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 — OpenAI
GPT-6 Luna is a reasoning model from OpenAI, released on September 22, 2026, which OpenAI describes as its most efficient model for focused, high-volume tasks. It takes text and image input, returns text, and has a May 18, 2026 knowledge cutoff.
| Property | Claude Fable 5.1 | GPT-6 Luna |
|---|---|---|
| Released | Sep 1, 2026 | Sep 22, 2026 |
| Developer | Anthropic | OpenAI |
| Type | reasoning | reasoning |
| License | proprietary | proprietary |
| Context window | — | 1,050,000 |
| Parameters | — | — |
| Developer status | — | — |
| Input $/M tokens | $10.00 | $0.10 |
| Output $/M tokens | $50.00 | $0.50 |
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.
No exclusive capabilities
Programmatic access available at /api/ai/compare?a=claude-fable-5-1&b=gpt-6-luna. CORS is open. Citation guidance: /about/editorial-process.