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Comparison · 3 models · Updated Oct 4, 2026

Claude Fable 5.1 vs Claude Fable 5 vs GPT-6 Astra

Too close to call on our weighted score (GPT-6 Astra 68, Claude Fable 5.1 66, Claude Fable 5 65). The right pick depends on what you value most.

  1. Anthropic

    Claude Fable 5.1

    Released Sep 1, 2026

    66/100
    • ECI164.8
    • Price$10.00 / $50.00
    • Context1M
    Full specs Remove Claude Fable 5.1

  2. Anthropic

    Claude Fable 5

    Released Jun 9, 2026

    65/100
    • ECI162.2
    • Price$10.00 / $50.00
    • Context1M
    Full specs Remove Claude Fable 5

  3. OpenAI

    GPT-6 Astra

    Released Sep 4, 2026

    68/100
    • ECI166.5
    • Price$10.00 / $50.00
    • Context1.05M
    Full specs Remove GPT-6 Astra
01 — Verdict

Too close to call

It is close. Our weighted score puts them within 1 points (GPT-6 Astra 68/100, Claude Fable 5.1 66/100, Claude Fable 5 65/100), so choose by what matters most for your work: GPT-6 Astra for raw capability and Claude Fable 5.1 on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGPT-6 AstraCapabilities Index (ECI): GPT-6 Astra 166.5 · Claude Fable 5.1 164.8 · Claude Fable 5 162.2
  • Lowest priceSame priceClaude Fable 5.1 $20.00 · Claude Fable 5 $20.00 · GPT-6 Astra $20.00 per 1M tokens (3:1 blend)
  • Longest contextGPT-6 AstraGPT-6 Astra 1,050,000 · Claude Fable 5.1 1,000,000 · Claude Fable 5 1,000,000 tokens
  • Widest inputsSame inputsClaude Fable 5.1: Text, Images, PDFs · Claude Fable 5: Text, Images, PDFs · GPT-6 Astra: Text, Images, PDFs
  • Self-hostingNo open weightsAll three are available only through APIs
How the score is built
MeasureWeightClaude Fable 5.1Claude Fable 5GPT-6 Astra
CapabilityCapabilities Index (ECI)50%979499
Price25%000
Inputs & features15%808080
Context window10%606061
Overall100%66/10065/10068/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

Claude Fable 5.1 vs Claude Fable 5 vs GPT-6 Astra specifications side by side
SpecificationClaude Fable 5.1AnthropicClaude Fable 5AnthropicGPT-6 AstraOpenAI
Capability
Capabilities Index (ECI)164.8162.2166.5 (best)
ECI rank#4 of 148#7 of 148#2 of 148 (best)
GPQA DiamondGraduate-level science questions—85.9%95.8% (best)
FrontierMath Tiers 1–3Research-level mathematics90.2%87.0%93.7% (best)
OTIS Mock AIME 2024–2025Competition mathematics100%100%100%
SimpleQA VerifiedShort factual questions70.8%70.7%75.6% (best)
Price per million tokens
Input$10.00$10.00$10.00
Output$50.00$50.00$50.00
Cached input$0.25 (best)$1.00$1.00
Blended (3:1)$20.00$20.00$20.00
Long-context rateSame rateSame rateOver 272K: $20.00 / $75.00
Price sourceOfficial Anthropic APIOfficial Anthropic APIOfficial OpenAI API
Limits
Context window1,000,000 tokens1,000,000 tokens1,050,000 tokens (best)
Max output128,000 tokens128,000 tokens128,000 tokens
Inputs and features
TextYesYesYes
ImagesYesYesYes
PDFsYesYesYes
AudioNoNoNo
VideoNoNoNo
ReasoningYeslow · medium · high · xhigh · maxYeslow · medium · high · xhigh · maxYeslow · medium · high · xhigh · max
Tool callingYesYesYes
Structured outputYesYesYes
Availability
WeightsProprietaryProprietaryProprietary
API model IDclaude-fable-5-1claude-fable-5gpt-6-astra
API providers2938 (best)26
ReleasedSep 1, 2026Jun 9, 2026Sep 4, 2026
Knowledge cutoffJun 2026Jan 31, 2026Apr 30, 2026
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • Claude Fable 5.1$200.00
  • Claude Fable 5$200.00
  • GPT-6 Astra$200.00
04 — Questions

Which should you choose?

Which is better: Claude Fable 5.1, Claude Fable 5 or GPT-6 Astra?

It is close. Our weighted score puts them within 1 points (GPT-6 Astra 68/100, Claude Fable 5.1 66/100, Claude Fable 5 65/100), so choose by what matters most for your work: GPT-6 Astra for raw capability and Claude Fable 5.1 on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Fable 5.1, Claude Fable 5 or GPT-6 Astra?

Claude Fable 5.1, Claude Fable 5 and GPT-6 Astra cost the same: $10.00 input / $50.00 output per million tokens.

Which scores higher on benchmarks?

GPT-6 Astra scores higher on the Capabilities Index (ECI): GPT-6 Astra 166.5 (#2 of 148), Claude Fable 5.1 164.8 (#4 of 148) and Claude Fable 5 162.2 (#7 of 148). The confidence ranges of the top two overlap (163.1–171.1 vs 161.8–169.1), so treat the gap as small. On individual benchmarks: FrontierMath Tiers 1–3 — GPT-6 Astra 93.7%, Claude Fable 5.1 90.2%, Claude Fable 5 87.0%; OTIS Mock AIME 2024–2025 — Claude Fable 5.1 100%, Claude Fable 5 100%, GPT-6 Astra 100%; SimpleQA Verified — GPT-6 Astra 75.6%, Claude Fable 5.1 70.8%, Claude Fable 5 70.7%.

Which is better for coding?

There are no published SWE-bench Verified results for Claude Fable 5.1, Claude Fable 5 and GPT-6 Astra yet, so there is no like-for-like coding score. On overall capability, GPT-6 Astra leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.

Which has the bigger context window?

GPT-6 Astra has the largest context window at 1,050,000 tokens, against 1,000,000 for Claude Fable 5.1 and 1,000,000 for Claude Fable 5. Maximum output per response: Claude Fable 5.1 up to 128,000, Claude Fable 5 up to 128,000, GPT-6 Astra up to 128,000 tokens.

Which can read images, PDFs, audio or video?

Claude Fable 5.1 accepts text, images and PDFs; Claude Fable 5 accepts text, images and PDFs; GPT-6 Astra accepts text, images and PDFs. They handle the same number of input types.

Are any of these open source?

No. Claude Fable 5.1, Claude Fable 5 and GPT-6 Astra are proprietary and only available through APIs and apps.

Which is newer?

GPT-6 Astra is the newest, released Sep 4, 2026. Claude Fable 5.1 came out Sep 1, 2026; Claude Fable 5 came out Jun 9, 2026. Knowledge cutoff: Claude Fable 5.1 Jun 2026, Claude Fable 5 Jan 31, 2026, GPT-6 Astra Apr 30, 2026.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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