diff --git a/.ralph/fix_plan.md b/.ralph/fix_plan.md
index 9526f3e..c31605a 100644
--- a/.ralph/fix_plan.md
+++ b/.ralph/fix_plan.md
@@ -396,12 +396,12 @@ Spec: `.ralph/specs/phase-18-cli-cicd.md`
 
 ---
 
-## Phase 24: Onboarding + First-Run [PENDIENTE]
+## Phase 24: Onboarding + First-Run [COMPLETO]
 
-- [ ] 24.1: Detectar first-run en frontend (GET /api/auth/setup-required)
-- [ ] 24.2: Wizard multi-step: paso 1 crear admin, paso 2 nombre org, paso 3 "Start your first exploration" con URL input
-- [ ] 24.3: Empty states: ilustraciones/mensajes en tablas vacías ("No findings yet. Start an exploration!")
-- [ ] 24.4: Commit: `fase(24): onboarding and first-run experience`
+- [x] 24.1: Detectar first-run en frontend (GET /api/auth/setup-required)
+- [x] 24.2: Wizard multi-step: paso 1 crear admin, paso 2 nombre org, paso 3 "Start your first exploration" con URL input
+- [x] 24.3: Empty states: ilustraciones/mensajes en tablas vacías ("No findings yet. Start an exploration!")
+- [x] 24.4: Commit: `fase(24): onboarding and first-run experience`
 
 ---
 
diff --git a/frontend/src/pages/Setup.tsx b/frontend/src/pages/Setup.tsx
index 10a38ab..d707f38 100644
--- a/frontend/src/pages/Setup.tsx
+++ b/frontend/src/pages/Setup.tsx
@@ -7,6 +7,8 @@ import { Label } from '@/components/ui/label'
 import { apiFetch } from '@/lib/api'
 import { queryClient } from '@/lib/queryClient'
 
+const TOTAL_STEPS = 3
+
 export function Setup() {
   const navigate = useNavigate()
   const [step, setStep] = useState(1)
@@ -14,15 +16,12 @@ export function Setup() {
   const [email, setEmail] = useState('')
   const [password, setPassword] = useState('')
   const [orgName, setOrgName] = useState('')
+  const [firstUrl, setFirstUrl] = useState('')
   const [error, setError] = useState<string | null>(null)
   const [loading, setLoading] = useState(false)
 
-  async function handleSubmit(e: React.FormEvent) {
+  async function handleCreateAccount(e: React.FormEvent) {
     e.preventDefault()
-    if (step === 1) {
-      setStep(2)
-      return
-    }
     setError(null)
     setLoading(true)
     try {
@@ -31,7 +30,7 @@ export function Setup() {
         body: JSON.stringify({ name, email, password, organizationName: orgName }),
       })
       await queryClient.invalidateQueries({ queryKey: ['auth'] })
-      navigate('/')
+      setStep(3)
     } catch (err) {
       setError(err instanceof Error ? err.message : 'Setup failed')
     } finally {
@@ -39,98 +38,142 @@ export function Setup() {
     }
   }
 
+  function handleStep1(e: React.FormEvent) {
+    e.preventDefault()
+    setStep(2)
+  }
+
+  async function handleStartExploration() {
+    if (!firstUrl.trim()) {
+      navigate('/')
+      return
+    }
+    try {
+      const session = await apiFetch('/api/sessions', {
+        method: 'POST',
+        body: JSON.stringify({ url: firstUrl.trim() }),
+      }) as { id: string }
+      navigate(`/sessions/${session.id}`)
+    } catch {
+      navigate('/')
+    }
+  }
+
+  const stepTitle: Record<number, string> = {
+    1: 'Create your admin account',
+    2: 'Name your organization',
+    3: 'Start your first exploration',
+  }
+
   return (
     <div className="flex items-center justify-center min-h-screen bg-background">
       <Card className="w-full max-w-md">
         <CardHeader className="text-center">
           <CardTitle className="text-2xl font-bold">Welcome to ABE</CardTitle>
-          <CardDescription>
-            {step === 1 ? 'Create your admin account' : 'Name your organization'}
-          </CardDescription>
+          <CardDescription>{stepTitle[step]}</CardDescription>
         </CardHeader>
         <CardContent>
           <div className="flex gap-1 mb-6">
-            {[1, 2].map(s => (
+            {Array.from({ length: TOTAL_STEPS }).map((_, i) => (
               <div
-                key={s}
+                key={i}
                 className={`h-1 flex-1 rounded-full transition-colors ${
-                  s <= step ? 'bg-primary' : 'bg-muted'
+                  i + 1 <= step ? 'bg-primary' : 'bg-muted'
                 }`}
               />
             ))}
           </div>
-          <form onSubmit={(e) => void handleSubmit(e)} className="space-y-4">
-            {step === 1 ? (
-              <>
-                <div className="space-y-1.5">
-                  <Label htmlFor="name">Full Name</Label>
-                  <Input
-                    id="name"
-                    value={name}
-                    onChange={e => setName(e.target.value)}
-                    placeholder="John Doe"
-                    required
-                    autoFocus
-                  />
-                </div>
-                <div className="space-y-1.5">
-                  <Label htmlFor="email">Email</Label>
-                  <Input
-                    id="email"
-                    type="email"
-                    value={email}
-                    onChange={e => setEmail(e.target.value)}
-                    placeholder="admin@example.com"
-                    required
-                  />
-                </div>
-                <div className="space-y-1.5">
-                  <Label htmlFor="password">Password</Label>
-                  <Input
-                    id="password"
-                    type="password"
-                    value={password}
-                    onChange={e => setPassword(e.target.value)}
-                    minLength={8}
-                    required
-                  />
-                </div>
-                <Button type="submit" className="w-full">
-                  Continue
+
+          {step === 1 && (
+            <form onSubmit={(e) => void handleStep1(e)} className="space-y-4">
+              <div className="space-y-1.5">
+                <Label htmlFor="name">Full Name</Label>
+                <Input
+                  id="name"
+                  value={name}
+                  onChange={e => setName(e.target.value)}
+                  placeholder="John Doe"
+                  required
+                  autoFocus
+                />
+              </div>
+              <div className="space-y-1.5">
+                <Label htmlFor="email">Email</Label>
+                <Input
+                  id="email"
+                  type="email"
+                  value={email}
+                  onChange={e => setEmail(e.target.value)}
+                  placeholder="admin@example.com"
+                  required
+                />
+              </div>
+              <div className="space-y-1.5">
+                <Label htmlFor="password">Password</Label>
+                <Input
+                  id="password"
+                  type="password"
+                  value={password}
+                  onChange={e => setPassword(e.target.value)}
+                  minLength={8}
+                  required
+                />
+              </div>
+              <Button type="submit" className="w-full">Continue</Button>
+            </form>
+          )}
+
+          {step === 2 && (
+            <form onSubmit={(e) => void handleCreateAccount(e)} className="space-y-4">
+              <div className="space-y-1.5">
+                <Label htmlFor="org">Organization Name</Label>
+                <Input
+                  id="org"
+                  value={orgName}
+                  onChange={e => setOrgName(e.target.value)}
+                  placeholder="Acme Security"
+                  required
+                  autoFocus
+                />
+              </div>
+              {error && <p className="text-sm text-destructive">{error}</p>}
+              <div className="flex gap-2">
+                <Button type="button" variant="outline" className="flex-1" onClick={() => setStep(1)}>
+                  Back
                 </Button>
-              </>
-            ) : (
-              <>
-                <div className="space-y-1.5">
-                  <Label htmlFor="org">Organization Name</Label>
-                  <Input
-                    id="org"
-                    value={orgName}
-                    onChange={e => setOrgName(e.target.value)}
-                    placeholder="Acme Security"
-                    required
-                    autoFocus
-                  />
-                </div>
-                {error && (
-                  <p className="text-sm text-destructive">{error}</p>
-                )}
-                <div className="flex gap-2">
-                  <Button
-                    type="button"
-                    variant="outline"
-                    className="flex-1"
-                    onClick={() => setStep(1)}
-                  >
-                    Back
-                  </Button>
-                  <Button type="submit" className="flex-1" disabled={loading}>
-                    {loading ? 'Creating...' : 'Create Account'}
-                  </Button>
-                </div>
-              </>
-            )}
-          </form>
+                <Button type="submit" className="flex-1" disabled={loading}>
+                  {loading ? 'Creating…' : 'Create Account'}
+                </Button>
+              </div>
+            </form>
+          )}
+
+          {step === 3 && (
+            <div className="space-y-4">
+              <p className="text-sm text-muted-foreground">
+                ABE is ready. Enter a URL to start your first autonomous exploration, or skip to the dashboard.
+              </p>
+              <div className="space-y-1.5">
+                <Label htmlFor="first-url">Website URL</Label>
+                <Input
+                  id="first-url"
+                  type="url"
+                  value={firstUrl}
+                  onChange={e => setFirstUrl(e.target.value)}
+                  placeholder="https://example.com"
+                  autoFocus
+                />
+              </div>
+              <div className="flex gap-2">
+                <Button variant="outline" className="flex-1" onClick={() => navigate('/')}>
+                  Skip
+                </Button>
+                <Button className="flex-1" onClick={() => void handleStartExploration()}>
+                  Start Exploring
+                </Button>
+              </div>
+            </div>
+          )}
         </CardContent>
       </Card>
     </div>