AI Model Comparisons
Side-by-side pricing, benchmarks and specs for frontier models from Anthropic and OpenAI.
Last updated 2026-09-30 · Vendor data sourced from Anthropic and OpenAI
All Models at a Glance
| Spec | Claude Fable 5.1 | Claude Opus 5.5 | Claude Sonnet 5.5 | GPT-6 Astra |
|---|---|---|---|---|
| Vendor | Anthropic | Anthropic | Anthropic | OpenAI |
| Released | Sep 1, 2026 | Sep 22, 2026 | Sep 28, 2026 | Sep 3, 2026 |
| Input / output (per MTok) | $10 / $50 | $4 / $20 | $2 / $10 | $10 / $50 |
| Batch input / output | $5 / $25 | $2 / $10 | $1 / $5 | $5 / $25 |
| Context window | 1M tokens | 1M tokens | 1M tokens | 1.05M tokens |
| Max output | 128K tokens | 128K tokens (300K on Batch API) | 128K tokens (300K on Batch API) | 128K tokens |
| Latency | Slower | Moderate | Fast | Slower |
| Thinking | Adaptive, always on, cannot be disabled | Adaptive, always on, cannot be disabled | Adaptive; can be tuned with between_tools (no up-front thinking at effort <= high) | Reasoning model, effort configurable |
| Default effort | high | medium | high | medium |
| Knowledge cutoff | Jun 2026 | Jun 2026 | Jun 2026 | Apr 2026 |
Same-Vendor Comparisons (Anthropic)
Claude Opus 5.5 vs Claude Sonnet 5.5
Opus leads 7 of 8 benchmarks; Sonnet wins Terminal-Bench, is faster and costs half as much.
Claude Opus 5.5 vs Claude Fable 5.1
Opus is 60% cheaper, faster and scores higher on all seven benchmarks.
Cross-Vendor Comparisons (Anthropic vs OpenAI)
Model Comparison FAQ
Which Claude model should I use?
Sonnet 5.5 is the cheapest and fastest of the three and fits routine coding and everyday API work. Opus 5.5 leads most benchmarks and suits long-running agents and complex reasoning. Fable 5.1 is the premium tier at $10 / $50 per million tokens and is worth it only if your own evals show it pays off.
Claude vs GPT: which is cheaper?
Claude Opus 5.5 costs $4 / $20 per million input / output tokens and Sonnet 5.5 costs $2 / $10, versus $10 / $50 for GPT-6 Astra. Per-token price is not the same as per-task cost, so benchmark on your own workload before deciding.
How often is this data updated?
Specs and prices come from each vendor's official documentation and are re-verified whenever a model or price changes. Every comparison page shows its last-updated date.