Gemini 3.1 Pro Review 2026: Benchmarks, Pricing & What Changed
Google released Gemini 3.1 Pro in preview on February 19, 2026, reporting a lead on 13 of 16 major benchmarks against competing frontier models. Here's what changed, what it costs, and how it stacks up against GPT-5.5 and Claude Opus 4.8.
Reviewed 2026-07-13 · Source: Google Gemini API pricing
Quick Verdict
Gemini 3.1 Pro is the cheapest of the current flagship models per token while leading the most benchmarks outright — a reported highest-ever GPQA Diamond score of 94.3%, plus strong agentic-coding results on SWE-bench Verified and Terminal-Bench 2.0. At $2.00/$12.00 per million input/output tokens (under 200K context) it undercuts both GPT-5.5 and Claude Opus 4.8, making it the default pick for teams optimizing for benchmark breadth and cost rather than a specific occupation-focused eval suite.
What's New in Gemini 3.1 Pro
Leads 13 of 16 major benchmarks
Google positions Gemini 3.1 Pro as its most capable model to date, topping 13 of 16 widely-tracked benchmarks against competing frontier models — including a reported highest-ever score on GPQA Diamond (94.3%).
1 million token context window
Gemini 3.1 Pro accepts up to 1 million input tokens, with a maximum output of 64,000 tokens — enough for large codebases, long research documents, or entire book manuscripts in a single request.
Strong agentic and terminal coding scores
Beyond chat benchmarks, Gemini 3.1 Pro scores 80.6% on SWE-bench Verified and 68.5% on Terminal-Bench 2.0, signaling a deliberate push into autonomous coding-agent territory rather than just conversational quality.
Still labeled 'preview' as of mid-2026
As of this review, Gemini 3.1 Pro has not received a general-availability label — it remains a preview model in the Gemini API, even as Google has already teased a Gemini 3.5 Pro successor for later in 2026.
Benchmark Scores
Google reports Gemini 3.1 Pro leads 13 of 16 major benchmarks tracked against competing frontier models.
| Benchmark | Gemini 3.1 Pro |
|---|---|
| GPQA Diamond (graduate-level science) | 94.3% |
| ARC-AGI-2 (novel reasoning) | 77.1% |
| SWE-bench Verified (real-world coding) | 80.6% |
| Humanity's Last Exam | 44.4% |
| BrowseComp (autonomous research) | 85.9% |
| Terminal-Bench 2.0 (agentic coding) | 68.5% |
Gemini 3.1 Pro Pricing
API pricing per million tokens, verified against Google's current Gemini API pricing page.
Input: $2.00 / million tokens
Output: $12.00 / million tokens
Standard pricing for prompts up to 200,000 tokens of context.
Input: $4.00 / million tokens
Output: $18.00 / million tokens
Long-context pricing kicks in beyond 200K tokens, up to the 1M token window.
Input: $1.25 / million tokens
Output: $10.00 / million tokens
Still available for cost-sensitive workloads that don't need the 3.1 Pro benchmark gains.
API model ID: gemini-3.1-pro-preview. Available via Google AI Studio.
Who Should Use Gemini 3.1 Pro?
Use it now if you're running:
- ✓ Cost-sensitive workloads that still need frontier-level benchmark results
- ✓ Autonomous research or browsing agents (BrowseComp-heavy tasks)
- ✓ Agentic coding workflows needing strong SWE-bench and terminal-task performance
- ✓ Long-document or large-codebase tasks needing the 1M token context window
Consider alternatives if:
- → You need a generally-available (non-preview) model with a stability SLA
- → Your workload is occupation-specific knowledge work — GPT-5.5's GDPval-style evals may match your use case better
- → Your prompts regularly exceed 200K tokens — long-context pricing roughly doubles the per-token cost
Frequently Asked Questions
What is Gemini 3.1 Pro?
Gemini 3.1 Pro is Google's flagship large language model, released in preview on February 19, 2026. It leads 13 of 16 major benchmarks tracked against competing frontier models, including a reported highest-ever score of 94.3% on GPQA Diamond, and ships with a 1 million token context window.
How much does Gemini 3.1 Pro cost via the API?
For prompts up to 200,000 tokens of context, Gemini 3.1 Pro costs $2.00 per million input tokens and $12.00 per million output tokens. Beyond 200K tokens (up to the 1M token limit), pricing rises to $4.00 per million input tokens and $18.00 per million output tokens. That's roughly 60% more than the previous-generation Gemini 2.5 Pro ($1.25/$10.00 per million tokens).
What are Gemini 3.1 Pro's benchmark scores?
Gemini 3.1 Pro scores 94.3% on GPQA Diamond, 77.1% on ARC-AGI-2, 80.6% on SWE-bench Verified, 85.9% on BrowseComp, 68.5% on Terminal-Bench 2.0, and 44.4% on Humanity's Last Exam. Google reports it leads 13 of 16 major benchmarks against competing frontier models at time of release.
Is Gemini 3.1 Pro generally available?
No — as of this review, Gemini 3.1 Pro remains labeled 'preview' in the Gemini API rather than generally available, despite being in preview since February 2026. Google has already previewed a Gemini 3.5 Pro successor for later in 2026, but as of writing it is not yet listed as a shipping model ID.
How does Gemini 3.1 Pro compare to GPT-5.5 and Claude Opus 4.8?
All three are 2026-generation flagship models with 1M token context windows. Gemini 3.1 Pro is the cheapest of the three at $2.00/$12.00 per million tokens (vs. GPT-5.5's $5/$30 and Claude Opus 4.8's $5/$25) while leading more raw benchmarks, including the highest reported GPQA Diamond score. GPT-5.5 leans into occupation-specific knowledge-work evals, and Claude Opus 4.8 emphasizes agentic coding honesty in Claude Code — Gemini 3.1 Pro's edge is benchmark breadth plus lower cost per token.
What's the context window for Gemini 3.1 Pro?
Gemini 3.1 Pro accepts up to 1 million input tokens and generates a maximum of 64,000 output tokens per request, making it suitable for large codebases, long documents, and multi-file agentic workflows without chunking.
Try Gemini 3.1 Pro
Available today in preview via Google AI Studio and the Gemini API.
Try Google AI Studio →API developers: model ID is gemini-3.1-pro-preview
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