On August 26, the Bitcoin mainnet successfully processed its first quantum-resistant transaction. Avihu Levy from StarkWare used the QSB scheme to spend about 10,000 satoshis, and this transaction was included in block 964199. The method involved repeatedly tweaking the transaction off-chain using a GPU until the hash coincidentally resembled a valid signature. No changes were made to the consensus rules, and regular nodes can still verify it using the old method. This scheme can defend against Shor's algorithm with approximately 118-bit security, but against Grover's algorithm, it drops to about 59-bit. The issue is that regular nodes won’t relay this kind of transaction, so it has to be sent directly to MARA. The computational power required costs around $150 to $200, and it takes a few hours. Levy himself said this is just a last resort. Plus, it only protects coins that have already migrated into the scheme. The migration step is still a regular transaction, and once the public key is exposed, it could be vulnerable to theft. There are about 7 million Bitcoin on-chain with public keys already exposed, and these coins have no escape route. Even the CEO mentioned that this shouldn’t be interpreted as Bitcoin being fully prepared. In the long term, a soft fork is still necessary.