Grok 4.3 vs Nemotron 3 Ultra
Grok 4.3 (2026) and Nemotron 3 Ultra (2026) are frontier-tier reasoning models from xAI and NVIDIA AI. Grok 4.3 ships a 1m-token context window, while Nemotron 3 Ultra ships a 1m-token context window. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads. It focuses on practical selection signals rather than broad model-family marketing.
Nemotron 3 Ultra is safer overall; choose Grok 4.3 when vision-heavy evaluation matters.
Decision scorecard
Local evidence first| Signal | Grok 4.3 | Nemotron 3 Ultra |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps and long-context analysis |
| Decision fit | RAG, Agents, and Long context | Long context |
| Context window | 1m | 1m |
| Cheapest output | $2.50/1M tokens | - |
| Provider routes | 4 tracked | 0 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Grok 4.3 has broader tracked provider coverage for fallback and procurement flexibility.
- Grok 4.3 uniquely exposes Vision, Multimodal, and Function calling in local model data.
- Local decision data tags Grok 4.3 for RAG, Agents, and Long context.
- Local decision data tags Nemotron 3 Ultra for Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Grok 4.3
$1,625
Cheapest tracked route/tier: xAI Console
Nemotron 3 Ultra
Unavailable
No complete token price in local provider data
Cost delta unavailable until both models have sourced input and output token prices.
Switch friction
- No overlapping tracked provider route is sourced for Grok 4.3 and Nemotron 3 Ultra; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Vision, Multimodal, and Function calling before moving production traffic.
- No overlapping tracked provider route is sourced for Nemotron 3 Ultra and Grok 4.3; plan for SDK, billing, or endpoint changes.
- Grok 4.3 adds Vision, Multimodal, and Function calling in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-06 | 2026-06-04 |
| Context window | 1m | 1m |
| Parameters | ~0.5T | 550B |
| Architecture | - | moe |
| License | Proprietary | NVIDIA Open Model |
| Openness | Proprietary | Open weights |
| Commercial use | Commercial use with conditions | Commercial use allowed |
| Knowledge cutoff | 2024-11 | - |
Pricing and availability
| Pricing attribute | Grok 4.3 | Nemotron 3 Ultra |
|---|---|---|
| Input price |
| - |
| Output price |
| - |
| Providers | - |
Capabilities
| Capability | Grok 4.3 | Nemotron 3 Ultra |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| Reasoning | Yes | Yes |
| Function calling | Yes | No |
| Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | No | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on vision: Grok 4.3, multimodal input: Grok 4.3, function calling: Grok 4.3, tool use: Grok 4.3, and structured outputs: Grok 4.3. Both models share reasoning mode, 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 4.3 has $1.25/1M input tokens and Nemotron 3 Ultra has no token price sourced yet. Provider availability is 4 tracked routes versus 0. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose Grok 4.3 when vision-heavy evaluation and broader provider choice are central to the workload. Choose Nemotron 3 Ultra when provider fit 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.
FAQ
Which has a larger context window, Grok 4.3 or Nemotron 3 Ultra?
Grok 4.3 supports 1m tokens, while Nemotron 3 Ultra supports 1m tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Is Grok 4.3 or Nemotron 3 Ultra open source?
Grok 4.3 is listed under Proprietary. Nemotron 3 Ultra is listed under NVIDIA Open Model. 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 vision, Grok 4.3 or Nemotron 3 Ultra?
Grok 4.3 has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Grok 4.3 or Nemotron 3 Ultra?
Grok 4.3 has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for reasoning mode, Grok 4.3 or Nemotron 3 Ultra?
Both Grok 4.3 and Nemotron 3 Ultra expose reasoning mode. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Where can I run Grok 4.3 and Nemotron 3 Ultra?
Grok 4.3 is available on xAI Console, OpenRouter, Microsoft Foundry, and Vercel AI Gateway. Nemotron 3 Ultra is available on the tracked providers still being sourced. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-06-09. Data sourced from public model cards and provider documentation.