Grok 4 Fast Reasoning vs Jamba Mini
Grok 4 Fast Reasoning comes out ahead, 75 to 55 on our weighted score, though Jamba Mini is 9% cheaper per token.
- Our pick
xAIGrok 4 Fast Reasoning
75/100- ECI—
- Price$0.20 / $0.50
- Context2M
AI21 LabsJamba Mini
55/100- ECI—
- Price$0.20 / $0.40
- Context256K
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 Jamba Mini (55). It leads on inputs & features and context window. Jamba Mini 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 priceJamba MiniJamba Mini $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 · Jamba Mini 256,000 tokens
- Widest inputsGrok 4 Fast ReasoningGrok 4 Fast Reasoning: Text, Images, Audio, Video · Jamba Mini: Text
- Self-hostingJamba MiniPublishes downloadable weights
| Measure | Weight | Grok 4 Fast Reasoning | Jamba Mini |
|---|---|---|---|
| Price | 50% | 73 | 75 |
| Inputs & features | 30% | 80 | 35 |
| Context window | 20% | 72 | 36 |
| Overall | 100% | 75/100 | 55/100 |
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 | Jamba MiniAI21 Labs |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | — | — |
| ECI rank | — | — |
| Price per million tokens | ||
| Input | $0.20 | $0.20 |
| Output | $0.50 | $0.40 (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 AI21 Labs API |
| Limits | ||
| Context window | 2,000,000 tokens (best) | 256,000 tokens |
| Max output | 2,000,000 tokens (best) | 4,096 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | No |
| PDFs | No | No |
| Audio | Yes | No |
| Video | Yes | No |
| Reasoning | Yes | No |
| Tool calling | Yes | Yes |
| Structured output | No | Yes |
| Availability | ||
| Weights | Proprietary | Open |
| API model ID | — | jamba-mini |
| API providers | 5 (best) | 1 |
| Released | Dec 18, 2025 | Jan 8, 2026 |
| Knowledge cutoff | — | Aug 22, 2024 |
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
- Jamba Mini$2.80
Which should you choose?
Which is better: Grok 4 Fast Reasoning or Jamba Mini?
Grok 4 Fast Reasoning is the better all-round choice, scoring 75/100 against Jamba Mini (55). It leads on inputs & features and context window. Jamba Mini 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 Jamba Mini?
Jamba Mini is cheaper at $0.20 input / $0.40 output per million tokens (official AI21 Labs 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 Jamba Mini 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 Jamba Mini has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for Grok 4 Fast Reasoning and Jamba Mini 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 256,000 for Jamba Mini. Maximum output per response: Grok 4 Fast Reasoning up to 2,000,000, Jamba Mini up to 4,096 tokens.
Which can read images, PDFs, audio or video?
Grok 4 Fast Reasoning accepts text, images, audio and video; Jamba Mini accepts text. Grok 4 Fast Reasoning handles the widest range of inputs.
Are any of these open source?
Jamba Mini publishes its weights and can be self-hosted; Grok 4 Fast Reasoning is proprietary.
Which is newer?
Jamba Mini is the newest, released Jan 8, 2026. Grok 4 Fast Reasoning came out Dec 18, 2025. Knowledge cutoff: Jamba Mini Aug 22, 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 Nov 2, 2026.
