@@ -0,0 +1,102 @@
+import { test, expect, type ElectronApplication, type Page } from "@playwright/test";
+import fs from "node:fs";
+import path from "node:path";
+import { currentRow, items, launch, seedHome, tid } from "./support";
+
+/**
+ * How a reply reads in the transcript (#277). This part covers its Markdown: GitHub-flavoured blocks
+ * render as elements, raw HTML stays text, and nothing in a reply runs, fetches or navigates.
+ */
+let app: ElectronApplication;
+let page: Page;
+let home: string;
+let repo: string;
+const dialogs: string[] = [];
+
+const REPLY = [
+  "## Result",
+  "",
+  "| File | Lines |",
+  "| :--- | ---: |",
+  "| a.ts | 12 |",
+  "",
+  "> Run the suite before pushing.",
+  "",
+  "- [x] parser",
+  "- [ ] renderer",
+  "  1. nested step",
+  "",
+  "```ts",
+  "export const answer = 42;",
+  "```",
+  "",
+  'Inert: <img src="https://example.com/x.png" onerror="alert(1)"> and [a script](javascript:alert(2)) and ![chart](https://example.com/c.png).',
+].join("\n");
+
+test.beforeAll(async () => {
+  ({ home, repo } = seedHome());
+  ({ app, page } = await launch(home));
+  page.on("dialog", (dialog) => { dialogs.push(dialog.message()); void dialog.dismiss(); });
+  const script = path.join(home, "rendering-script.json");
+  fs.writeFileSync(script, JSON.stringify([{ content: REPLY }]));
+  await page.evaluate((mock_script) => window.modex!.invoke("settings:update", { mock_script }), script);
+  await page.keyboard.press("Meta+n");
+  await expect(tid(page, "composer-input")).toBeFocused();
+  await tid(page, "composer-input").fill("summarize the change");
+  await page.keyboard.press("Meta+Enter");
+  await expect(tid(page, "thread-view")).toBeVisible({ timeout: 15_000 });
+  await expect(items(page, "assistant")).toHaveCount(1);
+  await expect(currentRow(page)).toHaveAttribute("data-status", "idle");
+});
+
+test.afterAll(async () => {
+  await app?.close();
+  fs.rmSync(home, { recursive: true, force: true });
+  fs.rmSync(repo, { recursive: true, force: true });
+});
+
+test("a reply's tables, quotes, task lists and code render as elements", async () => {
+  const answer = items(page, "assistant").first();
+  await expect(answer.getByRole("heading", { name: "Result" })).toBeVisible();
+  const table = answer.locator("table");
+  await expect(table.getByRole("columnheader")).toHaveText(["File", "Lines"]);
+  await expect(table.getByRole("cell")).toHaveText(["a.ts", "12"]);
+  await expect(answer.locator("blockquote")).toHaveText("Run the suite before pushing.");
+  const boxes = answer.getByRole("checkbox");
+  await expect(boxes).toHaveCount(2);
+  await expect(boxes.nth(0)).toBeChecked();
+  await expect(boxes.nth(1)).not.toBeChecked();
+  await expect(boxes.nth(0)).toBeDisabled();
+  await expect(answer.locator("li ol li")).toHaveText("nested step");
+  await expect(answer.locator('pre.code[data-lang="ts"]')).toHaveText("export const answer = 42;");
+});
+
+test("raw HTML, script links and images in a reply stay inert", async () => {
+  const answer = items(page, "assistant").first();
+  await expect(answer).toContainText('<img src="https://example.com/x.png" onerror="alert(1)">');
+  await expect(answer).toContainText("[a script](javascript:alert(2))");
+  await expect(answer.locator("img")).toHaveCount(0);
+  await expect(answer.locator('a[href^="javascript:"]')).toHaveCount(0);
+  await expect(answer.getByRole("link", { name: "Image: chart" })).toHaveAttribute("href", "https://example.com/c.png");
+  expect(dialogs).toEqual([]);
+});
+
+test("Copy on a code block puts exactly its code on the clipboard and starts nothing", async () => {
+  const answer = items(page, "assistant").first();
+  const block = tid(answer, "code-block");
+  await expect(block).toContainText("ts");
+  // A follow-up suggestion can arrive after the turn ends and grow the composer, which moves the
+  // transcript under the pointer mid-click: the likely cause of the one CI run (39112253838) where
+  // Copied never showed after a 42 ms click. A missed click copies nothing, so clicking again until
+  // Copied shows cannot hide a wrong copy.
+  const copy = tid(block, "code-copy");
+  await expect(async () => {
+    await copy.click();
+    await expect(copy).toHaveText("Copied", { timeout: 1000 });
+  }).toPass({ timeout: 15_000 });
+  expect(await app.evaluate(({ clipboard }) => clipboard.readText())).toBe("export const answer = 42;");
+  await expect(items(page, "tool")).toHaveCount(0);
+  await expect(items(page, "approval")).toHaveCount(0);
+  await expect(items(page, "user")).toHaveCount(1);
+  await expect(currentRow(page)).toHaveAttribute("data-status", "idle");
+});
@@ -0,0 +1,70 @@
+import { test, expect, type ElectronApplication, type Page } from "@playwright/test";
+import fs from "node:fs";
+import path from "node:path";
+import { currentRow, items, launch, resizeWindow, seedHome, tid } from "./support";
+
+/**
+ * Markdown at the 900x600 minimum (#277): with the Review panel open the transcript is about 265 px
+ * wide. A wide table and a long code line scroll inside their own boxes, and no table column is
+ * squeezed to a word, in every theme.
+ */
+let app: ElectronApplication;
+let page: Page;
+let home: string;
+let repo: string;
+
+test.beforeAll(async () => {
+  ({ home, repo } = seedHome());
+  ({ app, page } = await launch(home));
+  await page.keyboard.press("Meta+n");
+  await expect(tid(page, "composer-input")).toBeFocused();
+});
+
+test.afterAll(async () => {
+  await app?.close();
+  fs.rmSync(home, { recursive: true, force: true });
+  fs.rmSync(repo, { recursive: true, force: true });
+});
+
+const WIDE = [
+  "| Path | Change | Detail |",
+  "| --- | --- | --- |",
+  "| apps/desktop/src/renderer/components/transcript/CodeBlock.tsx | added | " + "a long cell that keeps going ".repeat(8) + "|",
+  "",
+  "```ts",
+  "export const aVeryLongLineOfCode = [" + Array.from({ length: 30 }, (_, i) => `"item-${i}"`).join(", ") + "];",
+  "```",
+].join("\n");
+
+test("a reply's tables and code stay readable in every theme at the 900×600 minimum", async ({}, testInfo) => {
+  const script = path.join(home, "wide-script.json");
+  fs.writeFileSync(script, JSON.stringify([{ content: WIDE }]));
+  await page.evaluate((mock_script) => window.modex!.invoke("settings:update", { mock_script }), script);
+  const replies = await items(page, "assistant").count();
+  await tid(page, "composer-input").fill("show the wide table");
+  await page.keyboard.press("Meta+Enter");
+  // Wait for this reply itself, then for the turn to end: the thread was already idle before it.
+  await expect(items(page, "assistant")).toHaveCount(replies + 1, { timeout: 20_000 });
+  await expect(items(page, "assistant").last()).toContainText("aVeryLongLineOfCode");
+  await expect(currentRow(page)).toHaveAttribute("data-status", "idle", { timeout: 20_000 });
+  const answer = items(page, "assistant").last();
+  await expect(answer.locator("table")).toBeVisible();
+  await resizeWindow(app, page, 900, 600);
+  for (const theme of ["graphite", "jev", "coven"]) {
+    await page.evaluate((value) => window.modex!.invoke("settings:update", { theme: value }), theme);
+    await answer.scrollIntoViewIfNeeded();
+    // The page never scrolls sideways: a wide table and a long code line scroll inside their own boxes.
+    expect(await tid(page, "transcript").evaluate((el) => el.scrollWidth - el.clientWidth), `${theme}: no sideways page scroll`).toBeLessThanOrEqual(0);
+    expect(await answer.locator(".md-table").evaluate((el) => el.scrollWidth > el.clientWidth), `${theme}: the table scrolls in its box`).toBe(true);
+    // No column is squeezed to a word: before cells had a minimum width, Detail measured 58 px and its row 1,009 px tall.
+    const narrowest = await answer.locator("td").evaluateAll((cells) => Math.min(...cells.map((c) => c.getBoundingClientRect().width / parseFloat(getComputedStyle(c).fontSize))));
+    expect(narrowest, `${theme}: every cell is at least about ten characters wide`).toBeGreaterThanOrEqual(9.5);
+    expect(await answer.locator("pre.code").evaluate((el) => el.scrollWidth > el.clientWidth), `${theme}: the code scrolls in its box`).toBe(true);
+    await expect(tid(answer, "code-copy")).toBeVisible();
+    await answer.locator("table").evaluate((table) => table.scrollIntoView({ block: "start" }));
+    const shot = await page.screenshot();
+    await testInfo.attach(`markdown-${theme}-900x600`, { body: shot, contentType: "image/png" });
+    // MODEX_SCREENSHOTS=<dir> keeps them for review evidence.
+    if (process.env.MODEX_SCREENSHOTS) fs.writeFileSync(path.join(process.env.MODEX_SCREENSHOTS, `markdown-${theme}-900x600.png`), shot);
+  }
+});
@@ -38,12 +38,16 @@
   },
   "devDependencies": {
     "@playwright/test": "^1.63.0",
+    "@types/mdast": "4.0.4",
     "@types/qrcode": "^1.5.6",
     "@types/react": "^19.0.0",
     "@types/react-dom": "^19.0.0",
     "@vitejs/plugin-react": "^6.1.1",
     "@xterm/addon-fit": "0.11.0",
     "@xterm/xterm": "6.0.0",
+    "mdast-util-from-markdown": "2.0.3",
+    "mdast-util-gfm": "3.1.0",
+    "micromark-extension-gfm": "3.0.0",
     "electron": "^44.4.5",
     "electron-builder": "26.15.3",
     "react": "^19.3.0",