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Claude Fable 5.1 vs Claude Opus 5
A straight cost comparison of Claude Fable 5.1 (Anthropic) and Claude Opus 5 (Anthropic), per 1,000,000 tokens, verified October 2026.
Rate-by-rate comparison
| Metric | Claude Fable 5.1 | Claude Opus 5 | Winner |
|---|---|---|---|
| Input / 1M | $10 | $5 | Claude Opus 5 |
| Cached input / 1M | $0.25 | $0.50 | Claude Fable 5.1 |
| Cache write / 1M | $12.50 | $6.25 | Claude Opus 5 |
| Output / 1M | $50 | $25 | Claude Opus 5 |
| Context window | 1,000,000 | 1,000,000 | Tie |
| Batch API | Yes | Yes | Tie |
| Long-context tier | None | None | — |
For per-token metrics, the lower number wins. For context window and batch support, the higher or broader option wins. A dash means the provider does not publish that rate: a missing cache-write fee means writes are not billed per token, while a missing cached-input rate means cache hits bill at the full input rate.
Blended cost: 1M input + 250K output
| Model | Blended cost | Difference |
|---|---|---|
| Claude Fable 5.1 | $22.50 | +$11.25 |
| Claude Opus 5 | $11.25 | Cheaper |
Three workloads, two bills
| Workload | Claude Fable 5.1 | Claude Opus 5 | Winner |
|---|---|---|---|
| Support chat 1,000 requests · 4K input / 600 output | $70 | $35 | Claude Opus 5 |
| RAG with caching 1,000 requests · 50K input (45K cached) / 1K output | $112 | $72.76 | Claude Opus 5 |
| Nightly batch job 10,000 requests · 10K input / 2K output | $1000 | $500 | Claude Opus 5 |
Which one should you pick?
Claude Fable 5.1 wins on none of the three workloads above, while Claude Opus 5 wins on support chat, cached RAG, nightly batch job.
Beyond price, the two differ on input rate ($10 vs $5); output rate ($50 vs $25); cached-input rate ($0.25 vs $0.50); cache-write rate ($12.50 vs $6.25).
Batch mode is available on Claude Fable 5.1 and Claude Opus 5, which halves the nightly job. Both publish cached-input discounts, so a stable system prompt is worth caching on either.
FAQ
Is Claude Fable 5.1 cheaper than Claude Opus 5?
On a blended 1M-input-plus-250K-output workload, Claude Opus 5 is cheaper by 50% ($11.25 vs $22.50). The gap changes for cache-heavy prompts and for batch jobs, as the workload table shows.
Which handles longer prompts, Claude Fable 5.1 or Claude Opus 5?
Both models share the same 1,000,000-token context window. Neither model publishes a long-context surcharge.
Do both models support prompt caching?
Claude Fable 5.1 bills cached reads at $0.25 per 1M; Claude Opus 5 at $0.50.