StarkWare researcher Avihu Levy conducted an experimental quantum‑resistant Bitcoin transaction on the mainnet, which was confirmed in block 964,199 on Wednesday, according to StarkWare. The transaction spent a 10,000‑satoshi output protected by the Quantum Safe Bitcoin (QSB) scheme, as described in Levy’s paper and code repository. QSB combines hash‑based one‑time signatures with computational searches that bind an authorization to a specific transaction, a design intended to prevent forgery if elliptic‑curve cryptography is broken by a quantum computer. The test moves Levy’s April proposal from theory to an on‑chain demonstration, showing that Bitcoin’s consensus rules can accommodate this form of quantum‑resistant spending without a protocol change. StarkWare estimated the transaction cost at $150 to $200 and said the computation took several hours. The QSB transaction is classified as nonstandard under Bitcoin Core’s default relay policies, meaning ordinary nodes would not propagate it before confirmation and it must be submitted directly through MARA’s Slipstream service. StarkWare spokesperson Nathan Jeffay said the completed transaction cost “low hundreds of dollars,” reiterating the $150‑$200 estimate. CEO Eli Ben‑Sasson stated that a soft fork should be considered for broader adoption and that QSB provides a safety net while protocol‑level protections are developed. Bitcoin developers are separately reviewing BIP‑360, a proposal to introduce a Pay‑to‑Merkle‑Root output type and remove quantum‑vulnerable key‑path spends.