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 pricing, Mistral Large 3 675B Instruct costs $0.50/1M input tokens versus $5/1M for the alternative. 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 | 0 shared | 0 shared |
Decision tradeoffs
- 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 | Commercial use: conditional | Commercial use: 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
No shared benchmark scores are currently available for this pair.
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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.