Grok 4 Fast Reasoning vs Mistral Magistral Small 2509
Grok 4 Fast Reasoning (2025) and Mistral Magistral Small 2509 (2025) are frontier reasoning models from xAI and MistralAI. Grok 4 Fast Reasoning ships a 2m-token context window, while Mistral Magistral Small 2509 ships a not-yet-sourced context window. On pricing, Mistral Magistral Small 2509 costs $0.50/1M input tokens versus $1.25/1M for the alternative. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Mistral Magistral Small 2509 is ~150% cheaper at $0.50/1M; pay for Grok 4 Fast Reasoning only for reasoning depth.
Decision scorecard
Local evidence first| Signal | Grok 4 Fast Reasoning | Mistral Magistral Small 2509 |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and long-context analysis | provider-routed production |
| Decision fit | Long context and Vision | General |
| Context window | 2m | — |
| Cheapest output | $2.50/1M tokens | $1.50/1M tokens |
| Provider routes | 2 tracked | 2 tracked |
| Shared benchmarks | 0 shared | 0 shared |
Decision tradeoffs
- Grok 4 Fast Reasoning has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Grok 4 Fast Reasoning uniquely exposes Vision, Multimodal, and Reasoning in local model data.
- Local decision data tags Grok 4 Fast Reasoning for Long context and Vision.
- Mistral Magistral Small 2509 has the lower cheapest tracked output price at $1.50/1M tokens.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Grok 4 Fast Reasoning
$1,625
Cheapest tracked route/tier: xAI Console
Mistral Magistral Small 2509
$775
Cheapest tracked route/tier: AWS Bedrock
Estimated monthly gap: $850. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Grok 4 Fast Reasoning and Mistral Magistral Small 2509; plan for SDK, billing, or endpoint changes.
- Mistral Magistral Small 2509 is $1/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Vision, Multimodal, and Reasoning before moving production traffic.
- No overlapping tracked provider route is sourced for Mistral Magistral Small 2509 and Grok 4 Fast Reasoning; plan for SDK, billing, or endpoint changes.
- Grok 4 Fast Reasoning is $1/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Grok 4 Fast Reasoning adds Vision, Multimodal, and Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-09-01 | 2025-09-01 |
| Context window | 2m | — |
| Parameters | — | 24B |
| Architecture | Decoder Only | - |
| License | Proprietary | Apache 2.0OSI-approved |
| Openness | Proprietary | Open source |
| Commercial use | Commercial use: conditional | Commercial use: permitted |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | Grok 4 Fast Reasoning | Mistral Magistral Small 2509 |
|---|---|---|
| Input price | $1.25/1M tokens | $0.50/1M tokens |
| Output price | $2.50/1M tokens | $1.50/1M tokens |
| Providers |
Capabilities
| Capability | Grok 4 Fast Reasoning | Mistral Magistral Small 2509 |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| Reasoning | Yes | No |
| Function calling | No | No |
| Tool use | No | No |
| Structured outputs | No | No |
| Code execution | No | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark scores are currently available for this pair.
Deep dive
The capability footprint differs most on vision: Grok 4 Fast Reasoning, multimodal input: Grok 4 Fast Reasoning, and reasoning mode: Grok 4 Fast Reasoning. 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.
For cost, Grok 4 Fast Reasoning lists $1.25/1M input and $2.50/1M output tokens on the cheapest tracked provider, while Mistral Magistral Small 2509 lists $0.50/1M input and $1.50/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Mistral Magistral Small 2509 lower by about $0.83 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.
Choose Grok 4 Fast Reasoning when reasoning depth are central to the workload. Choose Mistral Magistral Small 2509 when provider fit and lower input-token cost 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.
FAQ
Which is cheaper, Grok 4 Fast Reasoning or Mistral Magistral Small 2509?
Mistral Magistral Small 2509 is cheaper on tracked token pricing. Grok 4 Fast Reasoning costs $1.25/1M input and $2.50/1M output tokens. Mistral Magistral Small 2509 costs $0.50/1M input and $1.50/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Grok 4 Fast Reasoning or Mistral Magistral Small 2509 open source?
Grok 4 Fast Reasoning is listed under Proprietary. Mistral Magistral Small 2509 is listed under Apache 2.0. 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 Fast Reasoning or Mistral Magistral Small 2509?
Grok 4 Fast Reasoning 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.
Which is better for multimodal input, Grok 4 Fast Reasoning or Mistral Magistral Small 2509?
Grok 4 Fast Reasoning 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 Fast Reasoning or Mistral Magistral Small 2509?
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.
Where can I run Grok 4 Fast Reasoning and Mistral Magistral Small 2509?
Grok 4 Fast Reasoning is available on Microsoft Foundry and xAI Console. Mistral Magistral Small 2509 is available on AWS Bedrock and Vercel AI Gateway. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-06-15. Data sourced from public model cards and provider documentation.