Claude Fable 5.1 vs Grok 4 Fast
Claude Fable 5.1 leads the LLM Stats Score 56.8 to 32.0. Grok 4 Fast is 72.7x cheaper per token.
Anthropic · xAI · Updated for 2026
Which is better?
Claude Fable 5.1 leads the overall LLM Stats Score 56.8 to 32.0, ranking #2 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, Grok 4 Fast is roughly 72.7x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Grok 4 Fast also accepts a larger context window (2,000,000 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 value its reported benchmark strengths — it wins 1 of 1 exact shared results
- you want the most recent training data — it shipped Sep 2026
Choose Grok 4 Fast
- cost matters — it's about 72.7x cheaper per token
- you process long inputs — it offers a 2,000,000 token context window
At a glance
The differences that matter most.
Individual benchmarks
7 reported for Claude Fable 5.1 · 7 for Grok 4 Fast
Claude Fable 5.1 outperforms in 1 benchmarks (Humanity's Last Exam), while Grok 4 Fast 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 50.0x more expensive than Grok 4 Fast ($0.20/1M tokens).
For output processing, Claude Fable 5.1 ($50.00/1M tokens) is 100.0x more expensive than Grok 4 Fast ($0.50/1M tokens).
In conclusion, Claude Fable 5.1 is more expensive than Grok 4 Fast.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Grok 4 Fast accepts 2,000,000 input tokens compared to Claude Fable 5.1's 1,000,000 tokens. Claude Fable 5.1 can generate longer responses up to 128,000 tokens, while Grok 4 Fast is limited to 30,000 tokens.
Input capabilities
Documented input modalities across available providers
Both Claude Fable 5.1 and Grok 4 Fast support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Fable 5.1
Grok 4 Fast
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 Grok 4 Fast was released on 2025-08-28.
Claude Fable 5.1 is 12 months newer than Grok 4 Fast.
Sep 1, 2026
3 days ago
1.0yr newerAug 28, 2025
1.0 years 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. Grok 4 Fast is available from xAI.
Claude Fable 5.1
Grok 4 Fast
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Fable 5.1 and Grok 4 Fast side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Fable 5.1 vs Grok 4 Fast.