GPT-5.5 vs Mistral Medium 3 Instruct
GPT-5.5 (2026) and Mistral Medium 3 Instruct (2025) are frontier reasoning models from OpenAI and MistralAI. GPT-5.5 ships a 1.1M-token context window, while Mistral Medium 3 Instruct ships a 128K-token context window. On pricing, Mistral Medium 3 Instruct costs $0.4/1M input tokens versus $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.
Mistral Medium 3 Instruct is ~1150% cheaper at $0.4/1M; pay for GPT-5.5 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | GPT-5.5 | Mistral Medium 3 Instruct |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Long context |
| Context window | 1.1M | 128K |
| Cheapest output | $30/1M tokens | $2/1M tokens |
| Provider routes | 2 tracked | 2 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 uniquely exposes Vision, Multimodal, and Reasoning in local model data.
- Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
- Mistral Medium 3 Instruct has the lower cheapest tracked output price at $2/1M tokens.
- Local decision data tags Mistral Medium 3 Instruct for Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
GPT-5.5
$11,500
Cheapest tracked route: OpenAI API
Mistral Medium 3 Instruct
$820
Cheapest tracked route: Mistral AI Studio
Estimated monthly gap: $10,680. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for GPT-5.5 and Mistral Medium 3 Instruct; plan for SDK, billing, or endpoint changes.
- Mistral Medium 3 Instruct is $28/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Vision, Multimodal, and Reasoning before moving production traffic.
- No overlapping tracked provider route is sourced for Mistral Medium 3 Instruct and GPT-5.5; plan for SDK, billing, or endpoint changes.
- GPT-5.5 is $28/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.5 adds Vision, Multimodal, and Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-23 | 2025-10-01 |
| Context window | 1.1M | 128K |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | 1 |
| Knowledge cutoff | 2025-12 | - |
Pricing and availability
| Pricing attribute | GPT-5.5 | Mistral Medium 3 Instruct |
|---|---|---|
| Input price | $5/1M tokens | $0.4/1M tokens |
| Output price | $30/1M tokens | $2/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.5 | Mistral Medium 3 Instruct |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| Reasoning | Yes | No |
| Function calling | Yes | No |
| Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | Yes | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on vision: GPT-5.5, multimodal input: GPT-5.5, reasoning mode: GPT-5.5, function calling: GPT-5.5, tool use: GPT-5.5, structured outputs: GPT-5.5, and code execution: GPT-5.5. 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, GPT-5.5 lists $5/1M input and $30/1M output tokens, while Mistral Medium 3 Instruct lists $0.4/1M input and $2/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Mistral Medium 3 Instruct lower by about $11.62 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.
Choose GPT-5.5 when coding workflow support and larger context windows are central to the workload. Choose Mistral Medium 3 Instruct when provider fit 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.
FAQ
Which has a larger context window, GPT-5.5 or Mistral Medium 3 Instruct?
GPT-5.5 supports 1.1M tokens, while Mistral Medium 3 Instruct supports 128K tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, GPT-5.5 or Mistral Medium 3 Instruct?
Mistral Medium 3 Instruct is cheaper on tracked token pricing. GPT-5.5 costs $5/1M input and $30/1M output tokens. Mistral Medium 3 Instruct costs $0.4/1M input and $2/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is GPT-5.5 or Mistral Medium 3 Instruct open source?
GPT-5.5 is listed under Proprietary. Mistral Medium 3 Instruct is listed under 1. 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, GPT-5.5 or Mistral Medium 3 Instruct?
GPT-5.5 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, GPT-5.5 or Mistral Medium 3 Instruct?
GPT-5.5 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.
Where can I run GPT-5.5 and Mistral Medium 3 Instruct?
GPT-5.5 is available on OpenAI API and OpenRouter. Mistral Medium 3 Instruct is available on NVIDIA NIM and Mistral AI Studio. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-05-11. Data sourced from public model cards and provider documentation.