diff --git a/packages/ui/src/components/chat/composer/editor/ComposerEditor.tsx b/packages/ui/src/components/chat/composer/editor/ComposerEditor.tsx
index 41a2825f..c248a53f 100644
--- a/packages/ui/src/components/chat/composer/editor/ComposerEditor.tsx
+++ b/packages/ui/src/components/chat/composer/editor/ComposerEditor.tsx
@@ -344,6 +344,10 @@ export const ComposerEditor = React.forwardRef<ComposerEditorHandle, ComposerEdi
             if (!view) return;
             const current = view.state.doc.toString();
             if (current === value) return;
+            // Skip every controlled writeback while the browser is composing.
+            // A stale value echo can differ from CodeMirror's newer document,
+            // and replacing it would interrupt the IME session and move the caret.
+            if (view.compositionStarted) return;
             view.dispatch({
                 changes: { from: 0, to: current.length, insert: value },
                 // An external rewrite (draft restore, history navigation,
diff --git a/packages/ui/src/components/chat/composer/editor/__tests__/writebackCompositionGuard.test.ts b/packages/ui/src/components/chat/composer/editor/__tests__/writebackCompositionGuard.test.ts
new file mode 100644
index 00000000..94df2c8f
--- /dev/null
+++ b/packages/ui/src/components/chat/composer/editor/__tests__/writebackCompositionGuard.test.ts
@@ -0,0 +1,28 @@
+import { describe, expect, test } from 'bun:test';
+import { readFileSync } from 'node:fs';
+
+const composerEditorSource = readFileSync(
+    new URL('../ComposerEditor.tsx', import.meta.url),
+    'utf-8',
+);
+
+const writebackEffect = (): string => {
+    const start = composerEditorSource.indexOf('// Controlled value:');
+    expect(start).toBeGreaterThan(-1);
+    const end = composerEditorSource.indexOf('}, [value]);', start);
+    expect(end).toBeGreaterThan(start);
+    return composerEditorSource.slice(start, end);
+};
+
+describe('composer value writeback composition guard (issue #2527)', () => {
+    test('checks equality, then composition, before dispatching', () => {
+        const effect = writebackEffect();
+        const equalityCheck = effect.indexOf('if (current === value) return;');
+        const compositionGuard = effect.indexOf('if (view.compositionStarted) return;');
+        const dispatch = effect.indexOf('view.dispatch({');
+
+        expect(equalityCheck).toBeGreaterThan(-1);
+        expect(compositionGuard).toBeGreaterThan(equalityCheck);
+        expect(dispatch).toBeGreaterThan(compositionGuard);
+    });
+});