chore: improve iframe loading time (#18134)

- Pre-load all the embed app iframes
- Avoid reloading the iframe when the selected app changes

site/src/pages/TaskPage/TaskPage.stories.tsx

@@ -1,5 +1,5 @@
 import type { Meta, StoryObj } from "@storybook/react";
-import { spyOn } from "@storybook/test";
+import { expect, spyOn, within } from "@storybook/test";
 import {
 	MockFailedWorkspace,
 	MockStartingWorkspace,
@@ -115,9 +115,8 @@ export const Active: Story = {
 											...MockWorkspaceApp,
 											id: "claude-code",
 											display_name: "Claude Code",
+											slug: "claude-code",
 											icon: "/icon/claude.svg",
-											url: `${window.location.protocol}/iframe.html?viewMode=story&id=pages-terminal--ready&args=&globals=`,
-											external: true,
 											statuses: [
 												MockWorkspaceAppStatus,
 												{
@@ -131,11 +130,13 @@ export const Active: Story = {
 										{
 											...MockWorkspaceApp,
 											id: "vscode",
+											slug: "vscode",
 											display_name: "VS Code Web",
 											icon: "/icon/code.svg",
 										},
 										{
 											...MockWorkspaceApp,
+											slug: "zed",
 											id: "zed",
 											display_name: "Zed",
 											icon: "/icon/zed.svg",
@@ -153,4 +154,15 @@ export const Active: Story = {
 			},
 		});
 	},
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+
+		const vscodeIframe = await canvas.findByTitle("VS Code Web");
+		const zedIframe = await canvas.findByTitle("Zed");
+		const claudeIframe = await canvas.findByTitle("Claude Code");
+
+		expect(vscodeIframe).not.toBeVisible();
+		expect(zedIframe).not.toBeVisible();
+		expect(claudeIframe).toBeVisible();
+	},
 };

site/src/pages/TaskPage/TaskPage.tsx

@@ -19,7 +19,6 @@ import {
 	TooltipProvider,
 	TooltipTrigger,
 } from "components/Tooltip/Tooltip";
-import { useProxy } from "contexts/ProxyContext";
 import {
 	ArrowLeftIcon,
 	ChevronDownIcon,
@@ -27,7 +26,6 @@ import {
 	RotateCcwIcon,
 } from "lucide-react";
 import { AppStatusIcon } from "modules/apps/AppStatusIcon";
-import { getAppHref } from "modules/apps/apps";
 import { useAppLink } from "modules/apps/useAppLink";
 import { AI_PROMPT_PARAMETER_NAME, type Task } from "modules/tasks/tasks";
 import { WorkspaceAppStatus } from "modules/workspaces/WorkspaceAppStatus/WorkspaceAppStatus";
@@ -312,17 +310,6 @@ const TaskApps: FC<TaskAppsProps> = ({ task }) => {
 		throw new Error(`Agent for app ${activeAppId} not found in task workspace`);
 	}
 
-	const { proxy } = useProxy();
-	const [iframeSrc, setIframeSrc] = useState(() => {
-		const src = getAppHref(activeApp, {
-			agent,
-			workspace: task.workspace,
-			path: proxy.preferredPathAppURL,
-			host: proxy.preferredWildcardHostname,
-		});
-		return src;
-	});
-
 	const embeddedApps = apps.filter((app) => !app.external);
 	const externalApps = apps.filter((app) => app.external);
 
@@ -344,7 +331,6 @@ const TaskApps: FC<TaskAppsProps> = ({ task }) => {
 
 								e.preventDefault();
 								setActiveAppId(app.id);
-								setIframeSrc(e.currentTarget.href);
 							}}
 						/>
 					))}
@@ -387,11 +373,16 @@ const TaskApps: FC<TaskAppsProps> = ({ task }) => {
 			</div>
 
 			<div className="flex-1">
-				<iframe
-					title={activeApp.display_name ?? activeApp.slug}
-					className="w-full h-full border-0"
-					src={iframeSrc}
-				/>
+				{embeddedApps.map((app) => {
+					return (
+						<TaskAppIFrame
+							key={app.id}
+							active={activeAppId === app.id}
+							app={app}
+							task={task}
+						/>
+					);
+				})}
 			</div>
 		</main>
 	);
@@ -443,6 +434,37 @@ const TaskAppButton: FC<TaskAppButtonProps> = ({
 	);
 };
 
+type TaskAppIFrameProps = {
+	task: Task;
+	app: WorkspaceApp;
+	active: boolean;
+};
+
+const TaskAppIFrame: FC<TaskAppIFrameProps> = ({ task, app, active }) => {
+	const agent = task.workspace.latest_build.resources
+		.flatMap((r) => r.agents)
+		.filter((a) => !!a)
+		.find((a) => a.apps.some((a) => a.id === app.id));
+
+	if (!agent) {
+		throw new Error(`Agent for app ${app.id} not found in task workspace`);
+	}
+
+	const link = useAppLink(app, {
+		agent,
+		workspace: task.workspace,
+	});
+
+	return (
+		<iframe
+			src={link.href}
+			title={link.label}
+			loading="eager"
+			className={cn([active ? "block" : "hidden", "w-full h-full border-0"])}
+		/>
+	);
+};
+
 export const data = {
 	fetchTask: async (workspaceOwnerUsername: string, workspaceName: string) => {
 		const workspace = await API.getWorkspaceByOwnerAndName(