Zcash just made shielded notes unstealable by quantum computers. Mainnet rollout this month. Today, spending a shielded note requires one thing: a valid signature from your private key, which lives on an elliptic curve. Quantum computers can extract that key. Quantum arrives, your note is gone. The new note version requires two things at once to spend. First, the same elliptic-curve signature. Second, a value derived from a hash chain rooted in your seed phrase. Quantum breaks the elliptic curve. Quantum does not break hashes. The attacker can fake the first half. They cannot fake the second. The legitimate owner has the seed. They derive both halves. They spend. When quantum arrives, you sweep your shielded ZEC through the post-quantum path to a fully post-quantum address. Funds preserved. What this does not solve: privacy of past transactions. zk-SNARKs themselves still rely on elliptic curves, so a future quantum attacker could decrypt the contents of historical shielded transactions. Full privacy migration is targeted for 2027. ZEC holders just need to shield. The protocol does the rest.