iOS: adopt UIScene lifecycle (Xcode deprecation warning)

[hessius]

Problem

Xcode warns on the iOS/Capacitor build:

UIScene lifecycle will soon be required. Failure to adopt will result in an assert in the future.

(Reported in 2.6.0 beta testing.)

Findings (researched 2026-07-05)

• Capacitor 8.4.1 has no built-in UIScene/SceneDelegate support. The bridge (CAPBridgeViewController / ApplicationDelegateProxy) is wired to the classic AppDelegate window lifecycle. There is no official SceneDelegate template, migration guide, or UIApplicationSceneManifest.
• Not currently breaking. It is a log warning only. Apple's assert fires only when building against the iOS 27 SDK (~Sep 2026). Shipping against the iOS 26 SDK today is safe.
• Official fix is imminent. Ionic is fast-tracking UIScene support for Capacitor 8.5 (out-of-band breaking minor; work started the sprint of 2026-06-22). Tracking issue: CLIENT OF UIKIT REQUIRES UPDATE: This process does not adopt UIScene lifecycle. This will become an assert in a future version. ionic-team/capacitor#7961.

Recommendation

Prefer the official Capacitor 8.5 (or 9) upgrade over the unofficial workaround, because:

• The community workaround (add SceneDelegate.swift + UIApplicationSceneManifest, trim AppDelegate) is superseded/reconciled by the Capacitor upgrade anyway.
• Our AppDelegate routes deep links / Universal Links via ApplicationDelegateProxy (open url, continue userActivity). Under a SceneDelegate these AppDelegate callbacks are bypassed, so the proxy calls must be re-implemented in the scene delegate (scene(:openURLContexts:), scene(:continue:)) or deep-link/discovery handling silently breaks. This needs on-device verification.

Action items

• Watch CLIENT OF UIKIT REQUIRES UPDATE: This process does not adopt UIScene lifecycle. This will become an assert in a future version. ionic-team/capacitor#7961 / bump to Capacitor 8.5 when released.
• After the bump, verify the webview loads and that Universal Links / custom URL schemes / MeticulousDiscoveryPlugin still work on device.
• Only if the deadline approaches before 8.5 ships: apply the community SceneDelegate workaround with the ApplicationDelegateProxy scene routing, and regression-test deep links on device.

References

• CLIENT OF UIKIT REQUIRES UPDATE: This process does not adopt UIScene lifecycle. This will become an assert in a future version. ionic-team/capacitor#7961 (tracking) — CLIENT OF UIKIT REQUIRES UPDATE: This process does not adopt UIScene lifecycle. This will become an assert in a future version. ionic-team/capacitor#7961
• Community workaround — CLIENT OF UIKIT REQUIRES UPDATE: This process does not adopt UIScene lifecycle. This will become an assert in a future version. ionic-team/capacitor#7961 (comment)
• Apple TN3187 — https://developer.apple.com/documentation/technotes/tn3187-migrating-to-the-uikit-scene-based-life-cycle