Gemini 3.1 Pro Preview

Gemini 3.1 Pro Preview is the preview release of Google DeepMind's flagship Gemini 3.1 Pro, launched February 19, 2026 as a Transformer-based Mixture-of-Experts model tuned for deep reasoning, agentic coding and tool use. It is natively multimodal across text, image, video, audio and code, with a roughly 1M-token input context window and up to 65K output tokens, enough for entire codebases, long PDFs, or hours of audio/video in one prompt. It delivers a reported 2x-plus reasoning gain over Gemini 3 Pro and tops many tracked benchmarks, with strong instruction following and long-horizon agentic stability. Best for the most complex reasoning, synthesis and agentic engineering tasks where capability matters more than cost.

curl https://api.tunerouter.com/v1/chat/completions \
  -H "Authorization: Bearer $TUNEROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "gemini-3.1-pro-preview", "messages": [{"role": "user", "content": "Hello!"}]}'

Model ID: gemini-3.1-pro-preview · works with OpenAI SDKs — just point base_url at api.tunerouter.com