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Hermann Yakushev
Hermann Yakushev

Posted on Originally published at llmpodium.com

GPT-6 Astra vs Claude Fable 5.1: Head-to-Head Benchmarks, Arena Elo & Pricing

#ai #openai #anthropic #benchmarks

This benchmark showdown was originally published on LLMPodium — the premier independent AI model evaluation leaderboard tracking 700+ LLMs.

Executive Summary

The late 2026 frontier AI race has culminated in a direct showdown between OpenAI GPT-6 Astra and Anthropic Claude Fable 5.1. Both models represent the state-of-the-art in autonomous agentic workflows, long-context repository refactoring, and formal mathematical reasoning.

Here is how they compare across verified LMSYS Chatbot Arena Elo, SWE-bench Pro, FrontierMath, and real-world token economics.

1. Head-to-Head Scorecard

Metric OpenAI GPT-6 Astra Anthropic Claude Fable 5.1 Advantage
LLMPodium Overall Rank #3 (Score 86.2) #2 (Score 88.4) Claude Fable (+2.2)
LMSYS Arena Elo 1498 1512 Claude Fable (+14 Elo)
SWE-bench Pro (Verified) 67.0% 65.0% GPT-6 Astra (+2.0%)
FrontierMath (Tier 4) 97.6% 94.2% GPT-6 Astra (+3.4%)
Humanity's Last Exam (HLE) 53.2% 65.0% Claude Fable (+11.8%)
Context Window 1,100,000 tokens 500,000 tokens GPT-6 Astra (2.2x)
Max Output Tokens 128,000 tokens 64,000 tokens GPT-6 Astra (2x)
Input Token Price / 1M $10.00 $10.00 Tie
Output Token Price / 1M $50.00 $50.00 Tie

2. Strengths & Engineering Tradeoffs

When to Choose GPT-6 Astra:

  1. Massive Codebases & Context: Astra's 1.1M active context window allows ingesting entire production enterprise repositories in a single reasoning pass without loss of needle-in-a-haystack recall.
  2. Formal Proofs & Math: Scoring 97.6% on FrontierMath Tier 4, Astra leads the world in autonomous theorem proving and formal verification.
  3. Cybersecurity Hardening: Certified Critical-tier rating under the Preparedness Framework prevents exploit code leakage.

When to Choose Claude Fable 5.1:

  1. Nuanced System Prompt Adherence: Claude Fable continues Anthropic's dominance in complex multi-persona orchestration and high-touch instruction following.
  2. Abstract Reasoning (HLE): Claude Fable's 65.0% on Humanity's Last Exam demonstrates superior generalization across interdisciplinary research domains.
  3. Conversational Coherence: Currently holding the #2 spot on LMSYS Arena Elo with 1512 points.

🔗 Live Scorecards & Token Pricing

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