diff --git a/Sources/GhosttyTerminalView.swift b/Sources/GhosttyTerminalView.swift
index 2ee395f0..5ff4359a 100644
--- a/Sources/GhosttyTerminalView.swift
+++ b/Sources/GhosttyTerminalView.swift
@@ -2677,6 +2677,15 @@ final class TerminalSurface: Identifiable, ObservableObject {
 
     private(set) var surface: ghostty_surface_t?
     private weak var attachedView: GhosttyNSView?
+
+    /// Whether the runtime Ghostty surface exists and has not begun teardown.
+    ///
+    /// Use this before passing `surface` to Ghostty C APIs that dereference the
+    /// pointer (e.g. `ghostty_surface_inherited_config`, `ghostty_surface_quicklook_font`).
+    /// A non-nil `surface` alone is not sufficient — the underlying native state may
+    /// already be closing or closed.
+    var hasLiveSurface: Bool { surface != nil && portalLifecycleState == .live }
+
     /// Whether the terminal surface view is currently attached to a window.
     ///
     /// Use the hosted view rather than the inner surface view, since the surface can be
diff --git a/Sources/Workspace.swift b/Sources/Workspace.swift
index 3734b412..ed36d8fb 100644
--- a/Sources/Workspace.swift
+++ b/Sources/Workspace.swift
@@ -26,6 +26,13 @@ func cmuxCurrentSurfaceFontSizePoints(_ surface: ghostty_surface_t) -> Float? {
         return nil
     }
 
+    // Validate the font pointer is a live heap allocation before interpreting
+    // it as a CTFont. ghostty_surface_quicklook_font returns an unretained
+    // pointer that can become stale on Intel Macs (#1496, #1870).
+    guard malloc_size(quicklookFont) > 0 else {
+        return nil
+    }
+
     let ctFont = Unmanaged<CTFont>.fromOpaque(quicklookFont).takeUnretainedValue()
     let points = Float(CTFontGetSize(ctFont))
     guard points > 0 else { return nil }
@@ -6797,7 +6804,8 @@ final class Workspace: Identifiable, ObservableObject {
 
     private func rememberTerminalConfigInheritanceSource(_ terminalPanel: TerminalPanel) {
         lastTerminalConfigInheritancePanelId = terminalPanel.id
-        if let sourceSurface = terminalPanel.surface.surface,
+        if terminalPanel.surface.hasLiveSurface,
+           let sourceSurface = terminalPanel.surface.surface,
            let runtimePoints = cmuxCurrentSurfaceFontSizePoints(sourceSurface) {
             let existing = terminalInheritanceFontPointsByPanelId[terminalPanel.id]
             if existing == nil || abs((existing ?? runtimePoints) - runtimePoints) > 0.05 {
@@ -6895,7 +6903,8 @@ final class Workspace: Identifiable, ObservableObject {
             preferredPanelId: preferredPanelId,
             inPane: preferredPaneId
         ) {
-            guard let sourceSurface = terminalPanel.surface.surface else { continue }
+            guard terminalPanel.surface.hasLiveSurface,
+                  let sourceSurface = terminalPanel.surface.surface else { continue }
             var config = cmuxInheritedSurfaceConfig(
                 sourceSurface: sourceSurface,
                 context: GHOSTTY_SURFACE_CONTEXT_SPLIT