Grok 4 Fast Reasoning vs Nemotron 3 Super-120B-A12B
Grok 4 Fast Reasoning (2025) and Nemotron 3 Super-120B-A12B (2026) are frontier reasoning models from xAI and NVIDIA AI. Grok 4 Fast Reasoning ships a not-yet-sourced context window, while Nemotron 3 Super-120B-A12B ships a 1M-token context window. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
Nemotron 3 Super-120B-A12B is safer overall; choose Grok 4 Fast Reasoning when reasoning depth matters.
Decision scorecard
Local evidence first| Signal | Grok 4 Fast Reasoning | Nemotron 3 Super-120B-A12B |
|---|---|---|
| Decision fit | General | RAG, Long context, and Classification |
| Context window | — | 1M |
| Cheapest output | - | $0.45/1M tokens |
| Provider routes | 1 tracked | 3 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Grok 4 Fast Reasoning uniquely exposes Reasoning in local model data.
- Nemotron 3 Super-120B-A12B has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Nemotron 3 Super-120B-A12B has broader tracked provider coverage for fallback and procurement flexibility.
- Nemotron 3 Super-120B-A12B uniquely exposes Structured outputs in local model data.
- Local decision data tags Nemotron 3 Super-120B-A12B for RAG, Long context, and Classification.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
Grok 4 Fast Reasoning
Unavailable
No complete token price in local provider data
Nemotron 3 Super-120B-A12B
$185
Cheapest tracked route: OpenRouter
Cost delta unavailable until both models have sourced input and output token prices.
Switch friction
- No overlapping tracked provider route is sourced for Grok 4 Fast Reasoning and Nemotron 3 Super-120B-A12B; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Reasoning before moving production traffic.
- Nemotron 3 Super-120B-A12B adds Structured outputs in local capability data.
- No overlapping tracked provider route is sourced for Nemotron 3 Super-120B-A12B and Grok 4 Fast Reasoning; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Structured outputs before moving production traffic.
- Grok 4 Fast Reasoning adds Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-09-01 | 2026-03-11 |
| Context window | — | 1M |
| Parameters | — | 120B |
| Architecture | decoder only | decoder only |
| License | Proprietary | Unknown |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | Grok 4 Fast Reasoning | Nemotron 3 Super-120B-A12B |
|---|---|---|
| Input price | - | $0.09/1M tokens |
| Output price | - | $0.45/1M tokens |
| Providers |
Capabilities
| Capability | Grok 4 Fast Reasoning | Nemotron 3 Super-120B-A12B |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | Yes | No |
| Function calling | No | No |
| Tool use | No | No |
| Structured outputs | No | Yes |
| Code execution | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on reasoning mode: Grok 4 Fast Reasoning and structured outputs: Nemotron 3 Super-120B-A12B. Both models share the core language-model surface, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
Pricing coverage is uneven: Grok 4 Fast Reasoning has no token price sourced yet and Nemotron 3 Super-120B-A12B has $0.09/1M input tokens. Provider availability is 1 tracked routes versus 3. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose Grok 4 Fast Reasoning when reasoning depth are central to the workload. Choose Nemotron 3 Super-120B-A12B when provider fit and broader provider choice are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions. It also helps separate model capability from provider packaging, which can change cost and latency. For teams standardizing a stack, that distinction is often the difference between a benchmark win and a reliable deployment.
FAQ
Is Grok 4 Fast Reasoning or Nemotron 3 Super-120B-A12B open source?
Grok 4 Fast Reasoning is listed under Proprietary. Nemotron 3 Super-120B-A12B is listed under Unknown. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for reasoning mode, Grok 4 Fast Reasoning or Nemotron 3 Super-120B-A12B?
Grok 4 Fast Reasoning has the clearer documented reasoning mode signal in this comparison. If reasoning mode is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for structured outputs, Grok 4 Fast Reasoning or Nemotron 3 Super-120B-A12B?
Nemotron 3 Super-120B-A12B has the clearer documented structured outputs signal in this comparison. If structured outputs is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Grok 4 Fast Reasoning and Nemotron 3 Super-120B-A12B?
Grok 4 Fast Reasoning is available on Microsoft Foundry. Nemotron 3 Super-120B-A12B is available on DeepInfra, NVIDIA NIM, and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
When should I pick Grok 4 Fast Reasoning over Nemotron 3 Super-120B-A12B?
Nemotron 3 Super-120B-A12B is safer overall; choose Grok 4 Fast Reasoning when reasoning depth matters. If your workload also depends on reasoning depth, start with Grok 4 Fast Reasoning; if it depends on provider fit, run the same evaluation with Nemotron 3 Super-120B-A12B.
Continue comparing
Last reviewed: 2026-05-14. Data sourced from public model cards and provider documentation.