Anthropic · Long and demanding tasks
Claude Fable 5.1
A variant for demanding work where longer processing times and higher costs are acceptable.
- Costs
- $10 input / $50 output per million tokens in standard API mode.
- Speed
- The provider ranks it among the slower models in the Claude family.
- Availability
- Claude API, Amazon Bedrock, Google Cloud and Microsoft Foundry
- Input length
- 1 million tokens; output capped at 128 thousand tokens.
- Inputs
- Text and images → text
Data checked . Published September 1, 2026. Specifications and prices are provided by the vendor; usage recommendations come from the editorial team. We do not yet have our own comparative test of this version.
Ideal use
When to choose it
- Complex tasks with multiple sequential steps
- Working with extensive context and code
Usage boundaries
When to choose another model
- When you need the fastest possible response or the lowest costs.
Traceable supporting sources
Data and measurement sources
Distinguish between the manufacturer's documentation and the results of a specific test. Measurements also depend on the settings and the task set used.
Vendor documentation
Specifications, availability, and termsManufacturer data verified as of the review date. Recommended use is an editorial interpretation.
Open original source ↗Efficiency in practice
With what Claude Fable 5.1 combine
Documents → analysis → verification
A fast model prepares the material, and a stronger model focuses on analyzing it.
Agreement between two models is not proof; the cited inputs are what matters.Trends over time
Related events from AI Radar
Claude Opus 5.5 available on Amazon Bedrock with lower costs per task
According to Anthropic, developers working with long-running agentic tasks or extensive documents can expect clearer ongoing updates on model progress and less need to correct outputs, but also more frequent refusals of requests due to stricter safety classifiers.
According to Anthropic, companies running agentic tasks on Amazon Bedrock may achieve lower average costs per task thanks to lower token prices and significantly cheaper cache reads, which is particularly relevant for long-running and repeated workloads.
OpenAI halved prices for the GPT-6 Sol and Luna models; independent analysis does not confirm a performance improvement
New: Anthropic released Claude Opus 5.5 on the same day (2026-09-23), roughly an hour after OpenAI; Claude Opus 5.5 is 20% cheaper than the previous Opus 5.0 ($4/$20 vs $5/$25); Opus 5.5 improved communication style and token efficiency; The model releases launch a 'price war' between the two largest AI companies; GPT-6 Luna and Sol are part of a broader strategy of price competition, not an isolated release
Developers working with the API from OpenAI can reduce inference costs by up to half while maintaining the same usage pattern (Sol for more complex tasks, Luna for high-volume simple tasks), but independent tests suggest that a lower price may not mean higher or even the same output quality in all cases.
Businesses gain a cheaper option for reasoning models for high-volume or repetitive tasks (summaries, data extraction, code), but according to an independent analysis, actual output quality has not improved compared with the previous generation and has instead declined on some knowledge work tasks, so deployment decisions should not rely solely on the manufacturer's claims about price/performance.
OpenAI opens the Pro plan to new users, but halves API credits and moves toward payment for actual usage
New: API credits per dollar halved; Pro plan at $200/month reopened to new users; 5-hour window for the weekly allotment removed; Strategic shift from subsidized subscription models to pay-per-use pricing; Microsoft is making similar changes with Copilot
Users considering the OpenAI Pro plan at $200/month now also benefit from the removal of the 5-hour limit, but those paying through the API receive fewer credits for the same dollar than before — the new lower prices of the GPT-6 Sol and Luna models only partially offset this.
Companies using the OpenAI API should recalculate their AI operating costs, because the number of credits per dollar is changing and the price of the new GPT-6 Sol and Luna models has also fallen by 50 % compared with the 5.6 series — the net impact on the budget depends on the specific usage volume and types of models used.
Nathan Lambert (AI2): in his view, fears of imminent superintelligence reflect cultural panic, rather than a technical breakthrough
Those following debates about the pace of AI progress get an argument for a more measured reading of warnings about imminent superintelligence and for distinguishing between measurable acceleration from deploying agents and genuinely recursively self-improving AI.
Next step
Compare the model using your actual task.
A benchmark narrows the selection. A short trial on your data determines the choice.