diff --git a/docs/maintainers/session-cookie-transport.md b/docs/maintainers/session-cookie-transport.md
index 744468f4..f9eda16c 100644
--- a/docs/maintainers/session-cookie-transport.md
+++ b/docs/maintainers/session-cookie-transport.md
@@ -1,32 +1,43 @@
 # Session Cookie Transport Decision
 
-**Date:** 2026-08-05
-**Status:** Production cookies require HTTPS.
+**Date:** 2026-08-01
+**Status:** Compatibility decision; HTTPS migration remains follow-up work.
 
 SeerrNG uses an `express-session` cookie to carry the authenticated browser
 session, including the session created by Plex sign-in. The current
-configuration uses a secure session cookie in production:
+configuration uses `secure: 'auto'`:
 
-- Production sets the `Secure` attribute unconditionally. When SeerrNG is
-  behind a trusted TLS terminator, `express-session` uses
-  `X-Forwarded-Proto: https` to validate the request transport.
-- Development also sets `Secure`; local browser testing must use HTTPS (or a
-  test client that does not require a browser cookie).
+- When SeerrNG is reached through HTTPS, or a trusted TLS terminator forwards
+  `X-Forwarded-Proto: https`, the session cookie receives the `Secure`
+  attribute.
+- When SeerrNG is reached directly over HTTP, the browser can store and send
+  the cookie over HTTP.
 
-## Why production requires HTTPS
+## Why `secure: true` is not being enabled unconditionally
 
-The production deployment uses `https://request.snape.tech` and has proxy
-trust enabled for its TLS terminator. A browser must use that HTTPS endpoint
-for production sign-in. Direct `http://kspls0:5055` access is a diagnostic
-health-check path, not a supported browser authentication origin.
+The direct deployment at `http://kspls0:5055` depends on the HTTP session
+cookie. Making the cookie unconditionally secure causes the browser to reject
+that cookie on the HTTP origin. The Plex OAuth result then cannot be resumed
+in the SeerrNG browser session, so Plex sign-in to the app fails. The same
+change would break other direct-HTTP and LAN deployments.
 
-This prevents an authenticated session from being sent over clear-text HTTP.
-The `js/clear-text-cookie` finding that motivated this change should resolve in
-the next CodeQL scan; it must not be dismissed or hidden with a query
-configuration.
+This is a compatibility/security tradeoff, not a CodeQL false positive. The
+`js/clear-text-cookie` finding at `server/index.ts:323` is accurate for direct
+HTTP deployments. It must remain visible; it must not be dismissed, ignored,
+or hidden with a CodeQL model or query configuration.
 
 ## Chosen behavior
 
-All session cookies are secure, `httpOnly`, and use the existing CSRF-dependent
-`SameSite` policy. The `development` flag only controls whether Express trusts
-a forwarded proxy protocol.
+Preserve `secure: 'auto'` so Plex sign-in and existing HTTP deployments keep
+working, while ensuring HTTPS deployments receive secure session cookies. The
+remaining risk is that an HTTP deployment exposes the authenticated session to
+anyone able to observe or modify that network traffic.
+
+## Resolution path
+
+To remove the finding without breaking Plex sign-in, deploy SeerrNG behind a
+working HTTPS endpoint and redirect HTTP to HTTPS. After that deployment is
+verified, change the session cookie to `secure: true`, update the transport
+tests, and remove the HTTP compatibility path. The TLS termination and
+redirect must be deployed and tested first; changing the cookie setting alone
+breaks authentication.
diff --git a/release-notes/fixed-plex-login-session.md b/release-notes/fixed-plex-login-session.md
new file mode 100644
index 00000000..0418f777
--- /dev/null
+++ b/release-notes/fixed-plex-login-session.md
@@ -0,0 +1,8 @@
+---
+category: fixed
+audience: users, operators
+area: authentication
+action: none
+breaking: false
+---
+Plex sign-in now completes on direct HTTP/LAN deployments again, while HTTPS deployments continue to receive Secure session cookies; failed session handoffs now show an error instead of spinning indefinitely.
diff --git a/server/index.ts b/server/index.ts
index 367b2599..4383b874 100644
--- a/server/index.ts
+++ b/server/index.ts
@@ -321,11 +321,7 @@ app
         secret: settings.sessionSecret,
         resave: false,
         saveUninitialized: false,
-        cookie: {
-          ...sessionTransportOptions.cookie,
-          // Keep the clear-text transport guard explicit at the session sink.
-          secure: true,
-        },
+        cookie: sessionTransportOptions.cookie,
         proxy: sessionTransportOptions.proxy,
         ...(sessionStore ? { store: sessionStore } : {}),
       })
diff --git a/server/utils/sessionCookie.test.ts b/server/utils/sessionCookie.test.ts
index 65b2616b..55d0d2bd 100644
--- a/server/utils/sessionCookie.test.ts
+++ b/server/utils/sessionCookie.test.ts
@@ -5,19 +5,14 @@ import { describe, it } from 'node:test';
 import request from 'supertest';
 import { getSessionTransportOptions } from './sessionCookie';
 
-const createApp = () => {
+const createApp = (development = false) => {
   const app = express();
   app.use(
     session({
       secret: '01234567890123456789012345678901',
       resave: false,
       saveUninitialized: false,
-      cookie: {
-        httpOnly: true,
-        sameSite: 'strict',
-        secure: true,
-      },
-      proxy: true,
+      ...getSessionTransportOptions(development, true),
     })
   );
   app.get('/', (req, res) => {
@@ -28,14 +23,17 @@ const createApp = () => {
 };
 
 describe('getSessionTransportOptions', () => {
-  it('requires secure session cookies in every runtime', () => {
-    assert.equal(getSessionTransportOptions(false, true).cookie.secure, true);
-    assert.equal(getSessionTransportOptions(false, false).cookie.secure, true);
+  it('uses automatic transport-aware security for session cookies', () => {
+    assert.equal(getSessionTransportOptions(false, true).cookie.secure, 'auto');
+    assert.equal(
+      getSessionTransportOptions(false, false).cookie.secure,
+      'auto'
+    );
     assert.equal(getSessionTransportOptions(false, true).proxy, true);
   });
 
   it('keeps the remaining cookie protections in development and production', () => {
-    assert.equal(getSessionTransportOptions(true, true).cookie.secure, true);
+    assert.equal(getSessionTransportOptions(true, true).cookie.secure, 'auto');
     assert.equal(
       getSessionTransportOptions(true, true).cookie.sameSite,
       'strict'
@@ -52,7 +50,13 @@ describe('getSessionTransportOptions', () => {
     assert.equal(getSessionTransportOptions(true, true).proxy, false);
   });
 
-  it('emits a secure production cookie from a TLS terminator without global proxy trust', async () => {
+  it('matches the cookie security to the forwarded request transport', async () => {
+    const directResponse = await request(createApp()).get('/');
+    assert.doesNotMatch(
+      directResponse.get('Set-Cookie')?.[0] ?? '',
+      /; Secure(?:;|$)/
+    );
+
     const response = await request(createApp())
       .get('/')
       .set('X-Forwarded-Proto', 'https');
diff --git a/server/utils/sessionCookie.ts b/server/utils/sessionCookie.ts
index f146b984..cb1df102 100644
--- a/server/utils/sessionCookie.ts
+++ b/server/utils/sessionCookie.ts
@@ -10,7 +10,9 @@ export const getSessionTransportOptions = (
     maxAge: SESSION_MAX_AGE_MS,
     httpOnly: true,
     sameSite: csrfProtection ? 'strict' : 'lax',
-    secure: true,
+    // Let express-session add Secure for HTTPS requests while preserving
+    // compatibility with direct HTTP/LAN deployments.
+    secure: 'auto',
   },
   // This option is scoped to express-session's transport check. It lets a
   // TLS terminator's X-Forwarded-Proto=https authorize a Secure cookie
diff --git a/src/components/Login/index.tsx b/src/components/Login/index.tsx
index cdc8dae9..6e477264 100644
--- a/src/components/Login/index.tsx
+++ b/src/components/Login/index.tsx
@@ -61,12 +61,29 @@ const Login = ({ initialBackdrops }: { initialBackdrops?: string[] }) => {
           { signal: controller.signal }
         );
 
-        if (active && response.data?.id) {
-          void revalidate();
+        if (active) {
+          if (!response.data?.id) {
+            throw new Error('Unable to complete Plex sign-in.');
+          }
+
+          const authenticatedUser = await revalidate();
+          if (!authenticatedUser) {
+            throw new Error(
+              'Plex sign-in succeeded, but Seerr could not establish a browser session. Check that you are using the HTTPS URL or that direct HTTP session cookies are enabled.'
+            );
+          }
         }
       } catch (e) {
         if (active && !axios.isCancel(e)) {
-          setError(axios.isAxiosError(e) ? e.response?.data?.message : '');
+          const message = axios.isAxiosError(e)
+            ? e.response?.data?.message
+            : e instanceof Error
+              ? e.message
+              : undefined;
+          setError(message || 'Unable to complete Plex sign-in.');
+        }
+      } finally {
+        if (active) {
           setAuthToken(undefined);
           setProcessing(false);
         }