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Claude Fable 5.1 vs GPT-6 Astra

Claude Fable 5.1 and GPT-6 Astra: current price, context, max output, and supported operations.

Which one to choose

Pick Claude Fable 5.1 for long-horizon agent runs that need sustained reasoning and where you want adaptive thinking always on; pick GPT-6 Astra for hard coding, research and document work that involves operating software, with a reasoning effort you set per request. These are each maker's top model, so test on your hardest tasks. Neither is the right default for routine, latency-sensitive traffic.

Pricing comparison

Claude Fable 5.1GPT-6 Astra
Model makerAnthropicOpenAI
Delivery availabilityAvailableAvailable
Context window1M1.05M
Max output128K128K
Official price
Input$10.00per 1M tokensOutput$50.00per 1M tokens
Input$10.00per 1M tokensOutput$50.00per 1M tokens
TokenLab price
Input$3.00per 1M tokensOutput$15.00per 1M tokens
Input$3.00per 1M tokensOutput$15.00per 1M tokens
Model performance
30-day success rate
64.2%
7-day median latency
29.8 sn=362
30-day success rate
33.0%
7-day median latency
15.9 sn=439
Capabilities
JSON modePrompt CacheReasoningTool useVision
CodeJSON modePrompt CacheReasoningTool useVision

Choose Claude Fable 5.1 when

  • Your agent runs for many steps and must keep a plan and earlier decisions in view.
  • You want reasoning to be adaptive and on by default, without choosing a level each call.
  • Your work stays clear of exploit generation and restricted biology, which Anthropic's safeguards still block.

Choose GPT-6 Astra when

  • You want to set reasoning effort yourself, from low up to max, depending on the request.
  • The job has the model fill online forms, update CRM records or run front-end checks.
  • You need research, spreadsheets or documents drafted alongside code in one model.

How they differ

AspectClaude Fable 5.1GPT-6 Astra
Role in the lineupAnthropic's top Claude model of September 2026, the slowest tier, built for demanding reasoning.OpenAI's most capable GPT-6 model, with Sol and Luna as cheaper descendants.
Reasoning controlAdaptive thinking is always on with a high default effort.Reasoning effort is selectable from low to max, the widest range in GPT-6.
SafeguardsClassifiers block exploit generation and restrict some biology work, which can interrupt legitimate security research.OpenAI presents it as its most aligned model, with better handling of user intent and boundaries.
Computer and software usePositioned for long agent runs, and Anthropic reports results on terminal and editor-based coding benchmarks.OpenAI reports leading results on computer use and browsing, and names form filling and CRM updates as examples.
LatencyLatency-sensitive chat is better served by Sonnet 5.5 or Haiku 4.5.High effort lengthens responses; a smaller GPT-6 model fits latency-sensitive chat.

Summary

  • Claude Fable 5.1: Input $3.00 / Output $15.00 per 1M tokens; GPT-6 Astra: Input $3.00 / Output $15.00 per 1M tokens. Rates depend on the billing unit, specification, and usage. Compare matching conditions in the model's detailed pricing; a single rate does not determine the total cost.
Claude Fable 5.1
Claude 5
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GPT-6 Astra
GPT-6
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FAQ

Is Claude Fable 5.1 better than GPT-6 Astra?

Neither maker positions its model as a replacement for the other. Fable 5.1 is Anthropic's top tier for long reasoning-heavy agent runs; Astra is OpenAI's top tier for the hardest coding, research and computer-use work. Compare them on your own hardest tasks.

Should I use either as my default model?

Usually not. Anthropic suggests starting with Opus 5.5 and moving to Fable 5.1 only when your evaluations still fall short. OpenAI points to Sol and Luna for much of Astra's behavior at lower cost. Reserve both for the hardest work.

Do they differ in how thinking is controlled?

Yes. Fable 5.1 runs adaptive thinking that is always on with a high default effort. Astra lets you choose effort per request from low to max, so you can match depth to each task.

Can I use both in one system?

Yes. A common split is routing hard planning or long-horizon turns to one and computer-use or document steps to the other, then comparing results on your evaluation set. Smaller models can handle the routine traffic around them.

Which is cheaper, Claude Fable 5.1 or GPT-6 Astra?

Claude Fable 5.1: Input $3.00 / Output $15.00 per 1M tokens; GPT-6 Astra: Input $3.00 / Output $15.00 per 1M tokens. Rates depend on the billing unit, specification, and usage. Compare matching conditions in the model's detailed pricing; a single rate does not determine the total cost.

What are the key differences between Claude Fable 5.1 and GPT-6 Astra?

GPT-6 Astra: Code

Sources

Reviewed Oct 2, 2026