Gemini 3.1 Pro Preview vs GPT-5.5 Pro
Gemini 3.1 Pro Preview (2026) and GPT-5.5 Pro (2026) are frontier reasoning models from Google DeepMind and OpenAI. Gemini 3.1 Pro Preview ships a 1m-token context window, while GPT-5.5 Pro ships a 1.05m-token context window. On SWE-bench Verified, GPT-5.5 Pro leads by 2 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
GPT-5.5 Pro is safer overall; choose Gemini 3.1 Pro Preview when coding workflow support matters.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Pro Preview | GPT-5.5 Pro |
|---|---|---|
| Best for | multimodal apps, tool-calling agents, and long-context analysis | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1m | 1.05m |
| Cheapest output | $12/1M tokens | $180/1M tokens |
| Provider routes | 5 tracked | 3 tracked |
| Shared benchmarks | 5 shared | SWE-bench Verified leader |
Decision tradeoffs
- Gemini 3.1 Pro Preview holds a shared-benchmark lead on Google-Proof Q&A, ahead by 0.7 points.
- Gemini 3.1 Pro Preview has the lower cheapest tracked output price at $12/1M tokens.
- Gemini 3.1 Pro Preview has broader tracked provider coverage for fallback and route flexibility.
- Local decision data tags Gemini 3.1 Pro Preview for Coding, RAG, and Agents.
- GPT-5.5 Pro holds a shared-benchmark lead on SWE-bench Verified, ahead by 2 points.
- GPT-5.5 Pro has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 Pro uniquely exposes Reasoning in local model data.
- Local decision data tags GPT-5.5 Pro 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.
Gemini 3.1 Pro Preview
$4,600
Cheapest tracked route/tier: Google AI Studio
GPT-5.5 Pro
$69,000
Cheapest tracked route/tier: OpenAI API <=272K tokens (standard)
Estimated monthly gap: $64,400. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- GPT-5.5 Pro is $168/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.5 Pro adds Reasoning in local capability data.
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- Gemini 3.1 Pro Preview is $168/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-02-19 | 2026-04-23 |
| Context window | 1m | 1.05m |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2025-01 | 2025-12 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Pro Preview | GPT-5.5 Pro |
|---|---|---|
| Input price |
| $30/1M tokens |
| Output price |
| $180/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Pro Preview | GPT-5.5 Pro |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | Yes |
| JSON / Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.5 Pro |
|---|---|---|
| SWE-bench Verified | 80.6 | 82.6 |
| SWE-bench Pro | 54.2 | 58.6 |
| Google-Proof Q&A | 94.3 | 93.6 |
| LiveCodeBench | 91.7 | 91.0 |
| MCP-Atlas | 69.2 | 75.3 |
Continue comparing
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- GPT-5.5 Pro vs Grok 4
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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.