iOS 26+ introduces a Deferred Start API for AVCaptureSession that postpones initialization of non-preview outputs (like photo and movie outputs) until after the first preview frame renders, dramatically cutting camera app launch times.
• Reduces camera app launch time by up to 2x — only the preview output initializes before first frame, all other outputs initialize in the background
• Responsive Capture (isResponsiveCaptureEnabled) pairs with deferred start so users can still take photos immediately even before the photo output fully initializes
• Automatic and manual modes give developers flexibility: automatic triggers deferred init right after preview appears, manual lets you choose the exact moment