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Stepfun Step 5 Preview (LLM): On AA Pareto frontier

StepFun released Step 5 Preview on September 18, 2026, a reasoning model that scores 44 on the Artificial Analysis Intelligence Index, well above the median of 25 for comparable models. Step 5 Preview accepts text and image input, outputs text, has a 1M-token context window, and is priced at $1.00 per 1M input tokens and $2.70 per 1M output tokens, versus medians of $1.88 and $10.00. Evaluating the model on the Intelligence Index cost $918.34 and generated 160M tokens, compared with a median of 90M.

read4 min views1 publishedSep 19, 2026
Stepfun Step 5 Preview (LLM): On AA Pareto frontier
Image: source

Model summary

Speed

Step 5 Preview is amongst the leading models in intelligence and well priced when comparing to other models of similar price. The model supports text and image input, outputs text, and has a 1M tokens context window.

Step 5 Preview scores 44 on the Artificial Analysis Intelligence Index, placing it well above average among comparable models (median: 25). When evaluating the Intelligence Index, it generated 160M tokens, which is very verbose in comparison to the median of 90M.

Pricing for Step 5 Preview is $1.00 per 1M input tokens (competitively priced, median: $1.88) and $2.70 per 1M output tokens (competitively priced, median: $10.00). In total, it cost $918.34 to evaluate Step 5 Preview on the Intelligence Index.

Reasoning Yes This page shows the reasoning version of this model. A non-reasoning variant may also exist.
Input modality Supports: text and image
Output modality Supports: text
Context window 1M ~1500 A4 pages of size 12 Arial font

Metrics are compared against models of the same class:

  • Non-reasoning models → compared only with other non-reasoning models
  • Reasoning models → compared across both reasoning and non-reasoning
  • Open weights models → compared only with other open weights models of the same size class:
- Tiny: ≤4B parameters
- Small: 4B–40B parameters
- Medium: 40B–150B parameters
- Large: >150B parameters
  • Proprietary models → compared across proprietary and open weights models of the same price range, using a blended 3:1 input/output price ratio:

  • <$0.15 per 1M tokens

  • $0.15–$1 per 1M tokens

  • $1 per 1M tokens Highlights

Speed

IntelligenceUpdated #

Artificial Analysis Intelligence Index

Artificial Analysis Intelligence Index by Open Weights / Proprietary

Measures the performance of models on specific capabilities and industries

Artificial Analysis Finance & Accounting Index

Intelligence Evaluations

Agentic knowledge work, (Elo-500)/2000

Agentic real-world work tasks, (Elo-500)/2000

[AutomationBench-AA](https://artificialanalysis.ai/evaluations/automationbench-aa)Updated

Agentic SaaS workflows

Agentic coding & terminal use

Coding

Reasoning & knowledge

GDP.pdfNew Professional document reasoning, All-pass

Physics reasoning

Knowledge

1 - hallucination rate

Long context reasoning

Legal agentic work, criterion pass rate

Agentic business operations

Quantitative analysis on spreadsheets & documents

Agentic tool use

Kubernetes incident root-cause analysis

Visual reasoning

MLCR-AANew Medical long context reasoning

AA-Briefcase

AA-Briefcase Elo

AA-Omniscience

AA-Omniscience Index

Intelligence Index Comparisons #

Intelligence Index vs. Cost per Intelligence Index Task

Token Use #

Output Tokens per Intelligence Index Task

Cost #

Cost per Intelligence Index Task

Cost to Run Artificial Analysis Intelligence Index

Pricing: Cache Hit, Input, and Output

Context Window #

Context Window

Frequently Asked Questions #

Common questions about Step 5 Preview

Step 5 Preview was released on September 18, 2026.

Step 5 Preview was created by StepFun.

Step 5 Preview scores 44 on the Artificial Analysis Intelligence Index, placing it well above average among other reasoning models in a similar price tier (median: 25).

Step 5 Preview costs $1.00 per 1M input tokens (very competitive, median: $1.88) and $2.70 per 1M output tokens (very competitive, median: $10.00), based on StepFun's API.

Step 5 Preview costs $1.00 per 1M input tokens and $2.70 per 1M output tokens (based on StepFun's API). For a blended rate (7:2:1 cache hit/input/output ratio), this is $0.51 per 1M tokens. Pricing may vary by provider. Compare provider pricing

When evaluated on the Intelligence Index, Step 5 Preview generated 160M output tokens, which is at the higher end compared to other reasoning models in a similar price tier (median: 90M).

Yes, Step 5 Preview is a reasoning model. It uses extended thinking or chain-of-thought reasoning to work through complex problems before providing an answer.

Step 5 Preview supports text and image input.

Step 5 Preview supports text output.

Yes, Step 5 Preview supports image input and can analyze, describe, and answer questions about images.

Yes, Step 5 Preview is multimodal. It can process text and image input and generate text output.

Step 5 Preview has a context window of 1.0M tokens. This determines how much text and conversation history the model can process in a single request.

No, Step 5 Preview is proprietary. The model weights are not publicly available.

Step 5 Preview has 600 billion parameters.

Step 5 Preview achieves a score of 44 on the Artificial Analysis Intelligence Index. This composite benchmark evaluates models across reasoning, knowledge, mathematics, and coding.

Yes, Step 5 Preview is available via API through 1 provider. Compare API providers

Step 5 Preview is available through 1 API provider. Compare providers

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