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Comparison · 2 models · Updated Oct 4, 2026

Step 3.5 Flash vs Grok 4.1 Fast

Grok 4.1 Fast comes out ahead, 71 to 62 on our weighted score, though Step 3.5 Flash is 45% cheaper per token.

  1. StepFun

    Step 3.5 Flash

    Released Jan 29, 2026

    62/100
    • ECI—
    • Price$0.10 / $0.30
    • Context256K
    Full specs Remove Step 3.5 Flash
  2. Our pick

    xAI

    Grok 4.1 Fast

    Released Nov 19, 2025

    71/100
    • ECI—
    • Price$0.20 / $0.50
    • Context2M
    Full specs Remove Grok 4.1 Fast

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Grok 4.1 Fast is our pick

Grok 4.1 Fast is the better all-round choice, scoring 71/100 against Step 3.5 Flash (62). It leads on inputs & features and context window. Step 3.5 Flash wins on price. 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 3.5 FlashStep 3.5 Flash $0.15 · Grok 4.1 Fast $0.275 per 1M tokens (3:1 blend)
  • Longest contextGrok 4.1 FastGrok 4.1 Fast 2,000,000 · Step 3.5 Flash 256,000 tokens
  • Widest inputsGrok 4.1 FastStep 3.5 Flash: Text · Grok 4.1 Fast: Text, Images
  • Self-hostingStep 3.5 FlashPublishes downloadable weights
How the score is built
MeasureWeightStep 3.5 FlashGrok 4.1 Fast
Price50%8976
Inputs & features30%3560
Context window20%3672
Overall100%62/10071/100

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.

Step 3.5 Flash vs Grok 4.1 Fast specifications side by side
SpecificationStep 3.5 FlashStepFunGrok 4.1 FastxAI
Capability
Capabilities Index (ECI)——
ECI rank——
Price per million tokens
Input$0.10 (best)$0.20
Output$0.30 (best)$0.50
Cached input$0.02—
Blended (3:1)$0.15 (best)$0.275
Long-context rateSame rateSame rate
Price sourceOfficial StepFun (Global) APIMedian of 2 providers
Limits
Context window256,000 tokens2,000,000 tokens (best)
Max output256,000 tokens (best)30,000 tokens
Inputs and features
TextYesYes
ImagesNoYes
PDFsNoNo
AudioNoNo
VideoNoNo
ReasoningYeslow · highNo
Tool callingYesYes
Structured outputNoYes
Availability
WeightsOpenProprietary
API model IDstep-3.5-flash—
API providers8 (best)2
ReleasedJan 29, 2026Nov 19, 2025
Knowledge cutoffJan 2025—
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.

  • Step 3.5 Flash$1.60
  • Grok 4.1 Fast$3.00
04 — Questions

Which should you choose?

Which is better: Step 3.5 Flash or Grok 4.1 Fast?

Grok 4.1 Fast is the better all-round choice, scoring 71/100 against Step 3.5 Flash (62). It leads on inputs & features and context window. Step 3.5 Flash wins on price. 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, Step 3.5 Flash or Grok 4.1 Fast?

Step 3.5 Flash is cheaper at $0.10 input / $0.30 output per million tokens (official StepFun (Global) API price). Grok 4.1 Fast costs $0.20 input / $0.50 output per million tokens (median across 2 API providers). At a typical mix of three input tokens to one output token, that is $0.15 per million tokens for Step 3.5 Flash versus $0.275 for Grok 4.1 Fast (1.8× as much).

Which scores higher on benchmarks?

There is no independent benchmark that covers both models yet. Step 3.5 Flash has not been scored yet and Grok 4.1 Fast has not been scored yet.

Which is better for coding?

There are no published SWE-bench Verified results for Step 3.5 Flash and Grok 4.1 Fast 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?

Grok 4.1 Fast has the largest context window at 2,000,000 tokens, against 256,000 for Step 3.5 Flash. Maximum output per response: Step 3.5 Flash up to 256,000, Grok 4.1 Fast up to 30,000 tokens.

Which can read images, PDFs, audio or video?

Step 3.5 Flash accepts text; Grok 4.1 Fast accepts text and images. Grok 4.1 Fast handles the widest range of inputs.

Are any of these open source?

Step 3.5 Flash publishes its weights and can be self-hosted; Grok 4.1 Fast is proprietary.

Which is newer?

Step 3.5 Flash is the newest, released Jan 29, 2026. Grok 4.1 Fast came out Nov 19, 2025. Knowledge cutoff: Step 3.5 Flash Jan 2025.

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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