The estimated cost of building a quantum-safe Bitcoin transaction has fallen from about $320 to roughly $67 in a single week—a drop of nearly 80%—after developers and AI models competed to optimize the code behind the construction, according to StarkWare.

The figure comes from the dashboard of the Quantum-Safe Bitcoin Optimization Challenge, an open contest run by StarkWare alongside Yukon Research and Eigen Labs to see how far outside solvers could push the number down.

The competition builds on a milestone from last month, when the first quantum-safe Bitcoin transaction was mined on mainnet. The construction, developed by StarkWare, is designed to protect coins without requiring a network-wide fork. That initial transaction took roughly 3,100 GPU-hours and cost around $320 to build. One week of open competition cut most of that away. The lower that figure falls, the closer the approach moves from a one-off research demonstration toward something individual holders could realistically run on their own machines.

The savings come from raw speed. The expensive part of the process is a brute-force search that runs on a user's own hardware before anything reaches the blockchain, which is why it shows up as a GPU rather than a Bitcoin fee. The construction slots a hash where Bitcoin expects a signature, and because only about one in 70 trillion hash outputs takes the required shape, finding a valid one means hashing inputs over and over until one fits. Faster code therefore translates directly into fewer GPU-hours for the same result. The hash-centric design is also what gives the construction its quantum resistance: the elliptic-curve signatures Bitcoin normally uses are the component that quantum computers are expected to break, while hash functions are considered resistant to known quantum attacks.

Solvers made dramatic progress during the contest. One core benchmark jumped from 146 million verified candidates per second to over 820 million on a standard RTX 4090, with 62 improvements promoted across two tracks.

Notably, the leading records were held by developers running AI models, with StarkWare citing Anthropic's Opus 5 and Fable 5.1 at the top and OpenAI's GPT-6 Astra, Grok 4.6, and Kimi close behind—a striking datapoint for how quickly AI-assisted coding is reaching performance-critical systems work.

StarkWare was careful to temper expectations. The $67 figure is an estimate under stated hardware assumptions, not a market price, and it shifts each time a solver beats the record. The company also stressed that the effort does not make Bitcoin quantum-safe on its own: the transactions are nonstandard and must be sent directly to a miner, and the construction only shields coins whose public key has not already been exposed. That distinction matters because a Bitcoin address typically conceals its public key until the first time funds are spent from it; once a key is visible on-chain, it becomes the input a quantum attacker would target. StarkWare maintains that a soft fork remains the better long-term fix.

The work lands amid intensifying focus on Bitcoin's exposure to "Q-Day," the hypothetical point at which quantum computers could break the elliptic-curve cryptography securing wallets. Firms including Coinbase are already drafting post-quantum custody playbooks.