Claude Fable 5.1 vs Claude Opus 5.5: API price, context and cost per task
Anthropic's two top models. Opus 5.5 launched a month after Fable 5.1 and beats it on several of Anthropic's own tests while costing well under half as much per token.
On output, Claude Opus 5.5 is 2.5x cheaper ($20 vs $50 per million tokens). On input, Claude Opus 5.5 is 2.5x cheaper ($4 vs $10 per million tokens).
Data updated 2026-11-11 - source: public OpenRouter model list, refreshed daily. Prices in USD, excluding VAT.
Specs and prices side by side
| Claude Fable 5.1 | Claude Opus 5.5 | |
|---|---|---|
| Vendor | Anthropic | Anthropic |
| Input, per 1M tokens | $10 | $4 |
| Output, per 1M tokens | $50 | $20 |
| Cached input, per 1M | $0.25 | $0.2 |
| Batch (input / output) | $5 / $25 | $2 / $10 |
| Context window | 1,000,000 | 1,000,000 |
| Max output | 128,000 | 128,000 |
| Input types | text, images, files | text, images, files |
| Reasoning | Yes | Yes |
| Tool calling | Yes | Yes |
| On OpenRouter since | 1 Sep 2026 | 22 Sep 2026 |
Highlighted: the cheaper price or the larger limit. "Not published" means the figure is not in the public model listing yet.
What a month of work costs
Four typical workloads at today's list prices. Reasoning models also bill their thinking as output tokens, so treat output-heavy numbers as a floor.
| Workload | Claude Fable 5.1 | Claude Opus 5.5 | Difference |
|---|---|---|---|
| Support chatbot10,000 conversations a month, about 1,500 input and 400 output tokens each | $350 | $140 | Claude Opus 5.5 2.5x cheaper |
| Coding agent300 tasks a month, about 80,000 input tokens (code context re-read across steps) and 8,000 output tokens each | $360 | $144 | Claude Opus 5.5 2.5x cheaper |
| Coding agent with caching70% of input served from the prompt cache | $196 | $80.16 | |
| Long-document analysis1,000 documents a month, about 50,000 tokens in and a 1,500-token summary out | $575 | $230 | Claude Opus 5.5 2.5x cheaper |
| Content drafting600 articles a month, about 3,000 tokens of brief in and 2,500 tokens of draft out | $93 | $37.20 | Claude Opus 5.5 2.5x cheaper |
Price stability over the last 30 days
- Claude Fable 5.1: no change in the last 30 days.
- Claude Opus 5.5: no change in the last 30 days.
What the vendors and benchmarks say
Claude Fable 5.1
"Claude Fable 5.1 improves on Claude Fable 5 across the board, with the biggest gains in agentic coding, long-running agentic workflows, and knowledge work: long code refactors, front-end and visual..."model card on OpenRouter
- A refresh of the Fable 5 line, released on 20 August 2026. Anthropic withdrew Fable 5 in June 2026 and restored it on 1 July. Source: Anthropic
- Terminal-Bench 4.0: 55.8%; GDPval-AA v2.1: 1735 Elo. Source: Anthropic's Claude Opus 5.5 launch comparison
Claude Opus 5.5
"Claude Opus 5.5 is Anthropic's flagship model for demanding reasoning, coding, and long-horizon agentic work, succeeding Claude Opus 5."model card on OpenRouter
- Released on 22 September 2026 as the first model of the Claude 5.5 family. Source: Anthropic
- Anthropic says a typical task at default settings costs 40% less than on Opus 5, because the model uses fewer tokens, and that generation is over 30% faster. Source: Anthropic
- Thinking is always on and cannot be switched off; the default effort level is medium (Opus 5 defaulted to high). Source: Anthropic model documentation
- Terminal-Bench 4.0: 66.4%; GDPval-AA v2.1: 1846 Elo. In Anthropic's test, 16 of 18 reports written from incomplete sources contained no invented figure. Source: Anthropic
- Fast mode costs $8 / $40 and batch mode $2 / $10 per million tokens; knowledge cutoff June 2026. Source: Anthropic
Which one to pick
On Anthropic's published numbers Opus 5.5 is ahead of Fable 5.1 on Terminal-Bench 4.0 (66.4% vs 55.8%) and GDPval-AA v2.1 (1846 vs 1735). In Anthropic's sourcing test, 16 of 18 Opus 5.5 reports written from incomplete sources contained no invented figure, while Fable 5.1 passed none. Unless a specific task works measurably better on Fable 5.1 in your own tests, Opus 5.5 is the default. Note that Opus 5.5 always thinks - reasoning cannot be switched off - which adds output tokens.
Cheaper models with a similar context window
Models from our comparison set that cost less than both on a blended basis and support tool calling. They are not equivalent in quality - test before switching.
- Kimi K3 (Moonshot AI): $0.192 / $16 per million tokens, 1.05M context
- GPT-6.1 Sol (OpenAI): $2 / $10 per million tokens, 1.05M context
- GPT-6 Sol (OpenAI): $2 / $10 per million tokens, 1.05M context
Related reading
- Muse Wonder vs Claude Opus 5.5, Fable 5.1 and GPT-6 Astra: Benchmarks
- Fable 5.1 vs Mythos 5.1: One Model, Two Rule Sets
- Claude Fable 5.1: Pricing, Features & Review (2026)
- Claude Fable 5.2 vs Opus 5.5: Price, Benchmarks, Which to Pick
- Claude Opus 5.5 vs GPT-6 Astra: Plan or API?
- Claude Pro vs. Max vs. API: Opus 5.5 costs compared
How we calculate
Prices are the public per-token list rates from OpenRouter's model list, which match the vendors' own API prices for first-party models and show the current routed price for open-weight models served by several hosts. Monthly costs multiply those rates by the token volumes in each workload; caching assumes the stated share of input is billed at the cached-input rate. Benchmarks and claims are quoted from the named sources, mostly the vendors themselves - treat them as a guide and test on your own tasks. See also the AI cost calculator and all tracked model prices.
Frequently asked questions
Which is cheaper, Claude Fable 5.1 or Claude Opus 5.5?
As of 11 Nov 2026, Claude Fable 5.1 costs $10 per million input tokens and $50 per million output tokens; Claude Opus 5.5 costs $4 and $20. Claude Fable 5.1 is cheaper in 0 of the 4 monthly workloads we price on this page. The real bill also depends on how many reasoning tokens each model writes.
Which has the larger context window?
Claude Fable 5.1 reads up to 1,000,000 tokens and can write up to 128,000; Claude Opus 5.5 reads up to 1,000,000 and writes up to 128,000.
How much does a support chatbot cost on each model?
For 10,000 conversations a month (about 15 million input and 4 million output tokens) you would pay about $350 on Claude Fable 5.1 and $140 on Claude Opus 5.5 at list prices, before any caching or batch discounts.
Do they offer prompt caching or batch discounts?
Claude Fable 5.1 lists cached input at $0.25 per million and a batch rate of $5 / $25. Claude Opus 5.5 lists cached input at $0.2 per million and a batch rate of $2 / $10. Caching matters most for agents and chatbots that resend the same context on every turn.
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