Seed Evolving vs Step 5 Preview vs MiMo-V2.5-Pro-UltraSpeed
Step 5 Preview comes out ahead, 57 to 50 and 43 on our weighted score, and it is the cheaper option too.
ByteDance SeedSeed Evolving
50/100- ECI—
- Price$0.891 / $4.45
- Context256K
- Our pick
StepFunStep 5 Preview
57/100- ECI—
- Price$1.00 / $2.70
- Context1M
XiaomiMiMo-V2.5-Pro-UltraSpeed
43/100- ECI—
- Price$1.30 / $2.61
- Context1.05M
Step 5 Preview is our pick
Step 5 Preview is the better all-round choice, scoring 57/100 against Seed Evolving (50) and MiMo-V2.5-Pro-UltraSpeed (43). It leads 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 5 PreviewStep 5 Preview $1.43 · MiMo-V2.5-Pro-UltraSpeed $1.63 · Seed Evolving $1.78 per 1M tokens (3:1 blend)
- Longest contextMiMo-V2.5-Pro-UltraSpeedMiMo-V2.5-Pro-UltraSpeed 1,048,576 · Step 5 Preview 1,000,000 · Seed Evolving 256,000 tokens
- Widest inputsSeed Evolving and Step 5 PreviewSeed Evolving: Text, Images, Video · Step 5 Preview: Text, Images, Video · MiMo-V2.5-Pro-UltraSpeed: Text
- Self-hostingMiMo-V2.5-Pro-UltraSpeedPublishes downloadable weights
| Measure | Weight | Seed Evolving | Step 5 Preview | MiMo-V2.5-Pro-UltraSpeed |
|---|---|---|---|---|
| Price | 50% | 38 | 43 | 40 |
| Inputs & features | 30% | 80 | 80 | 35 |
| Context window | 20% | 36 | 60 | 61 |
| Overall | 100% | 50/100 | 57/100 | 43/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Seed EvolvingByteDance Seed | Step 5 PreviewStepFun | MiMo-V2.5-Pro-UltraSpeedXiaomi |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | — | — | — |
| ECI rank | — | — | — |
| Price per million tokens | |||
| Input | $0.891 (best) | $1.00 | $1.30 |
| Output | $4.45 | $2.70 | $2.61 (best) |
| Cached input | $0.178 | $0.05 | $0.011 (best) |
| Blended (3:1) | $1.78 | $1.43 (best) | $1.63 |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Official Volcengine Ark API | Official StepFun (Global) API | Official Xiaomi API |
| Limits | |||
| Context window | 256,000 tokens | 1,000,000 tokens | 1,048,576 tokens (best) |
| Max output | 256,000 tokens | 1,000,000 tokens (best) | 131,072 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | No |
| PDFs | No | No | No |
| Audio | No | No | No |
| Video | Yes | Yes | No |
| Reasoning | Yesminimal · low · medium · high · xhigh · max | Yeslow · medium · high | Yes |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | No |
| Availability | |||
| Weights | Proprietary | Proprietary | Open |
| API model ID | doubao-seed-evolving | step-5-preview | mimo-v2.5-pro-ultraspeed |
| API providers | 2 | 7 (best) | 1 |
| Released | Jun 23, 2026 | Sep 16, 2026 | Jun 8, 2026 |
| Knowledge cutoff | — | — | Dec 2024 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Seed Evolving$17.81
- Step 5 Preview$15.40
- MiMo-V2.5-Pro-UltraSpeed$18.27
Which should you choose?
Which is better: Seed Evolving, Step 5 Preview or MiMo-V2.5-Pro-UltraSpeed?
Step 5 Preview is the better all-round choice, scoring 57/100 against Seed Evolving (50) and MiMo-V2.5-Pro-UltraSpeed (43). It leads 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, Seed Evolving, Step 5 Preview or MiMo-V2.5-Pro-UltraSpeed?
Step 5 Preview is cheaper at $1.00 input / $2.70 output per million tokens (official StepFun (Global) API price). MiMo-V2.5-Pro-UltraSpeed costs $1.30 input / $2.61 output per million tokens (official Xiaomi API price); Seed Evolving costs $0.891 input / $4.45 output per million tokens (official Volcengine Ark API price). At a typical mix of three input tokens to one output token, that is $1.43 per million tokens for Step 5 Preview versus $1.63 for MiMo-V2.5-Pro-UltraSpeed (1.1× as much) and $1.78 for Seed Evolving (1.2× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers all three models yet. Seed Evolving has not been scored yet, Step 5 Preview has not been scored yet and MiMo-V2.5-Pro-UltraSpeed has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for Seed Evolving, Step 5 Preview and MiMo-V2.5-Pro-UltraSpeed yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. All three support tool calling for agent workflows.
Which has the bigger context window?
MiMo-V2.5-Pro-UltraSpeed has the largest context window at 1,048,576 tokens, against 1,000,000 for Step 5 Preview and 256,000 for Seed Evolving. Maximum output per response: Seed Evolving up to 256,000, Step 5 Preview up to 1,000,000, MiMo-V2.5-Pro-UltraSpeed up to 131,072 tokens.
Which can read images, PDFs, audio or video?
Seed Evolving accepts text, images and video; Step 5 Preview accepts text, images and video; MiMo-V2.5-Pro-UltraSpeed accepts text. Seed Evolving handles the widest range of inputs.
Are any of these open source?
MiMo-V2.5-Pro-UltraSpeed publishes its weights and can be self-hosted; Seed Evolving and Step 5 Preview is proprietary.
Which is newer?
Step 5 Preview is the newest, released Sep 16, 2026. Seed Evolving came out Jun 23, 2026; MiMo-V2.5-Pro-UltraSpeed came out Jun 8, 2026. Knowledge cutoff: MiMo-V2.5-Pro-UltraSpeed Dec 2024.
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.
