fix(files): keep large source previews responsive (#3665)

Large read-only files bypassed the editor's virtualization and eagerly mounted every highlighted token, which could stall the renderer for seconds and consume gigabytes of memory. Route source previews through bounded platform renderers and reject reads above their display budgets before accumulation.
2026-08-22 10:13:31 +02:00
parent 8905ad4160
commit c763b80824
22 changed files with 589 additions and 183 deletions
@@ -90,6 +90,87 @@ async function seedAgentWithFileLink(input: LinkedFile) {
 }

 test.describe("CodeMirror workspace file editing", () => {
+  test("renders a lockfile-sized read-only source with a bounded CodeMirror DOM", async ({
+    page,
+  }) => {
+    const session = await seedMockAgentWorkspace({
+      repoPrefix: "file-source-lockfile-",
+      title: "Large source",
+      initialPrompt: "Generate a title and a git branch name. Return JSON only.",
+    });
+    const lockfile = `${'{"packages":['}${Array.from({ length: 42_000 }, (_, index) => `{"name":"package-${index}","version":"1.0.0"}`).join(",")}]}`;
+    await writeFile(path.join(session.cwd, "package-lock.json"), lockfile, "utf8");
+
+    try {
+      await openAgentRoute(page, session);
+      await openWorkspaceFile(page, "package-lock.json");
+
+      await expect(page.getByTestId("file-source-editor")).toBeVisible();
+      await expect(editor(page)).toContainText('"package-0"');
+      await expect.poll(() => page.locator(".cm-line").count()).toBeLessThan(200);
+    } finally {
+      await session.cleanup();
+    }
+  });
+
+  test("keeps the app interactive around a plain 11 MB source", async ({ page }) => {
+    const session = await seedMockAgentWorkspace({
+      repoPrefix: "file-source-plain-",
+      title: "Plain large source",
+      initialPrompt: "Generate a title and a git branch name. Return JSON only.",
+    });
+    await writeFile(
+      path.join(session.cwd, "plain.txt"),
+      "plain source\n".repeat(1_050_000),
+      "utf8",
+    );
+
+    try {
+      await openAgentRoute(page, session);
+      await openWorkspaceFile(page, "plain.txt");
+      await expect(page.getByTestId("file-source-editor")).toBeVisible();
+      await expect(editor(page)).toContainText("plain source");
+      await expect.poll(() => page.locator(".cm-line").count()).toBeLessThan(200);
+
+      await page.getByTestId(`workspace-tab-agent_${session.agentId}`).first().click();
+      await expect(page.getByTestId("message-input-root")).toBeVisible();
+      await page.getByTestId("workspace-tab-file_plain.txt").first().click();
+      await expect(page.getByTestId("file-source-editor")).toBeVisible();
+    } finally {
+      await session.cleanup();
+    }
+  });
+
+  test("refuses a file above the display budget and keeps its tab recoverable", async ({
+    page,
+  }) => {
+    const session = await seedMockAgentWorkspace({
+      repoPrefix: "file-source-unsupported-",
+      title: "Unsupported large source",
+      initialPrompt: "Generate a title and a git branch name. Return JSON only.",
+    });
+    await writeFile(
+      path.join(session.cwd, "too-large.txt"),
+      Buffer.alloc(51 * 1024 * 1024),
+      "utf8",
+    );
+
+    try {
+      await openAgentRoute(page, session);
+      await openWorkspaceFile(page, "too-large.txt");
+      await expect(page.getByTestId("file-source-too-large")).toContainText(
+        "This file is too large to display",
+      );
+
+      await page.getByTestId(`workspace-tab-agent_${session.agentId}`).first().click();
+      await expect(page.getByTestId("message-input-root")).toBeVisible();
+      await page.getByTestId("workspace-tab-file_too-large.txt").first().click();
+      await expect(page.getByTestId("file-source-too-large")).toBeVisible();
+    } finally {
+      await session.cleanup();
+    }
+  });
+
  test("opens an assistant file link at its referenced line", async ({ page }) => {
    const target = "target.ts:42";
    const session = await seedAgentWithFileLink({