Crypto News

AI Helped Rebuild Satoshi's Original Bitcoin Program, Byte for Byte

Seventeen years after Bitcoin launched, nobody had managed to rebuild Satoshi's first Windows program and get the exact same file. A developer says AI helped them do it. Here is the story in plain words.

Quick answer: A developer known as t4t5 rebuilt the first Bitcoin program for Windows that Satoshi Nakamoto released in January 2009, and their copy is identical to the original, down to the last byte. News reports say they used Anthropic's AI model Claude Opus 5.5 to work out exactly how Satoshi's computer was set up. The result shows the original program was made only from the code Satoshi published, with nothing hidden inside.

Key takeaways

AI did the detective work. Reports say the developer used Claude Opus 5.5 to work out Satoshi's 2009 computer setup.
The copy is identical. Its digital fingerprint, the SHA-256 hash, matches the original file exactly.
Nothing was hidden. Every part of the original program can be explained by Satoshi's public code.
One mystery remains. The file everyone has is the 10 January 2009 update. The very first version, from 8 January, has never been found.

Satoshi Nakamoto shared Bitcoin's code with the world in January 2009, then disappeared. But sharing code is not the same as proving that the program people downloaded was built from it. For 17 years, nobody could rebuild that first program and get the exact same file. Now a developer says AI helped them do it.

What happened?

A developer who goes by t4t5 published a project on GitHub that rebuilds bitcoin.exe, the first Bitcoin program for Windows, from Satoshi's original code. The rebuilt file is exactly the same as the one Satoshi shared in 2009.

According to BeInCrypto, republished by Yahoo Tech on 22 October 2026, they used Claude Opus 5.5, an AI model made by Anthropic, to figure out which computer, software and settings Satoshi used. The GitHub project itself explains the technical steps but does not mention the AI.

Why was it so hard?

A program is not just code. It also depends on the computer, the tools and the settings used to build it. Change any of them slightly and the final file comes out different, even from the same code.

So to get an identical copy, the developer had to recreate Satoshi's setup from 2008 and 2009 almost perfectly, using old software from that time, right down to tiny details such as how the lines of one settings file ended.

How do we know the copy is identical?

Every file has a digital fingerprint called a SHA-256 hash. If even one byte changes, the fingerprint changes completely. The rebuilt bitcoin.exe has the same fingerprint as the original, and the same size of 6,440,960 bytes, so the two files are identical.

What did it reveal about Satoshi?

The rebuild gives a rare look at how Bitcoin was first made. According to the project:

Satoshi worked on Windows XP, using a free programming toolkit called MinGW.
The program was built in debug mode, a setting developers normally use while testing, with the extra information stripped out afterwards.
Satoshi changed their tools part way through. Some parts were built in late November 2008 and Bitcoin itself on 10 January 2009.

What is still a mystery?

Bitcoin was announced on 8 January 2009. But the file everyone has today is actually the update from two days later, 10 January. No confirmed copy of the very first launch-day program is known to exist.

The rebuild also has small limits, which the developer lists openly: a few timestamps had to be entered by hand, two helper files were copied from the original rather than rebuilt, and the build ran on a simulator rather than a real Windows XP computer.

Why does this matter?

It proves the original Bitcoin program contains nothing except the code Satoshi made public. For a system built on the idea that anyone can check it, that is reassuring. It also shows how AI can now help with detailed detective work that people had not managed for years.

Bitcoin's motto is simple: do not trust, verify. The same goes for your own money. The Fizen wallet is self-custody, so you hold the keys to your own balance.

Frequently asked questions

Did AI really help rebuild Satoshi's Bitcoin program?

News reports say the developer used Claude Opus 5.5 to work out Satoshi's computer setup. The GitHub project shows the result but does not name the AI.

What does byte for byte mean?

That the rebuilt file is exactly the same as the original, with not a single difference. Its SHA-256 fingerprint matches.

Is this the very first Bitcoin version?

No. It is the 10 January 2009 update. The 8 January launch version has never been found.

Does this reveal who Satoshi is?

No. It shows how the program was built, not who built it.

Why does it matter?

It proves the original program contains only Satoshi's public code, with nothing hidden inside.

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Terms and conditions

Information only. This article reports on a public software project and press coverage of it. It is not financial, legal, tax or investment advice, and not an offer or sale of any product.
For readers in the United States. This is information only, not an offer or sale, and not advice. Fizen products and services are not offered to US Persons.
Independent. Fizen is not affiliated with t4t5, Anthropic, BeInCrypto or the Satoshi Nakamoto Institute. Technical details are as published in the GitHub repository on 23 October 2026.

Sources

Facts checked against the GitHub repository and press coverage on 23 October 2026.