fix(web-shell): stop stacking duplicate copies when restoring prompt text

packages/web-shell/client/hooks/useQueuedPrompts.test.ts

@@ -0,0 +1,44 @@
+import { describe, expect, it } from 'vitest';
+import { mergeRestoredPromptText } from './useQueuedPrompts';
+
+// Regression for #7128: restoration paths can fire more than once for the
+// same prompt (failed submit + reconnect/refresh, queue clear racing an
+// abort), and a user retrying an identical message restores identical text.
+// Stacking those copies is what surfaced as "sent messages concatenated back
+// into the input box after refresh".
+describe('mergeRestoredPromptText', () => {
+  it('fills an empty editor with the restored text', () => {
+    expect(mergeRestoredPromptText('', 'hello')).toBe('hello');
+    expect(mergeRestoredPromptText('   ', 'hello')).toBe('hello');
+  });
+
+  it('prepends above a different draft the user is typing', () => {
+    expect(mergeRestoredPromptText('draft', 'restored')).toBe(
+      'restored\ndraft',
+    );
+  });
+
+  it('is a no-op when the same text was already restored', () => {
+    expect(mergeRestoredPromptText('hello', 'hello')).toBe('hello');
+  });
+
+  it('is a no-op when the text already sits at the top of the editor', () => {
+    expect(mergeRestoredPromptText('hello\ndraft', 'hello')).toBe(
+      'hello\ndraft',
+    );
+  });
+
+  it('stays idempotent across repeated restores of the same prompt', () => {
+    let editor = '';
+    for (let i = 0; i < 3; i++) {
+      editor = mergeRestoredPromptText(editor, '用python写一个hello world');
+    }
+    expect(editor).toBe('用python写一个hello world');
+  });
+
+  it('does not treat a same-prefix but different first line as a duplicate', () => {
+    expect(mergeRestoredPromptText('hello world\ndraft', 'hello')).toBe(
+      'hello\nhello world\ndraft',
+    );
+  });
+});

packages/web-shell/client/hooks/useQueuedPrompts.ts

@@ -53,6 +53,21 @@ interface UseQueuedPromptsArgs {
 
 const MAX_COMPLETED_PROMPT_IDS = 100;
 
+/**
+ * Merge a restored prompt's text into the editor content. Restoration paths
+ * (failed submits, failed mid-turn inserts, queue clears) prepend the prompt
+ * above whatever the user is currently typing — but several of them can fire
+ * for the same prompt across reconnects/refreshes, and a user retrying an
+ * identical message produces the same text twice. Stacking those copies is
+ * what #7128 reports as "inputs concatenated after refresh", so restoring
+ * text that is already present at the top of the editor is a no-op.
+ */
+export function mergeRestoredPromptText(current: string, text: string): string {
+  if (!current.trim()) return text;
+  if (current === text || current.startsWith(`${text}\n`)) return current;
+  return `${text}\n${current}`;
+}
+
 type RefreshPendingPromptsResult =
   | 'refreshed'
   | 'skipped'
@@ -286,8 +301,10 @@ export function useQueuedPrompts({
         return;
       }
       const current = editorRef.current?.getText() ?? '';
-      const next = current.trim() ? `${text}\n${current}` : text;
-      editorRef.current?.setText(next);
+      const next = mergeRestoredPromptText(current, text);
+      if (next !== current) {
+        editorRef.current?.setText(next);
+      }
       if (images && images.length > 0) {
         editorRef.current?.restoreImages(images);
       }