LLM Reference

Gemini 3.1 Pro Preview vs GPT-5

Gemini 3.1 Pro Preview (2026) and GPT-5 (2025) are frontier reasoning models from Google DeepMind and OpenAI. Gemini 3.1 Pro Preview ships a 1m-token context window, while GPT-5 ships a 400k-token context window. On SWE-bench Verified, Gemini 3.1 Pro Preview leads by 5.7 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.

Gemini 3.1 Pro Preview is safer overall; choose GPT-5 when coding workflow support matters.

Decision scorecard

Local evidence first
SignalGemini 3.1 Pro PreviewGPT-5
Best formultimodal apps, tool-calling agents, and long-context analysisreasoning-heavy apps, multimodal apps, and tool-calling agents
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window1m400k
Cheapest output$12/1M tokens$10/1M tokens
Provider routes5 tracked4 tracked
Shared benchmarksSWE-bench Verified leader4 shared

Decision tradeoffs

Choose Gemini 3.1 Pro Preview when...
  • Gemini 3.1 Pro Preview holds a shared-benchmark lead on SWE-bench Verified, ahead by 5.7 points.
  • Gemini 3.1 Pro Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
  • 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.
Choose GPT-5 when...
  • GPT-5 has the lower cheapest tracked output price at $10/1M tokens.
  • GPT-5 uniquely exposes Reasoning in local model data.
  • Local decision data tags GPT-5 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.

Lower estimate GPT-5

Gemini 3.1 Pro Preview

$4,600

Cheapest tracked route/tier: Google AI Studio

GPT-5

$3,500

Cheapest tracked route/tier: Replicate API

Estimated monthly gap: $1,100. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Gemini 3.1 Pro Preview -> GPT-5
  • Provider overlap exists on Replicate API, OpenRouter, and Vercel AI Gateway; start route-level A/B tests there.
  • GPT-5 is $2/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • GPT-5 adds Reasoning in local capability data.
GPT-5 -> Gemini 3.1 Pro Preview
  • Provider overlap exists on OpenRouter, Replicate API, and Vercel AI Gateway; start route-level A/B tests there.
  • Gemini 3.1 Pro Preview is $2/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Check replacement coverage for Reasoning before moving production traffic.

Specs

Specification
Released2026-02-192025-08-07
Context window1m400k
Parameters——
ArchitectureDecoder OnlyDecoder Only
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-012024-09

Pricing and availability

Pricing attributeGemini 3.1 Pro PreviewGPT-5
Input price
0-200,001t
$2/1M tokens
200,001t+
$4/1M tokens
$1.25/1M tokens
Output price
0-200,001t
$12/1M tokens
200,001t+
$18/1M tokens
$10/1M tokens
Providers
Google AI StudioGCP Vertex AIOpenRouterReplicate APIVercel AI Gateway
Replicate APIOpenRouterOpenAI APIVercel AI Gateway

Capabilities

CapabilityGemini 3.1 Pro PreviewGPT-5
VisionYesYes
MultimodalYesYes
ReasoningNoYes
JSON / Tool useYesYes
Structured outputsYesYes
Code executionYesYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkGemini 3.1 Pro PreviewGPT-5
SWE-bench Verified80.674.9
Google-Proof Q&A94.388.4
AIME 202595.094.6
MMMU Pro88.278.4

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Model pages
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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.