Step 5 Preview Open vs AIAion 3.5 Paid
Step 5 Preview vs Aion 3.5 compared — price per token, context window, multimodality, openness and which to choose. Can the open-source model replace the paid one? Full 2026 breakdown.
Prices & specs refreshed from live data · olud.ai
Open-model prices = cheapest provider via OpenRouter; official maker rates may be higher.
$2.7 /M outputNo per-token fees if you self-host
$6 /M outputManaged API (no infra to run)
Step 5 Preview vs Aion 3.5 specs
| Spec | Step 5 Preview | Aion 3.5 | Winner |
|---|---|---|---|
| Maker | Stepfun | AionLabs | – |
| Type | Open-weight | Proprietary | |
| Context window | 1M tokens | 262K tokens | |
| Input price | $1/M · free self-host | $3/M | |
| Output price | $2.7/M · free self-host | $6/M | |
| Vision / multimodal | Yes | No | |
| Tool / function calling | Yes | Yes | = Tie |
| Self-hostable | Yes | No (API only) | |
| License | Open weights | Proprietary |
Price gap & when to choose each
Step 5 Preview is ~2.2× cheaper than Aion 3.5 on output tokens ($2.7 vs $6 per M tokens).
- You want to self-host or run on your cloud
- You need the longer 1M context window
- You prioritize data privacy & control
- You want the lowest operating costs
- You are building open or reproducible AI
- You want frontier performance through a managed API
- You value reliability & ecosystem
- You don't want to manage infrastructure
Feature comparison
| Capability | Step 5 Preview | Aion 3.5 |
|---|---|---|
| Open weights (downloadable) | ✓ | ✗ |
| Self-hostable | ✓ | ✗ |
| Runs fully offline | ✓ | ✗ |
| Vision / multimodal | ✓ | ✗ |
| Tool / function calling | ✓ | ✓ |
| 1M+ context window | ✓ | ✗ |
Benchmarks: Step 5 Preview vs Aion 3.5
Independent benchmark scores measured by Artificial Analysis. Higher is better (except latency).
Benchmark data by Artificial Analysis.
How Step 5 Preview and Aion 3.5 score
| Criterion | Step 5 Preview | Aion 3.5 |
|---|---|---|
| Cost-efficiency | 4.5 | 4.0 |
| Context window | 5.0 | 4.0 |
| Openness | 5.0 | 1.5 |
| Self-hosting | 5.0 | 1.0 |
| Multimodality | 5.0 | 3.5 |
Scores come from live data — output price (cost), context length, open vs closed weights (openness & self-hosting) and vision/tool support (multimodality). Raw task quality isn't scored here; it depends on your benchmark — see the verdict.
What each model is
Step 5 Preview Open
Step 5 Preview is StepFun's flagship model for agentic work, built on a sparse Mixture-of-Experts architecture (27B active / 600B total parameters). It performs strongly in software engineering and professional...
Aion 3.5 Paid
Aion 3.5 is a multi-model roleplaying and storytelling system from AionLabs, built on the GLM family of models. It uses a collaborative generation process in which multiple specialized models each...
Other models in these families
These variants are tracked but not compared here — one page per family keeps the comparison readable.
Frequently asked questions
Is Step 5 Preview as good as Aion 3.5?
Step 5 Preview is open-weight and competitive on many tasks, but Aion 3.5 may still lead on the hardest reasoning and agentic work. The gap keeps narrowing — benchmark both on your actual use case before deciding.
Can I run Step 5 Preview locally?
Yes. Step 5 Preview has open weights, so you can self-host it on your own GPUs or run it via a low-cost API. Aion 3.5 is API-only and cannot be self-hosted.
How much cheaper is Step 5 Preview?
Step 5 Preview costs $2.7/M output vs $6/M for Aion 3.5 — roughly 2x cheaper via API, and free if you self-host.
Step 5 Preview vs Aion 3.5 — which should I pick in 2026?
Choose Step 5 Preview if you want to self-host, keep your data private and skip per-token fees — it's open-weight and runs on your own hardware. Choose Aion 3.5 if you want frontier capability through a managed API with zero infrastructure to run.
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