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Head-to-head comparison

Claude Fable 5.1 vs GPT-6 Astra

Claude Fable 5.1 (Anthropic) and GPT-6 Astra (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 9 September 2026

As of 9 September 2026, GPT-6 Astra holds the stronger ModelCap Index position (#1 vs #3).

Which should you choose?

Choose Claude Fable 5.1 if…

  • you want provider choice — 4 listed API providers against 2.
  • LMArena Agent is your yardstick — 14.5% against 12.5%.
  • AA Intelligence Index is your yardstick — 53.4 against 52.8.
  • AA Terminal-Bench 2.1 is your yardstick — 91.4% against 88.4%.
  • AA Humanity's Last Exam is your yardstick — 59.1% against 54.7%.

Choose GPT-6 Astra if…

  • you want the stronger overall ModelCap Index position — #1 against #3 (93.7 vs 87.7 points).
  • ARC-AGI-2 is your yardstick — 95.0% against 90.0%.
  • Terminal-Bench 4.0 is your yardstick — 58.2% against 57.9%.
  • you want the more recently listed model — GPT-6 Astra was listed 4 September 2026, Claude Fable 5.1 1 September 2026.

Claude Fable 5.1 vs GPT-6 Astra: specs, pricing and context

Specification comparison of Claude Fable 5.1 and GPT-6 Astra
FieldClaude Fable 5.1AnthropicGPT-6 AstraOpenAI
ModelCap Index position#3#1
Index score87.793.7
EvidenceMeasuredMeasured
Input price / 1M tokens$10.00$10.00
Output price / 1M tokens$50.00$50.00
Context window1M tokens1M tokens
Max output tokens128K128K
API providers listed42
Weight accessAPI onlyAPI only
Input modalitiesText, Image, FileFile, Image, Text
First listed1 September 20264 September 2026
PublisherAnthropicOpenAI

Evidence: 5 public benchmark observations across 5 boards · 4 public benchmark observations across 4 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Fable 5.1 vs GPT-6 Astra

Public benchmark boards where Claude Fable 5.1 or GPT-6 Astra has a published result
BoardClaude Fable 5.1GPT-6 AstraLeads
Arena codingArena (LMArena)15171491–1542Max—Only one result
LMArena AgentLMArena14.5%12.6%–16.4%Max12.5%10.4%–14.7%MaxClaude Fable 5.1
ARC-AGI-2ARC Prize Foundation90.0%Max95.0%MaxGPT-6 Astra
ARC-AGI-3ARC Prize Foundation—62.7%MaxOnly one result
AA Intelligence IndexArtificial Analysis53.4intelligence-index:v4.3:reasoning-unspecified52.8intelligence-index:v4.3:maxClaude Fable 5.1
AA Terminal-Bench 2.1Artificial Analysis91.4%terminal-bench:2.1:terminus-2:e2b:pass-at-1:3-repeats:source-model="Claude Fable 5.1 (max with fallback)":reasoning=true88.4%terminal-bench:2.1:terminus-2:e2b:pass-at-1:3-repeats:source-model="GPT-6 Astra (max)":reasoning=trueClaude Fable 5.1
AA Humanity's Last ExamArtificial Analysis59.1%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="Claude Fable 5.1 (max with fallback)":reasoning=true54.7%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="GPT-6 Astra (max)":reasoning=trueClaude Fable 5.1
Terminal-Bench 4.0Terminal-Bench (Laude Institute)57.9%54.1%–61.6%Claude Code · Max58.2%55.4%–61.0%Codex · MaxGPT-6 Astra

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Claude Fable 5.1 vs GPT-6 Astra: common questions

Is Claude Fable 5.1 better than GPT-6 Astra?

GPT-6 Astra ranks higher on the ModelCap Index as of 9 September 2026: #1 against #3. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.

Is Claude Fable 5.1 cheaper than GPT-6 Astra?

Both list the same output price, $50.00/1M tokens, with input at $10.00/1M and $10.00/1M respectively. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $45.00 for Claude Fable 5.1 versus $45.00 for GPT-6 Astra. The listed-rate totals are equal. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.

Which has the bigger context window, Claude Fable 5.1 or GPT-6 Astra?

Both publish a 1M-token context window.

Which is better for coding, Claude Fable 5.1 or GPT-6 Astra?

AA Terminal-Bench 2.1: Claude Fable 5.1 91.4%, GPT-6 Astra 88.4% — Claude Fable 5.1 leads. Terminal-Bench 4.0: Claude Fable 5.1 57.9%, GPT-6 Astra 58.2% — GPT-6 Astra leads.

Are Claude Fable 5.1 and GPT-6 Astra open-weight models?

Claude Fable 5.1: API only. GPT-6 Astra: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run Claude Fable 5.1 and GPT-6 Astra?

ModelCap currently lists 4 API providers for Claude Fable 5.1 and 2 for GPT-6 Astra, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Fable 5.1 vs GPT-6 Astra comparison?

Every figure comes from the sealed ModelCap dataset published 9 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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