diff --git a/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceFeature.swift b/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceFeature.swift
index b33d8e9..4f43c62 100644
--- a/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceFeature.swift
+++ b/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceFeature.swift
@@ -28,6 +28,7 @@ struct LoopWorkspaceFeature {
     /// `@State` because the *toggle* lives in the window toolbar, which `AppView` owns —
     /// and a control and the thing it controls cannot hold the answer separately.
     var isRailVisible = LoopWorkspaceRail.loadVisible()
+    var hasCustomRailVisibility = LoopWorkspaceRail.hasStoredVisibility()
     /// How wide the rail is, after any drag on its edge. Persisted like its visibility:
     /// someone who widened it to read beats did not mean only this session.
     var railWidth = LoopWorkspaceRail.loadWidth()
@@ -109,6 +110,7 @@ struct LoopWorkspaceFeature {
     /// and handled up there, the way `.nodeTapped` already is.
     /// ⌥G, and the toolbar's trailing panel toggle.
     case railToggled
+    case mailroomContentChanged(hasContent: Bool)
     /// The rail's leading edge was dragged. Sent once, on release — a per-frame action
     /// would put a reducer run and a `UserDefaults` write behind every pixel.
     case railWidthChanged(CGFloat)
@@ -273,9 +275,15 @@ struct LoopWorkspaceFeature {
 
       case .railToggled:
         state.isRailVisible.toggle()
+        state.hasCustomRailVisibility = true
         LoopWorkspaceRail.saveVisible(state.isRailVisible)
         return .none
 
+      case .mailroomContentChanged(let hasContent):
+        guard hasContent, !state.hasCustomRailVisibility else { return .none }
+        state.isRailVisible = true
+        return .none
+
       case .railWidthChanged(let width):
         state.railWidth = LoopWorkspaceRail.clamped(width)
         LoopWorkspaceRail.saveWidth(state.railWidth)
diff --git a/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceRail.swift b/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceRail.swift
index 11826f2..2254e97 100644
--- a/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceRail.swift
+++ b/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceRail.swift
@@ -142,8 +142,11 @@ struct LoopWorkspaceRail: View {
     UserDefaults.standard.set(folded, forKey: summaryFoldedDefaultsKey)
   }
 
-  /// **Off** until someone asks for it. It used to default on, which meant every loop
-  /// that feeds nothing opened with 212 points of empty panel beside its terminal.
+  static func hasStoredVisibility() -> Bool {
+    UserDefaults.standard.object(forKey: visibleDefaultsKey) as? Bool != nil
+  }
+
+  /// Starts hidden; Mailroom content may reveal it until a person chooses otherwise.
   static func loadVisible() -> Bool {
     UserDefaults.standard.object(forKey: visibleDefaultsKey) as? Bool ?? false
   }
diff --git a/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceView.swift b/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceView.swift
index 33022d2..fe180ea 100644
--- a/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceView.swift
+++ b/graphcode/Sources/Features/LoopWorkspace/LoopWorkspaceView.swift
@@ -51,6 +51,12 @@ struct LoopWorkspaceView: View {
     .frame(maxWidth: .infinity, maxHeight: .infinity)
     .overlay { expandedBoard }
     .onReceive(CanvasClock.tick) { now = $0 }
+    .onChange(of: mailroomHasContent, initial: true) { _, hasContent in
+      store.send(.mailroomContentChanged(hasContent: hasContent))
+    }
+    .onChange(of: store.id) { _, _ in
+      store.send(.mailroomContentChanged(hasContent: mailroomHasContent))
+    }
     .onDisappear { store.send(.workspaceLeft) }
     // The folder header goes in the toolbar, not in the `VStack` above, and the pane
     // does *not* claim the titlebar inset. Both were tried: `.ignoresSafeArea(.top)`
@@ -142,6 +148,10 @@ struct LoopWorkspaceView: View {
     LoopWorkspaceRail.hasContent(node: store.node, graph: store.graph)
   }
 
+  private var mailroomHasContent: Bool {
+    MailroomPresentation.hasContent(graph: store.graph, enabled: mailroomEnabled)
+  }
+
   private var railShortcut: some View {
     Button("") { store.send(.railToggled) }
       .keyboardShortcut("g", modifiers: .option)
diff --git a/graphcode/Tests/LoopWorkspaceFeatureTests.swift b/graphcode/Tests/LoopWorkspaceFeatureTests.swift
index 740c236..47dda5a 100644
--- a/graphcode/Tests/LoopWorkspaceFeatureTests.swift
+++ b/graphcode/Tests/LoopWorkspaceFeatureTests.swift
@@ -10,7 +10,7 @@ import Testing
 /// persists via `TerminalLayoutStore`, so these also incidentally cover that the right
 /// save happens at the right time — a temp-directory-backed store is injected so tests
 /// never touch the app's real Application Support folder.
-@Suite
+@Suite(.serialized)
 struct LoopWorkspaceFeatureTests {
   /// Records what the reducer asks `TerminalSurfaceClient` to end: the attach going
   /// away (`retired`) and the zmx sessions being terminated behind it (`killed`).
@@ -443,7 +443,10 @@ struct LoopWorkspaceFeatureTests {
     ) { LoopWorkspaceFeature() }
     store.exhaustivity = .off
 
-    await store.send(.railToggled) { $0.isRailVisible = true }
+    await store.send(.railToggled) {
+      $0.isRailVisible = true
+      $0.hasCustomRailVisibility = true
+    }
     #expect(LoopWorkspaceRail.loadVisible())
   }
 
@@ -459,3 +462,65 @@ struct LoopWorkspaceFeatureTests {
     #expect(LoopWorkspaceRail.loadVisible() == false)
   }
 }
+
+extension LoopWorkspaceFeatureTests {
+  @Test(arguments: [false, true])
+  @MainActor
+  func mailroomContentRevealsTheRailWithoutSavingAUserPreference(existingContent: Bool) async {
+    var state = makeState()
+    state.isRailVisible = false
+    state.hasCustomRailVisibility = false
+    let store = makeStore(state)
+
+    if !existingContent {
+      await store.send(.mailroomContentChanged(hasContent: false))
+      #expect(!store.state.isRailVisible)
+    }
+    await store.send(.mailroomContentChanged(hasContent: true)) {
+      $0.isRailVisible = true
+    }
+    #expect(!store.state.hasCustomRailVisibility)
+    await store.send(.mailroomContentChanged(hasContent: true))
+    await store.send(.mailroomContentChanged(hasContent: false))
+    #expect(store.state.isRailVisible)
+  }
+
+  @Test
+  @MainActor
+  func hidingTheRailPreventsMailFromReopeningItAcrossWorkspaces() async {
+    let key = LoopWorkspaceRail.visibleDefaultsKey
+    let saved = UserDefaults.standard.object(forKey: key)
+    UserDefaults.standard.removeObject(forKey: key)
+    defer {
+      if let saved {
+        UserDefaults.standard.set(saved, forKey: key)
+      } else {
+        UserDefaults.standard.removeObject(forKey: key)
+      }
+    }
+    #expect(!LoopWorkspaceRail.hasStoredVisibility())
+    let store = makeStore(makeState())
+    await store.send(.mailroomContentChanged(hasContent: true)) {
+      $0.isRailVisible = true
+    }
+    #expect(!LoopWorkspaceRail.hasStoredVisibility())
+    await store.send(.railToggled) {
+      $0.isRailVisible = false
+      $0.hasCustomRailVisibility = true
+    }
+    await store.send(.mailroomContentChanged(hasContent: false))
+    await store.send(.mailroomContentChanged(hasContent: true))
+    #expect(!store.state.isRailVisible)
+    #expect(LoopWorkspaceRail.hasStoredVisibility())
+    #expect(!LoopWorkspaceRail.loadVisible())
+
+    let reopened = makeStore(makeState())
+    #expect(reopened.state.hasCustomRailVisibility)
+    await reopened.send(.mailroomContentChanged(hasContent: true))
+    #expect(!reopened.state.isRailVisible)
+    await reopened.send(.railToggled) {
+      $0.isRailVisible = true
+    }
+    #expect(LoopWorkspaceRail.loadVisible())
+  }
+}