diff --git a/src-tauri/src/launcher.rs b/src-tauri/src/launcher.rs
index 7e893c9..6dcab82 100644
--- a/src-tauri/src/launcher.rs
+++ b/src-tauri/src/launcher.rs
@@ -304,6 +304,50 @@ fn holds_a_version(root: &Path) -> bool {
 
 /// The launcher's update feed on the download page (written by package_launcher.ps1).
 const LAUNCHER_FEED: &str = "launcher-update.json";
+/// The same, for a launcher that runs from an ODIAN drive and replaces its own exe.
+const PORTABLE_FEED: &str = "launcher-portable.json";
+
+/// Is `offered` a later version than `running`? Plain numeric compare, field by field.
+fn newer(offered: &str, running: &str) -> bool {
+  fn parts(v: &str) -> Vec<u64> {
+    v.split(['.', '-']).map_while(|p| p.parse().ok()).collect()
+  }
+  let (a, b) = (parts(offered), parts(running));
+  for i in 0..a.len().max(b.len()) {
+    let (x, y) = (a.get(i).copied().unwrap_or(0), b.get(i).copied().unwrap_or(0));
+    if x != y {
+      return x > y;
+    }
+  }
+  false
+}
+
+/// Put `bytes` where this executable is, moving the running one aside.
+///
+/// The `.old` copy is what makes this safe to do to yourself: if the new exe never starts,
+/// the previous one is still on the drive next to it. `prune_old_exe` removes it at the
+/// next start, which only happens once the new one has run.
+fn swap_exe(bytes: &[u8]) -> Result<(), String> {
+  let exe = std::env::current_exe().map_err(|e| format!("cannot find this launcher: {e}"))?;
+  let old = exe.with_extension("old.exe");
+  let fresh = exe.with_extension("new.exe");
+  let _ = std::fs::remove_file(&old);
+  std::fs::write(&fresh, bytes).map_err(|e| format!("cannot write {}: {e}", fresh.display()))?;
+  std::fs::rename(&exe, &old).map_err(|e| format!("cannot move the running launcher aside: {e}"))?;
+  if let Err(e) = std::fs::rename(&fresh, &exe) {
+    let _ = std::fs::rename(&old, &exe); // put it back rather than leave the drive with none
+    return Err(format!("cannot put the new launcher in place: {e}"));
+  }
+  Ok(())
+}
+
+/// Delete the exe a portable update moved aside. Called at start: reaching here at all is
+/// the new launcher proving it runs.
+pub fn prune_old_exe() {
+  if let Ok(exe) = std::env::current_exe() {
+    let _ = std::fs::remove_file(exe.with_extension("old.exe"));
+  }
+}
 
 /// Append one line to `<dir>/launcher.log`, keeping one older file past 2 MB. Best effort:
 /// a log that cannot be written never stops the launcher.
@@ -1611,12 +1655,79 @@ impl Launcher {
   /// run its installer, which restarts the launcher. Runs first at start; `updating_self`
   /// keeps anything from launching or installing meanwhile (the window reads "checking").
   /// Offline, with no page configured, or with anything wrong, this launcher carries on.
+  /// Update a launcher that runs from an ODIAN drive, by replacing its own exe.
+  ///
+  /// The feed is `launcher-portable.json`: a small document signed with the release key, the
+  /// same key and the same `signing_payload` rule as a pack manifest, naming the raw exe and
+  /// its sha256. Both are checked before anything is swapped - the signature says the DHP
+  /// meant to publish this, the hash says the bytes arrived whole.
+  ///
+  /// Windows will not let a running exe be overwritten, but it WILL let it be renamed, so
+  /// the old one is moved aside and the new one takes its name. The old copy is deleted at
+  /// the next start, which is to say once the new one has proved it runs.
+  async fn update_portable(&self, app: &AppHandle) {
+    let mcp_url = self.inner.lock().await.settings.mcp_url.clone();
+    if mcp_url.is_empty() {
+      return;
+    }
+    let url = format!("{}/download/{PORTABLE_FEED}", mcp_url.trim_end_matches('/'));
+    let Ok(response) = self.http.get(&url).timeout(Duration::from_secs(20)).send().await else {
+      return; // offline is the normal case away from the office
+    };
+    if !response.status().is_success() {
+      return; // a site that publishes no portable build simply has nothing to offer
+    }
+    let Ok(feed) = response.json::<serde_json::Value>().await else { return };
+    if let Err(e) = odian_packs::signing::verify(&feed, odian_packs::bundled_public_key()) {
+      self.log(app, "warn", format!("The portable launcher feed is not signed by the ODIAN release key: {e}"));
+      return;
+    }
+    let (Some(version), Some(file), Some(want_sha)) = (
+      feed.get("version").and_then(|v| v.as_str()),
+      feed.get("file").and_then(|v| v.as_str()),
+      feed.get("sha256").and_then(|v| v.as_str()),
+    ) else {
+      return;
+    };
+    if !newer(version, env!("CARGO_PKG_VERSION")) {
+      return;
+    }
+    // A file name from the feed must never escape the download folder.
+    if file.contains(['/', '\\']) || file.contains("..") {
+      self.log(app, "warn", format!("The portable launcher feed names a suspect file: {file}"));
+      return;
+    }
+    self.log(app, "info", format!("Updating this drive's launcher to {version}…"));
+    let bytes = match self.http.get(format!("{}/download/{file}", mcp_url.trim_end_matches('/')))
+      .timeout(Duration::from_secs(300)).send().await
+    {
+      Ok(r) if r.status().is_success() => match r.bytes().await {
+        Ok(b) => b,
+        Err(e) => return self.log(app, "warn", format!("The new launcher did not download: {e}")),
+      },
+      _ => return self.log(app, "warn", "The new launcher did not download."),
+    };
+    let got = odian_packs::hashing::sha256_hex(&bytes);
+    if got != want_sha {
+      self.log(app, "warn", "The new launcher failed its checksum and was not installed.");
+      return;
+    }
+    if let Err(e) = swap_exe(&bytes) {
+      self.log(app, "warn", format!("Could not replace this drive's launcher: {e}"));
+      return;
+    }
+    self.log(app, "info", format!("This drive's launcher is now {version}. Restarting…"));
+    app.restart();
+  }
+
   pub async fn update_self(&self, app: &AppHandle) {
     use tauri_plugin_updater::UpdaterExt;
-    // A launcher that ships on an ODIAN drive is part of the drive: installing a newer one
-    // would put it on this PC instead, beside an install it does not carry.
+    // A launcher that ships on an ODIAN drive cannot take the ordinary update: that runs the
+    // NSIS setup, which installs onto whatever PC the drive is plugged into - leaving a
+    // launcher behind on a borrowed machine, pointed at an install that PC does not have.
+    // The drive's copy replaces its own exe instead, in place, from a signed raw build.
     if self.inner.lock().await.portable {
-      self.log(app, "info", "This launcher runs from its ODIAN drive: it is updated with the drive.");
+      self.update_portable(app).await;
       return;
     }
     let mcp_url = self.inner.lock().await.settings.mcp_url.clone();
@@ -2542,6 +2653,25 @@ mod tests {
     std::fs::remove_dir_all(&web).ok();
   }
 
+  #[test]
+  fn a_drive_only_takes_a_genuinely_later_launcher() {
+    // Numeric, field by field. Text order would read 0.1.9 as later than 0.1.10 and pin
+    // every drive on the older build for the rest of the 0.1.x line.
+    assert!(newer("0.1.35", "0.1.34"));
+    assert!(newer("0.1.10", "0.1.9"), "ten is after nine");
+    assert!(!newer("0.1.9", "0.1.10"));
+    assert!(!newer("0.1.34", "0.1.34"), "the same version is not an update");
+    assert!(!newer("0.1.33", "0.1.34"), "never walk backwards");
+    assert!(newer("0.2.0", "0.1.99"));
+    assert!(newer("1.0.0", "0.9.9"));
+    // A suffixed tag compares on its numbers; nothing after them counts.
+    assert!(newer("0.1.35-dhp", "0.1.34"));
+    assert!(!newer("0.1.34-dhp", "0.1.34"));
+    // Nonsense from a feed must not read as an update.
+    assert!(!newer("", "0.1.34"));
+    assert!(!newer("latest", "0.1.34"));
+  }
+
   #[test]
   fn only_another_operators_name_is_a_user_swap() {
     assert_eq!(swapped_user("m2op", Some("jimmy")), Some("m2op"));
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index bbe6869..beb4cf9 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -36,6 +36,9 @@ pub fn run() {
       }
       app.manage(launcher::Launcher::load(app.handle())?);
 
+      // Reaching here is the proof a portable update worked, so the exe it moved aside can
+      // go. Before anything else: it costs one remove of a file that is usually absent.
+      launcher::prune_old_exe();
       // First a newer launcher, if the download page has one (it installs and restarts
       // this one), then a look at the site; the window shows "checking" meanwhile.
       let handle = app.handle().clone();
diff --git a/src-tauri/tauri.conf.json b/src-tauri/tauri.conf.json
index fb16bdf..fa1a704 100644
--- a/src-tauri/tauri.conf.json
+++ b/src-tauri/tauri.conf.json
@@ -1,7 +1,7 @@
 {
   "$schema": "../node_modules/@tauri-apps/cli/config.schema.json",
   "productName": "ODIAN Launcher",
-  "version": "0.1.34",
+  "version": "0.1.36",
   "identifier": "fr.odian.launcher",
   "build": {
     "frontendDist": "../dist",