Claude Fable 5.1 vs Mercury 3
Claude Fable 5.1 leads the LLM Stats Score 53.2 to 36.1. Mercury 3 is 123.1x cheaper per token.
Anthropic · Inception · Updated for 2026
Which is better?
Claude Fable 5.1 leads the overall LLM Stats Score 53.2 to 36.1, ranking #9 overall.
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, Mercury 3 is roughly 123.1x 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
- overall performance matters — it scores 53.2 and ranks #9 on LLM Stats
- your work emphasizes reasoning and agents — it leads those capability indexes
- you value its reported benchmark strengths — it wins 1 of 1 exact shared results
Choose Mercury 3
- cost matters — it's about 123.1x cheaper per token
- you want the most recent training data — it shipped Oct 2026
At a glance
The differences that matter most.
Individual benchmarks
7 reported for Claude Fable 5.1 · 12 for Mercury 3
Claude Fable 5.1 outperforms in 1 benchmarks (GDPval-AA), while Mercury 3 is better at 0 benchmarks.
Claude Fable 5.1 significantly outperforms across most benchmarks.
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 100.0x more expensive than Mercury 3 ($0.10/1M tokens).
For output processing, Claude Fable 5.1 ($50.00/1M tokens) is 142.9x more expensive than Mercury 3 ($0.35/1M tokens).
In conclusion, Claude Fable 5.1 is more expensive than Mercury 3.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Both models have the same input context window of 1,000,000 tokens. Mercury 3 can generate longer responses up to 131,072 tokens, while Claude Fable 5.1 is limited to 128,000 tokens.
Input capabilities
Documented input modalities across available providers
Claude Fable 5.1 supports multimodal inputs, whereas Mercury 3 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 3
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 3 was released on 2026-10-19.
Mercury 3 is 2 months newer than Claude Fable 5.1.
Sep 1, 2026
1 months ago
Oct 19, 2026
3 days ago
1mo newerKnowledge 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 3 is available from Inception.
Claude Fable 5.1
Mercury 3
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Fable 5.1 and Mercury 3 side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Fable 5.1 vs Mercury 3.