Merge pull request #20165 from mozilla/FXA-12760-v2

fix(fxa_status): Allow status.capabilities to be undefined

Author: LZoog

packages/fxa-settings/src/lib/hooks/useFxAStatus/index.tsx

@@ -57,30 +57,35 @@ export function useFxAStatus(integration: FxAStatusIntegration) {
           isPairing: false,
           service: Constants.SYNC_SERVICE,
         });
-        if (!webChannelEngines && status.capabilities.engines) {
+
+        // Very old versions of Firefox iOS do not send `capabilities` in the
+        // fxa_status response. This suppresses TypeErrors due to this.
+        const capabilities = status.capabilities || {};
+
+        if (!webChannelEngines && capabilities.engines) {
           // choose_what_to_sync may be disabled for mobile sync, see:
           // https://github.com/mozilla/application-services/issues/1761
           // Desktop OAuth Sync will always provide this capability too
           // for consistency.
           if (
             isSyncDesktopV3 ||
-            (isSyncOAuth && status.capabilities.choose_what_to_sync)
+            (isSyncOAuth && capabilities.choose_what_to_sync)
           ) {
-            setWebChannelEngines(status.capabilities.engines);
+            setWebChannelEngines(capabilities.engines);
           }
         }
         // Check if third party auth (passwordless) log in to the browser is supported,
         // currently only Firefox desktop 147+ as of Q1 2026
         if (
-          status.capabilities.keys_optional &&
+          capabilities.keys_optional &&
           isOAuthNative &&
           integration.isFirefoxNonSync()
         ) {
           setSupportsKeysOptionalLogin(true);
         } else {
           setSupportsKeysOptionalLogin(false);
         }
-        if (status.capabilities.can_link_account_uid) {
+        if (capabilities.can_link_account_uid) {
           setSupportsCanLinkAccountUid(true);
         } else {
           setSupportsCanLinkAccountUid(false);