Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) vs. Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback)

Comparison between Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) and Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) across intelligence, price, speed, context window and more.

For details relating to our methodology, see our Methodology page.

Highlights

Intelligence

Artificial Analysis Intelligence Index · Higher is better

Speed

Output tokens per second · Higher is better

Cost per Task

Weighted average cost (USD) per Intelligence Index task · Lower is better

Model Comparison

Anthropic logoAnthropic
Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback)
Anthropic logoAnthropic
Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback)
Intelligence Index
62
58
Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) is more intelligent than Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback)
Price per 1M Tokens
$7.17
$7.17
Both Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) and Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) have the same price
Output Speed
47 tokens/s
60 tokens/s
Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) is faster than Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback)
Time to First Token
34.57s
5.54s
Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) responds faster than Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback)
Context Window
1000k tokens~1,500 A4 pages of size 12 Arial font
1000k tokens~1,500 A4 pages of size 12 Arial font
Both Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) and Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) have the same sized context window
Release Date
September 2026
September 2026
Both Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) and Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) have the same release date
Reasoning
Yes
Yes
Both Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) and Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) have reasoning
Image Input Support
Yes
Yes
Both Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) and Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) have image input support
Open Source (Weights)
No
No
Both Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) and Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) are proprietary

Intelligence

Artificial Analysis Intelligence Index

Artificial Analysis Intelligence Index v4.1.1 incorporates 9 evaluations: GDPval-AA v2, 𝜏³-Banking, Terminal-Bench v2.1, SciCode, Humanity's Last Exam, GPQA Diamond, CritPt, AA-Omniscience, AA-LCR

Artificial Analysis Intelligence Index v4.1.1 includes: GDPval-AA v2, 𝜏³-Banking, Terminal-Bench v2.1, SciCode, Humanity's Last Exam, GPQA Diamond, CritPt, AA-Omniscience, AA-LCR. See Intelligence Index methodology for further details, including a breakdown of each evaluation and how we run them.

Artificial Analysis Intelligence Index by Open Weights / Proprietary

Artificial Analysis Intelligence Index v4.1.1 incorporates 9 evaluations: GDPval-AA v2, 𝜏³-Banking, Terminal-Bench v2.1, SciCode, Humanity's Last Exam, GPQA Diamond, CritPt, AA-Omniscience, AA-LCR

Artificial Analysis Intelligence Index v4.1.1 includes: GDPval-AA v2, 𝜏³-Banking, Terminal-Bench v2.1, SciCode, Humanity's Last Exam, GPQA Diamond, CritPt, AA-Omniscience, AA-LCR. See Intelligence Index methodology for further details, including a breakdown of each evaluation and how we run them.

Indicates whether the model weights are available. Models are labelled as 'Commercial Use Restricted' if commercial use is limited by conditions, and as 'Non-commercial' if the license prohibits commercial use.

Benchmarks

Intelligence Evaluations

Intelligence evaluations measured independently by Artificial Analysis · Higher is better
See more
GDPval-AA v2

Agentic real-world work tasks, (Elo-500)/2000

𝜏³-Banking

Agentic tool use

Terminal-Bench v2.1

Agentic coding & terminal use

SciCode

Coding

Humanity's Last Exam

Reasoning & knowledge

GPQA Diamond

Scientific reasoning

CritPt

Physics reasoning

AA-Omniscience Accuracy

Knowledge

AA-Omniscience Non-Hallucination Rate

1 - hallucination rate

AA-LCR

Long context reasoning

AA-Briefcase

Agentic knowledge work, Elo

AutomationBench-AA

Agentic SaaS workflows

No data available
Harvey LAB-AA

Legal agentic work, criterion pass rate

EnterpriseOps-Gym-AA

Agentic business operations

No data available
AA-AnalystAgent

Quantitative analysis on spreadsheets & documents

No data available
IFBench

Instruction following

No data available
APEX-Agents-AA

Long-horizon agentic tasks

No data available
ITBench-AA

Kubernetes incident root-cause analysis

No data available
MMMU-Pro

Visual reasoning

No data available

While model intelligence generally translates across use cases, specific evaluations may be more relevant for certain use cases.

Artificial Analysis Intelligence Index v4.1.1 includes: GDPval-AA v2, 𝜏³-Banking, Terminal-Bench v2.1, SciCode, Humanity's Last Exam, GPQA Diamond, CritPt, AA-Omniscience, AA-LCR. See Intelligence Index methodology for further details, including a breakdown of each evaluation and how we run them.

AA-Briefcase

AA-Briefcase Elo

AA-Briefcase is an agentic knowledge work benchmark developed by Artificial Analysis. AA-Briefcase Elo is a combined metric that aggregates rubric pass rate, analytical quality Elo and presentation Elo · Higher is better

AA-Briefcase Elo is a combined metric that aggregates analytical quality Elo, presentation Elo, and rubric pass rate, with rubric performance converted into Elo via synthetic head-to-head matches. Elo and 95% confidence interval bounds are clamped at 0.

AA-Omniscience

AA-Omniscience Index

AA-Omniscience Index (higher is better) measures knowledge reliability and hallucination. It rewards correct answers, penalizes hallucinations, and has no penalty for refusing to answer. Scores range from -100 to 100, where 0 means as many correct as incorrect answers, and negative scores mean more incorrect than correct.

AA-Omniscience Index (higher is better) measures knowledge reliability and hallucination. It rewards correct answers, penalizes hallucinations, and has no penalty for refusing to answer. Scores range from -100 to 100, where 0 means as many correct as incorrect answers, and negative scores mean more incorrect than correct.

Openness Index

Artificial Analysis Openness Index: Score

Openness Index assesses model openness on a 0 to 100 normalized scale (higher is more open)
No data available

Intelligence Index Comparisons

Intelligence Index vs. Cost per Intelligence Index Task

Artificial Analysis Intelligence Index · Weighted average cost (USD) per Artificial Analysis Intelligence Index task
Most attractive quadrant
Pareto line

Weighted average cost per Intelligence Index task. Each evaluation’s cost is calculated from input, cache hit, cache write, reasoning, and answer token prices, divided by task count, and weighted by its Intelligence Index weight.

Artificial Analysis Intelligence Index v4.1.1 includes: GDPval-AA v2, 𝜏³-Banking, Terminal-Bench v2.1, SciCode, Humanity's Last Exam, GPQA Diamond, CritPt, AA-Omniscience, AA-LCR. See Intelligence Index methodology for further details, including a breakdown of each evaluation and how we run them.

Token Use

Output Tokens per Intelligence Index Task

Weighted average number of output tokens used to run one task in the Artificial Analysis Intelligence Index

The number of tokens required per Intelligence Index task. This is calculated by multiplying the output tokens per eval by the relative weights of each benchmark in the Intelligence Index, then dividing by task count (excluding repeats).

Cost

Cost per Intelligence Index Task

Weighted average cost (USD) per Artificial Analysis Intelligence Index task, segmented by token type. Lower is better

Weighted average cost per Intelligence Index task. Each evaluation’s cost is calculated from input, cache hit, cache write, reasoning, and answer token prices, divided by task count, and weighted by its Intelligence Index weight.

Cost to Run Artificial Analysis Intelligence Index

Cost (USD) to run all evaluations in the Artificial Analysis Intelligence Index

The cost to run the evaluations in the Artificial Analysis Intelligence Index, calculated using the model's input, cache hit, cache write, reasoning, and answer token prices and the number of tokens used across evaluations (excluding repeats).

Pricing: Cache Hit, Input, and Output

Price (USD per M Tokens)

Price per token for cached prompts (previously processed), typically offering a significant discount compared to regular input price, represented as USD per million tokens. The values shown here are the cache hit price; cache write and cache storage are billed separately and vary by provider — see "Cache pricing by provider" for detail.

Context Window

Context Window

Context window: tokens limit · Higher is better

Larger context windows are relevant to RAG (Retrieval Augmented Generation) LLM workflows which typically involve reasoning and information retrieval of large amounts of data.

Maximum number of combined input & output tokens. Output tokens commonly have a significantly lower limit (varied by model).

Speed

Measured by Output Speed (tokens per second)

Output Speed

Output tokens per second · Higher is better

Tokens per second received while the model is generating tokens (ie. after first chunk has been received from the API for models which support streaming).

Figures represent performance of the model's first-party API (e.g. OpenAI for o1) or the median across providers where a first-party API is not available (e.g. Meta's Llama models).

Time per Intelligence Index Task

Weighted average decode time (minutes) per task; excludes TTFT and overhead time · Lower is better

The weighted average time (seconds) per Artificial Analysis Intelligence Index task. This is calculated by dividing output tokens per task by output speed, weighted by the relative weights of each benchmark in the Intelligence Index.

Latency

Measured by Time (seconds) to First Token

Latency: Time To First Answer Token

Seconds to first answer token received · Accounts for reasoning model 'thinking' time

Time to first answer token received, in seconds, after API request sent. For reasoning models, this includes the 'thinking' time of the model before providing an answer. For models which do not support streaming, this represents time to receive the completion.

End-to-End Response Time

Seconds to output 500 tokens, calculated based on time to first token, 'thinking' time for reasoning models, and output speed

End-to-End Response Time

Seconds to output 500 tokens, including reasoning model 'thinking' time · Lower is better

Seconds to receive a 500 token response. Key components:

  • Input time: Time to receive the first response token
  • Thinking time (only for reasoning models): Time reasoning models spend outputting tokens to reason prior to providing an answer. Amount of tokens based on the average reasoning tokens across a diverse set of 60 prompts (methodology details).
  • Answer time: Time to generate 500 output tokens, based on output speed

Figures represent performance of the model's first-party API (e.g. OpenAI for o1) or the median across providers where a first-party API is not available (e.g. Meta's Llama models).

Model Size (Open Weights Models Only)

Model Size: Total and Active Parameters

Comparison between total model parameters and parameters active during inference
No data available

The total number of trainable weights and biases in the model, expressed in billions. These parameters are learned during training and determine the model's ability to process and generate responses.

The number of parameters actually executed during each inference forward pass, expressed in billions. For Mixture of Experts (MoE) models, a routing mechanism selects a subset of experts per token, resulting in fewer active than total parameters. Dense models use all parameters, so active equals total.

Frequently Asked Questions

Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) is more intelligent. Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) scores 62, compared with Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) at 58 on the Artificial Analysis Intelligence Index.

Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) is faster. Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) generates 59.6 tokens per second, compared with Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) at 47.0 tokens per second.

Both models cost $7.17 per 1M tokens (7:2:1 cache hit/input/output ratio).

Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) has lower latency. Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) has a time to first token of 5.54s, compared with Claude Fable 5.1 (Adaptive Reasoning, High Effort, Default Fallback) at 34.57s.

Both models have a context window of 1.0M tokens.