fix(web): preserve selected text when copying over HTTP (#2120)

Co-authored-by: chenyicun <chenyicun@msh.team>

.changeset/fix-web-clipboard-paste.md

@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/kimi-code": patch
+---
+
+web: Fix copying selected chat text over plain HTTP from replacing the clipboard with an event placeholder.

apps/kimi-web/src/components/chat/Markdown.vue

@@ -16,7 +16,7 @@ import { useIsDark } from '../../composables/useIsDark';
 import type { FilePreviewRequest } from '../../types';
 import { collectFilePathAliases, findFilePathLinks } from '../../lib/filePathLinks';
 import { markdownRenderPlan } from '../../lib/markdownPerformance';
-import { copyTextToClipboard } from '../../lib/clipboard';
+import { copyCodeBlockFallback, copyTextToClipboard } from '../../lib/clipboard';
 import * as katexWorkerModule from 'markstream-vue/workers/katexRenderer.worker?worker&type=module';
 import * as mermaidWorkerModule from 'markstream-vue/workers/mermaidParser.worker?worker&type=module';
 import Tooltip from '../ui/Tooltip.vue';
@@ -338,15 +338,6 @@ const codeBlockProps = {
   loading: false,
 };
 
-function copyCodeBlockFallback(code: string): void {
-  // markstream emits `copy` even when it skipped the write because the
-  // Clipboard API is unavailable. Reuse our plain-HTTP fallback in that case,
-  // while avoiding a duplicate write after markstream succeeds on HTTPS.
-  const clipboard = typeof navigator !== 'undefined' ? navigator.clipboard : undefined;
-  if (clipboard && typeof clipboard.writeText === 'function') return;
-  void copyTextToClipboard(code);
-}
-
 // Root cause for the "large session turns into code skeletons" failure:
 // markstream mounts every code block in the loaded transcript, then shiki has
 // to tokenize all of them. `loading: false` removes the visible skeleton gate,

apps/kimi-web/src/lib/clipboard.ts

@@ -30,6 +30,18 @@ export async function copyTextToClipboard(text: string): Promise<boolean> {
   return legacyCopy(text);
 }
 
+/**
+ * Complete markstream's code-block copy on plain HTTP without intercepting
+ * native selection-copy events that bubble through MarkdownRender.
+ */
+export function copyCodeBlockFallback(payload: unknown): void {
+  if (typeof payload !== 'string') return;
+
+  const clipboard = typeof navigator !== 'undefined' ? navigator.clipboard : undefined;
+  if (clipboard && typeof clipboard.writeText === 'function') return;
+  void copyTextToClipboard(payload);
+}
+
 function legacyCopy(text: string): boolean {
   if (typeof document === 'undefined' || typeof document.execCommand !== 'function') {
     return false;

apps/kimi-web/test/clipboard.test.ts

@@ -1,8 +1,9 @@
+// Scenario: clipboard writes in secure and plain-HTTP web contexts.
+// Responsibilities: preserve native selection copies and provide the legacy
+// code-block fallback. The test stubs only navigator/document browser APIs.
+// Run: pnpm --filter @moonshot-ai/kimi-web test -- clipboard.test.ts
 import { afterEach, describe, expect, it, vi } from 'vitest';
-import { copyTextToClipboard } from '../src/lib/clipboard';
-
-// The web test suite runs in the default node environment (no jsdom), so we
-// mock the tiny `navigator` / `document` surface that the helper touches.
+import { copyCodeBlockFallback, copyTextToClipboard } from '../src/lib/clipboard';
 
 interface FakeDocument {
   execCommand: ReturnType<typeof vi.fn>;
@@ -78,3 +79,26 @@ describe('copyTextToClipboard', () => {
     await expect(copyTextToClipboard('nope')).resolves.toBe(false);
   });
 });
+
+describe('code-block copy fallback', () => {
+  it('does not overwrite selected text when a native copy event bubbles on plain HTTP', () => {
+    installNavigator(undefined);
+    const doc = installDocument(true);
+    const copyEvent = { toString: () => '[object ClipboardEvent]' };
+
+    copyCodeBlockFallback(copyEvent);
+
+    expect(doc.execCommand).not.toHaveBeenCalled();
+    expect(doc.textarea.value).toBe('');
+  });
+
+  it('copies emitted code text when the Clipboard API is unavailable', () => {
+    installNavigator(undefined);
+    const doc = installDocument(true);
+
+    copyCodeBlockFallback('const host = "example.test";');
+
+    expect(doc.execCommand).toHaveBeenCalledWith('copy');
+    expect(doc.textarea.value).toBe('const host = "example.test";');
+  });
+});