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Head-to-head comparison

Gemini 3.1 Pro Preview vs GPT-5.6 Terra

Gemini 3.1 Pro Preview (Google) and GPT-5.6 Terra (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 22 September 2026

As of 22 September 2026, Gemini 3.1 Pro Preview holds the stronger ModelCap Index position (#17 vs #21).

Which should you choose?

Choose Gemini 3.1 Pro Preview if…

  • you want the stronger overall ModelCap Index position — #17 against #21 (81.5 vs 79.7 points).
  • Arena coding is your yardstick — 1520 against 1518.
  • AA τ²-Bench Telecom is your yardstick — 95.6% against 86.3%.
  • AA Humanity's Last Exam is your yardstick — 47.0% against 42.9%.

Choose GPT-5.6 Terra if…

  • you want provider choice — 3 listed API providers against 2.
  • LMArena Agent is your yardstick — 1.4% against -5.8%.
  • AA Intelligence Index is your yardstick — 42.1 against 29.7.
  • you want the more recently listed model — GPT-5.6 Terra was listed 9 July 2026, Gemini 3.1 Pro Preview 19 February 2026.

Gemini 3.1 Pro Preview vs GPT-5.6 Terra: specs, pricing and context

Specification comparison of Gemini 3.1 Pro Preview and GPT-5.6 Terra
FieldGemini 3.1 Pro PreviewGoogleGPT-5.6 TerraOpenAI
ModelCap Index position#17#21
Index score81.579.7
EvidenceMeasuredMeasured
Input price / 1M tokens$2.00$2.00
Output price / 1M tokens$12.00$12.00
Context window1M tokens1M tokens
Max output tokens66K128K
API providers listed23
Weight accessAPI onlyAPI only
Input modalitiesAudio, File, Image, Text, VideoFile, Image, Text
First listed19 February 20269 July 2026
PublisherGoogleOpenAI

Evidence: 4 public benchmark observations across 4 boards · 6 public benchmark observations across 6 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Gemini 3.1 Pro Preview vs GPT-5.6 Terra

Public benchmark boards where Gemini 3.1 Pro Preview or GPT-5.6 Terra has a published result
BoardGemini 3.1 Pro PreviewGPT-5.6 TerraLeads
Arena codingArena (LMArena)15201515–152515181510–1525X-HighGemini 3.1 Pro Preview
LMArena AgentLMArena-5.8%-6.6%–-5.0%1.4%0.3%–2.6%X-HighGPT-5.6 Terra
ARC-AGI-2ARC Prize Foundation—83.9%MaxOnly one result
ARC-AGI-3ARC Prize Foundation—0.8%MaxOnly one result
AA Intelligence IndexArtificial Analysis29.7intelligence-index:v4.3:reasoning-unspecified42.1intelligence-index:v4.3:maxGPT-5.6 Terra
AA τ²-Bench TelecomArtificial Analysis95.6%tau2:telecom:dual-control:pass-at-1:3-repeats:source-model="Gemini 3.1 Pro Preview":reasoning=true86.3%tau2:telecom:dual-control:pass-at-1:3-repeats:source-model="GPT-5.6 Terra (max)":reasoning=trueGemini 3.1 Pro Preview
AA Humanity's Last ExamArtificial Analysis47.0%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="Gemini 3.1 Pro Preview":reasoning=true42.9%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="GPT-5.6 Terra (max)":reasoning=trueGemini 3.1 Pro Preview
Terminal-Bench 4.0Terminal-Bench (Laude Institute)—21.5%18.3%–24.8%Codex · MaxOnly one result

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Gemini 3.1 Pro Preview vs GPT-5.6 Terra: common questions

Is Gemini 3.1 Pro Preview better than GPT-5.6 Terra?

Gemini 3.1 Pro Preview ranks higher on the ModelCap Index as of 22 September 2026: #17 against #21. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.

Is Gemini 3.1 Pro Preview cheaper than GPT-5.6 Terra?

Both list the same output price, $12.00/1M tokens, with input at $2.00/1M and $2.00/1M respectively. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $10.00 for Gemini 3.1 Pro Preview versus $10.00 for GPT-5.6 Terra. The listed-rate totals are equal. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.

Which has the bigger context window, Gemini 3.1 Pro Preview or GPT-5.6 Terra?

Both publish a 1M-token context window.

Which is better for coding, Gemini 3.1 Pro Preview or GPT-5.6 Terra?

Arena coding: Gemini 3.1 Pro Preview 1520, GPT-5.6 Terra 1518 — Gemini 3.1 Pro Preview leads.

Are Gemini 3.1 Pro Preview and GPT-5.6 Terra open-weight models?

Gemini 3.1 Pro Preview: API only. GPT-5.6 Terra: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run Gemini 3.1 Pro Preview and GPT-5.6 Terra?

ModelCap currently lists 2 API providers for Gemini 3.1 Pro Preview and 3 for GPT-5.6 Terra, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Gemini 3.1 Pro Preview vs GPT-5.6 Terra comparison?

Every figure comes from the sealed ModelCap dataset published 22 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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