AI Model Comparison
Side-by-side comparison of pricing, context window, benchmarks, capabilities, and license. Every figure comes from the developer's own pages, last checked on ; each model's page lists its sources. A figure we could not source shows as a dash.
Model A — Anthropic
Claude Fable 5.1 is Anthropic's model for demanding reasoning and long-horizon agentic work, released on September 1, 2026, and extends Claude Fable 5 at the same input and output prices. It takes text and image input, returns text, and uses adaptive thinking that is always on.
Model B — NVIDIA
Nemotron 3 Ultra is an open-weight language model from NVIDIA, released on June 4, 2026, which NVIDIA describes as frontier-scale, with 550B total and 55B active parameters in a hybrid Mamba-2, mixture-of-experts and attention architecture. It produces a reasoning trace before its answer and supports up to 1M tokens of context.
| Property | Claude Fable 5.1 | NVIDIA Nemotron 3 Ultra |
|---|---|---|
| Released | Sep 1, 2026 | Jun 4, 2026 |
| Developer | Anthropic | NVIDIA |
| Type | reasoning | reasoning |
| License | proprietary | open-weight |
| Context window | — | 1,048,576 |
| Parameters | — | 550B total, 55B active (LatentMoE: Mamba-2 + MoE + attention hybrid) |
| Developer status | — | — |
| Input $/M tokens | $10.00 | — |
| Output $/M tokens | $50.00 | — |
Bold green values indicate the winner on that dimension where comparison is meaningful (lower price wins; bigger context wins; more open license wins; newer date wins). Prices are the ones each developer lists today; a model it no longer prices has none.
Programmatic access available at /api/ai/compare?a=claude-fable-5-1&b=nemotron-3-ultra. CORS is open. Citation guidance: /about/editorial-process.