ZMIME
Comparison · 2 models · Updated Oct 4, 2026

Claude Fable 5.1 vs GPT-6 Astra (Fast)

Too close to call on our weighted score (GPT-6 Astra (Fast) 36, Claude Fable 5.1 36). The right pick depends on what you value most.

  1. Anthropic

    Claude Fable 5.1

    Released Sep 1, 2026

    36/100
    • ECI164.8
    • Price$10.00 / $50.00
    • Context1M
    Full specs Remove Claude Fable 5.1

  2. OpenAI

    GPT-6 Astra (Fast)

    Released Sep 4, 2026

    36/100
    • ECI—
    • Price$20.00 / $100.00
    • Context1.05M
    Full specs Remove GPT-6 Astra (Fast)

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Too close to call

It is close. Our weighted score puts them within a point (GPT-6 Astra (Fast) 36/100, Claude Fable 5.1 36/100), so choose by what matters most for your work: Claude Fable 5.1 on price and GPT-6 Astra (Fast) for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

  • CapabilityNot enough dataNo independent benchmark covers every model here yet
  • Lowest priceClaude Fable 5.1Claude Fable 5.1 $20.00 · GPT-6 Astra (Fast) $40.00 per 1M tokens (3:1 blend)
  • Longest contextGPT-6 Astra (Fast)GPT-6 Astra (Fast) 1,050,000 · Claude Fable 5.1 1,000,000 tokens
  • Widest inputsSame inputsClaude Fable 5.1: Text, Images, PDFs · GPT-6 Astra (Fast): Text, Images, PDFs
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightClaude Fable 5.1GPT-6 Astra (Fast)
Price50%00
Inputs & features30%8080
Context window20%6061
Overall100%36/10036/100

Left out because at least one model lacks the data: capability. The remaining weights were rescaled.

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 GPT-6 Astra (Fast) specifications side by side
SpecificationClaude Fable 5.1AnthropicGPT-6 Astra (Fast)OpenAI
Capability
Capabilities Index (ECI)164.8—
ECI rank#4 of 148—
FrontierMath Tiers 1–3Research-level mathematics90.2%—
OTIS Mock AIME 2024–2025Competition mathematics100%—
SimpleQA VerifiedShort factual questions70.8%—
Price per million tokens
Input$10.00 (best)$20.00
Output$50.00 (best)$100.00
Cached input$0.25—
Blended (3:1)$20.00 (best)$40.00
Long-context rateSame rateSame rate
Price sourceOfficial Anthropic APIMedian of 1 providers
Limits
Context window1,000,000 tokens1,050,000 tokens (best)
Max output128,000 tokens128,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoNoNo
ReasoningYeslow · medium · high · xhigh · maxYes
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDclaude-fable-5-1—
API providers29 (best)1
ReleasedSep 1, 2026Sep 4, 2026
Knowledge cutoffJun 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
  • GPT-6 Astra (Fast)$400.00
04 — Questions

Which should you choose?

Which is better: Claude Fable 5.1 or GPT-6 Astra (Fast)?

It is close. Our weighted score puts them within a point (GPT-6 Astra (Fast) 36/100, Claude Fable 5.1 36/100), so choose by what matters most for your work: Claude Fable 5.1 on price and GPT-6 Astra (Fast) for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

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

Claude Fable 5.1 is cheaper at $10.00 input / $50.00 output per million tokens (official Anthropic API price). GPT-6 Astra (Fast) costs $20.00 input / $100.00 output per million tokens (median across 1 API provider). At a typical mix of three input tokens to one output token, that is $20.00 per million tokens for Claude Fable 5.1 versus $40.00 for GPT-6 Astra (Fast) (2× as much).

Which scores higher on benchmarks?

There is no independent benchmark that covers both models yet. Claude Fable 5.1 has an ECI of 164.8 and GPT-6 Astra (Fast) has not been scored yet.

Which is better for coding?

There are no published SWE-bench Verified results for Claude Fable 5.1 and GPT-6 Astra (Fast) yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.

Which has the bigger context window?

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

Which can read images, PDFs, audio or video?

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

Are any of these open source?

No. Claude Fable 5.1 and GPT-6 Astra (Fast) are proprietary and only available through APIs and apps.

Which is newer?

GPT-6 Astra (Fast) is the newest, released Sep 4, 2026. Claude Fable 5.1 came out Sep 1, 2026. Knowledge cutoff: Claude Fable 5.1 Jun 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

Related comparisons