o4-mini vs Phi 3.5 MoE Instruct
o4-mini (2025) and Phi 3.5 MoE Instruct (2024) are frontier reasoning models from OpenAI and Microsoft Research. o4-mini ships a not-yet-sourced context window, while Phi 3.5 MoE Instruct ships a 128K-token context window. On pricing, o4-mini costs $0.5/1M input tokens versus $0.5/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
o4-mini is safer overall; choose Phi 3.5 MoE Instruct when provider fit matters.
Specs
| Released | 2025-04-16 | 2024-08-20 |
| Context window | — | 128K |
| Parameters | — | 16x3.8B (42B, 6.6B active) |
| Architecture | decoder only | decoder only |
| License | Proprietary | MIT |
| Knowledge cutoff | 2025-08 | - |
Pricing and availability
| o4-mini | Phi 3.5 MoE Instruct | |
|---|---|---|
| Input price | $0.5/1M tokens | $0.5/1M tokens |
| Output price | $2/1M tokens | $0.5/1M tokens |
| Providers |
Capabilities
| o4-mini | Phi 3.5 MoE Instruct | |
|---|---|---|
| Vision | ||
| Multimodal | ||
| Reasoning | ||
| Function calling | ||
| Tool use | ||
| Structured outputs | ||
| Code execution |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on vision: o4-mini, multimodal input: o4-mini, reasoning mode: o4-mini, function calling: o4-mini, tool use: o4-mini, structured outputs: o4-mini, and code execution: o4-mini. 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, o4-mini lists $0.5/1M input and $2/1M output tokens, while Phi 3.5 MoE Instruct lists $0.5/1M input and $0.5/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Phi 3.5 MoE Instruct lower by about $0.45 per million blended tokens. Availability is 4 providers versus 1, so concentration risk also matters.
Choose o4-mini when coding workflow support and broader provider choice are central to the workload. Choose Phi 3.5 MoE Instruct 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 is cheaper, o4-mini or Phi 3.5 MoE Instruct?
o4-mini is cheaper on tracked token pricing. o4-mini costs $0.5/1M input and $2/1M output tokens. Phi 3.5 MoE Instruct costs $0.5/1M input and $0.5/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is o4-mini or Phi 3.5 MoE Instruct open source?
o4-mini is listed under Proprietary. Phi 3.5 MoE Instruct 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 vision, o4-mini or Phi 3.5 MoE Instruct?
o4-mini 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, o4-mini or Phi 3.5 MoE Instruct?
o4-mini 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, o4-mini or Phi 3.5 MoE Instruct?
o4-mini 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 o4-mini and Phi 3.5 MoE Instruct?
o4-mini is available on OpenAI API, OpenRouter, OpenAI Batch API, and Replicate API. Phi 3.5 MoE Instruct is available on Fireworks AI. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-04-24. Data sourced from public model cards and provider documentation.