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Claude Fable 5.1 vs Claude Mythos Preview

Claude Fable 5.1 and Claude Mythos Preview are closely matched at 54.8 and 55.6 on the LLM Stats Score. Claude Fable 5.1 is 2.5x cheaper per token.

Anthropic · Anthropic · Updated for 2026

Which is better?

Claude Fable 5.1 and Claude Mythos Preview are closely matched on the overall LLM Stats Score at 54.8 and 55.6.

In the 1 individual benchmarks reported for both models, Claude Fable 5.1 wins 1; this is a narrower head-to-head signal than the composite indexes.

On price, Claude Fable 5.1 is roughly 2.5x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Fable 5.1

  • you value its reported benchmark strengths — it wins 1 of 1 exact shared results
  • cost matters — it's about 2.5x cheaper per token

Choose Claude Mythos Preview

  • you want predictable pricing at $25.00/M input and $125.00/M output

At a glance

The differences that matter most.

Claude Fable 5.1
Anthropic
Claude Mythos Preview
Anthropic
Core performance indexes
LLM Stats Score
54.8
#5
55.6
#2
Reasoning
52.1
#7
56.3
#1
Agents
39.3
#6
36.8
#13
Cost, coverage & limits
Benchmark wins
1 of 1
0 of 1
Input price
$10.00 / M
$25.00 / M
Output price
$50.00 / M
$125.00 / M
Context window
1,000,000
—

Capability indexes

Additional strengths measured across groups of related public benchmarks

1 shared
Index
Claude Fable 5.1
Claude Mythos Preview
Vision
40.5#1
39.1#2
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

7 reported for Claude Fable 5.1 · 16 for Claude Mythos Preview

1 shared

Claude Fable 5.1 outperforms in 1 benchmarks (Humanity's Last Exam), while Claude Mythos Preview is better at 0 benchmarks.

Claude Fable 5.1 significantly outperforms across most benchmarks.

Wed Sep 02 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Claude Fable 5.1 costs less

For input processing, Claude Fable 5.1 ($10.00/1M tokens) is 2.5x cheaper than Claude Mythos Preview ($25.00/1M tokens).

For output processing, Claude Fable 5.1 ($50.00/1M tokens) is 2.5x cheaper than Claude Mythos Preview ($125.00/1M tokens).

In conclusion, Claude Mythos Preview is more expensive than Claude Fable 5.1.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Wed Sep 02 2026 • llm-stats.com
Anthropic
Claude Fable 5.1
Input tokens$10.00
Output tokens$50.00
Best providerAnthropic
Anthropic
Claude Mythos Preview
Input tokens$25.00
Output tokens$125.00
Best providerAnthropic
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Only Claude Fable 5.1 specifies input context (1,000,000 tokens). Only Claude Fable 5.1 specifies output context (128,000 tokens).

Anthropic
Claude Fable 5.1
Input1,000,000 tokens
Output128,000 tokens
Anthropic
Claude Mythos Preview
Input- tokens
Output- tokens
Wed Sep 02 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Fable 5.1 and Claude Mythos Preview support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

Claude Fable 5.1

Text
Images
Audio
Video

Claude Mythos Preview

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

Claude Fable 5.1

Proprietary

Closed source

Claude Mythos Preview

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Fable 5.1 was released on 2026-09-01, while Claude Mythos Preview's release date is not specified.

We can confirm Claude Fable 5.1's release timeline, but cannot make a direct age comparison without Claude Mythos Preview's release date.

Claude Fable 5.1

Sep 1, 2026

0 days ago

Claude Mythos Preview

—

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Provider Availability

Claude Fable 5.1 is available from Anthropic. Claude Mythos Preview is available from Anthropic.

Claude Fable 5.1

anthropic logo
Anthropic
Input Price:Input: $10.00/1MOutput Price:Output: $50.00/1M

Claude Mythos Preview

anthropic logo
Anthropic
Input Price:Input: $25.00/1MOutput Price:Output: $125.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Fable 5.1 and Claude Mythos Preview side-by-side, then vote on the output you prefer.

Claude Fable 5.1
✓ Preferred
Claude Mythos Preview
Open in Playground

FAQ

Common questions about Claude Fable 5.1 vs Claude Mythos Preview.

Which is better, Claude Fable 5.1 or Claude Mythos Preview?

Claude Fable 5.1 and Claude Mythos Preview are closely matched on the LLM Stats Score at 54.8 and 55.6. Claude Fable 5.1 is made by Anthropic and Claude Mythos Preview is made by Anthropic. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Fable 5.1 compare to Claude Mythos Preview in benchmarks?

Claude Fable 5.1 scores OSWorld 2.0: 77.9%, CursorBench v3.2: 73.4%, Humanity's Last Exam: 65.0%, GDPval-AA: 61.8%, Terminal-Bench 4.0: 55.8%. Claude Mythos Preview scores CyBench: 100.0%, USAMO25: 97.6%, GPQA: 94.6%, SWE-Bench Verified: 93.9%, CharXiv-R: 93.2%.

Is Claude Fable 5.1 cheaper than Claude Mythos Preview?

Claude Fable 5.1 is 2.5x cheaper for input tokens. Claude Fable 5.1 costs $10.00/M input and $50.00/M output via anthropic. Claude Mythos Preview costs $25.00/M input and $125.00/M output via anthropic.

What are the context window sizes for Claude Fable 5.1 and Claude Mythos Preview?

Claude Fable 5.1 supports 1.0M tokens and Claude Mythos Preview supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Fable 5.1 and Claude Mythos Preview?

Key differences include LLM Stats Score (54.8 vs 55.6), input pricing ($10.00 vs $25.00/M). See the full comparison above for benchmark-by-benchmark results.

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