Developer T4T5 has used Anthropic's Claude Opus 5.5 to recreate an early Windows program for Bitcoin, released by Satoshi Nakamoto in 2009. The rebuilt bitcoin.exe has the same SHA-256 hash as a preserved original and matches it byte for byte. The result offers new evidence about how Bitcoin's early software was built, but the version running on the network's launch day has yet to be found.
Rebuilt executable matches the preserved original
T4T5 recreated the computing environment used at the time and built the program with Claude Opus 5.5. The developer's results show that the generated bitcoin.exe shares the original file's SHA-256 hash, with every byte matching.
That level of reproducibility is not guaranteed simply by having the source code. Bitcoin's earliest software was not designed for reproducible builds: differences in compilers, software libraries and even line endings can change the resulting file. Producing an identical executable therefore requires reconstructing the environment and specific settings used to build it.
Bitcoin's launch-day software is still unconfirmed
The reconstruction concerns the original Bitcoin software released by Nakamoto in 2009. While the file match provides evidence about the early build process, it does not settle every question about which version was used when Bitcoin launched. The software from that day remains missing.
Reproducing a preserved release and locating the launch-day version are separate matters. What has been established is that T4T5's rebuilt program is identical to one surviving original file. The available evidence does not show that this was the version running on Bitcoin's launch day. Reconstructing the build environment advances analysis of the early software, but the missing launch-day file still limits efforts to verify the network's initial release in full.