text model comparison
Claude Fable 5.1 vs Claude Opus 5.5
Claude Fable 5.1 and Claude Opus 5.5 are both current text models, from Anthropic. Claude Opus 5.5 is 60% cheaper per 1M input tokens than Claude Fable 5.1, $4 vs $10. On Arena Text, Claude Fable 5.1 scores 1501 Elo and Claude Opus 5.5 1507 Elo (Arena, measured October 8, 2026). Both accept 1,000,000 tokens of context.
Data verified October 12, 2026 · Dataset 2026-10-12
Side by side
Standard-tier prices in effect today. The better value in each row is highlighted.
| Fact | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| Price per 1M input tokens | $10 | $4 (better) |
| Price per 1M output tokens | $50 | $20 (better) |
| Cost of 10M input and 2M output tokens | $200 | $80 (better) |
| Arena Text | 1501 Elo (#3 of 39) | 1507 Elo (#1 of 39) (better) |
| FrontierMath Tiers 1-3 (v2) | 90.2% (#4 of 37) | 91.2% (#3 of 37) (better) |
| SimpleQA Verified | 70.8% (#5 of 34) | 72.2% (#4 of 34) (better) |
| GPQA Diamond | Not measured | 90.6% (#22 of 37) |
| Provider | Anthropic | Anthropic |
| Release date | September 1, 2026 | September 22, 2026 |
| Access | API only | API only |
| Context window | 1,000,000 tokens | 1,000,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Input | text, image | text, image |
| Output | text | text |
When to choose each
Claude Fable 5.1
Best for
- Long-horizon agentic coding where a large prompt prefix is replayed across many turns
- Work where Claude Opus 5 at higher effort has already been evaluated and fell short
Watch out for
- Base input and output pricing is unchanged from Fable 5 at $10 / $50; the saving is entirely in cache reads, so a workload with little cache reuse sees no discount
- The 4.7-generation tokenizer produces roughly 30% more tokens for the same text than Claude Sonnet 4.6 and earlier, so per-token rates are not directly comparable across generations
- Anthropic’s launch comparisons are self-reported and were not reproduced independently here
Claude Opus 5.5
Best for
- Long-running agentic coding and knowledge work as the general-purpose default
- Cache-heavy agent loops where the 0.05x read multiplier compounds
Watch out for
- The API effort default is medium here, not high as on Claude Fable 5.1 and Claude Sonnet 5.5, so a like-for-like comparison has to set effort explicitly
- The 4.7-generation tokenizer produces roughly 30% more tokens for the same text than Claude Sonnet 4.6 and earlier, so per-token rates do not compare directly across generations
Claude Fable 5.1 vs Claude Opus 5.5 FAQ
Which is cheaper, Claude Fable 5.1 or Claude Opus 5.5?
Claude Opus 5.5 is 60% cheaper per 1M input tokens than Claude Fable 5.1, $4 vs $10. For 10M input and 2M output tokens, Claude Fable 5.1 costs $200 and Claude Opus 5.5 $80 at standard rates.
Which scores higher on independent benchmarks, Claude Fable 5.1 or Claude Opus 5.5?
Claude Opus 5.5 leads on Arena Text, 1507 Elo to 1501 Elo; Claude Opus 5.5 leads on FrontierMath Tiers 1-3 (v2), 91.2% to 90.2%; Claude Opus 5.5 leads on SimpleQA Verified, 72.2% to 70.8%. Scores are independent evaluations, not either vendor's launch figures.
Which has the larger context window, Claude Fable 5.1 or Claude Opus 5.5?
Both accept 1,000,000 tokens of context.
Related comparisons
- Claude Fable 5.1 vs Claude Mythos 5.1
- Claude Fable 5.1 vs GPT-5.5
- Claude Fable 5.1 vs GPT-6 Astra
- Claude Fable 5 vs Claude Fable 5.1
- Claude Fable 5 vs Claude Opus 5.5
- Claude Opus 4.8 vs Claude Opus 5.5
- Claude Opus 5.5 vs Gemini 3.8 Flash
- Claude Opus 5.5 vs GPT-5.5
- Claude Opus 5.5 vs GPT-5.6 Sol
- Claude Opus 5.5 vs Kimi K3
Production evaluation
Choosing between Claude Fable 5.1 and Claude Opus 5.5?
Public benchmarks narrow the shortlist. We run both on your own tasks, data and cost limits, then build the routing and review controls to run the winner in production.
- A head-to-head evaluation on your real workload
- Routing between models by cost and difficulty