| Claude Fable 5 | Claude Opus 4.8 | |
|---|---|---|
| arenaElo | 1492 | 1435 |
| humanEval | 98 | 94.5 |
| sweBench | 77 | 67 |
| mmlu | 95.1 | 93 |
| gpqa | 92 | 67.5 |
| aime | 94 | 90 |
| Price in/out ($/M) | $10 / $50 | $5 / $25 |
Fable 5 is the most capable model Anthropic ships (stronger long-horizon autonomous agents and frontier reasoning), but it costs $10 / $50 per M tokens, uses a new tokenizer that counts ~30% more tokens, has thinking always on, and requires 30-day data retention. Opus 4.8 stays the pragmatic default at $5 / $25 with the familiar request surface. Reach for Fable 5 on your hardest agentic and research work; keep Opus 4.8 for the high-volume bulk of production traffic.