diff --git a/Relay/ContentView.swift b/Relay/ContentView.swift
index 22aa9e4..db85567 100644
--- a/Relay/ContentView.swift
+++ b/Relay/ContentView.swift
@@ -56,7 +56,12 @@ struct ContentView: View {
             }
         }
         .relayErrorAlert()
-        .frame(minWidth: 700, minHeight: 500)
+        // Sized to fit a quarter-screen tile on a 14" MacBook Pro at its
+        // default scaled resolution (1512×982 pt → quarter ≈ 756×491), with a
+        // few points of margin for macOS tiling gaps. The width must also clear
+        // the sidebar overflow invariant: rail 52 + sidebar max 300 + a usable
+        // timeline (400) = 752.
+        .frame(minWidth: 752, minHeight: 480)
     }
 }
 
diff --git a/Relay/Views/MainView.swift b/Relay/Views/MainView.swift
index 2b6de55..d9a805b 100644
--- a/Relay/Views/MainView.swift
+++ b/Relay/Views/MainView.swift
@@ -248,7 +248,12 @@ struct MainView: View { // swiftlint:disable:this type_body_length
                 spaceRailView
             }
         }
-        .navigationSplitViewColumnWidth(min: 160, ideal: 300, max: 360)
+        // Keep the sidebar narrow enough that, even at its max, it plus the
+        // 52pt space rail and a usable timeline fit inside the 760pt minimum
+        // window — otherwise NavigationSplitView overflows the window (the
+        // sidebar shoves off the left edge and the detail spills past the
+        // right) instead of compressing the user-dragged sidebar.
+        .navigationSplitViewColumnWidth(min: 160, ideal: 280, max: 300)
     }
 
     // MARK: - Detail