diff --git a/src/components/ActionPanel.svelte b/src/components/ActionPanel.svelte
index 326ae55..063edc1 100644
--- a/src/components/ActionPanel.svelte
+++ b/src/components/ActionPanel.svelte
@@ -257,6 +257,20 @@
         Offline: ODIAN <strong>{s?.installed}</strong> runs on local data and map tiles.
       {/if}
     </p>
+    {#if s?.online && !s.signed_in && !checking}
+      <!-- The operator is remembered with the install (launcher.json travels with a drive),
+           the DHP sign-in is not (Credential Manager, per PC). So a drive on another PC offers
+           Launch as if nothing were missing, and ODIAN then runs on that PC's own data: no live
+           aircraft, no tiles from the site. Launch stays the button - a sign-in that cannot
+           complete must not stop ODIAN - but the gap is said here, with the way out. -->
+      <p class="secondary attention">
+        <Icon name="alert" size={14} />
+        <span>
+          Not signed in on this PC: ODIAN will run on this PC's own data, without live aircraft.
+          <button class="btn-link" disabled={blocked} onclick={() => launcher.signIn()}>Sign in</button>
+        </span>
+      </p>
+    {/if}
     {#if launcher.syncAttention > 0}
       <p class="secondary attention">
         <Icon name="alert" size={14} />
diff --git a/src/lib/mock.ts b/src/lib/mock.ts
index e29bf91..1bb1ab5 100644
--- a/src/lib/mock.ts
+++ b/src/lib/mock.ts
@@ -1,7 +1,7 @@
 // Browser-only stand-in for the Rust backend, so the hub can be designed with
 // `npm run dev`. Same shapes as docs/CONTRACT.md, driven by timers.
 //
-//   ?scenario=first-run | update-required | ready | offline-installed |
+//   ?scenario=first-run | update-required | ready | new-pc | offline-installed |
 //             offline-not-installed | installing | running | sync-conflicts | error |
 //             dev  (a licensed developer PC: the Dev section of Settings appears)
 //   &fail=sign_in | install | restore | launch | notes   make that flow fail
@@ -265,6 +265,11 @@ function initialStatus(scenario: MockScenario): Status {
     case "ready":
       Object.assign(s, { installed: CURRENT, operator: OPERATOR, signed_in: true });
       break;
+    case "new-pc":
+      // A drive on a PC it has never been on: the install and its operator came with it,
+      // the DHP sign-in (per PC) did not. Online, launchable, and not signed in.
+      Object.assign(s, { installed: CURRENT, operator: OPERATOR, signed_in: false });
+      break;
     case "offline-installed":
       Object.assign(s, { online: false, installed: PREVIOUS, operator: OPERATOR });
       break;
diff --git a/src/lib/types.ts b/src/lib/types.ts
index 9cbb7aa..af34150 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -349,6 +349,7 @@ export const MOCK_SCENARIOS = [
   "first-run",
   "update-required",
   "ready",
+  "new-pc",
   "offline-installed",
   "offline-not-installed",
   "installing",