8 to 26 weeks. Always follow your vet's advice about when your puppy can go out and meet the world.
What is your puppy doing right now?
Pick one to see what it might mean.
Rule of thumb: awake stretch about 45 minutes at 8 weeks, growing by roughly 5 minutes a week. Naps of 60–120 minutes. A guide only, not a vet's schedule.