Introducing Claude Fable 5.1 — Transcript

Today we're releasing Fable 5.1, the latest upgrade to our most capable model class. Whatever you already hand Claude, it can take on more and do the hardest parts better. That's possible because of how it handles multi-step work like a complex financial model, a long mathematical proof, or a contract with hundreds of cross-references. These are the kinds of tasks where a small mistake in step 2 messes things up in step 40, and Fable 5.1 holds up the whole way. Give it a software project, and it can take on more of it than ever.

From code review to performance work, features that cut across an entire codebase. Sessions you can step away from and come back to. If it hits a wall, it tells you what it tried and where it got stuck. And it doesn't stop at code. Give Fable 5.1 an open question, and it comes back with something polished, ready for you to review. The research, the spreadsheet, the memo, the deck, all with the numbers and sources laid out so that you can check them. And this model is great at science. Give it a hard problem, and it works with you by reading the literature, proposing a hypothesis, and designing an experiment so that your research happens faster.

Fable 5.1 is out today, available everywhere. Hand it something big and see what it brings back. We think it's the best model we've made for complex work, and it's ready for yours.