What to Pack in Your Day Pack for a Multi-Day Hike

That should be sufficient.

I’d consider a similar principle to whenever I check my main bag in for a flight. Travel documents, means of payment; phone and charger and a toothbrush always stay with me.

If you have any prescription medications or other valuables, you should carry them with you. It's not common for bags to go missing but you don't want to find yourself without anything essential.

Home last night from the GR 65, used luggage transport for the larger pack and used a Gossamer Gear Loris 25 for the daypack. It had my wallet/passport/credential/cell phone, small dry bag with charger, air pods, second small dry bag in the outside pocket with first aid supplies, water bladder, smart water bottle on outside as extra water source and after hike drinking, extra tshirt/undies/socks in case large bag got lost, guide book, insulating layer/rain jacket, depending on weather, lunch/snacks. First time using this pack, with mixed feelings. Ultra light, fit me well, good design. On cooler days, it was wonderful as it blocked the wind well and the foam sit pad that gives the pack structure was used often on days when there were no places to sit for breaks. But on the hot days, it was pretty brutal with no air flow. If I can figure out a way to get the pack even a smidge off my back instead of having the sit pad rest directly on it, it would be my perfect day pack.