Mistral Magistral Small 2509 vs Phi 3.5 MoE Instruct
Mistral Magistral Small 2509 (2025) and Phi 3.5 MoE Instruct (2024) are compact production models from MistralAI and Microsoft Research. Mistral Magistral Small 2509 ships a not-yet-sourced context window, while Phi 3.5 MoE Instruct ships a 128k-token context window. On pricing, both list $0.50/1M input tokens on the cheapest tracked route. 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 safer overall; choose Phi 3.5 MoE Instruct when provider fit matters.
Decision scorecard
Local evidence first| Signal | Mistral Magistral Small 2509 | Phi 3.5 MoE Instruct |
|---|---|---|
| Best for | provider-routed production | general production evaluation |
| Decision fit | General | Long context |
| Context window | — | 128k |
| Cheapest output | $1.50/1M tokens | $0.50/1M tokens |
| Provider routes | 2 tracked | 1 tracked |
| Shared benchmarks | 0 shared | 0 shared |
Decision tradeoffs
- Mistral Magistral Small 2509 has broader tracked provider coverage for fallback and procurement flexibility.
- Phi 3.5 MoE Instruct has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Phi 3.5 MoE Instruct has the lower cheapest tracked output price at $0.50/1M tokens.
- Local decision data tags Phi 3.5 MoE Instruct for Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Mistral Magistral Small 2509
$775
Cheapest tracked route/tier: AWS Bedrock
Phi 3.5 MoE Instruct
$525
Cheapest tracked route/tier: Fireworks AI
Estimated monthly gap: $250. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Mistral Magistral Small 2509 and Phi 3.5 MoE Instruct; plan for SDK, billing, or endpoint changes.
- Phi 3.5 MoE Instruct is $1/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- No overlapping tracked provider route is sourced for Phi 3.5 MoE Instruct and Mistral Magistral Small 2509; plan for SDK, billing, or endpoint changes.
- Mistral Magistral Small 2509 is $1/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-09-01 | 2024-08-20 |
| Context window | — | 128k |
| Parameters | 24B | 16x3.8B (42B, 6.6B active) |
| Architecture | - | Decoder Only |
| License | Apache 2.0OSI-approved | MITOSI-approved |
| Openness | Open source | Open source |
| Commercial use | Commercial use: permitted | Commercial use: permitted |
| Knowledge cutoff | - | 2023-10 |
Pricing and availability
| Pricing attribute | Mistral Magistral Small 2509 | Phi 3.5 MoE Instruct |
|---|---|---|
| Input price | $0.50/1M tokens | $0.50/1M tokens |
| Output price | $1.50/1M tokens | $0.50/1M tokens |
| Providers |
Capabilities
| Capability | Mistral Magistral Small 2509 | Phi 3.5 MoE Instruct |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | 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 is close: both models cover the core production surface. That makes context budget, benchmark fit, and provider maturity more important than a simple checklist. If your application depends on one integration detail, verify it against the provider route you plan to use, not just the base model listing.
For cost, Mistral Magistral Small 2509 lists $0.50/1M input and $1.50/1M output tokens on the cheapest tracked provider, while Phi 3.5 MoE Instruct lists $0.50/1M input and $0.50/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Phi 3.5 MoE Instruct lower by about $0.30 per million blended tokens. Availability is 2 providers versus 1, so concentration risk also matters.
Choose Mistral Magistral Small 2509 when provider fit 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, Mistral Magistral Small 2509 or Phi 3.5 MoE Instruct?
Phi 3.5 MoE Instruct is cheaper on tracked token pricing. Mistral Magistral Small 2509 costs $0.50/1M input and $1.50/1M output tokens. Phi 3.5 MoE Instruct costs $0.50/1M input and $0.50/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Mistral Magistral Small 2509 or Phi 3.5 MoE Instruct open source?
Mistral Magistral Small 2509 is listed under Apache 2.0. 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.
Where can I run Mistral Magistral Small 2509 and Phi 3.5 MoE Instruct?
Mistral Magistral Small 2509 is available on AWS Bedrock and Vercel AI Gateway. Phi 3.5 MoE Instruct is available on Fireworks AI. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
When should I pick Mistral Magistral Small 2509 over Phi 3.5 MoE Instruct?
Mistral Magistral Small 2509 is safer overall; choose Phi 3.5 MoE Instruct when provider fit matters. If your workload also depends on provider fit, start with Mistral Magistral Small 2509; if it depends on provider fit, run the same evaluation with Phi 3.5 MoE Instruct.
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Last reviewed: 2026-06-15. Data sourced from public model cards and provider documentation.