Fable 5.1 vs Opus 5.5
Claude Fable 5.1 vs Claude Opus 5.5
Overview
Fable 5.1 is Anthropic’s slower, always-on-thinking high tier ($10 / $50). Opus 5.5 is the cheaper high-end ($4 / $20) with moderate latency. If you already reach for Fable, this page is the case for demoting most turns to Opus.
When Fable vs when Opus
| Fable 5.1 | Opus 5.5 | |
|---|---|---|
| Role | Final pass / hardest spec | Default hard task |
| $ / MTok in-out | $10 / $50 | $4 / $20 |
| Speed | Slower | Moderate |
| Default effort | high | medium |
| Use if | Wrong answer is very expensive | You need quality without Fable’s bill |
Capabilities
- Fable as reviewerArchitecture reviews, legal-ish constraints, or a spec that Opus already failed once.
- Opus as workhorse-premiumMost “this is hard” coding still belongs on Opus, not Fable.
- Cost ratioSame 10K in + 2K out: Fable ≈ $0.10 + $0.10 = $0.20; Opus ≈ $0.04 + $0.04 = $0.08.
Context Window
Both 1M / 128K class. Putting a 200K repo sketch on Fable is $2 input before any output; on Opus it is $0.80.
- Cache on Fable if you truly stay there—reads are $0.25 / MTok.
- Otherwise cache on Opus and only lift the last turn to Fable.
Pricing
Anthropic list. Batch halves both SKUs. Confirm before procurement.
- Fable 5.1
- $10 / $50 · cache read $0.25 · batch $5 / $25
- Opus 5.5
- $4 / $20 · cache read $0.20 · batch $2 / $10
How to Use
- Ask if Opus already failedIf you have not tried Opus 5.5, try it first.
- One Fable passUse Fable to critique or rewrite, then continue on Opus or Sonnet.
- Cap spendSet a max Fable calls per ticket in your agent router.