * 60_000 && url.searchParams.get('fresh') !== '1') return releaseCache.body;
     const res = await fetch(`${RELEASES_URL}?t=${Math.floor(Date.now() / 60000)}`, { cache: 'no-store', signal: AbortSignal.timeout(15_000) }).catch((e) => { throw new HttpError(502, e.message); });
     if (!res.ok) throw new HttpError(502, `the release list answered ${res.status}`);
-    const list = ((await res.json())?.releases || []).filter((e) => e.id === 'pithos-desktop' && /^\d+\.\d+\.\d+$/.test(e.version));
+    // each build is listed per platform ("win-x64", "linux-x64", "mac-…"); only ours counts
+    const os = { win32: 'win', linux: 'linux', darwin: 'mac' }[process.platform];
+    const list = ((await res.json())?.releases || []).filter((e) => e.id === 'pithos-desktop' && /^\d+\.\d+\.\d+$/.test(e.version) && String(e.platform || '').startsWith(`${os}-`));
     const latest = list.reduce((best, e) => (!best || cmpVersion(e.version, best.version) > 0 ? e : best), null);
     const body = { latest: latest && { version: latest.version, date: latest.date || null, changes: String(latest.changes || '').slice(0, 600) } };
     releaseCache = { at: Date.now(), body };
diff --git a/ui/app.js b/ui/app.js
index fde8338..65c9829 100644
--- a/ui/app.js
+++ b/ui/app.js
@@ -2570,7 +2570,8 @@ const UPDATES_URL = 'https://navigate.st/bns/theseus.x/extensions/pithos/updates
 // (read by the local server). The chip downloads the matching installer, or
 // the portable exe, in the browser.
 function desktopUpdates(current, { ver, chip, check }) {
-  const file = state.status?.portable ? 'Pithos-portable.exe' : 'Pithos-Setup.exe';
+  const plat = state.status?.platform;
+  const file = plat === 'linux' ? 'Pithos.AppImage' : plat === 'darwin' ? 'Pithos.dmg' : state.status?.portable ? 'Pithos-portable.exe' : 'Pithos-Setup.exe';
   const rest = () => { chip.hidden = true; ver.hidden = false; };
   const flash = (text, cls, title) => {
     chip.hidden = false; ver.hidden = true; chip.className = `brandupd ${cls}`; chip.textContent = text; chip.title = title || ''; chip.disabled = true; chip.onclick = null;