GPT-5.5 vs Mistral Medium 3.5
GPT-5.5 (2026) and Mistral Medium 3.5 (2026) are frontier-tier reasoning models from OpenAI and MistralAI. GPT-5.5 ships a 1.1M-token context window, while Mistral Medium 3.5 ships a 256K-token context window. On SWE-bench Verified, GPT-5.5 leads by 11.1 pts. On pricing, Mistral Medium 3.5 costs $1.5/1M input tokens versus $5/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Mistral Medium 3.5 is ~233% cheaper at $1.5/1M; pay for GPT-5.5 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | GPT-5.5 | Mistral Medium 3.5 |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1.1M | 256K |
| Cheapest output | $30/1M tokens | $7.5/1M tokens |
| Provider routes | 2 tracked | 2 tracked |
| Shared benchmarks | SWE-bench Verified leader | 1 rows |
Decision tradeoffs
- GPT-5.5 leads the largest shared benchmark signal on SWE-bench Verified by 11.1 points.
- GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 uniquely exposes Code execution in local model data.
- Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
- Mistral Medium 3.5 has the lower cheapest tracked output price at $7.5/1M tokens.
- Local decision data tags Mistral Medium 3.5 for Coding, RAG, and Agents.
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 3.5
$3,075
Cheapest tracked route: Mistral AI Studio
Estimated monthly gap: $8,425. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Mistral Medium 3.5 is $22.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Code execution before moving production traffic.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- GPT-5.5 is $22.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.5 adds Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-23 | 2026-04-29 |
| Context window | 1.1M | 256K |
| Parameters | — | 128B |
| Architecture | decoder only | decoder only |
| License | Proprietary | Mistral License |
| Knowledge cutoff | 2025-12 | - |
Pricing and availability
| Pricing attribute | GPT-5.5 | Mistral Medium 3.5 |
|---|---|---|
| Input price | $5/1M tokens | $1.5/1M tokens |
| Output price | $30/1M tokens | $7.5/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.5 | Mistral Medium 3.5 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | No |
Benchmarks
| Benchmark | GPT-5.5 | Mistral Medium 3.5 |
|---|---|---|
| SWE-bench Verified | 88.7 | 77.6 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has GPT-5.5 at 88.7 and Mistral Medium 3.5 at 77.6, with GPT-5.5 ahead by 11.1 points. The largest visible gap is 11.1 points on SWE-bench Verified, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on code execution: GPT-5.5. Both models share vision, multimodal input, reasoning mode, and function calling, 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 3.5 lists $1.5/1M input and $7.5/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Mistral Medium 3.5 lower by about $9.2 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 3.5 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.
FAQ
Which has a larger context window, GPT-5.5 or Mistral Medium 3.5?
GPT-5.5 supports 1.1M tokens, while Mistral Medium 3.5 supports 256K 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 3.5?
Mistral Medium 3.5 is cheaper on tracked token pricing. GPT-5.5 costs $5/1M input and $30/1M output tokens. Mistral Medium 3.5 costs $1.5/1M input and $7.5/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is GPT-5.5 or Mistral Medium 3.5 open source?
GPT-5.5 is listed under Proprietary. Mistral Medium 3.5 is listed under Mistral License. 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 3.5?
Both GPT-5.5 and Mistral Medium 3.5 expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. 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 3.5?
Both GPT-5.5 and Mistral Medium 3.5 expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Where can I run GPT-5.5 and Mistral Medium 3.5?
GPT-5.5 is available on OpenAI API and OpenRouter. Mistral Medium 3.5 is available on Mistral AI Studio and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-14. Data sourced from public model cards and provider documentation.