ZMIME
Comparison · 2 models · Updated Oct 4, 2026

Seed Evolving vs Step 5 Preview

Step 5 Preview comes out ahead, 57 to 50 on our weighted score, and it is the cheaper option too.

  1. ByteDance Seed

    Seed Evolving

    Released Jun 23, 2026

    50/100
    • ECI—
    • Price$0.891 / $4.45
    • Context256K
    Full specs Remove Seed Evolving
  2. Our pick

    StepFun

    Step 5 Preview

    Released Sep 16, 2026

    57/100
    • ECI—
    • Price$1.00 / $2.70
    • Context1M
    Full specs Remove Step 5 Preview

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Step 5 Preview is our pick

Step 5 Preview is the better all-round choice, scoring 57/100 against Seed Evolving (50). It leads on price 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 priceStep 5 PreviewStep 5 Preview $1.43 · Seed Evolving $1.78 per 1M tokens (3:1 blend)
  • Longest contextStep 5 PreviewStep 5 Preview 1,000,000 · Seed Evolving 256,000 tokens
  • Widest inputsSame inputsSeed Evolving: Text, Images, Video · Step 5 Preview: Text, Images, Video
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightSeed EvolvingStep 5 Preview
Price50%3843
Inputs & features30%8080
Context window20%3660
Overall100%50/10057/100

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.

Seed Evolving vs Step 5 Preview specifications side by side
SpecificationSeed EvolvingByteDance SeedStep 5 PreviewStepFun
Capability
Capabilities Index (ECI)——
ECI rank——
Price per million tokens
Input$0.891 (best)$1.00
Output$4.45$2.70 (best)
Cached input$0.178$0.05 (best)
Blended (3:1)$1.78$1.43 (best)
Long-context rateSame rateSame rate
Price sourceOfficial Volcengine Ark APIOfficial StepFun (Global) API
Limits
Context window256,000 tokens1,000,000 tokens (best)
Max output256,000 tokens1,000,000 tokens (best)
Inputs and features
TextYesYes
ImagesYesYes
PDFsNoNo
AudioNoNo
VideoYesYes
ReasoningYesminimal · low · medium · high · xhigh · maxYeslow · medium · high
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDdoubao-seed-evolvingstep-5-preview
API providers27 (best)
ReleasedJun 23, 2026Sep 16, 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.

  • Seed Evolving$17.81
  • Step 5 Preview$15.40
04 — Questions

Which should you choose?

Which is better: Seed Evolving or Step 5 Preview?

Step 5 Preview is the better all-round choice, scoring 57/100 against Seed Evolving (50). It leads on price 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, Seed Evolving or Step 5 Preview?

Step 5 Preview is cheaper at $1.00 input / $2.70 output per million tokens (official StepFun (Global) API price). Seed Evolving costs $0.891 input / $4.45 output per million tokens (official Volcengine Ark API price). At a typical mix of three input tokens to one output token, that is $1.43 per million tokens for Step 5 Preview versus $1.78 for Seed Evolving (1.2× as much).

Which scores higher on benchmarks?

There is no independent benchmark that covers both models yet. Seed Evolving has not been scored yet and Step 5 Preview has not been scored yet.

Which is better for coding?

There are no published SWE-bench Verified results for Seed Evolving and Step 5 Preview 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?

Step 5 Preview has the largest context window at 1,000,000 tokens, against 256,000 for Seed Evolving. Maximum output per response: Seed Evolving up to 256,000, Step 5 Preview up to 1,000,000 tokens.

Which can read images, PDFs, audio or video?

Seed Evolving accepts text, images and video; Step 5 Preview accepts text, images and video. They handle the same number of input types.

Are any of these open source?

No. Seed Evolving and Step 5 Preview are proprietary and only available through APIs and apps.

Which is newer?

Step 5 Preview is the newest, released Sep 16, 2026. Seed Evolving came out Jun 23, 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