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Comparison · 2 models · Updated Oct 4, 2026

GPT-6 Astra (Fast) vs Claude Mythos 5

Too close to call on our weighted score (GPT-6 Astra (Fast) 36, Claude Mythos 5 36). The right pick depends on what you value most.

  1. 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)

  2. Anthropic

    Claude Mythos 5

    Released Jun 9, 2026

    36/100
    • ECI—
    • Price$10.00 / $50.00
    • Context1M
    Full specs Remove Claude Mythos 5

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01 — Verdict

Too close to call

It is close. Our weighted score puts them within a point (GPT-6 Astra (Fast) 36/100, Claude Mythos 5 36/100), so choose by what matters most for your work: Claude Mythos 5 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 Mythos 5Claude Mythos 5 $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 Mythos 5 1,000,000 tokens
  • Widest inputsSame inputsGPT-6 Astra (Fast): Text, Images, PDFs · Claude Mythos 5: Text, Images, PDFs
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGPT-6 Astra (Fast)Claude Mythos 5
Price50%00
Inputs & features30%8080
Context window20%6160
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.

GPT-6 Astra (Fast) vs Claude Mythos 5 specifications side by side
SpecificationGPT-6 Astra (Fast)OpenAIClaude Mythos 5Anthropic
Capability
Capabilities Index (ECI)——
ECI rank——
Price per million tokens
Input$20.00$10.00 (best)
Output$100.00$50.00 (best)
Cached input——
Blended (3:1)$40.00$20.00 (best)
Long-context rateSame rateSame rate
Price sourceMedian of 1 providersMedian of 2 providers
Limits
Context window1,050,000 tokens (best)1,000,000 tokens
Max output128,000 tokens128,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoNoNo
ReasoningYesYes
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model ID——
API providers12 (best)
ReleasedSep 4, 2026Jun 9, 2026
Knowledge cutoff—Jan 31, 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.

  • GPT-6 Astra (Fast)$400.00
  • Claude Mythos 5$200.00
04 — Questions

Which should you choose?

Which is better: GPT-6 Astra (Fast) or Claude Mythos 5?

It is close. Our weighted score puts them within a point (GPT-6 Astra (Fast) 36/100, Claude Mythos 5 36/100), so choose by what matters most for your work: Claude Mythos 5 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, GPT-6 Astra (Fast) or Claude Mythos 5?

Claude Mythos 5 is cheaper at $10.00 input / $50.00 output per million tokens (median across 2 API providers). 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 Mythos 5 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. GPT-6 Astra (Fast) has not been scored yet and Claude Mythos 5 has not been scored yet.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-6 Astra (Fast) and Claude Mythos 5 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 Mythos 5. Maximum output per response: GPT-6 Astra (Fast) up to 128,000, Claude Mythos 5 up to 128,000 tokens.

Which can read images, PDFs, audio or video?

GPT-6 Astra (Fast) accepts text, images and PDFs; Claude Mythos 5 accepts text, images and PDFs. They handle the same number of input types.

Are any of these open source?

No. GPT-6 Astra (Fast) and Claude Mythos 5 are proprietary and only available through APIs and apps.

Which is newer?

GPT-6 Astra (Fast) is the newest, released Sep 4, 2026. Claude Mythos 5 came out Jun 9, 2026. Knowledge cutoff: Claude Mythos 5 Jan 31, 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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