Grok 4 Fast Reasoning vs Xiaomi MiMo-V2.5-TTS-Series
Grok 4 Fast Reasoning (2025) and Xiaomi MiMo-V2.5-TTS-Series (2026) are frontier reasoning models from xAI and Xiaomi. Grok 4 Fast Reasoning ships a 2m-token context window, while Xiaomi MiMo-V2.5-TTS-Series ships a not-yet-sourced 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.
Xiaomi MiMo-V2.5-TTS-Series is safer overall; choose Grok 4 Fast Reasoning when reasoning depth matters.
Decision scorecard
Local evidence first| Signal | Grok 4 Fast Reasoning | Xiaomi MiMo-V2.5-TTS-Series |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and long-context analysis | multimodal apps |
| Decision fit | Long context and Vision | Vision |
| Context window | 2m | — |
| Cheapest output | $2.50/1M tokens | - |
| Provider routes | 2 tracked | 1 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Grok 4 Fast Reasoning has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Grok 4 Fast Reasoning has broader tracked provider coverage for fallback and procurement flexibility.
- Grok 4 Fast Reasoning uniquely exposes Vision and Reasoning in local model data.
- Local decision data tags Grok 4 Fast Reasoning for Long context and Vision.
- Local decision data tags Xiaomi MiMo-V2.5-TTS-Series for Vision.
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
Xiaomi MiMo-V2.5-TTS-Series
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 Fast Reasoning and Xiaomi MiMo-V2.5-TTS-Series; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Vision and Reasoning before moving production traffic.
- No overlapping tracked provider route is sourced for Xiaomi MiMo-V2.5-TTS-Series and Grok 4 Fast Reasoning; plan for SDK, billing, or endpoint changes.
- Grok 4 Fast Reasoning adds Vision and Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-09-01 | 2026-04-23 |
| Context window | 2m | — |
| Parameters | — | — |
| Architecture | decoder only | - |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use with conditions | Commercial use with conditions |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | Grok 4 Fast Reasoning | Xiaomi MiMo-V2.5-TTS-Series |
|---|---|---|
| Input price | $1.25/1M tokens | - |
| Output price | $2.50/1M tokens | - |
| Providers |
Capabilities
| Capability | Grok 4 Fast Reasoning | Xiaomi MiMo-V2.5-TTS-Series |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | Yes |
| 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 rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on vision: Grok 4 Fast Reasoning and reasoning mode: Grok 4 Fast Reasoning. Both models share multimodal input, 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 $1.25/1M input tokens and Xiaomi MiMo-V2.5-TTS-Series has no token price sourced yet. Provider availability is 2 tracked routes versus 1. 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 and broader provider choice are central to the workload. Choose Xiaomi MiMo-V2.5-TTS-Series 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. 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 Xiaomi MiMo-V2.5-TTS-Series open source?
Grok 4 Fast Reasoning is listed under Proprietary. Xiaomi MiMo-V2.5-TTS-Series is listed under Proprietary. 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 Xiaomi MiMo-V2.5-TTS-Series?
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 Xiaomi MiMo-V2.5-TTS-Series?
Both Grok 4 Fast Reasoning and Xiaomi MiMo-V2.5-TTS-Series expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for reasoning mode, Grok 4 Fast Reasoning or Xiaomi MiMo-V2.5-TTS-Series?
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 Xiaomi MiMo-V2.5-TTS-Series?
Grok 4 Fast Reasoning is available on Microsoft Foundry and xAI Console. Xiaomi MiMo-V2.5-TTS-Series is available on Xiaomi. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
When should I pick Grok 4 Fast Reasoning over Xiaomi MiMo-V2.5-TTS-Series?
Xiaomi MiMo-V2.5-TTS-Series 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 Xiaomi MiMo-V2.5-TTS-Series.
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Last reviewed: 2026-05-26. Data sourced from public model cards and provider documentation.