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Model comparison

Step 3.7 Flash vs Step 5 Preview

Two StepFun tiers compared on the figures that decide which one a workload actually needs.

Catalog record checked September 26, 2026Individual provider fields may changeEvidence confidence: High — see receipts below

StepFun

Step 3.7 Flash

Budget · Open weights

vs

StepFun

Step 5 Preview

Frontier

AI model capability comparison
SpecificationStep 3.7 FlashStep 5 Preview
ProviderStepFunStepFun
TierBudgetFrontier
Context window256KWinner: 1M
Max outputNot verifiedUnverifiedNot verifiedUnverified
Input / 1M tokensWinner: $0.20$1
Output / 1M tokensWinner: $1.15$2.70
WeightsOpenClosed
Parameters198B total / 11B active (sparse MoE VLM)600B total / 27B active MoE (StepFun)
Reasoning levelslow, medium, highNot verifiedUnverified
Modalitiestext, image, videotext, image
LicenseApache 2.0Not disclosedUnverified
API model idstep-3.7-flashstep-5-preview
ReleasedMay 29, 2026September 18, 2026
Artificial Analysis Intelligence Index (2026-09-26)19.5Winner: 43.7

Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

Where each score comes from, and how far it can be compared across models.

  • 2026-09-26
    Artificial Analysis

    Composite index blending reasoning, knowledge, and coding evals into one 0–100 score.

    Comparable with caveatOnly same-version scores are comparable. v4.3.2 was rebaselined (the top score fell from 66 on v4.1.1 to ~58), so v4.1.1 figures must not be compared with v4.3.2 figures — check measuredAt.

Pricing tiers

Step 3.7 Flash: $0.20/$1.15 per MTok on the StepFun platform (cache hit $0.04); open weights (Apache 2.0) on Hugging Face.

Step 5 Preview: $1.00/$2.70 per MTok on the StepFun platform (cache-hit input $0.05); StepFun lists it under Multimodal Reasoning Models and says output tokens include reasoning. No max-output figure is published. StepFun says open weights follow on 2026-10-15. Release date per Artificial Analysis's listing (StepFun's launch page is undated).

BudgetOpen weightsRecord checked September 26, 2026

Step 3.7 Flash

Step 3.7 Flash is StepFun's efficient open-weight (Apache 2.0) sparse-MoE VLM for high-volume multimodal work.

Best for

  • High-volume multimodal
  • Cost-sensitive API
  • Chinese market

Watch out

No longer StepFun's newest model (Step 5 Preview launched in September 2026); verify hosted pricing and availability.

FrontierRecord checked September 26, 2026

Step 5 Preview

Step 5 Preview is StepFun's new frontier reasoning model — a 1M-context, vision-input API preview that lands near Kimi K3 and GLM 5.3 on the Artificial Analysis index at a lower price.

Best for

  • Long-context work on a budget
  • Chinese + English
  • Early testing before the open-weight drop

Watch out

Preview: weights are promised for 2026-10-15 but not yet released, and its max output is unpublished and the launch benchmarks are vendor-run.

When the cheaper one wins

Step 3.7 Flash is cheaper on output at $1.15 per million tokens against $2.70 for Step 5 Preview — about 2.3×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.

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Evidence confidence: High

How strong and complete the evidence behind this comparison is — not a prediction of which model is better.

  • Pricing verified on both sides — Input and output rates are verified for both models.
  • 3/5 core specs verified on both sides — Not published for at least one side: max output, reasoning levels.
  • 1 shared named benchmark with differing scores — Measured on: Artificial Analysis Intelligence Index.
  • Verified within the last 90 days — Newest catalog check was 2 days ago.
  • Both models carry source citations — Each side has at least two catalog sources on record.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

Related comparisons

Diving deeper on one model? Step 3.7 Flash · Step 5 Preview

Common questions

Step 3.7 Flash vs Step 5 Preview

Answered from the verified figures on this page rather than general guidance.

Is Step 3.7 Flash or Step 5 Preview cheaper for input?
Step 3.7 Flash is cheaper at $0.20 per million input tokens, against $1 for Step 5 Preview — roughly 5.0× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Step 3.7 Flash has tiered pricing: $0.20/$1.15 per MTok on the StepFun platform (cache hit $0.04); open weights (Apache 2.0) on Hugging Face. Step 5 Preview has tiered pricing: $1.00/$2.70 per MTok on the StepFun platform (cache-hit input $0.05); StepFun lists it under Multimodal Reasoning Models and says output tokens include reasoning. No max-output figure is published. StepFun says open weights follow on 2026-10-15. Release date per Artificial Analysis's listing (StepFun's launch page is undated).
Is Step 3.7 Flash or Step 5 Preview cheaper for output?
Step 3.7 Flash is cheaper at $1.15 per million output tokens, against $2.70 for Step 5 Preview — roughly 2.3× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Step 3.7 Flash has tiered pricing: $0.20/$1.15 per MTok on the StepFun platform (cache hit $0.04); open weights (Apache 2.0) on Hugging Face. Step 5 Preview has tiered pricing: $1.00/$2.70 per MTok on the StepFun platform (cache-hit input $0.05); StepFun lists it under Multimodal Reasoning Models and says output tokens include reasoning. No max-output figure is published. StepFun says open weights follow on 2026-10-15. Release date per Artificial Analysis's listing (StepFun's launch page is undated).
Which has the larger context window, Step 3.7 Flash or Step 5 Preview?
Step 5 Preview accepts 1M tokens against 256K for Step 3.7 Flash. This only matters if you routinely send very long documents or large codebases.
Should I use Step 3.7 Flash or Step 5 Preview?
Step 3.7 Flash is the budget tier and Step 5 Preview the frontier tier. The useful question is whether your hardest task actually fails on the cheaper one — most production volume such as classification, extraction and summarisation does not.
Can I self-host Step 3.7 Flash or Step 5 Preview?
Step 3.7 Flash publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. Step 5 Preview is a closed model whose supported access paths are controlled by its provider.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

  • Input price: Step 3.7 Flash costs $0.20 per 1M tokens versus $1 for Step 5 Preview — a 5x difference at the headline tier.
  • Context: Step 5 Preview takes 1M against 256K for Step 3.7 Flash — only decisive if your prompts approach the smaller window.
  • Deployment: Step 3.7 Flash publishes weights you can self-host; the other is API-only.
  • Positioning: Step 3.7 Flash sits in the budget tier, Step 5 Preview in the frontier tier — most production volume (classification, extraction, summarisation) does not need the pricier tier.
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