Grok 4 Fast Reasoning vs Solar Pro 3
Grok 4 Fast Reasoning comes out ahead, 75 to 53 on our weighted score, though Solar Pro 3 is 9% cheaper per token.
- Our pick
xAIGrok 4 Fast Reasoning
75/100- ECI—
- Price$0.20 / $0.50
- Context2M
UpstageSolar Pro 3
53/100- ECI—
- Price$0.25 / $0.25
- Context131K
Add a model
Make it a three-way comparison.
Grok 4 Fast Reasoning is our pick
Grok 4 Fast Reasoning is the better all-round choice, scoring 75/100 against Solar Pro 3 (53). It leads on inputs & features and context window. Solar Pro 3 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 priceSolar Pro 3Solar Pro 3 $0.25 · Grok 4 Fast Reasoning $0.275 per 1M tokens (3:1 blend)
- Longest contextGrok 4 Fast ReasoningGrok 4 Fast Reasoning 2,000,000 · Solar Pro 3 131,072 tokens
- Widest inputsGrok 4 Fast ReasoningGrok 4 Fast Reasoning: Text, Images, Audio, Video · Solar Pro 3: Text
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | Grok 4 Fast Reasoning | Solar Pro 3 |
|---|---|---|---|
| Price | 50% | 73 | 75 |
| Inputs & features | 30% | 80 | 35 |
| Context window | 20% | 72 | 25 |
| Overall | 100% | 75/100 | 53/100 |
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 | Grok 4 Fast ReasoningxAI | Solar Pro 3Upstage |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | — | — |
| ECI rank | — | — |
| Price per million tokens | ||
| Input | $0.20 (best) | $0.25 |
| Output | $0.50 | $0.25 (best) |
| Cached input | — | — |
| Blended (3:1) | $0.275 | $0.25 (best) |
| Long-context rate | Same rate | Same rate |
| Price source | Median of 4 providers | Official Upstage API |
| Limits | ||
| Context window | 2,000,000 tokens (best) | 131,072 tokens |
| Max output | 2,000,000 tokens (best) | 8,192 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | No |
| PDFs | No | No |
| Audio | Yes | No |
| Video | Yes | No |
| Reasoning | Yes | Yeslow · medium · high |
| Tool calling | Yes | Yes |
| Structured output | No | No |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | — | solar-pro3 |
| API providers | 5 (best) | 4 |
| Released | Dec 18, 2025 | Jan 26, 2026 |
| Knowledge cutoff | — | Jul 2025 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Grok 4 Fast Reasoning$3.00
- Solar Pro 3$3.00
Which should you choose?
Which is better: Grok 4 Fast Reasoning or Solar Pro 3?
Grok 4 Fast Reasoning is the better all-round choice, scoring 75/100 against Solar Pro 3 (53). It leads on inputs & features and context window. Solar Pro 3 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, Grok 4 Fast Reasoning or Solar Pro 3?
Solar Pro 3 is cheaper at $0.25 input / $0.25 output per million tokens (official Upstage API price). Grok 4 Fast Reasoning costs $0.20 input / $0.50 output per million tokens (median across 4 API providers). At a typical mix of three input tokens to one output token, that is $0.25 per million tokens for Solar Pro 3 versus $0.275 for Grok 4 Fast Reasoning (1.1× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers both models yet. Grok 4 Fast Reasoning has not been scored yet and Solar Pro 3 has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for Grok 4 Fast Reasoning and Solar Pro 3 yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.
Which has the bigger context window?
Grok 4 Fast Reasoning has the largest context window at 2,000,000 tokens, against 131,072 for Solar Pro 3. Maximum output per response: Grok 4 Fast Reasoning up to 2,000,000, Solar Pro 3 up to 8,192 tokens.
Which can read images, PDFs, audio or video?
Grok 4 Fast Reasoning accepts text, images, audio and video; Solar Pro 3 accepts text. Grok 4 Fast Reasoning handles the widest range of inputs.
Are any of these open source?
No. Grok 4 Fast Reasoning and Solar Pro 3 are proprietary and only available through APIs and apps.
Which is newer?
Solar Pro 3 is the newest, released Jan 26, 2026. Grok 4 Fast Reasoning came out Dec 18, 2025. Knowledge cutoff: Solar Pro 3 Jul 2025.
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 Nov 2, 2026.
