Phi-3 Medium 128K vs Phi-4 Mini Flash Reasoning
Phi-3 Medium 128K (2024) and Phi-4 Mini Flash Reasoning (2025) are frontier reasoning models from Microsoft Research. Phi-3 Medium 128K ships a 128k-token context window, while Phi-4 Mini Flash Reasoning ships a 128k-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.
Phi-4 Mini Flash Reasoning is safer overall; choose Phi-3 Medium 128K when provider fit matters.
Decision scorecard
Local evidence first| Signal | Phi-3 Medium 128K | Phi-4 Mini Flash Reasoning |
|---|---|---|
| Best for | provider-routed production | reasoning-heavy apps |
| Decision fit | Coding, Long context, and Classification | Long context |
| Context window | 128k | 128k |
| Cheapest output | $1.50/1M tokens | - |
| Provider routes | 2 tracked | 1 tracked |
| Shared benchmarks | 0 shared | 0 shared |
Decision tradeoffs
- Phi-3 Medium 128K has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Phi-3 Medium 128K for Coding, Long context, and Classification.
- Phi-4 Mini Flash Reasoning uniquely exposes Reasoning in local model data.
- Local decision data tags Phi-4 Mini Flash Reasoning for Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Phi-3 Medium 128K
$775
Cheapest tracked route/tier: Microsoft Foundry
Phi-4 Mini Flash Reasoning
Unavailable
No complete token price in local provider data
Cost delta unavailable until both models have sourced input and output token prices.
Switch friction
- Provider overlap exists on NVIDIA NIM; start route-level A/B tests there.
- Phi-4 Mini Flash Reasoning adds Reasoning in local capability data.
- Provider overlap exists on NVIDIA NIM; start route-level A/B tests there.
- Check replacement coverage for Reasoning before moving production traffic.
Specs
Pricing and availability
| Pricing attribute | Phi-3 Medium 128K | Phi-4 Mini Flash Reasoning |
|---|---|---|
| Input price | $0.50/1M tokens | - |
| Output price | $1.50/1M tokens | - |
| Providers |
Capabilities
| Capability | Phi-3 Medium 128K | Phi-4 Mini Flash Reasoning |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | Yes |
| 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 reasoning mode: Phi-4 Mini Flash 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.
Pricing coverage is uneven: Phi-3 Medium 128K has $0.50/1M input tokens and Phi-4 Mini Flash Reasoning 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 Phi-3 Medium 128K when provider fit and broader provider choice are central to the workload. Choose Phi-4 Mini Flash Reasoning when reasoning depth 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
Which has a larger context window, Phi-3 Medium 128K or Phi-4 Mini Flash Reasoning?
Phi-3 Medium 128K supports 128k tokens, while Phi-4 Mini Flash Reasoning supports 128k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Is Phi-3 Medium 128K or Phi-4 Mini Flash Reasoning open source?
Phi-3 Medium 128K is listed under MIT. Phi-4 Mini Flash Reasoning is listed under MIT. 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, Phi-3 Medium 128K or Phi-4 Mini Flash Reasoning?
Phi-4 Mini Flash 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 Phi-3 Medium 128K and Phi-4 Mini Flash Reasoning?
Phi-3 Medium 128K is available on Microsoft Foundry and NVIDIA NIM. Phi-4 Mini Flash Reasoning is available on NVIDIA NIM. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
When should I pick Phi-3 Medium 128K over Phi-4 Mini Flash Reasoning?
Phi-4 Mini Flash Reasoning is safer overall; choose Phi-3 Medium 128K when provider fit matters. If your workload also depends on provider fit, start with Phi-3 Medium 128K; if it depends on reasoning depth, run the same evaluation with Phi-4 Mini Flash Reasoning.
Continue comparing
Last reviewed: 2026-05-22. Data sourced from public model cards and provider documentation.