--- a/api/cpp/platform.rs
+++ b/api/cpp/platform.rs
@@ -47,6 +47,11 @@
 }
 
 impl WindowAdapter for CppWindowAdapter {
+    #[cfg(target_env = "ohos")]
+    fn internal(&self, _: i_slint_core::InternalToken) -> Option<&dyn i_slint_core::window::WindowAdapterInternal> {
+        Some(self)
+    }
+
     fn window(&self) -> &Window {
         &self.window
     }
@@ -186,6 +191,103 @@
     }
 }
 
+
+// Harmony's native editor and cursor services are provided by the C++ host.
+// Keep this extension target-local; the public C++ adapter ABI stays unchanged.
+#[cfg(target_env = "ohos")]
+mod harmony_services {
+    use super::*;
+    use core::cell::Cell;
+    use i_slint_core::window::{InputMethodRequest, WindowAdapterInternal, WindowInner};
+    type HarmonyOsCallback = unsafe extern "C" fn(*mut c_void, *const c_void, i32,
+        *const u8, usize, usize, usize, f32, f32, f32, f32, i32);
+    std::thread_local! { static CALLBACK: Cell<Option<HarmonyOsCallback>> = const { Cell::new(None) }; }
+    #[unsafe(no_mangle)]
+    pub extern "C" fn crossdesk_slint_set_os_callback(callback: HarmonyOsCallback) {
+        CALLBACK.set(Some(callback));
+    }
+    impl WindowAdapterInternal for CppWindowAdapter {
+        fn input_method_request(&self, request: InputMethodRequest) {
+            let Some(callback) = CALLBACK.get() else { return };
+            let (kind, properties) = match request {
+                InputMethodRequest::Enable(p) => (1, Some(p)),
+                InputMethodRequest::Update(p) => (2, Some(p)),
+                InputMethodRequest::Disable => (0, None),
+                _ => return,
+            };
+            let p = properties.unwrap_or_default();
+            let cursor = p.text[..p.cursor_position].encode_utf16().count();
+            let anchor = p.text[..p.anchor_position.unwrap_or(p.cursor_position)].encode_utf16().count();
+            unsafe { callback(self.user_data, self as *const Self as *const c_void, kind, p.text.as_ptr(), p.text.len(), cursor, anchor,
+                p.cursor_rect_origin.x, p.cursor_rect_origin.y, p.cursor_rect_size.width,
+                p.cursor_rect_size.height, p.input_type as i32); }
+        }
+        fn set_mouse_cursor(&self, cursor: i_slint_core::items::MouseCursor) {
+            if let Some(callback) = CALLBACK.get() {
+                unsafe { callback(self.user_data, self as *const Self as *const c_void, 3, core::ptr::null(), 0, 0, 0,
+                    0., 0., 0., 0., cursor as i32); }
+            }
+        }
+    }
+    // IME commands target the editor that owns the native input session. Use
+    // Slint's normal key handling (selection, clipboard, validation and undo)
+    // without mutating the window's physical modifier state.
+    #[unsafe(no_mangle)]
+    pub unsafe extern "C" fn crossdesk_slint_edit(adapter: *const c_void,
+        text: *const u8, length: usize, modifiers: i32) {
+        use i_slint_core::input::{InternalKeyEvent, KeyEvent, KeyEventType};
+        let Ok(text) = core::str::from_utf8(unsafe { core::slice::from_raw_parts(text, length) }) else { return };
+        let window = WindowInner::from_pub(&unsafe { &*(adapter as *const CppWindowAdapter) }.window);
+        let Some(item) = window.focus_item.borrow().upgrade() else { return };
+        if item.downcast::<i_slint_core::items::TextInput>().is_none() { return; }
+        let mut key_event = KeyEvent::default();
+        key_event.text = text.into();
+        key_event.modifiers.shift = modifiers & 1 != 0;
+        key_event.modifiers.control = modifiers & 2 != 0;
+        for event_type in [KeyEventType::KeyPressed, KeyEventType::KeyReleased] {
+            item.borrow().as_ref().key_event(&InternalKeyEvent {
+                key_event: key_event.clone(), event_type, ..Default::default()
+            }, &window.window_adapter(), &item);
+        }
+    }
+    #[unsafe(no_mangle)]
+    pub unsafe extern "C" fn crossdesk_slint_selection(adapter: *const c_void, anchor: i32, cursor: i32) {
+        let window = WindowInner::from_pub(&unsafe { &*(adapter as *const CppWindowAdapter) }.window);
+        let Some(item) = window.focus_item.borrow().upgrade() else { return };
+        let Some(input) = item.downcast::<i_slint_core::items::TextInput>() else { return };
+        let input = input.as_pin_ref();
+        let text = input.text();
+        // Harmony uses UTF-16 indices; Slint uses UTF-8 byte offsets. Clamp
+        // malformed ranges to character boundaries, including surrogate pairs.
+        let byte_offset = |offset: i32| -> i32 {
+            let mut utf16 = 0;
+            for (byte, ch) in text.char_indices() {
+                if utf16 + ch.len_utf16() > offset.max(0) as usize { return byte as i32; }
+                utf16 += ch.len_utf16();
+            }
+            text.len() as i32
+        };
+        input.set_selection_offsets(&window.window_adapter(), &item, byte_offset(anchor), byte_offset(cursor));
+    }
+    // Called only on the Slint thread while the owning C++ window is alive.
+    #[unsafe(no_mangle)]
+    pub unsafe extern "C" fn crossdesk_slint_composition(adapter: *const c_void,
+        commit: bool, text: *const u8, length: usize) {
+        use i_slint_core::input::{InternalKeyEvent, KeyEvent, KeyEventType};
+        let Ok(text) = core::str::from_utf8(unsafe { core::slice::from_raw_parts(text, length) }) else { return };
+        let mut key_event = KeyEvent::default();
+        key_event.text = text.into();
+        let event = if commit {
+            InternalKeyEvent { event_type: KeyEventType::CommitComposition,
+                key_event, ..Default::default() }
+        } else {
+            InternalKeyEvent { event_type: KeyEventType::UpdateComposition, preedit_text: text.into(),
+                preedit_selection: Some(text.len() as i32..text.len() as i32), ..Default::default() }
+        };
+        WindowInner::from_pub(&unsafe { &*(adapter as *const CppWindowAdapter) }.window).process_key_input(event);
+    }
+}
+
 type PlatformUserData = *mut c_void;
 
 struct CppPlatform {