Claude Fable 5.1 vs GPT-6 Astra (2026): Which AI Model Is Better?

Both are popular language models. Here is how Claude Fable 5.1 and GPT-6 Astra stack up on price, strengths and weaknesses, and which one we would pick.

Claude Fable 5.1

Anthropic's Claude models (Fable 5.1, Opus 5.5, Sonnet 5, Haiku 4.5) with 1M-token context

9.0 /10

Pricing: Free plan, paid from $20/mo

Pros

1M-token context window on Fable 5.1, Opus 5.5 and Sonnet 5
Up to 128K output tokens per request, useful for long drafts and chapters
Opus 5.5 is billed at $4 / $20 per million tokens, well below Fable 5.1
Available on the Claude API, Amazon Bedrock, Google Cloud and Microsoft Foundry

Cons

Fable 5.1 costs $10 input / $50 output per million tokens
Free Claude plan only includes Sonnet and Haiku
No native image generation; text and image input only
Pro and Max users get only part of their weekly limits on Fable

Visit Claude Fable 5.1 ↗

GPT-6 Astra

OpenAI's GPT-6 family (Astra, Sol, Luna) behind ChatGPT and the OpenAI API

9.0 /10

Pricing: Free plan, paid from $8/mo

Pros

Three tiers let you trade quality for cost: Astra, Sol and Luna
GPT-6 Sol and Luna API prices are half of the GPT-5.6 equivalents
Same model family powers ChatGPT, so drafts and API output behave alike
Wide third-party support in automation tools such as n8n, Make and Zapier

Cons

GPT-6 Astra is expensive on the API at $10 in / $50 out per million tokens
Sol is limited to paid ChatGPT plans; free users get Luna
Closed weights: you cannot self-host or fine-tune locally
Fast release cadence means prompts and outputs shift every few months

Visit GPT-6 Astra ↗

Claude Fable 5.1 vs GPT-6 Astra at a glance

	Claude Fable 5.1	GPT-6 Astra
Editor score	9.0 / 10	9.0 / 10
Pricing model	Freemium	Freemium
Starting price	$20/mo	$8/mo
Reader upvotes	0	0
Best for	llm, anthropic, claude	llm, openai, chatgpt
Makes	Blog posts & articles, Ad & marketing copy, Emails & newsletters, Scripts & outlines	Blog posts & articles, Ad & marketing copy, Emails & newsletters, Scripts & outlines
Maker	Anthropic	OpenAI
Latest release	2026-09	2026-09
Apps offering it	15	17

Our pick

Claude Fable 5.1 edges it with a score of 9.0 versus 9.0. Claude Fable 5.1 is the better fit if you value: 1m-token context window on fable 5.1, opus 5.5 and sonnet 5, up to 128k output tokens per request, useful for long drafts and chapters. Choose GPT-6 Astra instead if you need: three tiers let you trade quality for cost: astra, sol and luna, gpt-6 sol and luna api prices are half of the gpt-5.6 equivalents.