Claude Sonnet 4.5 vs Gemini 3.1 Pro Preview

Claude Sonnet 4.5 (2025) and Gemini 3.1 Pro Preview (2026) are frontier reasoning models from Anthropic and Google DeepMind. Claude Sonnet 4.5 ships a 200k-token context window, while Gemini 3.1 Pro Preview ships a 1m-token context window. On MMLU PRO, Gemini 3.1 Pro Preview leads by 5.0 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 fits 5x more tokens; pick it for long-context work and Claude Sonnet 4.5 for tighter calls.

Decision scorecard

Local evidence first
SignalClaude Sonnet 4.5Gemini 3.1 Pro Preview
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentsmultimodal apps, tool-calling agents, and long-context analysis
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window200k1m
Cheapest output$15/1M tokens$12/1M tokens
Provider routes8 tracked5 tracked
Shared benchmarks4 sharedMMLU PRO leader

Decision tradeoffs

Choose Claude Sonnet 4.5 when...
  • Claude Sonnet 4.5 has broader tracked provider coverage for fallback and route flexibility.
  • Claude Sonnet 4.5 uniquely exposes Reasoning in local model data.
  • Local decision data tags Claude Sonnet 4.5 for Coding, RAG, and Agents.
Choose Gemini 3.1 Pro Preview when...
  • Gemini 3.1 Pro Preview holds a shared-benchmark lead on MMLU PRO, ahead by 5.0 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 the lower cheapest tracked output price at $12/1M tokens.
  • Gemini 3.1 Pro Preview uniquely exposes Code execution in local model data.
  • Local decision data tags Gemini 3.1 Pro Preview 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 Gemini 3.1 Pro Preview

Claude Sonnet 4.5

$6,150

Cheapest tracked route/tier: Microsoft Foundry

Gemini 3.1 Pro Preview

$4,600

Cheapest tracked route/tier: Google AI Studio

Estimated monthly gap: $1,550. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Sonnet 4.5 -> Gemini 3.1 Pro Preview
  • Provider overlap exists on GCP Vertex AI, OpenRouter, and Replicate API; start route-level A/B tests there.
  • Gemini 3.1 Pro Preview is $3/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Reasoning before moving production traffic.
  • Gemini 3.1 Pro Preview adds Code execution in local capability data.
Gemini 3.1 Pro Preview -> Claude Sonnet 4.5
  • Provider overlap exists on GCP Vertex AI, Replicate API, and OpenRouter; start route-level A/B tests there.
  • Claude Sonnet 4.5 is $3/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Check replacement coverage for Code execution before moving production traffic.
  • Claude Sonnet 4.5 adds Reasoning in local capability data.

Specs

Specification
Released2025-09-292026-02-19
Context window200k1m
Parameters——
ArchitectureDecoder OnlyDecoder Only
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-122025-01

Pricing and availability

Pricing attributeClaude Sonnet 4.5Gemini 3.1 Pro Preview
Input price
0-200,001t
$3/1M tokens
200,001t+
$6/1M tokens
0-200,001t
$2/1M tokens
200,001t+
$4/1M tokens
Output price
0-200,001t
$15/1M tokens
200,001t+
$22.50/1M tokens
0-200,001t
$12/1M tokens
200,001t+
$18/1M tokens
Providers
Microsoft FoundryAnthropicSnowflake CortexGCP Vertex AIAWS BedrockReplicate API
Google AI StudioGCP Vertex AIOpenRouterReplicate APIVercel AI Gateway

Capabilities

CapabilityClaude Sonnet 4.5Gemini 3.1 Pro Preview
VisionYesYes
MultimodalYesYes
ReasoningYesNo
JSON / Tool useYesYes
Structured outputsYesYes
Code executionNoYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkClaude Sonnet 4.5Gemini 3.1 Pro Preview
MMLU PRO86.091.0
SWE-bench Verified77.280.6
Google-Proof Q&A83.494.3
MMMU Pro68.988.2

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Last reviewed: 2026-07-26. Data sourced from public model cards and provider documentation.