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Ethan Mollick asked Opus 4.6 (in Claude Code) to build Borges’s Library of Babel…

2026-06-16 · 18:24 UTC ·@emollick ·0 min read

Brief

Ethan Mollick posted that he prompted Opus 4.6 (Claude Code) to generate Borges’s Library of Babel; within roughly an hour it produced a searchable web implementation that encodes books using a Feistel cipher so every possible book has a real location. He links the live demo (library-of-babel-3d.netlify) and credits Dan Shipper for an independent version.

Why it matters

Ethan Mollick asked Opus 4.6 (in Claude Code) to build Borges’s Library of Babel and the model produced a working implementation within about one hour (posted 2026-06-16).

Key details

  • The AI used a Feistel cipher so every possible book maps to a unique, retrievable location and the site supports searching text across the entire Library (link: library-of-babel-3d.netlify).
  • Mollick notes this repeats earlier work with Claude 4.6 and that developer Dan Shipper independently created a similar version posted on the same thread.
Source evidence

Previously done with Claude 4.6: nitter.net/emollick/status/201966…

@danshipper also did a version (which I did not know until he posted on this thread).

Ethan Mollick (@emollick)

I asked Opus 4.6 in Claude Code to build me Borges's Library of Babel. An hour later it delivered this.

The AI implemented a Feistel cipher so each possible book has a real location, you can search for text across the Library & find the book.

Enter it: library-of-babel-3d.netlify.…

Video

— https://nitter.net/emollick/status/2019668008680182063#m