diff --git a/src/Surface.zig b/src/Surface.zig
index d19f61d11..fa7af108e 100644
--- a/src/Surface.zig
+++ b/src/Surface.zig
@@ -1152,6 +1152,22 @@ pub fn focusCallback(self: *Surface, focused: bool) !void {
 
     // Schedule render which also drains our mailbox
     try self.queueRender();
+
+    // Notify the app about focus in/out if it is requesting it
+    {
+        self.renderer_state.mutex.lock();
+        const focus_event = self.io.terminal.modes.focus_event;
+        self.renderer_state.mutex.unlock();
+
+        if (focus_event) {
+            const seq = if (focused) "\x1b[I" else "\x1b[O";
+            _ = self.io_thread.mailbox.push(.{
+                .write_stable = seq,
+            }, .{ .forever = {} });
+
+            try self.io_thread.wakeup.notify();
+        }
+    }
 }
 
 pub fn refreshCallback(self: *Surface) !void {
diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index 4c01f1b00..db801a15c 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -80,6 +80,7 @@ modes: packed struct {
     deccolm: bool = false, // 3,
     deccolm_supported: bool = false, // 40
 
+    focus_event: bool = false, // 1004
     mouse_alternate_scroll: bool = true, // 1007
     mouse_event: MouseEvents = .none,
     mouse_format: MouseFormat = .x10,
diff --git a/src/terminal/ansi.zig b/src/terminal/ansi.zig
index 228895972..e7d3f0a52 100644
--- a/src/terminal/ansi.zig
+++ b/src/terminal/ansi.zig
@@ -95,6 +95,9 @@ pub const Mode = enum(u16) {
     /// to track mouse movement.
     mouse_event_any = 1003,
 
+    /// Send focus in/out events.
+    focus_event = 1004,
+
     /// Report mouse position in the utf8 format to support larger screens.
     mouse_format_utf8 = 1005,
 
diff --git a/src/termio/Exec.zig b/src/termio/Exec.zig
index 617e0b156..a9632d799 100644
--- a/src/termio/Exec.zig
+++ b/src/termio/Exec.zig
@@ -1061,6 +1061,8 @@ const StreamHandler = struct {
 
             .mouse_alternate_scroll => self.terminal.modes.mouse_alternate_scroll = enabled,
 
+            .focus_event => self.terminal.modes.focus_event = enabled,
+
             else => if (enabled) log.warn("unimplemented mode: {}", .{mode}),
         }
     }