Claude Fable 5.1 vs Claude Sonnet 5.5: Specs & Benchmark Comparison
Claude Fable 5.1 and Claude Sonnet 5.5 both come from Anthropic, and both were released in September 2026.
The two models share 3 published benchmarks. Claude Sonnet 5.5 leads on 3 of them. The widest gaps are on Terminal-Bench 4.0, where Claude Sonnet 5.5 scores 70.6% against 55.8%; AutomationBench, where Claude Sonnet 5.5 scores 44.7% against 31.4%. Averaged across everything we track, Claude Fable 5.1 sits at 59.7% and Claude Sonnet 5.5 at 67.4%.
Claude Sonnet 5.5 is the cheaper API at $2 per million input tokens and $10 per million output tokens, roughly 5 times cheaper than Claude Fable 5.1 at $10 and $50. Both accept a context window of about 1M tokens. Both accept text and images as input.
| Characteristic | Claude Fable 5.1 | Claude Sonnet 5.5 |
|---|---|---|
| Company | Anthropic | Anthropic |
| Release Date | September 1, 2026 | September 28, 2026 |
| Parameters | — | — |
| Multimodal | Yes | Yes |
| Context (input) | 1.0M | 1.0M |
| Context (output) | 128K | 128K |
| Input Price / 1M | $10.00 | $2.00 |
| Output Price / 1M | $50.00 | $10.00 |
| Average Score | 59.7% | 67.4% |
| Benchmarks | ||
| Terminal-Bench 4.0 | 55.8% | 70.6% |
| AutomationBench | 31.4% | 44.7% |
| Terminal-Bench-Science 0.1 | 52.6% | 59.9% |
Visual Benchmark Comparison
Verdict
Claude Sonnet 5.5 leads in 2 out of 4 comparison categories.
Both models show comparable average scores: Claude Fable 5.1 — 0.6, Claude Sonnet 5.5 — 0.7.
Claude Sonnet 5.5 is 5.0x cheaper: input $2.00/1M vs $10.00/1M tokens.
Same context size: 1M tokens.
Claude Sonnet 5.5 is newer: released 9/28/2026 vs 9/1/2026.
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Frequently Asked Questions
Which is better for coding — Claude Fable 5.1 or Claude Sonnet 5.5?
Which model is cheaper — Claude Fable 5.1 or Claude Sonnet 5.5?
Which has a larger context window — Claude Fable 5.1 or Claude Sonnet 5.5?
The Claude Fable 5.1 and Claude Sonnet 5.5 comparison is updated for 2026. Data includes benchmark results, API pricing, context window size and other specifications. For more detailed information, visit the Claude Fable 5.1 or Claude Sonnet 5.5 page. See also the complete list of AI model comparisons.