Claude Fable 5.1 vs Claude Opus 5.5
Claude Opus 5.5 scored higher than Claude Fable 5.1 on every benchmark both have published, and it costs $4 input and $20 output per 1M tokens against Fable's $10 and $50. For coding-agent work at list prices Opus 5.5 is the better buy: Fable 5.1 costs 2.5 times as much for lower published scores.
How Fable 5.1 and Opus 5.5 compare
Anthropic released Fable 5.1 on 1 September 2026 and Opus 5.5 three weeks later, on 22 September. They have the same limits: 1M tokens of context, 128K tokens of output, text and images in.
Opus 5.5 leads on all three scores. Terminal-Bench 4.0: 66.4% against 55.8%, with Opus run at xhigh effort. FrontierCode 1.1: 54.4% against 50.3%, Fable's figure being the one quoted in the Opus 5.5 announcement. Humanity's Last Exam with tools: 67.7% against 65%, though the same announcement later quoted 65.6% for Fable.
What the price gap means in a session
Our feature session costs $54 on Fable 5.1 and $21.60 on Opus 5.5. With 90% of prompts read from the cache it is $11.88 against $5.18; the gap narrows a little there, because Fable's cached input ($0.25) is close to Opus's ($0.20). A long agent day costs $488 against $195 without the cache.
Divide the feature session by the Terminal-Bench score and Fable 5.1 costs $0.97 per point, Opus 5.5 $0.33. That is a rough lens, not a ranking, but it points the same way as everything else on this page.
When Fable 5.1 still makes sense
Benchmarks average over tasks that may not look like yours. If a workflow is already tuned on Fable 5.1, run the same tasks on Opus 5.5 before moving it. Our Fable vs Opus for coding comparison makes the case for where the top model still earns its price.
Side by side
| Claude Fable 5.1 | Claude Opus 5.5 | |
|---|---|---|
| Maker | Anthropic | Anthropic |
| Released | 1 September 2026[1] | 22 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] | $4 per 1M tokens[2] |
| Output price | $50 per 1M tokens[1] | $20 per 1M tokens[2] |
| Cached input | $0.25 per 1M tokens[3] | $0.20 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 5.1 | Claude Opus 5.5 |
|---|---|---|
| Terminal-Bench 4.0Agentic coding tasks in a real terminal. | 55.8%[4] | 66.4%[5] Run at xhigh effort. |
| FrontierCode 1.1 (Main)Hard software engineering tasks. | 50.3%[5] Quoted in the Opus 5.5 announcement. | 54.4%[5] Max effort. |
| Humanity's Last Exam (with tools)Expert-level questions across many fields, tools allowed. | 65%[4] The Opus 5.5 announcement later quoted 65.6%. | 67.7%[5] |
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 5.1 | Claude Fable 5.1 cached | Claude Opus 5.5 | Claude Opus 5.5 cached |
|---|---|---|---|---|
| Quick fix10 calls of 25K prompt and 1.5K output tokens | $3.25 | $1.06 | $1.30 | $0.45 |
| Feature session60 calls of 80K prompt and 2K output tokens | $54 | $11.88 | $21.60 | $5.18 |
| Long agent day300 calls of 150K prompt and 2.5K output tokens | $488 | $92.63 | $195 | $41.10 |
Value for money and release gap
Claude Opus 5.5 came out 3 weeks later (21 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 5.1 | Claude Opus 5.5 |
|---|---|---|
| Input tokens per $1 | 100K | 250K |
| Filling the whole context window once | $10 | $4.00 |
| Feature session per point of Terminal-Bench 4.0 | $0.97 | $0.33 |
| Feature session per point of FrontierCode 1.1 (Main) | $1.07 | $0.40 |
| Feature session per point of Humanity's Last Exam (with tools) | $0.83 | $0.32 |
Questions
Is Claude Opus 5.5 better than Fable 5.1?
On published scores, yes: 66.4% against 55.8% on Terminal-Bench 4.0, 54.4% against 50.3% on FrontierCode 1.1 and 67.7% against 65% on Humanity's Last Exam with tools.
How much does Fable 5.1 cost compared with Opus 5.5?
$10 input and $50 output per 1M tokens, against $4 and $20 for Opus 5.5. Our feature session costs $54 on Fable 5.1 and $21.60 on Opus 5.5.
Which came out first, Fable 5.1 or Opus 5.5?
Claude Fable 5.1, on 1 September 2026. Claude Opus 5.5 followed on 22 September 2026, three weeks later.
Most compared
Any other two models: pick them in the lists at the top of the page.
- Claude Opus 5.5 vs Claude Sonnet 5.5
- Claude Opus 5 vs Claude Opus 5.5
- Claude Fable 5 vs Claude Fable 5.1
- Claude Opus 5.5 vs GPT-6.1 Sol
- Claude Opus 5.5 vs GPT-5.6 Sol
- Claude Fable 5.1 vs GPT-6 Astra
- Claude Opus 5.5 vs GPT-6 Astra
- Claude Opus 5.5 vs Gemini 4 Argon
- Claude Opus 5.5 vs Gemini 3.1 Pro Preview
- Claude Opus 5.5 vs Grok 4.7
- Claude Opus 5.5 vs DeepSeek V4 Pro
- 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 Sonnet 5.5 vs GPT-6.1 Sol
- 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 Sonnet 5.5 vs Gemini 4 Argon
- 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 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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