Fix session persistence across page navigation

apps/backend/src/auth/middleware.ts

@@ -246,20 +246,34 @@ export function setSessionCookie(
 	expiresAt: Date,
 	secure: boolean
 ): void {
+	// Expire the former API-only scope before issuing the document-wide cookie.
+	clearSessionCookieAtPath(res, secure, "/api/v1");
 	res.cookie(SESSION_COOKIE_NAME, token, {
 		httpOnly: true,
 		sameSite: "strict",
 		secure,
-		path: "/api/v1",
+		// Next.js authenticates document requests before rendering protected pages.
+		path: "/",
 		expires: expiresAt
 	});
 }
 
 export function clearSessionCookie(res: Response, secure: boolean): void {
+	clearSessionCookieAtPath(res, secure, "/");
+	// Older clients may still retain the scope used before page authentication.
+	clearSessionCookieAtPath(res, secure, "/api/v1");
+}
+
+/** Clears one exact cookie scope because browsers key cookies by name and path. */
+function clearSessionCookieAtPath(
+	res: Response,
+	secure: boolean,
+	path: string
+): void {
 	res.clearCookie(SESSION_COOKIE_NAME, {
 		httpOnly: true,
 		sameSite: "strict",
 		secure,
-		path: "/api/v1"
+		path
 	});
 }

apps/backend/tests/auth.test.ts

@@ -610,7 +610,27 @@ test("session cookies follow the actual LAN or trusted-proxy HTTPS request", asy
 		.set("Origin", "http://dvr.local")
 		.send(payload);
 	assert.equal(http.status, 200);
-	assert.doesNotMatch(http.headers["set-cookie"]?.[0] ?? "", /; Secure/i);
+	const setCookieHeader = http.headers["set-cookie"];
+	const httpCookies = Array.isArray(setCookieHeader)
+		? setCookieHeader
+		: setCookieHeader
+			? [setCookieHeader]
+			: [];
+	const httpCookie = httpCookies.find((cookie) =>
+		/; Path=\/(?:;|$)/i.test(cookie)
+	);
+	assert.ok(httpCookie);
+	assert.doesNotMatch(httpCookie, /; Secure/i);
+	// Server-rendered page requests also need the session to preserve sign-in.
+	assert.match(httpCookie, /; Path=\/(?:;|$)/i);
+	// Remove the old API-only cookie so duplicate token names cannot survive migration.
+	assert.ok(
+		httpCookies.some(
+			(cookie) =>
+				/; Path=\/api\/v1(?:;|$)/i.test(cookie) &&
+				/Expires=Thu, 01 Jan 1970 00:00:00 GMT/i.test(cookie)
+		)
+	);
 	const wrongScheme = await request(app)
 		.post("/auth/login")
 		.set("Host", "dvr.local")