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Comparison · 2 models · Updated Nov 2, 2026

GPT-6 Astra (Fast) vs Mercury 2.5

Mercury 2.5 comes out ahead, 55 to 33 on our weighted score, and it is the cheaper option too.

  1. OpenAI

    GPT-6 Astra (Fast)

    Released Sep 4, 2026New

    33/100
    • ECI—
    • Price$20.00 / $100.00
    • Context1.05M
    Full specs Remove GPT-6 Astra (Fast)
  2. Our pick

    Inception

    Mercury 2.5

    Released Sep 8, 2026New

    55/100
    • ECI—
    • Price$0.20 / $0.75
    • Context260K
    Full specs Remove Mercury 2.5

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Mercury 2.5 is our pick

Mercury 2.5 is the better all-round choice, scoring 55/100 against GPT-6 Astra (Fast) (33). It leads on price. GPT-6 Astra (Fast) wins on inputs & features and context window. 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 priceMercury 2.5Mercury 2.5 $0.338 · GPT-6 Astra (Fast) $40.00 per 1M tokens (3:1 blend)
  • Longest contextGPT-6 Astra (Fast)GPT-6 Astra (Fast) 1,050,000 · Mercury 2.5 260,000 tokens
  • Widest inputsGPT-6 Astra (Fast)GPT-6 Astra (Fast): Text, Images, PDFs · Mercury 2.5: Text
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGPT-6 Astra (Fast)Mercury 2.5
Price50%069
Inputs & features30%7045
Context window20%6136
Overall100%33/10055/100

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 Mercury 2.5 specifications side by side
SpecificationGPT-6 Astra (Fast)OpenAIMercury 2.5Inception
Capability
Capabilities Index (ECI)——
ECI rank——
Price per million tokens
Input$20.00$0.20 (best)
Output$100.00$0.75 (best)
Cached input—$0.02
Blended (3:1)$40.00$0.338 (best)
Long-context rateSame rateSame rate
Price sourceMedian of 1 providersOfficial Inception API
Limits
Context window1,050,000 tokens (best)260,000 tokens
Max output128,000 tokens (best)65,536 tokens
Inputs and features
TextYesYes
ImagesYesNo
PDFsYesNo
AudioNoNo
VideoNoNo
ReasoningYesYeslow · medium · high
Tool callingYesYes
Structured outputNoYes
Availability
WeightsProprietaryProprietary
API model ID—mercury-2.5
API providers16 (best)
ReleasedSep 4, 2026Sep 8, 2026
Knowledge cutoff——
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
  • Mercury 2.5$3.50
04 — Questions

Which should you choose?

Which is better: GPT-6 Astra (Fast) or Mercury 2.5?

Mercury 2.5 is the better all-round choice, scoring 55/100 against GPT-6 Astra (Fast) (33). It leads on price. GPT-6 Astra (Fast) wins on inputs & features and context window. 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 Mercury 2.5?

Mercury 2.5 is cheaper at $0.20 input / $0.75 output per million tokens (official Inception 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 $0.338 per million tokens for Mercury 2.5 versus $40.00 for GPT-6 Astra (Fast) (119× 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 Mercury 2.5 has not been scored yet.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-6 Astra (Fast) and Mercury 2.5 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 260,000 for Mercury 2.5. Maximum output per response: GPT-6 Astra (Fast) up to 128,000, Mercury 2.5 up to 65,536 tokens.

Which can read images, PDFs, audio or video?

GPT-6 Astra (Fast) accepts text, images and PDFs; Mercury 2.5 accepts text. GPT-6 Astra (Fast) handles the widest range of inputs.

Are any of these open source?

No. GPT-6 Astra (Fast) and Mercury 2.5 are proprietary and only available through APIs and apps.

Which is newer?

Mercury 2.5 is the newest, released Sep 8, 2026. GPT-6 Astra (Fast) came out Sep 4, 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 Nov 2, 2026.

05 — Keep comparing

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