In your parallel_prefilter function, you still return immediately when the first chunk finds a solution
This means you lose the operations done by the other threads.
I'm not sure he does now, there's a shared variable incrementing. But the kicker is there :
# Compute t2 for SHA256 prefilter if pubkey provided
Too bad we dont have public key in puzzle 69.
You're literally giving part of the solution of the search to your method

That was fun, but your code is obviously AI generated, and I'm not an LLM code fixer. So you're officially disqualified from the bounty.
That being said, with 99.5% improvement, I'm sur McD and WP will be thrilled to merge this method with the prefix one for even more gains. If they don't I might have to ask them to prove why it's not good
