Bitcoin confirmed its first mainnet transaction using the Quantum‑Safe Bitcoin (QSB) method on Aug. 26, according to StarkWare researcher Avihu Levy. The transaction did not change Bitcoin’s consensus rules. QSB replaces elliptic‑curve signatures with hash‑based commitments to protect against attacks by quantum computers that could run Shor’s algorithm. Generating each QSB spend requires about 2^46 hash attempts, estimated at $75‑$150 in off‑chain GPU computation. The process bypasses the public mempool and must be submitted directly to a participating miner. The method protects legacy outputs but does not secure Taproot, Lightning channels, or previously exposed keys. Coins must be moved to a QSB output before a quantum attack becomes feasible. StarkWare CEO Eli Ben‑Sasson said the successful transaction offers reassurance that holdings can be protected before a quantum threat materializes, pending a possible soft fork. Developers plan independent review of the QSB code, further mainnet testing, and work on more scalable post‑quantum signature systems. The demonstration serves as a fallback while a full network‑level migration remains under study.