fix(app): preserve nested list clipboard lines

Flattened child list lines were reparented inside the parent item line, so rich paste targets split markers from their content. Keep every flattened line as a sibling and cover cross-structure selection plus inline-code double-click copying.

packages/app/e2e/browser/assistant-selection-copy.spec.ts

@@ -2,7 +2,22 @@ import type { BrowserContext } from "@playwright/test";
 import { expect, test, type Page } from "../support/fixtures";
 import { openAgentRoute, seedMockAgentWorkspace } from "../support/helpers/mock-agent";
 
+const CROSS_STRUCTURE_MARKDOWN = [
+  "# P1 — High-value UI behavior",
+  "",
+  "5. Claude model and thinking preferences",
+  "",
+  "   - Switch Claude models and confirm each model retains its own thinking choice.",
+  "   - Cover new-workspace drafts, queued launches, schedules, and editing existing schedules.",
+  "   - Confirm Opus 5 exposes the Fast toggle.",
+  "   - Smoke with an older saved Fabel/model alias and with daemon/client version drift.",
+  "",
+  "6. Chat, composer, and timeline stability",
+].join("\n");
+
 const ASSISTANT_MARKDOWN = [
+  CROSS_STRUCTURE_MARKDOWN,
+  "",
   "Direct matches:",
   "",
   "Formatted **strong prose**, _emphasized prose_, and ~~struck prose~~.",
@@ -58,6 +73,10 @@ const ASSISTANT_MARKDOWN = [
 ].join("\n");
 
 const EXPECTED_WHOLE_SELECTION_MARKDOWN = ASSISTANT_MARKDOWN.replace(
+  `${CROSS_STRUCTURE_MARKDOWN}\n\n`,
+  "",
+)
+  .replace(
     "<https://autolink.example.com>",
     "[https://autolink.example.com](https://autolink.example.com)",
   )
@@ -78,18 +97,8 @@ async function allowRichClipboard(context: BrowserContext): Promise<void> {
   await context.grantPermissions(["clipboard-read", "clipboard-write"]);
 }
 
-async function selectAssistantMessage(page: Page): Promise<void> {
+async function selectStructuredClipboardFixture(page: Page): Promise<void> {
-  const assistantMessage = page.getByTestId("assistant-message").filter({
+  await selectAssistantTextRange(page, "Direct matches:", "ready");
-    hasText: "Direct matches:",
-  });
-  await expect(assistantMessage).toBeVisible();
-  await assistantMessage.evaluate((element) => {
-    const selection = window.getSelection();
-    const range = document.createRange();
-    range.selectNodeContents(element);
-    selection?.removeAllRanges();
-    selection?.addRange(range);
-  });
 }
 
 async function selectAssistantElement(page: Page, selector: string): Promise<void> {
@@ -109,6 +118,13 @@ async function selectAssistantText(page: Page, text: string): Promise<void> {
   await selectAssistantTextRange(page, text, text);
 }
 
+async function doubleClickAssistantText(page: Page, text: string): Promise<void> {
+  const assistantMessage = page.getByTestId("assistant-message").filter({
+    hasText: "Direct matches:",
+  });
+  await assistantMessage.getByText(text, { exact: true }).dblclick();
+}
+
 async function selectAssistantTextRange(
   page: Page,
   startText: string,
@@ -275,7 +291,7 @@ test("copying an assistant selection preserves Markdown structure and links", as
       .filter({ hasText: "apply_patch" });
     await expect(inlineCode).toHaveAttribute("data-pmono", "");
 
-    await selectAssistantMessage(page);
+    await selectStructuredClipboardFixture(page);
     await copySelection(page);
 
     const clipboard = await readRichClipboard(page);
@@ -317,6 +333,37 @@ test("copying an assistant selection preserves Markdown structure and links", as
     expect(clipboard.html).toContain('<th style="text-align:right">Right</th>');
     expect(clipboard.html).toContain('<th style="text-align:center">Center</th>');
 
+    await doubleClickAssistantText(page, "apply_patch");
+    await copySelection(page);
+
+    const doubleClickedCodeClipboard = await readRichClipboard(page);
+    expect(doubleClickedCodeClipboard.plainText).toBe("apply_patch");
+    expect(doubleClickedCodeClipboard.html).not.toContain("<code>");
+
+    await selectAssistantTextRange(
+      page,
+      "P1 — High-value UI behavior",
+      "Smoke with an older saved Fabel/model alias and with daemon/client version drift.",
+    );
+    await copySelection(page);
+
+    const headingAndListClipboard = await readRichClipboard(page);
+    expect(headingAndListClipboard.plainText).toBe(
+      [
+        "P1 — High-value UI behavior",
+        "===========================",
+        "",
+        "5. Claude model and thinking preferences",
+        "    - Switch Claude models and confirm each model retains its own thinking choice.",
+        "    - Cover new-workspace drafts, queued launches, schedules, and editing existing schedules.",
+        "    - Confirm Opus 5 exposes the Fast toggle.",
+        "    - Smoke with an older saved Fabel/model alias and with daemon/client version drift.",
+      ].join("\n"),
+    );
+    expect(headingAndListClipboard.html).toMatch(
+      /<h1>P1 — High-value UI behavior<\/h1>\s*<div>5\. Claude model and thinking preferences\s*<\/div><div>- Switch Claude models/,
+    );
+
     await selectAssistantText(page, "First");
     await copySelection(page);
 

packages/app/src/assistant-selection-copy/content.web.ts

@@ -162,9 +162,12 @@ function flattenClipboardListMarkup(html: string): string {
     items.forEach((item, index) => {
       const line = document.createElement("div");
       line.append(start === null ? "- " : `${start + index}. `);
+      const nestedLines: HTMLDivElement[] = [];
       let hasParagraph = false;
       for (const child of Array.from(item.childNodes)) {
-        if (child instanceof HTMLParagraphElement) {
+        if (child instanceof HTMLDivElement) {
+          nestedLines.push(child);
+        } else if (child instanceof HTMLParagraphElement) {
           if (hasParagraph) {
             line.append(document.createElement("br"), document.createElement("br"));
           }
@@ -174,7 +177,7 @@ function flattenClipboardListMarkup(html: string): string {
           line.append(child);
         }
       }
-      replacement.append(line);
+      replacement.append(line, ...nestedLines);
     });
     list.replaceWith(replacement);
   }