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Claude Opus 5.5 vs Fable 5.1
Fable is Anthropic's top tier. Fable 5.1 came out on September 1, 2026; Opus 5.5 followed on September 22, 2026 at well under half the price.
Side by side
| Opus 5.5 | Fable 5.1 | |
|---|---|---|
| Released | September 22, 2026 | September 1, 2026 |
| Input / output per 1M | $4.00 / $20.00 | $10.00 / $50.00 |
| Cache hit per 1M | $0.20 | $0.25 |
| API model ID | claude-opus-5-5 | claude-fable-5-1 |
| Claude apps and Claude Code | Yes (paid plans) | Yes |
Benchmarks
From Anthropic's Opus 5.5 launch post.
| Benchmark | Opus 5.5 | Fable 5.1 |
|---|---|---|
| Terminal-Bench 4.0 | 66.4% | 55.8% |
| FrontierCode 1.1 | 54.4% | 50.3% |
| CursorBench 4.0 | 57.8% | 51.8% |
| AutomationBench | 40.0% | 31.4% |
| Humanity's Last Exam | 67.7% | 65.6% |
| OSWorld 2.1 | 81.8% | 80.7% |
Mythos 5.1, released with Fable 5.1, is only available to vetted cyberdefenders and life scientists.
Source: Anthropic: Introducing Claude Opus 5.5
Cost per coding task
| Codebase size | Opus 5.5 | Fable 5.1 |
|---|---|---|
| Small (< 10k lines) | $0.223 | $0.549 |
| Medium (10k-100k lines) | $0.498 | $1.222 |
| Large / monorepo (> 100k lines) | $1.188 | $2.910 |
At 173 tasks a month on a medium codebase: about $86 on Opus 5.5 and $211 on Fable 5.1.
Compare every model in the calculator
When Fable 5.1 still makes sense
- You already have Fable 5.1 prompts tuned and tested, and switching costs more than it saves.
- Your own evals show Fable 5.1 winning on your workload. Anthropic's benchmarks don't.
- Otherwise, move to Opus 5.5.
FAQ
Is there a Claude Fable 5.5?
No. The newest Fable model is Fable 5.1. Anthropic's 5.5 releases so far are Opus 5.5 and Sonnet 5.5, with Haiku 5.5 announced.
Is Opus 5.5 better than Fable 5.1?
On Anthropic's own table, yes: it leads on all 6 benchmarks shown. Anthropic also says it performs at Fable 5.1's level on most work.
How much cheaper is Opus 5.5 than Fable?
$4.00 / $20.00 against $10.00 / $50.00 per 1M tokens, so 2.5x cheaper per token.
Independent page. Not affiliated with Anthropic. Benchmarks are Anthropic's; we have not run our own tests.