diff --git a/src/renderer/src/App.tsx b/src/renderer/src/App.tsx
index 3e9ec678..d475c94d 100644
--- a/src/renderer/src/App.tsx
+++ b/src/renderer/src/App.tsx
@@ -17,8 +17,8 @@ import type { SearchHit } from './types'
 import { loadProFeaturesRenderer } from './bootstrap/loadProFeaturesRenderer'
 import { renderProView, type ProViewContext } from './bootstrap/proView'
 import { UpgradeScreen } from './components/pro/UpgradeScreen'
-import { getProFeature, proFeatureComingSoon } from './components/pro/proCatalog'
-import { currentPlatform, isMac } from './lib/device'
+import { getProFeature, proFeatureComingSoon, landingView } from './components/pro/proCatalog'
+import { currentPlatform } from './lib/device'
 import { NotificationProvider } from './hooks/NotificationProvider'
 import { useNotifications } from './hooks/useNotifications'
 import { ToastProvider } from './hooks/ToastProvider'
@@ -226,9 +226,10 @@ function AppContent() {
     }
   }, [])
 
-  // Free users land on Models (download a model first, with the sidebar to
-  // explore); Mac Pro users land on Day. Never land on a locked or unavailable tab.
-  const [viewMode, setViewMode] = useState<ViewMode>(isPro && isMac() ? 'day' : 'models')
+  // Where to open: derived from the per-feature capability seam (see landingView), so
+  // the landing screen can never disagree with nav and gating about whether Day is
+  // available on this platform.
+  const [viewMode, setViewMode] = useState<ViewMode>(landingView(currentPlatform(), isPro))
   const [selectedSessionId, setSelectedSessionId] = useState<string | null>(null)
   const [selectedMemoryId, setSelectedMemoryId] = useState<number | null>(null)
   // Version of a downloaded-and-staged update (null = none). Surfaced as a banner
diff --git a/src/renderer/src/components/pro/proCatalog.ts b/src/renderer/src/components/pro/proCatalog.ts
index 9a670272..35012cb2 100644
--- a/src/renderer/src/components/pro/proCatalog.ts
+++ b/src/renderer/src/components/pro/proCatalog.ts
@@ -62,7 +62,13 @@ export const PRO_FEATURES: ProFeature[] = [
       'Per-meeting prep: who’s in it and your open items',
       'Priorities surfaced from what you actually did'
     ],
-    platforms: ['darwin']
+    // Ported to Windows: the whole Day path is portable - day.ts, day-layout.ts,
+    // ahead.ts and calendar.ts carry no platform-native code. Its two data sources
+    // both work on Windows now: the calendar comes from connectors (HTTP), and the
+    // activity half reads observations, which Replay's port put on Windows. Landing
+    // on Day now routes through `landingView` rather than an `isMac()` check, so nav,
+    // gating, copy and the landing screen all agree.
+    platforms: ['darwin', 'win32']
   },
   {
     route: 'reflect',
@@ -161,7 +167,12 @@ export const PRO_FEATURES: ProFeature[] = [
       'Approval queue for actions',
       'Auto-extracted to-dos'
     ],
-    platforms: ['darwin']
+    // Ported to Windows alongside Day, which produces its content: proactive.ts builds
+    // notifications from getDayPlan / getEventPrep, so shipping this without Day would
+    // have delivered an empty surface. Delivery is Electron's Notification (guarded by
+    // isSupported()), and core already sets the AppUserModelID that Windows requires
+    // for a toast to appear at all. notify.ts / proactive.ts carry no platform code.
+    platforms: ['darwin', 'win32']
   },
   {
     route: 'voice',
@@ -262,3 +273,23 @@ export function proFeatureComingSoon(
   }
   return !featureSupportsPlatform(feature, platform)
 }
+
+/**
+ * Which view the app should OPEN on. Free users land on Models (they need a model
+ * before anything else works); Pro users land on Day — but only where Day is
+ * actually available.
+ *
+ * This lives here, beside the seam, because it is a per-feature platform decision and
+ * `platforms` is the single source of truth for those. It previously sat in App.tsx as
+ * `isPro && isMac() ? 'day' : 'models'`, which was right only by accident: it agreed
+ * with the catalog while Day was macOS-only, and would have stranded a ported Day on
+ * Windows — nav and gating would light Day up from `platforms` while the landing
+ * screen still asked `isMac()`. Route the decision through the seam so porting a
+ * feature never leaves a second place to update.
+ *
+ * Never land on a locked or unavailable tab.
+ */
+export function landingView(platform: DevicePlatform, isPro: boolean): 'day' | 'models' {
+  const day = getProFeature('day')
+  return isPro && day && featureSupportsPlatform(day, platform) ? 'day' : 'models'
+}
diff --git a/src/renderer/src/lib/__tests__/proCatalog.lookup.test.ts b/src/renderer/src/lib/__tests__/proCatalog.lookup.test.ts
index bb53790b..e2197667 100644
--- a/src/renderer/src/lib/__tests__/proCatalog.lookup.test.ts
+++ b/src/renderer/src/lib/__tests__/proCatalog.lookup.test.ts
@@ -10,6 +10,7 @@ import {
   featureSupportsPlatform,
   proComingSoonHere,
   proFeatureComingSoon,
+  landingView,
   PRO_FEATURES,
   PRO_PAY_URL,
   type ProFeature
@@ -38,7 +39,7 @@ const winPorted = (route: string): ProFeature => ({
 // asserted against the catalog so a flipped `platforms` and this list can't drift.
 // Module-scoped because both the featureSupportsPlatform and proFeatureComingSoon
 // describes read it — the gate and the capability check must agree on one list.
-const WIN_PORTED = new Set(['vault', 'clipboard', 'replay'])
+const WIN_PORTED = new Set(['vault', 'clipboard', 'replay', 'day', 'notifications'])
 
 describe('getProFeature', () => {
   it('returns the matching feature for a known route', () => {
@@ -169,6 +170,46 @@ describe('proFeatureComingSoon', () => {
   })
 })
 
+describe('landingView reads the seam, not isMac (the stranded-Day guard)', () => {
+  it('sends free users to Models on every platform (they need a model first)', () => {
+    for (const p of ['darwin', 'win32', 'linux', 'unknown'] as const) {
+      expect(landingView(p, false), `free on ${p}`).toBe('models')
+    }
+  })
+
+  it('lands a Pro user on Day on macOS', () => {
+    expect(landingView('darwin', true)).toBe('day')
+  })
+
+  // THE regression guard for the rule this replaced. The old landing default was
+  // `isPro && isMac() ? 'day' : 'models'`, which returns 'models' on win32 no matter
+  // what the catalog says. With Day ported, nav and gating light it up from
+  // `platforms` — so an isMac-based landing screen would strand a Pro Windows user on
+  // Models. This fails the moment anything reintroduces that check.
+  it('lands a Pro user on Day on Windows now that Day is ported', () => {
+    expect(landingView('win32', true)).toBe('day')
+  })
+
+  // The other half: not "any non-Mac gets Day" either. Day is not ported to linux, so
+  // a Pro linux user must NOT be dropped onto an unavailable tab.
+  it('does not land a Pro user on Day where Day is unsupported', () => {
+    expect(landingView('linux', true)).toBe('models')
+    expect(landingView('unknown', true)).toBe('models')
+  })
+
+  // DRY: assert against the catalog rather than re-hardcoding the platform list, so
+  // this test and `platforms` can never drift. Porting Day to a new platform updates
+  // both sides from the one edit.
+  it('agrees with the day feature’s own platforms list on every platform', () => {
+    const day = getProFeature('day')
+    expect(day).toBeDefined()
+    for (const p of ['darwin', 'win32', 'linux', 'unknown'] as const) {
+      const expected = featureSupportsPlatform(day!, p) ? 'day' : 'models'
+      expect(landingView(p, true), `pro landing on ${p}`).toBe(expected)
+    }
+  })
+})
+
 describe('PRO_FEATURES data integrity', () => {
   it('has a non-empty catalog', () => {
     expect(PRO_FEATURES.length).toBeGreaterThan(0)