Grok 4 Fast Reasoning vs Xiaomi MiMo-V2.5
Grok 4 Fast Reasoning (2025) and Xiaomi MiMo-V2.5 (2026) are frontier-tier reasoning models from xAI and Xiaomi. Grok 4 Fast Reasoning ships a 2m-token context window, while Xiaomi MiMo-V2.5 ships a 1.05m-token context window. On pricing, Xiaomi MiMo-V2.5 costs $0.14/1M 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.
Xiaomi MiMo-V2.5 is ~793% cheaper at $0.14/1M; pay for Grok 4 Fast Reasoning only for long-context analysis.
Decision scorecard
Local evidence first| Signal | Grok 4 Fast Reasoning | Xiaomi MiMo-V2.5 |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and long-context analysis | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Long context and Vision | RAG, Agents, and Long context |
| Context window | 2m | 1.05m |
| Cheapest output | $2.50/1M tokens | $0.28/1M tokens |
| Provider routes | 2 tracked | 2 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.
- Local decision data tags Grok 4 Fast Reasoning for Long context and Vision.
- Xiaomi MiMo-V2.5 has the lower cheapest tracked output price at $0.28/1M tokens.
- Xiaomi MiMo-V2.5 uniquely exposes Function calling, Tool use, and Structured outputs in local model data.
- Local decision data tags Xiaomi MiMo-V2.5 for RAG, Agents, and Long context.
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
$182
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $1,443. 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 Xiaomi MiMo-V2.5; plan for SDK, billing, or endpoint changes.
- Xiaomi MiMo-V2.5 is $2.22/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Xiaomi MiMo-V2.5 adds Function calling, Tool use, and Structured outputs in local capability data.
- No overlapping tracked provider route is sourced for Xiaomi MiMo-V2.5 and Grok 4 Fast Reasoning; plan for SDK, billing, or endpoint changes.
- Grok 4 Fast Reasoning is $2.22/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Function calling, Tool use, and Structured outputs before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-09-01 | 2026-04-22 |
| Context window | 2m | 1.05m |
| 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 |
|---|---|---|
| Input price | $1.25/1M tokens | $0.14/1M tokens |
| Output price | $2.50/1M tokens | $0.28/1M tokens |
| Providers |
Capabilities
| Capability | Grok 4 Fast Reasoning | Xiaomi MiMo-V2.5 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | No | Yes |
| Tool use | No | Yes |
| Structured outputs | No | Yes |
| 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 function calling: Xiaomi MiMo-V2.5, tool use: Xiaomi MiMo-V2.5, and structured outputs: Xiaomi MiMo-V2.5. Both models share vision, multimodal input, and 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.
For cost, Grok 4 Fast Reasoning lists $1.25/1M input and $2.50/1M output tokens on the cheapest tracked provider, while Xiaomi MiMo-V2.5 lists $0.14/1M input and $0.28/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Xiaomi MiMo-V2.5 lower by about $1.44 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.
Choose Grok 4 Fast Reasoning when long-context analysis and larger context windows are central to the workload. Choose Xiaomi MiMo-V2.5 when vision-heavy evaluation 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. It also helps separate model capability from provider packaging, which can change cost and latency.
FAQ
Which has a larger context window, Grok 4 Fast Reasoning or Xiaomi MiMo-V2.5?
Grok 4 Fast Reasoning supports 2m tokens, while Xiaomi MiMo-V2.5 supports 1.05m tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Grok 4 Fast Reasoning or Xiaomi MiMo-V2.5?
Xiaomi MiMo-V2.5 is cheaper on tracked token pricing. Grok 4 Fast Reasoning costs $1.25/1M input and $2.50/1M output tokens. Xiaomi MiMo-V2.5 costs $0.14/1M input and $0.28/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Grok 4 Fast Reasoning or Xiaomi MiMo-V2.5 open source?
Grok 4 Fast Reasoning is listed under Proprietary. Xiaomi MiMo-V2.5 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?
Both Grok 4 Fast Reasoning and Xiaomi MiMo-V2.5 expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for multimodal input, Grok 4 Fast Reasoning or Xiaomi MiMo-V2.5?
Both Grok 4 Fast Reasoning and Xiaomi MiMo-V2.5 expose multimodal input. 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 Fast Reasoning and Xiaomi MiMo-V2.5?
Grok 4 Fast Reasoning is available on Microsoft Foundry and xAI Console. Xiaomi MiMo-V2.5 is available on OpenRouter and Xiaomi. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-26. Data sourced from public model cards and provider documentation.