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Compare performance benchmarks, coding intelligence, reasoning evaluations, context limits, and API economics between Kimi K3.1 Pro (Moonshot AI) and Step 5 Preview (StepFun).
| Metric / Capability | Kimi K3.1 Pro | Step 5 Preview |
|---|---|---|
| Developer / Organization | Moonshot AI | StepFun |
| Release Date | 2026-10-23 | 2026-10-08 |
| Deployment / Weights | Proprietary Cloud API | Open Weights |
| Context Window | 1.0M tokens (1,048,576 tokens) | 1.0M tokens (1,048,576 tokens) |
| Input Pricing (/1M Tokens) | $2 | Free (Open Weights) |
| Output Pricing (/1M Tokens) | $10 | Free (Open Weights) |
| Benchmark / Domain | Kimi K3.1 Pro | Step 5 Preview | Advantage |
|---|---|---|---|
Artificial Analysis Intelligence Index Composite index aggregating 10+ evaluations of general reasoning and knowledge. | 55.1% | 43.7% | Kimi K3.1 Pro (+26%) |
Artificial Analysis Coding Agent Index v2.0 Composite index of coding-agent systems (model + harness) across FrontierCode v1.1, SWE-Atlas-QnA, and Terminal-Bench v4. | — | 43.1% | — |
Terminal-Bench 4.0 Sandboxed command-line tasks requiring shell and file-system operation. | 65.7% | 33.3% | Kimi K3.1 Pro (+97%) |
GPQA Diamond Graduate-level physics, chemistry, and biology questions written by domain experts. | 94.2% | 93.5% | Kimi K3.1 Pro (+1%) |
Humanity's Last Exam Expert-written questions across hundreds of disciplines designed to resist saturation. | 51.1% | 46.5% | Kimi K3.1 Pro (+10%) |
Design Arena ELO Human-preference ELO across UI, 3D, data-visualization, and game-dev generations. | 1448 | — | — |
Kimi K3.1 Pro leads across 4 evaluated benchmarks compared to 0 for Step 5 Preview, showing notable advantages in Artificial Analysis Intelligence Index, Terminal-Bench 4.0, GPQA Diamond.
Both models feature equivalent context windows of 1.0M tokens (1,048,576 tokens).
Step 5 Preview is more economical. Input tokens cost $Free (Open Weights)/M tokens compared to $2/M tokens for Kimi K3.1 Pro.
Kimi K3.1 Pro is a proprietary cloud API. Step 5 Preview is an open-weights model.
Analyze 130+ models side-by-side using interactive radar charts, cost-efficiency quadrant plots, and live dataset filters on the full NeuBench index.
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