fix: prevent SAML re-fire infinite loop during short-lived-token redeem

[fabioh8010]

Explanation of Change

Fixes a SAML web sign-in loop where an SSO (SAML-required) user bounces between their identity provider and the app and the session never sticks.

On the /transition redirect-back, LogInWithShortLivedAuthTokenPage starts the short-lived token exchange (SignInWithShortLivedAuthToken, which optimistically sets account.isLoading) and navigates to HOME while still unauthenticated. SignInPage then remounts with hasInitiatedSAMLLogin reset (it's component-local useState); because account.isLoading is still true and SAML is required, it re-initiates SAML — a full-page window.location.replace to the IdP that tears the page down before the token exchange can finish. The token is never consumed, a fresh one is minted on the way back, and it loops. The root problem is that account.isLoading is set for two different reasons (about to start SAML vs. a short-lived token exchange already in flight) and SignInPage could not tell them apart.

This gates shouldInitiateSAMLLogin on the existing RAM_ONLY_IS_AUTHENTICATING_WITH_SHORT_LIVED_TOKEN flag, which is set only while a short-lived token exchange is in flight (in getShortLivedLoginParams) but was previously never read. SignInPage no longer re-initiates SAML during the exchange, so the exchange completes and the session sticks. Because the flag is set for the exact duration of the exchange, the fix is independent of the account.isLoading timing race and holds regardless of IdP/device/network speed. The legitimate first SAML initiation (no exchange in flight) is unchanged.

Fixed Issues

$ #95810
PROPOSAL:

Tests

Prerequisites

First, edit src/libs/actions/Session/index.ts to reproduce the SAML-loop bug conditions:

diff --git a/src/libs/actions/Session/index.ts b/src/libs/actions/Session/index.ts
index f909e17b8c5..6580ce394fd 100644
--- a/src/libs/actions/Session/index.ts
+++ b/src/libs/actions/Session/index.ts
@@ -845,9 +845,15 @@ function beginGoogleSignIn(token: string | null, preferredLocale: Locale | undef
 function signInWithShortLivedAuthToken(authToken: string, isSAML = false) {
     const {optimisticData, failureData, finallyData} = getShortLivedLoginParams(false, isSAML);
     const authMethod = isSAML ? CONST.AUTH_METHOD.SAML : CONST.AUTH_METHOD.SHORT_LIVED_AUTH_TOKEN;
-    Device.getDeviceInfoWithID().then((deviceInfo) => {
-        API.read(READ_COMMANDS.SIGN_IN_WITH_SHORT_LIVED_AUTH_TOKEN, {authToken, skipReauthentication: true, authMethod,     deviceInfo}, {optimisticData, failureData, finallyData});
-    });
+    // [SAML-REPRO] Force the sustained loop: apply the optimistic isLoading:true NOW, but delay the actual redeem so the
+    // re-fire tears the page down before auth can persist (mirrors prod, where the redeem is aborted every iteration).
+    // REMOVE before shipping.
+    Onyx.update(optimisticData);
+    setTimeout(() => {
+        Device.getDeviceInfoWithID().then((deviceInfo) => {
+            API.read(READ_COMMANDS.SIGN_IN_WITH_SHORT_LIVED_AUTH_TOKEN, {authToken, skipReauthentication: trueauthMethod,       deviceInfo}, {optimisticData, failureData, finallyData});
+        });
+    }, 3000);
     NetworkStore.setLastShortAuthToken(authToken);
 }
 

Now, you need to setup a local PROD web server so you are able to perform the entire SAML flow:

1. Reissue the dev cert to also cover new.expensify.com
   1. Same as npm run setup-https, plus one host, written to the cert path. The mkcert CA is already installed, so the new cert is trusted automatically, and dev.new.expensify.com keeps working.

      mkcert -cert-file config/rsbuild/certificate.pem -key-file config/rsbuild/key.pem new.expensify.com dev.new.expensify.com localhost 127.0.0.1

2. Point the prod host at localhost
   1. Leave www.expensify.com alone — it must keep resolving to real prod Auth.

      echo "127.0.0.1 new.expensify.com" | sudo tee -a /etc/hosts

3. Build against prod
   1. .env.production is already correct out of the box — EXPENSIFY_URL=https://www.expensify.com/, NEW_EXPENSIFY_URL=https://new.expensify.com/, and USE_WEB_PROXY=false (talks straight to prod). No edits needed. npm run build sets ENV=production → reads .env.production → outputs to dist/ (requires bun).

      npm run build

4. Serve dist as https://new.expensify.com (SPA-aware, on :443)
   1. Two terminals:

      # terminal A — static server with SPA fallback (so /transition serves index.html)
      npx serve -s dist -l 8082
      
      # terminal B — TLS on 443 → 8082 using the mkcert pair (443 needs sudo)
      sudo npx local-ssl-proxy --source 443 --target 8082 --cert config/rsbuild/certificate.pem --key config/rsbuild/key.pem

To clean up the PROD setup, run these:

sudo sed -i '' '/127\.0\.0\.1  new\.expensify\.com/d' /etc/hosts
npm run setup-https                 # restore the original dev cert

Test steps

1. Login with a normal account, assert it works.
2. Refresh the web/app, assert you are still logged in.
3. Sign out, assert it works.
4. Login with a SAML domain account, assert the SAML flow is executed just ONE time.
5. Refresh the web/app, assert you are still logged in.
6. Sign out, assert it works.

• Verify that no errors appear in the JS console

Offline tests

N/A

QA Steps

It's only possible to test on PROD environment.

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
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Screenshots/Videos

Android: Native

Screen.Recording.2026-07-15.at.12.18.21.mov

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

Screen.Recording.2026-07-15.at.11.03.00.mov

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Set the token guard before awaiting device info

When a SAML /transition callback is handled, LogInWithShortLivedAuthTokenPage calls signInWithShortLivedAuthToken and immediately schedules Navigation.navigate(ROUTES.HOME) for SAML callbacks, but signInWithShortLivedAuthToken does not apply getShortLivedLoginParams (including RAM_ONLY_IS_AUTHENTICATING_WITH_SHORT_LIVED_TOKEN) until Device.getDeviceInfoWithID() resolves. If navigation wins that race on a slower device/browser, this predicate still sees isAuthenticatingWithShortLivedToken === false while the old SAML-required/loading account state is present, so the page can re-fire SAML before the guard is ever set and the loop remains. Set the RAM-only guard synchronously before leaving /transition or before awaiting device info.

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