GPT-5.6 Luna vs Claude Fable 5: API pricing
OpenAI's GPT-5.6 Luna against Anthropic's Claude Fable 5 on price alone — per-token rates, caching, and context window. Run your own workload through both with the calculator below; capability differences are yours to judge on your evals.
| GPT-5.6 Luna | Claude Fable 5 | |
|---|---|---|
| Input / 1M tokens | $0.20 | $10.00 |
| Cached input / 1M | $0.02 | $1.00 |
| Output / 1M tokens | $1.20 | $50.00 |
| Context window | 1M | 1M |
| Max output | 125K | 125K |
| Vendor | OpenAI | Anthropic |
Prices last synced Aug 20, 2026 from the LiteLLM community price catalog — the same catalog Marginal prices real usage events against, refreshed daily. Spot an error? Tell us.
Price takeaways
- Input: GPT-5.6 Luna is 50x cheaper.
- Output: GPT-5.6 Luna is 42x cheaper.
- Cached input: GPT-5.6 Luna is 50x cheaper.
- Ratios shift with workload shape — output-heavy traffic weights the output rate, cache-friendly traffic weights the cached rate. The calculator below does the arithmetic on your numbers.
Your workload on both
Your monthly workload
Cache hit rate = share of input tokens served from the provider's prompt cache, billed at the model's cached-input price. Estimates use standard per-token rates — batch discounts, service tiers, and long-context surcharges are not applied.
| Model | Input | Cached input | Output | Per request | Monthly |
|---|---|---|---|---|---|
| GPT-5.6 Lunacheapest | $120 | $8.00 | $300 | $0.00086 | $428 |
| Claude Fable 5 | $6,000 | $400 | $12,500 | $0.038 | $18,900 |
Related comparisons
Switching models? Watch the bill move in real time.
Marginal prices every call against that day's rates, so an A/B between these two shows up as dollars per customer and feature — not a surprise at month end.