diff --git a/frontend/src/app/components/OnboardingV3/beats/BeatCard.tsx b/frontend/src/app/components/OnboardingV3/beats/BeatCard.tsx
index 9e33a00d..efe80ff9 100644
--- a/frontend/src/app/components/OnboardingV3/beats/BeatCard.tsx
+++ b/frontend/src/app/components/OnboardingV3/beats/BeatCard.tsx
@@ -52,6 +52,8 @@ const BeatCard: React.FC<{
 }> = ({ c, identity, onFinish, onBack }) => {
   const { accent, gradient } = useThemeAccent();
   const [name, setName] = useState(() => nameFromIdentity(identity));
+  // finish() can legitimately wait up to PREP_WAIT_CAP_MS on prep; the button must say so, once.
+  const [submitting, setSubmitting] = useState(false);
   const seed = useMemo(() => Math.floor(Math.random() * EPITHETS.length), []);
   const [roll, setRoll] = useState(0);
   const epithet = EPITHETS[(seed + roll) % EPITHETS.length];
@@ -184,8 +186,9 @@ const BeatCard: React.FC<{
       c={c}
       title={name ? `Welcome to OpenSwarm, ${name}` : 'Welcome to OpenSwarm'}
       body={"Here's your Swarm Card. Show it off to the world or keep it to yourself.\n\nAnd with that, you're ready to run your new OS."}
-      nextLabel="Get started"
-      onNext={() => onFinish(name.trim() || null)}
+      nextLabel={submitting ? 'Setting up...' : 'Get started'}
+      nextDisabled={submitting}
+      onNext={() => { if (submitting) return; setSubmitting(true); onFinish(name.trim() || null); }}
       onBack={onBack}
       stageDark
     >
diff --git a/frontend/src/app/components/OnboardingV3/useOnboardingV3Pipeline.ts b/frontend/src/app/components/OnboardingV3/useOnboardingV3Pipeline.ts
index bfdea934..0536ccc4 100644
--- a/frontend/src/app/components/OnboardingV3/useOnboardingV3Pipeline.ts
+++ b/frontend/src/app/components/OnboardingV3/useOnboardingV3Pipeline.ts
@@ -29,6 +29,7 @@ export function useOnboardingV3Pipeline() {
   // greeting/starters the instant they're ready (the common case, prep finishes during the beats) without
   // awaiting, so the curtain never blocks behind a spinner.
   const prepReadyRef = useRef<PrepResponse | null>(null);
+  const finishingRef = useRef(false);
   const scanResultRef = useRef<ScanResult | null>(null);
   const usageSummaryRef = useRef<string>('');
   const usageReadRef = useRef<Promise<void> | null>(null);
@@ -72,6 +73,9 @@ export function useOnboardingV3Pipeline() {
   }, []);
 
   const finish = useCallback(async (outcome: 'done' | 'skipped') => {
+    // Double-fire guard: repeated Get-started clicks during the prep wait must not stage twice.
+    if (finishingRef.current) return;
+    finishingRef.current = true;
     if (outcome === 'skipped') {
       dispatch(setFlowActive(false));
       dispatch(updateSettingsPatch({ onboarding_v3: 'skipped', accent_color: accent, accent_gradient: gradient, theme: mode }));