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Model comparison

Mistral Medium 3.5 vs Step 5 Preview

Mistral against StepFun, compared on context, price, and verified benchmark results.

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

Mistral

Mistral Medium 3.5

Frontier · Open weights

vs

StepFun

Step 5 Preview

Frontier

AI model capability comparison
SpecificationMistral Medium 3.5Step 5 Preview
ProviderMistralStepFun
TierFrontierFrontier
Context window262KWinner: 1M
Max outputNot verifiedUnverifiedNot verifiedUnverified
Input / 1M tokens$1.50Winner: $1
Output / 1M tokens$7.50Winner: $2.70
WeightsOpenClosed
Parameters128B dense600B total / 27B active MoE (StepFun)
Reasoning levelsNot verifiedUnverifiedNot verifiedUnverified
Modalitiestext, imagetext, image
LicenseModified MITNot disclosedUnverified
API model idmistral-medium-3-5step-5-preview
ReleasedApril 28, 2026September 18, 2026
Artificial Analysis Intelligence Index (2026-09-26)14.2Winner: 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

Mistral Medium 3.5: Mistral first-party API $1.50/$7.50 per MTok; Mistral advertises up to 90% off cached input (exact cached rate not verified). Open weights under a Modified MIT licence. 128B dense.

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).

FrontierOpen weightsRecord checked September 26, 2026

Mistral Medium 3.5

Mistral Medium 3.5 is the model Mistral calls its new flagship — a 128B dense open-weight model with a 256K context, powering its Vibe remote agents.

Best for

  • EU-hosted frontier work
  • Open-weight self-hosting
  • Mistral Vibe agents

Watch out

Far behind US and Chinese frontier models on the Artificial Analysis index; max output is not published. Check the Modified MIT terms before redistribution.

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 5 Preview is cheaper on output at $2.70 per million tokens against $7.50 for Mistral Medium 3.5 — about 2.8×. 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? Mistral Medium 3.5 · Step 5 Preview

Common questions

Mistral Medium 3.5 vs Step 5 Preview

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

Is Mistral Medium 3.5 or Step 5 Preview cheaper for input?
Step 5 Preview is cheaper at $1 per million input tokens, against $1.50 for Mistral Medium 3.5 — roughly 1.5× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Mistral Medium 3.5 has tiered pricing: Mistral first-party API $1.50/$7.50 per MTok; Mistral advertises up to 90% off cached input (exact cached rate not verified). Open weights under a Modified MIT licence. 128B dense. 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 Mistral Medium 3.5 or Step 5 Preview cheaper for output?
Step 5 Preview is cheaper at $2.70 per million output tokens, against $7.50 for Mistral Medium 3.5 — roughly 2.8× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Mistral Medium 3.5 has tiered pricing: Mistral first-party API $1.50/$7.50 per MTok; Mistral advertises up to 90% off cached input (exact cached rate not verified). Open weights under a Modified MIT licence. 128B dense. 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, Mistral Medium 3.5 or Step 5 Preview?
Step 5 Preview accepts 1M tokens against 262K for Mistral Medium 3.5. This only matters if you routinely send very long documents or large codebases.
Should I use Mistral Medium 3.5 or Step 5 Preview?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Mistral Medium 3.5 suits eu-hosted frontier work; Step 5 Preview suits long-context work on a budget.
Can I self-host Mistral Medium 3.5 or Step 5 Preview?
Mistral Medium 3.5 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 5 Preview costs $1 per 1M tokens versus $1.50 for Mistral Medium 3.5 — a 1.5x difference at the headline tier.
  • Context: Step 5 Preview takes 1M against 262K for Mistral Medium 3.5 — only decisive if your prompts approach the smaller window.
  • Measured capability: Step 5 Preview leads Artificial Analysis Intelligence Index 43.7 to 14.2 (measured 2026-09-26).
  • Deployment: Mistral Medium 3.5 publishes weights you can self-host; the other is API-only.
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