Claude Fable 5.1 vs Mercury 2
Claude Fable 5.1 leads the LLM Stats Score 56.8 to 23.7. Mercury 2 is 53.3x cheaper per token.
Anthropic · Inception · Updated for 2026
Which is better?
Claude Fable 5.1 leads the overall LLM Stats Score 56.8 to 23.7, ranking #2 overall.
On price, Mercury 2 is roughly 53.3x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Claude Fable 5.1 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Claude Fable 5.1
- overall performance matters — it scores 56.8 and ranks #2 on LLM Stats
- your work emphasizes reasoning and coding — it leads those capability indexes
- you process long inputs — it offers a 1,000,000 token context window
- you want the most recent training data — it shipped Sep 2026
Choose Mercury 2
- cost matters — it's about 53.3x cheaper per token
At a glance
The differences that matter most.
Individual benchmarks
7 reported for Claude Fable 5.1 · 6 for Mercury 2
Claude Fable 5.1 and Mercury 2don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Fable 5.1 ($10.00/1M tokens) is 40.0x more expensive than Mercury 2 ($0.25/1M tokens).
For output processing, Claude Fable 5.1 ($50.00/1M tokens) is 66.7x more expensive than Mercury 2 ($0.75/1M tokens).
In conclusion, Claude Fable 5.1 is more expensive than Mercury 2.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Claude Fable 5.1 accepts 1,000,000 input tokens compared to Mercury 2's 128,000 tokens. Claude Fable 5.1 can generate longer responses up to 128,000 tokens, while Mercury 2 is limited to 8,192 tokens.
Input capabilities
Documented input modalities across available providers
Claude Fable 5.1 supports multimodal inputs, whereas Mercury 2 does not.
Claude Fable 5.1 can handle both text and other forms of data like images, making it suitable for multimodal applications.
Claude Fable 5.1
Mercury 2
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Claude Fable 5.1 was released on 2026-09-01, while Mercury 2 was released on 2026-02-24.
Claude Fable 5.1 is 6 months newer than Mercury 2.
Sep 1, 2026
3 days ago
6mo newerFeb 24, 2026
6 months ago
Knowledge Cutoff
When training data ends
Neither model specifies a knowledge cutoff date.
Unable to compare the recency of their training data.
Provider Availability
Claude Fable 5.1 is available from Anthropic. Mercury 2 is available from Inception.
Claude Fable 5.1
Mercury 2
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Fable 5.1 and Mercury 2 side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Fable 5.1 vs Mercury 2.