Gemini 3.1 Pro Preview vs 
Riverflow V2 Fast
Gemini 3.1 Pro Preview has a larger context window than Riverflow V2 Fast (1.0M tokens vs 8K tokens).
Written rounds
2 promptsBuy-side IC memo on a fictional SaaS company. Valuation, then the diligence questions.
Five-year LBO on a fictional HVAC business. Returns first, then the sensitivities.
Price and specs
Not enough votes to call it. On the specs, Gemini 3.1 Pro Preview has the edge: bigger model tier, bigger context window, major provider backing.
| Spec | Gemini 3.1 Pro Preview | Riverflow V2 Fast |
|---|---|---|
| Input price | $2/M tokens | — |
| Output price | $12/M tokens | — |
| Context window | 1.0M tokens | 8K tokens |
| Weights | Closed | — |
| Free API (OpenRouter) | No | No |
| Released | Feb 2026 | Feb 2026 |
| At 10M a month | $20.00 | not listed |
Input tokens at list price. No caching, no batch discount.
Where to run it
Gemini 3.1 Pro Preview2 hosts
Riverflow V2 Fast1 host
Per million tokens. Prices and uptime via OpenRouter, checked 10 Oct 2026.
Common questions
What is the difference between Gemini 3.1 Pro Preview and Riverflow V2 Fast?
Gemini 3.1 Pro Preview is developed by Google AI while Riverflow V2 Fast is developed by Sourceful. Gemini 3.1 Pro Preview has a 1.0M token context window vs Riverflow V2 Fast's 8K. You can compare their actual outputs across 2 challenges on Rival to see how they differ in practice.
Which is better, Gemini 3.1 Pro Preview or Riverflow V2 Fast?
It depends on your use case. Gemini 3.1 Pro Preview and Riverflow V2 Fast each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 2 challenges so you can judge which fits your needs best.
How can I compare Gemini 3.1 Pro Preview and Riverflow V2 Fast on Rival?
This page shows a side-by-side comparison of Gemini 3.1 Pro Preview and Riverflow V2 Fast across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.
More comparisons
Against the newest arrivals
- Gemini 3.1 Pro Preview vs Step 5 PreviewLanded Oct 2026
- Riverflow V2 Fast vs Claude Haiku 5.5Landed Oct 2026
- Gemini 3.1 Pro Preview vs Ling 3.1 FlashLanded Oct 2026
- Riverflow V2 Fast vs Mistral Large 4Landed Oct 2026
- Gemini 3.1 Pro Preview vs GPT-6.1 SolLanded Sep 2026
- Riverflow V2 Fast vs Claude Sonnet 5.5Landed Sep 2026
- Gemini 3.1 Pro Preview vs Solar Mini 4Landed Sep 2026
- Riverflow V2 Fast vs Qwen3.8 Max PrimeLanded Sep 2026
Same lab, same size, long tail
- Gemini 3.1 Pro Preview vs Gemini 3.1 Flash Lite PreviewVersion compare
- Gemini 3.1 Pro Preview vs Gemini 3.8 FlashSame lab
- Riverflow V2 Fast vs Ox AlphaSame size
- Riverflow V2 Fast vs GPT-6.1 SolSame size
- Gemini 3.1 Pro Preview vs Mistral NemoNew provider
- Riverflow V2 Fast vs Mistral Small 4New provider
- Gemini 3.1 Pro Preview vs Mistral Small CreativeNew provider
- Riverflow V2 Fast vs Muse Glimmer 30BNew provider
