fix(export): harden post-merge file handling

electron/ipc/register/export.test.ts

@@ -40,6 +40,7 @@ async function makeTempDir() {
 }
 
 afterEach(async () => {
+	vi.restoreAllMocks();
 	await Promise.allSettled(
 		tempDirs.splice(0).map((dir) => fs.rm(dir, { force: true, recursive: true })),
 	);
@@ -59,4 +60,29 @@ describe("moveExportedTempFile", () => {
 		);
 		await expect(fs.access(tempPath)).rejects.toThrow();
 	});
+
+	it("falls back when Windows reports the destination already exists during initial rename", async () => {
+		const dir = await makeTempDir();
+		const tempPath = path.join(dir, "export-temp.mp4");
+		const destinationPath = path.join(dir, "export-final.mp4");
+		await fs.writeFile(tempPath, "new-export");
+		await fs.writeFile(destinationPath, "previous-export");
+
+		const originalRename = fs.rename.bind(fs);
+		const renameSpy = vi.spyOn(fs, "rename");
+		renameSpy.mockImplementation(async (from, to) => {
+			if (from === tempPath && to === destinationPath) {
+				const error = new Error("destination exists") as NodeJS.ErrnoException;
+				error.code = "EEXIST";
+				throw error;
+			}
+
+			return originalRename(from, to);
+		});
+
+		await moveExportedTempFile(tempPath, destinationPath);
+
+		await expect(fs.readFile(destinationPath, "utf8")).resolves.toBe("new-export");
+		await expect(fs.access(tempPath)).rejects.toThrow();
+	});
 });

electron/ipc/register/export.ts

@@ -58,7 +58,12 @@ export async function moveExportedTempFile(tempPath: string, destinationPath: st
 		return;
 	} catch (error) {
 		const code = (error as NodeJS.ErrnoException).code;
-		if (code !== "EXDEV" && code !== "EPERM" && code !== "ENOTEMPTY") {
+		if (
+			code !== "EXDEV" &&
+			code !== "EPERM" &&
+			code !== "ENOTEMPTY" &&
+			code !== "EEXIST"
+		) {
 			throw error;
 		}
 		// Cross-device or Windows permission quirks — fall back to copy + unlink so
@@ -143,6 +148,10 @@ async function resolveAllowedReadableFilePath(
 	}
 
 	const resolvedPath = path.resolve(filePath);
+	if (!isAllowedLocalReadPath(resolvedPath)) {
+		throw new Error(`${label} is not approved for local reads`);
+	}
+
 	const realPath = await fs.realpath(resolvedPath).catch(() => null);
 	if (!realPath) {
 		throw new Error(`${label} does not exist`);