two year old labrador pulls like a sled dog through three different harnesses and two head halters and i am ready to admit we are the problem, what actually changed leash walking for owners of high drive labs and retrievers who have been through this and come out the other side

Hopper is two years old, 72 pounds, neutered male labrador from a working line breeder. We have had him since 9 weeks and we did all of the puppy class work, AKC star puppy stuff, basic obedience class, the works. He is great at sit, down, place, recall in the yard, and he is genuinely a delight in the house and at the dog park. The single thing we have not solved in two years of trying is loose leash walking. Every walk turns into him pulling toward the next thing he wants to sniff or see, with his weight thrown against whatever piece of equipment we have on him, and us either being dragged down the sidewalk or stopping every six feet to do another reset that does not stick past the next interesting smell.

Equipment we have tried, in roughly the order we tried it. Standard flat collar with a six foot leash, which he ignored entirely. Front clip harness from a well reviewed brand, which slowed him down for about a week and then he learned to lean into it and pull anyway. Head halter, which he hated and rubbed his face raw against trying to get off, and which we could not get him acclimated to despite following the published protocol for it. Second front clip harness with a different fit because we thought maybe the first one was the problem, same result as the first. Prong collar that we used briefly under the supervision of a balanced trainer, which did stop the pulling instantly but felt wrong to both of us as a long term tool and we returned to positive methods after two sessions. We are currently back on a front clip harness and a six foot leash and the pulling is back to where it was when we started.

What i suspect is going on, with the caveat that i am clearly missing something. The published advice for loose leash walking generally falls into a few categories: reward heavily for any moment the dog is in position, change direction when the dog gets ahead, stop walking entirely until the dog comes back to position, use the right equipment to make pulling uncomfortable. We have done all of these, sometimes with religious consistency for weeks at a time, and Hopper learns the game in the backyard and on quiet streets but the second we are in any environment with real stimuli his brain leaves his body and we are sled dogging again. I do not think he is being defiant, i think the arousal level in interesting environments completely overwhelms whatever the training has built. I just do not know what to do about it.

What i am hoping for from this thread. Owners of high drive labs, goldens, vizslas, or similar who have actually solved this problem over time, what was the thing that moved the needle. Trainers who work this case pattern, what is the framing that owners like us usually miss. I am willing to put in significant time and i am willing to spend money on a private trainer if the right one is the answer, but i want to come into the next attempt with a clearer model of what we are trying to do than the equipment swapping we have been doing for two years. Specific protocols, specific books, specific approaches that helped. Hopper deserves walks that are not a fight for both of us