fix(desktop): offer diagnostics export from the startup failure screen

The exhausted-retry message tells users to export diagnostics, but the
loading screen hid the only export entry point (HomeShell). The sidecar's
export_diagnostics command does not need the Hub, so call it directly from
the loading screen while the transport is connected.

Co-authored-by: Saoud Rizwan <saoudrizwan@users.noreply.github.com>

apps/examples/desktop-app/webview/components/site-loader.test.tsx

@@ -27,6 +27,11 @@ import { LoadingScreen } from "./views/loading/LoadingScreen";
 import { SiteLoader } from "./views/loading/SiteLoader";
 import { AddProviderContent } from "./views/settings/add-provider";
 
+const invoke = vi.fn();
+vi.mock("@/lib/desktop-client", () => ({
+	desktopClient: { invoke: (...args: unknown[]) => invoke(...args) },
+}));
+
 const container = document.createElement("div");
 document.body.append(container);
 let root = createRoot(container);
@@ -209,6 +214,37 @@ it("distinguishes hub failure and allows retry", () => {
 	act(() => container.querySelector("button")?.click());
 	expect(state.retry).toHaveBeenCalledOnce();
 });
+it("exports diagnostics over the transport when the hub has failed", async () => {
+	invoke.mockResolvedValueOnce({ path: "/tmp/cline-diagnostics.txt" });
+	const state = readiness();
+	state.transport = "connected";
+	state.hub = { state: "failed", attempt: 4, message: "Hub failed" };
+	act(() => root.render(<LoadingScreen readiness={state} />));
+	const buttons = [...container.querySelectorAll("button")];
+	expect(buttons.map((button) => button.textContent)).toEqual([
+		"Retry",
+		"Export diagnostics",
+	]);
+	await act(async () => buttons[1].click());
+	expect(invoke).toHaveBeenCalledWith("export_diagnostics");
+	expect(container.textContent).toContain(
+		"Diagnostics saved to /tmp/cline-diagnostics.txt",
+	);
+});
+it("offers no export while the desktop transport is unavailable", () => {
+	const state = readiness();
+	state.transport = "unavailable";
+	state.startup = {
+		state: "failed",
+		error: "Sidecar exited",
+		exitStatus: null,
+		diagnostics: [],
+	};
+	act(() => root.render(<LoadingScreen readiness={state} />));
+	expect(
+		[...container.querySelectorAll("button")].map((b) => b.textContent),
+	).toEqual(["Retry"]);
+});
 it("shows actionable native startup diagnostics independently of authentication", () => {
 	const state = readiness();
 	state.startup = {

apps/examples/desktop-app/webview/components/views/loading/LoadingScreen.tsx

@@ -1,7 +1,9 @@
 "use client";
 
 import { Loader2 } from "lucide-react";
+import { useState } from "react";
 import type { useDesktopReadiness } from "@/hooks/use-desktop-readiness";
+import { desktopClient } from "@/lib/desktop-client";
 
 export function LoadingScreen({
 	readiness,
@@ -10,6 +12,21 @@ export function LoadingScreen({
 }) {
 	const connected = readiness.transport === "connected";
 	const { hub, startup } = readiness;
+	const [exportStatus, setExportStatus] = useState<string | null>(null);
+	// The sidecar writes the diagnostics report without the Hub, so the
+	// existing export works over the transport while the session service
+	// is still failing.
+	const exportDiagnostics = async () => {
+		setExportStatus("Exporting diagnostics…");
+		try {
+			const result = await desktopClient.invoke<{ path: string }>(
+				"export_diagnostics",
+			);
+			setExportStatus(`Diagnostics saved to ${result.path}`);
+		} catch (error) {
+			setExportStatus(error instanceof Error ? error.message : String(error));
+		}
+	};
 	const failed =
 		!readiness.retrying &&
 		(connected
@@ -76,13 +93,29 @@ export function LoadingScreen({
 							</pre>
 						</details>
 					)}
-					<button
-						type="button"
-						onClick={() => void readiness.retry()}
-						className="rounded-md bg-primary px-4 py-2 text-primary-foreground"
-					>
-						Retry
-					</button>
+					<div className="flex flex-wrap items-center justify-center gap-2">
+						<button
+							type="button"
+							onClick={() => void readiness.retry()}
+							className="rounded-md bg-primary px-4 py-2 text-primary-foreground"
+						>
+							Retry
+						</button>
+						{connected && (
+							<button
+								type="button"
+								onClick={() => void exportDiagnostics()}
+								className="rounded-md border border-border px-4 py-2 text-foreground hover:bg-surface-hover"
+							>
+								Export diagnostics
+							</button>
+						)}
+					</div>
+					{exportStatus && (
+						<p className="break-all text-xs text-muted-foreground">
+							{exportStatus}
+						</p>
+					)}
 				</div>
 			)}
 		</main>