diff --git a/crates/openpencil-shell-core/src/widgets/dropdown.rs b/crates/openpencil-shell-core/src/widgets/dropdown.rs
index 699d55aa7..8f37f946b 100644
--- a/crates/openpencil-shell-core/src/widgets/dropdown.rs
+++ b/crates/openpencil-shell-core/src/widgets/dropdown.rs
@@ -20,12 +20,24 @@ impl DropdownState {
     /// stays a pure state mutator without borrowing the Dropdown
     /// struct around it.
     ///
-    /// Skips when the key is released or the dropdown has no options
-    /// (no-op rather than wrap-around / panic). Non-navigation keys
-    /// fall through unchanged so widget code can layer additional
-    /// handlers later (e.g. typeahead in Phase D+).
+    /// Skips when the key is released, the dropdown has no options,
+    /// OR an IME composition is in progress (`event.is_composing ==
+    /// true`). The IME-skip is required by spec §2.4: while the
+    /// user is composing CJK / dead-key sequences, arrow keys belong
+    /// to the IME's candidate-picker UI, NOT to widgets that read
+    /// keys directly. Without this guard, every arrow keystroke
+    /// during a composition would cycle the dropdown selection
+    /// behind the IME panel — surfaced by the codex Phase C
+    /// stop-hook ("focused IME textarea lets composing keys mutate
+    /// dropdown state").
+    ///
+    /// Non-navigation keys fall through unchanged so widget code can
+    /// layer additional handlers later (e.g. typeahead in Phase D+).
     pub fn apply_key(&mut self, event: &crate::KeyEvent, option_count: usize) {
-        if event.state != crate::KeyState::Pressed || option_count == 0 {
+        if event.state != crate::KeyState::Pressed
+            || option_count == 0
+            || event.is_composing
+        {
             return;
         }
         match event.key {
diff --git a/crates/openpencil-shell-core/tests/widgets_static.rs b/crates/openpencil-shell-core/tests/widgets_static.rs
index 2db480c99..8b038fdc5 100644
--- a/crates/openpencil-shell-core/tests/widgets_static.rs
+++ b/crates/openpencil-shell-core/tests/widgets_static.rs
@@ -442,3 +442,36 @@ fn dropdown_apply_key_ignores_unrelated_keys() {
     assert_eq!(state.selected, 1);
     assert!(state.open);
 }
+
+#[test]
+fn dropdown_apply_key_ignores_keys_during_ime_composition() {
+    // Spec §2.4 widget rule: skip key dispatch while is_composing is
+    // true. ArrowDown during a CJK composition belongs to the IME's
+    // candidate-picker UI, NOT to the dropdown selection cycle.
+    // Codex Phase C stop-hook (#2): "focused IME textarea lets
+    // composing keys mutate dropdown state."
+    let mut state = DropdownState {
+        selected: 0,
+        open: false,
+    };
+    let composing_arrow = KeyEvent {
+        is_composing: true,
+        ..keydown(NamedKey::ArrowDown)
+    };
+    state.apply_key(&composing_arrow, 3);
+    assert_eq!(state.selected, 0, "composing ArrowDown must not advance");
+    assert!(!state.open, "composing ArrowDown must not open");
+
+    // Same protection for Enter / Escape — IME 'commit' shouldn't
+    // close the dropdown.
+    let mut state2 = DropdownState {
+        selected: 1,
+        open: true,
+    };
+    let composing_enter = KeyEvent {
+        is_composing: true,
+        ..keydown(NamedKey::Enter)
+    };
+    state2.apply_key(&composing_enter, 3);
+    assert!(state2.open, "composing Enter must not close");
+}