Ethan Mollick Shares an Experiment Building an Endless Journey Through 3D Worlds

What happened

Ethan Mollick describes asking Fable 5.2 to build an endless, hands-off journey through 3D worlds linked by portals. He says 25,000 agents created over 450 worlds inspired by books, art, and places, all in code. He links to a playable version and GitHub.

Read next

• More changes in today’s briefingGoogle DeepMind Introduces Gemini 4 Hydrogen for Fast Agentic Workflows

2 reports

The story so far

Anthropic released Claude Fable 5.2 and Claude Mythos 5.2, lowering API prices to $8 per million input tokens and $40 per million output tokens, from $10 and $50. Anthropic says both models improve coding, reasoning, and vision, and that Fable produces responses faster than version 5.1. Fable is available to paid users with safeguards for risky cybersecurity and biology tasks; Mythos is limited to organizations approved through Anthropic’s verification programs. The launch reports cite strong benchmark results, including Fable’s first-place score on Artificial Analysis’ Intelligence Index v5 at its highest compute tier. Those figures come from the named benchmark evaluations; Anthropic’s prerelease examples also include software migrations, electronic devices, and physics problems. TechCrunch reports that an optional faster serving mode costs twice as much, while the lower API prices apply to standard use.