The estimated cost of constructing a quantum-resistant Bitcoin transaction dropped from about $320 to roughly $67 in seven days, after a wave of AI-assisted solvers competed in an optimization challenge run by StarkWare, Yukon Research and Eigen Labs.

The figure comes from the live dashboard of the Quantum-Safe Bitcoin Optimization Challenge, an open contest that asked outside developers to push the number down. StarkWare disclosed the latest result this week.

What is the reference transaction?

The first quantum-safe Bitcoin transaction was mined on mainnet last month, a construction StarkWare built to protect coins without requiring a network-wide protocol fork. That initial transaction cost around $320 and consumed roughly 3,100 GPU-hours. One week of public competition cut most of that compute cost out.

How does the cost drop so quickly?

The expensive step is a brute-force search that runs on a user's own hardware before anything reaches the chain. That is why the savings show up as a GPU bill rather than a Bitcoin fee.

The construction inserts a hash where Bitcoin expects a signature, and only about one in 70 trillion hash outputs fits the required shape. Faster code therefore means fewer GPU-hours per successful build.

Solvers pushed a core benchmark from 146 million verified candidates per second to over 820 million on a standard RTX 4090. The challenge promoted 62 improvements across two tracks in seven days.

• Cost reduction: roughly 79%, $320 to $67
• Benchmark: 146M to 820M verified candidates per second on RTX 4090
• Promotions: 62 improvements across two tracks

Which solvers led the field?

Developers running large AI models swept the leaderboard. StarkWare named Anthropic's Opus 5 and Fable 5.1 at the top, with OpenAI's GPT-6 Astra, Grok 4.6 and Kimi close behind.

The contest did not specify whether the AI tools wrote entire patches or assisted human engineers directly. StarkWare co-organized the challenge with Yukon Research and Eigen Labs.

Does the $67 figure make Bitcoin quantum-safe?

No. StarkWare stressed that the $67 number is an estimate under stated hardware assumptions, not a market price, and it shifts every time a solver beats the record. Two structural limits apply:

• The transactions are nonstandard and must be sent directly to a miner
• The construction only shields coins whose public key has not already appeared on-chain

StarkWare maintained that the contest does not, on its own, secure the Bitcoin network and that a soft fork remains the cleaner long-term path.

What changes before Q-Day?

The savings matter because institutions already map out a quantum contingency. Coinbase is drafting post-quantum custody playbooks for the hypothetical moment when quantum computers can break the elliptic-curve cryptography securing today's wallets, an event researchers call "Q-Day."

A soft fork remains the structurally cleaner protocol path, but the leaderboard suggests off-chain optimization still has room to compress the GPU bill for users who want protection before consensus catches up.