Claude Fable 5 vs Claude Fable 5.1
Claude Fable 5.1 is the same price as Claude Fable 5, $10 input and $50 output per 1M tokens, with cached input cut from $1 to $0.25 and a higher Terminal-Bench 4.0 score: 55.8% against 42%. For any new Fable work, Fable 5.1 is the version to use.
What changed in Fable 5.1
Anthropic released Fable 5 on 9 June 2026 and Fable 5.1 about three months later, on 1 September. Context (1M tokens), output (128K tokens) and the input and output prices did not change. The cache did: cached input now costs a quarter of what it did.
Terminal-Bench 4.0 went from 42% to 55.8%. Humanity's Last Exam with tools moved less, from 63.8% to 65%, and the Opus 5.5 announcement later quoted 65.6% for Fable 5.1. Only Fable 5.1 has a FrontierCode 1.1 score, 50.3%, quoted in the same announcement.
Where the saving is: the cache
Without the cache the two cost the same: $54 for our feature session and $488 for a long agent day. With 90% of prompts read from the cache, Fable 5.1 costs $11.88 against $15.12 for the feature session and $92.63 against $123 for the long day.
Opus 5.5 scored higher than both Fables on every benchmark we track, at a lower price, so Fable 5.1 against Opus 5.5 is the comparison to read before you pay for Fable at all.
Side by side
| Claude Fable 5 | Claude Fable 5.1 | |
|---|---|---|
| Maker | Anthropic | Anthropic |
| Released | 9 June 2026[1] | 1 September 2026[2] |
| Context window | 1M tokens[1] | 1M tokens[2] |
| Max output | 128K tokens[1] | 128K tokens[2] |
| Input price | $10 per 1M tokens[1] | $10 per 1M tokens[2] |
| Output price | $50 per 1M tokens[1] | $50 per 1M tokens[2] |
| Cached input | $1 per 1M tokens[3] | $0.25 per 1M tokens[3] |
| Long prompts | One price | One price |
| Price change | None announced | None announced |
| Open weights | No[1] Offered through the Claude API and cloud platforms; no weights are published. | No[2] Offered through the Claude API and cloud platforms; no weights are published. |
| Reads | text, image[1] | text, image[2] |
Benchmarks
Scores as the makers published them, each with its source and date. Makers run these at different settings, so read a gap of a few points as a tie.
| Benchmark | Claude Fable 5 | Claude Fable 5.1 |
|---|---|---|
| Terminal-Bench 4.0Agentic coding tasks in a real terminal. | 42%[4] | 55.8%[4] |
| FrontierCode 1.1 (Main)Hard software engineering tasks. | Not published | 50.3%[5] Quoted in the Opus 5.5 announcement. |
| Humanity's Last Exam (with tools)Expert-level questions across many fields, tools allowed. | 63.8%[4] | 65%[4] The Opus 5.5 announcement later quoted 65.6%. |
What a coding session costs
Our own estimate from the list prices above, for three sessions we define: a coding agent resends the conversation with every call, so prompts are large and grow. "Cached" assumes 90% of prompt tokens are read from the prompt cache and leaves out cache write fees. A long-prompt price applies when a call's prompt is over its threshold. Work out your own mix with the token cost calculator.
| Session | Claude Fable 5 | Claude Fable 5 cached | Claude Fable 5.1 | Claude Fable 5.1 cached |
|---|---|---|---|---|
| Quick fix10 calls of 25K prompt and 1.5K output tokens | $3.25 | $1.23 | $3.25 | $1.06 |
| Feature session60 calls of 80K prompt and 2K output tokens | $54 | $15.12 | $54 | $11.88 |
| Long agent day300 calls of 150K prompt and 2.5K output tokens | $488 | $123 | $488 | $92.63 |
Value for money and release gap
Claude Fable 5.1 came out 3 months later (84 days). Price per point divides our feature-session cost by a published score: lower means more score for the money. It is a rough lens, not a ranking.
| Measure | Claude Fable 5 | Claude Fable 5.1 |
|---|---|---|
| Input tokens per $1 | 100K | 100K |
| Filling the whole context window once | $10 | $10 |
| Feature session per point of Terminal-Bench 4.0 | $1.29 | $0.97 |
| Feature session per point of Humanity's Last Exam (with tools) | $0.85 | $0.83 |
Questions
Is Fable 5.1 more expensive than Fable 5?
No. Both cost $10 per 1M input tokens and $50 per 1M output tokens. Cached input is cheaper on Fable 5.1: $0.25 against $1.
How much better is Fable 5.1 than Fable 5?
13.8 points on Terminal-Bench 4.0 (55.8% against 42%) and 1.2 points on Humanity's Last Exam with tools (65% against 63.8%). Fable 5 has no published FrontierCode 1.1 score.
When was Fable 5.1 released?
On 1 September 2026, about three months after Claude Fable 5, which came out on 9 June 2026.
Most compared
Any other two models: pick them in the lists at the top of the page.
- Claude Fable 5.1 vs Claude Opus 5.5
- Claude Fable 5.1 vs GPT-6 Astra
- Claude Opus 5.5 vs Claude Sonnet 5.5
- Claude Opus 5 vs Claude Opus 5.5
- Claude Sonnet 5 vs Claude Sonnet 5.5
- Claude Haiku 5.5 vs Claude Sonnet 5.5
- Claude Haiku 4.5 vs Claude Haiku 5.5
- Claude Opus 5.5 vs GPT-6.1 Sol
- Claude Sonnet 5.5 vs GPT-6.1 Sol
- Claude Opus 5.5 vs GPT-5.6 Sol
- Claude Opus 5.5 vs GPT-6 Astra
- Claude Haiku 5.5 vs GPT-6 Luna
- GPT-6.1 Sol vs GPT-6 Sol
- GPT-6.1 Sol vs GPT-6 Astra
- Claude Opus 5.5 vs Gemini 4 Argon
- Claude Sonnet 5.5 vs Gemini 4 Argon
- Claude Opus 5.5 vs Gemini 3.1 Pro Preview
- Gemini 4 Argon vs GPT-6.1 Sol
- Gemini 3.1 Pro Preview vs Gemini 4 Argon
- Claude Haiku 5.5 vs Gemini 3.8 Flash
- Claude Opus 5.5 vs Grok 4.7
- Claude Opus 5.5 vs DeepSeek V4 Pro
- Claude Sonnet 5.5 vs Kimi K3
- Claude Sonnet 5.5 vs GLM-5.3
More tools
Sources
Numbers from the makers' own pages, checked by hand, last read . List prices in US dollars before tax. Spotted a mistake? office@shuriken.sh.
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