Claude Sonnet 4.5 vs DeepSeek V3.1

Claude Sonnet 4.5 (2025) and DeepSeek V3.1 (2025) are frontier reasoning models from Anthropic and DeepSeek. Claude Sonnet 4.5 ships a 200k-token context window, while DeepSeek V3.1 ships a 64k-token context window. On MMLU PRO, Claude Sonnet 4.5 leads by 2.7 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.

Claude Sonnet 4.5 is safer overall; choose DeepSeek V3.1 when coding workflow support matters.

Decision scorecard

Local evidence first
SignalClaude Sonnet 4.5DeepSeek V3.1
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentsmultimodal apps and provider-routed production
Decision fitCoding, RAG, and AgentsCoding, Agents, and Vision
Context window200k64k
Cheapest output$15/1M tokens$1/1M tokens
Provider routes8 tracked9 tracked
Shared benchmarksMMLU PRO leader2 shared

Decision tradeoffs

Choose Claude Sonnet 4.5 when...
  • Claude Sonnet 4.5 holds a shared-benchmark lead on MMLU PRO, ahead by 2.7 points.
  • Claude Sonnet 4.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
  • Claude Sonnet 4.5 uniquely exposes Reasoning and JSON / Tool use in local model data.
  • Local decision data tags Claude Sonnet 4.5 for Coding, RAG, and Agents.
Choose DeepSeek V3.1 when...
  • DeepSeek V3.1 has the lower cheapest tracked output price at $1/1M tokens.
  • DeepSeek V3.1 has broader tracked provider coverage for fallback and route flexibility.
  • DeepSeek V3.1 uniquely exposes Code execution in local model data.
  • Local decision data tags DeepSeek V3.1 for Coding, Agents, and Vision.

Monthly cost at traffic

Estimate token spend from the cheapest tracked input and output route or tier on this page.

Lower estimate DeepSeek V3.1

Claude Sonnet 4.5

$6,150

Cheapest tracked route/tier: Microsoft Foundry

DeepSeek V3.1

$466

Cheapest tracked route/tier: Novita AI

Estimated monthly gap: $5,684. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Sonnet 4.5 -> DeepSeek V3.1
  • Provider overlap exists on Microsoft Foundry, AWS Bedrock, and Replicate API; start route-level A/B tests there.
  • DeepSeek V3.1 is $14/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Reasoning and JSON / Tool use before moving production traffic.
  • DeepSeek V3.1 adds Code execution in local capability data.
DeepSeek V3.1 -> Claude Sonnet 4.5
  • Provider overlap exists on Microsoft Foundry, AWS Bedrock, and Replicate API; start route-level A/B tests there.
  • Claude Sonnet 4.5 is $14/1M 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 and JSON / Tool use in local capability data.

Specs

Specification
Released2025-09-292025-08-21
Context window200k64k
Parameters—671B total, 37B active (MoE)
ArchitectureDecoder OnlyMixture of Experts
LicenseProprietaryMITOSI-approved
OpennessProprietaryOpen source
WeightsNot releasedUnknown
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: permitted
Knowledge cutoff2025-12-

Pricing and availability

Pricing attributeClaude Sonnet 4.5DeepSeek V3.1
Input price
0-200,001t
$3/1M tokens
200,001t+
$6/1M tokens
$0.27/1M tokens
Output price
0-200,001t
$15/1M tokens
200,001t+
$22.50/1M tokens
$1/1M tokens
Providers
Microsoft FoundryAnthropicSnowflake CortexGCP Vertex AIAWS BedrockReplicate API
Microsoft FoundryFireworks AINVIDIA NIMTogether AIAWS BedrockReplicate API

Capabilities

CapabilityClaude Sonnet 4.5DeepSeek V3.1
VisionYesYes
MultimodalYesYes
ReasoningYesNo
JSON / Tool useYesNo
Structured outputsYesYes
Code executionNoYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkClaude Sonnet 4.5DeepSeek V3.1
MMLU PRO86.083.3
SWE-bench Verified77.266.0

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Last reviewed: 2026-10-07. Data sourced from public model cards and provider documentation.