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Official commercial channel

Gemini 3.1 Pro API

Google’s current reasoning flagship: a 1M window, priced in tiers by request length.

  • Context

    1M

  • Max output

    64K

  • Serving precision

    Vendor-managed

  • Licence

    Proprietary

Gemini 3.1 Pro is Google’s current tier for flagship reasoning, with a 1-million-token context window, roughly 64K maximum output and text plus image input. Pricing steps with context length: $2 per million input and $12 per million output up to 200K, rising to $4 and $18 above that. We provide access through an official commercial channel — no account pools, no reverse-engineered client protocols.

Proprietary, provided through the vendor’s official commercial licensing. Contract, invoice, audit trail — not an account pool and not a reverse-engineered client protocol.

Specifications

Model ID
gemini-3.1-pro
Published by
Google
How it is served
Official commercial channel
Licence
Proprietary
Context
1M
Max output
64K
Serving precision
Vendor-managed
Input modalities
Text · Image
Released
2026-02-19

What it is good at

Competitive on short requests
Below 200K tokens the rate is $2 input and $12 output per million. The overwhelming majority of production requests land in that band, so real invoices tend to come in well under a top-tier estimate.
A million-token window with image input
Long documents and images in the same request, which suits analysis over material full of charts and scans.
The other pole of the ecosystem
Part of the value of carrying Gemini is lateral comparison: run the same prompts against Claude, GPT and the open flagships on one key and the capability-versus-cost differences surface immediately.

Where it fits

  • Analysis of long material containing charts and scans
  • Cost-sensitive pipelines whose requests mostly stay under 200K tokens
  • Cross-vendor comparison and supplier redundancy
  • Workloads that need consistency with the Google ecosystem

Three steps

Change one line of base_url, put the model ID below in the `model` field, and leave the rest of your code alone.

model: "gemini-3.1-pro"

curl https://api.nexaix.net/v1/chat/completions \
  -H "Authorization: Bearer $NEXAIX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3.1-pro",
    "stream": true,
    "messages": [
      { "role": "user", "content": "Summarise this contract." }
    ]
  }'

About this model

How exactly does the pricing tier work?

It steps by the context length of the request: below 200K tokens you pay the lower rate, above it the whole request moves to the higher one. Estimate from your real input-length distribution rather than an average.

Why is there no Gemini 3.5 Pro?

Because it does not exist. Google’s Pro tier this generation is 3.1 Pro; 3.5 and 3.6 are Flash models — the faster, cheaper speed tier. Anyone marketing a "Gemini 3.5 Pro" is working from an unreliable source.

Do you log conversations?

No. Nothing is written to disk on our side; we keep only the request ID, token counts, timestamp and status code needed for billing and debugging. The upstream vendor’s data handling is governed by their own terms.

Also worth a look

Run your own eval on it

Take the trial credit, run the evals you already have against this model, and then decide whether it gets your production traffic.