Every attack so far used today's weapons. Yours is from the future: a computer that breaks the maths itself. This is the one page where we can't show you the attack failing.
A qubit is a quantum computer's working part; “noisy” ones make errors, and today's machines are mostly noise.
Aim the weapon — what does quantum actually do to each part of Bitcoin?
The race: the weapon vs the shield
This isn't Bitcoin's private problem. The same maths guards every bank, government and military secret on Earth. When the migration comes, Bitcoin migrates alongside the whole internet — with an upgrade process that has a proven record the internet's doesn't.
What if it arrives early?
Told straight: a sudden breakthrough would mean a messy, rushed migration, and old exposed coins could genuinely be stolen. It would be Bitcoin's hardest test, and nobody serious claims otherwise. But what survives even that scenario is the previous six pages' point — the record book, the nodes, the cap and the rules aren't what quantum threatens. The locks are. And locks can be changed.