fix(mcp): fail startRecording when the camera cannot be opened

src/cli/CliRecordRunner.test.tsx

@@ -82,6 +82,36 @@ describe("CliRecordRunner", () => {
 		expect(recorder.startRecordingImmediately).not.toHaveBeenCalled();
 	});
 
+	it("fails, and stops the starting capture, when the camera turns on but cannot be opened", async () => {
+		vi.mocked(window.electronAPI.cliGetRequest).mockResolvedValueOnce({ ...request, camera: true });
+		recorder.setWebcamEnabled.mockImplementationOnce(async () => {
+			recorder.webcamEnabled = true;
+			return true;
+		});
+		try {
+			const { rerender } = render(<CliRecordRunner />);
+			await waitFor(() => expect(recorder.startRecordingImmediately).toHaveBeenCalledTimes(1));
+			// The acquire failed (another app holds the camera): the recorder turns it back off.
+			recorder.webcamEnabled = false;
+			rerender(<CliRecordRunner />);
+			await waitFor(() =>
+				expect(window.electronAPI.cliDone).toHaveBeenCalledWith(
+					expect.objectContaining({
+						success: false,
+						error: expect.stringContaining("camera could not be opened"),
+					}),
+				),
+			);
+			recorder.recording = true;
+			rerender(<CliRecordRunner />);
+			await waitFor(() => expect(recorder.toggleRecording).toHaveBeenCalledTimes(1));
+			expect(window.electronAPI.cliLog).not.toHaveBeenCalledWith("info", "Recording started");
+		} finally {
+			recorder.webcamEnabled = false;
+			recorder.recording = false;
+		}
+	});
+
 	it("leaves the camera off unless asked", async () => {
 		recorder.setWebcamEnabled.mockClear();
 		render(<CliRecordRunner />);

src/cli/CliRecordRunner.tsx

@@ -253,9 +253,28 @@ export function CliRecordRunner() {
 		recorder.cursorCaptureMode,
 	]);
 
+	// A camera that cannot be opened (held by another app, OpenScreen's own HUD among them on
+	// Linux, or unplugged) turns itself back off in the recorder, which then records without it.
+	// A take asked to have the camera fails instead of reporting success without it (#1303).
+	// biome-ignore lint/correctness/useExhaustiveDependencies: fail is stable
+	useEffect(() => {
+		if (!requestReady?.camera || recorder.webcamEnabled) return;
+		if (phaseRef.current === "done" || recordingStartedAtRef.current !== null) return;
+		void fail(
+			new Error(
+				"The camera could not be opened: another app is using it (OpenScreen itself, when it is running), or it was disconnected",
+			),
+		);
+	}, [requestReady, recorder.webcamEnabled]);
+
 	// Recording state transitions: report start and arm the duration timer.
 	useEffect(() => {
 		const request = requestRef.current;
+		// The take failed while its capture was starting: stop it, nobody is waiting for it.
+		if (recording && phaseRef.current === "done" && recordingStartedAtRef.current === null) {
+			toggleRecordingRef.current();
+			return;
+		}
 		if (recording && recordingStartedAtRef.current === null) {
 			recordingStartedAtRef.current = Date.now();
 			setStatus("Recording…");