GPT-5.5 Instant vs Mistral Large 3 675B Instruct
GPT-5.5 Instant (2026) and Mistral Large 3 675B Instruct (2025) are compact production models from OpenAI and MistralAI. GPT-5.5 Instant ships a 400K-token context window, while Mistral Large 3 675B Instruct ships a 128K-token context window. On LMArena Vision Arena, GPT-5.5 Instant leads by 77 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Mistral Large 3 675B Instruct is ~900% cheaper at $0.50/1M; pay for GPT-5.5 Instant only for coding workflow support.
Decision scorecard
Local evidence first| Signal | GPT-5.5 Instant | Mistral Large 3 675B Instruct |
|---|---|---|
| Best for | multimodal apps and tool-calling agents | multimodal apps and provider-routed production |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 400K | 128K |
| Cheapest output | $30/1M tokens | $1.50/1M tokens |
| Provider routes | 1 tracked | 6 tracked |
| Shared benchmarks | LMArena Vision Arena leader | 2 shared |
Decision tradeoffs
- GPT-5.5 Instant holds a shared-benchmark lead on LMArena Vision Arena, ahead by 77 points.
- GPT-5.5 Instant has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 Instant uniquely exposes JSON / Tool use and Code execution in local model data.
- Local decision data tags GPT-5.5 Instant for Coding, RAG, and Agents.
- Mistral Large 3 675B Instruct has the lower cheapest tracked output price at $1.50/1M tokens.
- Mistral Large 3 675B Instruct has broader tracked provider coverage for fallback and route flexibility.
- Local decision data tags Mistral Large 3 675B Instruct for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GPT-5.5 Instant
$11,500
Cheapest tracked route/tier: OpenAI API
Mistral Large 3 675B Instruct
$775
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $10,725. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for GPT-5.5 Instant and Mistral Large 3 675B Instruct; plan for SDK, billing, or endpoint changes.
- Mistral Large 3 675B Instruct is $28.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for JSON / Tool use and Code execution before moving production traffic.
- No overlapping tracked provider route is sourced for Mistral Large 3 675B Instruct and GPT-5.5 Instant; plan for SDK, billing, or endpoint changes.
- GPT-5.5 Instant is $28.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.5 Instant adds JSON / Tool use and Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-05 | 2025-12-01 |
| Context window | 400K | 128K |
| Parameters | — | 675B |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Apache 2.0OSI-approved |
| Openness | Proprietary | Open source |
| Weights | Not released | Unknown |
| Code | Unknown | Unknown |
| Commercial use | Restricted | Permitted |
| Knowledge cutoff | 2025-08 | 2024-11 |
Pricing and availability
| Pricing attribute | GPT-5.5 Instant | Mistral Large 3 675B Instruct |
|---|---|---|
| Input price | $5/1M tokens | $0.50/1M tokens |
| Output price | $30/1M tokens | $1.50/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.5 Instant | Mistral Large 3 675B Instruct |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | No |
| JSON / Tool use | Yes | No |
| Structured outputs | Yes | Yes |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | GPT-5.5 Instant | Mistral Large 3 675B Instruct |
|---|---|---|
| LMArena Vision Arena | 1276.0 | 1199.0 |
| LMArena Text Arena - Creative Writing | 1418.0 | 1387.0 |
Deep dive
On shared benchmark coverage, LMArena Vision Arena has GPT-5.5 Instant at 1276 and Mistral Large 3 675B Instruct at 1199, with GPT-5.5 Instant ahead by 77 points; LMArena Text Arena - Creative Writing has GPT-5.5 Instant at 1418 and Mistral Large 3 675B Instruct at 1387, with GPT-5.5 Instant ahead by 31 points. The largest visible gap is 77 points on LMArena Vision Arena, 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 JSON / Tool use: GPT-5.5 Instant, JSON / Tool use: GPT-5.5 Instant, and code execution: GPT-5.5 Instant. Both models share vision, multimodal input, and structured outputs, 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 Instant lists $5/1M input and $30/1M output tokens on the cheapest listed provider, while Mistral Large 3 675B Instruct lists $0.50/1M input and $1.50/1M output tokens on the cheapest listed provider. A 70/30 input-output blend puts Mistral Large 3 675B Instruct lower by about $11.70 per million blended tokens. Availability is 1 providers versus 6, so concentration risk also matters.
Choose GPT-5.5 Instant when coding workflow support and larger context windows are central to the workload. Choose Mistral Large 3 675B Instruct when vision-heavy evaluation, lower input-token cost, and broader provider choice 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 Instant or Mistral Large 3 675B Instruct?
GPT-5.5 Instant supports 400K tokens, while Mistral Large 3 675B 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 Instant or Mistral Large 3 675B Instruct?
Mistral Large 3 675B Instruct is cheaper on listed token pricing. GPT-5.5 Instant costs $5/1M input and $30/1M output tokens. Mistral Large 3 675B Instruct costs $0.50/1M input and $1.50/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is GPT-5.5 Instant or Mistral Large 3 675B Instruct open source?
GPT-5.5 Instant is listed under Proprietary. Mistral Large 3 675B Instruct is listed under Apache 2.0. 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 Instant or Mistral Large 3 675B Instruct?
Both GPT-5.5 Instant and Mistral Large 3 675B Instruct expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for multimodal input, GPT-5.5 Instant or Mistral Large 3 675B Instruct?
Both GPT-5.5 Instant and Mistral Large 3 675B Instruct expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Where can I run GPT-5.5 Instant and Mistral Large 3 675B Instruct?
GPT-5.5 Instant is available on OpenAI API. Mistral Large 3 675B Instruct is available on OpenRouter, AWS Bedrock, NVIDIA NIM, Mistral AI Studio, and Microsoft Foundry. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-10-07. Data sourced from public model cards and provider documentation.