diff --git a/include/ghostty.h b/include/ghostty.h
index 681a4e9dc..d2e59b09f 100644
--- a/include/ghostty.h
+++ b/include/ghostty.h
@@ -675,6 +675,7 @@ void ghostty_app_open_config(ghostty_app_t);
 void ghostty_app_update_config(ghostty_app_t, ghostty_config_t);
 bool ghostty_app_needs_confirm_quit(ghostty_app_t);
 bool ghostty_app_has_global_keybinds(ghostty_app_t);
+void ghostty_app_set_color_scheme(ghostty_app_t, ghostty_color_scheme_e);
 
 ghostty_surface_config_s ghostty_surface_config_new();
 
diff --git a/macos/Sources/App/macOS/AppDelegate.swift b/macos/Sources/App/macOS/AppDelegate.swift
index faafa7205..ed257d9ec 100644
--- a/macos/Sources/App/macOS/AppDelegate.swift
+++ b/macos/Sources/App/macOS/AppDelegate.swift
@@ -95,6 +95,9 @@ class AppDelegate: NSObject,
     /// makes our logic very easy.
     private var isVisible: Bool = true
 
+    /// The observer for the app appearance.
+    private var appearanceObserver: NSKeyValueObservation? = nil
+
     override init() {
         terminalManager = TerminalManager(ghostty)
         updaterController = SPUStandardUpdaterController(
@@ -187,6 +190,23 @@ class AppDelegate: NSObject,
             )
         ])
         center.delegate = self
+
+        // Observe our appearance so we can report the correct value to libghostty.
+        self.appearanceObserver = NSApplication.shared.observe(
+            \.effectiveAppearance,
+             options: [.new, .initial]
+        ) { _, change in
+            guard let appearance = change.newValue else { return }
+            guard let app = self.ghostty.app else { return }
+            let scheme: ghostty_color_scheme_e
+            if (appearance.isDark) {
+                scheme = GHOSTTY_COLOR_SCHEME_DARK
+            } else {
+                scheme = GHOSTTY_COLOR_SCHEME_LIGHT
+            }
+
+            ghostty_app_set_color_scheme(app, scheme)
+        }
     }
 
     func applicationDidBecomeActive(_ notification: Notification) {
diff --git a/macos/Sources/Ghostty/Ghostty.App.swift b/macos/Sources/Ghostty/Ghostty.App.swift
index 52a535365..9056e692a 100644
--- a/macos/Sources/Ghostty/Ghostty.App.swift
+++ b/macos/Sources/Ghostty/Ghostty.App.swift
@@ -1212,6 +1212,7 @@ extension Ghostty {
 
                 switch (target.tag) {
                 case GHOSTTY_TARGET_APP:
+                    // Notify the world that the app config changed
                     NotificationCenter.default.post(
                         name: .ghosttyConfigDidChange,
                         object: nil,
@@ -1219,6 +1220,14 @@ extension Ghostty {
                             SwiftUI.Notification.Name.GhosttyConfigChangeKey: config,
                         ]
                     )
+
+                    // We also REPLACE our app-level config when this happens. This lets
+                    // all the various things that depend on this but are still theme specific
+                    // such as split border color work.
+                    guard let app_ud = ghostty_app_userdata(app) else { return }
+                    let ghostty = Unmanaged<App>.fromOpaque(app_ud).takeUnretainedValue()
+                    ghostty.config = config
+
                     return
 
                 case GHOSTTY_TARGET_SURFACE:
diff --git a/src/App.zig b/src/App.zig
index 57b30ada0..279c4e497 100644
--- a/src/App.zig
+++ b/src/App.zig
@@ -67,6 +67,11 @@ font_grid_set: font.SharedGridSet,
 last_notification_time: ?std.time.Instant = null,
 last_notification_digest: u64 = 0,
 
+/// The conditional state of the configuration. See the equivalent field
+/// in the Surface struct for more information. In this case, this applies
+/// to the app-level config and as a default for new surfaces.
+config_conditional_state: configpkg.ConditionalState,
+
 /// Set to false once we've created at least one surface. This
 /// never goes true again. This can be used by surfaces to determine
 /// if they are the first surface.
@@ -95,6 +100,7 @@ pub fn create(
         .mailbox = .{},
         .quit = false,
         .font_grid_set = font_grid_set,
+        .config_conditional_state = .{},
     };
     errdefer app.surfaces.deinit(alloc);
 
@@ -154,11 +160,24 @@ pub fn updateConfig(self: *App, rt_app: *apprt.App, config: *const Config) !void
         try surface.core_surface.handleMessage(.{ .change_config = config });
     }
 
+    // Apply our conditional state. If we fail to apply the conditional state
+    // then we log and attempt to move forward with the old config.
+    // We only apply this to the app-level config because the surface
+    // config applies its own conditional state.
+    var applied_: ?configpkg.Config = config.changeConditionalState(
+        self.config_conditional_state,
+    ) catch |err| err: {
+        log.warn("failed to apply conditional state to config err={}", .{err});
+        break :err null;
+    };
+    defer if (applied_) |*c| c.deinit();
+    const applied: *const configpkg.Config = if (applied_) |*c| c else config;
+
     // Notify the apprt that the app has changed configuration.
     try rt_app.performAction(
         .app,
         .config_change,
-        .{ .config = config },
+        .{ .config = applied },
     );
 }
 
@@ -380,6 +399,33 @@ pub fn keyEvent(
     return true;
 }
 
+/// Call to notify Ghostty that the color scheme for the app has changed.
+/// "Color scheme" in this case refers to system themes such as "light/dark".
+pub fn colorSchemeEvent(
+    self: *App,
+    rt_app: *apprt.App,
+    scheme: apprt.ColorScheme,
+) !void {
+    const new_scheme: configpkg.ConditionalState.Theme = switch (scheme) {
+        .light => .light,
+        .dark => .dark,
+    };
+
+    // If our scheme didn't change, then we don't do anything.
+    if (self.config_conditional_state.theme == new_scheme) return;
+
+    // Setup our conditional state which has the current color theme.
+    self.config_conditional_state.theme = new_scheme;
+
+    // Request our configuration be reloaded because the new scheme may
+    // impact the colors of the app.
+    try rt_app.performAction(
+        .app,
+        .reload_config,
+        .{ .soft = true },
+    );
+}
+
 /// Perform a binding action. This only accepts actions that are scoped
 /// to the app. Callers can use performAllAction to perform any action
 /// and any non-app-scoped actions will be performed on all surfaces.
diff --git a/src/Surface.zig b/src/Surface.zig
index ee2fe1ac5..b2530936a 100644
--- a/src/Surface.zig
+++ b/src/Surface.zig
@@ -359,11 +359,25 @@ const DerivedConfig = struct {
 pub fn init(
     self: *Surface,
     alloc: Allocator,
-    config: *const configpkg.Config,
+    config_original: *const configpkg.Config,
     app: *App,
     rt_app: *apprt.runtime.App,
     rt_surface: *apprt.runtime.Surface,
 ) !void {
+    // Apply our conditional state. If we fail to apply the conditional state
+    // then we log and attempt to move forward with the old config.
+    var config_: ?configpkg.Config = config_original.changeConditionalState(
+        app.config_conditional_state,
+    ) catch |err| err: {
+        log.warn("failed to apply conditional state to config err={}", .{err});
+        break :err null;
+    };
+    defer if (config_) |*c| c.deinit();
+
+    // We want a config pointer for everything so we get that either
+    // based on our conditional state or the original config.
+    const config: *const configpkg.Config = if (config_) |*c| c else config_original;
+
     // Get our configuration
     var derived_config = try DerivedConfig.init(alloc, config);
     errdefer derived_config.deinit();
@@ -481,7 +495,10 @@ pub fn init(
         .io_thr = undefined,
         .size = size,
         .config = derived_config,
-        .config_conditional_state = .{},
+
+        // Our conditional state is initialized to the app state. This
+        // lets us get the most likely correct color theme and so on.
+        .config_conditional_state = app.config_conditional_state,
     };
 
     // The command we're going to execute
diff --git a/src/apprt/embedded.zig b/src/apprt/embedded.zig
index 92137e6d7..ccafb9aa6 100644
--- a/src/apprt/embedded.zig
+++ b/src/apprt/embedded.zig
@@ -1357,6 +1357,22 @@ pub const CAPI = struct {
         return v.hasGlobalKeybinds();
     }
 
+    /// Update the color scheme of the app.
+    export fn ghostty_app_set_color_scheme(v: *App, scheme_raw: c_int) void {
+        const scheme = std.meta.intToEnum(apprt.ColorScheme, scheme_raw) catch {
+            log.warn(
+                "invalid color scheme to ghostty_surface_set_color_scheme value={}",
+                .{scheme_raw},
+            );
+            return;
+        };
+
+        v.core_app.colorSchemeEvent(v, scheme) catch |err| {
+            log.err("error setting color scheme err={}", .{err});
+            return;
+        };
+    }
+
     /// Returns initial surface options.
     export fn ghostty_surface_config_new() apprt.Surface.Options {
         return .{};