Step 5 Preview vs Seed 2.1 Pro vs LongCat-2.5-Preview
Step 5 Preview comes out ahead, 57 to 52 and 50 on our weighted score, though LongCat-2.5-Preview is 9% cheaper per token.
- Our pick
StepFunStep 5 Preview
57/100- ECI—
- Price$1.00 / $2.70
- Context1M
ByteDance SeedSeed 2.1 Pro
50/100- ECI—
- Price$0.891 / $4.45
- Context256K
Meituan (LongCat)LongCat-2.5-Preview
52/100- ECI—
- Price$0.75 / $2.95
- Context1M
Step 5 Preview is our pick
Step 5 Preview is the better all-round choice, scoring 57/100 against LongCat-2.5-Preview (52) and Seed 2.1 Pro (50). LongCat-2.5-Preview 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 priceLongCat-2.5-PreviewLongCat-2.5-Preview $1.30 · Step 5 Preview $1.43 · Seed 2.1 Pro $1.78 per 1M tokens (3:1 blend)
- Longest contextStep 5 Preview and LongCat-2.5-PreviewStep 5 Preview 1,000,000 · LongCat-2.5-Preview 1,000,000 · Seed 2.1 Pro 256,000 tokens
- Widest inputsStep 5 Preview and Seed 2.1 ProStep 5 Preview: Text, Images, Video · Seed 2.1 Pro: Text, Images, Video · LongCat-2.5-Preview: Text, Images
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Step 5 Preview | Seed 2.1 Pro | LongCat-2.5-Preview |
|---|---|---|---|---|
| Price | 50% | 43 | 38 | 44 |
| Inputs & features | 30% | 80 | 80 | 60 |
| Context window | 20% | 60 | 36 | 60 |
| Overall | 100% | 57/100 | 50/100 | 52/100 |
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 | Step 5 PreviewStepFun | Seed 2.1 ProByteDance Seed | LongCat-2.5-PreviewMeituan (LongCat) |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | — | — | — |
| ECI rank | — | — | — |
| Price per million tokens | |||
| Input | $1.00 | $0.891 | $0.75 (best) |
| Output | $2.70 (best) | $4.45 | $2.95 |
| Cached input | $0.05 (best) | $0.178 | — |
| Blended (3:1) | $1.43 | $1.78 | $1.30 (best) |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Official StepFun (Global) API | Official Volcengine Ark API | Median of 1 providers |
| Limits | |||
| Context window | 1,000,000 tokens (best) | 256,000 tokens | 1,000,000 tokens (best) |
| Max output | 1,000,000 tokens (best) | 256,000 tokens | 131,072 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | No | No | No |
| Audio | No | No | No |
| Video | Yes | Yes | No |
| Reasoning | Yeslow · medium · high | Yesminimal · low · medium · high · xhigh · max | Yes |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | No |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | step-5-preview | doubao-seed-2-1-pro-260628 | — |
| API providers | 7 (best) | 2 | 2 |
| Released | Sep 16, 2026 | Jun 23, 2026 | Sep 25, 2026 |
| Knowledge cutoff | — | — | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Step 5 Preview$15.40
- Seed 2.1 Pro$17.81
- LongCat-2.5-Preview$13.40
Which should you choose?
Which is better: Step 5 Preview, Seed 2.1 Pro or LongCat-2.5-Preview?
Step 5 Preview is the better all-round choice, scoring 57/100 against LongCat-2.5-Preview (52) and Seed 2.1 Pro (50). LongCat-2.5-Preview 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 5 Preview, Seed 2.1 Pro or LongCat-2.5-Preview?
LongCat-2.5-Preview is cheaper at $0.75 input / $2.95 output per million tokens (median across 1 API provider). Step 5 Preview costs $1.00 input / $2.70 output per million tokens (official StepFun (Global) API price); Seed 2.1 Pro 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 $1.30 per million tokens for LongCat-2.5-Preview versus $1.43 for Step 5 Preview (1.1× as much) and $1.78 for Seed 2.1 Pro (1.4× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers all three models yet. Step 5 Preview has not been scored yet, Seed 2.1 Pro has not been scored yet and LongCat-2.5-Preview has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for Step 5 Preview, Seed 2.1 Pro and LongCat-2.5-Preview 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?
Step 5 Preview and LongCat-2.5-Preview have the largest context windows (1,000,000 and 1,000,000 tokens), against 256,000 for Seed 2.1 Pro. Maximum output per response: Step 5 Preview up to 1,000,000, Seed 2.1 Pro up to 256,000, LongCat-2.5-Preview up to 131,072 tokens.
Which can read images, PDFs, audio or video?
Step 5 Preview accepts text, images and video; Seed 2.1 Pro accepts text, images and video; LongCat-2.5-Preview accepts text and images. Step 5 Preview handles the widest range of inputs.
Are any of these open source?
No. Step 5 Preview, Seed 2.1 Pro and LongCat-2.5-Preview are proprietary and only available through APIs and apps.
Which is newer?
LongCat-2.5-Preview is the newest, released Sep 25, 2026. Step 5 Preview came out Sep 16, 2026; Seed 2.1 Pro came out Jun 23, 2026.
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.
