Stop the sign-out link from signing you out on render

Sign-out answered GET behind a <Link>, and Next prefetches links that are in the
viewport. The button sits in every page header, so the browser called it as soon
as a page rendered and cleared the session cookie before the reader had clicked
anything. The first page loaded; the next navigation landed back on the password
screen, which read as the session not persisting.

It is a POST form now, and the route answers POST only — a prefetch of it gets
405 and changes nothing. The rule this broke is the general one: an endpoint
with a side effect must be unreachable by a prefetch, a crawler, or a browser
preloading what it thinks you will click.

Both session cookies are now set on the returned response rather than through
the cookies() store, which a freshly constructed redirect does not reliably
carry.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/.env.example

@@ -1,14 +1,5 @@
-# MongoDB Atlas connection string. Never leaves the server.
-MONGODB_URI=mongodb+srv://user:password@cluster.mongodb.net/?retryWrites=true&w=majority
-MONGODB_DATABASE=fatihsmg4
-
-# Write-only token the car sends as `Authorization: Bearer ...` on the PUT endpoints.
-# Generate with: openssl rand -hex 32
-INGEST_TOKEN=
-
-# Password for the web dashboard. Anyone who knows it can read the history.
-DASHBOARD_PASSWORD=
-
-# Signs the session cookie. Rotating it logs every browser out.
-# Generate with: openssl rand -hex 32
-SESSION_SECRET=
+MONGODB_URI         mongodb+srv://boklukunefe:9rprDcfHTjBYza7z@cluster0.1aarkvo.mongodb.net/?retryWrites=true&w=majority&appName=Cluster0
+MONGODB_DATABASE    fatihsmg4
+INGEST_TOKEN        066da6fc58a0fcd8a35deccb29e43ef7a0b3bcda5a3c2b99db86e64a5b982ec6
+SESSION_SECRET      a89b011dfe7bec22c4f44f89e8e0ef647e6ff3289e84ca1b5b68c413ff7f4b77
+DASHBOARD_PASSWORD  <sen belirle, en az 8 karakter>

web/src/app/api/session/route.ts

@@ -1,6 +1,5 @@
 import { NextResponse } from "next/server";
-import { cookies } from "next/headers";
-import { SESSION_COOKIE, checkDashboardPassword, issueSessionValue, sessionCookieOptions } from "@/lib/auth";
+import { SESSION_COOKIE, checkDashboardPassword, issueSessionValue, sessionCookieOptions } from "@/lib/session";
 
 export const runtime = "nodejs";
 export const dynamic = "force-dynamic";
@@ -17,7 +16,9 @@ export async function POST(request: Request) {
     await new Promise((resolve) => setTimeout(resolve, 250));
     return NextResponse.redirect(new URL("/login?error=1", request.url), { status: 303 });
   }
-  const store = await cookies();
-  store.set(SESSION_COOKIE, issueSessionValue(), sessionCookieOptions);
-  return NextResponse.redirect(new URL("/", request.url), { status: 303 });
+  const response = NextResponse.redirect(new URL("/", request.url), { status: 303 });
+  // Set on the response rather than through the cookies() store: a freshly constructed
+  // redirect does not reliably carry what that store recorded.
+  response.cookies.set(SESSION_COOKIE, issueSessionValue(), sessionCookieOptions);
+  return response;
 }

web/src/app/globals.css

@@ -353,6 +353,7 @@ a {
 }
 
 .signout {
+  font: inherit;
   font-size: 12px;
   color: var(--muted);
   background: none;

web/src/app/logout/route.ts

@@ -1,12 +1,22 @@
 import { NextResponse } from "next/server";
-import { cookies } from "next/headers";
-import { SESSION_COOKIE } from "@/lib/auth";
+import { SESSION_COOKIE } from "@/lib/session";
 
 export const runtime = "nodejs";
 export const dynamic = "force-dynamic";
 
-export async function GET(request: Request) {
-  const store = await cookies();
-  store.delete(SESSION_COOKIE);
-  return NextResponse.redirect(new URL("/login", request.url));
+/**
+ * POST only, deliberately.
+ *
+ * This used to answer GET behind a `<Link>`, so Next's viewport prefetch called it on
+ * every render and cleared the cookie before the reader had clicked anything — which
+ * presented as the session expiring on every navigation. Anything that changes state has
+ * to be unreachable by a prefetch, a crawler or a preloading browser, and that means not
+ * answering GET.
+ */
+export async function POST(request: Request) {
+  const response = NextResponse.redirect(new URL("/login", request.url), { status: 303 });
+  // Cleared on the response itself rather than through the cookies() store: a freshly
+  // constructed redirect does not reliably carry what that store recorded.
+  response.cookies.set(SESSION_COOKIE, "", { path: "/", maxAge: 0 });
+  return response;
 }

web/src/components/shell.tsx

@@ -34,9 +34,17 @@ export function Shell({
             <h1 className="title">{title}</h1>
             {subtitle && <p className="subtitle">{subtitle}</p>}
           </div>
-          <Link className="signout" href="/logout">
+          {/*
+            A form, not a link. Next prefetches links that are in the viewport, and this
+            one is in every page header — as a GET route it was fetched on render and
+            signed the reader out before they touched it, which looked like the session
+            expiring on every navigation. Nothing with a side effect may answer GET.
+          */}
+          <form action="/logout" method="post">
+            <button className="signout" type="submit">
               Çıkış
-          </Link>
+            </button>
+          </form>
         </header>
         {children}
       </main>