No shared benchmark table
Anthropic did not benchmark Claude Fable 5.1 against Claude Opus 4.8 in the 1 September 2026 launch table. The most-requested comparison in autosuggest, but the published scores do not exist side by side. State the absence plainly.
Price and capability
Claude Fable 5.1 lists at $10 per 1M input and $50 per 1M output, with a 1M-token context window at standard pricing. Claude Opus 4.8 lists at lower published rates but with a smaller context window (200K). For long-context workloads the Fable family wins on cost per cached token; for short, latency-sensitive calls Opus 4.8 is the cheaper route.
Ready to test the workflow?
Create account & add creditsBehaviour differences
Claude Opus 4.8 is the documented fallback target for high-risk queries in some Anthropic enterprise deployments. Fable 5.1 introduces the anti-distillation context rule for accounts created on or after 31 August 2026; Opus 4.8 does not.
| Capability | Fable 5.1 | Opus 4.8 |
|---|---|---|
| Context window | 1,000,000 | 200,000 |
| Input $/1M | $10.00 | lower |
| Output $/1M | $50.00 | lower |
| Cache read $/1M | $0.25 | not published |
| Five effort levels | Yes | No |
| Anti-distillation rule | Yes (new accounts) | No |
Frequently asked questions
Should I switch from Claude Opus 4.8 to Claude Fable 5.1?
Switch if your workload is long-context (over 200K tokens) or cache-heavy. Stay on Opus 4.8 if your workload is short, latency-sensitive, and you depend on the existing integration patterns.
Put Claude Fable 5.1 to work
Fund a controlled evaluation, start with a prepared prompt, and measure quality and cost on your own workload.