Riverflow V2.6 Pro vs Solar Pro 4: which should you choose in 2026?
Riverflow V2.6 Pro (by Sourceful) and Solar Pro 4 (by Upstage) are compared below. Here is how they stack up on benchmarks, price, and capabilities, and which one to pick in 2026.
There are not enough shared, protocol-compatible benchmark results to declare a performance leader.
Choose Riverflow V2.6 Pro if…
- • you need image inputs
- • you need image generation
Choose Solar Pro 4 if…
- • your own prompt tests favor its output; shared comparable evidence does not identify a unique advantage
The benchmark count includes only results measured with a matching benchmark version and protocol. Arena scores are shown separately. Missing, preliminary, and incompatible data is not treated as a controlled win. Published point-score comparisons are labeled separately when protocol details are incomplete. For text-output models, the verdict also compares token pricing and context windows.
Performance benchmarks
Every value links to its source. A dash means that no reviewed result is available for that exact model and protocol.
| Benchmark | Riverflow V2.6 Pro | Solar Pro 4 |
|---|---|---|
A 657-task benchmark of multi-step work across simulated SaaS applications in six business domains. The Artificial Analysis protocol reports a guardrail-aware score and is distinct from both the public Zapier split and the unrelated dynamic AutoBench framework. Guardrail-aware score | — | — |
A benchmark of difficult, verifiable information-seeking questions designed to measure an agent's ability to locate hard-to-find facts through web browsing. Accuracy | — | — |
A verified computer-use benchmark in which multimodal agents operate desktop applications and are graded from the resulting environment state. Mean task reward | — | — |
A human-validated subset of real GitHub issues used to measure whether a coding agent can produce repository patches that resolve the associated tests. Resolved | — | — |
Version 2.1 of the benchmark for completing realistic tasks in terminal environments. Harness, resource limits, and attempt count are part of the protocol. Mean task success | — | — |
A dynamic LLM evaluation framework in which models generate questions, answer them, and participate in reciprocal peer assessment. AutoBench is distinct from Zapier's AutomationBench. Weighted peer-assessment score | — | — |
The highest-quality subset of Graduate-Level Google-Proof Q&A, designed to test expert-level scientific reasoning in biology, physics, and chemistry. Accuracy | — | — |
A 2,500-question expert-level benchmark spanning dozens of academic fields. Tool-assisted and no-tools results are separate protocols and must not be merged. Accuracy | — | — |
| Arena preference scores | ||
Human preference score | — | 1386 ±6 |
Human preference score for code and web development | — | 1370 ±10 |
Benchmark sources
Reviewed evidence last updated 2026-08-09. Arena data last refreshed Oct 5, 2026.
Pricing, capabilities, and model facts
| Feature | Riverflow V2.6 Pro | Solar Pro 4 |
|---|---|---|
| Context & model facts | ||
| Developer | Sourceful | Upstage |
| API provider | Sourceful | Upstage |
| Input context | 32,768 tokens | 524,288 tokens |
| Maximum output | 29,491 tokens | 131,072 tokens |
| Released | — | — |
| Added to Writingmate | Oct 29, 2026 | Aug 10, 2026 |
| License | Not available | Not available |
| Knowledge cutoff | — | — |
| Capabilities | ||
| Inputs | Text, Image | Text |
| Outputs | Image | Text |
| Provider endpoint accepts tool parameters | No | Yes |
| Reasoning | Yes | Yes |
| Vision | Yes | No |
| Image Generation | Yes | No |
| Video Generation | No | No |
| API performance | ||
| p95 latency | Not measured | Not measured |
| Output throughput | Not measured | Not measured |
| Writingmate shows API performance only when both models have enough observations from the same measurement window, prompt profile, and provider. Third-party latency values are not copied into this table. | ||
Data sources
- Writingmate model catalog (pricing, limits, and availability)
Catalog data last updated Oct 29, 2026.
Why Pay for Multiple Subscriptions?
Comparing Riverflow V2.6 Pro from Sourceful with Solar Pro 4 from Upstage? Instead of managing separate API keys and subscriptions, get both with Writingmate.
| Plan | Price | Riverflow V2.6 Pro | Solar Pro 4 | AI Images | AI Video |
|---|---|---|---|---|---|
Writingmate Pro Most popular | $20/mo | Included | Included | Nano Banana Pro, FLUX.2, DALL-E & more | VEO 3.1, Kling 3.0 |
Writingmate Ultimate Power users | $60/mo | Included | Included | Nano Banana Pro, FLUX.2, DALL-E & more | VEO 3.1, Kling 3.0 |
Riverflow V2.6 Pro vs Solar Pro 4 FAQ
Which is better, Riverflow V2.6 Pro or Solar Pro 4?
There are not enough shared, protocol-compatible benchmark results to declare a performance leader.
Which model is cheaper to use through an API?
A comparable blended token price is not available for both models. Check the API pricing rows for the values that are currently published.
Which model supports more context?
Comparable context-window data is not available for both models.
Can I switch between Riverflow V2.6 Pro and Solar Pro 4?
Yes. Use the model selector on this page to open any current Writingmate model comparison. You can also run the same prompt with both models in Writingmate.
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