The blog.
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GPT-6 Astra vs Fable 5.1: What Actually Matters
OpenAI's GPT-6 Astra matches or beats Anthropic's Fable 5.1 on most benchmarks at a lower price. Here's what actually matters for people who build with these models.
Fable 5.1 Watermarks: How AI Text Watermarking Actually Works
Fable 5.1 is the first Anthropic model to watermark everything it writes. Here's how the watermark actually works and the only real way to get around it.
Fable 5.1: Better Benchmarks, 25% Lower Cost
Fable 5.1 beats Fable 5, Opus 5, and GPT 5.6 Soul across the board while costing an estimated 25% less — up to 45% less on long-running agentic work. Here's everything that actually changed.
